Elements of a Communications Link
Transmitter
The transmitter (TX) element processes message signal in order to produce a signal
most likely to pass reliably and efficiently through the channel. This usually involves
modulation of a carrier signal by the message signal,
coding of the signal to help correct for tranmission
errors, filtering of the message or modulated signal to constrain the occupied bandwidth,
and power amplification to overcome channel losses.
Transmission Channel
Loosley defined as the electrical medium between source and destination, e.g. cable,
optical fibre, free space, the channel is characterised by its
Loss/Attenuation, Bandwidth,
Noise/Interference and Distortion.
Receiver
The receiver (RX) function is principally to reverse the modulation processing of the transmitter in order to recover the message signal, attempting to compensate for any signal degradation introduced by the channel. This will normally involve amplification, filtering, demodulation and decoding and in general is a more complex task than the transmit processing.