Differential quadrature phase shift keying encoder for subcarrier systems

Claim 1

An apparatus, comprising at least one encoder for encoding a pair of synchronous binary input data streams S 0 (t), S 1 (t), into a pair of encoded binary data streams d 0 (t), d 1 (t), each said input data stream having a single bit period T between successive data bits; said encoder further including a first time delay circuit for delaying d 0 (t) by a period T to produce a first time-delayed encoded signal d 0 (t-T); a second time delay circuit for delaying d 1 (t) by a period T to produce a second time-delayed encoded signal d 1 (t-T); and a logic circuit for producing encoded signals d 0 (t) and d 1 (t) from S 0 (t), S 1 (t), d 0 (t-T), and d 1 (t-T) according to the logical relationships: d.sub.0 (t)=S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T) and d.sub.1 (t)=S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T). at least one QPSK modulator for modulating with the encoded signals d 0 and d 1 the phase φ(t) of at least one carrier signal having a frequency f and an amplitude A, said modulated carrier signal being given by x(t)=A cos(2πft+φ(t)); wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d 0 (t) and d 1 (t), and said encoder encodes d 0 (t) and d 1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.0 (t)=1, cos{Δφ-45°}<0 for S.sub.0 (t)=0, cos{Δφ+45°}>0 for S.sub.1 (t)=1, and cos{Δφ+45°}<0 for S.sub.1 (t)=0 where Δφ=φ(t)-φ(t).

Claim 2

An apparatus, comprising at least one encoder for encoding a pair of synchronous binary input data streams S 0 (t), S 1 (t), into a pair of encoded binary data streams d 0 (t), d 1 (t), each said input data stream having a single bit period T between successive data bits; said encoder further including a first time delay circuit for delaying d 0 (t) by a period T to produce a first time-delayed encoded signal d 0 (t-T); a second time delay circuit for delaying d 1 (t) by a period T to produce a second time-delayed encoded signal d 1 (t-T); and a logic circuit for producing encoded signals d 0 (t) and d 1 (t) from S 0 (t), S 1 (t), d 0 (t-T), and d 1 (t-T) according to the logical relationships: d.sub.0 (t)=S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T) and d.sub.1 (t)=S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.0 (t-T)+S.sub.0 (t) S.sub.1 (t) d.sub.1 (t-T). at least one QPSK modulator for modulating with the encoded signals d 0 and d 1 the phase φ(t) of at least one carrier signal having a frequency f and an amplitude A, said modulated carrier signal being given by x(t)=A cos(2πft+φ(t)); wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d 0 (t) and d 1 (t), and said encoder encodes d 0 (t) and d 1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.0 (t)=1, cos{Δφ-45°}<0 for S.sub.0 (t)=0, cos{Δφ+45°}>0 for S.sub.1 (t)=1, and cos{Δφ+45°}<0 for S.sub.1 (t)=0 where Δφ=φ(t)-φ(t).

Claim 14

An apparatus, comprising an encoder for encoding a pair of synchronous binary input data streams S m ,0 (t), S m ,1 (t) associated with said subcarrier at f m , each said input data stream having a single bit period T between successive data bits, into a pair of encoded binary data streams d m ,0 (t), d m ,1 (t); said encoder further including a first time delay circuit for delaying d m ,0 (t) by a period T to produce a first time-delayed encoded signal d m ,0 (t-T); a second time delay circuit for delaying d m ,1 (t) by a period T to produce a second time-delayed encoded signal d m ,1 (t-T); and said each said encoder further including means to enable d m ,0 (t) and d m ,1 (t) to satisfy the logical relationships ##EQU8## a plurality of microwave subcarrier QPSK modulators each associated with a microwave subcarrier signal for modulating with the encoded binary data streams d m ,0 (t), d m ,1 (t) the phase φ m (t) of the associated microwave subcarrier having a frequency f m and an amplitude A m , where m is the index number of the microwave subcarrier, each said modulated subcarrier signal being given by x.sub.m (t)=A.sub.m cos(2πf.sub.m t+φ(t)); wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d m ,0 (t) and d m ,1 (t), and said encoder encodes d m ,0 (t) and d m ,1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.m,0 (t)=1, cos{Δφ-45°}<0 for S.sub.m,0 (t)=0, cos{Δφ-45°}>0 for S.sub.m,1 (t)=1, and cos{Δφ-45°}<0 for S.sub.m,1 (t)=0 where Δφ m =φ m (t)-φ m (t).

