Abstract: A radio receiver uses the same tuner for receiving a selected digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal. The final IF signal is digitized at a rate that is a multiple of both the symbol frequencies of the QAM and VSB signals, for synchrodyning to baseband. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of the multiple of both the symbol frequencies of the QAM and VSB signals by applying automatic frequency and phase control (AFPC) signals developed in the digital circuitry to a local oscillator of the tuner. Baseband DTV signals obtained by synchrodyning the final IF signals have a sample rate higher than symbol rate to facilitate symbol synchronization. The baseband DTV signals are decimated to symbol rate before performing channel equalization to reduce the number of multipliers required in the channel equalization filter.

Abstract: An apparatus efficiently performs symbol timing recovery of sampled data included in a vestigial sideband (VSB) signal. Each of the sampled data is first filtered to output a positive and a negative band edge filtered components thereof. Thereafter, the negative band edge filtered component is processed to obtain a conjugate complex component; and the positive band edge filtered component is multiplied by the conjugate complex component to provide a multiplied component as symbol timing information. Finally, each of the sampled data is corrected based on the symbol timing information to generate interpolated data thereon as the timing recovered data.

Abstract: The data field synchronization segment as symbol coded for VSB transmission comprises pseudo-random noise (PN) sequence information that can be detected using a match filter in a QAM/VSB DTV signal receiver. The data field synchronization segment as symbol coded for QAM transmission does not contain the PN sequence information that can be detected using the same match filter used for detecting the PN sequence information in the VSB transmission. A threshold detector is used for determining whether the match filter response is of sufficient energy to indicate occurrence in a received DTV signal of the PN sequence information in the data field synchronization segment of a VSB DTV transmission. Timed latch circuitry is used for latching the indication for a period of time longer than at least one DTV data field. The QAM/VSB DTV signal receiver is operated either in a QAM reception mode or in a VSB reception mode, depending on the output signal of the timed latch circuitry.

Abstract: Methods for operating an adaptive receiver for receiving a selected DTV signal, which can be either a quadrature-amplitude-modulation (QAM) signal or a vestigial sideband (VSB) signal. The adaptive receiver includes adaptive symbol decoding circuitry for adaptively decoding baseband signal encoded in different signal formats at selected different code rates to provide a decoded output signal, an adaptive deinterleaver for deinterleaving the decoded output signal in accordance with a deinterleaving function selected from a plurality of deinterleaving functions, and an adaptive error decoder for detecting and correcting errors in the deinterleaver output signal.

Abstract: A broadband integrated television receiver for receiving a standard antenna or cable input and outputting an analog composite video signal and composite audio signal is disclosed. The receiver employs an up-conversion mixer and a down-conversion mixer in series to produce an IF signal. An IF filter between the mixers performs coarse channel selection. The down-conversion mixer may be an image rejection mixer to provide additional filtering. The received RF television signals are converted to a standard 45.75 MHz IF signal for processing on-chip by additional circuitry.

Abstract: In a circuit arrangement for demodulating an intermediate-frequency video signal generated while using a Nyquist edge, having a phase-locked loop (1) including a phase detector (3), a loop filter (4) and a voltage-controlled oscillator (5), and a video demodulator (2), the intermediate-frequency video signal being applied to the phase detector (3) and the output signal of the phase-locked loop (1) being applied to the video demodulator (2), which converts the intermediate-frequency video signal into a baseband video signal, phase fluctuations contained in the carrier of the intermediate-frequency video signal due to its generation while using a Nyquist edge are compensated in that the phase comparator (3) operates, by approximation, independently of modulation in the control range of the intermediate-frequency video signal, in that the baseband video signal is present in an inverted form with respect to the intermediate-frequency video signal, and in that a correction signal is derived from the baseband video

Abstract: There is provided a multi-receiving demodulator for receiving broadcasting signals from multiple broadcasting systems. The multi-receiving demodulator has a first band pass filter for selectively band-pass-filtering an intermediate frequency output from a tuner to obtain a color subcarrier corresponding to the broadcasting system of a received signal, according to a first control signal, and a second band pass filter for selectively band-pass-filtering the intermediate frequency output from the tuner to obtain an audio carrier corresponding to the broadcasting system of the received signal, according to a second control signal. A video demodulating portion receives the color subcarrier from the first band pass filter and selectively demodulates a video signal corresponding to the broadcasting system of the received signal in accordance with the second control signal.

