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5524120 |
Digital low power symbol rate detector
This detector provides a computationally simple digital low power detector of symbol rate, also called baud rate. It uses an approximate Hilbert transform function to create approximate in-phase...
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5519733 |
Method and apparatus for recovering a qam carrier
A method and apparatus are provided for recovering and tracking the carrier in a QAM communication system, even under heavy interference conditions. A subset of fixed points is defined on an ideal...
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5506836 |
Orthogonal frequency division multiplex demodulation
An orthogonal frequency division multiplex (OFDM) demodulation apparatus which accurately reproduces a clock and accurately generates a time window for discrete Fourier transformation (DFT) for...
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5499273 |
Method and apparatus for symbol clock recovery from signal having wide frequency possibilities
The present invention provides an apparatus for symbol clock recovery from a received signal having wide range of frequency errors or offsets. Magnitudes of received inphase and quadrature sampled...
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5497205 |
Apparatus for processing BPSK signal transmitted with NTSC TV on quadrature-phase video
A vestigial-sideband amplitude-modulation transmitter using a balanced modulator for generating a suppressed carrier that is in quadrature phasing with the video carrier of a television signal...
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5497400 |
Decision feedback demodulator with phase and frequency estimation
A data communication receiver (10) uses a decision feedback demodulator (32) to remove data from a received signal. Quadrature components of the received signal define a received phase. The...
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5491725 |
Tracking filter and quadrature-phase reference generator
A tracking filter has a tunable filter responsive to an input signal for producing a filtered output signal, a Hilbert transformer for producing an in-phase reference signal and a quadrature-phase...
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5490176 |
Detecting false-locking and coherent digital demodulation using the same
In a method of detecting false-locking the trains of clock signals corresponding to the two phase offset initially modulated trains of signals, the phase offset between said trains of clock signals...
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5471510 |
Asynchronous transfer mode digital telecommunication network terminal equipment synchronization device
A synchronization device, in an asynchronous transfer mode digital telecommunication network terminal equipment consists of: a jitter filter for filtering transfer jitter introduced by a network of...
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5455847 |
Clock recovery phase detector
A phase detector for symbol clock recovery in a digital communications system determines the phase error of a local symbol clock from the symbol rate of a transmitted signal by sampling the...
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5425057 |
Phase demodulation method and apparatus using asynchronous sampling pulses
A method is presented for efficient VLSI implementation of a narrowband BPSK or QPSK demodulator which minimizes filter processing requirements. The demodulator implements a digital filter which...
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5412693 |
Wholly-digital demodulation system for QAM signalling in low capacity links
The present invention relates to a QAM signal demodulation system able to recover phase and frequency of the carrier and convert the signal to baseband, and to perform these functions when...
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5377232 |
Frequency synchronized bidirectional radio system
A bidirectional radio system for low cost, high through-put accumulation of data from a large number of site units. The site units are connected to remote radio transceivers in radio communication...
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5371761 |
Transmission system and receiver for this system
Receiver (105) for signals transmitted according to an orthogonal frequency division multiplexing technique with carriers distributed symmetrically around a centre frequency f e , said receiver...
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5329242 |
Method and apparatus for signal demodulation using time-intervals
Method and apparatus for recovering a message signal from a carrier signal. More specifically, method and apparatus for demodulating a frequency modulated signal using measured time intervals...
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5278514 |
MSK demodulator using one synchronous detector
An MSK signal demodulating circuit including a carrier reproducing circuit for reproducing a carrier phase-synchronized with a component of a mark frequency or a space frequency of an MSK signal, a...
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5271041 |
Method and apparatus for QPR carrier recovery
A digital audio communication system includes a digital modulation and demodulation scheme which efficiently uses the bandwidth and channel spacing of a cable television system. A 30 channel...
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5268647 |
Method and arrangement of coherently demodulating PSK signals using a feedback loop including a filter bank
In order to coherently demodulate an incoming multi-phase PSK analog signal irrespective of large frequency deviation, an automatic frequency feedback loop is provided. An analog baseband signal is...
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5249204 |
Circuit and method for phase error correction in a digital receiver
A digital receiver, such as "C-QUAM" receiver (10), has phase error correction. In another form, a software program may be executed by a conventional digital signal processor to also implement...
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5247543 |
Carrier aquisition apparatus for digital satellite communication system
A time division PLL is composed of a complex multiplier (1), a phase difference detector (2), a low-pass filter (3), an adder (4) and a digital VCO (5). A D.C. value indicating the recovered...
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5228060 |
Control unit for controlling modem used in receiver
A control unit for controlling a modem used in a receiver demodulates a received signal by use of an adaptive equalizer, and a recovery circuit includes a timing recovery function and a carrier...
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5170415 |
Burst demodulator for establishing carrier and clock timing from a sequence of alternating symbols
In a burst demodulator, an APSK burst signal containing a preamble of alternating "1" and "-1" symbols, followed by a data field is received and quasi-coherently demodualted into a baseband complex...
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5131008 |
DSP-based GMSK coherent detector
An improved method and apparatus for demodulators for MSK signals. Demodulation of the MSK signals is performed at base-band other than at IF frequencies. A digital signal processor is preferably...
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5090027 |
Coherent PSK demodulator with adaptive line enhancer
A coherent PSK demodulator includes a frequency multiplier for multiplying the frequency of an incoming M-ary PSK signal by a factor M to extract a carrier component of the PSK signal. An adaptive...
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5065107 |
Phase-locked loop bandwidth switching demodulator for suppressed carrier signals
A receiver for tracking a carrier suppressed phase-shifted input signal comprises a phase-locked loop circuit for receiving the input signal and having a variable frequency oscillator responsive to...
