antennas-8 - smart antennas

7/27/2019 Antennas-8 - Smart Antennas

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Dr.-Ing. Getahun Mekuria

Department of Electrical and Computer Engineering (ECE)

Addis Ababa Institute of Technology (AAiT)

Addis Ababa University (AAU)

ECEG 6308

Analysis and Design of Antenna

Smart Antennas



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Non-Smart Antennas

Omni-directional Sectorized

• When omni-directional antennas are used at the base

station, the transmission/reception of each user's signal

becomes a source of interference to other users locatedin the same cell.

• An effective way to reduce this type of interference is to

split up the cell into multiple sectors and use sectorized

antennas.



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Non-Smart Antennas – Sectorized Antenna



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Non- Smart Antennas

• Sectorized antennas transmit and receive in a limitedportion of the cell, typically one-third of the circular area,

thereby reducing the overall interference in the system.



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Smart Antennas -Introduction

• A smart antenna is a Phased or Adaptive Array thatadjusts to the environment

• A smart antenna system combines multiple antenna

elements with a signal processing capability tooptimize its radiation and/or reception pattern

automatically in response to the signal environment.

• Smart Antennas are arrays of antenna elements that

change their antenna pattern dynamically to adjust to thenoise, interference in the channel and mitigate multipath

fading effects on the signal of interest.



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Smart Antennas –Advantages (Mobile Nets)

• Greater coverage area for each cell site• Better rejection of co-channel interference

• Reduced multipath interference / increased directionality

• Reduced delay spread as fewer scatterers are allowed

into the beam• Increased frequency reuse with fewer base stations

• Higher range in rural areas

• Improved building penetration

• Location information for emergency situations

• Increased data rates and overall system capacity• Reduction in dropped calls



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Smart Antennas –Advantages (Mobile Nets)

• Greater coverage area for each cell site• Extended Battery Life

• Better rejection of co-channel interference

• Reduced multipath interference / increased directionality

•

Reduced delay spread as fewer scatterers are allowedinto the beam

• Increased frequency reuse with fewer base stations

• Higher range in rural areas

• Improved building penetration

• Location information for emergency situations• Increased data rates and overall system capacity

• Reduction in dropped calls



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Smart Antennas –Types

• Switched Beaforming

•

Adaptive Beaforming



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Switched Beaforming (Phased Array, Multibeam):• Consists of either a number of fixed beams

with one beam turned on towards the desired

signal or a single beam (formed by phase

adjustment only) that is steered towards the

desired signal.



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Adaptive Beaforming:• An array of multiple antenna elements with the

received signals weighted and combined to

maximize the desired signal to interference and

noise (SINR) ratio. This means that the main

beam is put in the direction of the desired signal

while nulls are in the direction of the interference.



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Smart Antennas –Types Switched/Phased Array

Beamforming

Adaptive Beamforming



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SDMA (Spatial Division Multiple

Access) Beamformer



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Smart Antennas –Types – Pros and Cons

Switched Beam Forming Adaptive Beam FormingPros Simple to implement,

Low cost.

High capacity with

reduced interference,

Best suited for line of

sight environment

Cons Limited configuration

flexibility, There must be at

least one strong direct

component for DOA

estimation

Medium complexity, High

cost, There must be at

least one strong direct

component for DOA

estimation



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Smart Antennas –Geometries

(a) Linear array, (b) Circular Array, (C) 2D grid array, and (d) 3D grid array



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Smart Antennas – Architecture

Smart Antenna

Receiver system



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Smart Antennas – Architecture

Smart Antenna

Receiver system



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Smart Antennas – DOA Estimation Algorithms

Hardware Implementation of Smart Antennas



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Smart Antennas – DOA Estimation Algorithms

• MUSICMultiple Signal Classification

• ESPRIT

Estimation of Signal Parameter via Rotational

Invariant Technique

antennas-8 - smart antennas

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