61results about "Frequency demodulator arrangements" patented technology

A method is provided for communicating signals at a low power level in an electromagnetic interference (EMI) environment. A first device transmits a modulated signal having a first carrier frequency, including the encoded information via a hardwire transmission medium. In one aspect, the power level of the modulated signal can be adjusted to minimize power consumption or reduce the generation of EMI. The modulated signal may be in one of the following formats: frequency modulation (FM) or phase modulation (PM) to name a few examples. A second device including a logarithmic detector amplifier (LDA) demodulator circuit receives the signal, which may be mixed with EMI. The LDA demodulator circuit amplifies the modulated signal, without amplifying the EMI, to supply a demodulated baseband signal, which may be an n-ary digital signal, or an audio signal. A low-power, noise insensitive communication channel is also provided.

Disclosed herein is a direct conversion type signal processing semiconductor integrated circuit device capable of suppressing a DC voltage variation in the output of a variable gain amplifier upon the transition to a reception mode, reproducing stable receiving characteristics and improving receiving sensitivity. In the signal processing semiconductor integrated circuit device, voltage reference circuits for generating reference voltages for controlling or restricting currents for current sources for supplying operating currents for amplifiers constituting a reception-system circuit are boosted upon the transition from an idle mode or the like to the reception mode to allow the currents to flow into the constant-current sources of the amplifiers after the stabilization of the generated reference voltages.

A near field RF communicator has an antenna circuit (120) to receive a modulated radio frequency signal by inductive coupling and demodulation circuitry (130 or 131) to extract the modulation from a received modulated radio frequency signal inductively coupled to the antenna circuit. The demodulation circuitry has a virtual earth input comprising a current mirror. The demodulation circuitry may be formed by an amplifier (115 or 116) and a demodulator (114) coupled to an output of the amplifier. The amplifier may be a single input amplifier (116) coupled to an output of the antenna circuit or may be a differential amplifier (115) having first and second inputs to receive the modulated radio frequency signal from first and second outputs of the antenna circuit, with each amplifier input providing a virtual earth input.

A receiver includes a first oscillator supplying a reference frequency signal; a reference signal generator producing a first frequency conversion signal and a local calibration signal from the reference frequency signal; a first frequency converter responsive to the first frequency conversion signal to down-convert the received signal during normal receive operation and to down-convert the local calibration signal during calibration processing; a second frequency converter responsive to a second frequency conversion signal from a second oscillator to further down-convert the received signal and the local calibration signal; a demodulator that demodulates the received signal at a demodulation frequency; and a frequency error processor that determines a frequency error from the local calibration signal at the demodulation frequency, wherein the reference signal generator adjusts a frequency of the first frequency conversion signal used during normal receive operation in response to the frequency error to compensate for the frequency error.

An orthogonal cross-polarization interference compensating device for solving the problem tin which integration contents of an integration circuit are indefinite when a control loop is cut. An orthogonal cross-polarization interference compensator generates a compensation signal for compensating phase noise included in an own polarization signal. A demodulator compensates for orthogonal cross-polarization interference based on the compensation signal for the phase noise included in the own polarization signal. An error detector generates an error signal indicating phase difference between the own polarization signal compensated by the demodulator and a proper own polarization signal. A phase noise phase detector generates a differential signal indicating phase difference between the own polarization signal and other polarization signals based on the compensation signal and the error signal. An integration circuit integrates the differential signal and generates an integration signal. An infinite phase-shifter adjusts the compensation signal based on the integration signal. A control circuit determines whether or not orthogonal cross-polarization interference is present based on the compensation signal adjusted by the infinite phase-shifter, and adjusts the integration value indicated by the integration signal to be a predetermined value when there is no orthogonal cross-polarization interference.

A method and system of canceling radio frequency interference (RFI) sourced from a narrow-band radio frequency transmitter to interfere with the operation of a multi-carrier modulation system. The spectral components of the RFI can be represented as a Taylor series of 1/(m−1/2) where m is an integer and (m−1/2) is a normalized approximate distance between the frequency of interest and the center frequency of the RFI. The coefficients of the Taylor series are obtained by solving a set of linear equations using the Fourier output at several properly chosen frequencies where the RFI components dominate. The coefficients for the Taylor series are formulated as linear combinations of the FFT output at the chosen frequencies and are computed and stored beforehand. Simple multiplications and additions are needed for obtaining the Taylor series coefficients from the FFT output at the chosen frequencies. The coefficients of the Taylor series can be obtained for any frequency, and the spectral component of the RFI can be estimated and removed from the MCM signals.

A slot-based low Intermediate Frequency (‘IF’) radio receiver comprises an IF local oscillator for producing I and Q IF local oscillator signal components in phase quadrature, I and Q mixer channels for mixing the input signal with the I and Q IF local oscillator signal components to produce I and Q IF signal components. The IF local oscillator includes frequency alternation means for causing the IF local oscillator frequency to alternate a plurality of times during each frame between first and second values, one of which is greater and the other smaller than the desired carrier frequency of the input signal so as to reduce the effect of adjacent and alternate interferers. The phase of the baseband local oscillator is alternated in synchronism with the alternation of the IF local oscillator frequency.

A very low intermediate frequency (VLIF) receiver and a method of controlling a VLIF receiver. The method comprises estimating energy levels in first and second signals and detecting interference from a first adjacent channel interferer based upon a difference in energy in the first and second signals. The first signal comprising a first on-channel portion and an adjacent channel portion and the second signal comprises an intermediate frequency translation of the first on-channel portion. The energy levels are estimated for corresponding time instances and the adjacent channel interferer is of the adjacent channel portion. The VLIF receiver is then controlled based upon the detected interference.

