October 2013 | |Wayne Turner ,Sukhvinder Malik, Rahul
Atri , Preet Kanwar Rekhi

White Paper

Fundametals of Cellular
Ante...
An antenna consists of an arrangement of metallic conductor
("elements"), electrically connected (often through a transmis...
3. Relation B/w Wavelength, Frequency and Dipole
Length
The length of antenna dipole is dependent on frequency of operatio...
5. Wave propagation
Wave propagation is any of the ways in which waves travel.
For electromagnetic waves, propagation may ...
7. Antenna Radiation pattern
The radiation pattern of an antenna is a plot of the relative field
strength of the radio wav...
8. Antenna Gain and Antenna Beam Calculation
Gain is a parameter which measures the degree of directivity of the
antenna's...
Following figure show the vertical arrangement of dipole
beam width and respective gain

Aa

Accordingly also in the horiz...
Calculation of the Gain and Beam width for an antenna:
An Antenna is in below figure in which dipoles are arranged in
vert...
9. VSWR for an Antenna
For a radio transmitter or receiver to deliver power to
an antenna, the impedance of the radio and ...






Standard values for mobile communication networks
VSWR < 1.5
Return loss < 14 dB
Mismatch loss :The loss which i...
This figure shows the example of ”Beam Squint” . As per
specification requirement the beam squint should be minimum.
Secto...
Front to Back Ratio (F/B)
 FBR is the ratio of Max. Directivity of an antenna to its
directivity in opposite direction.
...
11. Mechanical and Electrical Down Tilt
In any Radio network Following are the possible solutions to reduce
the coverage t...
Mechanical Down lint and its impact on antenna Pattern

Each colour shows the different angle of mechanical downtilt. We c...
If we closely see both the down tilting we will find that electrical down
tilting is more uniform than the mechanical down...
• Even though the mechanical tilted antenna’s horizontal pattern cut
look acceptable at smaller value of tilt, a subtle di...
Choice of Omni Antenna






Omni-Antenna: 360 degree beam width in horizontal plane
Gain of the antenna is only depen...
Beam-forming Antenna
Beam forming is a signal processing technique used in sensor arrays for
directional signal transmissi...
Active antenna System
An active antenna is an antenna that contains active electronic components
These active elements are...
13. Antenna integration with the base station with
generations
The way in which integration of antenna is done with base s...
Authors

14. References
1.
2.
3.
4.
5.

Wikipedia.com
www.3gpp.org
www.commscope.com/docs/active_antenna_systems
www.anten...
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Fundamentals of cellular antenna creating magic in the air

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In our daily life we see so many antennas everywhere, from simple radio transreceiver to big tower antennas and DTH antennas. Antenna is a magical element in the field of communication. Nobody can dream of wireless communication without the use of antennas. It’s the antenna which creates the magic in the air and makes wireless communication possible.

In this paper authors will discuss about the cellular antennas. They will concentrate mainly on fundamentals of antenna, relationship between frequency, wavelength and dipole wave propagation and parameters of antenna like Gain, VSWR, SFR and FBR etc.

Authors also discuss about types of down tilt, generic requirements of antennas, selection of antennas and beam forming and active antenna systems.

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Fundamentals of cellular antenna creating magic in the air

