Final MTech Project

Design & Performance Analysis of Micro-strip Patch Antenna Array for DBS(Direct Broadcast Satellite) & MSA(Mobile System Application)

Arun Kumar Roll No. H10449M.Tech (E.C.E)

(Communication Systems)Career Point University

Hamirpur,HP,India.

OBJECTIVE & METHODOLOGY

1. Design and Performance Analysis of Micro-strip Patch Antenna for DBS(Direct Broadcast Satellite) & MSA(Mobile System Application) .

2. To design and implement this antenna using software HFSS (High Frequency Structural Simulator),v 13.0 .

Antenna Definition & working

Antenna is one type of transducer that converts the time varying electrical lines and magnetic lines of forces which is confined inside the transmission line into the electro-magnetic energy by mean of discontinuity in the flared end structure of the same.As shown in Animation.

Antenna Properties at a Glance

Power gainDirectivityRadiation patternsPolarization GainBandwidth & BeamwidthRadiation IntensityEffective ApertureRadiation Resistance

Definition & Overview of Micro-strip Patch Antenna

One of the most useful antennas at microwave frequencies (f > 1 GHz).

It consists of a metal “patch” on top of a grounded dielectric substrate.

The patch may be in a variety of shapes, but rectangular and circular are the most common.

A Micro-strip patch antenna consists of a radiating patch on one side of a dielectric substrate which has a ground plane on the other side.

Invented by Bob Munson in 1972 (but earlier work by Dechamps goes back to1953).

What is Micro-strip Antenna?

Parameters of Micro-strip Antenna

L = Length of the Micro-strip Patch Element

W = Width of the Micro-strip Patch Element

t= Thickness of Patch

h = Height of the Dielectric Substrate.

Basic Principles of MPA OperationThe patch acts approximately as a resonant cavity (short circuit walls on top and bottom, open-circuit walls on the sides).In a cavity, only certain modes are allowed to exist, at different resonant frequencies. If the antenna is excited at a resonant frequency, a strong field is set up inside the cavity, and a strong current on the (bottom) surface of the patch. This produces significant radiation .

Important formulae of Micro-strip Patch Antenna

1. Height of substrate:

2. Patch Width:

3. Resonant frequency:

4. Effective dielectric constant:

Different Shapes of Micro-strip Patch Elements

Methods Of Analysis Of Microstrip Patch Antennas

Basic Three Models are available on the primary complicating factors of the dielectric substrate with the backing conducting ground:-

Transmission Line Model (by using low impedance stripline). Cavity Model (series cavity resonant mode). Integral and Differential equation models(method of moments).

1. Finite element method.

2. Finite difference method.

Polarization in Microstrip Patch Antennas

Basically two types of MPA Polarizations :

Linear Polarization1. Vertical Polarization

2. Horizontal Polarization

Circular Polarization1. Left circular

2. Right Circular

Horizontally polarized Dipole Antenna

Three Basic Type Of Polarizations

Microstrip Arrays and Feed Mechanism

Arrays are required for high gain (narrow beamwidth) to provide increased range , rejection against interference , beam scanning or steering and for some specific radiation pattern.

Different type of Arrays:

1. Two dimensional Arrays(End fed).

2. Series fed linear Arrays(Series mounted & Shunt mounted).

3. Hybrid-fed Array(Series + Shunt feeding).

4. Corporate(Parallel) fed linear Array.

Selection Of MPA Substrate

Two main features of substrate selection:

1. Dielectric constant should be low possible which results in tighter fabrication tolerances.

2. Loss tangent should be very low to increase antenna efficiency.

Feed Techniques in MPA

Micro-strip Patch antenna (MPA) can be feed by variety of methods. These methods can be classified into two categories-Contacting and Non-Contacting. The foremost popular feed techniques used are :-

Micro-strip line. Co-axial probe Aperture coupling Proximity coupling

Advantages of Micro-strip Patch Antenna

Light weight & Less volume hence compatible with modular design.. Low profile planar configuration which can be easily made conformal to host surface. Low fabrication cost, hence can be manufactured in large quantities. Supports both, linear as well as circular polarization with simple change in feed position. Can be easily integrated with microwave integrated circuits (MICs) and support Printed Circuit technology.Capable of dual and triple frequency operations. Mechanically robust when mounted on rigid surfaces.

DBS(Direct Broadcast Satellite)

Satellite the back bone of modern world communication systems e.g. Broadcast, Commercial & Military Telecommunications, Telemedicine, Remote sensing etc.

DBS is becoming popular television standard worldwide.

It consists of ground user antenna of gain approx. 33dbi with frequency 11.7GHz to 12GHz in Ku Band.

