Printed UWB Circular and Modified Circular Disc Monopole Antennas
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Printed UWB Circular and Modified Circular Disc Monopole Antennas

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In this paper, we have investigated printed ...

In this paper, we have investigated printed
monopole antennas, which is basically printed microstrip
antenna with etched ground plane for UWB applications. In
particular, we have simulated two types of UWB printed
monopole antennas: circular and modified circular disk
monopole antennas. Simple rectangular microstrip lines are
used for feeding the printed monopole antennas. This UWB
monopole antenna designed works well for the whole UWB
frequency band 3.1-10.6GHz from the IE3D simulation
results.

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Printed UWB Circular and Modified Circular Disc Monopole Antennas Document Transcript

  • 1. ACEEE International Journal on Communication, Vol 1, No. 1, Jan 2010 Printed UWB Circular and Modified Circular Disc Monopole Antennas Ramu Pillalamarri, Jyoti Ranjan Panda and Rakhesh Singh Kshetrimayum Department of Electronics and Communication Engineering, Indian Institute of Technology, Guwahati, India Email: {p.ramu, j.panda, krs}@iitg.ernet.inAbstract- In this paper, we have investigated printed II. GEOMETRY OF PRINTED UWB MONOPOLEmonopole antennas, which is basically printed microstrip ANTENNAS AND SIMULATION RESULTSantenna with etched ground plane for UWB applications. Inparticular, we have simulated two types of UWB printed A. Circular Disc UWB Monopole Antennamonopole antennas: circular and modified circular diskmonopole antennas. Simple rectangular microstrip lines are The UWB antenna is designed on a FR4 substrate withused for feeding the printed monopole antennas. This UWB 4.4 relative permittivity and 1.6 mm thickness. Real partmonopole antenna designed works well for the whole UWB of antenna impedance is exactly 50 Ω at 7.0GHz,frequency band 3.1-10.6GHz from the IE3D simulation 11.0GHz and 11.5GHz where the imaginary part of theresults. antenna impedance equals zero as depicted in Fig. 1(c). Throughout the bandwidth of the UWB antenna, the realIndex Terms: UWB, printed monopole antennas part of the antenna impedance varies from 30 Ω to 90 Ω whereas the imaginary part of the antenna impedance is I INTRODUCTION in the range -30 Ω to +30 Ω that is not a major variation Ultra-Wideband (UWB) commonly refers to signal or of the antenna impedance. The final dimensions of thesystem that either has a large relative bandwidth (BW) or UWB antenna after doing an extensive simulation studya large absolute bandwidth [1]-[3]. Such a large BW are:offers specific advantages with respect to signal Dimensions of Circular Patch:robustness, information content and/or implementation Radius = 15.0 mm and metal thickness= 0.035mm.simplicity. But such systems have some fundamental Dimensions of Substrate:differences from the conventional narrowband systems. Width (W) = 50.0 mm and Length (L) =65.0 mmThe Federal Communications Commission (FCC) has Microstrip line:designated the 3.1 to 10.6 GHz band with Effective W=2.6mm and L=26.0mm .Isotropic Radiated Power (EIRP) below -41.3dBm/MHz Dimensions of Ground:for UWB Communications. W = 50.0mm and L =25.7mm. Some UWB antennas are much more complex than “g” is gap between the ground plane and patch.other existing single band, dual band and multi-band TABLE I: ANTENNA PARAMETERS VS FEED GAPantennas [4]-[6]. Most of the UWB monopole antennas g flow fhigh Antenna ηinvestigated till today is non-planar as in [5]-[6] and due (mm) (GHz) (GHz) Impedance (%)to their protruded structure, they cann’t be integrated withintegrated circuits and they are fragile. Few researchers (Ω)have also studied printed monopole antenna namelycircular disk printed monopole antenna [4] which is less 0.8 2.0 9.1 65 84.4fragile and planar in structure. In this paper, we will investigate UWB antenna, which 0.6 2.1 6.8 48 85is basically a printed microstrip antenna with etchedground plane. First we will investigate in depth thecircular disk printed monopole antenna as shown Fig. 0.3 2.1 12.8 50 861(a) and modify its structure by etching out some portionof it as shown in Fig. 3(a) for UWB applications. The For different values of g, the antenna impedance,second UWB antenna has slightly less BW than the bandwidth (flow is the lower start frequency of the antennaprevious one but it has higher efficiency and reduced BW, fhigh is the higher end frequency of the antenna BWsize. We have used conventional rectangular microstrip and antenna BW is considered for those frequency rangeline as feed line for printed UWB antennas which are where the s11 is below -10dB) and radiation efficiency areproperly matched to the antenna impedance. In future we tabulated. Here the gap (g) between the circular patch andwill also investigate other broadband matching the ground plane below is the most crucial parameter fortechniques to further improve the UWB performance of getting a broad BW. The other two importantthe printed monopole antennas. Zeland IE3D simulation considerations are proper impedance matching in order tosoftware [7] has been employed for obtaining the get the antenna impedance equal to 50 Ω and maximizesimulation results. the antenna radiation efficiency. As we can see from Table I, as the gap g decreases, flow is almost constant but 5© 2010 ACEEEDOI: 01.ijcom.01.01.02
