87 results about "Amplitude demodulation" patented technology

A parameter-free method to analyze sensor signals incorporates two or more of frequency demodulation, amplitude demodulation and phase demodulation of the raw signal data. The resulting signal is transformed to a frequency domain, and target fault characteristics from the demodulated signal are identified. The method is used to detect faults in bearings, gears and other mechanical components.

The present invention is directed an ultrasonic frequencies fault detecting apparatus. The present invention uses high frequency ultrasonic energy signals to analyze bearings and determine the presence of faults therein. The ultrasonic return signals are heterodyned (by amplitude demodulation) into the audio spectrum for purposes of audio detection. In addition, a FFT spectrum of the signal is displayed on a monitor for more accurate results. According to the present invention software is used to automatically analyze the FFT spectrum by comparing the current spectrum with stored spectrums of known bearing conditions as modified based on the rotary speed of the bearing and the number of balls. Once a defect in a bearing has been located in this manner using automated FFT analysis, an operator can then use a device, such as a calibrated lubricant dispenser, to effectuate maintenance and/or repair.

The invention discloses a laser radar system and a compound distance-measuring and speed-measuring method adopting sine-wave amplitude modulation and phase pulse code modulation of the same, relating to the laser radar system and the compound distance-measuring and speed-measuring method adopting the sine-wave amplitude modulation and phase pulse code modulation of the same. The laser radar system and the compound distance-measuring and speed-measuring method adopting the sine-wave amplitude modulation-phase pulse code modulation of the same are invented in order to solve the problem of mutual limitation of range resolution and distance measurement range of the laser radar of the conventional laser radar system distance measurement method. The laser radar system performs sine-wave amplitude and pulse code compound modulation on the light intensity of the light beams to form a signal waveform. The modulation way of the signals is the amplitude modulation way; the sequence is that a signal with a constant amplitude value is firstly subjected to the sine-wave amplitude modulation and then subjected to the pulse amplitude modulation, so that moving speed and moving distance of the target can be output; and as the Doppler frequency shift caused by the target movement is obtained through the sine-wave amplitude demodulation, the moving speed of the target is thereby obtained. The laser radar system and the compound distance-measuring and speed-measuring method adopting the sine-wave amplitude modulation and phase pulse code modulation of the same, disclosed by the invention, are suitable for the field of radar.

An wireless terminal includes a demodulating unit which comprises an FV (fading vector) estimating unit for receiving a CPICH spread/demodulated signal to output an FV signal with a reduced noise ratio; a phase synchronization unit for multiplying a PDSCH spread/demodulated signal with a complex conjugate of the FV signal to correct the phase offset of the PDSCH I and Q signals to send the resulting PDSCH I and Q signals to a multi-level QAM amplitude synchronization detection unit and to an amplitude demodulating unit; a first-quadrant transformation unit for collecting the second to fourth quadrant signals of the phase-synchronized PDSCH I and Q signals; and a threshold value detecting unit for calculating a multi-level QAM threshold value from the first quadrant signals and the FV signals to send the threshold signal to an amplitude demodulating unit. The amplitude demodulating unit effects amplitude demodulation to output multi-level QAM demodulated signals. The threshold value detecting unit previously assumes a plural number of probabilities as to which of the levels received data belongs to and, using a plural number of the data, raises the precision of the assumed data. The threshold value is estimated, using the frequencies and differences of the respective levels, from the assumed plural threshold values.

The invention relates to a method for sending and receiving a clock signal as well as an optical transmitter, an optical receiver and a system thereof. The sending method comprises superposing the following steps: a clock signal to be sent to an optical carrier by optical amplitude modulation to form a pilot tone modulated light carrier; superposing a service signal to be sent to the pilot tone modulated optical carrier by light amplitude modulation to form an optical modulation service signal; and sending the optical modulation service signal through a fiber link. The receiving method comprises the following steps: receiving an optical modulation service signal from a fiber link; outputting a mixed electrical signal including a service signal and a clock signal after photoelectric conversion and optical amplitude modulating are carried out to the received optical service-modulated signal; filtering the mixed electrical signal for separation to obtain the clock signal. The invention realizes receiving or unvarnished transmission of the clock signal without taking up other extra bandwidth or access resources of the optical transmission system, and greatly reduces network construction cost and maintenance cost, and is easy to realize.

