UNIT IV – PERFORMANCE OF CW MODULATION SYSTEMS
PART-A
1. What do you understand by Capture Effect in FM? NOV/DEC 2005, 2008, 2010
When the interference signal and FM input are of equal strength, the receiver fluctuates back and forth between them .This phenomenon is known as the capture effect.
2. What is the purpose of pre emphasis and de emphasis in FM? NOV/DEC 2007,2010
The psd of noise at the output of FM receiver usually increases rapidly at high frequencies but the psd of message signal falls off at higher frequencies. This means the message signal does not utilize the frequency band in efficient manner. Such more efficient use of frequency band and improved noise performance can be obtained with the help of pre emphasis and de-emphasis.
3. Define SNR. NOV/DEC 2005
It is defined as the ratio of signal power to the noise power.
4. How to achieve threshold reduction in FM receiver? NOV/DEC 2003
When the carrier to noise ratio reduces to certain value, the message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio.
5. Define threshold effect. NOV/DEC 2004, 2007, 2009
As the input noise power is increased the carrier to noise ratio is decreased the receiver breaks and as the carrier to noise ratio is reduced further crackling sound is heard and the output SNR cannot be predicted by the equation. This phenomenon is known as threshold effect.
6. What is meant by FOM of a receiver? NOV/DEC 2006
The ratios of output signal to noise ratio to channel signal to noise ratio is called figure of merit.
Figure of Merit = (SNR)o/(SNR)c = (So/No)/(Si/Ni)
7. What is threshold effect with respect to noise? MAY/JUNE 2007
When the carrier to noise ratio reduces to certain value, type message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio. This is called threshold effect.
8. What is FM threshold effect? NOV/DEC 2004, 2007
As the input noise power is increased the carrier to noise ratio is decreased the receiver breaks and as the carrier to noise ratio is reduced further crackling sound is heard and the output SNR cannot be predicted by the equation. This phenomenon is known as threshold effect.
9. Define Pre-emphasis. NOV/DEC 2010, 2007
The premodulation filtering in the transistor, to raise the power spectral density of the base band Signal in its upper-frequency range is called pre-emphasis (or pre distortion) Pre emphasis is particularly effective in FM systems which are used for transmission of audio signals.
10. Define De-emphasis. NOV/DEC 2010, 2007
The filtering at the receiver to undo the signal pre-emphasis and to suppress noise is called de- Emphasis.
11. What are the methods to improve FM threshold reduction? MAY 2010
Threshold reduction can be improved with the help of negative feedback in FM demodulator. It is achieved in FMFB demodulator.
12. What are the characteristics of super heterodyne receivers? MAY 2010
• It has wide range of tunable frequencies
• It has good selecting and rejection of adjacent channels
• It provides good amplification.
13. Compare the noise performance of DSBSC receiver using coherent detection with AM receiver using envelope detection. MAY 2011
In DSBSC receiver, the output signal to noise ratio is given as,
=
For envelope detection, the output signal to noise ratio is given as,
=
14. Differentiate input SNR from output SNR. MAY 2011
Input SNR = Average power of message signal at receiver input / Average power of noise at receiver input
Output SNR = Average power of message at receiver Output / Average power of noise at receiver output
15. Define the term – coherent detection in AM. MAY 2011
In the coherent detection of AM, a locally generated carrier is used. This carrier is in synchronism with the carrier at the transmitter.
16. Give the role of figure of merit in estimating the performance of a receiver.MAY 2011
• Figure of merit is used to compare the performance of different modulation systems.
• Since figure of merit is the ratio of output SNR to carrier SNR, if indicates better noise performance.
17. Define the term fidelity and selectivity of a receiver. DEC 2010
Fidelity: It is the response of the receiver over wide frequency range. Good response over wide range of bandwidth is called high fidelity receiver.
Selectivity: The selectivity is the ability of the receiver to select a signal of a desired frequency while rejecting all others.
18. State the expression for signal to noise ratio at the output of the receiver.MAY 2011
Signal to noise ratio at the output of the receiver is given
=
Here Pi is the input signal power
Fm is the highest signal frequency
19. Write the equation for transfer function of De-emphasis circuit. MAY 2011
Hd(f) = Here f1 = 1 / 2πRC
20. Define threshold effect in AM receiver. DEC 2010
When the carrier to noise ratio reduces to certain value, type message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio. This is called threshold effect.
