Abstract: The demodulator for digital modulation signals comprises a frequency detection device, an integral discharge filter, a summing device, a discrimination device, and a noise-compensating signal generation device. The frequency detection device outputs frequency detection signals by detecting frequencies of the digital modulation signals. The integral discharge filter outputs phase deviation signals by integrating the frequency detection signals for a given interval. The feedback summing device outputs compensated phase deviation signals to the discrimination device by feeding back the noise-compensating signals from the noise-compensating signal generation device to phase deviation signals from the integral discharge filter. The discrimination device outputs demodulation data by discriminating the deviation of the digital modulation signals based on the compensated phase deviation signals.

Abstract: An AM stereo broadcasting system for transmitting stereo signals in the AM broadcasting band. The system is based on amplitude modulation by two carriers having the same frequency and a 90.degree. phase difference from each other, and is capable of increasing the modulation depth of pilot signals (used for stereo signal identification) irrespective of the stereo signals, so that the pilot signals can be easily detected. By modulating both the sum and difference signals by the pilot signal, the receiver portion of the present system can derive the pilot signal irrespective of the stereo signals, thereby obviating many of the previous AM stereo broadcasting system problems.