364 results about "Digital demodulation" patented technology

An apparatus, system, and method, for determining the total frequency response of a communication system, include one or more testers each having a tuner, digital demodulation circuitry, and a controller that measures an absolute power level at the tester location for a particular channel and that measures a relative frequency response for the channel based on the tap weight coefficients from the digital demodulation circuitry. The absolute and relative measurements are combined and then recorded by each tester. The combined values of two or more testers are compared to determine the total frequency response of the communication system. The relative response measurements are converted from time domain to frequency domain by fast Fourier transformation. The controllers maintain a channel plan for sequencing the sweeping of consecutive channels.

A multi-standard single-chip receiver for digital demodulation of TV signals broadcasted over any of multiple digital television means, e.g., satellite, cable and terrestrial, is provided. The receiver can receive and demodulate a variety of different signal types received from one or more up-front tuners. A demodulator architecture in accordance with an embodiment of the present invention can be optimized to re-use common demodulation processing blocks for the different incoming signal types.

The invention discloses an indoor visible light positioning system. The indoor positioning technology is completed jointly by combination of an LED lamp, a hand-held receiving terminal, and a positioning algorithm. Position information is modulated on a carrier wave distributed to the LED lamp and reverse fast Fourier transform is carried out; a signal is sent into a drive circuit and then the signal is transmitted to an air channel in a visible light mode by free space. A receiving terminal carries out light convergence by an optical lens; the signal is converted into an electric signal; fast Fourier transform is carried out and digital demodulation is carried out; and according to information of three detected strongest powers, a distance between the receiving terminal and the LED lamp is estimated by a lambertian model. According to position coordinate information of a carried transmitting terminal and estimated distance information, a receiving coordinate is calculated finally and positioning is carried out. According to the invention, communication reliability is enhanced; the positioning precision is improved; and the interference of communication between LED cells is effectively resisted.

The invention discloses an onboard automatic speed measuring and height measuring radar system and a speed measuring and height measuring method. The system comprises an antenna, a transmitter, a superhet receiver, a broadband digital intermediate-frequency receiver, a center computer and a power module. The transmitter generates four sawtooth wave linear frequency modulation radio-frequency signals and achieves space symmetric configuration through the antenna; the superhet receiver and the broadband digital intermediate-frequency receiver complete echo signal digital demodulation together and calculate the frequency, amplitude, phase and signal-to-noise ratio information of echo signals; the center computer separates the speed information and the height information of the same echo beam by applying Doppler principle directivity based on the space symmetry and the timing sequence relevance of four beams, and the information is used for calculating the flight speed value and the flight height value of an aircraft. According to the onboard automatic speed measuring and height measuring radar system and the speed measuring and height measuring method, the same radar can be used for automatically measuring the speed and the height, the structure of an aircraft avionics system is simplified, the measuring precision is high, and the onboard automatic speed measuring and height measuring radar system and the speed measuring and height measuring method can be used for measuring carrier aircraft flight parameters.

The invention discloses a method for realizing a high anti-interference unmanned aerial vehicle remote control data link, which comprises two steps of data transmitting and data receiving, wherein the data transmitting comprises the steps of performing serial-parallel conversion, performing M-ary spread spectrum on parallel N-channel binary baseband information to obtain N-channel M-ary spread spectrum information, performing digital modulation, controlling a frequency hopping source to generate frequency hopping carriers by frequency hopping sequences and performing data sending; and the data receiving comprises the steps of receiving transmitted signals for bandpass filtering, synchronizing the system and dehopping, performing M-ary despreading, performing digital demodulation and performing serial-parallel conversion. The method adopts multi-channel M-ary spread frequency technology, and has higher information transmission efficiency compared with single-channel M-ary spread spectrum with high information transmission; the method adopts multi-channel M-ary spread spectrum, and each channel adopts frequency hopping sequences with different lengths and different code rules so that each channel has higher anti-interference ability; and the method adopts the combination of spread spectrum technology and frequency hopping technology, has the ability of resisting narrow-band interference and near-far effect of a frequency hopping communication mode, and meets the requirement of high interference resistance.

