Abstract: A modulator in which an input train of digital pulses is encoded to produce two encoded trains of digital pulses which are used to respectively modulate two out of phase carrier components. The two modulated carrier components are combined to produce a modulated output signal. A demodulator recovers carrier and clock signals from the modulated signal and combines these with the modulated signal to recover the input train of digital pulses.

Abstract: Frequency modulators for use in microwave link transmission systems include acoustic surface wave (ASW) oscillators. Each frequency modulator comprises two voltage control quadripole ASW oscillators. Control inputs of the two ASW oscillators receive modulation signal in opposite phase. Outputs of ASW oscillators are mixed in a mixer for delivering an IF signal. Thus frequency deviation is larger than in a conventional arrangement. Moreover, surface wave oscillators make it possible to directly insert a service channel signal in a microwave link repeater, without demodulation and modulation operations.

Abstract: A four phase staggered phase shift keying modulator system having means to modulate a voltage controlled oscillator generating the carrier by positive or negative pulses of a predetermined duration to shift the phase of the carrier by +90.degree. or -90.degree., the positive or negative being produced by individual coding of a series of applied pulses.