1. The document describes measuring and analyzing the radiation patterns of a dual-polarized meteorological radar antenna that was upgraded from single to dual polarization.
2. A Fresnel-zone holographic technique was used to measure the antenna's co-polarized and cross-polarized radiation patterns. The sidelobes were found to be higher than predicted.
3. Analysis of the aperture field data identified surface errors in the reflector dish and shadowing from the feed crook as contributing to the elevated sidelobes. Both theoretical modeling and manipulation of the measured data supported this finding.
Multi-Resolution Analysis: MRA Based Bright Band Height Estimation with Preci...Waqas Tariq
A method for reconstruction of cross section of rainfall situations with precipitation radar data based on wavelet analysis of Multi-Resolution Analysis (MRA) which allows extract a peak of the radar reflectivity is proposed in order to detect bright band height. It is found that the bright band height can be estimated by using the MRA with the basis of Daubechies wavelet family. It is also found that the boundaries in rainfall structure can be clearly extracted with MRA.
Probing the Detailed Physics of Hot Baryons with Lynx: Predictions from Mock ...John ZuHone
The document discusses how the Lynx X-ray observatory's high angular resolution, large effective area, and high spectral resolution would allow for detailed studies of the physics of hot baryons in galaxy clusters and galaxies. Mock observations using simulation tools show Lynx could map gas structures at small scales, detect pressure discontinuities like shocks, and observe velocity fields with higher precision than current instruments. The capabilities would provide new insights into gas properties in clusters and halos of galaxies.
Radiation Q bounds for small electric dipoles over a conducting ground planeYong Heui Cho
This document discusses theoretical bounds on the quality factor (Q) of small electric dipole antennas placed over a conducting ground plane. It finds that for vertically polarized dipoles, the Q can decrease by approximately a factor of two compared to an antenna of the same size in free space, indicating a doubling of bandwidth. This bandwidth enhancement is validated through simulations and measurements of small spherical helix dipole antennas over a ground plane. For horizontally polarized dipoles, the Q increases significantly compared to free space as the ground separation decreases. The analysis divides space into regions and uses vector spherical wave functions to calculate stored electric and magnetic energies, from which Q is determined following definitions by Chu and Thal.
The document describes a new algorithm for correcting the bidirectional reflectance distribution function (BRDF) of remote sensing reflectance measurements in coastal waters. Through radiative transfer simulations for a wide range of conditions, the authors developed a model relating remote sensing reflectance to the inherent optical properties of coastal waters. The new BRDF correction algorithm was shown to reduce uncertainty to below 1% when applied to both in situ and satellite ocean color data, improving on an existing open ocean algorithm. Its application significantly improved the match between in situ and MODIS satellite measurements of coastal waters.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Instrument to measure the bidirectional reflectanceajsatienza
This instrument measures the bidirectional reflectance distribution function (BRDF) of surfaces with the following properties:
1. It measures the BRDF for eight illumination angles from 0 to 65 degrees, three colors (475, 570, 658 nm), and over 100 selected viewing angles.
2. The viewing zenith angles range from 5 to 65 degrees, and the azimuth angles range from 0 to ±180 degrees relative to the illumination direction.
3. Tests show it can measure the BRDF of flat surfaces with a precision of 1-5% and an accuracy of 10% of the measured reflectance.
The document discusses image distortion effects in subsurface synthetic aperture radar (SAR) imaging of deserts and proposes an iterative corrective approach. It summarizes that subsurface SAR can map subsurface topography under sand but images are distorted due to geometric distortion and defocusing. It then proposes using dual-frequency SAR, with VHF penetrating sand and Ka imaging the surface, along with an iterative algorithm using the surface data to correct the VHF image and retrieve accurate subsurface heights. Simulation results showed the approach improved height resolution and coherence by 20-40% compared to conventional SAR.
Multi-Resolution Analysis: MRA Based Bright Band Height Estimation with Preci...Waqas Tariq
A method for reconstruction of cross section of rainfall situations with precipitation radar data based on wavelet analysis of Multi-Resolution Analysis (MRA) which allows extract a peak of the radar reflectivity is proposed in order to detect bright band height. It is found that the bright band height can be estimated by using the MRA with the basis of Daubechies wavelet family. It is also found that the boundaries in rainfall structure can be clearly extracted with MRA.
Probing the Detailed Physics of Hot Baryons with Lynx: Predictions from Mock ...John ZuHone
The document discusses how the Lynx X-ray observatory's high angular resolution, large effective area, and high spectral resolution would allow for detailed studies of the physics of hot baryons in galaxy clusters and galaxies. Mock observations using simulation tools show Lynx could map gas structures at small scales, detect pressure discontinuities like shocks, and observe velocity fields with higher precision than current instruments. The capabilities would provide new insights into gas properties in clusters and halos of galaxies.
Radiation Q bounds for small electric dipoles over a conducting ground planeYong Heui Cho
This document discusses theoretical bounds on the quality factor (Q) of small electric dipole antennas placed over a conducting ground plane. It finds that for vertically polarized dipoles, the Q can decrease by approximately a factor of two compared to an antenna of the same size in free space, indicating a doubling of bandwidth. This bandwidth enhancement is validated through simulations and measurements of small spherical helix dipole antennas over a ground plane. For horizontally polarized dipoles, the Q increases significantly compared to free space as the ground separation decreases. The analysis divides space into regions and uses vector spherical wave functions to calculate stored electric and magnetic energies, from which Q is determined following definitions by Chu and Thal.
The document describes a new algorithm for correcting the bidirectional reflectance distribution function (BRDF) of remote sensing reflectance measurements in coastal waters. Through radiative transfer simulations for a wide range of conditions, the authors developed a model relating remote sensing reflectance to the inherent optical properties of coastal waters. The new BRDF correction algorithm was shown to reduce uncertainty to below 1% when applied to both in situ and satellite ocean color data, improving on an existing open ocean algorithm. Its application significantly improved the match between in situ and MODIS satellite measurements of coastal waters.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Instrument to measure the bidirectional reflectanceajsatienza
This instrument measures the bidirectional reflectance distribution function (BRDF) of surfaces with the following properties:
1. It measures the BRDF for eight illumination angles from 0 to 65 degrees, three colors (475, 570, 658 nm), and over 100 selected viewing angles.
2. The viewing zenith angles range from 5 to 65 degrees, and the azimuth angles range from 0 to ±180 degrees relative to the illumination direction.
3. Tests show it can measure the BRDF of flat surfaces with a precision of 1-5% and an accuracy of 10% of the measured reflectance.
