Abstract: A method is described for controlling a data unit receiver or a data unit sender. The data unit receiver or sender comprise a gap response procedure for responding to gaps in the sequence of data units received at the receiver. A reordering detection procedure S12 is provided for detecting a reordering indication indicative of a potential re-ordering of data units in the course of a transmission from sender to receiver, and the gap response procedure is adapted in response to detecting a re-ordering indication.

Abstract: The present document discloses a method and system for improving echo cancellation in the presence of non-linear distortions. A circuit attenuates a transmit signal in one or more spectral bands based on a receive signal. The distorted echo comprised within the transmit signal results from distortions incurred by the receive signal when being rendered by an electronic device. The circuit compares energy values of the receive signal in multiple spectral bands with multiple corresponding spectral band dependent distortion thresholds and determines that for a first spectral band from multiple spectral bands. A first energy value from multiple energy values exceeding a first distortion threshold from multiple distortion thresholds attenuates the transmit signal in one or more spectral bands at higher frequencies than the first spectral band with corresponding spectral band dependent attenuation factors.

Abstract: A receiver suppresses noise simultaneously using a noise suppressor and an automatic gain controller (AGC). The receiver divides a received signal into an audio period and a non-audio period, analyzes whether the noise characteristic of the non-audio period corresponds to a non-static noise or a static noise, and if the noise characteristic corresponds to the static noise, analyzes whether the static noise is caused by a network or a transmitter side terminal. In accordance with the analyzed noise characteristic, the noise suppressor firstly suppresses the noise by determining the noise suppressing intensity, and sends a signal, from which the noise has been firstly suppressed, to the AGC. The AGC secondly suppresses the noise included in the signal. In this case, the threshold value of the AGC is controlled in real time in accordance with the noise characteristic.

Abstract: An apparatus for recovering carrier wave in digital broadcasting receiver and a method therefore are disclosed which are capable of easily detecting and correcting frequency offsets of carrier wave without recourse to a pilot signal in a digital broadcasting receiver receiving a broadcasting signal of vestigial sideband (VSB) modulation system, thereby recovering the carrier wave, wherein, to this end, a complex sine wave whose central frequency is 1/n the symbol frequency is multiplied to generate a real component and imaginary Offset Quadrature Amplitude Modulation (OQAM) signals to calculate a phase error value from the real and imaginary component OQAM signals, to generate a complex sine wave compensating the calculated phase error value, to multiply the complex sine wave by the complex signal outputted from the phase splitter and to convert the complex signal to a baseband signal whose frequency offset is corrected.

Abstract: A coil pair having a transmission coil and a reception coil. The transmission coil is configured to transmit a transmission signal having a carrier. The reception coil is configured to receive from a source a reception signal having the carrier and data, and to significantly suppress the carrier while maintaining coupling with the source at any position along and any position proximate to the reception coil.

Abstract: Carrier frequency detection for an N-ary modulated signal is achieved by digitizing the N-ary modulated signal, frequency shifting the digitized N-ary modulated signal to prevent aliasing, raising the frequency-shifted signal to the Nth power, transforming the raised signal to frequency domain data and determining an initial maximum frequency peak, iteratively fine shifting the frequency of the N-ary modulated signal around the initial maximum frequency peak and repeating the raising, transforming and determining steps to obtain a plurality of maximum frequency peaks, and calculating the carrier frequency from the maximum frequency peaks and the total related frequency shift.

Abstract: According to the invention, a circuit arrangement for gaining a 38 kHz stereo subcarrier and a 57 kHz RDS carrier for decoding a stereo signal comprised in a demodulated FM signal and/or an RDS signal comprised in a demodulated FM signal, having a simple structure with only one PLL and particularly only one voltage-controlled oscillator (2) is characterized in that the arrangement comprises a phase-locked loop with a loop filter (1), a voltage-controlled oscillator (2), a first phase detector (3) which receives a reference signal having a reference frequency, and a second phase detector (4), which receives the FM signal, the output signal of the voltage-controlled oscillator (2) being coupled to both phase detectors (3, 4) in a form divided down by means of dividers (6, 9; 10, 11), and the signal fed back to the second phase detector having a frequency of 19 kHz, in that dividers (9, 10, 12) are provided, by means of which the output signal of the voltage-controlled oscillator (2) is divided down and which su

Abstract: Methods and apparatus are provided for determining aperture phase distributions for use in radiating signals with an active phased array antenna having multiple beams and multiple carriers. Distinct initial phase distributions corresponding to the carriers are allocated. The initial phase distributions are modified for each of the carriers to generate respective radiation patterns that substantially correspond to respective coverage areas in accordance with amplification and radiation of signals having the initial phase distributions. The modified phase distributions are optimized to simultaneously increase carrier-signal power and reduce an intermodulation product radiated in the respective coverage areas in accordance with amplification and radiation of signals having the modified phase distributions.

