Digital differential angle demodulator

Claim 2

In a data transmission system for sending digital data between a transmitter and a receiver over a transmitting link by establishing predetermined multiples of a given phase amount in a carrier signal during successive modulation periods representative of preselected data combinations, the modulated carrier signal being converted at the receiver to a high frequency signal having the same phase relationship between adjacent modulation periods as the modulated carrier signal, a demodulator at the receiver for detecting said phase differences which comprises: counting means for producing a counter output signal having one portion indicative of multiples of said predetermined phase differences and another portion variable about a signal value indicative of a phase amount less than said given phase amount; comparing means responsive to the high frequency signal during a preselected portion of each modulation period for comparing said one portion of the output signal from the counting means obtained during one modulation period with said one portion obtained during an adjacent modulation period to provide an output signal representative of the phase difference multiple between the modulated high frequency signal present during said adjacent modulation periods; and means responsive to said variable portion of said counter output signal for synchronizing a preselected portion of said high frequency signal with said counter output value.

Claim 3

The demodulator as defined in claim 1 wherein said synchronizing means comprises means for selectively advancing or retarding said counting means to vary the variable portion of the output signal of said counting means.

Claim 4

The demodulator as defined in claim 2 wherein the signal value of said variable portion corresponds to odd multiples of one-half of said given phase difference amount.

Claim 5

The demodulator of claim 3 wherein the counting means is a high speed binary counter having a pluralitY of output stages each capable of assuming a first or second state and at least one stage of which corresponds to a phase value representing one-half of said given phase difference amount when said stage is in said first state.

Claim 6

The demodulator of claim 4 wherein the synchronizing means comprises a phase locked loop having: sensing means responsive to the phase of the high frequency signal during the preselected portion of each modulation period for providing an output signal indicative of the state of said at least one stage; and means responsive to the output signal of said sensing means for selectively advancing or retarding said high speed binary counter whereby the state of said at least one stage varies from said first to said second state to maintain synchronism with the phase of the high frequency signal.

Claim 7

The demodulator of Claim 5 wherein the comparing means comprises: a first binary signal storage register; a second binary signal storage register; a parallel adder for signals from said first and second registers; means for applying to said first storage register, from the most significant stages of the binary counter, said one portion of the counter output signal in response to the phase of the high frequency signal appearing during the preselected portion of one modulation period; means for transferring the signal in said first storage register to the second storage register before said signal applying means stores said one portion of the counter output signal in said first register during the next upcoming modulation period; and means for applying the signals stored in said first and second storage registers to said parallel adder to obtain an adder output representative of the phase difference between the signals from said first and said second storage registers.

Claim 8

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing phase differences of 360/N degrees (where N is a number greater than one) in a carrier signal during successive modulation periods representative of preselected data combinations, the modulated carrier signal being converted at the receiver to a high frequency signal having phase relationships between adjacent modulation periods related to the carrier signal phase relationships, a demodulator at the receiver for detecting the phase differences which comprises: means at the receiver responsive to the envelope of the carrier signal for deriving a clock signal in synchronism with the modulation periods of the carrier signal; means at the receiver responsive to the clock signal for generating a sample signal at substantially the center of each modulation period; counting means at the receiver for producing an output signal which includes a first and second portion, the first portion indicating multiples of 360/N degrees and said second portion being variable about an angular amount that is related to said 360/N degrees; comparing means at the receiver responsive to the high frequency signal and to the sample signal for comparing the first portions of the output signal of the counting means during successive modulation periods, said comparing means emitting an output signal which is a measure of the phase difference between compared signals; and means responsive to the second portion of the output signal of said counting means during each modulation period for phase locking the high frequency signal to said related angular amount of said second portion of output signal of said counting means.

Claim 9

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing phase differences of 360/N degrees (where N is a number greater than one) in a carrier signal during successive modulation periods representative of preselected data combinations, the modulated carrier signal being converted at the receiver to a high frequency signal having phase relationships between adjacent modulation periods related to the carrier signal phase relationships, a demodulator at the receiver for detecting the phase differences which comprises: means at the receiver responsive to the envelope of the carrier signal for deriving a clock signal in synchronism with the modulation periods of the carrier signal; means at the receiver responsive to the clock signal for generating a sample signal at substantially the center of each modulation period; counting means at the receiver for producing an output signal which includes a first and second portion, the first portion indicating multiples of 360/N degrees and said second portion being variable about an angular amount that is related to said 360/N degrees; comparing means at the receiver responsive to the high frequency signal and to the sample signal for comparing the first portions of the output signal of the counting means during successive modulation periods, said comparing means emitting an output signal which is a measure of the phase difference between compared signals; and means responsive to the second portion of the output signal of said counting means during each modulation period for phase locking the high frequency signal to said related angular amount of said second portion of output signal of said counting means.

Claim 10

The demodulator as defined in claim 7 wherein the related angular amount corresponds to odd multiples of 360/2N degrees.

Claim 11

The demodulator as defined in claim 8 wherein said phase locking means comprises means for selectively advancing or retarding the second portion of the output signal of said counting means as a function of the relation of the time of oCcurrence of the high frequency signal with the presence or absence of said related angular amount from said counting means.

Claim 12

The demodulator of claim 8 wherein N is equal to eight.

Claim 13

A data transmission system having a transmitting and receiving device connectable together by a signal transmission link, said system comprising: means at the transmitting device for generating a carrier signal having predetermined multiples of a given phase difference during successive modulation periods; a demodulator at the receiving device for sampling the phase of the received signal at a predetermined portion of each successive modulation period; means at the receiver associated with said demodulator for emitting a reference signal having a plurality of predetermined phase values with one output phase being half of the phase difference utilized at said transmitting device; and phase locking means connected between said signal generator and said demodulator whereby said data containing portion of said received carrier signal is locked to an odd multiple of the value of said one output phase.