The document discusses image distortion effects in subsurface synthetic aperture radar (SAR) imaging of deserts and proposes an iterative corrective approach. It summarizes that subsurface SAR can map subsurface topography under sand but images are distorted due to geometric distortion and defocusing. It then proposes using dual-frequency SAR, with VHF penetrating sand and Ka imaging the surface, along with an iterative algorithm using the surface data to correct the VHF image and retrieve accurate subsurface heights. Simulation results showed the approach improved height resolution and coherence by 20-40% compared to conventional SAR.
This document summarizes a research paper that presents a dual open stub loaded square microstrip antenna (DOSMSA) for quad-band wireless communication applications. The DOSMSA consists of a square patch with two open stubs placed diagonally. Measurements show the DOSMSA operates over four bands from 2.88-8.55 GHz with gains up to 3.21 dB, compared to 0.8 dB for a basic square microstrip antenna. The DOSMSA design achieves quad-band operation using a simple stub loading technique while reducing the antenna's copper area by 7.8% compared to the basic design. The antenna has broadside radiation patterns and could enable applications in WLAN and WiMAX
Synthesis of Optimized Asymmetrical Sum Patterns Using Conventional MethodIOSR Journals
Abstract: Sum patterns find applications in Radar for searching and ranging of the targets. A sum pattern with low sidelobe level is a desirable feature in these applications, in order to reduce EMI problems. Sum patterns with Asymmetrical sidelobe topography are considered, in applications where only certain angular regions of pattern are required to have low sidelobe level. Asymmetrical pattern characteristics can have lower beam widths for given design specifications as compared to symmetrical patterns. In view of this, a conventional method of synthesis is carried out in this paper, to produce asymmetrical sidelobe level patterns using discrete arrays. The effect of beam scanning on the pattern behavior is also analyzed for the above synthesized patterns. Keywords: sum pattern, asymmetrical sidelobe level, beam width, complex excitation weights, and discrete array.
Students aged 12 to 18 observed the Big Bang using an 11-inch telescope. They measured redshifts of galaxies and deduced quantitative conclusions about the age of the universe and density of dark matter. Key findings included:
- Measuring significant redshifts of 0.0077 and 0.003 for galaxies NGC 3516 and M66, matching literature values.
- Interpreting the main emission line at 6590 Angstroms as hydrogen-alpha, indicating a redshift of 0.0077 for NGC 3516.
- Concluding the Big Bang observations were highly significant based on statistical analysis, despite limitations of the small telescope.
C&T RF Antennas Inc provides information about antenna radiation patterns and gain. The radiation pattern shows the spatial distribution of the antenna's transmitted or received signal strength in different directions. Key parameters of the pattern include main lobe width, side lobe level, and front-to-back ratio. Antenna gain is determined by the radiation pattern and quantifies how well the antenna concentrates transmitted power, with a narrow main lobe and low side lobes resulting in higher gain. Proper antenna selection is important for optimizing cellular network coverage and performance.
The document summarizes a study on the effect of substrate materials on the performance of an ultra-wideband (UWB) antenna. A circularly polarized UWB antenna was designed using FR4 substrate and fed by a coplanar waveguide. Simulations were performed in HFSS to analyze the antenna's return loss, voltage standing wave ratio (VSWR), input impedance, gain, and radiation patterns at different resonant frequencies. The performance was also compared for different substrate materials, and FR4 provided the best results with a 9.745 GHz bandwidth. Key findings included FR4 achieving less than -10 dB return loss and VSWR below 2 across the operating band with a maximum gain of 4.5 dBi and quasi
Comparative Calibration Method Between two Different Wavelengths With Aureole...Waqas Tariq
A multi-stage method for calibration of sunphotometer is proposed by combining comparison calibration method between two different wavelengths with aureole observation method for long wavelength calibration. Its effectiveness in reducing the influences for calibration due to molecular and aerosolfs extinction in the unstable turbidity conditions is clarified. By comparing the calculated results with the proposed method and the existing individually calibration method, it is found that the proposed method is superior to the existing method in terms of calibration accuracy. Namely, Through a comparison between ILM and the proposed method using band 0.87um as reference, the largest calibration errors are 0.0014, 0.0428 by PM are lower than that by ILM (0.011,0.0489) for sky radiances with no error and -3~+3%, -5~+5% errors. By analyzing the observation data of 15 days with POM-1 Skyradiometer, the largest standard deviation of calibration constants by PM is 0.02016, and is lower than that by ILM (0.03858).
This work measured experimentally, and calculated theoretically using the existing Friis Fomula, the Attenuation of 92.1 MHz (Ajilete FM) Signals along Gambari(Lat 8o291N; Long 4o291) – Oyo-Road(Lat 7o501N; Long 3o561E), Oyo State Nigeria. The two results were compared. The experimental Measurement campaign was achieved by using an appropriate design dipole antenna, well matched to (810 GSP Analyser), to determine the attenuation. The calculated results correlated very well with the measurements (Correlation Coefficient Value R2=1). But, they are not accurate when compared with the measurements (Chi- square values equal zero for received power, measured attenuation). The inaccuracies of the results for the existing formula with the measurements may be due to hills, valleys, trees and bends along the links. Hence the accuracy of the model used can only be effectively confirmed in areas free of the obstacles mentioned above. By applying LEAST SQUARE fit method to the experimental measured data, the analytical models, P(x)= 0.0154x2-1.3575x-38.7620 and A(x)= 0132x2 -1.2464x-104.8487, in the form of polynomial of degree two, were obtained respectively for received power and measured attenuation. The analytical model obtained is therefore recommended for use in an area characterised with bends, valleys, hills and trees, since the model has taken into consideration all these factors. In addition, repeater stations should be installed for effective transmission and for wider coverage in forested and valley areas. Moreover, transmitter of higher value like ten kilowatts should be employed for long distance transmission
TH1.L09 - INVESTIGATIONS ON TOPS INTERFEROMETRY WITH TERRASAR-Xgrssieee
The document discusses techniques for interferometry using TerraSAR-X data acquired in TOPS mode. Two approaches are suggested to estimate constant azimuth offsets between bursts using spectral diversity: 1) Using spectral bands within bursts. 2) Using the overlapping area between bursts. Experimental results with TerraSAR-X data validate these approaches and compare TOPS to ScanSAR and stripmap modes. TOPS-stripmap interferograms seem feasible under a persistent scatterer approach with additional processing needed if there is an azimuth displacement.
