What is Analog Pulse Modulation ?
Pulse-amplitude modulation (PAM), is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal.
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http://en.wikipedia.org/wiki/Pulse-amplitude_modulation
Analog Pulse Modulation (APM) is a technique used in telecommunications and signal processing to transmit analog signals using digital means. It involves the encoding of the continuous analog signal into a series of discrete pulses.
To understand how APM works, let me explain the key steps involved:
1. Sampling: The first step is to sample the analog signal at regular intervals. This involves capturing the amplitude value of the signal at specific time points. The sampling rate determines how frequently the signal is sampled.
2. Quantization: Once the signal is sampled, the next step is to quantize the sampled values. Quantization involves assigning discrete amplitude levels to the sampled values. The number of possible amplitude levels is determined by the bit depth used for quantization. For example, if 8 bits are used, there will be 256 possible levels.
3. Encoding: After quantization, each quantized sample value is encoded into a binary code. The binary code represents the amplitude level of the sample. This can be achieved by converting the decimal value to its binary equivalent.
4. Modulation: The binary codes are then used to modulate a carrier signal. The most commonly used modulation techniques for APM are Pulse-Amplitude Modulation (PAM), Pulse-Position Modulation (PPM), and Pulse-Width Modulation (PWM). These modulation techniques vary in how the binary codes are used to modify the properties of the carrier signal, such as its amplitude, position, or width.
5. Demodulation: At the receiving end, the modulated signal is demodulated to extract the original analog signal. This involves reversing the modulation process, which typically includes extracting the binary codes and converting them back into quantized sample values. Finally, the quantized values are reconstructed into a continuous analog signal using a digital-to-analog converter (DAC).
Analog Pulse Modulation has applications in various fields, including telecommunications, audio signal processing, and data transmission. It offers advantages such as efficient use of bandwidth and noise immunity. However, it is susceptible to quantization error, which can introduce distortions in the reconstructed analog signal.