Abstract: A television converter uses digital signal processing (DSP) to provide compatibility with different television standards including NTSC and PAL video standards and FM, BTSC, DIN, Home Theatre, NICAM and independent digital audio standards. Audio processing is accomplished without passing the audio through a Nyquist filter used for video. This eliminates AM to PM conversion improving luminance linearity and differential gain and phase. It also prevents video information from phase modulating the audio intercarrier, thereby eliminating video "buzz" components in the audio. The audio processing includes a synchronous FM demodulator and a separate synchronous FM/QPSK demodulator for handling the different audio standards. Handling historical analog TV standards with DSP also enables the advantageous combination of analog and digital television reception within a single digital VLSI ASIC.

Abstract: A radio receiver uses the same tuner for receiving a selected wideband digital signal of at least a few megahertz bandwidth, such as a digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal accompanied by an unmodulated pilot carrier signal; and a second transmission standard specifies quadrature amplitude modulation. It is determined at the receiver which of respective modulation formats specified for the various transmission standards is employed for transmitting the wideband digital signal being received. The wideband digital signal is demodulated to produce a demodulated signal, demodulation be done according to a demodulation format suitable for demodulating the modulation format determined to be employed for transmitting the wideband digital signal.

Abstract: A digital demodulator which removes frequency and phase errors existing in a digital signal and converting the error-removed digital signal into a base band signal. The digital demodulator uses a frequency that is twice the transmission rate as the frequency of the sampling clock signal of an analog-to-digital (A/D) converter, and demodulates a received signal in a digital processing using the A/D converter which is low-speed. Thus, all of the received signal processing becomes digitized.

Abstract: A multi-standard receiver is which is particularly suited for reception of B/G-PAL and D/K-PAL TV signals. In the receiver, a tuner (TUN) selects a desired TV signal which is passed to a multi-standard demodulator (DEM) via an intermediate-frequency filter circuit (IFF). To obtain good performance, particularly in view of EN 55020 requirements, at moderate costs, the intermediate-frequency filter circuit (IFF) includes a main filter (FIL1) and an auxiliary filter (FIL2). The main filter (FIL1) may have a relatively narrow band, for example, just capable of passing a full B/G-PAL TV IF signal to the demodulator circuit. For D/K-PAL reception, the auxiliary filter (FIL2) is effectively switched (SW) in parallel with the main filter (FIL1). The auxiliary filter (FIL2) transfers the D/K-PAL sound carrier to the demodulator circuit (DEM), which transfer is not possible via the relatively narrow-band main filter (FIL1).

Abstract: A digital television signal receiver in a television set or in a digital video recorder digitizes received digital television signal as converted in frequency to a final intermediate-frequency band close to baseband, then performs equalization filtering on the digitized signal before demodulating it in the digital regime to regenerate baseband symbol coding. The equalization filtering is adaptive, and weighting coefficients for this filtering are adjusted in response to portions of the regenerated baseband symbol coding. Initial adjustment of the weighting coefficients is preferably done using selected portions of the data field synchronizing signal as a ghost cancellation reference signal, in order that convergence of the weighting coefficients to desired values proceeds more rapidly.

Abstract: A first mixer outputs a TV signal of a first intermediate frequency (the first IF) by up-converting an input signal. A second mixer outputs a TV signal of the second intermediate frequency (the second IF) by down-converting the TV signal of the first IF. The second IF is chosen to be different and below the conventional intermediate frequency used by single super-heterodyne analog TV tuners. By choosing a sufficiently low second IF, the passband signal can be directly sampled by an analog to digital converter after being filtered by a low pass filter. Thus, a digital television broadcast receiver tuner is achieved which can be used with a direct passband sampling type digital demodulator.

Abstract: A radio receiver for receiving a selected digital HDTV signal, irrespective of whether it is a complex-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal, using the same tuner. The tuner supplies a final IF signal in a 6 MHz frequency band, the lowest frequency of which is not appreciably more than 2.38 MHz. The final IF signal is digitized for synchrodyning to baseband, with the 2.375 MHz difference between the carrier frequencies of QAM and VSB signals being taken into account in the digital synchrodyning circuitry. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of symbol frequency by applying automatic frequency and phase control signals developed in the digital circuitry to a local oscillator of the tuner. The presence of the pilot carrier accompanying a selected VSB HDTV signal is detected for automatically switching the radio receiver for operation in a VSB signal reception mode.

