smart antenna

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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 ??