Abstract: A noise suppression system includes an a priori S/N ratio estimated value and expectation calculation unit that acquires an expectation of a priori S/N ratio, by correcting an estimated value of the a priori S/N ratio relating to a signal and a noise based on a priori S/N ratio model or based on a signal model and a noise model, the signal and the noise being estimated from an input signal in which the signal and the noise are mixed; a noise suppression coefficient calculation unit that calculates a noise suppression coefficient with use of the expectation of the a priori S/N ratio; and a noise suppression unit that suppresses the noise included in the input signal by multiplying the input signal by the noise suppression coefficient.

Abstract: Multicarrier techniques for wireless communications system are described. An apparatus may comprise a carrier management module to define a primary carrier for use by a multicarrier communications system to communicate control information, and a secondary carrier for use by the multicarrier communications system to communicate media information, with the secondary carrier having a communication parameter and technology that is potentially different from the primary carrier. Other embodiments are described and claimed.

Abstract: Disclosed is a precoding method comprising the steps of: generating a first coded block and a second coded block with use of a predetermined error correction block coding scheme; generating a first precoded signal z1 and a second precoded signal z2 by performing a precoding process, which corresponds to a matrix selected from among the N matrices F[i], on a first baseband signal s1 generated from the first coded block and a second baseband signal s2 generated from the second coded block, respectively; the first precoded signal z1 and the second precoded signal z2 satisfying (z1, z2)T=F[i] (s1, s2)T; and changing both of or one of a power of the first precoded signal z1 and a power of the second precoded signal z2, such that an average power of the first precoded signal z1 is less than an average power of the second precoded signal z2.

Abstract: A method and device for fisheye camera automatic calibration is disclosed. A first straight line and a second straight line are respectively moved to generate a first fisheye line and a second fisheye line being straight lines. At least two symmetric points are generated on the second straight line based on an intersection of the first straight line and the second straight line as a symmetric central point, so as to correspondingly generate at least two fisheye symmetric points. The second straight line rotates until a distance between the first fisheye line and each of two fisheye symmetric points is equal. Then, central intersection coordinates, fisheye symmetric coordinates, a fisheye symmetric distance are retrieved and used to calculate fisheye parameters.

Abstract: An example method includes: obtaining sinusoidal signals comprising components of a first time-domain signal; shifting phases of the sinusoidal signals by amounts corresponding to a specified time-shift to produce phase-shifted signals, and converting the phase-shifted signals to the time domain to produce time-shifted signals. The shifting may be performed to more closely align an envelope of the first time-domain signal with an envelope of a second time-domain signal.

Abstract: A method is provided for determining at least one filter of a filter bank in a transmission or coding system, on the basis of a prototype filter p. The method includes determining coefficients p[k] of the prototype filter p, of length L equal to N, from ? angle parameters ?i, for 0?i???1, expressed on the basis of a polynomial function ƒ(x), also referred to as a compact representation, such that: f ? ( x ) = ? 4 + t ? ? k = 0 d - 1 ? ? ? k ? T 2 ? k ? ( t ) ; t = 2 ? x - 1.

Abstract: A frequency detection technique includes generating first and second signals such that a frequency of the first signal is the same as a frequency of the second signal and such that the second signal is phase-shifted by a fixed amount with respect to the first signal. The technique further includes generating a third signal having a frequency that corresponds to an absolute value of a difference between the frequency of the first signal and an integer multiple of a frequency of the reference signal. The technique further includes generating a fourth signal having a frequency that corresponds to an absolute value of a difference between the frequency of the second signal and an integer multiple of the frequency of the reference signal. The technique further includes generating an fifth signal indicative of whether a phase relationship between the third and fourth signals is a leading phase relationship, a lagging phase relationship, or an in-phase relationship.

Abstract: Provided is a receiver for processing VSB signal. The receiver includes a first equalizer/decoder unit and a second equalizer/decoder unit. The first equalizer/decoder unit performs a first equalizing operation, first TCM decoding and first RS decoding on a received symbol to output a first dibit. The second equalizer/decoder unit performs a second equalizing operation, second TCM decoding and second RS decoding on the received symbol to output a transport stream. The first dibit is provided as a priori information for a soft-decision operation of the second TCM decoding.