Abstract: A power amplifier system and method for locating carrier frequencies across a frequency band, identifying the modulation format of each carrier, and locating and suppressing undesired intermodulation distortion (IMD) products generated by the power amplifier. The system includes an amplifier for amplifying RF carrier signals in a main signal path, a variable phase shifter and variable attenuator on a feed forward path, and a tunable receiver that digitizes a portion of the frequency band to baseband. The tunable receiver includes a tunable voltage controlled oscillator which provides an oscillating frequency to a mixer and is phase-locked to a highly stable reference oscillator. The mixer downconverts a desired RF based on the oscillating frequency to IF. A filter passes only a selected portion of the IF signals, and the filter has a passband sufficient to discern both narrowband and wideband carriers and their associated IMD products.

Abstract: The radio resource management server 1 receives radio link quality information measured by the radio base station 2 and radio link quality information measured by the radio base station 3 and thus detects the occurrence of interference. Upon the occurrence of the interference, the transmission power of the radio base station causing the occurrence of interference is controllably reduced to suppress the interference. In the method of controllably varying the transmission power of a radio base station, depending on the number of radio terminals or traffic volume, oscillation of a service area occurs. However, according to the present invention, the transmission power is changed on the occurrence of interference, without depending on the number of radio terminals or traffic volume, so that the area oscillation does not occur after the transmission power has been once stabilized.

Abstract: An apparatus for communicating, over a single transmission medium, two signals of substantially the same center frequency. The apparatus offsets in frequency one of the signals by combining the signal with the signal from a local oscillator. The apparatus then transmits the two signals, one offset from the other, as well as the signal from the local oscillator to allow for recovery of the two signals with a precise correction for the offset. In particular, the transmission medium is an optical fiber and the two signals are a main RF signal and a diversity RF signal received, respectively, by a main element and a diversity element of a diversity antenna system. The invention is of use, for example, in providing to a microbase station a main RF signal and its diversity RF signal received at a diversity antenna system remote from the microbase station and connected to the microbase station by an optical fiber.

Abstract: A front end circuit for an RF dual band GSM/DCS phone includes a first channel including an elliptical high-pass filter, a first SAW filter, and a low noise amplifier and a second channel including a second SAW filter and a second low noise amplifier. The output of each channel is alternately switchable to a single-side band mixer circuit. This front end circuit arrangement provides significantly reduced cost and part count over other approaches.

Abstract: A multi-carrier radio system in which pairs of subcarriers are positioned in frequency such that each subcarrier in a pair is the image of the other subcarrier in the pair. By making each subcarrier the image of another subcarrier, the radio system of the present invention permits highly integrated low-IF transceiver implementation. In an exemplary embodiment, a multi-carrier transceiver includes an integrated receiver comprising a first mixer for mixing an input signal with a local oscillator signal to produce an in-phase downconverted signal. Additionally, a first phase shifter phase-shifts the local oscillator signal to produce a quadrature local oscillator signal, and a second mixer mixes the input signal with the quadrature local oscillator signal to produce a quadrature downconverted signal. Thereafter, a second phase shifter phase-shifts, or rotates, the quadrature downconverted signal to produce a rotated quadrature downconverted signal.

Abstract: A method for decoding a suppressed-carrier modulated signal in the presence of a pilot tone, comprising the steps of:extracting the pilot signal from the modulated signal;obtaining the suppressed carrier by multiplying the pilot signal by the pilot signal in quadrature;adjusting the level of the suppressed carrier; andreconstructing the modulating signal.

Abstract: An electro-optic modulator and a method for its use, in which an optical carrier is effectively suppressed for transmission of a radio-frequency (rf) modulating signal over an optical communication link, to provide improved demodulator performance. A carrier component is recovered from the modulator, amplified, and reused, to minimize the effect of optical carrier losses. In one embodiment of the invention, a modulator (10) with complementary output ports (20 and 22) generates a carrier-suppressed output (FIG. 2B) containing rf sidebands from one port (20) and a strong carrier component (FIG. 2C) from the other output port (22). The carrier component is filtered in a residual sideband filter (14), amplified in an optical amplifying medium (12) and returned to the modulator (10) as its carrier input. In a second embodiment of the invention, a modulator (30) with a single output port produces rf sidebands and a suppressed carrier component (FIG.

