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Electronics and Communication Engineering - Microwave Communication

Exercise : Microwave Communication - Section 3
1.
A cavity resonator is
a hollow metallic enclosure
a hollow enclosure having magnetic material as its walls
a hollow enclosure having dielectric material as its walls
either (b) or (c)
Answer: Option
Explanation:

Hollow metallic enclosures exhibit resonance behaviour when excited by electromagnetic field.

These enclosures are called cavity resonators.

2.
If antenna diameter is increased four times, the maximum range is increased by a factor of
2
2
4
0.2
Answer: Option
Explanation:

Range of radar is proportional to antenna diameter.

3.

Assertion (A): Gunn diode is a transferred electron device.

Reason (R): A Gunn oscillator uses the phenomenon of transferred electron effect.

Both A and R are correct and R is correct explanation of A
Both A and R are correct but R is not correct explanation of A
A is correct but R is wrong
A is wrong but R is correct
Answer: Option
Explanation:

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.

4.
Atomic and molecular resonance is observed in many substances
at microwave frequencies
at low frequencies
at frequencies used in AM broadcast
at both (b) and (c)
Answer: Option
Explanation:

Atomic and molecular distances are very small. Therefore resonance can occur only at microwave frequencies.

5.
The component in the given figure is
attenuator
T type low pass filter
T type high pass filter
phase shifter
Answer: Option
Explanation:

Z01 provides series inductances and teflon filled low impedance line Z02 provides shunt capacitance.

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