21. What is sensitivity of receivers?
It is defined as a measure of its ability to receive weak signals
22. What is the SNR for AM with small noise case?
(So/No) / (Si/Ni) = (Ka2P) / (1+ Ka2 P)
23. Define Tracking.
Tracking is the process of correctly tuning a number of tunable circuits in a receiver.
24. What is TRF receiver?
Tuned Radio Frequency is also called straight receiver. Here the receiver operates in straight forward manner without frequency conversion.
25. What are the advantages of superheterodyne receiver over TRF?
The advantages of superheterodyne receiver over TRF are high selectivity; improved sensitivity throughout the carrier frequency band. It eliminates image frequency.
26. What is the figure of merit of DSBSC system?
The figure of merit of DSBSC signal is unity
27. Compare the noise performance of an AM and FM system?
The figure of merit of AM system is 1/3 when the modulation is 100 percent and that of FM is(3/2)mf2.The use of FM offers improved noise performance over AM . when (3/2)mf2 > 1/3.mf– modulation index in FM.
28. Define Sampling theorem.
A band limited signal of finite energy, which has no frequency components higher than fm Hertz may be completely recovered from a knowledge of its samples taken at the rate of 2fm samples per second.
29. What do you infer from the receiver output of a coherent detector?
The output equation y(t)=1/2Cacm(t) +1/2nI(t) indicates that the message signal and in-phase noise. Component of the filtered noise appear additively at the receiver output. The quadrature component of the narrow band noise is completely rejected by the coherent detector.
30. When is the figure of merit of SSBSC system?
For the same average transmitted signal power and the same average noise power in the message bandwidth, an SSB receiver will have exactly the same output signal to noise ratio as a DSB-SC receiver when both receivers use coherent detection for the recovery of the message signal.
31. Compare the noise performance of AM receiver with that of DSB-SC receiver.
The figure of merit of DSB-SC or SSB-SC receiver using coherent detection is always
unity, the figure of merit of AM receiver using envelope detection is always less than
unity. Therefore noise performance of AM receiver is always inferior to that of DSB- SC due to the wastage of power for transmitting the carrier.
32. What is the figure of merit of a AM system with 100 percent modulation?
The figure of merit of an AM system with 100 percent modulation is 1/3.This means that other factors being equal an AM system must transmit three times as much average power as a suppressed system in order to achieve the same quality of noise performance.
33. What are the characteristics of a receiver?
The characteristics of a receiver are sensitivity, selectivity, fidelity, and signal to noise ratio.
34. Why is equivalent noise temperature used for noise measurement?
For low noise devices the noise figure is close to unity, which makes the comparison difficult and hence it is preferable to use equivalent noise temperature.
35. What is the function of amplitude limiter in FM system?
The function of amplitude limiter in FM system is used to remove the amplitude variations by Clipping the modulated wave at the filter output almost to the zero axis .The resultant waves is rounded off by another BPF that is an integral part of the limiter thereby suppressing the harmonics of the carrier frequency.
36. What are components in a frequency discriminator?
Frequency discriminator has got two components .Slope detector or differentiator with a purely imaginary frequency response that varies linearly with frequency. It produces output where the amplitude and frequency vary with the message signal. An envelope detector that recover the amplitude variations and produces message signal.
37. What is a post detection filter?
The post detection filter named as”base-band low pass filter” has a bandwidth
that is just large enough to accommodate the highest frequency component of the message signal.
38. Define improvement factor.
The improvement factor IR is defined as the ratio of means output noise power without de-emphasis to the mean output noise power with de-emphasis.
39. Define input signal to noise ratio.
The input signal to noise ratio is defined as the ratio of the average power of the modulated signal to the average power of the filtered noise.
40. What is output signal to noise?
The output signal to noise ratio is defined as the ratio of the average power of the demodulated message signal to the average power of the noise, both measured at the receiver output.
41. Define channel signal to noise ratio.
The channel signal to noise ratio is defined as the ratio of the average power of the modulated signal into the average power of the channel noise in the message bandwidth both measured at the receiver input.
42. Define noise quieting effect.
In FM system as the carrier power increases, the effect of noise at the receiver output is reduced. This is called noise quieting effect.