Abstract: A method and an arrangement for synchronization in OFDM modulation. Frequency errors of an IF clock and a sampling clock are controlled by estimating the deviation of the sampling clock and, respectively, the IF clock for two subcarriers with different frequencies. According to the invention, the frequencies are chosen symmetrically around zero and the absolute phase errors are detected for both subcarriers. Timing errors and phase errors are formed from the absolute phase errors in order to generate two control signals. The first control signal is formed from the deviation of the sampling clock and the timing error for controlling the sampling clock while the second control signal is formed from the deviation of the IF clock and the phase error for controlling the IF clock.

Abstract: An FM stereo radio data-system receiver has a front end including an FM discriminator that produces a composite signal composed of an AM stereo signal, including a 19 KHz pilot, and an AM digital-data signal. A dual-bandwidth phase locked loop (PLL) locks onto the pilot and serves both, as the decoder of the stereo portion of the composite signal, and as a generator of a strong stable 38 KHz carrier for use in regenerating the bit rate clock signal and for decoding the data-symbol signal of the digital-data portion of the composite signal. Advantages include economy of circuitry, a simpler and less costly high pass filter, and greater reliability in the decoding of the data signal.

Abstract: A system for combining AM and FM transmissions. In-band, On-channel, FM Digital Audio Broadcast (IBOC FM-DAB) allows simultaneous transmission of DAB and FM over existing FM allocations without interfering with conventional analog FM signals. The utility of existing FM spectrum allocations is therefore enhanced.

Abstract: A carrier is received containing a plurality of signals within a first frequency band, for example television signals within the cable television band. The signals are upconverted to a second frequency band above the first band wherein a selected one of the upconverted signals will reside at an intermediate frequency within the second band. The selected upconverted signal is input to a homodyne detector operating at or near intermediate frequency. In-phase and quadrature signals output from the homodyne detector are digitally processed to recover a baseband signal.

Abstract: In transparent tone-in-band communication systems a notch in the frequency band is usually formed and then the resulting spectrum is translated in frequency to an intermediate frequency range as part of the transmission process. In a transmitter of the present invention a more simple arrangement is used in which the notch is formed directly in an intermediate frequency range by using mirror filters to divide an input signal into two portions and supply respective mixers, each having one output sideband in the intermediate frequency range. The mixers receive different reference frequencies and the mixer outputs are supplied to a summing circuit whose output is passed to a band pass filter to remove the unwanted sidebands. The original frequency spectrum is restored at the receiver by mixer processes of shifting the two selected sidebands similar to, but the inverse of, those used in the transmitter.

Abstract: A system and method for detecting the level of random noise contained in a band-limited amplitude-modulated signal. A sychronizing signal is produced which is .pi./2 out of phase with respect to the carrier of the amplitude-modulated signal. The amplitude-modulated signal and the synchronizing signal are multiplied together. Only a low frequency component is extracted from the multiplication output, and the low frequency component is taken as an indication of the level of the random noise contained in the amplitude-modulated signal.

Abstract: An improved system and method for modulation, demodulation and signal processing for single sideband communications systems which provides correction for the adverse effects of rapid fading characteristics in a mobile environment. The system provides modulation through a modified Weaver modulator in which the audio input is processed to produce an output in the form of an upper sideband having a pilot tone in a spectral gap at approximately midband. The receiver includes a modified Weaver demodulator and a correction signal generating circuit which processes the received faded audio input and pilot tone to produce a correcting signal. The correcting signal is mixed with the received signal to regenerate unfaded versions of both the signal and pilot by removing random amplitude and phase modulations imposed on them by the fading.

Abstract: A television sound receiving circuit for at least one sound channel contained in an RF signal converts the transmitted or already down-converted television signal as a composite signal to the baseband in a single-sideband demodulator circuit using the "phasing method", separates the first sound channel, corresponding to a lower sideband, and the second sound channel, corresponding to an upper sideband, and produces first and second sound signals at the desired frequency by subsequent frequency demodulation. Also shown are the interfaces for possible digitization and an advantageous use of the interfaces in which picture and sound signals are digitized together. The data can be combined into a single data stream which can be transferred over a bus system and is separable into the individual components if required.

