Transmitter

A transmitter is an electronic device that generates a signal and transmits it through a medium, typically by radiating electromagnetic waves from an antenna in radio communications. It converts information into a carrier signal and then amplifies and couples it to an antenna so that it propagates through air, space, or along a transmission line. In most systems, the transmitter works in conjunction with a receiver to form a communications link.

A transmitter generally comprises an oscillator to generate a carrier wave, a modulator to impress information onto the carrier, a power amplifier to raise the signal to a usable level, and one or more filters and impedance-matching networks to control bandwidth and efficiency. The output is connected to an antenna or transmission line. Modern transmitters may be digital, using software-defined radios, with baseband processing performed in a processor before modulation.

Modulation methods determine how information is encoded onto the carrier. Analog modulation includes amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). Digital modulation uses schemes such as ASK, FSK, PSK, QAM, and more, often combined with error correction and multiplexing. Transmitters are designed for specific frequency bands and power levels, and their bandwidth is constrained by regulatory standards.

Regulatory authorities assign licenses and technical rules for transmitter operation to avoid interference with others. Safety and electromagnetic compatibility considerations also apply. Transmitters are used in radio broadcasting, mobile networks, satellite links, radar, navigation beacons, telemetry, and many other applications.