Carrier signal

Carrier signal or carrier briefly (English carrier) is a periodically changing technical size (eg, an AC voltage or a radio wave ) with constant characteristic parameters (eg frequency, amplitude, duty cycle ). The carrier signal is the reference signal for demodulation of a previously for the purpose of transmitting the modulated carrier with an information signal.

The carrier signal, the carrier or the carrier frequency itself, or information from which the carriers can be reconstructed for the demodulation, if it is, for example, for certain types of modulation of the carrier is not transmitted.

Carrier frequency

The transmission technology of the carrier is typically a sinusoid of a particular frequency. In radio transmitters this is often at the same time, the nominal frequency of the emitted radio wave. With infrared or laser - transmission or other carrier frequency method, however, other, different or more carrier frequencies can be used simultaneously.

Symbols for the carrier frequency is or.

In the choice of carrier frequency different factors play a role:

First, here are called the transmission medium and the propagation behavior of the carrier signal. To enable the frequency range of the short-wave radio links with very large range, since the radio waves are reflected from ionospheric layers and the surface. In wireline communications, the transmission range of the type and quality of the cable and the distance depends.

To focus both the transmitted wave energy to a desired receiver and to achieve a higher sensitivity in the direction of a desired station, a directivity of an antenna is desired to be ( microwave ). The directivity of an antenna is dependent on the wavelength used and thus of the carrier frequency. At a smaller wavelength, and therefore a higher frequency is the same directivity may be achieved with a smaller antenna.

Directional antennas are, for example for terrestrial television reception (usually Yagi antennas ), radio links, to communicate with spacecraft, satellite television (usually parabolic antennas ) are used.

At higher frequencies, more bandwidth is available. This can be used to more information (eg TV compared to radio or radio) or the same information to be transmitted at a higher quality (for example, frequency modulation and amplitude modulation).

In Germany, regulates the frequency usage plan which frequency ranges can be used under what conditions, that is, by whom which carrier frequency may be used for radio transmission, what degree of modulation and may be used which type and what is the maximum transmitting power allowed.

For cable connections, and the so-called remote cables are often used carrier frequency systems are used.