The fabrication of microstrip line is done by

Since all ports matched, input SWR = 1. No power is reflected and P_in = P₄ = 1 W.

This power splits between ports 1 and 2. Therefore P₁ = P₂ = 0.5 ?, P₃ = 0.

An Impatt diode has n⁺ - p - i - p ⁺ structure and is used with reverse bias.

It exhibits negative resistance and operates on the principle of avalanche breakdown.

Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit.

The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode.

The features of Impatt diode oscillator are : frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%.

Its applications include police radar systems, low power microwave transmitter etc.

Avalanche diode can also be operated in large signal high efficiency mode called Trapped Avalanche Transit Time mode.

The Trapatt oscillations depend on the delay in the current caused by avalanche process.

The avalanche delay makes it possible to increase the diode voltage well above the breakdown voltage.

Therefore a very rapid multiplication of charge carriers occurs. A Trapatt diode is also a negative resistance device.

The features of Trapatt diode oscillator are : Frequency 3 to 50 GHz, Power output 1-3 W, efficiency about 25%.

Its applications are low power doppler radar, microwave beacon landing system etc.

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A Microstrip line has a single dielectric substratc with ground plane on one side and a strip on the other face.

Its special feature is easy access to top surface so that minor adjustments can be made after circuit fabrication.

The high dielectric constant of the substrate reduces guide wavelength and circuit dimensions.

A microstrip line is the most commomly used transmission structure for microwave integrated circuits.

The condition for minimum distortion is found by equating The result is .

For ideal dielectric loss angle is zero. For good quality cables, loss angle is very small, about 1° only.

It allows high frequencies.