This document summarizes a technique called structure-oriented, frequency-dependent (SOFD) filtering that can significantly increase the usable bandwidth of seismic data. The technique uses structure tensors computed from a stack to guide frequency-dependent filtering of individual frequency bands. This preserves structural features while improving signal-to-noise. The technique is demonstrated on land seismic data, improving signal quality at low and high frequencies. Well ties show the enhanced bandwidth data matches well logs, extending usable frequencies without degrading tie quality. The technique can be applied to pre-stack data by filtering offset volumes separately.
This document summarizes a new approach for classifying remote sensing signatures extracted from multispectral imagery. It combines spectral signatures to perform accurate classification. Simulation results are provided to verify the efficiency of the proposed weighted pixel statistics approach, which uses information from multiple spectral bands. It is shown to provide more accurate and less smoothed identification of classes compared to traditional weighted order statistics methods.
This document discusses the design of a circularly polarized circular patch antenna. It first describes designing a circular patch antenna with a single probe feed to produce linear polarization, then with two probes fed 90 degrees out of phase to produce circular polarization. Simulations showed the dual-probe antenna had a bandwidth of 8.33%, gain of 7.4 dBi, and nearly circular polarization. Parameters like patch radius and substrate thickness were analyzed, showing resonance frequency decreases with larger radius and increases with thinner substrate. The document concludes the dual-probe antenna design successfully produced circular polarization compared to the single-probe linear design.
This document discusses and compares different technologies for modern land seismic recording systems, including geophone arrays versus point receivers, cable-based versus cable-less systems, and 1C versus 3C sensors. It finds that while point receivers and cable-less systems can provide benefits at coarse spatial sampling, geophone arrays and cable-based systems have advantages at finer sampling intervals, including improved signal-to-noise ratio and quality control. The optimal technology depends on the specific survey needs and parameters. Weight analysis shows cable-based systems have lower weight at sampling intervals under around 50 meters.
This document describes the design and testing of a hexagonal fractal ultra-wideband antenna using Koch geometry. The introduction of Koch fractal geometry to the monopole and ground plane generates additional resonances, achieving an operational bandwidth of 122%. The compact 31 mm × 28 mm antenna exhibits an omnidirectional radiation pattern with good reflection coefficient across the UWB frequency range. Measurements of the fabricated prototype match well with simulations and demonstrate UWB performance from 3.4 to 13 GHz. Time-domain analysis shows good pulse preservation capability. In summary, the use of Koch fractal geometry enables both miniaturization and wide bandwidth in the proposed UWB antenna design.
This document summarizes key concepts in electron beam dosimetry and monitor unit calculations. It discusses electron beam interactions, depth dose distributions, characteristics of clinical beams, and factors that affect dose such as field size, distance, and inhomogeneities. It also describes how monitor units are calculated using output factors, distance corrections, and prescription isodose levels to determine the monitor units needed to deliver a prescribed dose to the treatment volume. Sample problems demonstrate how these concepts are applied in practice.
This study evaluated the use of multispectral and hyperspectral sensor data to estimate crop residue cover over agricultural areas. Hyperspectral data provided more accurate residue cover estimates than multispectral data due to greater spectral sensitivity. Models using a cellulose absorption index performed best. Residue cover estimates from hyperspectral data were substituted into models developed using multispectral data, improving accuracy of estimates from broader coverage sensors. Future work will focus on sensor fusion methods and integrating residue cover information into hydrologic models.
Proposed P-shaped Microstrip Antenna Array for Wireless Communication Applica...TELKOMNIKA JOURNAL
In this paper a P-shaped microstrip antenna array is proposed for X-band applications in the
frequency range (8.1567-9.3811) GHz .The gain obtained in this frequency range is about 8.305 dBi.
The reflection coefficient is less than - 10 dB in the above frequency range. The simulation results were
obtained for the optimum parameters using the CST software while the practical test was carried out using
Vector Network Analyzer (VNA). The microstrip antenna was manufactured using FR-4 substrate with
relative dielectric constant of 4.3 and loss tangent 푡푎푛 훿 = 0.002.The simulation and practical results were
compared. The size of the antenna array is (33 × 70 × 1.6) 푚푚3. This array is suitable for satellite
communication, radar application.
The document summarizes research on measuring the orientation and randomness of vegetation using polarimetric synthetic aperture radar (SAR) data. It describes models that characterize volume scattering components and their evolution over time. The document also analyzes parameters like mean orientation angle and randomness that are estimated using model-based polarimetric decomposition. Specifically, it studies how these parameters contribute to the decomposition and affect the co-polarization ratio of scattered radar signals.
This study investigates the scale effect of the relationship between the normalized difference vegetation index (NDVI) and land surface temperature (T) and improves a thermal sharpening method called TsHARP. The study finds that the slope of the NDVI-T relationship increases more significantly with spatial extent than with spatial resolution alone. An improved TsHARP method is developed that establishes the NDVI-T regression relationship based on the spatial extent of individual thermal pixels, rather than the entire image extent. Testing shows the improved method produces a sharper and more accurate thermal sharpening result compared to the original TsHARP method.
New Miniature Planar Microstrip Antenna Using DGS for ISM ApplicationsTELKOMNIKA JOURNAL
The aim of this paper is to use defected ground structures (DGS) in order to miniaturize a
microstrip patch antenna. The DGS structure is integrated in the ground plane to improve the performance
of the planar antenna, and shifted the resonance frequency from 5.8 GHz to 2.5 GHz, with a
miniaturization up to 83%. The antenna is designed, optimized, and miniaturized by using the CST MWstudio,
mounted on an FR-4 substrate having a dielectric constant 4.4, a loss tangent tan (ɸ)=0.025,
thickness of 1.6 mm with the whole area of 34X34 mm2.The proposed antenna is suitable for ISM
(Industrial, Scientific and Medical) applications at 2.5 GHz with S11 ≤(-10) dB. The antenna is fed by
50ohm input impedance and it has good performances in terms of matching input impedance and radiation
pattern. The proposed antenna was fabricated and tested.Simulation and measurement results are in good
agreement.
This document summarizes a research paper that proposes a compact hexagonal circularly polarized patch antenna for RFID applications. Key points:
- The antenna has a hexagonal patch with a central elliptical slot and two circular slots to generate circular polarization with a single feed.
- Dimensions of the slots are optimized to detune the fundamental TM11 mode into two orthogonal modes with nearly equal resonant frequencies and a 90 degree phase difference, satisfying circular polarization criteria.
- Measurements show the antenna achieves good impedance matching and circular polarization radiation characteristics at 2.45 GHz, making it suitable for RFID reader applications.