Abstract: A QAM/VSB digital television (DTV) receiver of plural conversion type uses the same circuitry up to a penultimate IF amplifier for receiving DTV signals no matter whether they use QAM or VSB modulation. The converter used for generating final IF signals when QAM modulation is received and the converter used for generating final IF signals when VSB modulation is received have respective mixers and respective local oscillators with separate automatic frequency and phase control. The use of such separate converters avoids a lock-out from VSB reception mode that otherwise can occur during the reception of DTV signals with VSB modulation.

Abstract: A digital television broadcast receiver comprising a digital signal demodulator, wherein the frequency of an intermediate frequency signal is made higher than the maximum frequency of any received signal, the intermediate frequency signal being demodulated by the digital signal demodulator, whereby interference attributable to a carrier signal from an oscillator of the demodulator is suppressed during demodulation.

Abstract: An improved DBS receiver front end architecture having a tuner chip and a demodulator/decoder chip. The tuner chip and the demodulator/decoder chip each include portions of a digital tuning frequency synthesizer. The frequency synthesizer comprises one or more digital counters which are implemented on the demodulator/decoder chip, and an oscillator which is implemented on the tuner chip. This advantageously avoids digital noise interference with the tuner chip while providing a reduced part count. Briefly, the present invention concerns a DBS receiver front end which includes a tuner chip and a demodulator/decoder chip which cooperate to perform a frequency synthesis function. The tuner chip has a tuning oscillator coupled to a tank circuit having an adjustable resonance frequency, and a downconverter coupled to receive a tuning frequency signal provided by the tuning oscillator.

Abstract: A receiver for receiving a cable and terrestrial digital signals of differing VSB modes where the data levels of the various signals have a desired relationship that enables simple data level slicing and error determination. Some of the signals have sync levels that do not conform to the desired relationship and the receiver includes a comb filter for reducing interference when receiving an 8VSB terrestrial signal. The mode of the received signal is determined and a correction factor is applied to the syncs of the signals as needed to reestablish the desired relationship. Operation of the comb filter results in additional levels and a disruption of the desired relationship. For such cases, the comb filtered data levels are modified to make them a subset of the VSB 16 data levels. The modifications are accomplished in feedback paths of the phase tracker after the circuit equalizer and do not affect the data levels passed to the next stage.

Abstract: A FPLL has an I, a Q and a third multiplier, with the I multiplier supplying demodulated signals to a limiter and the Q multiplier supplying signals to a loop filter. A VCO and phase shift circuit supply quadrature signals to the I and Q multipliers. The analog input signal is applied to the I multiplier and to the third multiplier. The third multiplier, which is located in an AC path in the loop to avoid the effects of offsets due to stray DC voltages and currents, is also supplied with the digital output of the limiter. The third multiplier supplies its output to the Q multiplier.

Abstract: An improved multiple conversion CATV settop terminal eliminates the adverse effects of oscillator difference beats by selectively controlling local oscillators and the use of a wideband bandpass filter. The wideband bandpass filter is coupled between the output of an up converter mixer and the input of a down converter mixer. Each mixer receives a second input from its corresponding local oscillator. A system microprocessor is programmed to control each local oscillator such that the oscillator difference beat frequencies are translated out of a following IF filter passband. Once translated, the oscillator difference beat frequencies no longer present a source of distortion to the received information signal.

Abstract: A video processing system that automatically adjusts video processor parameters depending upon the format of a received video signal in, e.g., a television receiver capable of receiving a multiplicity of video formats.

Abstract: At the transmitter side, carrier waves are modulated according to an input signal for producing relevant signal points in a signal space diagram. The input signal is divided into, two, first and second, data streams. The signal points are divided into signal point groups to which data of the first data stream are assigned. Also, data of the second data stream are assigned to the signal points of each signal point group. A difference in the transmission error rate between first and second data streams is developed by shifting the signal points to other positions in the space diagram expressed at least in the polar coordinate system. At the receiver side, the first and/or second data streams can be reconstructed from a received signal. In TV broadcast service, a TV signal is divided by a transmitter into, low and high, frequency band components which are designated as a first and a second data streams respectively.