An ultrasonic occupant detection and classification system transmits an ultrasonic signal and receives a composite signal containing interference created between the transmitted ultrasonic signal and a reflection of that signal from a moving occupant. A signal component of the received, composite signal is extracted by amplitude demodulation and bandpass filtered to derive a frequency characteristic that is compared to stored frequency data; and the derived and stored data are compared to identify frequencies characteristic of respiration and/or other movements characteristic of living beings.

A dielectric recording/reproducing apparatus is provided with: a probe for applying an electric field to a dielectric material; a return electrode for returning the high frequency electric field for data reproduction; an inductor placed between the probe and the return electrode; an oscillator which oscillates at a resonance frequency determined according to the inductor and a capacitance formed in the dielectric material just under the probe; a switch for switching circuit connections depending on whether data recording is performed and data reproducing is performed; a recording signal input device for converting data to be recorded to generate a recording signal; a direct current voltage generation device for generating a direct current bias voltage to be applied to the dielectric material; a frequency-amplitude demodulator for demodulating an oscillation signal of the oscillator having the frequency that is changed depending on the capacitance owned by the dielectric material just under the probe; and a signal detector for detecting data from the demodulated signal.

The invention discloses a self-adaptive closed-loop measuring system of a resonant accelerometer, the frequency control adopts a self-adaptive control phase-locked loop structure, and the control modeof a loop filter can be automatically selected according to the change of the external acceleration, the problems that in the prior art, circuit parameters are fixed, and self-adaptive adjustment cannot be achieved are solved, and the contradiction between the response speed and the steady-state phase difference of the phase-locked loop is effectively overcome, so that the measuring range, the scale factor linearity and the zero bias stability of the accelerometer are effectively improved. Meanwhile, the structure is simple, a complex algorithm is not needed, and the system has the advantagesof being simple, efficient and high in adaptability. A PI control unit adopts an incremental algorithm, the improvement of a traditional position type PI algorithm is achieved, a better control effect can be obtained, and the stability of the system is improved; an amplitude control module adopts an alternating current automatic gain control method, a simple and effective amplitude demodulation method is adopted in the module, hardware resources are saved, and the amplitude of the driving signals can be adjusted within a large range.

The invention relates to a digital demodulation method and a digital demodulation device for frequency modulation and amplitude modulation signals, and belongs to the technical field of electronic measurement. The digital demodulation measurement of the frequency modulation and amplitude modulation signals is realized in a virtual instrument way, local area model parameter values such as amplitude and frequency of a sinusoidal carrier signal sequence are obtained by utilizing a partial waveform of less than a waveform cycle, and a sinusoidal model of less than a waveform cycle is subjected to sliding fitting on an actually-measured curve waveform, so that the digital demodulation of the modulation signals is realized. In addition, the method and the device have the characteristics of high temporal resolution, high robustness, small demodulation distortion, absolute convergence, rapid demodulation and the like. The method and the device are high in temporal resolution and robustness, an algorithm is absolutely convergent, and tracing and calibration are facilitated.

The invention discloses a method for lowering the probability of detection dead zones in a phase sensitive optical time domain reflection system. The method comprises the steps that medium frequency signals are subjected to amplitude demodulation to obtain the distribution state of amplitudes of the medium frequency signals along with distances; the medium frequency signals at the present are divided into a plurality of intervals on a distance axis, the medium frequency signals with the maximum amplitude index as the center and with the same width as detection optical pulses are selected in each interval to be subjected to phase demodulation to obtain the estimation to all interval phases; the phases of the adjacent intervals are differenced to obtain the optical signal phase difference caused by optical path differences; meanwhile, the phases of the medium frequency signals at the corresponding positions in the previous moment are backtracked, and the phase differences of the adjacentintervals are gained; the phase differences of the current moment and the previous moment are subjected to differentiate operation, the variation of the phase differences of the adjacent intervals isobtained, and winding is released. According to the method, vibration signals can be reconstructed in a high-fidelity mode only by a common single-mode sensing optical fiber without changing a traditional phi-OTDR system structure, and the false alarm rate is obviously lowered.