A digital receiver for processing a signal received from a channel includes a digital demodulator and an equalizer coupled to the digital demodulator. The equalizer includes a feedforward filter and a decision feedback equalizer (DFE), wherein the feedforward filter includes a plurality of feedforward filter taps. Coefficients are associated with the plurality of feedforward filter taps and the values of all of the coefficients associated with the plurality of feedforward filter taps are dynamically determined.

The invention relates to a voice signal quantum encryption communication system based on a random number, which comprises terminal equipment, a quantum communication access point, a quantum communication gateway and a quantum communication access point, wherein the terminal equipment consists of a terminal sending subsystem and a terminal receiving subsystem; the terminal sending subsystem comprises a quantum key agreement and management module, a voice signal encoding module, a random number generation module, a voice encryption module and a digital modulation module; and the terminal receiving subsystem comprises a voice signal decoding module, a quantum key agreement and management module, a voice decryption module and a digital demodulation module. One piece of terminal equipment simultaneously comprises the terminal sending subsystem and the terminal receiving subsystem. According to the invention, the terminal sending subsystem is applied to send a voice signal with good encryption performance and high anti-interference performance and meanwhile, the terminal receiving subsystem is utilized to receive and reduce the voice signal, so that safety and integrity in the communication process are ensured.

The invention discloses a novel high-precision data acquisition system for electrical impedance imaging. The system is constructed by a main control module, a programmable current source, an electrode interface module, a voltage measurement module, a current detection module, a digital demodulation module, a communication interface module and the like. Excitation currents in an imaging target region are accurately controlled through the current detection module and the programmable current source, distribution differences are effectively suppressed through an electrode selection switch system in the electrode interface module, external disturbance is effectively blocked through an electrode wire double-shielding system in the electrode interface module, and related demodulation of response signals and excitation signals is achieved through the digital demodulation module. By the adoption of the high-precision data acquisition system, the influence of distribution parameters and external disturbance in the data acquisition system for electrical impedance imaging can be effectively suppressed, nonlinear errors of a measurement result are reduced, the signal to noise ratio of measured data is increased, the key problem that in the electrical impedance imaging research, data acquisition accuracy is difficultly further improved is solved, and the high-precision data acquisition system has important application value.

The invention discloses a novel digital demodulation identification method based on generalized fractional fourier transform (GFRFT) and fractional lower Wigner-Ville distribution (FLOWVD). The novel digital demodulation identification method comprises the steps as follows: received signals are sampled firstly, and then complex envelopes of the signals are restored through Hilbert transform; the maximum value of zero center normalization instantaneous amplitude spectrum density for the signals based on the GFRFT is calculated; the maximum value of the FLOWVD amplitude for the signals is calculated and is taken as characteristic quantity; and in addition, a sorter based on a decision tree is adopted, and the signals adopting different demodulation manners can be identified through data processing, threshold setting and comparison decision. Under the non-gaussian Alpha stable distribution noise, the novel digital demodulation identification method achieves the performance that remarkably surpasses the traditional method, and also achieves higher identification rate and favorable robustness.

The invention discloses a blood oxygen saturation measuring device and a measuring method. The measuring device is characterized in that a microprocessor outputs square waves at different frequencies and in twice rate relationship, the square waves drive at least two kinds of light emitting diodes, light emitted by the light emitting diodes is received by a photosensor after passing through a finger to be measured, the light is converted into voltage signals by the photosensor, the voltage signals are converted into preset amplitude voltage signals through a current / voltage conversation amplifier, an analog to digital converter converts the preset amplitude voltage signals into digital signals, the microprocessor processes the digital signals, and the blood oxygen saturation is obtained. The measuring method comprises the steps that: the microprocessor carries out separation processing on the digital signals, photoelectric volume pulse waves are obtained, and the background light interference is eliminated; a valley value and a peak value are obtained according to the photoelectric volume pulse waves; the valley value and the peak value are calculated to obtain a Q value; and the blood oxygen saturation is calculated through the Q value, and the blood oxygen saturation is obtained. Square wave frequency division modulation and digital demodulation are adopted, and the blood oxygen saturation measuring device and the measuring method have the characteristics that the measurement is accurate, the circuit is simple, and the cost is low.