43. Why the AM figure of merit is always <1?
The figure of merit of an AM receiver using envelope detection is always less than unity. This is due to the wastage of transmitting power, which results from transmitting the carrier as a component of the AM wave.
44. Define stability
Stability is the ability of the receiver to deliver a constant amount of output for a given period of time.
45. What is Nyquist rate?
The sampling rate 2fm samples per second for a signal bandwidth of fm hertz are called the nyquist rate. Its reciprocal 1/fm is called the Nyquist interval.
46. Write the advantages of super heterodyne receiver over TRF receivers?
• Improved selectivity in terms of adjacent channels.
• More uniform selectivity in terms of adjacent channel
• Improved receiver stability
• Uniform bandwidth because of fixed intermediate frequency
47. Write the advantages of a RF amplifier.
• Greater gain better sensitivity
• Improved signal to noise ratio
• Improved image frequency rejection
• Improved coupling of the receiver to the antenna
48. What the main functions of a receiver.
• Intercept the incoming modulated signal by the receiving antenna
• Select the desired signal and reject the unwanted signals
• Amplify this selected R.F signal
• Detect the modulated signal to get back the original modulating signal
• Amplify the modulating frequency signal
49. What are the drawbacks of emitter modulator?
• The amplifier is operated in class A mode, thus the efficiency is low.
• The output power is very small. Thus it is not suitable for generating high level modulation.
50. What do you mean by image frequency?
The local oscillator (fo), input signal frequency (f) and If some other frequency, f = fsi + 2fi appears at the input of mixer, then it produces fi at the output of the mixer fsi image frequency
51. What is intermediate frequency?
Intermediate frequency is defined as the difference between the signal frequency and the oscillator frequency.
IF = fs – fo when fs > fo , IF = fo – fs when fo > fs
52. What is the function of mixer?
The mixer stage is a nonlinear device and its purpose is to convert radio frequencies to intermediate frequencies.
53. What are the characteristics of a receiver?
The characteristics of a receiver are sensitivity, selectivity, fidelity, signal to noise ratio.
54. Why non-coherent detection is also called as envelope detection?
Non-coherent detection is often called envelope detection because the information is recovered from the received waveform by detecting the shape the modulated envelope.
55. Define Image frequency rejection ratio.
Image frequency rejection ratio is defined as the ratio of the gain at the signal frequency to the gain at the image frequency.
56. Define tracking errors.
If this tuning is not done precisely then the frequency difference i.e. (fo-fs) is not correct. These types of errors are known as the tracking errors.
57. Why do you meant by coherent radio receiver?
The frequencies generated in this receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter.
58. What is non coherent radio receiver?
In this receiver, either no frequencies are generated or the frequencies used for demodulation are completely independent from the transmitters’ carrier frequency.
PART – B
8 MARKS:
1. Explain the noise in AM receiver using its noisy model block diagram. (NOV/DEC 2006)
2. Calculate the noise power of a DSB-SC system using coherent detection.(MAY/JUNE 2006)
3. Discuss in detail the noise performance in SSB-SC receiver. (NOV/DEC 2007)
4.
5. Explain the noise model for AM system using envelope detection. (APRIL/MAY 2004)
6. Explain the superheterodyne FM receiver with block diagram. (NOV/DEC 2007)
7. Explain how threshold extension is achieved by FMFB technique.
8. Explain the Significance of Pre-emphasis and de-emphasis in FM system. (NOV/DEC 2006)
9. Compare the noise performance of AM and FM Systems (NOV/DEC 2005)
10. Define Hilbert transform with a suitable example. (MAY/JUNE 2007)
16 MARKS:
1. What is the function of pre-emphasis and de-emphasis in FM? Draw the circuit diagram of pre-emphasis and de-emphasis and explain its operation. (MAY/JUNE 2008)
2. Derive the expression for the power spectral density at the output of a FM discriminator when the received signal is corrupted by additive white Gaussian noise. (MAY/JUNE 2009)
3. Discuss the noise performance of different types of AM receivers in detail. (MAY/JUNE 2008)
4. Give the detailed noise analysis of a SSB receiver using Coherent detection. (MAY/JUNE 2009)
5. Write notes on the following i) FM threshold effect ii) FM threshold reduction. (NOV/DEC 2006)
PART-A
1. What do you understand by Capture Effect in FM? NOV/DEC 2005, 2008, 2010
When the interference signal and FM input are of equal strength, the receiver fluctuates back and forth between them .This phenomenon is known as the capture effect.
