Abstract: A system and method for determining an in-ear status of a wearable audio device includes determining that the device is in motion by monitoring a first sensor (e.g., an accelerometer) and determining that an acceleration is greater than an acceleration threshold. Once motion is determined, a second sensor (e.g., a capacitive sensor) is activated; contact with a body is determined based on contact data from the second sensor (e.g., a capacitance being greater than a capacitance threshold). Once contact is determined, a third sensor (e.g., an infrared sensor) is activated; proximity to the body is determined based on infrared data from third sensor (e.g., infrared data being greater than an infrared threshold). Once proximity is determined, the device changes its status to in-ear.

Abstract: A computing device may be configured to output a digital audio stream to an audio playback system for rendering as sound over speakers. The sound may be sampled. Based at least in part on a quality of the sampled sound, the data rate of the digital audio stream may be reduced by reducing a sampling rate and/or by reducing a number of bits per sample. A reduced sampling rate may be determined based on a computed maximum sampling rate of the audio playback system, and/or a reduced number of bits per sample may be determined based on a computed maximum number of bits per sample of the audio playback system. The maximum usable sampling rate and maximum usable number of bits per sample may be determined based on an upper usable frequency within a frequency spectrum of the sampled sound.

Abstract: A clock synthesis system may include a feed forward divider circuit configured to divide a source clock signal by one of a plurality of integers in response to a select signal to generate a reference clock that is synchronous to a synchronous pulse; a modulator that modulates the select signal in response to at least a difference value; a multiplier circuit that frequency multiplies the reference clock to generate an output clock; and a timing circuit that generates the difference value in response to the source clock and synchronous pulse.

Abstract: A method for processing an input composite signal includes tracking a signal component of the input composite signal according to a frequency of a pilot signal to generate a locked signal, detecting an amplitude of the signal component to generate a detecting result, and generating a reproduced pilot signal according to the detecting result and the locked signal. A frequency and a phase of the locked signal are substantially identical to the frequency and a phase of the pilot signal.

Abstract: A switch controller is provided that uses one or more capacitors to generate a slow turn on/slow turn off switch control signals to suppress audible switching noise in an audio switch. In some embodiments, an analog inverter and a capacitor are used to generate the switch control signals, while in other embodiments two capacitors are used to generate the switch control signals. To conserve power between switching states, routing logic is provided that ties the switch control signals to respective voltage rails and disables selected portions of the switch controller.

Abstract: There is provided a hearing aid that reduces a possibility of loss. The hearing aid of the present invention includes a microphone 101 configured to collect sound; a hearing aid processing unit 102 configured to perform hearing aid processing to an input signal from the microphone 101; a speaker 103 configured to output a signal processed by the hearing aid processing unit 102 to the outside; and a drop detection unit 104 configured to detect drop by reference to the input signal from the microphone 101.

Abstract: Disclosed herein are systems, methods, and non-transitory computer-readable storage media for allowing independent control of a formant position and inharmonic content in sound synthesis. In one aspect, this allows continuous shifting of the formant across a spectrum without producing any inharmonic spectral content. In a second aspect, this also makes it possible to generate sound with a defined inharmonic content amount and still move a formant position without changing the inharmonic content amount or to continuously change the amount of inharmonic content without significantly changing the formant position. The disclosed technology uses multiple modulators that are applied to a carrier signal by a weighted sum of their outputs.

Abstract: Exemplary embodiments include a frequency modulation (FM) transmitter and a non-FM receiver, which may be implemented on the same IC chip. The FM transmitter may include a digital FM modulator, a lowpass filter, an amplifier, and an LC tank circuit. The digital FM modulator may receive a digital input signal, perform FM modulation with the digital input signal, and provide a digital FM signal. The lowpass filter may filter the digital FM signal and provide a filtered FM signal. The amplifier may amplify the filtered FM signal and provide an output FM signal. The LC tank circuit may filter the output FM signal. The digital FM modulator may perform FM modulation by changing a variable divider ratio of a multi-modulus divider within a PLL. A delta-sigma modulator may receive the digital input signal and generate a modulator output signal used to obtain the variable divider ratio.