  1. 1. October 2013 | |Wayne Turner ,Sukhvinder Malik, Rahul Atri , Preet Kanwar Rekhi White Paper Fundametals of Cellular Antenna : Creating Magic in Air 1. Introduction In our daily life we see so many antennas everywhere, from simple radio transreceiver to big tower antennas and DTH antennas. Antenna is a magical element in the field of communication. Nobody can dream of wireless communication without the use of antennas. It’s the antenna which creates the magic in the air and makes wireless communication possible. In this paper authors will discuss about the cellular antennas. They will concentrate mainly on fundamentals of antenna, relationship between frequency, wavelength and dipole wave propagation and parameters of antenna like Gain, VSWR, SFR and FBR etc. Authors also discuss about types of down tilt, generic requirements of antennas, selection of antennas and beam forming and active antenna systems. 2. What is an antenna An antenna is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. An antenna is the converter between two kinds of electromagnetic waves: cable bounded wave’s ⇔ free space wave Contents 1. Introduction 2. What is an antenna 3. Relation Between Wavelength, Frequency and Dipole Length 4. Electric and Magnetic Field on Dipole 5. Wave propagation 6. Antenna Polarization 7. Antenna Radiation pattern 8. Antenna Gain and Antenna Beam Calculation 9. VSWR for an Antenna 10. Other Antenna Parameters 11. Mechanical and Electrical Down Tilt 12. Antenna Generic Requirement 13. Antenna Integration with the base station with generations 14. References
  2. 2. An antenna consists of an arrangement of metallic conductor ("elements"), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields, when created in the proper proportions, radiate away from the antenna into space as a moving transverse electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna. Antennas may also include reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. Antenna    Antennas can be designed to transmit or receive radio waves in all directions equally (omnidirectional antennas), or transmit them in a beam in a particular direction, and receive from that one direction only Antenna Consist of metallic conductor Antennas are designed to transmite or receive the wave Antenna is a quad pole device like amplifier and filter All RF components can be classified into two types:   Dual-pole (one termination) example for a dual-pole device: 50 ohm load Quad pole (two terminations) devices examples for a quadpole device: amplifier, filter. The antenna is a quad-pole device with the second termination connected to free space waves.
  3. 3. 3. Relation B/w Wavelength, Frequency and Dipole Length The length of antenna dipole is dependent on frequency of operation. Frequency and dipole length are inversely proportional, if the frequency is low then length of antenna will be high and if frequency is high the length of dipole antenna is less. Below figure shows the relationship between antenna and frequency Relation between frequency and wave length: λ = C/ f λ (m) = 300/ f [MHz] Example: f =935 MHz ⇒ λ = 0.32 m ⇒ dipole length (λ /2) ~160 mm f =1800 MHz ⇒ λ = 0.167 m ⇒ dipole length (λ /2) ~ 83 mm f =2100 MHz ⇒ λ = 0.142 m ⇒ dipole length (λ /2) ~ 71 mm f =2300 MHz ⇒ λ = 0.130 m ⇒ dipole length (λ /2) ~ 65 mm Both 900 MHz and 1800 MHz band are used by GSM technology, 2100 MHz is used by UMTS 3G technology and 2300 MHz is used for Broadband Wireless Access (BWA) technology like WiMAX and LTE. From above examples, we can see that as the frequency is increasing the length of dipole is decreasing 4. Electric and Magnetic Field on Dipole As we know that Antenna converts electrical energy into electromagnetic energy. When this electrical signal is applied the dipole antenna maximum voltage appears between the ends of the dipole, the voltage results in the electrical field (E) lines which occurs between these two charge centres. The current on the dipole causes a magnetically field (H) with an opposite amplitude distribution (max. at the feeding point, min. at the dipole ends) Wavelength, Frequency and Dipole      Wavelength λ (m) = 300/ f [MHz] Dipole Length= λ /2 As the frequency is increasing the length of dipole is decreasing voltage results in the electrical field (E) Current on the dipole causes a magnetically field (H)