2. What is the purpose of pre emphasis and de emphasis in FM? NOV/DEC 2007,2010
The psd of noise at the output of FM receiver usually increases rapidly at high frequencies but the psd of message signal falls off at higher frequencies. This means the message signal does not utilize the frequency band in efficient manner. Such more efficient use of frequency band and improved noise performance can be obtained with the help of pre emphasis and de-emphasis.
3. Define SNR. NOV/DEC 2005
It is defined as the ratio of signal power to the noise power.
4. How to achieve threshold reduction in FM receiver? NOV/DEC 2003
When the carrier to noise ratio reduces to certain value, the message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio.
5. Define threshold effect. NOV/DEC 2004, 2007, 2009
As the input noise power is increased the carrier to noise ratio is decreased the receiver breaks and as the carrier to noise ratio is reduced further crackling sound is heard and the output SNR cannot be predicted by the equation. This phenomenon is known as threshold effect.
6. What is meant by FOM of a receiver? NOV/DEC 2006
The ratios of output signal to noise ratio to channel signal to noise ratio is called figure of merit.
Figure of Merit = (SNR)o/(SNR)c = (So/No)/(Si/Ni)
7. What is threshold effect with respect to noise? MAY/JUNE 2007
When the carrier to noise ratio reduces to certain value, type message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio. This is called threshold effect.
8. What is FM threshold effect? NOV/DEC 2004, 2007
As the input noise power is increased the carrier to noise ratio is decreased the receiver breaks and as the carrier to noise ratio is reduced further crackling sound is heard and the output SNR cannot be predicted by the equation. This phenomenon is known as threshold effect.
9. Define Pre-emphasis. NOV/DEC 2010, 2007
The premodulation filtering in the transistor, to raise the power spectral density of the base band Signal in its upper-frequency range is called pre-emphasis (or pre distortion) Pre emphasis is particularly effective in FM systems which are used for transmission of audio signals.
10. Define De-emphasis. NOV/DEC 2010, 2007
The filtering at the receiver to undo the signal pre-emphasis and to suppress noise is called de- Emphasis.
11. What are the methods to improve FM threshold reduction? MAY 2010
Threshold reduction can be improved with the help of negative feedback in FM demodulator. It is achieved in FMFB demodulator.
12. What are the characteristics of super heterodyne receivers? MAY 2010
• It has wide range of tunable frequencies
• It has good selecting and rejection of adjacent channels
• It provides good amplification.
13. Compare the noise performance of DSBSC receiver using coherent detection with AM receiver using envelope detection. MAY 2011
In DSBSC receiver, the output signal to noise ratio is given as,
=
For envelope detection, the output signal to noise ratio is given as,
=
14. Differentiate input SNR from output SNR. MAY 2011
Input SNR = Average power of message signal at receiver input / Average power of noise at receiver input
Output SNR = Average power of message at receiver Output / Average power of noise at receiver output
15. Define the term – coherent detection in AM. MAY 2011
In the coherent detection of AM, a locally generated carrier is used. This carrier is in synchronism with the carrier at the transmitter.
16. Give the role of figure of merit in estimating the performance of a receiver.MAY 2011
• Figure of merit is used to compare the performance of different modulation systems.
• Since figure of merit is the ratio of output SNR to carrier SNR, if indicates better noise performance.
17. Define the term fidelity and selectivity of a receiver. DEC 2010
Fidelity: It is the response of the receiver over wide frequency range. Good response over wide range of bandwidth is called high fidelity receiver.
Selectivity: The selectivity is the ability of the receiver to select a signal of a desired frequency while rejecting all others.
18. State the expression for signal to noise ratio at the output of the receiver.MAY 2011
Signal to noise ratio at the output of the receiver is given
=
Here Pi is the input signal power
Fm is the highest signal frequency
19. Write the equation for transfer function of De-emphasis circuit. MAY 2011
Hd(f) = Here f1 = 1 / 2πRC
20. Define threshold effect in AM receiver. DEC 2010
When the carrier to noise ratio reduces to certain value, type message information is lost. The performance of the envelope detector deteriorates rapidly and it has no proportion with carrier to noise ratio. This is called threshold effect.
