In Pulse Amplitude Modulation (PAM) and Demodulation, resistors are not specifically used to determine the modulation or demodulation process. However, resistors may be present as part of the overall circuitry involved in PAM systems.
PAM is a modulation technique where the amplitude of a series of pulses is varied in accordance with the amplitude of the modulating signal. The demodulation process involves extracting the original modulating signal from the modulated pulses. The resistor values used in the circuitry can vary depending on the specific design requirements and components involved.
To provide a general understanding, let's discuss the basic concepts and components involved in PAM and demodulation:
PAM Modulation:
Pulse Generator: A pulse generator produces a train of pulses where the amplitude of each pulse corresponds to the instantaneous amplitude of the modulating signal. The pulse generator typically uses a combination of digital circuits or analog components such as operational amplifiers, comparators, and timing elements.
Analog Signal Source: The modulating signal, which could be an audio or any analog signal, is the input to the PAM system. The amplitude of this signal determines the amplitude of the pulses generated.
Amplification and Shaping: In some cases, amplification and shaping stages may be required to condition the modulating signal before it is used to generate the pulses. Operational amplifiers or other amplification circuits may be used in this stage.
PAM Demodulation:
Low-Pass Filter: In demodulation, the modulated PAM signal is passed through a low-pass filter to remove the high-frequency components and retain the baseband signal. The cutoff frequency of the filter should be chosen based on the bandwidth of the original modulating signal.
Sampling: After the low-pass filter, the PAM signal is sampled at a rate higher than the Nyquist rate to reconstruct the original modulating signal. The sampling rate should be carefully chosen to avoid aliasing.
Reconstructing Circuitry: Following sampling, additional circuitry such as sample-and-hold circuits or reconstruction filters may be employed to reconstruct the original analog signal. These components may involve resistors, capacitors, and operational amplifiers, among others, based on the specific design requirements.
It's important to note that the specific resistor values used in PAM and demodulation circuits depend on various factors such as the desired signal quality, circuit specifications, component characteristics, and design constraints. The values are typically determined through circuit analysis, simulations, and optimization techniques to meet the desired performance criteria.