  4. 4. 5. Wave propagation Wave propagation is any of the ways in which waves travel. For electromagnetic waves, propagation may occur in a vacuum as well as in a material medium. Other wave types cannot propagate through a vacuum and need a transmission medium to exist. The electrical signal converted into electromagnetic wave and transmitted over air. The wave now propagates in the air by conversion from electrical to magnetic energy and vice versa as shown in below figure. Wave Propagation and Antenna Polarization   The wave now propagates in the air by conversion from electrical to magnetic energy and vice versa The polarization of an antenna is the orientation of the electric field (Eplane) of the radio wave with respect to the Earth's surface 6. Antenna Polarization The polarization of an antenna is the orientation of the electric field (Eplane) of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation. There are different type of polarization of antenna and most common polarization and dipole orientation of dipole is given below:    4 Dipole orientation vertical : Vertical polarization ⇒ mainly used for mobile communication Dipole orientation Horizontal : Horizontal polarization ⇒ mainly used for broadcasting Dipole orientation +/-45° slanted : Cross polarization ⇒ used for polarization diversity with digital cellular networks
  5. 5. 7. Antenna Radiation pattern The radiation pattern of an antenna is a plot of the relative field strength of the radio waves emitted by the antenna at different angles. It is typically represented by a three dimensional graph, or polar plots of the horizontal and vertical cross sections. Antennas 3-dimensional pattern can be described by a vertical and horizontal cut  Vertical polarization : Horizontal pattern = H-plane (magnetic field) Vertical pattern = E-plane (electric field)  Half power beam width opening angle of the beam determined by the half power points (reduction by 3 dB) Aa Antenna Radiation Pattern  Antenna Have a 3 dimensional Pattern - Horizontal Pattern - Vertical Pattern - Half power beam width The pattern of an ideal isotropic antenna, which radiates equally in all directions, would look like a sphere. Many non - directional antennas, such as monopoles and dipoles, emit equal power in all horizontal directions, with the power dropping off at higher and lower angles; this is called an omnidirectional pattern and when plotted looks like a torus or donut. The radiation of many antennas shows a pattern of maxima or "lobes" at various angles, separated by "nulls", angles where the radiation falls to zero. This is because the radio waves emitted by different parts of the antenna typically interfere, causing maxima at angles where the radio waves arrive at distant points in phase, and zero radiation at other angles where the radio waves arrive out of phase. In a directional antenna designed to project radio waves in a particular direction, the lobe in that direction is designed larger than the others and is called the "main lobe". The other lobes usually represent unwanted radiation and are called "side lobes". The axis through the main lobe is called the "principal axis" or "bore sight axis".
  6. 6. 8. Antenna Gain and Antenna Beam Calculation Gain is a parameter which measures the degree of directivity of the antenna's radiation pattern. A high-gain antenna will preferentially radiate in a particular direction. The gain of an antenna is a passive phenomenon - power is not added by the antenna, but simply redistributed to provide more radiated power in a certain direction than would be transmitted by an isotropic antenna. The gain is measured in dBi and dBd dBi is gain with reference to Isotropic Antenna dBd is gain with reference to Dipole Antenna In practice, the half-wave dipole is taken as a reference instead of the isotropic radiator. The gain is then given in dBd (decibels over dipole): There is a relation between dBd and dBi given below Antenna Gain dBi= dBd + 2.15 . The gain is measured in dBi and dBd  dBi is gain with reference to Isotropic Antenna  dBd is gain with reference to Dipole Antenna The relation between dBd and dBi dBi= dBd + 2.15 An antenna designer must take into account the application for the antenna when determining the gain.   High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully in a particular direction. Low-gain antennas have shorter range, but the orientation of the antenna is relatively inconsequential. Antenna Gain and Dipole Arrangement: To concentrate the radiated power into the area around the horizon, half wave dipoles are arranged vertically and combined in phase With every doubling of the dipoles number   The half power beam width approx. halves The gain increases by 3 dB in the main direction