Abstract: The invention provides a sound processing device. In one embodiment, the sound processing device comprises a first microphone, a first analog-to-digital converter, a second microphone, and a second analog-to-digital converter. The first microphone detects a first sound pressure to generate a first analog audio signal. The first analog-to-digital converter converts the first analog audio signal from analog to digital to obtain a first digital audio signal. The second microphone detects a second sound pressure to generate a second analog audio signal.

Abstract: Signal of a channel selected in accordance with a cue instruction is supplied to a cue bus. Cue signal processing section provided in the cue bus can perform one or more signal processing operations, selected from among a predetermined plurality of different signal processing operations, such as “Delay”, “Insert” and “Equalizer”. For each of a plurality of channel types, a set of setting information is stored which contains information for setting ON or OFF of individual ones of the plurality of different signal processing operations. The set of setting information corresponding to the type of the channel selected via the cue instruction is referenced, and one or more signal processing operations is determined in such a manner that each signal processing operation set in an ON state in the setting file in correspondence with the type of the selected channel is performed on the signal supplied to the cue bus.

Abstract: There is provided a communication apparatus capable of reducing power consumption. The communication apparatus in accordance with the present invention includes a synchronization detection block 30 which detects synchronization by performing a receiving process using a plurality of clocks whose phase differs from each other with respect to synchronization information contained in a first frame as well as identifies the synchronization detected clocks as candidate clocks to be selected; a clock phase selection block 40 which selects a sampling clock to be used for sampling of the transmission signal from the candidate clocks to be selected, selects a stop clock separated by a predetermined phase from the selected sampling clock, and outputs an instruction for the stop clock; and a clock gate unit 60 which, terminates supplying the stop clock from the plurality of clocks to the synchronization detection block 30 as well as supplies other clocks to the synchronization detection block 30.

Abstract: An electronic appliance includes a microphone which detects a clapping sound, an edge signal extractor, an edge pulse generator and a judgment processing circuit. The judgment processing circuit generates a first gate having a first time width to detect whether or not a second clapping sound has been generated after elapse of a first predetermined time from a first time when the microphone detects a first clapping sound and the edge pulse generator generates the first edge pulse corresponding to the first clapping sound. Subsequently, the judgment processing circuit generates a second gate having a second time width to detect whether or not a third clapping sound has been generated after elapse of a second predetermined time from a second time when the edge pulse generator generates the second edge pulse corresponding to the second clapping sound.

Abstract: An apparatus and a method of automatically compensating a difference between audio signals of an analog broadcast and a digital broadcast depending on a difference of a modulation degree of an analog audio signal and a digital audio signal.

Abstract: A method for processing an input composite signal includes tracking a signal component of the input composite signal according to a frequency of a pilot signal to generate a locked signal, detecting an amplitude of the signal component to generate a detecting result, and generating a reproduced pilot signal according to the detecting result and the locked signal. A frequency and a phase of the locked signal are substantially identical to the frequency and a phase of the pilot signal.

Abstract: When a plug of a monaural microphone is connected to an external microphone input section, a right channel terminal is connected to a GND terminal, and a voltage Vdet will be a GND potential. A DC voltage detection section detects this GND potential, and outputs, for example, an H level signal as a detection signal. In response to this detection signal, a system control section controls a DSP so that, for example, an audio signal of the left channel is recorded by use of both right and left recording channels.

Abstract: The present invention provides a system and a method to prevent undesired sounds during FM modulator turn on. The system includes an RF attenuator circuit, a delay switch circuit, an RF ramp up circuit, and audio ramp up circuit. The RF attenuator circuit significantly reduces the RF signal from the FM modulator when the FM modulator is initially turned on, which significantly reduce whistle caused by the RF signal from the modulator beating with the local oscillator in the radio receiver. After allowing time for the PLL to lock onto the RF signal, the time delay switch circuit becomes active and charges the RF ramp up circuit. The RF ramp up circuit gradually increases the RF signal by gradually deactivating the RF attenuator circuit. The gradual increase of the RF signal is slower than the response time of the radio AGC, thereby preventing any pop as the RF signal is provided to the radio receiver.

