Design Problem 2 451

8/8/2019 Design Problem 2 451

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DESIGN PROBLEM 2

ECE451MICROWAVE

Design a micro strip line system for transmitting microwave of 100 GHz. Discuss

following points:

1. Design at system level.

2. Design layout of components.

3. Design schematic of components.

4. Detail of component used.

5. Electrical qualities of design.

SUBMITTED TO:

MS.NAVPREET KAUR

SUBMITTED BY:

ARUN KUMAR

RA6701A11

7460070002

B.TECH (HONS.)ECE



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Micromachined Microstrip Antenna

THE microstrip antenna is a very good common element in telecommunication and radar

applications since it provides a wide variety of designs, can be planar or conformal, and can be

fed in many different methods It is also compact and suitable for antenna array designs.

Microstrip antennas can be used in applications which require high-performance compact low-

cost planar antennas such as imaging arrays and collision-avoidance radars. The aperture coupled

microstrip antenna is of great interest since it allows for the electromagnetic separation of the

radiating element (the microstrip patch) and the feed network with the use of the ground plane.

At millimeter-wave frequencies, many limitations have to be overcome in order to design high-

performance microstrip antennas on silicon or GaAs substrates. The high dielectric constant of

the substrates used (for silicon) implies that surface waves are more easily triggered in the

substrate. The power lost to surface waves can be reduced by using thin substrates, typically

where is the dielectric wavelength. At 94 GHz for silicon, it corresponds to around 100- m-thick

substrates

MICROSTRIP ANTENNA:

IT is a Low gain antenna. At millimeter-wave frequencies, standard IC fabrication techniques

use silicon (er = 11.7) and GaAs (er = 12.9) substrates in this TM0 surface waves triggered into

the substrate and loss of power occurs in this we should Choose thin substrates ( h £ ld / 10 for

silicon we should Reduce the substrate er around and below the antenna by etching a cavity in

the silicon.

Surface wave in grounded dielectric



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Q2. Microstrip Antenna Layout

Microstrip antenna layout

Q1. Design of antenna

Procedure of design:

a. Patch antenna size determines frequency of resonance

c. H-shaped coupling aperture determines the coupling ratio. A small coupling is preferred toimprove the radiation front-to back ratio

c. Coupling aperture size determines the real part of the antenna

d .Imaginary part compensated by microstrip open stub

e. CPW-to-microstrip transition design

Cross section of antenna



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Cpw to microstrip transition

Two aperture-coupled microstrip antennas are designed for 94-GHz operation. One is built on a

full 100- m-thick silicon wafer and the other on a 200- m-thick silicon wafer in which a 150 m

deep cavity has been etched using tetramethyl ammonium hydroxide (TMAH) or potassium

hydroxide (KOH) wet-etching technique.



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RADIATION EFFICIENCY

The radiometric technique is an accurate method to measure the radiation efficiency of planar

antennas using standard hot/cold load measurements. The RF chain is calibrated using a standard

WR-10 pyramidal horn which has a known radiation efficiency of 97–98%. The horn is then

replaced by the microstrip antenna connected to the chain via a W -band picoprobe. This method

is a double side-band (DSB) measurement since no rf Filter is used to separate the upper side-

band from the lower side-band before mixing down to the intermediate frequency (IF). The

measurement is, therefore, more accurate if a small IF is chosen

Radiometric set up 85-100 ghz



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RF efficiency

Qualities of design

a. Micromachining techniques suitable for millimeter-wave aperture-coupled microstrip antennas

b. Small volume, light weight

c· Mutual coupling better than -20 dB

d· 50 % radiation efficiency

e· 10 dB front-to-back ratio

f· Applications to fully micro machined millimeter-wave phased arrays

Design Problem 2 451

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