Abstract: A method and apparatus for recovering an information carrier which has been transmitted as a sub-carrier in the lower VSB spectral region of a television signal. The invention utilizes a spectral inversion method to shift the data carrier frequency from the normal VSB spectral region to a spectral region normally associated with video information in a standard television signal. The data carrier is then recovered using a standard video demodulator and provided to a data utilization circuit, such as a QPSK demodulator.

Abstract: A method for multi-mode autonomous selection demodulation is disclosed. The method includes the step of providing a receiver with demodulation circuitry (110-112) capable of demodulating a plurality of waveform modulation techniques. The method also includes the step of receiving a modulated information waveform and a preamble associated with the modulated information waveform. The method also includes the steps of matching the preamble against a predefined set of patterns corresponding to a plurality of modulation techniques at the receiver and identifying a corresponding demodulation technique. Additionally, the method configures the demodulation circuitry (110-112) to apply the corresponding demodulation technique to the modulated information waveform.

Abstract: Digital broadcast receiving terminal apparatus which receives multi-channel digital broadcast signals to record the huge capacity without deteriorating the quality of signals and to visualize the digital broadcasting. The outputs form the error correction decoding circus 4 are applied to the TS processor 12 via the switches SW 1 and SW 2, at the same time they are applied to the recording program selector 11. The recording program selector 11 applies the encoded data of the predetermined program to the digital interface 13, the digital interface 13 inputs and outputs the encoded data through bus in the IEEE1394 specification for example. Thus, the encoded data are applied to the external equipment and recorded as they are, and the degradation of the quality can be prevented. The switches SW 1 and SW 2 changes the receiving signals and the outputs from the digital interface 13 and applies them to the TS processor 12. The TS processor 12 depacketizes the input encoded data.

Abstract: NTSC interference detectors include an NTSC extracting filter for supplying an NTSC extracting filter response that separates accompanying co-channel interfering NTSC signal component from the received I-channel baseband signal and its direct bias component. The NTSC extracting filter comprises a comb filter, which includes a delay circuit for supplying in response to said received I-channel baseband signal differentially delayed signals with a prescribed amount of differential delay equal to the duration of an even number of horizontal scanning periods of NTSC signal as will generate said co-channel interfering NTSC signal components. The comb filter further includes a subtractor for differentially combining the differentially delayed signals to generate the comb filter response.

Abstract: A broadcast signal receiver retrofit apparatus that receives broadcast signals, detects rating or category codes therein and compares the detected codes to a setting set in the retrofit device. If the comparison indicates that the incoming signal has a rating greater than that set or is of an undesired category the broadcast signal is blocked or an audio or visual alert is given. The retrofit device may be tamper-resistant to prevent disabling the device.

Abstract: For a possible simple structure, dispensing with ceramic filters, an FM demodulator for demodulating sound-FM signals comprises a controllable amplifier (1) which receives the sound signals converted to intermediate frequencies, said amplifier having a gain which is adjusted by means of an amplitude control circuit (4) and whose output signal is applied to the amplitude control circuit and to the phase-locked loop which supplies a demodulated sound signal in the locked-in state from its output, said phase-locked loop including a loop filter (7) which comprises a filter (8, 9, 10) of at least the second order with a pole at the frequency f=0, and a limit-detection circuit (13) which feeds back the operating frequency of the phase-locked loop to a predetermined frequency range when said phase-locked loop leaves this frequency range around a predeterminable nominal demodulation frequency, the amplitude control circuit (4) controlling the controllable amplifier (1) in dependence upon its output signal and a signa

Abstract: A television receiver for processing both analog television signals and digital television signals. Specifically, the television receiver contains a RF/IF front end, an analog-to-digital converter that samples a near baseband signal using a "free running" sample rate, and a combined demodulator that demodulates the digitized analog television signals or the sampled digital television signals. The combined demodulator recovers both pilot and pix carriers as well as provide a passband adaptive equalizer that removes ghosts from analog television signals and intersymbol interference from digital television signals.