Abstract: An apparatus and method are provided for receiving and reproducing stereo television sound. A transmitted television signal is received that contains a first component comprising the sum of first and second stereophonically related audio signals and a second component comprising the difference between the first and second stereophonically related audio signals. The first and second components are converted to produce a first sound carrier centered at a first intermediate frequency and a second sound carrier centered at a second intermediate frequency. The first component is detected from the first sound carrier at the first intermediate frequency. The second component is detected from the second sound carrier at the second intermediate frequency. The detected first and second components are combined to produce a left channel audio output and a right channel audio output.

Abstract: A phase locked loop circuit for use in a heterodyne receiver for stably demodulating a carrier-suppressed double-sideband signal such as a 2-phase or 4-phase PSK signal. The phase locked loop circuit comprises a reference oscillator oscillating at a frequency corresponding to an intermediate frequency, and the frequency difference between the reference frequency and the input frequency is detected by a Costas loop, a signal indicative of the frequency difference being fed back to a local oscillator through a loop filter thereby stabilizing the intermediate frequency.

Abstract: A receiver unit in a radio communication system in which a transmitter unit outputs transmission data, modulated in accordance with a multilevel QAM method and containing a leakage carrier by addition of a DC offset signal to either one of the quadrature components forming the transmission data, to the receiver unit through a transmission line, including: means for receiving the transmission data; means for branching a signal received at the transmission data receiving means into first and second signal components forming the multilevel QAM data, each including the leakage carrier having a phase difference of .pi.

Abstract: A radio frequency transmission system contains at least one coherently modulated information signal, for example, a T.V. signal. At a transmission, the information signal is combined with two pilot tones, F1 and F2, related by the equation F1=N/M F2, where N and M are integers. The combined signal is suppressed-carrier modulated at microwave frequencies and transmitted to a receiver. At the receiver, the signals are demodulated by a local oscillator. The two pilot tones are then separated from the information signal and are compared to each other. The local oscillator frequency is controlled in response to this comparison such that the pilot tones at the receiver bear the same relationship to each other that they had at the transmitter. When this is achieved, the local oscillator frequency is the same as the suppressed-carrier frequency and co-channel interference is prevented.

Abstract: In a synchronous video detector circuit using a phase-locked loop, the synchronous detection of a video IF signal is effected with a synchronous carrier signal reproduced by the PLL including a voltage-controlled oscillator. Each of a phase comparator of the PLL and a synchronous video detector has its input terminal connected to an output terminal of a video IF amplifier by untuned coupling, and arranged on the output side of the synchronous video detector is a phase-locked mode detector for detecting that the PLL is in its phase-locked mode. The phase-locked mode detector is adapted to control the band width of a low-pass filter of the PLL in either a narrow band mode or a wide band mode and the low-pass filter is controlled to operate in the narrow band mode only when the PLL is in the phase-locked mode of operation.

Abstract: A cosine signal corrector circuit as for use in a decoder for a system wherein an information signal is transmitted in the form of one trigonometric transform function of that signal. The second trigonometric transform function signal, required for decoding the information signal, required for decoding the information signal, is obtained by first deriving the Hilbert transform of the transmitted signal and phase inverting it, producing an approximate second transform function signal. The decoder produces the sum of the squares of the two transform function signals, and the difference between that decoder output and 1.0 is an "error" signal. Under the control of the signum signal of the approximate second transform function signal, the error signal is added to the approximate second transform function signal to produce an accurate second transform function signal.

Abstract: A receiver for tracking and demodulating several types of phase modulated communications, either analog or digital data, for either residual carrier or suppressed carrier signal and for phase modulation or keying of two, four or higher phase angles, from 0.degree. through 360.degree.. A carrier component signal and a converted series sideband component signal are obtained from the incoming signal and summed to produce a carrier tracking signal, permitting more accurate tracking of the above types of phase modulated data.

Abstract: A system and a receiver for transmission of signals by a double sideband amplitude modulated carrier with the carrier suppressed, known as a DSBSC wave, without reinsertion of the carrier at the receiver. In the receiver the DSBSC wave is amplified, demodulated by a full-wave rectifier, and the rectifier output reversed in polarity at instants of successive zero crossings of the signal, to produce the signal free from extraneous components.

Abstract: A process for the demodulation of an amplitude modulated signal composed of two suppressed carriers, at a same frequency F and in phase quadrature, which are respectively modulated by two modulation signals, the modulated signal being preceded by a reference signal at frequency F, bysampling the reference signal and the modulated signal, according to a frequency m.F (m being an integer);determining a polar angle .psi..sub.t of a rotating vector representing the reference signal, at time t, by calculating: ##EQU1## where x(t) and x(t-(1/4F)) are the values of two successive samples of the reference signal;determining polar coordinates (.rho..sub.t, .theta..sub.t) of a rotating vector representing the modulated signal, at time t, by calculating: ##EQU2## where y(t) and y(t-(1/4F)) are values of two successive samples of the modulated signal,calculating .gamma.=.theta..sub.t -.omega..sub.t -.phi..sub.o, where .phi..sub.o is the phase displacement between the reference signal and one of the carriers,calculating .

