Modulation techniques

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What is the major requirement for pulse code modulation? a. digital to analog conversion b. analog to digital conversion c. serial to parallel conversion d. parallel to serial conversion: b. analog to digital conversion
What is the major requirement for PCM demodulation? a. digital to analog conversion b. analog to digital conversion c. serial to parallel conversion d. parallel to serial conversion: a. digital to analog conversion
What is the number of digital levels that an analog signal can be divided into? a. bits in AID converter b. quantization level c. Nyquist rate d. Noise: b. quantization level
What is/are the outputs of a pulse code modulator circuit? a. carrier signal and information signal b. information signal c. carrier signal d. pulse string: d. pulse string
What is/are the input/s to a PCM demodulator circuit? a. carrier signal and information signal b. information signal c. carrier signal d. pulses: d. pulses
What does the PSK signal represent? a. HIGH and LOW levels in the information signal b. frequency changes in the information signal c. amplitude levels in the information signal d. phase changes in the information signal: a. HIGH and LOW levels in the information signal
What is the purpose of the input amplifier in the pulse code modulator circuit? a. compensate of attenuation and distortion b. scale digital input c. scale analog input d. generate pulses: c. scale analog input
In a QPSK system, how many information bits are represented by one cycle of the carrier signal? a. 4 b. 3 c. 2 d. 1: c. 2
How many phase shifts are used in a QPSK system and what is normally used? a. 2; 0° and 1800 b. 2; 45° and 225° c. 4; 0°, 90°, 180° and 270° d. 4; 90, 135°, 225°, 270°: c. 4; 0°, 90°, 180° and 270°
In a PSK/QPSK system, how many cycles of the carrier signal are phase shifted for each bit or two bits of the modulating input? a. 4 b. 3 c. 2 d. 1: d. 1
What is the output of a PSK demodulator circuit? a. digital information signal b. analog information signal c. 2fc d. 4fc: a. digital information signal
What digital data is generated for a 0 degree phase shift signal in the PSKIQPSK demodulator circuit? a. 1100 b. 0011 c. 1001 d. 0110: a. 1100
What is the minimum carrier frequency required in a FSK system using information signals ranging from 1 kHz to 6 kHz? a. 1kHz b. 5kHz c. 6kHz d. 30 kHz: d. 30 kHz
If the information signal is HIGH, what is the normal frequency of the FSK signal? a. F max b. FC c. F min d. 0: a. F max
If the information signal is LOW, what is the normal frequency of the FSK signal? a. F max b. FC c. F min d. 0: c. F min
What is the bandwidth of a FSK system that has a fc of 10 kHz and uses ±1 kHz frequency changes? a. 1kHz b. 9kHz c. 10 kHz d. 11 kHz: d. 11 kHz
In a typical FSK modulator, what type of FM modulator does the switching circuit drive? a. VCO b. PLL c. PCM d. Ratio: a. VCO
What is the purpose of the FM modulator in a FSK modulator? a. Change digital input into three voltage levels b. Change analog input into three voltage levels c. Generate frequency modulated signal d. Generate digital pulses: c. Generate frequency modulated signal
What is the purpose of the switching circuit in a FSK modulator? a. Change digital input into three voltage levels b. Change analog input into three voltage levels c. Frequency modulate the carrier signal d. Generate f min, FC and f m: a. Change digital input into three voltage levels
What is the input to a FSK demodulator circuit? a. Digital information signal b. FM signal c. AM signal d. FC: b. FM signal
What is the output of the NE567 FC Detector circuit if f min is received in the FSK demodulator? a. HIGH, indicating that the demodulator output is HIGH. b. LOW. indicating that the demodulator output is LOW. c. HIGH, indicating it h: c. HIGH, indicating it has not been received.
How is the FC Detector PLL circuit different from the FM Demodulator PLL circuit? a. The output of the VCO is not connected to the comparator b. The VCO is maintained at one frequency c. The input is converted to digital d. The output: b. The VCO is maintained at one frequency
When an FDM system uses several groups, which carrier frequencies must be different? a. Subcarriers for each group. b. Main carrier for each group. c. Subcarrier and main carriers for each group. d. None, all carrier frequencies must: b. Main carrier for each group.
What type of signal processing is used in FDM systems? a. AM only b. FM only c. AM and FM d. FSK or PSK: c. AM and FM
How is FDM accomplished? a. Combining several analog signals by FM modulation. b. Combining several digital signals by AM modulation. c. Combining several digital information signals by phase shifting. d. Combining several analog info: a. Combining several analog signals by FM modulation.
How is crosstalk reduced or eliminated in FDM systems? a. Crosstalk cannot be reduced or eliminated b. Guard Phases c. Guard Times d. Guard Bands: d. Guard Bands
What do the high and low levels in a Level DM system represent? a. High, positive signal - Low, negative signal b. High, increasing signal - Low, decreasing signal c. Positive, decreasing signal - Negative, increasing signal d. Positi: b. High, increasing signal - Low, decreasing signal
What does the DM signal represent? a. Amplitude changes in the information signal b. Frequency changes in the information signal c. Amplitude levels in the information signal d. Phase changes in the information signal: a. Amplitude changes in the information signal
How is delta modulation accomplished? a. Modifying sampling pulses with an information signal b. Modifying an information signal with sampling pulses c. Generating a string of pulses that represent changes d. Generating a string of pu: c. Generating a string of pulses that represent changes
What is the output of the comparator in a DM modulator circuit? a. Delayed information b. High or low levels c. Information signal d. DM signal: b. High or low levels
What is the output of the integrator in a DM modulator circuit? a. Delayed information b. High or low levels c. Information signal d. DM signal: a. Delayed information
What is the condition of the output signal if the input to a DM level demodulator is LOW? a. Increasing b. Decreasing c. Constant d. Pulse: b. Decreasing
What is the condition of the output signal if the input to aDM level demodulator is toggling? a. Increasing b. Decreasing c. Constant d. Pulse: c. Constant
What is/are the input/s to a DM demodulator circuit? a. Carrier signal and information signal b. Information signal c. Carrier signal d. Pulses: d. Pulses

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