En Micro Strip Anteena

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169]

Compact Microstrip Antenna

By

Danish Kumar Hotta

Roll No: EC 200117169

Under the guidance of

Mr. Rowdra Ghatak


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Introduction

The microstrip antenna is a very thin metallic strip,

placed a small fraction of a wavelength above a

ground plane, separated by a dielectric.

Where size, weight, cost, performance, ease of

installation, are of primary concern, microstrip

antennas are the best solutions.


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Construction and Geometry

2.2 < r < 12. Low dielectric=>better efficiency, larger B/W. A microstrip patch antenna is a radiating patch on one side of

a dielectric substrate, which has a ground plane on the

underside. The EM waves fringe off the top patch into the

substrate, reflecting off the ground plane and radiates out intothe air.


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Types of Microstrip antennas

a) Single radiating patches

Square, rectangular, dipole, circular, elliptical,

triangular, etc.

b) Single slot radiator

Narrow slot, circular ring slot, wide slot, circularpatch slot.

c) Microstrip traveling wave antennas

Comb, meander line type, rectangular loop type,

Franklin type MTWA.d) Microstrip antenna arrays

Consists of series of antennas connected with each

other to give better performance.


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Feeding methodsa) Microstrip feed

Easy to fabricate, simple to match by controlling the inset

position and relatively simple to model.

b) Coaxial probe feed

Easy to fabricate, low spurious radiation; difficult to

model accurately; narrow bandwidth of impedancematching.

c) Aperture coupling (no contact), microstrip feed line and

radiating patch are on both sides of the ground plane, the

coupling aperture is in ground plane

Low spurious radiation, easy to model; difficult to match,narrow bandwidth.

d) Proximity coupling (no contact), microstrip feed line and

radiating patch are on the same side of the ground plane

Largest bandwidth (up to 13%).


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Criteria for substrate selection

a) Possibility for surface-wave excitation

b) Effects of dispersion on the dielectric constant and low

tangent of the substrate

c) Magnitude of copper loss and dielectric lossd) Anisotropy in the substrate

e) Effects of temperature, humidity, and aging

f) Mechanical requirements: conformability, machinability,

solderability, weight, elasticity, etc.g) Cost


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Polarization types

Linear polarization

Circular polarization


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Bandwidth consideration

Narrowband Vs. Broadband Bandwidth measurement


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Design methodology

Research

Determining substrate Permittivity

Bench mark with commercially available antenna

Design feed impedance

Investigate broad band techniques

Design the broadband patch


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Some important structures

Rectangular patch

Transmission model

Cavity model

Circular patch


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Conclusion

Disadvantages: Relatively low efficiency (due to dielectric

and conductor losses) Low power

Spurious feed radiation (surface waves,strips, etc) Narrow frequency bandwidth (at most a

couple of percent) Relatively high level of cross polarization

radiation Applications:

Radio and wireless communications, aircrafts,

spacecraft and missile.


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En Micro Strip Anteena

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