GB1312991A - Phase detection system for at least one digital phase modulated wave - Google Patents

Abstract

1312991 Phase modulated transmission systems KOKUSAI DENSHIN DENWA KK 10 July 1970 [10 July 1969 12 Sept 1969] 33546/70 Heading H4P In a phase modulation detection system adaptable to either differential or absolute phase detection, products of a phase-modulated signal with each of two reference carrier waves of the same frequency and a phase difference of 90 degrees are produced, so that a function of the phase difference phase modulated signal and one of the reference waves is found by integrating respectively the two products or by passing the two products through respective low-pass filters to perform phase detection. The phase position of each signal element of the phase-modulated signal may be temporarily stored which is replaced by an immediately succeeding signal element similarly detected by the phase difference between two successive elements. A plurality of phase modulated signals can be phase detected in a time division manner. An oscillator employed for generating reference carriers need not be stabilized. Input phase modulated signals are fed to modulators 4-1, 4-2 which also receive respectively a reference wave fa and a 90 degree phaseshifted wave fb giving a product output which is passed to integrators 5-1, 5-2 which are reset in each half bit period of carrier frequency by signals applied to terminals 5-0. Integrator outputs are sampled and applied to converters 7, 8 which compare the outputs from the samplers and the difference in successive samplings being stored in memory 9, difference in successive samplings being passed to a decoder 11. Detailed arrangements for providing the various functions are described in the Specification.