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Questions and Answers
What is the effect on the deviation d of an FM signal when it is passed through a mixer?
What is the effect on the deviation d of an FM signal when it is passed through a mixer?
What is the output signal from a DSB-SC modulator?
What is the output signal from a DSB-SC modulator?
What is the purpose of an amplitude limiter in FM receivers?
What is the purpose of an amplitude limiter in FM receivers?
What is the modulation index of an FM wave given by s(t)=20cos(8π×106t+9sin(2π×103t))?
What is the modulation index of an FM wave given by s(t)=20cos(8π×106t+9sin(2π×103t))?
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What is true about Frequency Modulation?
What is true about Frequency Modulation?
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What does the amount of frequency deviation in FM signal depend on?
What does the amount of frequency deviation in FM signal depend on?
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What is the modulation index of FM given by?
What is the modulation index of FM given by?
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What happens to the frequency deviation Δ when the modulating frequency is doubled?
What happens to the frequency deviation Δ when the modulating frequency is doubled?
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What is the result of the amplitude of the modulating signal being greater than the amplitude of the carrier?
What is the result of the amplitude of the modulating signal being greater than the amplitude of the carrier?
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What is the ratio of the modulating signal voltage to the carrier voltage called?
What is the ratio of the modulating signal voltage to the carrier voltage called?
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What type of frequency modulation is generated using a VCO?
What type of frequency modulation is generated using a VCO?
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When does over-modulation occur in amplitude modulation?
When does over-modulation occur in amplitude modulation?
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What is the modulating signal voltage if the maximum and minimum voltages on the wave are 10v and 5v respectively?
What is the modulating signal voltage if the maximum and minimum voltages on the wave are 10v and 5v respectively?
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What is the circuit used for producing DSB-SC called?
What is the circuit used for producing DSB-SC called?
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What modulation technique is used to convert analog signal into digital signal?
What modulation technique is used to convert analog signal into digital signal?
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What is the bandwidth of a carrier wave with a modulating frequency varying between 900kHz and 1100kHz?
What is the bandwidth of a carrier wave with a modulating frequency varying between 900kHz and 1100kHz?
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What is the expression for bandwidth BW of a PCM system?
What is the expression for bandwidth BW of a PCM system?
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Which of the following is an indirect form of frequency modulation?
Which of the following is an indirect form of frequency modulation?
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What is the characteristic of a uniform quantizer in PCM?
What is the characteristic of a uniform quantizer in PCM?
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What is the maximum bandwidth of the message in a PCM system with a 7-bit binary encoder and a bit rate of 49*10^6bps?
What is the maximum bandwidth of the message in a PCM system with a 7-bit binary encoder and a bit rate of 49*10^6bps?
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In which type of modulation is the amplitude of the pulse train varied?
In which type of modulation is the amplitude of the pulse train varied?
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What is the signal to quantization noise ratio for a signal with a highest frequency component of 3.2MHz and peak to peak value 6 volt, transmitted using PCM with 512 quantization levels?
What is the signal to quantization noise ratio for a signal with a highest frequency component of 3.2MHz and peak to peak value 6 volt, transmitted using PCM with 512 quantization levels?
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Study Notes
Modulation Techniques
- Pulse Code Modulation (PCM) converts analog signal into digital signal
- Other modulation techniques: AM modulation, FM modulation
Bandwidth of PCM System
- Expression for bandwidth BW: BW > nfm, where n is the number of bits per sample and fm is the modulating frequency
Uniform Quantization
- Step size remains same in uniform quantization process
- The quantizer has linear characteristics
PCM System
- Bit rate of the system is equal to 49*10^6bps
- Maximum bandwidth of message: 7Mbps
Pulse Amplitude Modulation
- Amplitude of the pulse train is varied in pulse amplitude modulation
Signal to Quantization Noise Ratio
- For a signal with highest frequency component of 3.2MHz and peak to peak value 6 volt, signal to quantization noise ratio is 36.98dB
Amplitude Modulation
- The ratio between the modulating signal voltage and the carrier voltage is called modulation index
- Over-modulation occurs when the amplitude of the modulating signal is greater than the amplitude of the carrier
Voltage-Controlled Oscillator (VCO)
- VCO is used to generate indirect FM
DSB-SC Modulator
- The circuit used for producing DSB-SC is called a modulator
Frequency Modulation
- The two types of angle modulation are phase and frequency modulation
- Phase modulation is an indirect form of frequency modulation
- The amount of frequency deviation is proportional to the amplitude of the intelligence signal in an FM signal
FM Signal
- The effect on the deviation d of an FM signal when it is passed through a mixer: doubles
- In Frequency Modulation, amplitude of the carrier remains same, frequency of the carrier varies in accordance with the modulating signal, and the number of side bands are infinite
- The modulation index of FM is given by μ = frequency deviation/ modulating frequency
- According to Carson’s rule, Bandwidth B and modulating frequency fm are related as B = 2(Δf + fm) Hz
Disadvantages of PCM
- Encoding, decoding and quantizing circuitry of PCM is complex
- PCM require large bandwidth as compared to the other systems
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Description
Test your knowledge of digital signal processing concepts, including modulation techniques, pulse code modulation, and quantization process.