HEXAGONAL CIRCULARLY POLARIZED PATCH ANTENNA FOR RFID APPLICATIONSIJCI JOURNAL
A compact design of a hexagonal single feed circularly polarized microstrip antenna for RFID applications is
proposed. This structure fabricated on FR4 substrate offers compactness, good axial ratio bandwidth with a
broadside radiation characteristic in the entire band, better gain, good impedance bandwidth at a resonant
frequency of 2.45 GHz. The structure is suitable for RFID reader antenna applications.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
This document summarizes a research paper that presents a dual open stub loaded square microstrip antenna (DOSMSA) for quad-band wireless communication applications. The DOSMSA consists of a square patch with two open stubs placed diagonally. Measurements show the DOSMSA operates over four bands from 2.88-8.55 GHz with gains up to 3.21 dB, compared to 0.8 dB for a basic square microstrip antenna. The DOSMSA design achieves quad-band operation using a simple stub loading technique while reducing the antenna's copper area by 7.8% compared to the basic design. The antenna has broadside radiation patterns and could enable applications in WLAN and WiMAX
Synthesis of Optimized Asymmetrical Sum Patterns Using Conventional MethodIOSR Journals
Abstract: Sum patterns find applications in Radar for searching and ranging of the targets. A sum pattern with low sidelobe level is a desirable feature in these applications, in order to reduce EMI problems. Sum patterns with Asymmetrical sidelobe topography are considered, in applications where only certain angular regions of pattern are required to have low sidelobe level. Asymmetrical pattern characteristics can have lower beam widths for given design specifications as compared to symmetrical patterns. In view of this, a conventional method of synthesis is carried out in this paper, to produce asymmetrical sidelobe level patterns using discrete arrays. The effect of beam scanning on the pattern behavior is also analyzed for the above synthesized patterns. Keywords: sum pattern, asymmetrical sidelobe level, beam width, complex excitation weights, and discrete array.
Students aged 12 to 18 observed the Big Bang using an 11-inch telescope. They measured redshifts of galaxies and deduced quantitative conclusions about the age of the universe and density of dark matter. Key findings included:
- Measuring significant redshifts of 0.0077 and 0.003 for galaxies NGC 3516 and M66, matching literature values.
- Interpreting the main emission line at 6590 Angstroms as hydrogen-alpha, indicating a redshift of 0.0077 for NGC 3516.
- Concluding the Big Bang observations were highly significant based on statistical analysis, despite limitations of the small telescope.
C&T RF Antennas Inc provides information about antenna radiation patterns and gain. The radiation pattern shows the spatial distribution of the antenna's transmitted or received signal strength in different directions. Key parameters of the pattern include main lobe width, side lobe level, and front-to-back ratio. Antenna gain is determined by the radiation pattern and quantifies how well the antenna concentrates transmitted power, with a narrow main lobe and low side lobes resulting in higher gain. Proper antenna selection is important for optimizing cellular network coverage and performance.
The document summarizes a study on the effect of substrate materials on the performance of an ultra-wideband (UWB) antenna. A circularly polarized UWB antenna was designed using FR4 substrate and fed by a coplanar waveguide. Simulations were performed in HFSS to analyze the antenna's return loss, voltage standing wave ratio (VSWR), input impedance, gain, and radiation patterns at different resonant frequencies. The performance was also compared for different substrate materials, and FR4 provided the best results with a 9.745 GHz bandwidth. Key findings included FR4 achieving less than -10 dB return loss and VSWR below 2 across the operating band with a maximum gain of 4.5 dBi and quasi
Comparative Calibration Method Between two Different Wavelengths With Aureole...Waqas Tariq
A multi-stage method for calibration of sunphotometer is proposed by combining comparison calibration method between two different wavelengths with aureole observation method for long wavelength calibration. Its effectiveness in reducing the influences for calibration due to molecular and aerosolfs extinction in the unstable turbidity conditions is clarified. By comparing the calculated results with the proposed method and the existing individually calibration method, it is found that the proposed method is superior to the existing method in terms of calibration accuracy. Namely, Through a comparison between ILM and the proposed method using band 0.87um as reference, the largest calibration errors are 0.0014, 0.0428 by PM are lower than that by ILM (0.011,0.0489) for sky radiances with no error and -3~+3%, -5~+5% errors. By analyzing the observation data of 15 days with POM-1 Skyradiometer, the largest standard deviation of calibration constants by PM is 0.02016, and is lower than that by ILM (0.03858).
This work measured experimentally, and calculated theoretically using the existing Friis Fomula, the Attenuation of 92.1 MHz (Ajilete FM) Signals along Gambari(Lat 8o291N; Long 4o291) – Oyo-Road(Lat 7o501N; Long 3o561E), Oyo State Nigeria. The two results were compared. The experimental Measurement campaign was achieved by using an appropriate design dipole antenna, well matched to (810 GSP Analyser), to determine the attenuation. The calculated results correlated very well with the measurements (Correlation Coefficient Value R2=1). But, they are not accurate when compared with the measurements (Chi- square values equal zero for received power, measured attenuation). The inaccuracies of the results for the existing formula with the measurements may be due to hills, valleys, trees and bends along the links. Hence the accuracy of the model used can only be effectively confirmed in areas free of the obstacles mentioned above. By applying LEAST SQUARE fit method to the experimental measured data, the analytical models, P(x)= 0.0154x2-1.3575x-38.7620 and A(x)= 0132x2 -1.2464x-104.8487, in the form of polynomial of degree two, were obtained respectively for received power and measured attenuation. The analytical model obtained is therefore recommended for use in an area characterised with bends, valleys, hills and trees, since the model has taken into consideration all these factors. In addition, repeater stations should be installed for effective transmission and for wider coverage in forested and valley areas. Moreover, transmitter of higher value like ten kilowatts should be employed for long distance transmission
TH1.L09 - INVESTIGATIONS ON TOPS INTERFEROMETRY WITH TERRASAR-Xgrssieee
The document discusses techniques for interferometry using TerraSAR-X data acquired in TOPS mode. Two approaches are suggested to estimate constant azimuth offsets between bursts using spectral diversity: 1) Using spectral bands within bursts. 2) Using the overlapping area between bursts. Experimental results with TerraSAR-X data validate these approaches and compare TOPS to ScanSAR and stripmap modes. TOPS-stripmap interferograms seem feasible under a persistent scatterer approach with additional processing needed if there is an azimuth displacement.
