Abstract: A large-capacity CDMA transmission system that can realize communication with a moving unit such as an automobile, transmitting more quantity of information than the conventional system without increasing the occupied band width, using the same or narrower frequency band width. This system assumes the code division multiple access (CDMA) transmission system for simultaneous multiple communication, which performs phase modulation on a carrier signal while maintaining a phase of the carrier signal in a predetermined period at a predetermined value, so as to generate a primary modulated wave, and then, multiplies the obtained primary modulated wave by a spread code sequence. On the transmitting side, a differential coding phase modulation (DPSK) is employed to generate a primary modulated wave.

Abstract: A wireless transmitter for PM (phase modulation) signal with a spectrum scrambler for relocation of input spectrum for privacy purposes is comprised of a differential circuit coupled with an input terminal, a spectrum scrambler coupled with output of said differential circuit, and FM (frequency modulation) modulator coupled with output of the spectrum scrambler. Due to the position of the differential circuit before the spectrum scrambler, modulation index of modulated PM signal and/or the frequency band of the modulated PM signal does not increase irrespective of spectrum scrambling.

Abstract: A wireless receiver for a PM (phase modulation) signal with a spectrum scrambling for relocation of speech spectrums for the privacy of purpose is comprised of an antenna for receiving PM modulated signals, an FM demodulator coupled with the antenna, a spectrum de-scrambler connected to output of the FM demodulator, an integration circuit connected to output of said spectrum de-scrambler, and an output terminal coupled with output of the integration circuit. Due to the location of the de-scrambler between the FM demodulator and the integration circuit, a noise spectrum of a reception signal is independent from a design of spectrum scrambling, and an excellent substantial S/N is obtained irrespective of spectrum scrambling.