Abstract: A radio receiver for receiving a selected DTV signal that can be a quadrature-amplitude-modulation (QAM) signal or a vestigial sideband (VSB) signal synchrodynes the received signal to baseband and supplies the baseband signal to an adaptive equalizer. The presence of the pilot carrier accompanying a selected VSB DTV signal is detected for automatically switching the radio receiver for operation in a VSB signal reception mode, in which operating mode the adaptive equalizer is conditioned to respond to training signals included in the initial data segment of each data field of the VSB signal. The absence of pilot carrier accompanying a selected QAM DTV signal is detected for automatically switching the radio receiver for operation in a QAM signal reception mode, in which operating mode the adaptive equalizer is conditioned to operate without relying on the training signals included in the VSB signal.

Abstract: At the transmitter side, carrier waves are modulated according to an input signal for producing relevant signal points in a signal space diagram. The input signal is divided into, two, first and second, data streams. The signal points are divided into signal point groups to which data of the first data stream are assigned. Also, data of the second data stream are assigned to the signal points of each signal point group. A difference in the transmission error rate between first and second data streams is developed by shifting the signal points to other positions in the space diagram. At the receiver side, the first and/or second data streams can be reconstructed from a received signal. In TV broadcast service, a TV signal is divided by a transmitter into, low and high, frequency band components which are designated as a first and a second data stream respectively.

Abstract: A video receiver includes a tuner, a QAM demodulator including a selective gated PLL carrier recovery circuit, and a digital equalizer. The selective gated PLL carrier recovery circuit has a normal operation mode and a selection control mode. The channel changing of the tuner is performed after the selective gated PLL carrier recovery circuit is set to the selection control mode and the digital equalizer is held at its current state.

Abstract: In an SIF signal processing circuit, an SIF signal, which is an FM signal having a carrier frequency equal to a frequency difference between a video IF carrier and a sound IF carrier, is first converted to a lower carrier frequency common to SIF signals of any broadcasting system, and is then demodulated. The SIF processing circuit is provided with a PLL circuit for converting an SIF signal down to a lower frequency, so that an output from the PLL circuit is mixed with the SIF signal. The output of the PLL circuit is varied in accordance with a broadcasting system. A plurality of frequencies can be easily obtained from the PLL circuit simply by controlling a frequency division factor of its frequency divider. Thus, resonators can be dispensed with except for one for generating a reference oscillation signal.

Abstract: A mobile television receiver includes a TV tuner demodulating an incoming TV signal into a first video signal. A first horizontal sync signal is separated from the first video signal. Detection is made as to a quality of an image represented by the first video signal. A second horizontal sync signal is generated. Detection is made as to a difference between a phase of the first horizontal sync signal and a phase of the second horizontal sync signal. The phase of the second horizontal sync signal is controlled in response to the detected phase difference between the first horizontal sync signal and the second horizontal sync signal so that the second horizontal sync signal will be locked in phase and frequency to the first horizontal sync signal. A memory unit stores the first video signal in response to a memory control signal, and outputs the stored first video signal as a second video signal. The memory control signal is generated in response to the detected image quality.

Abstract: A radio receiver uses the same tuner for receiving a selected digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal. The final IF signal is digitized at a rate that is a multiple of both the symbol frequencies of the QAM and VSB signals, for synchrodyning to baseband. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of the multiple of both the symbol frequencies of the QAM and VSB signals by applying automatic frequency and phase control (AFPC) signals developed in the digital circuitry to a local oscillator of the tuner. Baseband DTV signals obtained by synchrodyning the final IF signals have a sample rate higher than symbol rate to facilitate symbol synchronization. The baseband DTV signals are decimated to symbol rate before performing channel equalization to reduce the number of multipliers required in the channel equalization filter.

Abstract: A data transmission apparatus applicable to transmission of data by the use of a cable of a television camera system or the like and capable of ensuring simplified exact demodulation of data transmitted through quadrature modulation. The apparatus comprises a demodulator for outputting detection signals of the quadrature-modulated signal based on reference signals whose phases are each different by a predetermined value from an I-axis reference signal and a Q-axis reference signal in the quadrature modulation; a signal level corrector for correcting the signal levels of the detection signals; and a signal converter for converting the output signals of the signal level corrector to detection signals based on the I-axis and Q-axis reference signals. An equalizer circuit is further included in the apparatus for adaptively equalizing the output signals of the signal converter or the output signals of the signal level corrector.

