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RADIO FREQUENCY INTEGRATED CIRCUITS

MODULE I

DIVYA P V

ASST.PROFESSOR

EC DEPT

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Introduction to the technology of microwave integrated circuitsConventional Microwave circuits

1.Constructed in coaxial or waveguide technology

2.Circuits and other components (filterc,directional couplers)were fabricatedseparately and then screwed together

3.Conductors in conventional circuits are coaxial lines or waveguides. MICs

1.Same as integrated digital circuits.

2.All the components are connected to each other and manufactured by using the sametechnology in a planar form

3.Conductors in MICs are microstrip line

The specific method used to develop and produce a special circuit functions in

micro strip is known as micro strip technology.

Principal requirements for a transmission structure to be suitable as a circuit element

in MIC is that the structure should be planar in configuration. A planar configuration

implies that the characteristics of the element can be determined by the dimensions in

a single plane. For example the width of a micro strip line on a dielectric substrate can

be adjusted to control its impedance.

There are several transmission structure that satisfy the requirement of beingplanar

1.Microstrip

2.Coplanar waveguide

3.Slotline4.Coplanar strips

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There is a wide range of MICs

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Advantages of MICs

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SUBSTRATES

Criteria for the choice of substrate material

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Criteria for the choice of substrate material

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Production methods (Technology ) for MICs

Various technologies available for the production of MICs

Difference among them are substrare material, the method of

fabricating conductors, resistors and capacitors and the degree of

integration

Degree of integration is a measure of the number of integrated elements

to be included in the total circuit.

Integrated elements are elements produced by the same technique

as the conductors, whereas hybrid elements are elements produced

separately and added to the circuit later.

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Important MIC technology in order of degree of freedom

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Thin film Hybrid Circuits

Most commonly used technique for the production of MICs is the thin film hybridtechnology.

Technology get its name from the method producing conductors, resistances andcapacitance rather than from the thickness of the substrate.

Conductors are produced either by vapour deposition or sputtering, both of which areperformed in vacuum and provide layers wih a thickness of less than 1um.

For use in microwaves the conductors are galvanically thickened to between 5um and10 um to reduce the losses

Resistance and capacitance as well as conductors can be produced as integratedcomponents

For thin film circuits with capacitors,the surface must be locally glazed or we mustuse saphire.

If the MIC is to have magnetic components,such as circulators then ferrite or garnetmust be used as substrates

Plastic substrates cannot be used for thin-film technology because they cannotwithstand the high temperatures and their outgassing makes a high vacuum verydifficult to attain.