This document summarizes a technique called structure-oriented, frequency-dependent (SOFD) filtering that can significantly increase the usable bandwidth of seismic data. The technique uses structure tensors computed from a stack to guide frequency-dependent filtering of individual frequency bands. This preserves structural features while improving signal-to-noise. The technique is demonstrated on land seismic data, improving signal quality at low and high frequencies. Well ties show the enhanced bandwidth data matches well logs, extending usable frequencies without degrading tie quality. The technique can be applied to pre-stack data by filtering offset volumes separately.
This document summarizes a new approach for classifying remote sensing signatures extracted from multispectral imagery. It combines spectral signatures to perform accurate classification. Simulation results are provided to verify the efficiency of the proposed weighted pixel statistics approach, which uses information from multiple spectral bands. It is shown to provide more accurate and less smoothed identification of classes compared to traditional weighted order statistics methods.
This document discusses the design of a circularly polarized circular patch antenna. It first describes designing a circular patch antenna with a single probe feed to produce linear polarization, then with two probes fed 90 degrees out of phase to produce circular polarization. Simulations showed the dual-probe antenna had a bandwidth of 8.33%, gain of 7.4 dBi, and nearly circular polarization. Parameters like patch radius and substrate thickness were analyzed, showing resonance frequency decreases with larger radius and increases with thinner substrate. The document concludes the dual-probe antenna design successfully produced circular polarization compared to the single-probe linear design.
This document discusses and compares different technologies for modern land seismic recording systems, including geophone arrays versus point receivers, cable-based versus cable-less systems, and 1C versus 3C sensors. It finds that while point receivers and cable-less systems can provide benefits at coarse spatial sampling, geophone arrays and cable-based systems have advantages at finer sampling intervals, including improved signal-to-noise ratio and quality control. The optimal technology depends on the specific survey needs and parameters. Weight analysis shows cable-based systems have lower weight at sampling intervals under around 50 meters.
This document describes the design and testing of a hexagonal fractal ultra-wideband antenna using Koch geometry. The introduction of Koch fractal geometry to the monopole and ground plane generates additional resonances, achieving an operational bandwidth of 122%. The compact 31 mm × 28 mm antenna exhibits an omnidirectional radiation pattern with good reflection coefficient across the UWB frequency range. Measurements of the fabricated prototype match well with simulations and demonstrate UWB performance from 3.4 to 13 GHz. Time-domain analysis shows good pulse preservation capability. In summary, the use of Koch fractal geometry enables both miniaturization and wide bandwidth in the proposed UWB antenna design.
This document summarizes key concepts in electron beam dosimetry and monitor unit calculations. It discusses electron beam interactions, depth dose distributions, characteristics of clinical beams, and factors that affect dose such as field size, distance, and inhomogeneities. It also describes how monitor units are calculated using output factors, distance corrections, and prescription isodose levels to determine the monitor units needed to deliver a prescribed dose to the treatment volume. Sample problems demonstrate how these concepts are applied in practice.
This study evaluated the use of multispectral and hyperspectral sensor data to estimate crop residue cover over agricultural areas. Hyperspectral data provided more accurate residue cover estimates than multispectral data due to greater spectral sensitivity. Models using a cellulose absorption index performed best. Residue cover estimates from hyperspectral data were substituted into models developed using multispectral data, improving accuracy of estimates from broader coverage sensors. Future work will focus on sensor fusion methods and integrating residue cover information into hydrologic models.
Proposed P-shaped Microstrip Antenna Array for Wireless Communication Applica...TELKOMNIKA JOURNAL
In this paper a P-shaped microstrip antenna array is proposed for X-band applications in the
frequency range (8.1567-9.3811) GHz .The gain obtained in this frequency range is about 8.305 dBi.
The reflection coefficient is less than - 10 dB in the above frequency range. The simulation results were
obtained for the optimum parameters using the CST software while the practical test was carried out using
Vector Network Analyzer (VNA). The microstrip antenna was manufactured using FR-4 substrate with
relative dielectric constant of 4.3 and loss tangent 푡푎푛 훿 = 0.002.The simulation and practical results were
compared. The size of the antenna array is (33 × 70 × 1.6) 푚푚3. This array is suitable for satellite
communication, radar application.
The document summarizes research on measuring the orientation and randomness of vegetation using polarimetric synthetic aperture radar (SAR) data. It describes models that characterize volume scattering components and their evolution over time. The document also analyzes parameters like mean orientation angle and randomness that are estimated using model-based polarimetric decomposition. Specifically, it studies how these parameters contribute to the decomposition and affect the co-polarization ratio of scattered radar signals.
This study investigates the scale effect of the relationship between the normalized difference vegetation index (NDVI) and land surface temperature (T) and improves a thermal sharpening method called TsHARP. The study finds that the slope of the NDVI-T relationship increases more significantly with spatial extent than with spatial resolution alone. An improved TsHARP method is developed that establishes the NDVI-T regression relationship based on the spatial extent of individual thermal pixels, rather than the entire image extent. Testing shows the improved method produces a sharper and more accurate thermal sharpening result compared to the original TsHARP method.
New Miniature Planar Microstrip Antenna Using DGS for ISM ApplicationsTELKOMNIKA JOURNAL
The aim of this paper is to use defected ground structures (DGS) in order to miniaturize a
microstrip patch antenna. The DGS structure is integrated in the ground plane to improve the performance
of the planar antenna, and shifted the resonance frequency from 5.8 GHz to 2.5 GHz, with a
miniaturization up to 83%. The antenna is designed, optimized, and miniaturized by using the CST MWstudio,
mounted on an FR-4 substrate having a dielectric constant 4.4, a loss tangent tan (ɸ)=0.025,
thickness of 1.6 mm with the whole area of 34X34 mm2.The proposed antenna is suitable for ISM
(Industrial, Scientific and Medical) applications at 2.5 GHz with S11 ≤(-10) dB. The antenna is fed by
50ohm input impedance and it has good performances in terms of matching input impedance and radiation
pattern. The proposed antenna was fabricated and tested.Simulation and measurement results are in good
agreement.
This document summarizes a research paper that proposes a compact hexagonal circularly polarized patch antenna for RFID applications. Key points:
- The antenna has a hexagonal patch with a central elliptical slot and two circular slots to generate circular polarization with a single feed.
- Dimensions of the slots are optimized to detune the fundamental TM11 mode into two orthogonal modes with nearly equal resonant frequencies and a 90 degree phase difference, satisfying circular polarization criteria.
- Measurements show the antenna achieves good impedance matching and circular polarization radiation characteristics at 2.45 GHz, making it suitable for RFID reader applications.