Abstract: A frequency and data synchronization control system through the 8VSB SFN DTx modulation prevents the deterioration of the digitally broadcasted receiving sensitivity caused by a discrepancy of the frequency or data between the receiver of the digital broadcasting signal and the distributed translator or between distributed translators.

Abstract: A carrier recovery apparatus includes a pilot strength detector, a first lock loop, a second lock loop, and a controller. The pilot strength detector determines whether a pilot strength of an input signal is greater than a threshold value to generate a control signal. The first lock loop performs a first carrier recovery on the input signal. The second lock loop performs a second carrier recovery on the input signal. The controller selectively allows the first lock loop to perform the first carrier recovery on the input signal or the second lock loop to perform the second carrier recovery on the input signal according to the control signal. The first lock loop is a pilot-based FPLL and the second locked loop is a pilot-less PLL.

Abstract: A phase tracking system includes a source of an input signal representing a received symbol. A phase rotator has a first input terminal which is responsive to the input signal, a second input terminal which is responsive to a phase correction signal, and an output terminal which produces a phase adjusted output signal. A decision element generates an ideal signal representing the received symbol in response to the phase adjusted output signal. A phase adjuster, which has full phase wrap-around capability, generates the phase correction signal in response to the phase difference between the phase adjusted output signal and the ideal signal.

Abstract: A symbol timing recovery apparatus used with a VSB-type receiver and a method of the same. In order for the symbol timing recovery, error information is generated and used utilizing a band edge component maximization (BECM) of a frequency band as well as an upper frequency band. Therefore, the symbol timing recovery can be more effectively achieved even when the upper frequency band is damaged due to multi-path components. Also, efficiency of the overall timing recovery can be improved by using the lower frequency band as well as the upper frequency band of the received signal in performing the symbol timing recovery. As a result, deterioration of the receiving system including the symbol timing recovery apparatus can be prevented.

Abstract: An arrangement is described for demodulating a vestigial sideband signal component contained in an amplitude-modulated frequency signal, and preferably in a vision intermediate-frequency signal derived from a television signal.

Abstract: The present invention provides a novel symbol timing recovery method for VSB receivers. Systems are described that comprise a timing error detector (TED) that produces an exact symbol timing error even in the presence residual carrier phase offset, loop filter that controls the characteristics of acquisition and tracking of digital PLL loop, Voltage/Numerically Controlled Oscillator (VCO/NCO) that adjusts the sampling instant and phase, A/D converter that samples a continuous VSB input signal, and a interpolating squared root raised cosine filter that performs both matched filtering and a compensation of constant timing offset of quarter symbol caused by the invented TED. The timing error detector in this invention comprises an envelope detector, band pass filter, squaring block, high pass filter, and decimator.

Abstract: A device and method for a symbol recovery in a digital television are disclosed. The device includes a symbol clock recovery device includes a remained phase error remover operating a digital baseband real/imaginary number component signals, and removing remained phase error, a timing error detector nonlinearly operating the real/imaginary number component signals having the remained phase error removed, and detecting symbol clock phase error information therefrom, and an oscillating part generating a symbol clock frequency compensated to at least two times from the detected symbol clock phase error information and outputting the compensated frequency.

Abstract: An arrangement is described for demodulating a vestigial sideband signal component contained in an amplitude-modulated frequency signal, and preferably in a vision intermediate-frequency signal derived from a television signal.

Abstract: Single sideband (SSB) mixers and methods of extracting a SSB signal, which are capable of outputting a single frequency using a plurality of mixers and a local oscillating frequency without having to implement phase-shifting. In one embodiment, a single sideband (SSB) mixer comprises a first mixer and a second mixer, wherein the first and second mixers multiply an input IF (intermediate frequency) signal by a local IF signal having the same frequency of the input IF signal; a band-pass filter which passes upper sideband signal output from the first mixer; a third mixer which multiplies the upper sideband signals output from the band-pass filter by a LO (local oscillating) signal; a fourth mixer which multiplies the signals output from the second mixer by the LO signal; and a subtraction device that subtracts output signals of the third mixer from output signals of the fourth mixer.