21. What is sensitivity of receivers?
It is defined as a measure of its ability to receive weak signals
22. What is the SNR for AM with small noise case?
(So/No) / (Si/Ni) = (Ka2P) / (1+ Ka2 P)
23. Define Tracking.
Tracking is the process of correctly tuning a number of tunable circuits in a receiver.
24. What is TRF receiver?
Tuned Radio Frequency is also called straight receiver. Here the receiver operates in straight forward manner without frequency conversion.
25. What are the advantages of superheterodyne receiver over TRF?
The advantages of superheterodyne receiver over TRF are high selectivity; improved sensitivity throughout the carrier frequency band. It eliminates image frequency.
26. What is the figure of merit of DSBSC system?
The figure of merit of DSBSC signal is unity
27. Compare the noise performance of an AM and FM system?
The figure of merit of AM system is 1/3 when the modulation is 100 percent and that of FM is(3/2)mf2.The use of FM offers improved noise performance over AM . when (3/2)mf2 > 1/3.mf– modulation index in FM.
28. Define Sampling theorem.
A band limited signal of finite energy, which has no frequency components higher than fm Hertz may be completely recovered from a knowledge of its samples taken at the rate of 2fm samples per second.
29. What do you infer from the receiver output of a coherent detector?
The output equation y(t)=1/2Cacm(t) +1/2nI(t) indicates that the message signal and in-phase noise. Component of the filtered noise appear additively at the receiver output. The quadrature component of the narrow band noise is completely rejected by the coherent detector.
30. When is the figure of merit of SSBSC system?
For the same average transmitted signal power and the same average noise power in the message bandwidth, an SSB receiver will have exactly the same output signal to noise ratio as a DSB-SC receiver when both receivers use coherent detection for the recovery of the message signal.
31. Compare the noise performance of AM receiver with that of DSB-SC receiver.
The figure of merit of DSB-SC or SSB-SC receiver using coherent detection is always
unity, the figure of merit of AM receiver using envelope detection is always less than
unity. Therefore noise performance of AM receiver is always inferior to that of DSB- SC due to the wastage of power for transmitting the carrier.
32. What is the figure of merit of a AM system with 100 percent modulation?
The figure of merit of an AM system with 100 percent modulation is 1/3.This means that other factors being equal an AM system must transmit three times as much average power as a suppressed system in order to achieve the same quality of noise performance.
33. What are the characteristics of a receiver?
The characteristics of a receiver are sensitivity, selectivity, fidelity, and signal to noise ratio.
34. Why is equivalent noise temperature used for noise measurement?
For low noise devices the noise figure is close to unity, which makes the comparison difficult and hence it is preferable to use equivalent noise temperature.
35. What is the function of amplitude limiter in FM system?
The function of amplitude limiter in FM system is used to remove the amplitude variations by Clipping the modulated wave at the filter output almost to the zero axis .The resultant waves is rounded off by another BPF that is an integral part of the limiter thereby suppressing the harmonics of the carrier frequency.
36. What are components in a frequency discriminator?
Frequency discriminator has got two components .Slope detector or differentiator with a purely imaginary frequency response that varies linearly with frequency. It produces output where the amplitude and frequency vary with the message signal. An envelope detector that recover the amplitude variations and produces message signal.
37. What is a post detection filter?
The post detection filter named as”base-band low pass filter” has a bandwidth
that is just large enough to accommodate the highest frequency component of the message signal.
38. Define improvement factor.
The improvement factor IR is defined as the ratio of means output noise power without de-emphasis to the mean output noise power with de-emphasis.
39. Define input signal to noise ratio.
The input signal to noise ratio is defined as the ratio of the average power of the modulated signal to the average power of the filtered noise.
40. What is output signal to noise?
The output signal to noise ratio is defined as the ratio of the average power of the demodulated message signal to the average power of the noise, both measured at the receiver output.
41. Define channel signal to noise ratio.
The channel signal to noise ratio is defined as the ratio of the average power of the modulated signal into the average power of the channel noise in the message bandwidth both measured at the receiver input.
42. Define noise quieting effect.
In FM system as the carrier power increases, the effect of noise at the receiver output is reduced. This is called noise quieting effect.
