JNTU III B.Tech II Semester Supplementary Examinations, Aug/Sep 2008, Microwave Engineering
( Common to Electronics & Communication Engineering and Electronics &
1. (a) Derive the wave equation for a TM wave and obtain all the field components
in a rectangular wave guide.
(b) A rectangular wave guide with dimension of 3 × 2 cm operates in the TM11 mode at 10 GHz. Determine the characteristic wave impedance.
2. (a) What is the effect of conductivity on the dielectric loss of a strip line?
(b) Derive the expression for attenuation constant for dielectric loss.
3. (a) Show the attenuation produced by rotary vane attenuator is given by – 40 log(sin?).
(b) Describe in detail about linear phase changer.
4. (a) Derive S – matrix for series Tee using the properties of S parameters.
(b) A Three port circulator has an insertion loss of 1dB, isolation 30 dB and VSWR = 1.5. Find the S – matrix.
5. (a) A reflex klystron has following parameters:
V0 = 800v, L = 1.5mm, Rsh = 15k ? 2, f = 9GHZ. Calculate
i. The repeller voltage fro which the tube can oscillate in 134 mode.
ii. The direct current necessary to give a microwave gap voltage of 200V.
iii. Electron efficiency.
(b) Name different methods of generating microwave power. Describe the necessary theory & Working of reflex klystron.
6. (a) Give the different types & explain the characteristics of slow wave structure.
(b) A TWT operates with following parameters:
Vb=2.5KV, Ib=25mA, Zo=10 , circuit length,L=50,f=9GHz
Find the gain parameter & power gain.
7. (a) A Ku-band IMPATT diode has a pulse operating voltage of 100v and a pulse
operating current of 0.9 A. The efficiency is about 10%. Calculate
i. The output power
ii. The duty cycle if the pulse width is 0.01ns and frequency is 16 GHz.
(b) Describe the principle of operation of IMPATT diode.
8. (a) How are microwave measurements different from low frequency measurements.
(b) What is the average power of a periodicwave if the peak power is 1300 W and the pulse width is 0.56 and periodic frequency of the wave is 1500 Hz.