Anna University Chennai 2005 B.E DIGITAL COMMUNICATIONS - Question Paper
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the propagation constant of the wave along the line
(8)
Q. 3
A lossless transmission line has a normalised load admittance . The observed standing wave ratio on the line is 4.0. It is proposed to use a short circuited stub to match the load to the line.
Determine the electrical distance from the load to the place where the stub should be located.
obtain the length of the stub in terms of wave length.
(14)
Q.4 Derive the relevant equations to calculate the Wave impedance of TE mode in the waveguide. (7)
An air filled rectangular waveguide with dimensions of 2.0 cm x1.0 cm is operating at a frequency of 11 Ghz. obtain the subsequent :
(i) possible modes (ii) cut-off frequencies
(iii) guide wavelengths.
(7)
Q.5 Explain with the help of a neat figure, the microwave set up to measure the frequency of a wave in a waveguide. (7)
A slotted line is used to measure the frequency and it was obtained that the distance ranging from nulls is 1.85 cm. provided the guide dimension as three cm x 1.5 cm, compute the value of the frequency
Q.6
discuss 2 properties of Scattering matrix.
obtain the Scattering matrix of a Magic Tee using the above principles.
(4)
(10)
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PART II
ans any 3 ques.. every ques. carries 14 marks.
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Q.7 Explain the working of Travelling Wave Tube with neat diagrams.
(7)
In a helix-type travelling wave tube operating at five x 108 Hz, the pitch to the circumference ratio of the helix is one : 10 and the beam density is such that the plasma, frequency is . What accelerating voltage is needed for the electron gun in order that the condition shall be fulfilled? Where , and are the phase constant of the transmission line model of the slow wave structure, the beam and in plasma respectively.
(7)
Q. 8 A standard x - band waveguide with inside dimension 2cm x one cm is connected to a different waveguide with dimension 1.6cm x 0.8 cm. The latter guide is terminated in a matched load. compute VSWR that would be caused by this discontinuity at 10 GHz. (Reactance associated with the geometrical discontinuity may be ignored.)
discuss with neat diagram, the principle of operation of Magnetron tube.
(7)
(7)
Q.9
discuss the working of
(i) Isolator (ii) Power splitter with neat figures.
(14)
Q.10 A LOS communication link operating at 50 MHz has the transmitting antenna at a height of 20 m. The distance to the receiving site is 15 Km, use the flat earth interference to compute the height of the receiving antenna for maximum received signal
(7)
In a communication link the antenna heights are 40 and 60 m. The distance ranging from terminals is 30 Km. presume standard refraction occurs. obtain the path gain factor for this system when presume a reflection coefficient of -1.
(7)
Q.11 Write short notes on any 4 of the subsequent :
(i) Microstripline.
(ii) Stripline.
(iii) Phase shifter.
(iv) E & H plane Tee.
(v) Varactor diode.
(vi) Troposcatter Propagation (31/2 x four = 14)
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| Earning: Approval pending. |