Abstract: A receiver for demodulating a single sideband signal which is subject to rapid phase jitter employs a Hilbert splitter for obtaining the Hilbert transform of the single sideband signal, and a local oscillator for signal demodulation. A post-oscillator feedback loop instantaneously derives the amount of phase jitter in the single sideband signal, and employs the derived phase jitter to adjust the phase of the local oscillator so that the local oscillator tracks the single sideband signal.Instantaneous derivation of the phase jitter is obtained because all post-oscillator signal manipulations are algebraic; post-oscillator Hilbert transform generation is not required. A first embodiment derives the exact amount of phase jitter. A second embodiment, more simple than the first, derives the approximate amount of phase jitter.

Abstract: A feedback circuit for controlling the phase of a local oscillator provided with frequency adjusting means and delivering a local carrier wave for demodulating a data signal transmitted by single side band amplitude modulation, the said feedback circuit comprising at least one sign multiplier (21) producing the product of the sign of the local demodulation carrier shifted by a phase difference of .pi./4 multiplied by the sign of the data signal to be demodulated, followed by a sign coincidence auto-correlator (22) which controls the said frequency adjusting means and correlates two versions of the signal delivered by the sign multiplier (21), one of the two versions being delayed relative to the other by an odd multiple of one fourth of the period of the carrier used for the amplitude modulation on transmission.

Abstract: An automatic fine tuning (AFT) circuit includes a frequency discriminator for discriminating an intermediate frequency signal, a capacitor supplied with the discriminated intermediate frequency signal to produce an AFT voltage thereacross, a comparator circuit for comparing the AFT voltage with a reference voltage, a first switching transistor controlled by the comparator circuit and which supplies and charges the capacitor with the reference voltage during a channel selection operation when the AFT voltage is less than the reference voltage, a second switching transistor controlled by the comparator circuit and which connects the capacitor to ground to discharge the same during a channel selection operation when the AFT voltage is greater than the reference voltage, and a third switching transistor for rendering the comparator circuit operative during a channel selection operation and inoperative during an AFT operation.

Abstract: In receiving apparatus for a double-sideband amplitude-modulated wave, a synchronous detector which samples the modulated wave for short periods centered on instants of peaks of the carrier at regularly-occurring intervals, with a sampling frequency greater than the Nyquist frequency for the modulating wave, equal to the carrier frequency divided by an integer, and reconstructs the modulating wave from the sequence of samples in a reconstruction filter. This detector has a high output signal-to-noise ratio and produces a distortionless output with positive or negative overmodulation, and with reduced or suppressed carrier.

Abstract: A single sideband signal can be demodulated by using sampled data techniques. An intermediate frequency (IF) radio signal is split into two branches and is sampled by two sample and hold devices; each sample and hold device operates at a rate that is not only a submultiple of the carrier frequency, but is also at least twice the information bandwidth. Prior to, or during sampling of one branch (the quadrature branch), a Hilbert's transform is performed upon the IF signal which results in the output of the two sample and hold devices being in phase quadrature. A phase shift of 90.degree., using a baseband finite impulse response Hilbert's transform filter, is performed upon the output signal of the quadrature branch's sample and hold device. The sum of the inphase sampled signal and the filtered quadrature phase sampled signal produces the demodulated lower sideband while the difference between the two produces the demodulated upper sideband.

Abstract: The local signal generation arrangement employed in a radio communication system for transmitting and/or receiving an upper sideband (USB) and a lower sideband (LSB) signal, but not simultaneously, employs a method in which the generation and/or detection of both USB and LSB signals is accomplished by utilizing only one bandpass filter, a so-called single sideband (SSB) filter, together with a balanced modulator arranged to receive a carrier signal produced from an oscillator whose frequency is accordance with the characteristic frequency of either of a pair of crystal resonators, which correspond to the upper cut-off and the lower cut-off frequencies of the SSB bandpass filter, respectively. The output signal from the said SSB filter is referred to herein as the intermediate frequency (IF) signal.The local signal generation arrangement includes a phase-locked loop (PLL) including at least a phase comparator, a low pass filter, and a voltage-controlled oscillator (VCO).