IndiaBIX

Electronics and Communication Engineering - Microwave Communication

Exercise : Microwave Communication - Section 4
16.
A 75 ohm line is first short terminated and minima locations are noted. Then the short is replaced by resistive load and minima location are again noted. If minima location are not altered and VSWR is 3, the value of resistive load is
25 Ω
50 Ω
225 Ω
250 Ω
Answer: Option
Explanation:

rv and VSWR .

17.
The word 'LORAN' means
long range navigation
long range TV transmission
long range cable transmission
either (b) or (c)
Answer: Option
Explanation:
No answer description is available. Let's discuss.
18.
In the given figure forward voltage wave has a magnitude
90 V
60 V
30 V
10 V
Answer: Option
Explanation:
No answer description is available. Let's discuss.
19.
The duty cycle of a radar transmitter is equal to
(PRF) (pulse width)
(PRF)/(pulse width)
(pulse width)/(PRF)
(pulse width) + (PRF)
Answer: Option
Explanation:
No answer description is available. Let's discuss.
20.
In a klystron amplifier the bunching effect
converts velocity modulation into current modulation of beam
converts current modulation into velocity modulation of beam
both (c) and (b)
neither (a) nor (b)
Answer: Option
Explanation:

A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers