JNTU III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008
(Electronics & Communication Engineering)
1. (a) Explain clearly the different high frequency effects in electron tubes and show how these are eliminated in the design of a high frequency microwave tube.
(b) The bunching grids of a Klystron amplifier are 2 mm apart. The beam voltage is 2KV and the drift space is 2.8 cm. Long. What must be the value of the RF voltage at the bunching grid to produce maximum fundamental components of the current at the catcher. Assume the operating frequency 2.8 GHz. On what factors does the bunching parameter depend upon.
2. (a) Explain the use of slow wave structure in TWT amplifier. Give neat sketches of different structures.
(b) Explain the working of a O-type Backward wave oscillator.
3. (a) Explain the principle of _ mode oscillations in cylindrical magnetron.
(b) Write short notes on ‘Reike’ diagram and its significance.
4. (a) Write short notes on “Parametric up converter”.
(b) What is a MASER? What does its name signify? What applications does it have?
5. (a) A rectangular wave-guide has a cross section of 1.5 cm x 0.8 cm, ?=0, ?= ?0
and 2= 420. The magnetic field component is given as
Hx = 2Sin ????_xa _ cos ????3_yb _ Sin (? × 1011t ? ? z) A/m
i. The mode of operation
ii. The cut off frequency
iii. The phase constant
iv. The propagation constant
v. The wave impedance.
(b) Write short notes on “Rectangular resonant Cavity”.
6. (a) Explain the working of two hole directional coupler with a neat diagram.
(b) Explain about E plane Tee junction with a neat sketch. Why it is called a series Tee?
7. (a) What are ferrites? List out their characteristics.
(b) What are scattering parameters? Explain the S matrix of a three port ideal
8. (a) Explain how you measure VSWR of given load for all kinds of loads possible.
(b) Give the measurement procedure of Q factor of a resonant cavity.