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Presentation no. 2Presentation no. 2

By:By: PPrateek rateek PPatelatelGaurav MaltareGaurav MaltarePuneetPuneet DDubey ubey

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INTRODUCTIONINTRODUCTION

In present era we need compact antennas incommunication applications.

T wo limitation of microstrip antennas are:-1. Low gain and2. Narrow bandwidth.

For compact antennas these two parametersfurther deteriorates .

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WHYWHY ??????

Size, bandwidth and efficiency of an antenna areinterrelated.

A s antennas are made smaller, either theoperating bandwidth or the antenna efficiency must decrease.

Gain and area of antenna are directly proportional to each other.

G=4 A/

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WHYCOMPACT

ANTENNAS

WHYCOMPACT

ANTENNAS??????

For wireless application we need small antennas,along with enhanced bandwidth and gain

Smaller the device smarter the antennas weneed.

Can be used at higher frequencies, for defenseand security purpose, lighter, cost effective,durable etc.

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OVERCOME T HE LIMITATIONSOVERCOME T HE LIMITATIONS

Some of the techniques to increases gain are:

Use of high permittivity dielectric superstratehelps in increasing the radiation efficiency

Inclusion of an amplifier type active circuitry A mplifier circuits integrated with the radiating patchto give rise to an active integrated antenna.

Stacked configurationIn stacked configuration two patches, driven andparasitic, are used with desired feeding technique.

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Some of the techniques to increases b andwidth

are:

Increasing substrate thickness .

Low dielectric constant.

But these two methods are limited by an inductiveimpedance offset that increases with thickness.

By changing patch geometry.

Using different feeding techniques .

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STACKED CONFIGURATIONSTACKED CONFIGURATIONIn stacked configuration two patches, driven andparasitic, are used with desired feeding technique.

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BW improvement by dielectric

BW improvement by dielectricconstantconstant

The combination of low dielectric constant andhigh dielectric constant can yield goodimpedance behavior.

The broadest bandwidth can be achieved whenthe substrate of lower patch have higher

dielectric constant than the upper substrate.

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BW improvement by dielectricBW improvement by dielectricthicknessthickness

The thickness of each layer also plays an importantrole in achieving the overall bandwidth. The thickerthe lower layer, the greater the bandwidth will be.the lower patch should be designed such that it isstrongly capacitive over the desired range of frequency instead of designing it for the minimumreturn loss.But the overall impedance will become inductive

when parasitic patch is placed onto theconfiguration, if lower layer is too thick.

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Antenna designAntenna design

First in the design is to select the dielectricsubstrate and then to fix the thickness h1 and h2.The lower substrate is of FR -4 ,thickness 4.8 mmUpper substrate is of foam with dielectricconstant of 1.07 and thickness 7 mm.The groove angle and the dimensions of both the

patches (driven and parasitic) are selected asoptimization variable with objective to get thecentral frequency 2.44 GHz

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RESULTS AND DI SUSS ION:

A size reduction of 66.34% can be achieved if

designed at 785 MHz frequency.

Gain is seen to be almost flat over the desiredrange of interest.

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T he characteristics in terms of VS WR

and gain are

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Conclusion

Conclusion

A new compact microstrip antenna is realized instacked configuration for WL A N application.

The stacked configuration enhances both gainand bandwidth of the antenna in the desired

band of interest.

A size reduction of 53% is obtained in theproposed configuration along with 4dBi gain and91 MHz band width.

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B ibliography .

GAIN AND BANDWIDTH ENHANCEMENT IN COMPACTMICROSTRIP ANTENNA paper by :-

Vibha Rani Gupta and Nisha Gupta