Abstract: To demodulate the RDS signal, the stereo-multiplex signal is multiplied in a first branch by the in-phase component of an oscillator, filtered by a low-pass filter while decimated in its sampling rate and filtered by a high-pass filter, while in a second branch it is multiplied by the quadrature component of the oscillator, filtered by a low-pass filter, decimated in its sampling rate, and filtered by a high-pass filter. An error signal to control the oscillator is calculated from the high-pass-filtered signals and the RDS bit clock. A clock generator generating the RDS bit clock is controlled by the first high-pass-filtered signal and by the oscillator. An RDS decoder, to whose input the first high-pass-filtered signal is applied, and an arithmetic unit which calculates the error signal from the high-pass-filtered signals and from the RDS bit clock are both clocked by the clock generator. The RDS data are retrievable from the output of the RDS decoder.

Abstract: A peak to peak detector circuit for use in an audio system comprises a first amplifier having an input terminal for receiving an L+R AC audio signal and an output terminal which is serially coupled to a resistor in series with a capacitor for generating a variable dc voltage having a time vs. amplitude relationship corresponding to the input L+R AC audio signal. A clamping diode having a cathode electrode coupled to a reference potential and having an anode electrode coupled to the capacitor operates to limit negative amplitude excursions associated with the variable dc voltage to a predetermined minimal value. A rectifying diode having a cathode electrode coupled to the anode electrode of the clamping diode, and an anode electrode coupled to a second capacitor to charge the second capacitor responsive to the amplitude of said variable dc voltage operates to produce a dc output signal proportional to the peak to peak amplitude of said L+R audio signal.

Abstract: A digital FM signal generator allows the generation of a modulated FM signal for broadcasting without the need for an analog modulator. The signal generator includes a digital signal processor which receives left and right signals from left and right signal channels and interpolates the signals to create a composite base band signal. The composite base band signal is then used by a numerically controlled oscillator to modulate a digital carrier signal. The result is a digital modulated FM RF signal which is then converted to an analog signal for broadcasting.

Abstract: Acoustic signals received by the ears are controlled by feeding back and filtering the signal to be applied to the speaker, rather than by use of a feedforward filter. The feedback filter may incorporate an electrical model of the speaker-to-ear transfer function to force the ear signals to a desired ratio of amplitudes and phases as a function of the frequency. The signals to be output to the right and left channels are fed back through a filter to obtain a feedback signal. The feedback signal is subtracted from one input channel and added to the other input channel to provide the output signals. This technique may be used both in stereo spreading and in three-dimensional localization of a monaural sound source. By using feedback instead of feedforward, the system can be readily adapted to different playback environments. Through a simple adjustment of the electrical model of the speaker-to-ear transfer functions, this system automatically provides the desired ear signals.

Abstract: In a digital audio broadcast receiver a digital audio transmission signal is supplied to a demodulator which provides demodulation samples. The demodulation samples are de-interleaved in a first section of a de-interleaving memory. After having been de-interleaved, demodulation samples are transferred to a second section of the de-interleaving memory. This transfer is effectuated in bursts via a relatively small buffer which stores the bursts. The second section of the de-interleaving memory effectively constitutes a relatively large buffer. De-interleaved demodulations samples are regularly read from the second section and supplied as a regular stream to a Viterbi decoder by means of a relatively small first-in first-out register.

Abstract: A radio frequency (RF) modulation apparatus for modulating input video and audio signals into a television broadcast signal is provided. The apparatus includes a buffer amplifier, a decoder, a switching device, and an RF modulator. The buffer amplifier amplifies and stores the input audio signal as a stored audio signal. The decoder inputs and decodes the stored audio signal to produce a decoded audio signal. The switching device inputs the stored audio signal from the buffer amplifier and the decoded audio signal from the decoder and selectively outputs either the stored audio signal or the decoded audio signal as a selected audio signal. Specifically, the stored audio signal is output as the selected audio signal if the input audio signal corresponds to a stereophonic audio signal or an audio multiplexing signal. On the other hand, the decoded audio signal is output as the selected audio signal if the input audio signal corresponds to a mono audio signal.