A radio receiver includes a processing unit that may generate a respective phase value corresponding to each of a plurality of digital samples of a received complex frequency modulation (FM) signal. The receiver also includes an impulse unit that may detect whether a linear combination of a phase value of a current sample and a phase value of one or more previous samples will produce an impulse at an output of an FM demodulator. If the impulse unit detects that an impulse will be produced at the output, the impulse unit may replace the output of the FM discriminator with a predetermined value.

GPS navigation devices or GPS receivers can consume less power by using a temperature recorder circuit and/or a power manager in maintaining the accuracies of the GPS receiver time and reference frequency to improve battery life. A representative receiver includes a time reference device and the temperature recorder circuit that operate while the receiver hibernates. The time reference device generates clock signals and the temperature recorder circuit receives and operates using the clock signals from the time reference device. The temperature recorder senses the temperature of the time reference device. The temperature recorder circuit is designed to send a wake-up signal to at least one electrical component of the receiver to wake up the electrical component of the receiver. The electrical component of the receiver includes at least one of the following: a GPS signal processing system and a frequency reference device.

The invention relates to a system and a method for eliminating single-frequency interference and multifrequency interference, which comprises the following steps: acquiring an estimated frequency and an estimated gain of an interfering signal through low-precision time-frequency transformation; producing a reference interfering signal according to the estimated frequency and the estimated gain; based on a minimum relevance principle, calculating to obtain an error signal according to a received signal and the reference interfering signal; and based on an adaptive algorithm, updating the reference interfering signal according to the error signal. The method of the invention has the advantages of low computational complexity, high convergence speed and high tracking accuracy, and the like.

A signal compensation circuit compensates for direct-current offset of an input signal by amplifying the input signal with an amplifier having a variable direct-current offset. A low-speed negative feedback loop charges and discharges a capacitor in an integrating circuit according to the direct-current component of the amplified signal. A high-speed negative feedback loop charges and discharges the same capacitor at a faster rate when the amplified signal goes outside an allowable amplitude range. The capacitor potential is used to control the direct-current offset of the amplifier. The allowable amplitude range is adjusted according to the amplitude of the amplified signal. High-speed compensation can thus be combined with a tolerance for runs of identical code levels in the input signal.

A method separates a multi-component signal by first estimating parameters of the signal. Then, using periodicity-based algebraic separation and energy-based demodulation, the signal is separated into components according to the parameters and constraints. Last, a Teager-Kaiser energy detector is applied to each component to provide a direct current signal for each component, and the constraint for each component used by the separating.

The invention belongs to the technical field of communication, and particularly relates to a broadband band-pass filter system and method, and the system comprises: a sampling unit which is used for collecting an original signal; ta band-pass filtering unit which is used for extracting fundamental wave signals of the signals; a zero-phase filtering unit which is used for receiving the output signal of the first band-pass filtering unit and carrying out secondary filtering on the output signal; and a first control unit which is used for fitting the amplitude-frequency characteristic curve of the fundamental wave filtering unit to obtain the relationship between the amplitude gain and the frequency, and carrying out amplitude compensation. After an original signal is collected, the originalsignal is preprocessed, when band-pass filtering is carried out on the preprocessed signal, a fundamental wave signal of the preprocessed signal is more easily extracted, and then signal amplitude compensation is carried out on the extracted fundamental wave signal, so that the accuracy of the finally band-pass signal is higher, and meanwhile, the band-pass filtering efficiency is higher.

The disclosure relates to a radio receiver and an intermediate frequency signal generation method, and specifically relates to an IF filter that band-limits an intermediate frequency signal outputtedfrom a mixer. An AFC unit controls the oscillation frequency of a PLL so that the frequency of the intermediate frequency signal is a predetermined frequency. When the AFC unit controls the oscillation frequency of the PLL, a band control unit controls the passing characteristic of the IF filter to the passing characteristic of a wide band, and after the completion of the control, controls the passing characteristic of the IF filter to the passing characteristic of a narrow band. A frequency correction unit refers to a filter information storage unit, and corrects the oscillation frequency controlled by the AFC unit according to the difference between the center frequency of the passband of the passing characteristic of the wide band and the center frequency of the passband of the passingcharacteristic of the narrow band.

The invention relates to a method for the frequency error correction of an oscillator of a sensor node in a sensor network, comprising the following steps: receiving a transmission signal of a transmitter, the signal being modulated by orthogonal frequency division multiplexing (OFDM); determining the frequency deviation of the oscillator using the received transmission signal; and determining a correction signal for correcting the frequency deviation of the oscillator and correcting the frequency of the oscillator by means of the correction signal.

The invention discloses a common-mode transient interference suppression circuit and an isolator. The common-mode transient interference suppression circuit comprises a first-stage high-pass filter, a second-stage high-pass filter, a signal demodulation circuit and a common-mode detection circuit, wherein the first-stage high-pass filter, the second-stage high-pass filter and the signal demodulation circuit are connected in series; the common-mode detection circuit is arranged between the first-stage high-pass filter and the second-stage high-pass filter; the first-stage high-pass filter and the second-stage high-pass filter are used for sequentially filtering the input signal of the signal receiving end, outputting a differential signal and providing a current discharge channel when common-mode transient interference occurs; the common-mode detection circuit is used for detecting the differential signal, generating a common-mode transient detection result signal and outputting the common-mode transient detection result signal to the signal demodulation circuit; and the signal demodulation circuit is used for demodulating the differential signal according to the common-mode transient detection result signal to obtain an original signal. According to the scheme, signal decoding abnormity caused by common-mode transient interference can be effectively suppressed, and the common-mode transient interference resistance of the isolator is improved.