HEXAGONAL CIRCULARLY POLARIZED PATCH ANTENNA FOR RFID APPLICATIONSIJCI JOURNAL
A compact design of a hexagonal single feed circularly polarized microstrip antenna for RFID applications is
proposed. This structure fabricated on FR4 substrate offers compactness, good axial ratio bandwidth with a
broadside radiation characteristic in the entire band, better gain, good impedance bandwidth at a resonant
frequency of 2.45 GHz. The structure is suitable for RFID reader antenna applications.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This document summarizes a research paper that proposes a modified patch antenna design for dual-band operation at 3 GHz and 5 GHz. The antenna design incorporates slots of different sizes and a defected ground structure to achieve the dual-band functionality. Simulation results using IE3D software show return losses of -12.17 dB at 3 GHz and -10.04 dB at 5 GHz. The fabricated antenna prototype shows good agreement with the simulated results, with a measured return loss of -12.71 dB. The proposed antenna design achieves the goal of operating at two frequency bands for applications requiring body-centric wireless communication.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
IRJET- Design and Analysis of LPDA Antenna for through the Wall Detection ...IRJET Journal
This document presents the design, simulation, and analysis of a logarithmic periodic dipole antenna (LPDA) for through-the-wall detection applications operating in the frequency range of 0.5-3 GHz. Key features of the antenna include a gain over 6 dB across the bandwidth, a VSWR less than 2.5, and a directional radiation pattern optimized for detecting targets behind walls. The antenna design was modified from a traditional LPDA by using strip dipoles rather than cylindrical ones and adding a reflector to increase directivity. Simulations showed the antenna meets design requirements for through-wall detection in terms of impedance matching, gain, and minimization of side lobes.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
1) An optimum pyramidal horn antenna was designed to provide a gain of 20dB at a center frequency of 9.5GHz.
2) The horn was fabricated from aluminum sheet with dimensions of 13.5cm by 11.5cm.
3) The performance of the fabricated horn was evaluated both analytically and experimentally. Results showed good agreement between calculated and measured parameters including gain, directivity, impedance, and scattering parameters.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna
resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different
details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different
details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna
resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different
details. Paper gives good agreement between measured and simulated results.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This document summarizes a research paper that proposes a modified patch antenna design for dual-band operation at 3 GHz and 5 GHz. The antenna design incorporates defected ground structures and slots cut into the patch and ground planes. Simulation results show return losses of -12.17 dB at 3 GHz and -10.04 dB at 5 GHz, meeting the design goals. The antenna was fabricated and measured results matched well with simulations, validating the proposed antenna design for body-centric wireless applications.
BODY ANTENNA WITH DGS FOR BODY CENTRIC WIRELESS COMMUNICATION SYSTEMjantjournal
This paper presents modified patch antenna for 3 GHz and 5 GHz operating frequencies. Here different approaches are studied by varying slot sizes, defected ground size, notch and also changing feed position. Insertion of slots gives dual frequency operation. Notch provides shifting of lower frequency band towards left hand side. Here combined effect of each techniques adopted gives desired result. Proposed antenna resonates for 3 and 5 GHz frequency. Simulation is done using IE3D software for various parameters. Return loss of final design was -12.17 dB for 3 GHz frequency and VSWR of 1.65. For 5 GHz simulation response was -10.04dB return loss and VSWR of 1.91. Proposed antenna is fabricated giving different details. Paper gives good agreement between measured and simulated results.
This document presents the design and analysis of a microstrip patch antenna for triple band applications in digital communication systems. The antenna is designed to operate at 1.5 GHz, 2.4 GHz, and 5.5 GHz bands. It consists of a rectangular patch fed by a microstrip line with two additional arms of different lengths acting as resonators. Simulation results show the antenna achieves impedance matching across bandwidths of 700 MHz, 800 MHz, and 1 GHz at the three frequencies. It has an omnidirectional radiation pattern and gain between 5-6 dBi. The compact triple band design reduces the antenna size by 67% compared to a conventional patch antenna.
This document describes the design and analysis of a two half-ring and half circular patch microstrip antenna for dual-band applications in the C-band frequencies. The antenna is designed to operate at 4.1 GHz and 6.5 GHz with moderate return loss and gain. Simulation results show the antenna achieves a peak gain of 3.08 dB at 4.1 GHz and 4.14 dB at 6.5 GHz when fabricated on FR4 epoxy substrate with a dielectric constant of 4.4 and thickness of 3 mm. Current distribution and radiation patterns are also analyzed to understand the antenna performance at the resonant frequencies.
The document summarizes the design, testing, and performance of a Landstorfer antenna. Key points:
1) The Landstorfer antenna is a modification of the traditional Yagi-Uda array that uses curved elements to increase directivity and decrease side lobes, at the cost of increased element length.
2) The antenna was designed based on an image from a reference book, scaled to have a driven element length of 3λ/2, and milled onto an FR4 board.
3) Testing found a VSWR of 6.5, corresponding to 53.7% loss. Maximum directivity was measured at 1.52GHz, with half power beamwidths of 102 and 30 degrees and
Discover timeless style with the 2022 Vintage Roman Numerals Men's Ring. Crafted from premium stainless steel, this 6mm wide ring embodies elegance and durability. Perfect as a gift, it seamlessly blends classic Roman numeral detailing with modern sophistication, making it an ideal accessory for any occasion.
https://rb.gy/usj1a2
Taurus Zodiac Sign: Unveiling the Traits, Dates, and Horoscope Insights of th...my Pandit
Dive into the steadfast world of the Taurus Zodiac Sign. Discover the grounded, stable, and logical nature of Taurus individuals, and explore their key personality traits, important dates, and horoscope insights. Learn how the determination and patience of the Taurus sign make them the rock-steady achievers and anchors of the zodiac.
Navigating the world of forex trading can be challenging, especially for beginners. To help you make an informed decision, we have comprehensively compared the best forex brokers in India for 2024. This article, reviewed by Top Forex Brokers Review, will cover featured award winners, the best forex brokers, featured offers, the best copy trading platforms, the best forex brokers for beginners, the best MetaTrader brokers, and recently updated reviews. We will focus on FP Markets, Black Bull, EightCap, IC Markets, and Octa.
Storytelling is an incredibly valuable tool to share data and information. To get the most impact from stories there are a number of key ingredients. These are based on science and human nature. Using these elements in a story you can deliver information impactfully, ensure action and drive change.
Unveiling the Dynamic Personalities, Key Dates, and Horoscope Insights: Gemin...my Pandit
Explore the fascinating world of the Gemini Zodiac Sign. Discover the unique personality traits, key dates, and horoscope insights of Gemini individuals. Learn how their sociable, communicative nature and boundless curiosity make them the dynamic explorers of the zodiac. Dive into the duality of the Gemini sign and understand their intellectual and adventurous spirit.
