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7/31/2019 Rudra Pratap Singh-Microstrip Antenna
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In its most fundamental form, a Microstrip Patch antenna
consists of a radiating patch on one side of a dielectric
substrate which has a ground plane on the other side. In order to simplify analysis and performance prediction, the
patch is generally square, rectangular, circular, triangular, and
elliptical or some other common shape.
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Waves in microstrip patch antenna
1. Surface waves
2. Leaky waves
3. Guided waves
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1. Surface waves
2. Leaky waves
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Feed techniques
Feed techniques
Contacting Feed Non contacting feed
Microstrip feed
Coaxial feed
Aperture-coupled feed
Proximity-coupled feed
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1. Contacting feed
(a). Microstrip feed
(b). Coaxial feed
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2. Non contacting feed
(a). Aperture coupled feed
(b). Proximity coupled feed
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Low profile (can even be conformal)
Easy to fabricate(use etching and phototlithography)
Easy to feed(coaxiale cable, microstrip line etc.)
Easy to use in array or incorporate with other
microstrip circuit elements.
Patterns are somewhat hemispherical with a
moderate directivity(about 6-8 dB typical)
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Low bandwidth( but can be improved by a variety of
techniques). Bandwidth of a few percent are typical.
Efficiency may be lower than other antennas.Efficiency is limited by conductor and dielectric
losses, and by surface-wave loss.
Low gain.
Extraneous radiation from feeds and junctions.
Poor end fire radiator except tapered slot antennas.
Low power handling capacity.
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Directivity:
In view of the cavity model, the
simplified expression for directivity D can be written
as-
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Gain:
Gain of the patch antenna from the directivity
relative to the vertical axis is normally 2 dB.
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Bandwidth:
Bandwidth is related as-
where, S= voltage standing ratio,
Q0= unloaded radiation quality factor.
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Efficiency:
where, = efficiency,
Pr= radiated power,
Pt=power dissipated due to conductor loss,
Pd= power dissipated due to dielectric.
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Applications:
Microstrip antennas are increasingly gaining popularity
for use in wireless application due to their low profile
structure.
Some applications of microstrip patch antenna are
tabled as below-
Cellular phone & video
Collision avoidance radar
Direct broadcast satellite
Global positioning satellite
GSM & Paging
Personal communication system
Wide area computer networks
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