Uses conventional parabolic reflector antenna to receive signal.

Performance subject to degradation by Snow & Rain.

Microstrip Patch Antenna Advantages for DBS System

Parabolic antennas are very popular for receiving broadcasts from satellites, but replacing them by small, MSA (Microstrip antenna) is preferable, especially for the home use.

A large parabolic antenna, with the primary feed placed in front of the reflector, needs a wide area for installation while a flat structure can be a feature of an MSA (Microstrip antenna) array used for receiving satellite broadcasting needs less space.

A small, MSA (Microstrip antenna) can possibly be mounted on

the wall of the house or even placed inside the window at home, depending on the field strength at the receiving environment ,while it is difficult with conventional parabolic antenna.

Microstrip Antenna Advantages for DBS System (continued)…

MSAs of either square or circular patches with one or two feeding points can be used for generating the circular polarization and capable of Dual Frequency reception simultaneously i.e. two different applications can be run from single MSA array which is otherwise not possible with conventional parabolic antennas used in DBS systems.

Beam shapes such as a sector beam and a multi-beam can be produced by an array of MSA elements, which can be easily fabricated to form a flat structure, even though thousands of elements are used, by means of a photo-etch technique applied to the copper-clad dielectric substrate .

Existing DBS based Patch Antenna Array

Parameters of DBS:

Frequency range: 11.7 - 12.0 GHz

Polarization: right-hand circular

Gain more than: 33 dBi

Axial ratio: less than 1 dB

VSWR : less than 1.5

Types of array : Circular Patch Array. Rectangular Patch Array. Microstrip Reflect Array.

Introduction To Mobile Systems

Mobile communications often require antennas having small size, light weight ,low profile and low cost.

Microstrip antennas (MSA) are a type of antenna which can meet these requirements, and various MSAs have so far been developed and used for mobile communication systems.

The practical applications for mobile systems are in portable

or pocket-size equipment and in vehicles.UHF pagers, manpack radars, and car telephones are typical of those.

Introduction To Mobile Systems continued…..

Base stations for mobile communications need antennas with sector radiation patterns .Small , simple antennas are also favored, since the antenna tower built for the base station can then be smaller and need less support for the weight.

Ships and aircraft also demand small, lightweight antennas, and some times conformal structures are desirable to allow antennas to be mounted flush on the body of the moving vehicle.

MSAs are considered to be suitable for such conditions and many antennas have been developed and installed on ships and aircraft. Examples are a marine radar antenna and a surveillance radar antenna.

Type of Mobile System Application

Antennas meant for mobile systems can be divided in to three principal categories according to their usage.

Land mobile system. Maritime mobile system. Aeronautical mobile system.

First Proposed Design of Microstrip Antenna Array for DBS and Mobile Systems

50 ohm FEED LINE

Microstrip Antenna

Proposed Microstrip Antenna Array

Feed Point Feed Point

Expected Array in = 36dBi (after losses)

Specification for Microstrip antenna unit (circular) for First Proposed design array

Realized Gain 4.2dB at 12Ghz

Second Proposed Design of Microstrip Antenna Array for DBS and Mobile Systems

Proposed Microstrip

Antenna Array

Microstrip Antenna

FEED LINE

Expected Array Gain = 40 dBi (after losses)

Termination

Specification for Microstrip antenna unit (candy shaped) for Second Proposed design array

Realized Gain 4dB at 12Ghz

Graphical Parameters Of Importance

Figure 1.2 Return loss vs. frequency curve for different values of a.

Figure 1.1 Radiation Pattern for frequency 11.434 respectively.

Realized Gain vs Frequency plot

Performance analysis work related to Array design

By using HFSS software the following parameters of the two proposed design arrays will be studied , analyzed and compared with conventional parabolic antenna used in DBS systems:

Return loss vs frequency curve of proposed antenna. Radiation Pattern for the DBS frequency band. Realized Gain vs Frequency plot. Input power level requirement for operation. Atmospheric attenuation effect on performance.

References Constantine A. Balanis “Antenna Theory Analysis and

Design” 3rd edition. Microstrip patch Antenna Antenna-theory.com. Ramesh Garg “Microstrip Antenna Design Handbook”. Randy Bancroft, 2nd edition, ”Microstrip and Printed

Antenna Design”. Broadband Patch Antennas, J.-F. Zurcher and F. E. Gardiol,

Artech House, 1995. Broadband Microstrip Antennas, G. Kumar and K. P. Ray,

Artech House, 2002. Compact and Broadband Microstrip Antennas, K.-L. Wong,

John Wiley, 2003.