The invention relates to a digital transmission demodulating method of a differential transformer displacement transducer, belonging to a method for processing signals for accurately measuring the small displacement of an object by using an LVDT (Linear Variable Differential Transformer). The method comprises the following steps of: driving a primary coil of the LVDT by a transformer manufactured by a field programmable gate array (FPGA), collecting the output signals Va and Vb of two secondary coils of the LVDT, carrying out digital demodulation on the collected output signals Va and Vb of the two secondary coils of the LVDT in the formula of S=(Va-Vb) / (Va+Vb), and detecting signals of the LVDT by the mapping relationship between the actual displacement of the LVDT iron core and the S. The addition and subtraction as well as the demodulation method of the division are used on the secondary coil signals in the LVDT, and the actual displacement of the LVDT iron core is obtained by a moving average algorithm and the mapping relationship. The invention reduces the noise interference to the measuring result and greatly reduces the measuring error.

A digital PWM demodulator includes a first set of delay cells to receive a PWM signal and to propagate the PWM signal in a forward direction for a first interval. Delayed signals obtained at the end of the first interval are propagated in the reverse direction through the delay cells for a second interval. A logic zero feeds into the last cell at the start of the second interval. The output of a last cell in the delay cells at the end of the second interval is indicative of a data value modulated on the PWM signal. The digital PWM demodulator includes a second set of delay cells designed to operate identical to the first set of delay cells. The first set of delay cells and the second set of delay cells in conjunction with additional digital circuitry demodulate alternate periods of the PWM signal.

The invention provides a low-power MSK non-coherent digital demodulating method by adopting the phase axis detection and a demodulator which consists of a phase axis generator, a quantizer, a phase detector, a judgment former, correlator groups, a sign judgment device and a clock selection circuit; wherein, the demodulator does not need an independent carrier frequency and a phase restoration circuit or a data restoration clock circuit; DSSS signals can directly de-spread by adopting the correlator groups without a clock and bit restoration circuit; the algorithm of the slopes of phase changes of base-band signals of PN code sequence is adopted in relative judgments, which can overcome the phase cumulative errors caused by the random clock skew of a sending terminal; in addition, the demodulator has a better compensation ability for frequency errors without special frequency compensation circuits; furthermore, the demodulating performance is unrelated with carrier phases and the synchronization performance of DSSS frequency spread and frames and signs is good. The MSK demodulator is characterized by simple demodulating method, low packet loss rate, few hardware expenses, strong anti-noise ability, low power, easy integration, and the like, and can be applied to modern high-end communication terminals.

The invention provided a paving type conformal array sonar device based on interference optical fiber hydrophone, comprising a laser source array, an interference optical fiber hydrophone time division multiplexing array, a wave-divided mixer, a dense wavelength division demultiplexer, a phase generation carrier wave demodulator and a data generator, wherein the laser source array transmits laser beam pulses of different wavelengths to be input into the interference optical fiber hydrophone time division multiplexing array; the interference optical fiber hydrophone time division multiplexing array modulates the laser beam pulses according to underwater acoustic signals to generate interference laser beam pulses; the wave-divided mixer processes wave-divided mixing on all interference laser beam pulses; the dense wavelength division demultiplexer demultiplexes and separtes the mixed interference laser beam pulses into a plurality of interference laser beam pulse groups of single wavelength; the phase generation carrier wave demodulation processes phase detection, photoelectric conversion and digital demodulation on the interference laser beam pulses; and the data generator generates multi-path sonar digital signals of conformal array according to the digital demodulation result.