Abstract: A vestigial sideband VSB receiver includes a digital processing part for selecting a desired channel frequency via an antenna and converting the desired channel frequency to an intermediate frequency to digitize a predetermined band of the intermediate frequency, a carrier wave restoring part for extracting pilot components from a signal of the digitized pass band to restore carrier waves, and a demodulator for separating components I and Q from the signal of the digitized pass band and multiplying the components with a complex carrier wave, which is restored in the carrier wave restoring part. The carrier waves are restored by extracting the pilot signals from the pass band and detecting the symmetrical errors of the carrier wave frequency, so that the carrier wave may be stably obtained and pursued with relation to the both positive and negative frequency offsets.

Abstract: A vestigial-sideband (VSB) signal is converted to a double-sideband amplitude-modulation signal having information that is subsequently detected in the double-sideband amplitude-modulation signal. A method for performing the conversion includes mixing the VSB signal with a first beat frequency different from a carrier frequency of the VSB signal, the first beat frequency being of such value as to generate a first mixing result that is translated in frequency to have a carrier at an offset frequency; mixing the VSB signal with a second beat frequency different from the carrier frequency of the VSB signal and from the first beat frequency, the second beat frequency being of such value as to generate a second mixing result that is translated in frequency to have a earner at the offset frequency; and combining the first and second mixing results to form the double-sideband amplitude-modulation signal with a carrier frequency at the offset frequency.

Abstract: An apparatus and method for eliminating a vestigial sideband (VSB) pilot tone in a vestigial sideband/quadrature amplitude modulation (VSB/QAM) receiving system, is provided. This apparatus eliminates a vestigial sideband (VSB) pilot tone in a vestigial sideband/quadrature amplitude modulation (VSB/QAM) shared receiving system including a VSB/QAM shared modulator for demodulating a received VSB signal and outputting I-axis VSB symbols and Q-axis VSB symbols.

Abstract: To improve the quality of the demodulated signal without altering the form in which an AM radio wave is transmitted, the received amplitude-modulated signal is converted to a single-sideband signal, and the information signal demodulated from the phase term of this converted single-sideband signal.

Abstract: A method of processing an AM radio signal comprises the step of receiving an AM radio signal including an upper sideband portion and a lower sideband portion, demodulating the upper sideband portion and the lower sideband portion to produce a demodulated upper sideband signal and a demodulated lower sideband signal, weighting the demodulated upper sideband signal and the demodulated lower sideband signal in response to noise power to produce a weighted demodulated upper sideband signal and a weighted demodulated lower sideband signal, and combining the weighted demodulated upper sideband signal and the weighted demodulated lower sideband signal to produce an output signal. Demodulators which process AM radio signals in accordance with the method, and receivers incorporating the demodulators, are also included.

Abstract: A vestigial-sideband (VSB) signal is converted to a double-sideband amplitude-modulation final intermediate-frequency signal that is subsequently detected to generate a baseband demodulation result. The carrier of this final I-F signal has a carrier offset from zero-frequency, which carrier offset exceeds the highest modulating frequency of the VSB signal and is adjusted to a prescribed carrier offset value. The double-sideband amplitude-modulation final I-F signal is generated by combining the VSB signal with its image.

Abstract: A quadrature vestigial sideband (QVSB) communication system provide bandwidth efficient data transmission using cross coupled data signaling during both transmit and receive having controlled intersymbol interference. The QVSB modem includes cross coupled arm transmit and receive data filtering on both of the I&Q channels providing a bandwidth efficient QVSB spectra. A quadrature crosstalk maximum likelihood sequence estimator implements a Viterbi decoding algorithm for providing estimated data sequence outputs. The receiver is a coherently aided demodulator synchronized by a synchronization loop providing time and phase references using the estimated data sequence outputs.

