Microwave Engineering Lab Viva Questions – Part 9

1) Which of the propagating modes has the lowest cut off frequency in the WR-90(X-band) rectangular waveguide - 0.9 *0.45 ( units of dimensions is inches)

a)TM01

b)TM10

c)TM11

d)TE21

Answer : [c] TM11

 

2) Which of the following are non dispersive structures

i) coaxial line

ii) micro strip line

iii)strip line

iv)circular waveguide

a)i, ii

b)ii, iii

c)i, iii

d)i, ii, iii

e)None of above

Answer : [c] i, iii

3) Z TEM is the wave impedance for the TEM mode, ZTE is the wave impedance for the TE mode, ZTM is the wave impedance for the TM mode, then(assume all modes are propagating )

a)ZTEM > ZTE > ZTM

b)ZTE >ZTEM >ZTM

c)ZTM >ZTE >ZTEM

d) ZTE =ZTM >ZTEM

Answer : [b] E >ZTEM >ZTM

4)

(i) In a Rectangular waveguide wave impedance can be defined where as characteristic impedance cannot be defined

(ii)Characteristic impedance cannot be defined for TE,TM waves where as wave impedance can be

defined

a)both (i),(ii) are true and (ii) is the correct reason for (i)

b) both (i),(ii) are true and (ii) is the not correct reason for (i)

c)( i) is true and (ii) is false

d)both (i),(ii) are false

Answer : [a] both (i),(ii) are true and (ii) is the correct reason for (i)

5.

(i) By changing the Gunn bias we can change the frequency of oscillations

(ii) By changing the repeller Voltage we can change the frequency of oscillations

a)(i) True,(ii)True

b)(i) True,(ii)False

c)(i) False,(ii)True

d)(i) False,(ii)False

Answer : [c] (i) False,(ii)True

7)

Assertion (A) : A microstrip line cannot support pure TEM mode of propagation

Reason (R) :A microstrip line suffers from various forms of losses.

a. Both A and R are true and R is the correct explanation of A

b. Both A and R are true but R is NOT the correct explanation of A

c. A is true but R is false

d. A is false but R is true

e. Both A and R are false

Answer : [b] Both A and R are true but R is NOT the correct explanation of A

9) Why is a reflex klystron oscillator preferred as an Ideal source in Microwave Measurements?

a. It provides high output power with single frequency

b. It provides high output power with wide frequency range

c. It provides low output power with stable single frequency

e. It provides low output power with multiple frequencies

None of the above

Answer : [d] it provides low output power with multiple frequencies

10) For a Gunn diode oscillator, the drift velocity of the electron is 107 cm/s and the active region ength is 10 × 10-4 cm. The natural frequency of oscillation would be

1 MHz

10 MHz

1 GHz

10 GHz

None of the above

Answer : [d] 10 GHz