subject: Pulse Amplitude Modulation [print this page] Pulse AmplitudeModulation is also known as PAM. This is the simplest form of pulse modulation. This technique helps to transmitdata by changing the power or voltage amplitudes of single pulse in a timed succession of electromagnetic pulses. In a different sense, the data that is to be transmitted is programmed in the amplitude of a chain of signal pulses. PAM is also used to generate extra pulse modulations.
Taking a look at this from a completely theoretical perspective, the potential pulse amplitudes in the pulse amplitude modulation could be infinite. This is just the case with analog pulse amplitude modulations. The 2-level PAM causes the resultant signal to be digitized whereas a 4 level pulse amplitude modulation consists of 22 potential separate pulse amplitudes. A pulse amplitude modulation of 8-level has 23 individual pulse amplitudes, and a 16-level pulse amplitude modulation consists of 24 discrete pulse amplitudes.
Concerning various pulse amplitude modulations, there are some systems which maintain the amplitude of every pulse. This amplitude is directly proportional to the immediate modulating-signal amplitude at the same time as pulse occurrence. For other pulse amplitude modulation systems, the reverse takes place that is, the amplitude is inversely proportional to the instant modulating-signal amplitude when the pulse occurs. In some other pulse amplitude modulation systems, the amplitude depends on additional factors that are related to modulating signal like the instantaneous phase and frequency, which might be different from its strength.
Nevertheless, in practical telecommunication applications, PAM is a very rarely used technology. It has been superseded by other techniques like pulse code modulation and pulse position modulation. Additionally, a new technology known as quadrature amplitude modulation is extensively used for telephone modems that have a data transfer rate more than 300 Kbps. I guess all doubts regarding PAM are cleared to you now? If Not ask for more.
