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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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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [2]

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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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [3]

Construction and Geometry

• 2.2 < Єr < 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 into the air.

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [4]

Types of Microstrip antennas

a) Single radiating patchesSquare, rectangular, dipole, circular, elliptical, triangular, etc.

b) Single slot radiator Narrow slot, circular ring slot, wide slot, circular patch slot.

c) Microstrip traveling wave antennasComb, meander line type, rectangular loop type, Franklin – type MTWA.

d) Microstrip antenna arraysConsists of series of antennas connected with each other to give better performance.

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [5]

Feeding methods

a) 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 impedance matching.

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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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [6]

Criteria for substrate selection

a) Possibility for surface-wave excitationb) Effects of dispersion on the dielectric constant and low

tangent of the substratec) Magnitude of copper loss and dielectric lossd) Anisotropy in the substratee) Effects of temperature, humidity, and agingf) Mechanical requirements: conformability, machinability,

solderability, weight, elasticity, etc.g) Cost

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [7]

Polarization types

• Linear polarization

• Circular polarization

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [8]

Bandwidth consideration

Narrowband Vs. Broadband Bandwidth measurement

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [9]

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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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [10]

Some important structures

•Rectangular patch

Transmission model

Cavity model

• Circular patch

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [11]

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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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [12]

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Technical Seminar Presentation-2004

Presented By: Danish Kumar Hotta [EC200117169] [13]