Abstract: A bandpass phase tracker automatically samples at prescribed carrier phases when digitizing a vestigial-sideband intermediate-frequency signal, which VSB I-F signal is modulated in accordance with a baseband symbol code of a prescribed symbol frequency. Heterodyning circuitry mixes oscillations from a local oscillator with the VSB I-F signal received from the I-F amplifier to generate an analog low-frequency heterodyne signal offset from zero frequency. The heterodyne signal is digitized in accordance with a first sampling clock signal to supply input signal for digital demodulation circuitry that demodulates the VSB I-F signal to supply real and imaginary components of a demodulated signal at baseband. The real component of the demodulated signal is supplied to an equalizer and symbol decoded; the imaginary component controls the frequency and phase of the local oscillator.

Abstract: A range gated microwave motion sensor having adjustable minimum and maximum detection ranges with little response to close-in false alarm nuisances such as insects or vibrating panels. The sensor resolves direction of motion and can respond to target displacement in a selected direction and through a selected distance, in contrast to conventional hair-trigger motion sensors. A constant false alarm rate (CFAR) detector prevents false triggers from fluttering leaves, vibrating machinery, and RF interference. The sensor transmits an RF pulse and, after a modulated delay, mixes echo pulses with a mixer pulse. Thus, the echo pulses are modulated at the mixer output while transmit and mixer pulse artifacts remain unmodulated and easily filtered from the output. Accordingly, the sensor only responds to echoes that fall within its minimum and maximum range-gated region, and not to close-in or far-out objects.

Abstract: A method of estimating pilot signal phase embedded in a wideband digital signal modulating a RF signal that is down converted to an intermediate frequency and digitized includes the steps of summing a block of the signal samples for removing the modulation data and generating data values representative of vector locations of the pilot signal with each data value representing an angular rotation of the pilot signal vector, and calculating the phase of the pilot signal by determining the arc tangent of the data values. The method produces a computationally efficient narrow band filter generated at the pilot signal frequency by simple addition of the digital data values. The method is usable in a software based 8-VSB digital television demodulation system.

Abstract: A method and system are provided for the transmission and reception of a composite radio-frequency (RF) signal including a supplemental signal, preferably representing encoded digital information, together with an analog signal which represents monophonic analog audio in the AM-band. The analog monophonic component of the composite signal may be received by conventional AM-band audio receivers. In certain embodiments, the analog signal is a single-sideband large-carrier or vestigial-sideband large-carrier signal, and the composite RF signal includes a digital signal whose spectrum is substantially confined in one inner sideband. In other embodiments, a baseband digital signal is combined with an analog monophonic audio signal and transmitted in upper inner and lower inner sidebands using nonlinear compatible quadrature amplitude modulation (NC-QAM). Additional digital signals' spectrum occupies the lower outer and upper outer sidebands.

Abstract: An N-VSB (vestigial sideband) modulation signal is converted into an M-QAM (quadrature amplitude modulation) signal, where M=N2, by shifting the symbol rate frequency of a received N-VSB modulation signal to center the waveform spectrum about zero Hertz prior to complex demodulation so that data symbols will alternately appear on demodulated I and Q channels. A pilot tone of the received N-VSB modulation signal is removed to eliminate any bias in the both I and Q channels. Symbol timing between I and Q channels is offset, and quadrature amplitude demodulation of the I and Q channel signals generate alternating I and Q channel data symbols. Alternating inversion of the alternating I and Q channel data symbols recovers the N-VSB symbol data.

Abstract: A communication system for sending a sequence of symbols on a communication link. The system includes a transmitter for placing information indicative of the sequence of symbols on the communication link and a receiver for receiving the information placed on the communication link by the transmitter. The transmitter includes a clock for defining successive frames, each of the frames including M time intervals, where M is an integer greater than 1. A modulator modulates each of M carrier signals with a signal related to the value of one of the symbols thereby generating a modulated carrier signal corresponding to each of the carrier signals. The modulated carriers are combined into a sum signal which is transmitted on the communication link. The carrier signals include first and second carriers, the first carrier having a different bandwidth than the second carrier.