The invention provides a phase generator carrier (PGC) digital demodulation method for an interferometric fiber optic sensor and a device thereof. The PGC digital demodulation method for the interferometric fiber optic sensor comprises the following steps: outputting interference light intensity signals including sensing signals phi(t), and carrier signals by adopting the PGC technique; performing discrete sampling on the interference light intensity signals in the whole observation time T to obtain time domain sequence signals of the interference light intensity signals; by taking a carrier fundamental frequency cycle Tc as a unit, dividing the T into a plurality of time slots, and performing discrete Fourier transformation (DFT) on the time domain sequence signals in all the slots Tc to obtain the frequency spectrums of the time domain sequence signals; performing inverse discrete Fourier transformation (IDFT) on the frequency spectrums to reconstruct corresponding time domain signals; and according to the relation between the harmonic amplitudes of the reconstructed signals and the harmonic amplitudes of continuous signals, calculating the in-phase components cosphi(t) and the quadrature components sinphi(t) of the sensing signals phi(t) in all carrier cycles Tc, and performing the calculation slot by slot until the cosphi(t), sinphi(t) and the sensing signals phi(t) in the whole observation time T are obtained, and signal PGC demodulation is realized by the digital technology. A mixing system is not adopted, a local oscillation signal is not needed, and the problems, such as carrier signal synchronization and the like do not exist, and the overall performance is better.

An apparatus and method for passive radio frequency identification (RFID) reader digital demodulation with respect to a Manchester subcarrier signal are disclosed. In a passive RFID environment where the Manchester subcarrier signal contains DC components in a frequency region, even when a tag signal containing the DC offset noise is input to a baseband, demodulation may be efficiently performed while the DC offset noise is removed. Therefore, accurate detection of tag information from the tag signal may be achieved.

A method and apparatus for digital demodulation for use in a wireless communication device include processing that begins by performing a fast Fourier transform to convert a plurality of time domain symbol components representing inbound data into a plurality of frequency domain symbol components. The processing continues by frequency domain equalizing at least some of the plurality of frequency domain symbol components based on a dynamic compensation control signal to dynamically compensate for adverse transmission characteristics of the plurality of time domain symbol components. The processing then continues by generating a plurality of estimated symbols and a plurality of error values for the plurality of compensated frequency domain symbol components. The processing then continues by generating the dynamic compensation control signal based on at least one of the plurality of error values, the plurality of frequency domain symbol components and the plurality of compensated frequency domain symbol components.

A dual mode radio communication apparatus according to the invention has a reception speech signal output circuit for processing an analog demodulation signal in an analog mode and a digital demodulation signal in a digital mode by means of a common signal processing circuit, thereby outputting reception speech signals, respectively. In the dual mode radio communication apparatus, a level variable circuit is provided across a signal path extending between a demodulated signal input terminal of a reception speech signal output circuit and a speaker. The level variable circuit determines whether the analog mode or the digital mode is set as the radio communication mode. If the analog mode is set, the gain of the level variable circuit is set to a first value for compensating for a level deviation in the analog demodulation signal. If the digital mode is set, the gain of the level variable circuit is set to a second value for preventing excessive suppression of the digital demodulation signal.

A digital demodulator that may be utilized in integrated radio receivers and / or integrated radios includes a mixing section, 1st and 2nd digital comb filters, phase locked loop module, and a data recovery module. The mixing section is operably coupled to produce a digital I signal and a digital Q signal from a digital intermediate frequency signal. The 1st comb filter filters the digital I signal while the 2nd comb filter filters the digital Q signal. The phase locked loop module produces a digital signal from the filtered I and filtered Q signals. The data recovery module interprets the digital signal to recapture a data stream.