The invention discloses a permanent magnet synchronous motor low-speed domain rotor position identification method, so as to solve the problems that the traditional pulse signal injection method usesmultiple filters, the hysteresis effects are superimposed, the dynamic performance of the system is reduced, and the position estimation error is increased. A new low-speed position sensorless controlstrategy is proposed. In particular, on the basis of injection of a high-frequency pulse square wave voltage signal to a two-phase stationary coordinate system, through a generalized second-order integrator (SOGI), current in a beta axis is subjected to signal separation and amplitude demodulation, two paths of orthogonal signals including rotor position information are obtained, and through heterodyne and a rotor position observer, the rotor position information is extracted, and no filter is used during the whole signal demodulation process. The dynamic performance of the control system andthe accuracy of the rotor position estimation are effectively improved.

A multilevel amplitude modulation device for generating, from digital data, a multilevel amplitude modulation signal having four or more signal levels and outputting the generated signal, including: an average level calculator that selects one of a plurality of preliminarily prepared different candidates for a code word building method such that average level of a symbol array, obtained by adding a symbol for a code word of digital data to be transmitted to one or more already outputted symbols included in a multilevel amplitude modulation signal already outputted, is most approximate to voltage center of the four or more signal levels, and outputs a selection signal indicating the selected method; a signal converter that forms a codeword of the digital data in accordance with the method indicated by the selection signal; and a multilevel modulator that generates a multilevel amplitude modulation signal using the codeword and outputs the generated signal.

The invention discloses a method for extracting characteristics of a mechanical state signal of an on-load tap changer, and relates to the field of measuring electrical variables. The method for extracting the characteristics of the mechanical state signal of the on-load tap changer comprises the steps that a vibration signal during on-load tap switching process is measured through an accelerationsensor; noise component in an original signal is removed by wavelet denoising; then an envelope line of time domain waveform of the vibration signal after noise reduction is calculated by a Hilbert amplitude demodulation method; an amplitude mutation method is used for dividing the envelope line of the vibration signal into a stationary section and a non-stationary section; then an empirical modedecomposition method is used for decomposing the non-stationary segment signal to extract the feature quantity, and the fast Fourier transform is used for decomposing the stationary section to extract the vibration characteristic quantity so as to establish a vibration feature database of the on-load tap changer. The method for the extracting characteristics of the mechanical state signal of theon-load tap changer can improve the accuracy of the vibration signal feature extraction of the on-load tap changer without increasing the calculation cost, and provides an effective method for realizing on-line monitoring and diagnosis of the mechanical state of the on-load tap changer.

The invention discloses a transient electric energy quality signal analysis method based on high-frequency harmonic compensation iteration EMD, and the method comprises the following steps: 1), preprocessing a raw transient electric energy quality signal; 2), constructing a high-frequency compensation signal; 3), extracting an IMF component of the transient electric energy quality signal; 4), locating the starting and ending moments of transient disturbance; 5), carrying out the component analysis of the transient electric energy quality signal. The method carries out the decomposition of the IMF component, employs the HT transformation and an amplitude demodulation method for the decomposition of transient amplitude, transient frequency and phase of the signal, can analyzes the transient electric energy quality signal in real time, carries out the locating of the starting and ending moments of transient disturbance, and analyzes the harmonic component in the signal. The method can effectively carry out the locating and analysis of the transient electric energy quality disturbance signal, and provides reference data for the treatment of the electric energy quality, so as to guarantee the stable operation of a power system.

In contactless communication in which a carrier wave transmitted from a first antenna of a host is received via a second antenna of a terminal and the carrier wave is amplitude-modulated on the terminal to transmit data to the host, a carrier wave detected from the first antenna is amplitude-demodulated to obtain a first demodulated output, and phase information included in the carrier wave detected from the first antenna is extracted and the extracted phase information is decoded to obtain a second demodulated output. Then, either of the first and second demodulated outputs is selected and output. Even when a null is caused by an antenna distance between a PCD and a PICC, demodulated data is reliably obtained by utilizing demodulation processing that uses phase information.

