STUPIDSID
1(a)
What is Causal system?
2 M
1(b)
Find the Fourier transform of impulse function.
2 M
1(c)
What are the merits and limitations of Fourier Transform?
3 M
Solve any one question from Q.1(d) & Q.1(e)
1(d)
Find the Fourier series of the function
x(t)=cos(5t) + cos(15t)
in exponential form.
x(t)=cos(5t) + cos(15t)
in exponential form.
7 M
1(e)
Find the Fourier transform of the function
x(t)=5t2-15t
How will be the Fourier transform be changed if this function has a period of 10 sec.?
x(t)=5t2-15t
How will be the Fourier transform be changed if this function has a period of 10 sec.?
7 M
2(a)
The antenna current of AM transmitter is 10 amperes for only the carrier component and 11 amperes when carrier is modulated. Find the depth of modulation.
2 M
2(b)
What is meant by vestigial side band transmission?
2 M
2(c)
How modulation index in AM can be determined with the help of an oscilloscope?
3 M
Solve any one question from Q.2(d) & Q.2(e)
2(d)
Suppose nonlinear devices are available for which the output current i0 and input voltage vi are related by i0=avi+b vi3
where a and b are constant. Explain how these devices may be used to produce the product modulation.
where a and b are constant. Explain how these devices may be used to produce the product modulation.
7 M
2(e)
Show that any scheme that can demodulate DSB-SC can also demodulate AM. Is the converse also true?
7 M
3(a)
Illustrate the relationship between FM and PM with the help of block diagram.
2 M
3(b)
A Carrier is frequency modulated by two sinusoidal signals of frequency f1and f2. Make out an expression the FM signal defining the modulating signal clearly.
2 M
3(c)
A 400Hz modulating signal of voltage 2.4 volts is modulated under FM to have a modulation index of 60. Calculate the maximum deviation and required bandwidth.
3 M
Solve any one question from Q.3(d) & Q.3(e)
3(d)
Justify the statement 'FM has infinite bands'. Calculate the bandwidth of an FM signal generated to have a deviation of 75 kHz by a message signal of 9 kHz. What is the modulation index of the FM wave?
7 M
3(e)
An angle modulated signal with carrier frequency ωc=2π×106
s(t)=10 cos(ωc +0.1 sin2000πt)
i) Find the power of the modulated signal
ii) Find the frequency deviation
iii) Find the phase deviation
s(t)=10 cos(ωc +0.1 sin2000πt)
i) Find the power of the modulated signal
ii) Find the frequency deviation
iii) Find the phase deviation
7 M
4(a)
List the advantages of Superheterodyne receiver over TRF receiver.
2 M
4(b)
List the factors influencing the choice of IF for a radio receiver.
2 M
4(c)
In a superheterodyne receiver the input AM signal has a center frequency of 1425 kHZ and bandwidth 10 kHZ. The input is down converted to 455 kHZ (single stage down conversion). What is the image frequency?
3 M
Solve any one question from Q.4(d) & Q.4(e)
4(d)
Draw the block diagram of high level AM transmitter and explain the function of each block.
7 M
4(e)
In a broadcast super-heterodyne receiver having no RF amplifier, the loaded Q of the antenna coupling circuit (at the input to the mixer) is 100. If the intermediate frequency is 455 kHz, calculate:
i) The image frequency and rejection ratio at 1000kHz.
ii) The image frequency and its rejection ratio at 25 mHz.
i) The image frequency and rejection ratio at 1000kHz.
ii) The image frequency and its rejection ratio at 25 mHz.
7 M
5(a)
Explain the significance of the term 'Noise temperature' as applied to a receiver.
2 M
5(b)
Calculate the system noise of a receiver that has three stages of a receiver having overall gain of 40dB and bandwidth of 30kHz.The noise figure is 7dB. Assume T0=290°K and Boltzmann's constant 1.38 ×10-23 J/°K.
2 M
5(c)
Calculate the minimum receivable signal in radar receiver which has an IF bandwidth of 1.5mHz and a 9-dB noise figure.
3 M
Solve any one question from Q.5(d) & Q.5(e)
5(d)
The first stage of a two stage amplifier has a voltage gain of 10,600 ohms input resistance, 1600 ohms equivalent noise resistance and 27K ohms resistance. For the second stage these values are 25, 81 K ohms and 1 M Ohms respectively. Calculate the equivalent input noise resistance of two amplifier.
7 M
5(e)
Calculate the noise voltage at the input of television RF amplifier using a device that has a 200 ohms equivalent noise resistance and 300 ohms input resistance. The band width of amplifier is 6 mHz and temperature is 17 degree C.
7 M
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