  7. 7. Following figure show the vertical arrangement of dipole beam width and respective gain Aa Accordingly also in the horizontal plane a beam can be created with each halving of the beam width the gain is increased by 3 dB (the shown patterns are theoretically) The resulting gain of an antenna is the sum of the “vertical” and “horizontal” gain
  8. 8. Calculation of the Gain and Beam width for an antenna: An Antenna is in below figure in which dipoles are arranged in vertical polarization. Following are the step to calculate the gain of antenna. The shown Antenna has 8 Dipole in vertical direction which contributes 9dB. 3 dB due to Back plane of antenna and further 3 dB to one more column of 8 dipole in Horizontal plane. 9 dB gain due to 8 no of dipoles in vertical direction 3 dB gain due to Backplane 3 dB gain due to addition of one more column of eight dipoles in horizontal plane Total gain =9 +3 +3 = 15 dB with reference to dipole antenna Now if we want to convert it with reference to the Isotropic antenna then we have to add 2.15 dB in gain of dipole Then gain of antenna in dBi = 15 +2.15dB =17.15 dB In the same manner we can find out the beam width of antenna. A dipole have 78 Degree beam in vertical plane and doubling the dipole makes beam width half. For 2 Dipole in vertical make vertical beam width to 32 Degree and further 8 Dipole make beam width as 7 degree. Some of the beam power is wasted in the minor lobe while designing the antenna. Same with Horizontal beam width, the two columns make horizontal beam width as 90 degree. Then the specification of such antenna becomes as below: 8 Horizontal beam width = 90 Degree Vertical beam Width = 7 Degree Gain of antenna = 17.15 dBi
  9. 9. 9. VSWR for an Antenna For a radio transmitter or receiver to deliver power to an antenna, the impedance of the radio and transmission line must be well matched to the antenna's impedance. The parameter VSWR is a measure that numerically describes how well the antenna is impedance matched to the radio or transmission line it is connected to. The Antennas are screened (pass/fail criteria) based on VSWR specifications (VSWR specs). For VSWR Example we can assume a generator will generate a frequency and send it to a termination. The termination may not accept the entire input power (green line), and therefore will reflect some of the input power (red line) back to the generator. VSWR   The forward running signal together with the return running signal create a standing wave (VSWR = voltage standing wave ratio)   VSWR (s) = U max. / U min. (range 1 to ∞) Return loss attenuation:Rerun Loss [dB] = − {20 log*Ur − 20 log*Uv} The forward running signal together with the return running signal create a standing wave VSWR (s) = U max. / U min. (range 1 to ∞) Return loss attenuation Rerun Loss [dB] = − {20 log*Ur − 20 log*Uv} Standard values for mobile communication networks • VSWR < 1.5 • Return loss < 14 dB
  10. 10.     Standard values for mobile communication networks VSWR < 1.5 Return loss < 14 dB Mismatch loss :The loss which is effecting the system performance due to the reflected/returned power VSWR 1.5 1.3 1.2 Mismatch loss (dB) 0.18 0.08 0.04 For an optimized system performance, all components have to be matched and Professional applications use a nominal impedance of 50 Ohms Exact value only for one frequency; over the operating band deviations from 50 Ohms are specified by the VSWR Other Antenna Parameters      There are some other important parameters of antenna like Beam Squint, Sector Power Ratio and Front to Back Ratio Beam squint is defined as the difference between the mechanical bore site and the electrical bore site of an antenna. Sector Power Ratio (SPR) is another measure of an antenna’s ability to minimize interference FBR is the ratio of Max. Directivity of an antenna to its directivity in opposite direction Cross polarization ratio is a difference in dB between the peak of the co-polarized main beam and the max. 10. Other Antenna Parameters There are some other important parameters of antenna like Beam Squint, Sector Power Ratio and Front to Back Ratio (F/B). We will discuss about them in brief and significance of the parameters. Beam Squint  Beam squint is defined as the difference between the mechanical bore site and the electrical bore site of an antenna.  The mechanical bore site is defined as being perpendicular to the antenna’s back tray  Electrical bore site is defined as the mid-point of the 3 dB beam width.