The invention provides a weak capacitance change measurement circuit, and particularly relates to the technical field of weak capacitance signal conversion and detection. The measurement circuit comprises a CV conversion circuit, an amplification circuit, an analog multiplier, a low-pass filter and a phase shift circuit, the CV conversion circuit converts the relative change rate of the capacitance value of a capacitance sensor into the amplitude change of a weak sinusoidal signal; the weak sinusoidal signal is amplified by an amplifying circuit; the amplitude of an output signal of the amplifying circuit is solved by an amplitude demodulation circuit consisting of the analog multiplier and the low-pass filter, and a direct-current useful signal in direct proportion to the relative changerate of the sensor capacitor is output through the low-pass filter; the phase shifter changes the phase difference between the reference signal of the amplitude demodulation circuit and the output signal of the amplification circuit, and the circuit sensitivity is improved.

The invention discloses a method for a hyperbolic tangent companding transform capable of decreasing the peak-to-average power ratio (PAPR) of an OFDM (orthogonal frequency division multiplexing) signal, mainly used for solving the problems of non-constant average power and high error rate in the prior art. The method comprises the following realization steps of: (1) performing a quadrature amplitude modulation on the data bit stream generated by an information source, performing a serial-to-parallel conversion then sampling; (2) performing an inverse fast Fourier transform (IFFT) on an over-sampling signal to obtain an original OFDM signal; (3) establishing a companding function based on a hyperbolic tangent function, performing a companding transform on the original OFDM signal, performing a parallel-to-serial conversion then transmitting the signal; (4) calculating the PAPR of a transmitting signal; (5) performing a serial-to-parallel conversion on a receiving signal, then performing a de-companding transform and a fast Fourier transform (FFT); (6) de-over-sampling a FFT signal to obtain an OFDM demodulation signal; and (7) performing a parallel-to-serial conversion and a quadrature amplitude demodulation on the OFDM demodulation signal, then counting an error rate. The method for a hyperbolic tangent companding transform capable of decreasing the PAPR of an OFDM signal disclosed by the invention can efficiently suppress the PAPR, remarkably decrease the error rate, and keep a constant average power; and the method can be widely applied to a new generation of broadband wireless OFDM communication system.

Antenna identification data is transferred over a regular channel that is normally used for transferring navigation signals. Modulation of the received signal is used for transferring the portable antenna parameter data. Antenna identifications and parameters are written into a portable antenna module. The antenna module is attached to a radio receiver. The antenna module and the receiver are powered up. The portable antenna module receives radio signals that are amplified in a low-noise amplifier. Then, a level of the output signal is discretely modulated in the amplitude modulator and the signal is transferred to the radio receiver. The discrete fluctuations of the level of the signal are determined in the amplitude demodulator. The fluctuation of the level of the signal carries the information about the identification parameters of the portable antenna module. An analog-to-digital conversion of the determine signal fluctuation is performed in an analog-to-digital converter. The converted digital signal is used for receiving data related to the type and parameters of the portable antenna module.

In a receiver, a synchronization circuit (MIX2, C1, R1, VCO) provides a set of oscillator signals (OSI, OSQ, OSX, OSY) that are synchronized with a carrier of an amplitude-modulated signal. The set of oscillator signals (OSI, OSQ, OSX, OSY) comprises a first amplitude-demodulation oscillator signal (OSX) and a second amplitude-demodulation oscillator signal (OSY) that differ in phase. A first amplitude-demodulation mixer (MIX3) mixes the first amplitude-demodulation oscillator signal (OSX) with the amplitude-modulated signal so as to obtain a first amplitude-demodulated signal (MO3). A second amplitude-demodulation mixer (MIX4) mixes the second amplitude-demodulation oscillator signal (OSY) with the amplitude-modulated signal so as to obtain a second amplitude-demodulated signal (MO4). A magnitude comparator (MDT1, MDT2, DDT) compares respective magnitudes (M+, M−) of the first amplitude-demodulated signal (MO3) and the second amplitude-demodulated signal. Accordingly, a phase-error detection signal (IPED) is obtained that varies as a function of a difference between the respective magnitudes (M+, M−) of the first amplitude-demodulated signal (MO3) and the second amplitude-demodulated signal (MO4).