Radio transmitter ICs are electronic devices that propagate radio frequency (RF) electromagnetic signals. They are used in high-end remote keyless entry systems, automatic meter reading devices, building automation and industrial controls, and consumer radios. Radio transmitter ICs are also used in other consumer electronics such as MP3 players, telecommunications systems, wireless devices, and for broadcasting TV signals and data. These tiny devices have an integrated circuit (IC) form factor, but are functionally similar to traditional radio transmitters. With radio transmitter ICs, the generated signals are sent to the media through a tiny antenna. Typically, this antenna is internal to the device, and is known as a chip antenna or embedded antenna.
There are many different types of radio transmitter ICs. FM devices use frequency modulation (FM), a technique that causes the instantaneous frequency of a sine-wave carrier to depart from the center frequency by an amount proportional to the instantaneous value of the modulating signal. AM radio transmitter ICs are also available. These devices use amplitude modulation (AM), a technique that causes the baseband signal to vary the amplitude or height of the carrier wave to create the desired information content. Radio transmitter ICs for specific applications such as process control, telecommunication, and consumer radios are also available.
Some radio transmitter ICs are designed for very high frequency (VHF) or ultra high frequency (UHF) applications. Other are designed for TV broadcasting, short-wave, or long-wave communications. VHF transmitters are designed for radio frequencies between 30 and 300 MHz. For television applications, there are two distinct bands. The TV VHF-low band extends from 54 MHz to 88 MHz, or from channels 2 to 6. The TV VHF-high band ranges from 174 MHz to 216 MHz, or from channels 7 to 13. The ultra high frequency (UHF) portion of the electromagnetic spectrum covers 300 MHz to 3.0 GHz. One of the bands within this part of the spectrum is the TV UHF band, which ranges from 470 MHz to 806 MHz, or from channels 14 to channel 69. Radio transmitter ICs for other specialized or proprietary applications are also available from a variety of suppliers.