Abstract: A sampling timing phase error detector in a VSB modulation signal which can realize a high speed transmission. The sampling timing phase error detector for detecting a timing phase error of a sampling from a discrete time sequence obtained by sampling, by a frequency n.multidot.fs (n is a positive integer), a multivalue VSB modulation signal in which transmission symbol sequence of real numbers is processed by a VSB modulation at a symbol frequency fs obtains the timing phase error on the basis of signals obtained by detecting the discrete time sequence at frequencies around a Nyquist frequency fs/2 as a center.

Abstract: A Vestigal Sideband (VSB) demodulator having a clock generator for generating a clock signal based on a symbol frequency of the VSB signal; an A/D converter for converting the VSB signal into a digital signal based on the clock signal of the clock generator; a first multiplier for multiplying the digital signal by a first value sequence and generating a first multiplier output signal; a second multiplier for multiplying the digital signal by a second value sequence and generating a second multiplier output signal; a complex type filter for shaping and VSB demodulation of the multiplier output signals and generating Inphase and Quadrature data output signals; a decimating circuit for decimating the Inphase and Quadrature data output signals and generating decimated signals; a complex multiplier for multiplying the decimated signals by a predetermined value and generating multiplied output signals; an error detector for detecting a frequency deviation and a phase deviation from the multiplied output signals and

Abstract: A method and system are provided for the transmission and reception of a composite radio-frequency (RF) signal including a supplemental signal, preferably representing encoded digital information, together with an analog signal which represents monophonic analog audio in the AM-band. The analog monophonic component of the composite signal may be received by conventional AM-band audio receivers. In certain embodiments, the analog signal is a single-sideband large-carrier or vestigial-sideband large-carrier signal, and the composite RF signal includes a digital signal whose spectrum is substantially confined in one inner sideband. In other embodiments, a baseband digital signal is combined with an analog monophonic audio signal and transmitted in upper inner and lower inner sidebands using nonlinear compatible quadrature amplitude modulation (NC-QAM). Additional digital signals' spectrum occupies the lower outer and upper outer sidebands.

Abstract: A radio frequency (rf) receiver adapted to receive a number of different digitally modulated rf input signals such as quadrature amplitude modulated (QAM) and vestigial side band (VSB) rf input signals includes circuitry for down converting the rf input signals to an intermediate frequency (IF) range having a center frequency fc2 and a bandwidth of Bhz and converter circuitry for sampling the IF signals and then producing corresponding baseband signals. In a preferred embodiment, the intermediate frequency signals are applied to a sample and hold circuit which is sampled at a frequency fs and whose output is coupled via a low pass filter to an analog-to-digital converter whose output is then applied to a Hilbert filter for demodulating the sampled signals and producing baseband signals. In-phase (I) and quadrature (Q) signals are produced whose phase and amplitude are not a function of different components and their tolerance of different conduction paths, as in the prior art.

Abstract: A modulation and demodulation scheme for video signals may be used for HDTV signals using VSB-PAM, analog NTSC signals using VSB-AM and digital video signals using QAM. VSB-PAM modulation and demodulation may be performed using in-phase and quadrature baseband filters. By adjusting the filter taps, a single modulator structure may be used for QAM and VSB-PAM modulation. Similarly, a single demodulator structure may be used for QAM and VSB-PAM demodulation. This demodulator may also be used for VSB-AM modulation.

Abstract: An error detecting and correcting apparatus incorporated in a trellis decoder to compensate effects of 180.degree. phase errors of a transmitted N-level VSB (Vestigial Sideband) signal in a GA (Grand Alliance) HDTV (High Definition Television) receiver, the transmitted signal including a transmitted reference signal and a transmitted data signal, the decoder including an error detector for comparing a predetermined reference signal with the transmitted reference signal to provide an error signal denoting the presence or absence a 180.degree. phase error, a phase corrector for inverting the sign of the transmitted data signal to provide an inverted transmitted data signal, a switch for selectively providing the transmitted data signal or the inverted transmitted data signal in response to the error signal, and a trellis decoder for decoding the transmitted data signal or the inverted data signal provided by the switch.

