In microwave system the function of mode filter is

Beam width between nulls of a parabolic antenna . Therefore 50° is the nearest value.

Turn ratio is so selected as to give low SWR at both ports.

If Z_L is load impedance and Z₀ is characteristic impedance.

Input impedance =. If Z_L = Z₀ the input impedance = Z₀.

Cathode is the first part and anode is the last.

Since R_L < Z₀, r_v is negative.

Since reactance does not contribute thermal noise to the circuit, it is a low noise device.

If line is o.c. |r_v| = 1 and VSWR = ?.

A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field.

This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms.

A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.

Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.

and is thus proportional to cross sectional area.

It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

The growing RF wave travels in opposite direction to the electron beam.

The frequency of wave can be changed by changing the voltage which controls the beam velocity.

Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

It features are:

1. Frequency range - 1 GHz to 1000 GHz.

2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

It is used as signal source in transmitters and instruments.