  • 2. ACEEE International Journal on Communication, Vol 1, No. 1, Jan 2010the fhigh increases and there is evident increase in the BW.The efficiency of the antenna also slightly increases.Other than this, we have also seen that the ground planesize especially the width of the ground plane is also an Real partimportant factor affecting the antenna impedance andconsequently the BW. Wider ground plane means longerinput microstrip line and higher inductance and it reducesthe antenna fundamental resonant frequency andharmonic frequencies. Note the UWB performance of themonopole antenna is due to many closely resonatingfundamental and harmonic frequencies. The first Imaginary partresonant frequency of the monopole antenna isdetermined by the diameter of the circular disc. It Frequency (GHz)behaves like a quarter wave monopole antenna. (c) The E-plane and H-plane radiation patterns of the Figure 1. (a) Geometry (b) s11 versus frequency plot (BW is fromcircular disc UWB monopole antenna at 3.1, 7.2 and 10.6 2.1GHz to 12.4 GHz) (c) Antenna impedance versus frequency ofGHz are shown in Fig. 2(a)-2(f). It can be observed that circular disc UWB monopole antennathe E-plane radiation pattern is in the shape of 8 at 3.1GHz and it is in distorted 8 shapes at the higherfrequencies. It has maximum directivity at -150 and - 1800at 3.1GHz and at the frequency 7.2 GHz it has been tiltedto 100 and -1750. The H-plane radiation pattern on theother hand is purely omni-directional pattern at 3.1GHzand as frequency increases it is slightly distorted. (a) (a) (b) (b) 6© 2010 ACEEEDOI: 01.ijcom.01.01.02
  • 3. ACEEE International Journal on Communication, Vol 1, No. 1, Jan 2010 (c) (f) Figure 2. Circular disc UWB monopole antenna: E-plane radiation patterns at (a) 3.1 GHz, (b) 7.2 GHz, (c) 10.6 GHz and H-plane radiation patterns at (d) 3.1 GHz, (e) 7.2 GHz, (f) 10.6 GHz B. Modified Circular Disc UWB-Monopole Antenna This modified UWB monopole antenna is designed directly from the circular disc UWB-Monopole antenna with some modifications in the patch shape as shown in Fig. 3(a). We have used the same FR4 substrate with 4.4 relative permittivity and 1.6 mm thickness. The real part of antenna impedance is exactly 50 Ω at 7.2GHz and 11.4 GHz when the imaginary part of antenna impedance crosses zero. The final optimal dimensions of the UWB- monopole antenna are: Dimensions of Patch: W = 25.0mm and L = 23.0 mm. Dimensions of Substrate:W = 50.0 mm and L = 60.0 mm Dimensions of Ground: W = 50.0 mm and L = 25.7mm Microstrip line: W=2.6mm and L=26.0mm (d) “g” is gap between the ground plane and patch TABLE II: ANTENNA PARAMATERS FOR FEED GAP=0.3MM g flow fhigh Antenna η (mm) (GHz) (GHz) Impedance (%) (Ω) 0.3 2.3 11.3 50 90 After doing an extensive simulation study, we have fixed the dimensions of UWB monopole antenna and the value of “g” as 0.3mm. The antenna impedance, flow, fhigh and radiation efficiency are tabulated in Table II. Note that modified circular disc UWB monopole antenna is more compact than the circular disc UWB monopole antenna. It has a slightly better efficiency although the antenna BW is reduced it is still much broader than UWB BW of 3.1 GHz to 10.6Hz. As far as the E-plane and H- plane radiation patterns they are quite similar to the previous antenna throughout the frequency regions which we have not shown here for paper space limitations. (e) 7© 2010 ACEEEDOI: 01.ijcom.01.01.02
  • 4. ACEEE International Journal on Communication, Vol 1, No. 1, Jan 2010 III. CONCLUSION In this paper, we have investigated printed UWB monopole antennas, which is basically a printed microstrip antenna with the etched ground plane. Printed UWB monopole antennas are less fragile, planar and can be integrated with the integrated circuits unlike previous monopole antennas which have non-planar or protruded structures above the ground plane. In particular, we have (a) simulated two types of UWB monopole antennas namely circular and modified circular disk printed monopole antennas. The second antenna is compact and has higher efficiency whereas the first antenna has slightly wider BW. The E-plane radiation of both the printed monopole antennas is in the form of 8 shapes and it is slightlyS11 (dB) distorted at higher frequencies. The H-plane radiation pattern has omni-directional patterns which also become distorted at the higher frequencies of the BW. It has been observed that such monopole antennas are suitable for UWB operations from the IE3D simulation results. REFERENCES Frequency (GHz) [1] H. Schantz, The Art and Science of Ultra wideband (b) Antennas, Artech House Inc., 2005. [2] G. R. Aiello and G. D. Rogerson, “Ultra-wideband Wireless Systems," IEEE Microwave Magazine, June, 2003, pp. 36-47. Antenna Impedance [3] B. Allen, M. Dohler, E. E. Okon, W. Q. Malik, A. K. Brown and D. J. Edwards, Ultra-Wideband Antennas and Real part Propagation for Communications, Radar and Imaging, John Wiley & Sons, 2007. [4] J. Liang, C. Chiau, X. Chen and J. Yu, “Study of a circular disc monopole antennas for ultra wideband applications,” 2004 International Symposium on Antennas and Imaginary part Propagation, 17-21 August, 2004. [5] N. P. Agrawall, G. Kumar, and K. P. Ray, “Wide-Band Planar Monopole Antennas," IEEE Transactions on Antennas and Propagation, vol. 46, no. 2, February 1998, pp. 294-295. Frequency (GHz) [6] M. Hammoud, P. Poey and F. Colombel, “Matching the Input Impedance of a Broadband Disc Monopole," (c) Electronics Letters, vol. 29, no. 4, 18th February 1993, pp. Figure 3. (a) Geometry (b) s11 versus frequency plot (BW is from 406-407. 2.3GHz to 11.3 GHz) (c) Antenna impedance versus frequency of [7] IE3D version 10.2, Zeland Corp., Freemont, CA, modified circular disc UWB monopole antenna USA. 8© 2010 ACEEEDOI: 01.ijcom.01.01.02