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Browse by Category: Main > Communications
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
6606357 Carrier injecting waveform-based modulation scheme for reducing satellite transponder power requirements and earth terminal antenna size Aug. 12, 2003
6594320 Orthogonal Frequency Division Multiplexed (OFDM) carrier acquisition method Jul. 15, 2003
6590945 Method and apparatus for frequency offset compensation Jul. 8, 2003
6496542 Digital communication system Dec. 17, 2002
6477153 Method and apparatus for using the sidelobe of a long range antenna for a short range communication link Nov. 5, 2002
6470056 Offset QPSK modulation analytic system Oct. 22, 2002
6462679 Method and apparatus for modulating a signal Oct. 8, 2002
6445746 IS-136+ slot formation Sep. 3, 2002
6445745 Phase encoding methods for handling multiple phase modulated signals on a single channel Sep. 3, 2002
6366622 Apparatus and method for wireless communications Apr. 2, 2002
6351503 Threshold extension block phase estimator for quasi-coherent communications systems Feb. 26, 2002
6332208 Data transmitting apparatus and data transmitting method Dec. 18, 2001
6301291 Pilot symbol assisted modulation and demodulation in wireless communication systems Oct. 9, 2001
6285721 Method for assisting simple synchronization to the carrier of a dispersed-energy QPSK signal Sep. 4, 2001
6243427 Multichannel radio frequency transmission system to deliver wideband digital data into independent sectorized service areas Jun. 5, 2001
6222878 Communication system with end-to-end quadrature balance control Apr. 24, 2001
6157679 Method of adding encryption/encoding element to the modulation/demodulation process Dec. 5, 2000
6125148 Method for demodulating information in a communication system that supports multiple modulation schemes Sep. 26, 2000
5999570 Transmission apparatus, sending apparatus, and receiving apparatus, and transmission method Dec. 7, 1999
5987068 Method and apparatus for enhanced communication capability while maintaining standard channel modulation compatibility Nov. 16, 1999
5950124 Cellular communication system with dynamically modified data transmission parameters Sep. 7, 1999
5933448 Automatic tuning of a radio transceiver Aug. 3, 1999
5930299 Digital modulator with compensation and method therefor Jul. 27, 1999
5847622 Quadrature phase shift keying modulating apparatus Dec. 8, 1998
5832044 Transmitter antenna diversity and fading-resistant modulation for wireless communication systems Nov. 3, 1998
5673291 Simultaneous demodulation and decoding of a digitally modulated radio signal using known symbols Sep. 30, 1997
5668795 Modulation system for spread spectrum CDMA communiction Sep. 16, 1997
5661757 Radio-card communication system Aug. 26, 1997
5615230 Process for transmitting digital signals which combines advantages of OQPSK and .pi./4-QPSK Mar. 25, 1997
5604770 PI/4 DQPSK modulation with coarse mapper precession and fine filter precession Feb. 18, 1997
5602669 Digital signal transmission apparatus, digital signal transmission method, and digital signal transmitter-receiver Feb. 11, 1997
5598435 Digital modulation using QAM with multiple signal point constellations not equal to a power of two Jan. 28, 1997
5590155 Equipment for generating a transmit signal from first and second digital signals Dec. 31, 1996
5585761 Demodulation of digital phase modulated signal Dec. 17, 1996
5581575 Method and apparatus for transmission of variable rate digital data Dec. 3, 1996
5570388 Method and apparatus using simple codes for the wireless transmission of non-data symbols Oct. 29, 1996
5570379 Coded modulation apparatus Oct. 29, 1996
5555547 Convolutional coding and viterbi decoding system transparent to phase skips of .pi. and .pi./2, with applications in TDMA transmission Sep. 10, 1996
5550866 Digital demodulator reference signal generator having DC blocker and first Hilbert transformation with quadrature output followed by gain staging and combination for second Hilbert transformat Aug. 27, 1996
5548615 Methods and apparatus for rotationally invariant multilevel coding Aug. 20, 1996
5526381 Robust non-coherent detector for .pi./4-DQPSK signals Jun. 11, 1996
5523726 Digital quadriphase-shift keying modulator Jun. 4, 1996
5515400 Method for arranging signal points in a quadrature amplitude modulation/demodulation system May. 7, 1996
5495504 Signal generating apparatus Feb. 27, 1996
5488632 Transmission and reception in a hostile interference environment Jan. 30, 1996
5473290 Variable-throughput digital modulator and its use in FM radio broadcasting Dec. 5, 1995
5398237 Acquisition and tracking of independent quadrature modulated bitstreams Mar. 14, 1995
5379322 Baseband signal generator for digital modulator Jan. 3, 1995
5373532 .pi./4 quadrature phase shift keying modulator Dec. 13, 1994
5363410 Modulation circuit for a digital radio communications apparatus using a phase shifted DQPSK modulation system Nov. 8, 1994

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