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Electronics and Communication Engineering - Microwave Communication

Exercise : Microwave Communication - Section 4
31.
Which of the following modes of transmission will not be supported by a rectangular waveguide?
TE15
TE12
TM11
TM10
Answer: Option
Explanation:
No answer description is available. Let's discuss.
32.
In a circular waveguide with radius r, the dominant mode is
TM01
TE01
TM11
TE11
Answer: Option
Explanation:

Some applications require dual polarization capability. Circular waveguide has this capability.

These analysis uses cylindrical coordinates.

In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode.

If D is diameter of waveguide

λc = 1.706 D for TE11 mode

λc = 1.029 D for TE21 mode

λc = 0.82 D for TE01 mode

λc = 1.306 D for TM01 mode.

33.
If 'a' is the width of rectangular wave guide and 'λ' is the wave length, then
Answer: Option
Explanation:
No answer description is available. Let's discuss.
34.
A parametric amplifier uses
non linear resistance
non linear reactance
either (a) or (b)
neither (a) nor (b)
Answer: Option
Explanation:

In a parametric amplifier the non-linear element is varactor diode or inductor.

35.

Assertion (A): Impatt diode can be used in both amplifiers and oscillators.

Reason (R): Impatt diode has a low resistance.

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:

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.

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