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Questions and Answers
What is the purpose of quantization in the sampling process?
What is the purpose of quantization in the sampling process?
- To represent digital data in waveform format
- To convert analog signals to their digital form
- To enhance the quality of the transmission medium
- To approximate the amplitude of a pulse to the nearest permitted integer (correct)
Which modulation technique is associated with converting analog amplitudes to discrete levels?
Which modulation technique is associated with converting analog amplitudes to discrete levels?
- Pulse Amplitude Modulation (PAM) (correct)
- Frequency Modulation (FM)
- Amplitude Modulation (AM)
- Pulse Code Modulation (PCM)
What defines attenuation in communication signals?
What defines attenuation in communication signals?
- The increase in signal strength with distance
- The conversion of digital signals into binary code
- The introduction of unwanted signals into a desired signal
- The decrease in signal strength as it travels along a transmission medium (correct)
Which type of noise is caused by natural atmospheric phenomena?
Which type of noise is caused by natural atmospheric phenomena?
What process converts discrete signals into highs (1) and lows (0)?
What process converts discrete signals into highs (1) and lows (0)?
What is the frequency of violet light with a wavelength of 400 nm?
What is the frequency of violet light with a wavelength of 400 nm?
What does the term 'modem' refer to?
What does the term 'modem' refer to?
What is the primary source of solar noise?
What is the primary source of solar noise?
In amplitude modulation (AM), which aspect of the carrier signal varies?
In amplitude modulation (AM), which aspect of the carrier signal varies?
What causes thermal noise in electrical conductors?
What causes thermal noise in electrical conductors?
If a sampling signal has a frequency of 50 Hz, what is its period?
If a sampling signal has a frequency of 50 Hz, what is its period?
Which modulation technique involves varying the frequency of the carrier?
Which modulation technique involves varying the frequency of the carrier?
Which type of noise is particularly noticeable in semiconductor devices?
Which type of noise is particularly noticeable in semiconductor devices?
What does distortion refer to in data transmission?
What does distortion refer to in data transmission?
What does modulation do to a data signal?
What does modulation do to a data signal?
How is the signal-to-noise ratio (S/N ratio) quantitatively described?
How is the signal-to-noise ratio (S/N ratio) quantitatively described?
What is the relationship between frequency and wavelength in a wave equation?
What is the relationship between frequency and wavelength in a wave equation?
In the formula $S/N ratio = 10 log_{10} (P_s / P_n)$, what does $P_s$ represent?
In the formula $S/N ratio = 10 log_{10} (P_s / P_n)$, what does $P_s$ represent?
When converting an analog signal to a digital signal, what process is commonly used?
When converting an analog signal to a digital signal, what process is commonly used?
What is the S/N ratio when a signal of 2.5 volts rms is corrupted by 10 mV rms of noise?
What is the S/N ratio when a signal of 2.5 volts rms is corrupted by 10 mV rms of noise?
What is the S/N ratio of a signal with 350 watts transmitted through a cable medium with 60 watts of noise?
What is the S/N ratio of a signal with 350 watts transmitted through a cable medium with 60 watts of noise?
What is the main difference between analog and digital signals?
What is the main difference between analog and digital signals?
Which formula correctly represents the relationship between wavelength, wave speed, and frequency?
Which formula correctly represents the relationship between wavelength, wave speed, and frequency?
How is frequency expressed in terms of measurement?
How is frequency expressed in terms of measurement?
What describes a periodic signal?
What describes a periodic signal?
How is amplitude defined in terms of a wave?
How is amplitude defined in terms of a wave?
If a signal has a period of 0.00235 seconds, how is its frequency calculated?
If a signal has a period of 0.00235 seconds, how is its frequency calculated?
Which of the following is NOT true about nonperiodic signals?
Which of the following is NOT true about nonperiodic signals?
What is the unit for measuring frequency?
What is the unit for measuring frequency?
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Study Notes
Types of Noise in Signals
- Solar Noise: Originates from the sun.
- Cosmic Noise: Generated by distant stars.
- Thermal Noise: Results from thermal agitation of charges in electrical conductors.
- Shot Noise: Caused by fluctuations in electrical current, noticeable in semiconductor devices.
Signal Distortion
- Distortion: Refers to the alteration of a signal during data transmission.
- Delay Distortion: A phenomenon in guided transmission media where different signal frequencies travel at different speeds.
Signal-to-Noise Ratio (SNR)
- Definition: A quantitative measure of signal quality, representing the ratio of signal power to noise power.
- Formula:
- ( \text{S/N ratio} = 10 \log_{10} \left( \frac{P_s}{P_n} \right) ) in dB
- ( \text{S/N ratio} = 20 \log_{10} \left( \frac{V_s}{V_n} \right) ) in dB
- Example Calculations:
- For a 2.5 volts rms signal with 10 mV noise: SNR = 48 dB.
- For a 350 watts signal with 60 watts noise: SNR = 7.66 dB.
Types of Signals
- Analog Signals: Continuous values, represented by a sine wave, e.g., speech and audio.
- Digital Signals: Binary values (0 and 1), represented by a square wave, having discrete levels.
- Periodic Signals: Repeated patterns within measurable time frames, called cycles.
- Nonperiodic Signals: Random changes without a repeating pattern.
Signal Properties
- Wavelength (( \lambda )): Related to frequency; ( \lambda = \frac{c}{f} ) where ( c ) is the speed of light.
- Frequency (( f )): Number of waves passing a point each second; ( f = \frac{1}{T} ) where ( T ) is the period.
- Amplitude: Height of the wave, measured from equilibrium to peak or trough.
Modems
- Definition: A combination of "modulator" and "demodulator" for converting digital data into a signal compatible with transmission media.
- Modulation Types:
- Amplitude Modulation (AM): Varies carrier amplitude based on the information signal.
- Frequency Modulation (FM): Varies carrier frequency based on the information signal.
- Phase Modulation (PM): Varies carrier phase based on the information signal.
Analog-to-Digital Conversion
- Sampling: Converts analog signals into discrete levels via ADC.
- Pulse Amplitude Modulation (PAM): Initial step in converting analog signals.
- Quantization: Approximates amplitude values of pulses to the nearest integer.
- Pulse Code Modulation (PCM): Represents discrete signals as binary equivalents.
Channel Impairments
- Attenuation: Decrease in signal strength with distance traveled along the medium.
- Noise: Unwanted signals superimposed onto desired signals.
- Atmospheric Noise: Arises from natural phenomena (e.g., lightning).
- Man-made Noise: Generated by human activities and electrical equipment.
- Extraterrestrial Noise: Includes solar and cosmic noise, originating from outside Earth.
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