ADAPTIVE ARRAY ANTENNA

1
ADAPTIVE ARRAY ANTENNA

• BY
• ANURAG SRIVASTAVA (07307306)
• SANJEEV GUPTA (07307408)

2
POTLI BABA KI !

• Introduction.
• Evolution.
• Categorization.
• Switched Beam Antenna.
• Adaptive Array Systems.
• Algorithm.
• Types.
• Market Scenario.
• Conclusion.

3
INTRODUCTION

• The theory behind intelligent antennas is not
  new, similar techniques were already used in
  military radar and satellite tracking systems.
• Cost barrier was hindrance.
• In the last couple of years the field of smart
  antenna technology is rapidly becoming one of the
  most promising areas of mobile communications,
  especially with development in DSPs and
  innovative algorithms.

4

• How can an antenna be made more intelligent?
• Instead of having one element have many!
• The antenna can become an antenna system that
  can be designed to shift signals before
  transmission at each of the successive elements
  so that the antenna has a composite effect.

5
EVOLUTION

• Antenna developed in the following order of
  increasing benefits and intelligence.
• Sectorised systems.
• Diversity systems.

6
EVOLUTION

• Sectorized Systems
• Sectorized antenna systems take a traditional
  cellular area and subdivide it into sectors that
  are covered using directional antennas looking
  out from the same base station location.
• Each sector is treated as a different cell, the
  range of which is greater than in the omni
  directional case.
• Sector antennas increase the possible reuse of a
  frequency channel by reducing potential
  interference inside the original cell.

7
EVOLUTION
Fig 1. Sectorized Antenna and Coverage Patterns
8
EVOLUTION

• Diversity Systems
• The diversity system incorporates two or more
  antenna elements at the base station.
• Use correlation networks.
• Thus their slight physical separation (or space
  diversity) is used to improve reception by
  counteracting the negative effects of multi path
  reception.

9
EVOLUTION

• Diversity offers an improvement in the effective
  strength of the received signal by using one of
  the following two methods
• Switched diversity
• At least one antenna will be in a favorable
  location at a given moment
• The system continually switches between antennas
  so as always to use the element with the largest
  output. While reducing the negative effects of
  signal fading
• They do not increase gain since only one antenna
  is used at a time.
• Diversity combining
• This approach corrects the phase error in two
  multi path signals and
• Effectively combines the power of both signals to
  produce gain..

10
APPROACH

• To generate an adaptively adjustable antenna
  beam.
• Maximizing the antenna gain in the desired
  direction.
• Simultaneously, placing minimal radiation pattern
  in the directions of the interferers.

11
SYSTEM CATEGORIZATION

• Smart array systems are broadly categorized as
• Switched Beam systems.
• Adaptive Array systems.

12
SWITCHED BEAM SYSTEM

• A switched-beam antenna system consists of
  several highly directive, fixed, pre-defined
  beams.
• Beams are formed to have high sensitivity in
  particular fixed directions or sectors.
• Antenna systems detect signal strength, choose
  from one of several predetermined, fixed beams,
  and switch from one beam to another as the user
  moves throughout the sector.

13
SWITCHED BEAM SYSTEM
top view(horizontal)
4
5
6
3
7
2
1
8
user
9
16
10
15
11
14
12
13
Switched Array (predetermined)
14
SWITCHED BEAM LIMITATIONS

• Incapacity for providing protection from
  multi-path components arriving near the desired
  signal. i.e. cannot discriminate between
  multipaths at close AoA.
• Cannot take advantage of path diversity by
  combining coherent multi-path components.

Desired signal
Interference
Interference
15
ADAPTIVE ARRAY SYSTEM

• Use sophisticated signal-processing algorithms
  to
• Distinguish between desired signals, multi-path
  and interfering signals.
• Update its beam pattern.
• By combining adaptive digital signal processing
  with spatial processing techniques, adaptive
  array systems can achieve greater performance
  improvements than attainable using switched beam
  systems.