  11. 11. This figure shows the example of ”Beam Squint” . As per specification requirement the beam squint should be minimum. Sector Power Ratio  Sector Power Ratio (SPR) is another measure of an antenna’s ability to minimize interference.  SPR compares the RF power radiated outside the sector to the RF power radiated and retained within the sector. It is expressed in percentage and SPRs as low 3% – 4%,
  12. 12. Front to Back Ratio (F/B)  FBR is the ratio of Max. Directivity of an antenna to its directivity in opposite direction.  Ratio of signal strength transmitted in a forward direction to that transmitted in a backward direction  A front-to-back ratio is usually expressed in dB  FBR of antenna‘s ability to generate or neglect the interference through its back lobe.  Front-to-back ratio (F/B) compares gain at bore site to gain at point 180º behind bore site  It is often expressed as the F/B ratio over some angle around the 180º point (ie. 180 ±30º) Cross Polarization Ratio (CPR)  Cross polarization ratio is a difference in dB between the peak of the co-polarized main beam and the max. Cross polarized signal over an angle measured with in defined region.  Cross-Polarization Ratio (CPR) is a measure of the decorrelation of the two polarizations used in a X-Pol antenna one at +45º and the other at – 45º.  The better the CPR, better the performance of the polarization Diversity.
  13. 13. 11. Mechanical and Electrical Down Tilt In any Radio network Following are the possible solutions to reduce the coverage to mitigate the unwanted interference: • • • • Lowering the Antenna height Replacing the Antenna with lower gain of Antenna Down tilting the elevation beam Down-tilting of elevation beam is the most cost effective and predominantly used techniques even in 2G (GSM/CDMA) technologies. There are two types of Down Tilts are possible: • • Electrical: By changing the phase in the individual antenna dipoles - Fixed Tilt - Mechanical Electrical Tilt (MET) - Remote electrical Tilt (RET) Mechanical Tilt: Simply tilting the Antenna mechanically Mechanical Downtilt  A mechanical down tilt increases the upper distance to the mast and makes the antenna pointing down  The requested down tilt angle is achieved only in main direction  Effective down tilt varies across the azimuth Mechanical Downtilt (Effect on Horizontal Pattern)  Effect on the horizontal pattern at the horizon : reduction of the field strength in main direction without any change +/- 90° to it results in deformation of the horizontal pattern  This effect of changing half power beam width can hardly be considered in the network planning and reduces the prediction accuracy. Mechanical and Electrical Down Tilt Two Types of tilt • Electrical: By changing the phase in the individual antenna dipoles - Fixed Tilt - Mechanical Electrical Tilt (MET) - Remote electrical Tilt (RET) • Mechanical Tilt: Simply tilting the Antenna mechanically
  14. 14. Mechanical Down lint and its impact on antenna Pattern Each colour shows the different angle of mechanical downtilt. We can see for 10 degree downtilt antenna horizontal pattern total shrink Electrical Downtilt More elegant in the electrical down tilt with the antenna remaining upright; instead of equal phases on the dipoles, particular phase distributions are selected by varying the cable lengths to the dipoles. In Electrical Downtilt the following is done :    The fixed phase distribution applies to all azimuth directions ⇒ electrical down tilt angle is constant The shape of the horizontal pattern remains constant Accurate network planning is assured
  15. 15. If we closely see both the down tilting we will find that electrical down tilting is more uniform than the mechanical down tilt. Electrical down tilt equally attenuate the pattern in on the directions by controlling the feed current while in mechanical downtilt basically tilt attenuate the main 0 degree attenuation beam by physically down tilting the antenna which further increase the SPR (Sector Power ratio) The Electrical downtilt have following flavours  Fixed Electrical Tilt (for e.g., 0°, 2°, 4° etc. ):  Mechanical Electrical Tilt (MET): - Electrical tilt of antenna can be change by just changing the knob mechanically - It can change the tilt in some degree (1 or 2°) of steps.  Remote Electrical Tilt (RET): - Electrical tilt can be controlled remotely through EMS/NMS of a network. - This is a great feature as RF optimizations can be done without physically going to the cell site. Electrical Tilt vs. Mechanical Tilt • Small value of mechanical tilt, the pattern seems acceptable but with greater amount of down tilt, the pattern takes on a “peanut” Shaped look. This is undesirable as the purpose of down tilting is to reduce the coverage in all directions to reduce the interference.