43. Why the AM figure of merit is always <1?
The figure of merit of an AM receiver using envelope detection is always less than unity. This is due to the wastage of transmitting power, which results from transmitting the carrier as a component of the AM wave.
44. Define stability
Stability is the ability of the receiver to deliver a constant amount of output for a given period of time.
45. What is Nyquist rate?
The sampling rate 2fm samples per second for a signal bandwidth of fm hertz are called the nyquist rate. Its reciprocal 1/fm is called the Nyquist interval.
46. Write the advantages of super heterodyne receiver over TRF receivers?
• Improved selectivity in terms of adjacent channels.
• More uniform selectivity in terms of adjacent channel
• Improved receiver stability
• Uniform bandwidth because of fixed intermediate frequency
47. Write the advantages of a RF amplifier.
• Greater gain better sensitivity
• Improved signal to noise ratio
• Improved image frequency rejection
• Improved coupling of the receiver to the antenna
48. What the main functions of a receiver.
• Intercept the incoming modulated signal by the receiving antenna
• Select the desired signal and reject the unwanted signals
• Amplify this selected R.F signal
• Detect the modulated signal to get back the original modulating signal
• Amplify the modulating frequency signal
49. What are the drawbacks of emitter modulator?
• The amplifier is operated in class A mode, thus the efficiency is low.
• The output power is very small. Thus it is not suitable for generating high level modulation.
50. What do you mean by image frequency?
The local oscillator (fo), input signal frequency (f) and If some other frequency, f = fsi + 2fi appears at the input of mixer, then it produces fi at the output of the mixer fsi image frequency
51. What is intermediate frequency?
Intermediate frequency is defined as the difference between the signal frequency and the oscillator frequency.
IF = fs – fo when fs > fo , IF = fo – fs when fo > fs
52. What is the function of mixer?
The mixer stage is a nonlinear device and its purpose is to convert radio frequencies to intermediate frequencies.
53. What are the characteristics of a receiver?
The characteristics of a receiver are sensitivity, selectivity, fidelity, signal to noise ratio.
54. Why non-coherent detection is also called as envelope detection?
Non-coherent detection is often called envelope detection because the information is recovered from the received waveform by detecting the shape the modulated envelope.
55. Define Image frequency rejection ratio.
Image frequency rejection ratio is defined as the ratio of the gain at the signal frequency to the gain at the image frequency.
56. Define tracking errors.
If this tuning is not done precisely then the frequency difference i.e. (fo-fs) is not correct. These types of errors are known as the tracking errors.
57. Why do you meant by coherent radio receiver?
The frequencies generated in this receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter.
58. What is non coherent radio receiver?
In this receiver, either no frequencies are generated or the frequencies used for demodulation are completely independent from the transmitters’ carrier frequency.
PART – B
8 MARKS:
1. Explain the noise in AM receiver using its noisy model block diagram. (NOV/DEC 2006)
2. Calculate the noise power of a DSB-SC system using coherent detection.(MAY/JUNE 2006)
3. Discuss in detail the noise performance in SSB-SC receiver. (NOV/DEC 2007)
4.
5. Explain the noise model for AM system using envelope detection. (APRIL/MAY 2004)
6. Explain the superheterodyne FM receiver with block diagram. (NOV/DEC 2007)
7. Explain how threshold extension is achieved by FMFB technique.
8. Explain the Significance of Pre-emphasis and de-emphasis in FM system. (NOV/DEC 2006)
9. Compare the noise performance of AM and FM Systems (NOV/DEC 2005)
10. Define Hilbert transform with a suitable example. (MAY/JUNE 2007)
16 MARKS:
1. What is the function of pre-emphasis and de-emphasis in FM? Draw the circuit diagram of pre-emphasis and de-emphasis and explain its operation. (MAY/JUNE 2008)
2. Derive the expression for the power spectral density at the output of a FM discriminator when the received signal is corrupted by additive white Gaussian noise. (MAY/JUNE 2009)
3. Discuss the noise performance of different types of AM receivers in detail. (MAY/JUNE 2008)
4. Give the detailed noise analysis of a SSB receiver using Coherent detection. (MAY/JUNE 2009)
5. Write notes on the following i) FM threshold effect ii) FM threshold reduction. (NOV/DEC 2006)
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