Abstract: The method for obtaining the quality signal includes multiplying a digital multiplex signal (MPX) by respective reference carrier signals mutually phase shifted by 90.degree. to each other, but otherwise equal, to form a pair of mixed signals (Imr1,Imr2); multiplying the mixed signals (Imr1, Imr2) by respective correction signals (G38c,G38s) to form a pair of corrected mixed signal (Ims1,Ims2); separately multiplying the digital multiplex signal (MPX) by each of two reference pilot signals mutually shifted in phase by 90.degree.

Abstract: The FM stereo broadcasting apparatus has a sampling frequency converter for receiving a digital input signal having an L (left audio)-signal and an R (right audio)-signal and for converting the digital input signal so that its sampling frequency is equal to either a frequency of a subcarrier of a composite audio signal or a first sampling frequency of a first sampling signal for the operation of a composite audio signal generator, a sampling signal generator for generating the first sampling signal for the operation of the composite audio signal generator having the first sampling frequency which is equal to 2.sup.

Abstract: A simple and effective stereophonic transmission system (1) wherein the transmitter (2) alternatively encodes successive block periods of a block signal with samples of the left-hand channel signal (L.sub.in) and the right-hand channel signal (R.sub.in). At receiver side, the left-hand and right-hand stereo signals are decoded from the encoded block signal by alternate integration and peak detection of positive and negative received pulses, the pulse widths of the received pulses corresponding to amplitudes of the transmitted samples. When detecting the pulses for one stereophonic channel, the corresponding other stereophonic channel is blocked.

Abstract: An FM signal phase-shifted by 90.degree. and an FM signal not phase-shifted are supplied to a multiplier to demodulate a stereo composite signal. A 90.degree. phase shifting circuit has a first oscillation circuit whose phase shift amount varies according to a timing at which the amount of a current flowing through a charging and discharging capacitor is changed. A multiplexer is provided to process the stereo composite signal to output left and right channel signals. The multiplexer has a second oscillation circuit for generating a signal multiplied by the stereo composite signal to extract the left and right channel signals from the composite signal. The first and second oscillation circuits each have a differential amplifier. The constant current of the constant current source of each differential amplifier is set by trimming-regulate it by a regulating circuit.

Abstract: In a radio receiver with digital signal processing, a stereo multiplex signal received and the useful signals derived therefrom are processed in digital form at a first sampling rate. The subsidiary signals derived from the stereo multiplex signal are at least partly processed at a second sampling rate that is smaller than the first sampling rate. The sampling rate of the processed subsidiary signals are reduced to the first sampling rate with the processed subsidiary signals, acting as control signals with the first sampling rate, affecting the stereo multiplex signal and the useful signals.

Abstract: A pilot signal detection circuit comprises: a PLL circuit for generating a reference signal whose frequency is same as and phase-synchronized with a carrier of a pilot signal extracted from broadcasting waves; a sync-detector for sync-detecting the carrier by using the reference signal; a frequency signal generator for generating a first pair of signals having a frequency assigned to sound multiplex broadcasting and a phase difference of 90 degrees and a second pair of signals having a frequency assigned to stereophonic broadcasting and a phase difference of 90 degrees; multiplies for multiplying the signal output from the sync detector by the output signals from the frequency signal generator; squaring circuits for squaring the output signals from the multipliers; LPFs for filtering the output signals from the squaring circuits; an adder for adding the outputs of the LPFs, and a detector for detecting the pilot signal by comparing the output of the adder with a predetermined reference level.

Abstract: In a circuit for decoding a multiplex signal in a stereo receiver, where the multiplex signal contains a composite signal (L+R) in the base band, a subcarrier modulated with a difference signal (L-R), and a pilot signal with half the frequency of the subcarrier, the multiplex signal in digital form is multiplied (2, 3) by a reference carrier generated with a sampling clock signal (14) produced in the radio receiver, where the reference carrier is present in two phase positions shifted 90.degree. with respect to each other. The mix or product signals resulting from this multiplication are multiplied (4, 5) by one correction signal each, thus forming corrected mix signals. The corrected mix signals are added (6) and supplied to a matrix circuit (8, 9), together with the composite signal, to create respective stereo audio channel signals (L, R).