A VSB demodulating device and method in a DTV receiver is disclosed, in which a VSB signal is received for independent carrier wave recovery and symbol clock recovery. An A / D converter samples the output of a SAW filter with a fixed frequency and converts the resultant value to a digital signal. A carrier wave recovery portion recovers a carrier wave from a base band pilot signal output from a multiplier, and a timing recovery portion recovers a symbol clock used for a transmitter using the output of a matched filter disposed in a base band. In this case, the carrier wave recovery portion and the timing recovery portion are independently operated without affecting each other. Thus, the carrier wave recovery portion is operated stably even in case where a fatal ghost exists in a band used for timing recovery. Furthermore, since a closed loop control can be implemented independently for carrier wave recovery and timing recovery, stability of the system is improved, thereby improving performance of the DTV receiver.

The invention discloses a phase demodulation device and demodulation method capable of suppressing light-intensity fluctuation noise. The phase demodulation device comprises a fiber interferometer and a digital demodulation device. According to the device and method, an improvement is carried out on a conventional phase generation carrier algorithm; multiplying operation is carried out on a fundamental frequency component and a frequency doubling component of a tested phase, and meanwhile, multiplying operation is carried out on the differential value of the fundamental frequency component and the differential value of the frequency doubling component; then, division operation is carried out on the two products above to remove noise caused by light-intensity fluctuation; and the tested phase is calculated through an integration method. Meanwhile, a noise reduction demodulation algorithm is integrated in FPGA and DSP large-scale high-speed signal processors; and according to the characteristics of high parallel processing capability of an FPGA and excellent floating-point calculation performance of a DSP, differential and corresponding phase calculation are partially realized in the two processors respectively, thereby ensuring real-time performance. The phase demodulation device and method suppress the light-intensity fluctuation noise effectively, improve long-term stability and can be widely applied to the fields of high-precision fiber measurement and fiber sensing and the like.

The invention relates to a digital demodulation device, in particular to a continuous-phase frequency-shift keying digital demodulation device and a demodulation method implemented by the same. The continuous-phase frequency-shift keying digital demodulation device comprises a comparator device and a field-programmable gate array device. An internal circuit of the field-programmable gate array device comprises a clock unit, a sampling unit, a counting unit, a buffer unit and a reconstruction unit, and the clock unit is connected with the sampling unit, the counting unit, the buffer unit and the reconstruction unit; the comparator device is connected with the sampling unit; the sampling unit is connected with the counting unit; the counting unit is connected with the buffer unit; the buffer unit is connected with the reconstruction unit. The continuous-phase frequency-shift keying digital demodulation device and the demodulation method have the advantages that the demodulation device has the simple circuit and is easy to implement, low in programmable logic resource consumption and high in signal adaptability; the demodulation method can replace the traditional continuous-phase frequency-shift keying digital demodulation method, so that shortcomings of complexity in implementation, high resource consumption and inadaptability to proximity of data rates and carrier frequencies can be overcome, and the like.

The invention provides a high-speed-digital-demodulation-based power control system and method of a vector network analyzer. On the basis of the digital demodulation and processing way, nearly all digital filters with any random bandwidths can be designed by using a digital signal processing technology, thereby improving the signal to noise ratio of demodulation and achieving an objective of enlarging a power scanning range. The digital demodulation link of the vector network analyzer has high linearity, so that the power control accuracy is improved. With the power control method for digital demodulation and processing, the designs of circuits of microwave detector and a log amplifier and the like are not needed, thereby simplifying the loop hardware design. Because demodulation is carried out on the intermediate frequency without limitation of a signal source frequency range, the same set of amplitude stabilization system can be applied to power control of the vector network analyzer in different power ranges as long as the intermediate frequency is not changed.

