In the given figure forward voltage wave has a magnitude

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.

The quantities required to be measured in microwave circuits are frequency, power and impedance.

Microwave frequency measurement is done by slotted line, resonant cavities and transfer oscillator.

Microwave power measurement uses bolometers and microwave power meters.

A self balancing bridge working on the principle of power substitution is commonly used.

Microwave impedance measurement is done by measurement of reflection coefficient and VSWR.

A slotted line and probe is a basic tool for these measurements.' Network analyser enables rapid impedance measurement over a broad frequency range.

The action of varactor diode is due to the capacitance of depletion layer. The thickness of depletion layer depends on the reverse bias which should not cause breakdown.