Abstract: A device and method for composite signal decoding is provided in which an analog to digital converter (18) digitizes an incoming composite signal. The digitized signal is transmitted to a least mean squares estimator (24). Least mean squares estimator (24) generates composite estimates which are filtered in filter (26). A phase extractor (28) extracts information on the phase between the sampling frequency and the incoming composite signal. Any phase shift existing between a left channel and right channel of the incoming composite signal are compensated in phase compensator (30). A channel extractor (34) extracts a sum and a difference of the left and right channels based on the phase information generated by phase extractor (28). An interpolator (36) adds and subtracts the information generated by channel extractor (34) to isolate the left and right channel signals.

Abstract: A digital FM stereo decoder uses the phase characteristics of linear phase FIR filters, together with a trignometric operation, to generate a 38 kHz subcarrier signal from a 19 kHz pilot. The subcarrier signal is mixed with the input composite signal from which the pilot has been removed to shift its L-R component to baseband; the linear phase FIR filters also maintain phase coherence between the subcarrier and the composite signals. A low distortion output is obtained without the use of a phase locked loop for the regeneration of the subcarrier signal.

Abstract: A method is provided for decoding a composite signal which includes receiving a composite signal including a pilot signal at a pilot signal frequency, and first and second information modulated with a subcarrier at a harmonic of the pilot frequency. The composite signal is sampled at a preselected sampling frequency. The sampled composite signal is mixed down with a reference signal of approximately the same frequency. The mixed down pilot signal is extracted from the mixed down composite signal, the amplitude and sign of the mixed down pilot signal proportional to the phase difference between the pilot signal and the reference signal. The phase of the reference signal is adjusted as a function of the amplitude and sign of the mixed down pilot signal such that the reference signal is approximately 90.degree. out of phase with the received pilot signal. The sample of the composite signal taken closest to the start of a period of the pilot signal is identified.

Abstract: An FM receiver includes an FM discriminator having a comparator for converting the FM signal to a series of discrete square-wave pulses all of the same amplitude and of a repetition rate varying with the frequency of the FM signals; and an integrator circuit which integrates the series of monopolar square-wave pulses to produce an output signal having an amplitude varying with the repetition rate of the square-wave pulses. Also described are FM stero systems including the above FM discriminator in its audio channels.

Abstract: There are provided a modulation circuit (9) and a signal processing circuit (2) on the same chip. The modulation circuit (9) modulates an input signal (30) to apply it to a selector (8). The selector (8) selectively applies to the signal processing circuit (2) either the input signal (30) or a modulated signal (40) in accordance with a select signal (50). The modulation circuit (9) is synchronized with the signal processing circuit (2) by a timing signal (11) from the signal processing circuit (2). For this reason, there is no need of an equipment for synchronizing the signal processing circuit (2) and the modulation circuit (9) in the test. A test signal provided from the exterior need not have been already modulated. Therefore, the test signal can be easily produced and confirmed, and the compression rate of the test signal is improved.

Abstract: A receiver having a signal path incorporating a tuner, a demodulator circuit for supplying a stereo multiplex signal having a baseband stereo sum signal (L+R), a 19 kHz stereo pilot and a stereo difference signal (L-R) which is double sideband amplitude-modulated on a suppressed 38 kHz subcarrier, a sampler for converting an analog signal into a time-discrete signal and a stereo decoder for time-division multiplex decoding of a time-discrete stereo multiplex signal into time-discrete left and right stereo signals. In order to realize an effective selection of the stereo multiplex signal by an easily integrable low-pass filter, the stereo decoder includes a time-discrete halfband low-pass filter circuit having a finite impulse response, with a transition band which is substantially located in the frequency range of said modulated stereo difference signal and with a half-value transfer which is located at the frequency of said 38 kHz stereo subcarrier.