Claim 15

An apparatus, comprising an encoder for encoding a pair of synchronous binary input data streams S m ,0 (t), S m ,1 (t) associated with said subcarrier at f m , each said input data stream having a single bit period T between successive data bits, into a pair of encoded binary data streams d m ,0 (t), d m ,1 (t); said encoder further including a first time delay circuit for delaying d m ,0 (t) by a period T to produce a first time-delayed encoded signal d m ,0 (t-T); a second time delay circuit for delaying d m ,1 (t) by a period T to produce a second time-delayed encoded signal d m ,1 (t-T); and said each said encoder further including means to enable d m ,0 (t) and d m ,1 (t) to satisfy the logical relationships ##EQU8## a plurality of microwave subcarrier QPSK modulators each associated with a microwave subcarrier signal for modulating with the encoded binary data streams d m ,0 (t), d m ,1 (t) the phase φ m (t) of the associated microwave subcarrier having a frequency f m and an amplitude A m , where m is the index number of the microwave subcarrier, each said modulated subcarrier signal being given by x.sub.m (t)=A.sub.m cos(2πf.sub.m t+φ(t)); wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d m ,0 (t) and d m ,1 (t), and said encoder encodes d m ,0 (t) and d m ,1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.m,0 (t)=1, cos{Δφ-45°}<0 for S.sub.m,0 (t)=0, cos{Δφ-45°}>0 for S.sub.m,1 (t)=1, and cos{Δφ-45°}<0 for S.sub.m,1 (t)=0 where Δφ m =φ m (t)-φ m (t).

Claim 23

An apparatus for transferring digital data across an optical data link, comprising an encoder for encoding a first input data signal S 0 and a second input data signal S 1 into a first encoded signal d 0 and second encoded signal d 1 , said first and second input data signals being synchronous with each other and having the same single bit time period T between successive data bits; said encoder further includes a first time delay circuit for delaying d 0 by a period T to produce a first time-delayed encoded signal d' 0 ; a second time delay circuit for delaying d 1 by a period T to produce a second time-delayed encoded signal d' 1 ; and a logic circuit for producing encoded signals d 0 and d 1 from S 0 , S 1 , d' 0 and d' 1 according to the boolean expressions: d.sub.0 =S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 and, d.sub.1 =S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 ; at least one subcarrier modulator for simultaneously modulating an associated subcarrier with said first and second encoded signals to produce a modulated subcarrier signal that contains two bits of information for each symbol period, said symbol period equal to said bit period T of each said input data signals S 0 and S 1 ; an optical modulator for modulating at least one said modulated subcarrier signal on an optical carrier signal; an optical detector for detecting at least one said subcarrier from said optical carrier signal to provide a detected subcarrier signal; and a demodulator for demodulating said first input data signal from said detected subcarrier signal.

Claim 24

An apparatus for transferring digital data across an optical data link, comprising an encoder for encoding a first input data signal S 0 and a second input data signal S 1 into a first encoded signal d 0 and second encoded signal d 1 , said first and second input data signals being synchronous with each other and having the same single bit time period T between successive data bits; said encoder further includes a first time delay circuit for delaying d 0 by a period T to produce a first time-delayed encoded signal d' 0 ; a second time delay circuit for delaying d 1 by a period T to produce a second time-delayed encoded signal d' 1 ; and a logic circuit for producing encoded signals d 0 and d 1 from S 0 , S 1 , d' 0 and d' 1 according to the boolean expressions: d.sub.0 =S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 and, d.sub.1 =S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 ; at least one subcarrier modulator for simultaneously modulating an associated subcarrier with said first and second encoded signals to produce a modulated subcarrier signal that contains two bits of information for each symbol period, said symbol period equal to said bit period T of each said input data signals S 0 and S 1 ; an optical modulator for modulating at least one said modulated subcarrier signal on an optical carrier signal; an optical detector for detecting at least one said subcarrier from said optical carrier signal to provide a detected subcarrier signal; and a demodulator for demodulating said first input data signal from said detected subcarrier signal.

