Definition - What does Pulse Amplitude Modulation (PAM) mean?
- Pulse amplitude modulation (PAM) is one of several forms of single modulation in which data is transmitted through varying the amplitude of the pulses in regular timed sequence of electrical or electromagnetic pulses. In the case of analog pulse amplitude modulation signals, the number of pulse amplitudes can be infinite. Pulse amplitude modulation is mostly used in digital data transmission with non baseband applications.
- Pulse amplitude modulation is used in the popular Ethernet communication standard.
- We observe that by using flattop samples to generate a PAM signal, we introduce amplitude distortion as well as a delay of T/2. This effect is similar to the variation in transmission frequency that is caused by the finite size of the scanning aperture in television. The distortion caused by the use of PAM to transmit an analog signal is called the aperture affect. This distortion may be corrected by using an equalizer (see Figure 2.10). The equalizer has the effect of decreasing the in-band loss of the filter as the frequency increases in such a manner to compensate for the aperture effect. For T/Ts ≤ 0.1, the amplitude distortion is less than 0.5%, in which case the need of equalization may be omitted altogether.
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