Method for generating a frequency modulation

摘要

In the previous circuits for generating a frequency modulation, a large number of side oscillations were produced above and below the carrier, the number being dependent on the modulation index. These side oscillations also determine the bandwidths. In the invention, the side oscillations are avoided in that the amplitudes of code pulses or of PAM pulses are converted into pulse duration pulses and after that are shaped into square width pulses, for example by means of an electronic relay. Using a low-pass filter, the square width pulses are then converted into a sinusoidal alternating current. The periods of the pulse duration pulses, of the square width pulses and of the halfwaves or periods of the sinusoidal alternating current are always the same so that the change in the PDM pulses also results in a change in the frequency of the coding AC, this therefore being a frequency modulation.