Abstract: A radio receiver uses the same tuner for receiving a selected digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal. The tuner supplies a final IF signal in a 6-MHz-wide frequency band, the lowest frequency of which is not appreciably more than 2.69 MHz. The final IF signal is digitized at a rate that is a multiple of both the symbol frequencies of the QAM and VSB signals, for synchrodyning to baseband, with the 2.69 MHz difference between the carrier frequencies of QAM and VSB signals being taken into account in the digital synchrodyning circuitry. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of the multiple of both the symbol frequencies of the QAM and VSB signals by applying automatic frequency and phase control signals developed in the digital circuitry to a local oscillator of the tuner.

Abstract: To make it possible to receive a modulated signal which is obtained by suppressing a carrier signal such as a high definition TV signal which is digitally demodulated such as QAM (quadrature amplitude modulation), a receiver of the double super-heterodyne system having the first and second mixers 9 and 13 is a basic constitution. A band pass filter having a flatness in pass band and a small deviation of group delay which will prevent the demodulation of a high definition TV signal from degradation is used a first intermediate frequency filter 11. An SAW filter is used as a second intermediate frequency filter 16. The third mixer 28 for converting a second intermediate frequency signal to a third intermediate frequency signal in frequency is installed and the frequency of the third intermediate frequency signal to be converted is set to a value lower than the frequency of the second intermediate frequency signal.

Abstract: A phase detecting method and associated apparatus for use in a digital vestigial sideband modulation communication device. The phase detecting method has the steps of: digital-filtering I channel data applied from the exterior to restore Q channel data; compensating for a phase of the I and Q channel data by a prescribed phase error value; estimating an I channel level value which approximates the I channel data from the phase-compensated I channel data; and obtaining a difference between the phase-compensated I channel data and the estimated I channel level value, and generating as the phase error value an operation value obtained by multiplying the difference by a sign of the Q channel data.

Abstract: A high-performance voltage controlled oscillator without use of variable capacitance (varicap) diodes which is easy in fabrication in an semiconductor IC form. The voltage controlled oscillator includes:a differential amplifier having a differential pair of transistors (Q.sub.1, Q.sub.2); an LC resonance circuit having a coil (L.sub.0) and a capacitor (C.sub.0); a phase shift circuit for receiving a differential output of the differential amplifier via a buffer of transistors (Q.sub.3, Q.sub.4) and for providing its output for the differential amplifier in a positive feedback mode; and a current control circuit for variably controlling an operating current (Ie) of the phase shift circuit according to a controlled voltage applied from a circuit other than those in the voltage controlled oscillator.

Abstract: A digital TV broadcasting signal is demodulated to obtain a bit stream containing at least a first packet of a first program specific information concerning all TV programs conveyed by the digital TV broadcasting signal and first packets of the TV programs themselves. Selection data is entered for selecting at least one of the TV programs. In response to the selection data, only second packets are selected from among the first packets. The second packets contain only data of the selected TV program. The second packets are decoded. Further, the first packet and the second packets are output without decoding and accepted. The first program specific information is modified into a second program specific information concerning the selected at least one of the TV programs. The modification is executed after the first packet and the second packets are output. Or, the modification is executed before the first packet and the second packets are accepted.

Abstract: A television signal receiver for processing an HDTV signal transmitted in a vestigial sideband (VSB) format includes input complex filters shared by a timing recovery network (30) and a carrier recovery network (50). The filter network includes a pair of upper and lower band edge filters (20, 22) mirror imaged around the upper and lower band edges of the VSB signal for producing suppressed subcarrier AM output signals. The timing recovery network includes a phase detector (28, 38, 62) and responds to an AM signal derived from the two filters (via 26) for synchronizing a system clock (CLK). The carrier recovery network (50) also includes a phase detector (54, 60, 62, 64), and responds to outputs from one or both of the filters for producing an output error signal (.DELTA.) representing a phase/frequency offset of the VSB signal. The error signal is used to reduce or eliminate the offset to produce a recovered baseband or near baseband signal.