Abstract: A DC offset measurement and compensation circuit includes a switch arrangement for establishing a zero carrier condition in the circuit. The circuit output is integrated to develop any DC offsets, which are converted to analog form and subtracted from the signal output. A reference may also be subtracted to establish a base digital level for the output.

Abstract: A biphase stable FPLL includes a polarity determination circuit that ascertains the lockup phase of the FPLL based upon the polarity of the pilot in the digital signal. A frequency lock indicator circuit determines from the recovered pilot when frequency lock has occurred and the polarity determination circuit is responsive thereto for inverting the phase of the incoming signal (or alternatively, of the outgoing signal) as determined in order to supply an output signal of predetermined polarity. The frequency lock indicator consists of a zero crossings detector and a latch that is sampled for a time period. The zero crossings detector is a delay and an exclusive OR gate. An optional confidence counter may be used with the latch to determine when frequency lock has occurred to provide the lock indicator signal.

Abstract: A polarity detection circuit for an FPLL demodulated signal including a small DC pilot recovers the DC pilot by determining the DC levels of the demodulated output signals both with and without the DC pilot. A zero carrier condition is created for determining the DC level of the output signal without the DC pilot. The two DC levels are subtracted and limited and the polarity of the recovered DC pilot is used to control the operation of a polarity inverter to assure that the output signal has a desired polarity.

Abstract: In a demodulator for a complex-value vestigial sideband signal, a Nyquist slope filter which consists of two subfilters (Ra, Ia) is used, a filter device (FBASTP) being connected downstream of, or also capable of being integrated in, the said Nyquist slope filter, in order to suppress subcarriers, specifically in such a way that the real parts (Ra) and imaginary parts (Ia) of the sub-filters can be combined in each case.

Abstract: A communication system having a modulation system for transmitting a symbol set via a single side-band modulated carrier and a demodulation system for recovering the in-phase and quadrature signals from the modulated carrier. The modulation circuit receives M symbol values and generates M time domain samples for each of the in-phase and quadrature signals. The in-phase and quadrature signals can then be combined to generate the single side-band modulated carrier. The modulation circuit includes a transform circuit for generating M transformed symbol values by computing the transform of the M symbol values. A polyphase filter bank having 2M FIR filters is used to process the output of the transform circuit. Each filter has g taps, where g is an integer greater than 1. The outputs of the polyphase filters are combined with the outputs of the polyphase filters generated from a previously received set of M symbols to generate the M time-domain signal values of the in-phase signal.

Abstract: A demodulator receives a radio signal and causes a carrier signal reproducing circuit to reproduce the carrier signal of the received signal. One amplifier amplifies the amplitude of the reproduced carrier signal by K, and another amplifies the amplitude of the reproduced carrier signal by (K+2). An adder adds the reproduced carrier signal, amplified by K, and the received signal. A subtracter subtracts the received signal from the reproduced carrier signal amplified by (K+2). The output signal of the adder is demodulated by a first FM demodulator and the output signal of the subtracter is demodulated by a second FM demodulator. Another subtracter outputs the difference between the demodulated signals from the first and second FM demodulators as a demodulated signal of the received signal.

Abstract: In a radio receiver for receiving vestigial sideband (VSB) signals including symbol codes descriptive of digital signals, HDTV signals being exemplary of such VSB signals, a tuner provides for selecting one of channels at different locations in a frequency band used for transmitting such VSB signals. The tuner also includes mixers for performing plural conversion of the selected channel to a final intermediate-frequency signal, which is digitized by an analog-to-digital converter. A phase tracker, operative on narrow-bandpass filtered portions of the digitized final intermediate frequency signal centering on its carrier frequency, suppresses an imaginary portion of the final intermediate-frequency signal, arising from multipath distortion or from phase incoherency in local oscillations used during frequency conversion.

Abstract: 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 receives as modulating signal a binary phase-shift-keying (BPSK) signal encoding digital signals. The quadrature transmission reduces the visibility of the lower-frequency PSK sidebands in the TV signal as viewed on screen. The symbol rate of the PSK is made to be a multiple of the horizontal line scan rate of video signal. To reduce the visibility of the higher-frequency PSK sidebands in the TV signal as viewed on screen, the BPSK is transmitted twice during respective frames of successive pairs of data frames, which data frames recur at the same rate as video frames. To reduce the interference of video with the PSK, the PSK is subjected to partial-response filtering at the transmitter and is highpass line-comb filtered at the digital signal receiver.