16
ADAPTIVE ARRAY SYSTEM
Fig 3 Fully adaptive spatial processing,
supporting two users on the same
conventional channel simultaneously in the same
cell.
17
ADAPTIVE ARRAY SYSTEM
Fig 2 Performance evaluation
18
ADAPTIVE ARRAY SYSTEM

• Two major considerations
• Choice of Adaptive Antenna Array
• Phased Array
• Digital Beam formation array
• Parasitic Array
• Choice of Adaptive DSP Algorithm

19
(No Transcript)
20
IMPLEMENTATION ADSP ALGORITHM

• N elements of array receive signals from
  M sources
• Umn Amn Smn ejwt
  -------- (1)
• Where Amn is signal strength and Smn is
  phase lag .
• Total signal received at an element from
  M sources
• Un S Amn Smn ejwt
  -------- (2)
• Multiply (2) by Weighting Coefficient
  w and summing
• y S Un wn ------- (3) , summed
  over n 0 to N-1
• In direction towards source m output
  is
• ym Am ejwt S Smn wn -------
  (4) .

21

• From (4) gm S Smn wn , is gain of
  antenna in direction of source m.
• In matrix form for M N, gain can be
  written as
• Re-arranging this we will get W matrix. By
  calculating W, radiation pattern in a particular
  direction can be known using (4).

22

• Radiation pattern when N 15 and d/? 1/3

23
Implementation of Adaptive Antenna Array

• PHASED ARRAY
• Relative phases of the elements is of respective
  signals feeding the antennas are varied.
• The beam forming network consists of power
  dividers, couplers, switches, phase shifters,
  biasing networks.
• Circularly polarized (CP) patch antennas as array
  elements.

24

• Extensively used in Radar, Military and
  Satellite Communication.
• Advantages Scanning and weight.
• Communication Research laboratory and NASDA
  developed an scanning spot beam active phased
  array antenna for the experimental high data rate
  (Gigabit) communication satellite.
• In Australia, a twelve-element land mobile
  terminal phased array antenna is designed for
  keeping constant tracking of the MobilesatTM
  satellite while the terminal is moving

25

• Phased Array The functional block diagram of the
  mobile antenna is depicted which is tracking a
  satellite.

26
Cont..
.
27
PARASITIC ARRAY

• The parasitic array is formed with one active and
  several surrounding monopoles on the ground
  plane.
• Changing reactance of the parasitic elements
  alters the radiation of each element.
• The loads on the parasitic elements are carried
  out by terminating a transmission line by a
  variable reflection phase shifter.
• Lower complexity and power consumption.

28
PARASITIC ARRAY

• Configuration of a seven-element ESPAR antenna.

29
Market Scenario

• Navini Networks is combining MIMO and beamforming
  in its adaptive antenna system arrays and base
  station
• CalAmp's smart antenna development has resulted
  in beamforming technology that can be leveraged
  to enhance the performance and coverage of
  wireless networks such as WiFi (802.11) and WiMAX
  (802.16).
• DDI has implemented 3000 ArrayCom base stations.
• Worldwide, WLL markets offer good targets for
  smart antennas. Mobile networks in regions such
  as Asia Pacific and Eastern Europe, are slowly
  becoming good markets.

30
Continued

• Airgain, Inc., a developer of high-performance
  smart antenna
• solutions for the WLAN market.
• Airgain, Inc. launched A2475 Smart Antenna,
  solution for wireless access points, routers and
  gateway devices.

31
Garmin GXM 30 XM Smart Antenna for XM Radio/
NavTraffic/ XM XW Weather.
32
Research by NASA andGeorgia Inst. Of Tech.
33
Image taken From Satellite Using AAA
34
APPLICATIONS
35
CONCLUSION

• Beamforming antenna systems improve wireless
  network performance
• -increase system capacity
• -improve signal quality
• -suppress interference and noise
• -save power
• Beamforming antennas improve infrastructure
  networks performance. They may improve ad hoc
  networks performance. New MAC protocol standards
  are needed.
• Vector antennas may replace spatial arrays to
  further improve beamforming performance

36
CONCLUSION

• With different structures, adaptive array
  antennas play important roles in the evolution
  of wireless communications systems .
• Applications where cost and power consumption are
  the main limited factors, parasitic array
  antennas are suitable.
• DBF array antennas and phased array antennas
  dominate in the applications such as satellite
  communications, where high performance is
  desired.
• In addition to combating fading, diversity
  antennas can also be employed to realize
  high-speed MIMO wireless transmissions.

37
References

• Design of a Smart Antenna for Reducing Co-Channel
  Interference in Cellular Mobile Communications,
  Adel A. Saleeb, IEEE 1999
• J.H. Winters, Smart antennas for wireless
  systems, IEEE
• Personal Com. Magazine, pp. 23 -27, Feb.
  1998.

38
THANK YOU