At Techbox Square, in Singapore, we're not just creative web designers and developers, we're the driving force behind your brand identity. Contact us today.
At Techbox Square, in Singapore, we're not just creative web designers and developers, we're the driving force behind your brand identity. Contact us today.
Event Report - SAP Sapphire 2024 Orlando - lots of innovation and old challengesHolger Mueller
Holger Mueller of Constellation Research shares his key takeaways from SAP's Sapphire confernece, held in Orlando, June 3rd till 5th 2024, in the Orange Convention Center.
Recruiting in the Digital Age: A Social Media MasterclassLuanWise
In this masterclass, presented at the Global HR Summit on 5th June 2024, Luan Wise explored the essential features of social media platforms that support talent acquisition, including LinkedIn, Facebook, Instagram, X (formerly Twitter) and TikTok.
The 10 Most Influential Leaders Guiding Corporate Evolution, 2024.pdfthesiliconleaders
In the recent edition, The 10 Most Influential Leaders Guiding Corporate Evolution, 2024, The Silicon Leaders magazine gladly features Dejan Štancer, President of the Global Chamber of Business Leaders (GCBL), along with other leaders.
B2B payments are rapidly changing. Find out the 5 key questions you need to be asking yourself to be sure you are mastering B2B payments today. Learn more at www.BlueSnap.com.
1. FRESNEL-ZONE MEASUREMENT AND ANALYSIS OF A DUALPOLARIZED METEOROLOGICAL RADAR ANTENNA
D.B. Hayman, T.S. Bird and G.C. James
CSIRO Telecommunications and Industrial Physics
PO Box 76, Epping NSW 1710, Australia
Abstract
The use of dual polarization in meteorological radars offers significant advantages over single
polarization. Recently a standard single-polarization C-band radar was upgraded to operate in dualpolarization mode. The antenna has a 4.2m diameter parabolic reflector with a prime-focus feed. A
spherical Fresnel-zone holographic technique was used to obtain the radiation pattern for the
upgraded antenna. The sidelobes were higher than predicted and so the data was analyzed to
identify the relative contributions of shadowing from the feed crook and surface errors in the dish.
This paper describes practical considerations in the measurement of this antenna and the analysis of
the results.
Keywords: Antenna measurements, Fresnel zone, Holography.
1. Introduction
There is an increasing use of dual polarization in meteorological radars, particularly for research
applications. The additional data provided by dual polarization leads to improved understanding of clouds
and precipitation. For instance, droplet size can be estimated using the difference between the vertical and
horizontal reflectivities. Larger droplets are more oblate and will have a greater differential reflectivity
than smaller droplets [1,2].
The antenna discussed in this paper is based on a standard existing single-polarization-radar system that
was upgraded to provide dual polarization capability. The upgrade included a high-power-microwave
switch, a dual waveguide run to the antenna and a new feed and orthomode transducer (OMT) for the
antenna.
The existing single polarization feed crook was replaced with a dual polarization feed system. An axially
symmetric feed with a ring-slot flange was designed, along with an OMT. These were supported by struts
and fed by a dual waveguide run. The waveguide was covered with resonant absorber to minimise the
effects of reflections. The new feed crook was fitted to the antenna and the antenna measured to check the
performance of the upgrade (Fig. 1).
2. Fig. 1. Antenna with Upgraded Feed.
The target performance for the antenna was specified by the end user and included well matched copolarized beam patterns, low sidelobes, low cross polarization and high isolation between channels. The
basic parameters for the antenna are given in Table 1.
Antenna type
Diameter (D)
Focal ratio (f/D)
Half-cone angle
Beamwidth
Gain
Polarization
Frequency
Prime focus fed paraboloid
4.2 m
0.34
72°
0.9°
>45 dBi
Horizontal & vertical linear
5600 to 5650 MHz
Table 1. Summary of System Specifications.
This paper describes the measurement of the upgraded antenna and an analysis of the results.
2. Antenna Measurement Set-up
The antenna radiation patterns were obtained using a Fresnel-zone holographic technique [3]. All of the
measurements were made at the centre frequency, 5.625 GHz. The antenna was too large for our near-field
range and we could not measure the far-field directly as our longest range is 40 m and the Rayleigh
criterion, 2D2/λ, is 600 m. For the Fresnel zone approximation to apply, the distance must be more than [3]
3
D4 λ
2
= 9m
Our 40 m outdoor range, with its elevation over azimuth rotator, was well suited for this task. Fig. 2 shows
a schematic of the measurement set-up and Fig. 3 shows the antenna and source tower. The signal received
from the antenna and a reference signal, taken from a coupler placed just before the source horn, were fed
into an amplitude and phase microwave receiver. A computer logged the data and drove the antenna in
azimuth and elevation to produce a two dimensional map.
3. Fig. 2. Measurement Set-up.
The range length of 19 m was chosen as a compromise between the conflicting requirements of minimising
ground reflection and interference between the source and antenna under test (AUT).
The radiation pattern was sampled in elevation and azimuth in a rectangular grid over the angular range of
–11° to +10.5°; the asymmetry was for convenience in processing. This range was chosen to provide
sufficient coverage of the sidelobes. The resolution of the aperture field map is given by:
λ
2 sin θ
where θ is the half angle of the scan. In this case, the resolution was 5 mm which was adequate for our
analysis.
Fig. 3. Outdoor Antenna Range.
The number of samples required is determined by the Nyquist criterion which ensures there is no aliasing
of the predicted aperture field. The spacing, in radians, must be no more than the wavelength divided by
the diameter of the AUT; for this antenna, converting to degrees, the minimum spacing was 0.73°. We
sampled at 0.5° intervals giving a 44x44 point map. Each radiation pattern map took about 50 minutes to
complete. The size of the data set for this Fresnel-zone measurement was only about 5% of that required
for a near-field measurement giving a considerable saving in measurement time. To compensate for drift in
the signal, calibration points were obtained at regular intervals. These were on boresight for the co-polar
maps and near a cross-polar peak for the cross-polar maps.