Abstract: A noise suppressing circuit has a gate for controlling a composite signal applied to a stereo demodulator of an FM tuner, and a detector for detecting a noise included in the composite signal and for producing a noise dependent signal for controlling the gate to close it. A pilot signal detector is provided for detecting a pilot signal included in the composite signal for producing a pilot dependent pulses. In response to the noise dependent signal and to the pilot dependent pulses, gate control pulses are applied to the gate, thereby closing the gate in synchronism with the pilot signal.

Abstract: Generally, and in one form of the invention, a composite signal decoder (60) is disclosed which does not require synchronizing the sampling rate to the phase of the incoming pilot signal. Curve fitting filter (126) up-samples and interpolates the incoming composite signal (A) using a bank of coefficient filters selected from filter coefficient bank storage (122) by Bank Selector (124). Bank selector (124) operates in response to a phase offset value produced by phase calculator (112). Because curve fitting filter (126) need not be synchronous with the incoming pilot signal, the output sample rate can be asynchronous from the input sample rate. Other devices, systems and methods are also disclosed.

Abstract: In stereo receivers with digital decoding pulse generation, interference by the harmonics of the digital switching signal with signals in adjacent channels or with carrier signals in the sideband lead to faults that can be perceived in the audible range as chirping. An integrated stereo decoder with digital decoding pulse generation is described in which the low-harmonic, step-like switching signal consecutively assumes within a period and relative to the amplitude the values (1+.sqroot.2).sup.-1, 1, (1+.sqroot.2).sup.-1, -(1+.sqroot.2).sup.-1, -1, -(1+.sqroot.2).sup.-1, with the .+-.(1+.sqroot.2).sup.-1 values each persisting for an eighth of the period and the .+-.1 values a quarter of the period. Furthermore, an integrated circuit array for generation of this low-harmonic oscillation is described.

Abstract: An FM stereo receiving device according to the present invention has an object to be able to demodulate a stereo signal in a state close to a monaural reception, in which a pilot signal is extracted from an FM-demodulated output; a subcarrier signal is formed, based on this pilot signal; IF signals are switched intermittently by this subcarrier signal; and intermittent IF signals are IF-detected to obtain intermittent signals of base-band signals.These intermittent signals are switched by means of two switches, based on a subcarrier signal. Low frequency components of each output audio signal are extracted to obtain left and right signals EL and ER through a de-emphasis circuit.Owing to this device, it is possible to enlarge a reception region for an FM stereo broadcast with a high sensitivity.

Abstract: A discrete parallel path modulation multiplexer for use in generating a composite baseband signal from separate left and right input signals. The composite baseband signal includes the sum of the left and right input signals and the product of the difference between the left and right input signals and a subcarrier. The composite baseband signal may also include a pilot subcarrier at one-half the frequency of the subcarrier. In one signal path, the multiplexer multiplies the right input signal by the function (1+sin (wt)) and in a second signal path the multiplexer multiplies the left input signal by the function (1-sin (wt)). The products are then combined to obtain the composite baseband signal. A pilot subcarrier may also be generated and included as part of the composite baseband signal.

Abstract: An improved AM-FM combined stereo receiver is provided having a single processor for removing, in the FM mode, arctangent distortion, and in the AM mode, to process the phase term from arctangent ##EQU1## to determine ##EQU2## Further, the radio includes a single discriminator circuit, wherein, in the FM mode, the discriminator tank circuit is used to convert frequency deviation to baseband audio, and in the AM mode, the discriminator tank circuit is used as the frequency-determining element for the voltage controlled oscillator (VCO), the VCO being used to translate the intermediate frequency (IF) signal to baseband.

Abstract: In an FM stereo receiving device according to the present invention, a received first FM-modulated wave is demodulated by means of an FM-demodulator, from the demodulated output of which a subcarrier signal is produced, further a monaural signal is extracted by means of an LPF, and the monaural signal is again FM-modulated by means of a voltage controlled oscillator to obtain a second FM-modulated wave. Then a difference frequency component wave is produced by a multiplication operator and an LPF, starting from the first FM-modulated wave and the second FM-modulated wave and the FM-modulated wave and the difference frequency component wave are switched over with the subcarrier signal by means of a switch circuit. In this way signals of a right ear side component and a left ear side component are obtained and a stereo signal is obtained by FM-demodulating both the signals by means of the FM-demodulator.