  16. 16. • Even though the mechanical tilted antenna’s horizontal pattern cut look acceptable at smaller value of tilt, a subtle difference is taking place ----commonly referred to as ‘pattern booming’. In essence 3 dB beam width getting larger. Hence it increases the sector overlap area. • In the case of electrical tilt, the Gain is reduced in all directions. Sector overlap area will not increase. Therefore electrical tilt is always better solution than the mechanical tilt. • In the past, the thumb rule for maximum mechanical tilt was = ½ of the vertical beam width of Antenna. This cannot be used where the electrical tilt of Antenna is also used. Antenna generic Requirement Interface requirements are:  Antenna should have 50 ohm RF interface for prefect impedance matching  Antenna should have RF interface of 7/16 DIN Type connector  It should be bottom fed type to ease access  It should have AISG interface for RFT feature for remote electrical tilt Electrical requirements are:  Operating Frequency, Peak Power support, VSWR, Polarization, FBR, SPR, Efficiency, RET capability, HBW, VBW and Gain related requirements can be considered under electrical requirement. Environmental requirement  Operating Temp. Range, Humidity Range, IP65 for dust and water protection, survive wind loading speed, Mechanical strength and resistance to Corrosion can be considered under Environmental requirements 12. Antenna Generic Requirement When we are selecting an antenna have to make some generic requirements. Broadly these requirements are related to Interface, Electrical requirement and Environmental requirement Interface requirements are:  Antenna should have 50 ohm RF interface for prefect impedance matching  Antenna should have RF interface of 7/16 DIN Type connector  It should be bottom fed type to ease access  It should have AISG interface for RFT feature for remote electrical tilt Electrical requirements are:  Operating Frequency, Peak Power support, VSWR, Polarization, FBR, SPR, Efficiency, RET capability, HBW, VBW and Gain related requirements can be considered under electrical requirement. Environmental requirement  Operating Temp. Range, Humidity Range, IP65 for dust and water protection, survive wind loading speed, Mechanical strength and resistance to Corrosion can be considered under Environmental requirements 13. Selection of antenna
  17. 17. Choice of Omni Antenna     Omni-Antenna: 360 degree beam width in horizontal plane Gain of the antenna is only depends upon the vertical beam width. Direct trade-off between Gain and vertical beam width For 7° vertical beam width, gain of the antenna will be 9 dB (due to 8 vertical elements) + 2.15 dB (dipole gain)= ~ 11 dBi Application: - In Rural Area where capacity of a BTS is not required - For in building coverage with Pico and femto BTS. Choice of Sectored Antenna Sectored Antenna: (Directional Antenna) Will have directivity in horizontal and vertical plane both, Antenna gain is depends on horizontal & vertical beam width as beam width decreases, Gain increases and vice a versa. Horizontal (Azimuth) beam width of Antenna requirement comes from the number of sectors in the bases station and deployment scenario. Vertical beam width requirement comes from the antenna placement height. For e.g. Antenna on 30 meter tower height required 7° vertical beam width.  Following sectored Antenna are generally available:  45° Horizontal Beam width  65° Horizontal Beam width  90° Horizontal Beam width  120° horizontal Beam width 45°Horizontal Beam width Antenna: Used for 4 sectors Base Station, Very less usage of such antenna because of more overlap area for 4 sector BTS configuration 65°Horizontal Beam width Antenna: Used for 3 sectors Base Station especially in Dense Urban, Urban & Sub-urban, Widely used Antenna. ~ 75% of total antennas are used of this type in any network. 90° Horizontal Beam width Antenna: Used for 3 sector Base Station especially in rural area 120° Horizontal Beam width Antenna: Used for 2 sectors Base Station, main application is of highway coverage Omni and Sectored antenna    Omni-Antenna have 360 degree beam width in horizontal plane Sectored Antenna have directivity in horizontal and vertical plane both sectored Antenna are generally available:  45° Horizontal Beam width  65° Horizontal Beam width  90° Horizontal Beam width  120° horizontal Beam width