Abstract: A synchronous detector for demodulating and decoding a digital data signal modulated either according to a vestigial sideband or a quadrature amplitude modulation scheme is based upon the principle of recognizing that a vestigial sideband signal may be regarded and treated as an offset-keyed QAM signal. The detector comprises a tuner for tuning to a center frequency symmetrically displaced within the transmitted digital data signal frequency spectrum and a decoder circuit selectively operating to reconstruct the transmitted digital data stream according to the duration of a transmitted data symbol. A related method of demodulating and decoding a modulated digital data stream comprises analogous steps of tuning to a center carrier frequency and selectively switching between in phase and quadrature arms of the demodulator such that the switch resides in one position or the other for a duration equal to half the duration of a transmitted data symbol.

Abstract: An improved modulator circuit for mixing a modulation signal with a carrier signal includes first and second harmonic mixers which are operative to produce modulated output signals at an output frequency corresponding to both the sum and the difference of the modulation signal frequency and the even harmonic frequencies of the carrier signal frequency. In one configuration employing a 90.degree. hybrid, the output signals of the harmonic mixers are combined to produce a single sideband modulated output signal. A novel harmonic mixer circuit is also provided along with demodulator circuits and methods of modulating and demodulating modulation signals.

Abstract: A system of transmission with amplitude modulation for the transmission of signals of all types, analog and/or digital, requiring high performance characteristics with respect to the noise induced by the transmission channel, comprising, at transmission, means for the suppressed carrier amplitude modulation of a useful signal and means for the amplitude modulation, in phase quadrature with said modulated useful signal, of a service signal, making it possible, at reception, to remove the ambiguity on the polarity of the demodulated useful signal. Thus it enables the transmission of signals in suppressed carrier modulation mode, hence with a good signal-to-noise ratio, without losing the polarity of the signal. The transmitters and receivers according to the invention also enable the transmission and reception of the signals modulated in SCAM, VSBAM or VSBSCAM modes.

Abstract: An asymmetrical sideband modulated (ASM) signal, such as an RF NTSC television signal is demodulated into in-phase and quadrature phase components, each of which are sampled at a sampling rate that is less than the Nyquist rate for the components. The signals, each of which includes aliasing distortion, are respective real and imaginary parts of a complex signal that is not subject to aliasing distortion at the chosen sampling frequency. The in-phase component of the signal is recovered by inserting zero-valued samples interstitially into each of the sampled in-phase and quadrature phase signals and then applying the modified signals to a complex filter. The resultant interpolated in-phase signal is a full bandwidth signal and is substantially free of aliasing distortion.

Abstract: A communication system for sending a sequence of symbols on a communication link. The system includes a transmitter for placing information indicative of the sequence of symbols on the communication link and a receiver for receiving the information placed on the communication link by the transmitter. The transmitter includes a clock for defining successive frames, each of the frames including M time intervals, where M is an integer greater than 1. A modulator modulates each of M carrier signals with a signal related to the value of one of the symbols thereby generating a modulated carrier signal corresponding to each of the carrier signals. The modulated carriers are combined into a sum signal which is transmitted on the communication link. The carrier signals include first and second carriers, the first carrier having a different bandwidth than the second carrier.

Abstract: A communication system for sending a sequence of symbols on a communication link. The system includes a transmitter for placing information indicative of the sequence of symbols on the communication link and a receiver for receiving the information placed on the communication link by the transmitter. The transmitter includes a clock for defining successive frames, each of the frames including M time intervals, where M is an integer greater than 1. A modulator modulates each of M carrier signals with a signal related to the value of one of the symbols thereby generating a modulated carrier signal corresponding to each of the carrier signals. The modulated carriers are combined into a sum signal which is transmitted on the communication link. The carrier signals include first and second carriers, the first carrier having a different bandwidth than the second carrier.