Claim 14

A data transmission system having a transmitting and receiving device connectable together by a signal transmission link, said system comprising: means at the transmitting device for generating a carrier signal having predetermined multiples of a given phase difference during successive modulation periods; a demodulator at the receiving device for sampling the phase of the received signal at a predetermined portion of each successive modulation period; means at the receiver associated with said demodulator for emitting a reference signal having a plurality of predetermined phase values with one output phase being half of the phase difference utilized at said transmitting device; and phase locking means connected between said signal generator and said demodulator whereby said data containing portion of said received carrier signal is locked to an odd multiple of the value of said one output phase.

Claim 15

The system of claim 11 wherein said phase locking means comprises means for selectively advancing or retarding said reference signal in response to a preselected number of said sampled phases.

Claim 18

A method in accordance with claim 13 further defined in that said step of locking the signals comprises: locking the phase present in said preselected portions to a phase value representing an odd multiple of one half the given phase difference.

Claim 21

A method in accordance with claim 13 further defined in that said step of locking the signals comprises: locking the signals in said preselected portion to reference signals approximately representing odd multiples of one half the minimum difference of the preselected phase values.

Claim 22

In a data transmission system for sending digital data between a transmitter and receiver over a transmission link wherein the digital data is represented by a carrier signal which is differentially phase modulated by predetermined multiples of a given angular amount during successive modulation periods in accordance with information to be transmitted, a demodulator at the receiver which comprises: a pulse counter driven at a fixed repetition rate and having a readout signal with certain portions of the signal bEing indicative of various multiples of said given phase angular amount and having another portion thereof being indicative of a phase angular amount other than said given angular amount, said counter including means responsive to a counter varying signal for altering said other signal portion and thus the phase of said other phase angular amount represented thereby; means for generating a sample signal during a precise portion of each successive modulation period, which portions each coincide with the phase of the carrier that represents the phase modulated information to be sampled during such modulation periods; and signal applying means connected between said counter varying means and responsive to said other signal portion for phase locking the carrier signal occurring during said precise portions with said other phase angular amount of the signal from said counting means.

Claim 23

In a data transmission system for sending digital data between a transmitter and receiver over a transmission link wherein the digital data is represented by a carrier signal which is differentially phase modulated by predetermined multiples of a given angular amount during successive modulation periods in accordance with information to be transmitted, a demodulator at the receiver which comprises: a pulse counter driven at a fixed repetition rate and having a readout signal with certain portions of the signal bEing indicative of various multiples of said given phase angular amount and having another portion thereof being indicative of a phase angular amount other than said given angular amount, said counter including means responsive to a counter varying signal for altering said other signal portion and thus the phase of said other phase angular amount represented thereby; means for generating a sample signal during a precise portion of each successive modulation period, which portions each coincide with the phase of the carrier that represents the phase modulated information to be sampled during such modulation periods; and signal applying means connected between said counter varying means and responsive to said other signal portion for phase locking the carrier signal occurring during said precise portions with said other phase angular amount of the signal from said counting means.

Claim 24

A demodulator in accordance with claim 17 wherein said other signal portion of said counting means includes: a plurality of increasing predetermined angular amounts which sum together to total said given angular amount; and wherein said signal applying means includes: means connected to monitor one of said plurality of angular amounts as a reference for phase locking the carrier signal to the monitored one of said angular amounts.

Claim 25

A demodulator in accordance with claim 18 wherein the monitored angular amount is substantially one-half the given phase difference and wherein said signal applying means includes means for either adding or subtracting pulses from said counting means during every modulation period.

Claim 26

A demodulator in accordance with claim 19 wherein said signal adding and/or subtracting means is only operative following the repeated presence and/or repeated absence of said monitored angular amount during a given number of successive modulation periods.

Claim 27

In a system wherein digital data is represented by a carrier signal which is differentially phase modulated by multiples of a predetermined angular amount during successive modulation periods, a demodulator comprising: counting means for producing an output signal having a first portion indicative of multiples of said predetermined angular amount, and a second portion indicative of an angular amount less than said predetermined angular amount, said counting means being variable for varying said second portion of said output signal about said lesser phase amount; means responsive to receipt of the carrier signal for generating a sample signal during each modulation period; comparing means responsive to the phase of the modulated carrier signal and to the sample signal for comparing the first portion of said output signal of the counting means during successive modulation periods to provide an output signal which is a measure of the phase difference between the modulated signals occurring at adjacent modulation periods; and means responsive to the second portion of said output signal of said counting means and to the phase of said carrier during the presence of said sample signal for varying said counting means into phase locking relation between said carrier signal and said lesser angular amount.

Claim 28

In a system wherein digital data is represented by a carrier signal which is differentially phase modulated by multiples of a predetermined angular amount during successive modulation periods, a demodulator comprising: counting means for producing an output signal having a first portion indicative of multiples of said predetermined angular amount, and a second portion indicative of an angular amount less than said predetermined angular amount, said counting means being variable for varying said second portion of said output signal about said lesser phase amount; means responsive to receipt of the carrier signal for generating a sample signal during each modulation period; comparing means responsive to the phase of the modulated carrier signal and to the sample signal for comparing the first portion of said output signal of the counting means during successive modulation periods to provide an output signal which is a measure of the phase difference between the modulated signals occurring at adjacent modulation periods; and means responsive to the second portion of said output signal of said counting means and to the phase of said carrier during the presence of said sample signal for varying said counting means into phase locking relation between said carrier signal and said lesser angular amount.