Yashwantrao Chavan Maharashtra Open University 2007 B.E EC 1305 — TRANSMISSION LINES AND WAVEGUIDES - Question Paper

EC 1305 — TRANSMISSION LINES AND WAVEGUIDES

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2007.

Fifth Semester

(Regulation 2004)

Electronics and Communication Engineering

Time: 3 hours
Maximum: 100 marks

PART A — (10 x two = 20 marks)

1. describe propagation constant of a transmission line.
2. compute the characteristic impedance of a transmission line if the subsequent measurements have been made on the line Zoc= 550 /__-60 degree ohm and Z sc = 500/__30 degree.
3. elaborate the applications of the quarter—wave line?
4. A 50 ohm line is terminated in load ZR =90+j60 ohm. Determine the reflection coefficient.
5. elaborate the characteristics of principal wave?
6. describe the cut—off frequency of a guide.
7. A rectangular waveguide with dimensions a = 8.5 cm and b = 4.3cm is fed by five GHz carrier. Will a TE11 mode be propagated?
8. describe wave impedance and write the expression for wave impedance of TE waves in rectangular guide.
9. elaborate the applications of cavity resonators?
10. Write Bessel's function of 1st type of order zero.

PART B — (5 x 16 = 80 marks)

11. (a) (i) Derive the expressions for the input impedance of a transmission line. (10)
(ii) A cable has the subsequent parameters:
R: 48.75 ohm/km, L: 1.09 mH/km, G: 38.75 MU/km and C: 0.059 uf/km.
Determine the characteristic impedance, propagation constant and wavelength for a source of f: 1600 Hz and Es: 1.0 volts. (6)

Or

(b) (i) A cable has been uniformly loaded by an inductance such that wl >> R . Assuming leakage conductance to be nil, deduce an expression for attenuation and phase constant without neglecting R.
(ii) A transmission line has the subsequent parameters per km R: 15 ohm, C: 15 uf, L: one mH and G: one uU. obtain the additional inductance to provide distortion-less transmission. compute attenuation and phase constant for the loaded line. ( eight )

12. (a) (i) Deduce the expression for constant — S circle for the dissipation-less line and discuss. ( eight )
(ii) A transmission line is terminated in ZL. Measurements indicate that the standing wave minima are 102 cm apart and that the last minimum is 35 cm from the load end of the line. The value of
standing wave ratio is 2.4 and R0 :250 ohm. Determine wave length and load impedance. ( eight )

Or

(b) (i) discuss the procedure of double stub matching on a transmission line with an example. ( eight )
(ii) Determine the length and location of a single short circuited stub to produce an impedance match on a transmission line with R0 of 600 Q and terminated in 1800 Q. ( eight )

13. (a) (i) Derive the expressions for the field components of TM waves ranging from parallel plates, propagating in Z direction. (10)
(ii) For a frequency of six GHz and plane separation = seven cm. obtain the subsequent for the TE1o made z
(1) Cutoff frequency
(2) Phase and group velocity. (6)

Or

(b) (i) discuss wave impedance and find the expressions of wave impedance for TE and TM waves guided along parallel planes, Also sketch the variation of wave impedance with frequency. (10)
(ii) For a frequency of five GHz and plane separation of eight cm in air, obtain the subsequent for TM mode (6)
(1) Cut-off wave length
(2) Characteristic impedance and
(3) Phase constant.

14. (a) (i) find the solution of Electric and Magnetic fields of TM waves guided along rectangular wave guide. (10)
(ii) A rectangular waveguide measures three >< 4.5 cm internally and has a 10 GHz signal propagated in it. compute the cut-off wavelength, the guide wavelength and the characteristic wave impedance for the TE mode. (6)

Or

(b) (i) explain the attenuation of electromagnetic wave s guided along rectangular waveguide. ( eight )
(ii) elaborate the dimensions of a waveguide with the subsequent specifications?
(1) At a frequency of 9959.5 MHz, the guide wavelength for TE mode is 87.57% of the cut-off wavelength
(2) TEao and TEiz mode have the identical cut-off frequency. ( eight )

15. (a) (i) Determine the solution of electric and magnetic fields of TM waves guided along circular waveguide. (10)
(ii) A circular waveguide has an internal diameter of four cm. For a 10 GHZ signal propagated in it in the TEn mode, compute cut—off wavelength, guide wavelength and characteristic impedance. Uhm: 1.84 (6)

Or

(b) (i) find the expression for resonant frequency of circular cavity resonator. ( eight )
(ii) compute the resonant frequency of a rectangular resonator of dimensions a: three cm, b: two cm and d = four cm if the operating mode is TEioi. presume free space within the cavity. (8 )

Earning:   Approval pending.