Question

(a) Describe the principle of operation of

                (i) Klystron amplifier

                (ii) Travelling wave tube (TWT) amplifier.

(b) A parabolic reflector is used to receive a satellite signal of 4 GHz. If the beamwidth of the device is

      2.50

(i) find the diameter of the parabolic reflector.

              (ii) calculate the gain of the device assuming that the efficiency factor is 50%

Answer 1

(a) (i)

This klystron amplifier operation is based on the velocity modulation concept only.

(ii)

A TWT (travelling wave tube) as the name itself indicates the radio frequency input travels along the tube with the velocity of light as the electron beam is focused and directed by the usage of magnetic field.

Simply, a cathode upon hearing produces beam of electrons and these are attracted by anode at collector side. In between, for the electrons not to get scattered we provide a magnetic field.

This is similar to that of klystron. Except that this uses magnetic external magnetic field and klystron uses cavities.

(b)