SUMMARY

This unit's core results, gathered in one place: the basic elements needed to transmit and receive a signal over a long distance using electromagnetic waves are a transducer, an amplifier, a carrier signal, a modulator, a power amplifier, a medium of transmission, transmitting and receiving antennas, a demodulator and a detector. For long-distance transmission, the baseband signal must first be modulated onto a carrier wave. If the amplitude of the carrier signal is modified according to the instantaneous amplitude of the baseband signal, the result is called amplitude modulation; if instead the carrier's frequency is modified this way, the result is frequency modulation; and if the carrier's phase is modified while its amplitude and frequency stay constant, the result is phase modulation. The height of a transmitting or receiving antenna must be a multiple of $\lambda/4$. If the electromagnetic waves radiated by the transmitter glide along the surface of the Earth to reach the receiver, that propagation is called ground wave propagation; if instead the waves are radiated upward at large angles and reflected by the ionosphere back to Earth, it is called sky wave propagation; and the process of sending and receiving an information signal directly through space is called space wave communication. Satellite communication relays a signal between transmitter and receiver via an orbiting satellite. Fibre-optic communication is the method of transmitting information by sending pulses of light through an optical fibre. RADAR stands for Radio Detection And Ranging, one of the important applications of communication systems used for remote sensin …