The invention provides a parallel interpolation bit synchronization system in all-digital demodulation and a synchronized method thereof. The method comprises the following steps: (1) delaying two paths of input parallel sampling data K1 and K2 respectively for three clock cycles, and obtaining K1_d1, K1_d2, K1_d3 and K2_d1, K2_d2 and K2_d3; (2) respectively carrying out interpolation processing to the above sampling data and uk; (3) delaying indicating effective signals to the time when the above interpolation processing obtains results, carrying out extraction to the interpolation processing results in the step (2) according to the indicating effective signals, obtaining maximum points of symbols and traversing points of symbols and outputting the maximum points of the symbols; (4) calculating timing errors according to the maximum points of symbols and traversing points of symbols obtained in the step (3), carrying out noise filtration on the timing errors and obtaining NCO control signals after adjusting amplitude processing; and (5) determining the interval uk of the indicating effective signals and the maximum points of symbols with the former sampling point, entering next clock cycle and starting execution from the step (1).

A method for processing data obtained from a condition monitoring system, the method including steps of (a) obtaining an Acoustic Emission time waveform from at least one sensor and (b) digitally demodulating the Acoustic Emission time waveform.

The invention provides a simulation method for the digital closed-loop control logic of a fiber-optic gyroscope. The simulation method comprises the following steps: establishing a model and simulating according to the model, wherein a fiber-optic gyroscope closed-loop control logic model comprises a digital demodulation model and a digital controller model, and a closed-loop control logic simulation fiber-optic gyroscope model comprises a Sagnac effect model, a deviation modulation model, a step modulation model and phase modulation model; determining parameters needed by simulation, wherein the parameters comprise a system loop closing cycle, a modulation square wave frequency f, a square wave half-cycle sampling point number and a magnification factor; adjusting the magnification factor of a pre-amplifier module and the magnification factor of a post-amplifier module to realize normal loop closing of the fiber-optic gyroscope model in a simulation process; determining whether the output scale factor of the fiber-optic gyroscope is consistent with a required index or not through the waveform and numerical value of an output signal. By adopting the simulation method, designers do not need to perform detailed coding writing and can put more effort into system design and analysis; the project period can be shortened, the working efficiency is increased, and the product cost is reduced.

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 embodiment of the invention discloses a digital modulation method. The method comprises: coding processing is carried out on original data to obtain a bit sequence; the bit sequence is divided into M to-be-modulated bit groups, wherein each to-be-modulated bit group includes N bits; according to a preset constellation map, constellation mapping is carried out on the M to-be-modulated bit groups to obtain M constellation points; phases of the M constellation points are obtained, wherein the phases of the M constellation points include: phi1, phi2, ..., phiM; the phases of the M constellation points I are adjusted; to be specific, the phi1 is adjusted to be phi0+phi1, the phi2 is adjusted to be phi0+phi1+phi2, ..., and the phiM is adjusted to be phi0+phi1+phi2+phi3+...+phiM, wherein the phi0 is 0 or the phi0 is the phase of a previous symbol before the constellation point with the phase of phi1; and the M constellation points after phase adjustment are modulated to obtain an N-order modulation signal. In addition, the embodiment of the invention also discloses a digital demodulation method and apparatus, and a system. Therefore, the phase noise interference can be reduced.

The invention provides an all-digital demodulation method based on an open loop structure. The receiver firstly filters out-of-band noise of an obtained digital baseband signal through a matching filter, detects a burst signal on the basis of a double-sliding-window algorithm; an O & M algorithm is adopted to complete timing error estimation of the burst signal, controls a cubic interpolation filter to carry out interpolation operation on the obtained sample value through a timing error; and performs cross-correlation operation on the signal after timing synchronization and a local synchronization code element to complete frame synchronization and eliminate a frequency offset error, and finally, removes phase offset through a phase offset estimation algorithm based on a maximum likelihoodcriterion to complete stripping of a carrier, thereby obtaining a recovered baseband signal. The sampling rate is reduced, and the calculation complexity is reduced. The method is simple, the demodulation effect is good, the noise tolerance is high, and the reliability and efficiency of burst signal demodulation are improved.