FMsignaale

FMsignaale are signals that use frequency modulation, where the instantaneous frequency of a carrier is varied in proportion to the input signal. In practice, FMsignaale are the standard form of frequency-modulated radio signals used for broadcasting, two-way radio, and many telemetry systems. The key characteristic is that information is encoded in frequency changes rather than amplitude.

In an FMsignale, the carrier frequency f_c is shifted by an amount Δf that depends on the modulating signal m(t). The peak deviation Δf specifies how far the instantaneous frequency can move from the carrier, and the modulation index β is defined as Δf divided by the highest frequency of the modulating signal. This approach provides strong resilience to amplitude fluctuations and noise, at the expense of requiring more bandwidth than amplitude-modulated signals.

Historically, frequency modulation was developed and refined in the early 20th century, with significant contributions from Edwin Armstrong in the 1930s. FMsignaale gained prominence for radio broadcasting because they maintain strength in the presence of amplitude distortion and multipath, delivering clearer audio, especially in noisy environments. They are widely used for broadcast radio, aeronautical communications, and land-mobile radio, as well as for certain telemetry and data links.

Common variants include wideband FM (WFM) and narrowband FM (NBFM). In broadcasting, FMsignaale typically occupy the VHF band and use a standard maximum deviation around 75 kHz, with baseband audio up to about 15 kHz, a 19 kHz stereo pilot tone, and, in many regions, a 57 kHz RDS subcarrier. Demodulation is usually performed with discriminators or phase-locked loop receivers, often implemented in analog or digital form.