Co- and cross-polarization data were taken with the set-up as described and processed using the following
six steps [3]:
(1) phase and amplitude drifts were corrected by interpolating between the calibration points;
(2) a correction was made to compensate for the offset in the centre of rotation as the antenna was set above
4. and forward of the centre of rotation;
(3) the aperture field was calculated by applying a Fourier transform and quadratic phase correction;
(4) a circle with a radius one wavelength larger than the reflector was used as a mask and the field was set
to zero outside it to remove measurement artifacts;
(5) a second Fourier transform was applied to produce a two dimensional map of the far-field, covering
±10° in both azimuth and elevation;
(6) cardinal and inter-cardinal plane pattern cuts were interpolated from the two dimensional maps.
The results are shown in the following sections.
Fig. 4. Measured Co-polar Far-Field Contour Plot with Contours at 3 dB Intervals.
Fig. 5. Measured Cross-polar Far-Field Contour Plot with Contours at 3 dB Intervals.
3. Antenna Patterns
The far-field antenna patterns obtained using the holographic technique are shown in Figs 4 to 8. There
was little difference between vertical and horizontal polarization and the results shown are all with the E-
5. field for the AUT horizontal. The sidelobe mask was supplied as a desired target by the user of the
antenna. The aperture amplitude and phase responses were used in analysing the antenna performance
(Fig. 9).
Fig. 6. Measured Co-polar Cardinal Plane Pattern Cuts.
Fig. 7. Measured Co-polar Intercardinal Plane Pattern Cuts.
Fig. 8. Measured Cross-polar Pattern Cuts.
Various figures of merit for the antenna were determined from the measurements and most were
6. satisfactory. The gain, determined through pattern integration, was 45.5 dB. The beamwidth varied from
0.9° to 0.95°. The peak cross-polar level was –32 dB. The patterns from the two polarizations were
closely matched. The sidelobes, however, were greater than the desired level, the worst case being
–21 dB (Fig. 7).
Fig. 9. Measured Aperture Amplitude with a Grey Scale Range of 30 dB.
Fig. 10. Surface Errors Normal to Dish Surface with Contours Spaced by 1 mm and Negative Contours
Dashed.
4. Sidelobe Analysis
When the antenna was measured, the sidelobe levels were considered too high and some effort went into
determining the cause. Preliminary theoretical studies, using a physical optics model, included blockage by
the feed but not the feed crook struts. It did not include surface errors in the reflector. The radiation
pattern cuts for the model are shown in Fig. 11. The predicted sidelobes are at –32 dB whereas the
measurements give sidelobes up to –21 dB.
7. Fig. 11. Preliminary Theoretical Model Cardinal Plane
Co-Polarized Pattern Cuts and 45° Cross-Polarized Cut.
Two likely candidates, suggested by the measured aperture data (Figs 9 and 10), for causing the high
sidelobes are the feed-crook shadow and the surface errors. The relative effects of these were tested by
both manipulating the measured data and modelling them.
The reflector surface errors were calculated by translating the aperture field phase variations into physical
deviations normal to the surface of the paraboloid (Fig. 10). The results from the vertically and
horizontally polarized measurements were very similar. The assumption that the phase distortions in the
aperture were dominated by the surface errors and not scattering from the feed crook or the struts was
supported by the random variation and lack of symmetry in the aperture phase. The r.m.s. surface error
calculated in this way was 1.6 mm and the maximum deviations were ±4 mm.
The surface errors were effectively removed from the measured data in the following way. Aperture data
was altered by setting all the phase terms to zero; the amplitude data was left unchanged. This
approximates the effect of having a perfect dish while retaining the effect of blockage due to the feed and
struts present. The effect of the feed-crook and struts on the aperture phase are assumed to be secondary.
The aperture field derived in this way was then transformed to give the far-field pattern. The horizontal
plane sidelobes dropped from –27 dB to –34 dB, which was below the theoretical level of –32 dB obtained
with a perfect paraboloid. The vertical sidelobes fell from –22 dB to –25 dB.
Fig. 12. Theoretical Radiation Pattern Including Surface Errors.
8. Fig. 13. Theoretical Radiation Pattern Including Feed-Crook Shadow.
The feed-crook shadow was investigated because the amplitude image (Fig. 9) was dominated by it. The
struts were not considered because they were not visible in the aperture map. The effect of the shadow was
removed from the measured data by filling in the region of the aperture map in shadow (Fig. 9) with values
similar to those on either side of the shadow. The feed crook was covered with a resonant absorbing
material and so the main effect of the crook was expected to be shadowing. This experiment showed a
significant reduction in the vertical plane sidelobes, particularly the second, but made little difference to the
horizontal plane.
The surface errors were modelled by introducing the random fluctuations into the surface of the reflector
with approximately the same characteristics of those indicated by the aperture map (Fig. 10). The predicted
results, shown in Fig. 12, indicate that the surface errors can result in sidelobe levels close to those
measured.
The blockage of the feed crook was included in the theoretical model of the antenna by setting the aperture
amplitude to zero in a band running from the centre of the antenna to the edge. The width of the band was
150 mm which was similar to that seen on the aperture map derived from measurement (Fig. 9). This
model gives sidelobes in the horizontal plane of –35 dB and those in the vertical plane at –27 dB. The level
without the blockage was –32 dB (Fig. 13).
Both the theoretical models and manipulation of the measured aperture data give indications of levels of
sidelobes but not the precise detail. They do, however, show the same general trends.
It can be concluded that surface errors are the major contributor to the horizontal plane sidelobes. The
vertical sidelobes appear to be affected to a similar extent by both the surface errors and aperture blockage.
6. Conclusions
The measurement of an upgraded meteorological radar antenna has been described. The antenna met all
the specifications except that the sidelobes were above the desired level. The main causes for this has been
shown to be surface errors in the dish and shadowing from the feed crook. To reduce these sidelobes, a
superior dish is required and further attention is needed to reduce the effect of blockage by the feed crook.
The manipulation of the aperture fields in both the measured and theoretical data proved an effective tool in
9. investigating mechanisms affecting the antenna performance.
7. Acknowledgments
The authors thank M. Wright, K. Smart, R. Forsyth, P. Doherty and K. Greene for their assistance with the
antenna upgrade and measurements.
References
[1] D Atlas ed., "Radar in meteorology: Battan Memorial and 40th Anniversary Radar Meteorology
Conference", Battan Memorial and 40th Anniversary Radar Meteorology Conference (1987 Boston,
Mass.), American Meteorological Society.
[2] T. Keenan, K. Glasson, F. Cummings, T. Bird, J. Keeler and J. Lutz: “The BMRC/NCAR Polarimetric
Radar System”, JWA Conference, Tsukuba, Japan. 24-25 Jan 1996.
[3] G.T. Poulton: “Microwave holography for antenna measurements”, IREECON'83, Sydney, Australia, 59 September 1983, pp. 256-258.