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Smart Antennas
Presented by :-
Rajib Kumar Das
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Overview
Introduction
Types of Smart antennas
Smart antenna for vehicles
Part I
Part II
Beamforming algorithms
DoA algorithms
MSA implementation
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Smart Antenna
Smart antenna refers to a system of antenna array with smart signal processing algorithms that are used to identify spatial signal signature such as the DOA of the signal, and use it to calculate beam forming vectors, to track and locate the antenna beam on the mobile/target.
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SA Application
Radar Radio Astronomy Radio Telescopy Cellular System
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Non Smart antenna system
Limited BW available hence interference in systemOmni directional antennas used at the BS This is an interference limited system Solution : Sectorized antenna
Source http://www.altera.com/endmarket/wirelessantenna
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Smart antenna Technology
Concept of beam forming Reduces interferences in the system & increases capacity Each user signal is multiplied by complex weight thereby adjusting mag & phase of signal & beam is formedBeam forming is of two types
BS
Source http://www.altera.com/endmarket/wirelessantenna
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Switched beam
Beams are formed in pre determined direction BS switches between different beams based on Rx signal measurement.
Source http://www.smartanteenas.googlepages.com
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Adaptive beam forming
Beams are not formed in pre determined direction Real time processing BS forms narrow beam towards desired user Improves S/N ratio
Source http://www.altera.com/endmarket/wirelessantenna
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Types of SA
Adaptive array MIMO
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MIMO
Increased data handling capability Higher spectral efficiency No additional BW requirement
Source www.webopedia.com
Advantages
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Adaptive arrays antennas
Switched beam Parasitic array Digital beam forming array Diversity array Phased array
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Switched beam forming implementation
Implementation using power splitters & phase shifters Application: Radar, EW & satellite system
Source http://www.smartanteenas.googlepages.com
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Phased array antenna
Functional block diagram of phased array mounted on car
Source http://www.smartanteenas.googlepages.com
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Phased array antenna
Functional diagram of phased array antenna
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Digital beam forming array antenna
].
Source http://www.smartanteenas.googlepages.com
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Parasitic array antenna
Active element is surrounded by number of parasitic elements Switching of parasitic elements done by PIN diode 3 direction beam steering achieved
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SA application on vehicles with array antenna
Antennas are usually vertically mounted Requirement Omni directional pattern in azimuth plane
Cellular car radio antenna [1]
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Radiation properties as function of antenna location
Roof rim has rotational non symmetric environment Deviation of desired omni directional pattern Omni directional pattern could be achieved only at the center of roof
Radiation properties as a function of antenna loc on car[2]
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Array antenna on vehicles[1]
Multi element phased array technique Vertical dimension less than quarter wavelength is possible At BS individual BF for individual tracking & signal optimzation Conventional methods used at Mobile station Thus only one RX/TX front end is required
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3 element antenna with adjustable main beam direction[1]
Achievement: Adjustable directive main beam covering complete azimuth plane Reduction in side lobes Gain is 5 dB more than conventional antenna Further optimization possible by 4 elements
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Two element optimized antenna
2 element pattern optimized antenna [2]
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Diversity car antenna for cellular radio
Problem of multiple path propagation in channel Signal quality improves with number of elements
Signal quality with different antenna combination[1]
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Part II
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Why Smart Antennas ?
Enhance System performance Increases channel capacity Enhances Spectrum efficiency Range coverage Track multiple users
Reduce Interference Delay spread Multipath fading
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Why Smart Antennas ? (contd..)
Reduce system complexity
Reduce co channel interference Tx mode Rx mode
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Terminologies
Fading Mean path loss Slow fading
• Difficult to predict Fast fading
• Multipath propagation• Phase variations• Rayleigh distribution
Channel spread Doppler spread Angle spread Delay spread
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Switched Beam Vs Adaptive Array
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Block diagram of Smart Antenna
Source : [8]
Unwanted users
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Beamforming
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Beamforming Schemes Delay & sum
Unity response Disadvantage : Interference
Null steering Cancels plane wave from
known direction Handles strong interference Disadvantage : Multiple
interference
Digital Beamforming Higher sampling rates Capacity enhancement upto
200 %
Source : [4]
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Adaptive Beamforming Algorithms
Sample Matrix Inversion (SMI) Replaces covariance matrix of spatially sampled
signals by estimated value iteratively Least Mean Square (LMS)
Weights are subjected to constraints Constant Modulus Algorithm (CMA)
Assumes that interference causes amplitude fluctuation in o/p
Neural Network approach Applicable when ref sig is available Iteratively minimizes the MSE between ref sig and
modified array o/pSource : [5]
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DoA Algorithms
DFT and Maximum Entropy Method (MEM) Uses signal
subspace MUltiple SIgnal
Classification (MUSIC) Estimates DoA in
noise subspace More accurate
Source : [8]
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Smart Antenna Design Implementation
A planar array configuration: Dx = 54.562 mm,Dy = 54.747 mm, dx = 7.500 mm, dy = 7.500 mm,
xo = 0.794 mm, yo = 1.164 mm, W = 2.247 mm, L = 2.062 mm,t = 0.300mm, r = 11.7, = 0.04, f = 20GHz.
Source : [6]
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Radiation Pattern
E-plane
H-plane
Source : [6]
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Conclusion
Advantages accrued Applications
PL Adhoc networks High data rate : 3G
Applicable scheme for TDMA CDMA
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References[1] R Kronberger,H Lindermerier,J Hopf “Smart antenna applications on vehicles with low profile array antenna” Proc IEEE Vol 53 pp1-3 September 2003.
[2] R Kronberger,H Lindermerier,J Hopf “Design method for antenna array on cars” Proc IEEE Vol 101 pp11-15 September 2003.
[3] http://www.smartanteenas.googlepages.com
[4] http://www.iec.org
[5]Michael Chryssomallis “Smart antennas” IEEE antenna and propagation magazine” Vol 42 No 3 pp 129-138, June 2000.
[6]Salvatore Bellofiore, Constantine,Jeffry and Andreas “ Smart antenna systems for mobile communication networks “IEEE Antenna’s and propagation magazine” Vol 44 No 3 pp 145-154, June 2002.
[7] AJ Paulraj,D Gesbert “Smart antennas for mobile communication” IEEE Antenna’s and propagation magazine Vol 57 No 5 pp 1-14, June 2000.
[8]JM Samhan,RM Shubair and MA Alquadi “Design and implementation of an adaptive smart antenna” Proc IEEE Vol 57 pp6-7 September 2006.
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Questions ??