Subträger

Subträger, in German, refers to a subcarrier, a secondary carrier signal used in modulation schemes to convey information alongside or under a primary carrier. A subcarrier is typically a stable sinusoidal tone at a designated frequency, chosen so that its content can be separated by filtering and demodulated independently from other signals in the channel. Subcarriers enable frequency-division multiplexing and the transmission of multiple data streams within a single channel, or the conveyance of auxiliary information such as stereo difference signals or control data.

Common examples include FM stereo broadcasting, where a 38 kHz subcarrier carries the stereo difference signal, and a 19 kHz pilot tone helps the receiver recover the subcarrier. In modern communications, subcarriers are central to orthogonal frequency-division multiplexing (OFDM), where many closely spaced subcarriers carry independent data streams with orthogonal spacing to minimize interference. Subcarrier multiplexing is also used in fiber-optic and copper networks, where bandwidth is increased by transmitting data on multiple subcarriers.

Key considerations include the subcarrier frequency selection, bandwidth, power allocation, and the modulation scheme used on the subcarrier (for example, QAM or PSK). Accurate frequency generation and phase stability are important to maintain orthogonality and reduce interference. Subträger concepts also extend to digital-domain constructs, where subcarriers serve as carriers for pilot symbols, reference signals, or control channels.