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Class Information
Number: 375/281
Name: Pulse or digital communications > Systems using alternating or pulsating current > Angle modulation > Phase shift keying > More than two phases > Quaternary
Description: Subject matter where the phases are 90 degrees apart.

Patents under this class:
1 2 3

Patent Number Title Of Patent Date Issued
5361047 PI/4 shift QPSK modulator and communication apparatus used therewith Nov. 1, 1994
5315583 Method and apparatus for digital audio broadcasting and reception May. 24, 1994
5289503 Method and circuit arrangement for producing a QPSK signal on which a carrier signal is superposed Feb. 22, 1994
5274669 Signal equalizing method employing test sequences Dec. 28, 1993
5222103 Differential quadrature phase shift keying encoder for subcarrier systems Jun. 22, 1993
5179578 Coherent demodulator for .pi./4 shifted QPSK signal Jan. 12, 1993
5157693 Digital modulation circuit Oct. 20, 1992
5122765 Direct microwave modulation and demodulation device Jun. 16, 1992
5084903 Modulation and demodulation system employing AM-PSK and QPSK communication system using digital signals Jan. 28, 1992
4980687 Digital demodulator Dec. 25, 1990
4939734 Method and a system for coding and decoding data for transmission Jul. 3, 1990
4897620 Continuous phase shift modulation system with improved spectrum control Jan. 30, 1990
4873683 TDMA radio system employing BPSK synchronization for QPSK signals subject to random phase variation and multipath fading Oct. 10, 1989
RE33056 Signal structures for double side band-quadrature carrier modulation Sep. 12, 1989
4821097 Apparatus and method for providing digital audio on the sound carrier of a standard television signal Apr. 11, 1989
4807251 PSK modem system with improved demodulation reliability Feb. 21, 1989
4786882 Quadriphase phase modulation system Nov. 22, 1988
4756008 Digitized quadrature phase shift keying modulator Jul. 5, 1988
4691318 Data transmission system with error correcting data encoding Sep. 1, 1987
4682343 Processing circuit with asymmetry corrector and convolutional encoder for digital data Jul. 21, 1987
4680775 Device for coding-decoding a binary digital signal bit stream for an "OQPSK" digital modulator-demodulator with four phase states Jul. 14, 1987
4675880 Antimultipath communication by injecting tone into null in signal spectrum Jun. 23, 1987
4613976 Constant envelope offset QPSK modulator Sep. 23, 1986
4612518 QPSK modulator or demodulator using subharmonic pump carrier signals Sep. 16, 1986
4606051 QPSK demodulator with I and Q post-detection data correction Aug. 12, 1986
4599735 Timing recovery circuit for synchronous data transmission using combination of L Bi phase and modified biphase codes Jul. 8, 1986
4586023 Means and method for data transmission on wired channels Apr. 29, 1986
4584693 QPSK system with one cycle per Baud period Apr. 22, 1986
4481640 Spread spectrum modem Nov. 6, 1984
4468784 Three-state digital mixer-driver circuit Aug. 28, 1984
4462001 Baseband linearizer for wideband, high power, nonlinear amplifiers Jul. 24, 1984
4385401 Three-state digital mixer-driver circuit May. 24, 1983
4377791 Phase displacement modulator having four quadrant phases Mar. 22, 1983
4327439 Method for generating modem transmission signals with quadrature amplitude modulation Apr. 27, 1982
4291277 Adaptive predistortion technique for linearizing a power amplifier for digital data systems Sep. 22, 1981
4290143 Transmission method and apparatus wherein binary data bits are converted into barker words and vice versa Sep. 15, 1981
4285062 Digital multi-level multi-phase modulation communication system Aug. 18, 1981
4267591 QPSK Suppressed carrier with rotating reference phase May. 12, 1981
4244047 Multiplexed carrier transmission through harmonic polluted medium Jan. 6, 1981
4231094 Method and device for determining the phase intercept in a system employing phase-shift keying modulation Oct. 28, 1980
4109100 Reverberation compensating communication system Aug. 22, 1978
4099121 Spatial diversity satellite communications system with error control Jul. 4, 1978
4041391 Pseudo noise code and data transmission method and apparatus Aug. 9, 1977
4035767 Error correction code and apparatus for the correction of differentially encoded quadrature phase shift keyed data (DQPSK) Jul. 12, 1977
3980945 Digital communications system with immunity to frequency selective fading Sep. 14, 1976
3978406 Code error detecting system in digital code transmission Aug. 31, 1976
3939407 Plural channel communications system Feb. 17, 1976
3931472 Asynchronous quadriphase communications system and method Jan. 6, 1976

1 2 3

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