Digital demodulator for phase-modulated data transmission systems

Claim 2

In a synchronous differentially coherent phase-modulation data transmission system a demodulator at the receiver therefor comprising means for detecting transitions in a received signaling wave whose changes in phase between synchronous signaling intervals encode data, a high-frequency counter whose full count is coextensive with one cycle of said signaling wave, means responsive to said transition detecting means for resetting said counter to a reference condition at a predetermined portion of each signaling interval, and means for reading out the state of said counter just prior to the operation of said resetting means as a measure of the phase change in said signaling wave between signaling intervals.

Claim 3

The demodulator defined in claim 1 in combination with means for translating said received signaling wave to a relatively high intermediate frequency to provide a plurality of zero-crossing transitions for each signaling interval.

Claim 4

The demodulator defined in claim 1 and means for interrupting the operation of said counter prior to resetting for a preselected interval to facilitate readout.

Claim 5

The demodulator defined in claim 1 in which said counter comprises a precision oscillator of fixed frequency harmonically related by an integral power of two to the frequency of said signaling wave and a multistage binary frequency divider in tandem with said oscillator.

Claim 6

The demodulator defined in claim 1 in which said resetting means discriminates between positive- and negative-going transitions in said signaling wave and inverts the most significant output of said counter upon readout responsive to a preselected transition polarity.

Claim 7

In a data transmission system which encodes digital data as discrete phase differences between successive signaling intervals of a carrier wave, a receiver comprising means for translating said carrier wave to an intermediate-frequency wave providing a plurality of zero-crossing transitions for each signaling interval; means for detecting the instant of occurrence and polarity of zero-crossing transitions in said intermediate-frequency wave at a preselected sampling time within each signaling interval; means for generating a high-frequency wave whose frequency is harmonicallY related to said intermediate frequency by a power of two; a binary counter having a plurality of stages each capable of assuming a first and second state, the condition of the terminal stage of said counter corresponding to inversions of said phase differences; means normally gating said generating means to said binary counter; means operative at said sampling times to disable said gating means for a predetermined interval; register means capable of storing the states of a plurality of stages of said binary counter; means operative at said sampling times and responsive to the polarity of the transition in said intermediate-frequency wave for transferring the actual condition or the binary complement thereof from said binary counter to said register means; and means operative at said sampling times to reset said counter to a reference condition and to enable said gating means.

Claim 8

In a data transmission system which encodes digital data as discrete phase differences between successive signaling intervals of a carrier wave, a receiver comprising means for translating said carrier wave to an intermediate-frequency wave providing a plurality of zero-crossing transitions for each signaling interval; means for detecting the instant of occurrence and polarity of zero-crossing transitions in said intermediate-frequency wave at a preselected sampling time within each signaling interval; means for generating a high-frequency wave whose frequency is harmonicallY related to said intermediate frequency by a power of two; a binary counter having a plurality of stages each capable of assuming a first and second state, the condition of the terminal stage of said counter corresponding to inversions of said phase differences; means normally gating said generating means to said binary counter; means operative at said sampling times to disable said gating means for a predetermined interval; register means capable of storing the states of a plurality of stages of said binary counter; means operative at said sampling times and responsive to the polarity of the transition in said intermediate-frequency wave for transferring the actual condition or the binary complement thereof from said binary counter to said register means; and means operative at said sampling times to reset said counter to a reference condition and to enable said gating means.

Claim 9

In a synchronous differentially coherent phase-modulation data transmission system the method of demodulating the received data signal wave comprising the steps of detecting transitions in said received data signal wave whose changes in phase between signaling intervals encode data, continuously generating a repetitive counting sequence whose length is coextensive with one cycle of said signal wave, interrupting said counting sequence at a predetermined portion of each signaling interval, recording the state of said counting sequence immediately following said interruption, and resetting said counting sequence to a reference condition at the termination of said predetermined portion of each signaling interval.

Claim 10

In a synchronous differentially coherent phase-modulation data transmission system the method of demodulating the received data signal wave comprising the steps of detecting transitions in said received data signal wave whose changes in phase between signaling intervals encode data, continuously generating a repetitive counting sequence whose length is coextensive with one cycle of said signal wave, interrupting said counting sequence at a predetermined portion of each signaling interval, recording the state of said counting sequence immediately following said interruption, and resetting said counting sequence to a reference condition at the termination of said predetermined portion of each signaling interval.

Claim 11

The method of claim 7 including a further preliminary step of translating the frequency of the baseband wave on which data signals were originally encoded to a higher intermediate frequency to increase substantially the numbers of transitions for each signaling interval in said data signal wave.