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5049830 |
Carrier recovery system and digital phase demodulator
A carrier recovery system combining a narrow band carrier phase estimator and a wide band carrier phase estimator, and a digital phase demodulator using this carrier recovery system. The narrow...
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5001727 |
Carrier and data recovery and demodulation system
A modulated carrier is received on a node (10) and then the I- and the Q-channels extracted with a local carrier clock (16) that is free-running relative to the modulated carrier. The I- and the...
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4975927 |
Demodulator with composite transversal equalizer and eye detection clock synchronizer
In a digital demodulator, a recovered baseband signal is sampled in response to a clock pulse supplied from a VCO and converted to a digital signal representing one of multilevels of the sampled...
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4972430 |
Spread spectrum signal detector
A spread spectrum signal detector for sampling a modulated carrier employing a zero-crossing detection means having two independent control loops, a first loop for a zero-mean threshold control and...
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4959844 |
Clock recovery circuit for digital demodulator
A digital demodulator (10) operates by multiplying an input signal with first and second orthogonal demodulation reference signals (Loa, LOb) to generate respective product signals, which are then...
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4947408 |
Digital carrier demodulator employing components working beyond normal limits
In a digital device having an input thereto comprising a digital sample stream at a frequency F, a method for employing a component therein designed to work at a frequency less than F. The method...
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4894845 |
Receiver for a phase-shift keyed carrier signal
A receiver for a PSK-signal includes a demodulator for obtaining a demodulated data signal which after regeneration is applied to a remodulator for PKS-remodulation of the received PSK-signal to...
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4890302 |
Circuit for extracting carrier signals
In circuits for reproducing carriers for continuous phase modulation having a rational modulation index these signals are multiplied in a multiplier for producing a harmonic, with unique phases...
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4871975 |
Carrier recovery circuit for offset QPSK demodulators
A carrier recovery circuit comprises a voltage-controlled oscillator with a π/2 phase shifter coupled to it for generating carriers of quadrature phase relationship. First and second phase...
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4859956 |
Validity decision circuit capable of correctly deciding validity of an error signal in a multilevel quadrature amplitude demodulator
In a demodulator for demodulating a multilevel quadrature amplitude modulated signal specified by a plurality of output signal points arranged on an approximately octangular specific region into an...
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4849991 |
Method and circuitry for determining symbol timing for time division multiple access radio systems
In order to correctly demodulate a received sequential burst of symbols in a Time Division Multiple Access (TDMA) radio system, proper symbol timing is necessary. A method and circuitry for...
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4811363 |
Method for recovering a phase difference signal
A method of recovering a signal representing the phase difference between a local carrier signal and the carrier of an amplitude and/or phase shift keyed received signal involves dividing the...
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4788695 |
System for decoding self-clocking data signals
A coherent detection and decoding circuit coherently recovers data embedded in a self-clocking data signal by recovering the clock in one integrate and dump circuit and recovering the data in a...
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4780887 |
Carrier recovery circuitry immune to interburst frequency variations
A carrier recovery circuit comprises first and second mixers for mixing a received PSK signal with first and second reference frequency signals. A remodulator extracts a preamble from each burst of...
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4764730 |
Radio receiver demodulation system
A radio receiver demodulation system which utilizes a sweep track type phase lock circuit and provides stable demodulation by starting and stopping the sweep on the basis of a decoded code error.
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4691176 |
Adaptive carrier tracking circuit
An adaptive carrier tracking circuit for receiving pulse code modulated communications which have passed through a scintillation environment is disclosed. The rate and magnitude of phase or...
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4682117 |
Quadrature demodulation data receiver with phase error correction
A data receiver in which the phase of the carrier signal is controlled so that the threshold levels used for coherent demodulation occur at the quarter points, that is 0°, 90°, 180° and 270°....
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4675883 |
Arrangement for Carrier Recovery from Two Received Phase Shift Keyed Signals
An arrangement for carrier recovery of two pulse shift keyed signals comprising a bandpass filter at the input which is followed by a series connection of a full-wave rectifier, a carrier frequency...
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4653071 |
Carrier recovery circuit for PSK communication system
A PSK carrier recovery system has a frequency multiplier, a filter circuit and a limiter circuit for producing a double frequency signal from the incoming PSK signal. A pair of demodulators are...
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4622683 |
Fast acquisition ringing filter MSK demodulator
A clock and carrier recovery circuit, and a related method, for use in a minimum shift keying (MSK) receiver demodulator. The clock and carrier recovery circuit uses ringing filters to lock onto...
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4587498 |
Circuit for recovering the carrier of an amplitude-and-phase-modulated input signal
A circuit for recovering the carrier of an amplitude-and-phase-modulated input signal (in particular QAM signal) is provided with a frequency-controlled oscillator for producing the carrier, with a...
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4584534 |
Method and apparatus for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals
The invention relates to a method for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals and applies especially to data...
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4581586 |
Crosstalk reduction in unbalanced QPSK detectors
A method and apparatus for demodulating quadrature phase shift keyed (QPSK) signals in a manner which reduces crosstalk between channels. The in phase (I) data is recovered first by recovering the...
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4507617 |
Carrier recovery circuit for a PSK modulated signal
A carrier recovery circuit for use in a demodulator for a 2 n -phase PSK modulated signal which comprises a phase-locked loop including a voltage-controlled oscillator (7) and an automatic...
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4470145 |
Single sideband quadricorrelator
A supplementary frequency acquisition circuit in the form of a frequency difference detector called a single sideband quadricorrelator is provided. When used in conjunction with a phase-locked loop...
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