Abstract: A system which enables transmission of a standard composite stereo sound signal, made up of baseband, subcarrier band and pilot signals, from a first location to a second location while requiring only a relatively low bit rate for the transmission link. The standard composite stereo signal is synchronously sampled at a first location at rate F.sub.s twice the subcarrier frequency F.sub.c (four times the pilot frequency F.sub.p), and the sampled signal transmitted over the link along with appropriate synchronizing signals. At the second location, a signal processor separates the received signal into a first signal related to one stereo channel signal (e.g. R) and a second signal representative of the other stereo channel (e.g. L), determines the proper scale for the pilot signal, and regenerates the original standard composite stereo sound signal by combining the L-related and R-related signals with the pilot scale signals in appropriate proportions and with appropriate filtering.

Abstract: An audio detector circuit forms L+R and L-R audio signals from an intermediate frequency compatible quadrature amplitude modulated signal in the form (1+L+R)cos(fct+.phi.) where .phi. contains phase modulated L+R and L-R signals. An envelope detector generates an L+R audio signal and in-phase and quadrature phase detectors produce L+R and L-R audio signals, respectively. The difference between L+R outputs of the envelope and in-phase detectors are amplified to generate a cosine correction signal. Each detector includes a differential operational amplifier having an field effect feedback transistor coupled between each amplifier output and the corresponding input and an field effect transistor coupling the compatible quadrature amplitude modulated signal to the operational amplifier inputs.

Abstract: A method and circuit arrangement identifies the presence or absence of known frequencies in an input signal composed of a plurality of frequencies, whereby a frequency generator controlled by a reference frequency generates four switch signals having frequencies dependent upon the frequency to be identified and having a phase difference of 90.degree. and respectively one switch signal is mixed with the input signal in a respective mixer. The respective mixer products of two mixers are additively combined and are filtered through a respective filter for filtering AC components out, and the DC voltage component contained in the respective mixer product given the presence of the known frequency is evaluated with respect to the amplitude.

Abstract: A signal distinction circuit comprising a noise detector for detecting a noise included in a received signal; and a maintaining circuit for maintaining the condition of a signal outputted from a detector for detecting a discrimination signal according to a signal outputted from the noise detector so that since the noise detector and the maintaining circuit prevent the condition of a signal outputted from the distinction circuit from being changed when an inteference such as a multipath interference occuurs, an output corresponding to a received signal can be reliably obtained.

Abstract: A switched capacitor low pass filter is used to sample an FM stereo composite signal with non-overlapping clock signal to achieve phase or magnitude detection of the 19 kHz pilot without being adversely affected by the presence of information at or about 57 kHz.

Abstract: A switched capacitor pilot cancellation circuit included in an FM stereo decoder signal path which substantially eliminates the 19 kHz pilot from the FM composite by subtracting a reconstructed pilot frequency signal from the FM composite. The reconstructed pilot signal is obtained by applying the DC output voltage of a pilot magnitude detector to a switched capacitor network which is sampled by clock signals which convert the DC to 19 kHz.

Abstract: A digital receiver samples data from an amplitude modulated subcarrier at a rate less than twice the subcarrier's maximum frequency by sampling at known phase points. Sampling at known phase points is achieved by generating a sampling clock from a signal phase locked to and transmitted with the modulated data subcarrier.

Abstract: A PLL circuit comprises a variable frequency divider (7) for frequency-dividing a signal having a reference frequency f.sub.1 with a frequency dividing ratio n.sub.1 or n.sub.2, a fixed frequency divider (8) for further frequency-dividing an output of the variable frequency divider with a frequency dividing ratio n.sub.0, to generate a first output signal and a second output signal which is out of phase by 90.degree. from the first output signal, multiplier (10) for multiplying an input signal by the second output signal, a comparator (11) for comparing an output of the multiplier with a predetermined reference voltage, and a D-type flip-flop (12) receiving as a D input an output of the comparator and receiving as a clock input the first output signal, an output of the D-type flip-flop (12) being applied to the variable frequency divider (7). When the second output signal leads the input signal by 90.degree.