  18. 18. Beam-forming Antenna Beam forming is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in a phased array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beam forming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. Adaptive Array Antennas are used for Beam-forming at base station. Array of elements are (vertical polarized) vertically placed at 0.5 λ apart to have correlated signal which are essential for beam-forming. The mini requirement for beam forming the antenna should be 4 port or more. Beam Forming Antenna • • Adaptive Array Antennas are used for Beam-forming Array of elements are vertical polarized or vertically placed at 0.5 λ apart to have correlated signal which are essential for beamforming The above picture shows 4 port and 8 port antenna in first two pictures which can be used for beam forming. To support 8 transceiver beam forming requires 8 antenna elements and if placement of element is vertically then the size of antenna becomes very large , so the alternative to achieved the same the placement of antenna element can be done slanted i.e. 45 degree which is also known as cross polarization. This will reduces the size & weight of Antenna compared to 8 separate column of vertical polarized Antenna in a single radome as shown in third picture. From the above pictures it can also be observed that the antenna elements are 0.5 λ apart from each other to achieve the correlated signals amongst the different chains .
  19. 19. Active antenna System An active antenna is an antenna that contains active electronic components These active elements are radio cards and amplifiers. In these type of Remote Radio Head functionality integrated in to antennas. Below shown picture is an example of active antenna. In this individual radio cards and amplifier are attached behind the individual dipole. Active Antenna Systems    The types of antenna are basically next new generation antennas where only need to connect CPRI/OBSAI interface from the baseband unit. An active antenna is an antenna that contains active electronic components These active elements are radio cards and amplifiers. In Active Antenna Remote Radio Head functionality integrated in to antennas.
  20. 20. 13. Antenna integration with the base station with generations The way in which integration of antenna is done with base station is changing continually with the generation. In 2G GSM/CDMA system where both baseband and radio was a single unit. The feeder cables from the radio of the base station are connected to the antenna. Sometimes Tower mounted amplifiers are also used to increase the coverage and to compensate the losses due to feeder cables. 3G WCDMA/ 4G LTE brings the concept of separate baseband and radio part. In this convention the radio comes closer to antenna and reduces the losses that were happening in 2G due to long RF feeder cable. The connection between baseband and radio introduced is CPRI/OBSAI based which is basically a fiber connection. Antenna Integration With basestation with generations    In 2 G/CDMA systems the feeder cables from the radio of the base station are connected to the antenna In 3 G the connection between baseband and radio introduced is CPRI/OBSAI based which is basically a fiber connection. The new coming technology which is active antenna system will totally eliminate use of RF feeder cable as the radio head becomes the part of antenna. The new coming technology which is active antenna system will totally eliminate use of RF feeder cable as the radio head becomes the part of antenna. The based band unit of base station is connected through CPRI/OBSAI fiber interface. This will eliminate the losses which were introduced by the RF feeder cables in present topologies.
  21. 21. Authors 14. References 1. 2. 3. 4. 5. Wikipedia.com www.3gpp.org www.commscope.com/docs/active_antenna_systems www.antenna-theory.com/ Antenna and Wave Propagation by KD Prasad Wanye Turner Sytem Design Eningeer Preet Rekhi LTE System Test Engineer Rahul Atri LTE System Test Engineer Sukhvinder Malik LTE System Test Engineer Disclaimer: Authors state that this whitepaper has been compiled meticulously and to the best of their knowledge as of the date of publication. The information contained herein the white paper is for information purposes only and is intended only to transfer knowledge about the respective topic and not to earn any kind of profit. Every effort has been made to ensure the information in this paper is accurate. Authors does not accept any responsibility or liability whatsoever for any error of fact, omission, interpretation or opinion that may be present, however it may have occurred

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