What Are All The Different Parts In Modem?

The term modem is short for modulator-demodulator. In general, the modulator has the means for converting a baseband analog or digital signal to a form suitable for use by a transmitter connected by some transmission medium to a receiver. The signal from the receiver is demodulated and returned as nearly as possible to the original baseband form. Some modems are designed to perform the transmitter and receiver functions as well as the modulator and demodulator functions.

In the modulator, the signal will generally be converted to a digital form, if it is not already. It may be compressed and encoded. The encoded signal is used to modulate a carrier in any of a variety of forms, depending on the transmitter and medium. (The output may be electrical, or it may be sound for use by an acoustic coupler to a phone line, or it may be light for use by an optical fiber.)

The received signal will generally be filtered, demodulated, decoded, error-corrected, decompressed, and returned to its baseband form. In addition to performing these functions, the demodulator will usually also reconstitute the clock used for timing the digital bits.

The parts of the modem, then, are compressor, encoder, modulator, filter, clock reconstructor, demodulator, decoder, and decompressor. Depending on the baseband signal, there may also be analog-to-digital and digital-to-analog converters. The encoder and decoder may include error-correction. Depending on the medium, there may also be a transmitter and receiver, or those may be separate (as is usually the case for radio or microwave transmission). There may also be spectrum spreading and despreading involved.