Abstract: The present invention aims to provide a CATV converter which can receive both of analog and digital signals. The CATV converter comprises a second mixer (10) coupled with a first filter (13) which attenuates approximately equal frequency to an audio carrier of an upper adjacent channel and approximately equal frequency to a video carrier of a lower adjacent channel, a first amplifier (14) coupled with an output terminal of the first filter (13), and a second filter (15) coupled with the output terminal of the first amplifier (14). The second filter (15) attenuates a video carrier of the upper adjacent channel and an audio carrier of the lower adjacent channel. When an input signal is within a predetermined frequency range, the input signal fed to the input terminal (1) can short-circuit the input and output terminals of the second filter with a high frequency of the input signal.

Abstract: At the transmitter side, carrier waves are modulated according to an input signal for producing relevant signal points in a signal space diagram. The input signal is divided into, two, first and second, data streams. The signal points are divided into signal point groups to which data of the first data stream are assigned. Also, data of the second data stream are assigned to the signal points of each signal point group. A difference in the transmission error rate between first and second data streams is developed by shifting the signal points to other positions in the space diagram expressed at least in the polar coordinate system. At the receiver side, the first and/or second data streams can be reconstructed from a received signal. In TV broadcast service, a TV signal is divided by a transmitter into, low and high, frequency band components which are designated as a first and a second data streams respectively.

Abstract: A QAM/VSB digital receiver is disclosed which includes a source of a QAM/VSB signal. An analog-to-digital converter is coupled to the QAM/VSB signal source, and is further responsive to a sample clock signal. A filter/complement is coupled to the analog-to-digital converter and has a first output terminal which produces a low-pass filtered QAM/VSB signal, and a second output terminal which produces a high-pass filtered QAM/VSB signal complementary to the low-pass filtered QAM/VSB signal. A sample clock generating circuit is coupled to the second output terminal of the filter/complement and produces the sample clock signal in response to the high-pass filtered QAM/VSB signal.

Abstract: An encoding and decoding frequency synchronizing method capable of synchronizing the frequency on the encoder side and that on the decoder side with a small scale configuration is to be provided. A write clock generator 4 generates a write clock synchronized with input video signals. An AD converter 3 converts the input video signals into digital video signals on the basis of the write clock. A frame synchronizer 5 writes the digital signals, and reads them on the basis of a processing clock from a clock generator 6, synchronized with the transmission clock. A high efficiency encoder 7 converts the digital video signals into encoded signals on the basis of the,processing clock. A modulator 9 modulates the encoded signals on the basis of the transmission clock. A clock generator 13 generates a demodulated processing clock on the basis of the transmission clock obtained by demodulation with a demodulator 11.

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: An IF demodulator circuit with IF gain control at a variable time constant, which receives an IF carrier including synchronizing pulses, a black porch and picture information with a positively modulated picture signal, in which the IF picture signal is amplified to a nominal amplitude value by the gain control, and which includes an IF demodulator (3) which demodulates the IF picture signal and supplies a picture signal from the output, while, for a gain control which is independent of DC offsets that may occur in the picture signal, the demodulator circuit is constructed in such a way that a black level detector (8) for generating a black level signal used as a threshold value signal in conformity with the amplitude value of the black porch of the picture signal supplied by the amplitude demodulator (3) is provided, that a DC offset circuit (4) is provided, which raises the DC component of the picture signal and/or lowers the DC component of the threshold value signal in such a way that both signals are offs

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: A HDTV receiver which is improved in its overall performance and is simplified in its configuration, by improving a symbol timing restoring circuit, includes a tuner for selecting a necessary channel from input signals via an antenna, an IF processing & carrier restoring portion for performing an IF process & carrier restoration from the output of the tuner, an analog-to-digital converter (ADC) for converting the output of the IF processing & carrier restoring portion into a digital signal, a timing restoring portion for restoring a timing from the output of the ADC, a 2:1 down-sampler for 2:1 down-sampling the output of the ADC, a sync detector for detecting a sync from the output of the 2:1 down-sampler, a channel equalizer for performing a channel equalization from the output of the 2:1 down-sampler, a phase controller for correcting the phase error from the output of the channel equalizer, an optimal viterbi decoder for performing a viterbi decoding operation from the output of the phase contr