Claim 34

An apparatus for receiving digital data from an optical data link, comprising an optical detector for detecting at least one subcarrier from a subcarrier modulated optical carrier signal to provide a detected subcarrier signal; and a demodulator for demodulating a first data signal and a second data signal from said detected subcarrier signal, said demodulator comprising (a) a phase delay network for delaying the phase of said detected subcarrier by a predetermined phase delay and providing a phase-delayed detected subcarrier; (b) a phase advance network for advancing the phase of said detected subcarrier by a predetermined phase advance and providing a phase-advanced detected subcarrier, said predetermined phase delay and said predetermined phase advance each being selected such that the resulting phase difference between said phase-delayed detected subcarrier and said phase-advanced detected subcarrier is substantially 90°; (c) a time delay circuit for delaying said detected subcarrier by said single bit time period T to provide a time-delayed detected subcarrier; (d) a first demodulation mixer for mixing said phase-delayed detected subcarrier with said time-delayed detected subcarrier; and (e) a second demodulation mixer for mixing said phase-advanced detected subcarrier with said time-delayed detected subcarrier.

Claim 35

An apparatus for receiving digital data from an optical data link, comprising an optical detector for detecting at least one subcarrier from a subcarrier modulated optical carrier signal to provide a detected subcarrier signal; and a demodulator for demodulating a first data signal and a second data signal from said detected subcarrier signal, said demodulator comprising (a) a phase delay network for delaying the phase of said detected subcarrier by a predetermined phase delay and providing a phase-delayed detected subcarrier; (b) a phase advance network for advancing the phase of said detected subcarrier by a predetermined phase advance and providing a phase-advanced detected subcarrier, said predetermined phase delay and said predetermined phase advance each being selected such that the resulting phase difference between said phase-delayed detected subcarrier and said phase-advanced detected subcarrier is substantially 90°; (c) a time delay circuit for delaying said detected subcarrier by said single bit time period T to provide a time-delayed detected subcarrier; (d) a first demodulation mixer for mixing said phase-delayed detected subcarrier with said time-delayed detected subcarrier; and (e) a second demodulation mixer for mixing said phase-advanced detected subcarrier with said time-delayed detected subcarrier.

Claim 37

A method of modulating a carrier signal with digital information, comprising the steps of encoding a pair of synchronous binary input data streams S 0 , S 1 , into a pair of encoded binary data streams d 0 , d 1 , each said input stream having a single bit period between T between successive data bits; delaying d 0 by a period T to produce a first time-delayed encoded signal d' 0 ; delaying d 1 by a period T to produce a second time-delayed encoded signal d' 1 ; and producing encoded signals d 0 and d 1 from S 0 , S 1 , d' 0 and d' 1 according to the boolean expressions: d.sub.0 =S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 and, d.sub.1 =S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 ; modulating the phase φ(t) of at least one carrier signal having a frequency f and an amplitude A, said modulated carrier signal being given by x(t)=A cos(2πft+φ(t) wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d 0 (t) and d 1 (t) and said encoder encodes d 0 (t) and d 1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.0 (t)=1, cos{Δφ-45°}<0 for S.sub.0 (t)=0, cos{Δφ-45°}>0 for S.sub.1 (t)=1, and cos{Δφ-45°}<0 for S.sub.1 (t)=0; where Δφ=φ(t)-φ(t).

Claim 38

A method of modulating a carrier signal with digital information, comprising the steps of encoding a pair of synchronous binary input data streams S 0 , S 1 , into a pair of encoded binary data streams d 0 , d 1 , each said input stream having a single bit period between T between successive data bits; delaying d 0 by a period T to produce a first time-delayed encoded signal d' 0 ; delaying d 1 by a period T to produce a second time-delayed encoded signal d' 1 ; and producing encoded signals d 0 and d 1 from S 0 , S 1 , d' 0 and d' 1 according to the boolean expressions: d.sub.0 =S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 and, d.sub.1 =S.sub.0 S.sub.1 d'.sub.1 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.0 +S.sub.0 S.sub.1 d'.sub.1 ; modulating the phase φ(t) of at least one carrier signal having a frequency f and an amplitude A, said modulated carrier signal being given by x(t)=A cos(2πft+φ(t) wherein said phase φ(t) is determined by the logical values of said encoded binary data streams d 0 (t) and d 1 (t) and said encoder encodes d 0 (t) and d 1 (t) to satisfy the relationships cos{Δφ-45°}>0 for S.sub.0 (t)=1, cos{Δφ-45°}<0 for S.sub.0 (t)=0, cos{Δφ-45°}>0 for S.sub.1 (t)=1, and cos{Δφ-45°}<0 for S.sub.1 (t)=0; where Δφ=φ(t)-φ(t).