360 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 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 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.

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.

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 digital demodulator that may be utilized in integrated radio receivers and/or integrated radios includes a mixing section, 1^st and 2^nd 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 1^st comb filter filters the digital I signal while the 2^nd 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.

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.

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.

The invention relates to a tamed spread spectrum multiplexing method for high-speed data transmission. The method is characterized by comprising a transmitting step and a receiving step, wherein the transmitting step comprises the following steps of: converting 2n-bit serial data to be transmitted into two paths of parallel data, performing multi-nary data spectrum spread, acquiring a baseband signal, performing D/A (Digital/Analog) conversion to acquire an analog baseband signal, and transmitting through quadrature modulation; and the receiving step comprises the following steps of: converting a high-frequency signal received by an antenna into an intermediate-frequency signal, then converting the intermediate-frequency signal into a digital intermediate-frequency signal, and converting the digital intermediate-frequency signal into serial data through digital demodulation, synchronous signal de-spread and parallel-series conversion. The tamed spread spectrum multiplexing method for the high-speed data transmission is an effective technical means for solving the contradiction between the communication rate and the signal bandwidth of spread spectrum communication, so that the shading property, the reliability and the anti-interference performance of high-speed data communication equipment are improved.

The present invention relates to a system and method for digitally demodulating FM signals in a digital wireless walkie-talkie system. In order to be compatible with the problem of analog FM demodulation in a digital mobile walkie-talkie system, in the present invention, the data sampling module first The input analog FM signal is sampled, and then the carrier removal module performs carrier removal processing on the data to be demodulated, and then the baseband analysis module analyzes the IQ two-way carrier signal to restore the modulated signal, and finally the low The pass filter module performs low pass filter to output the demodulation result signal. The clock module, carrier removal module, baseband analysis module, and low-pass filter module in the system can be realized by one FPGA. The invention realizes the compatibility of the analog FM demodulation in the digital mobile walkie-talkie system, realizes the digital processing of the analog signal, thereby achieving the purpose of enhancing the anti-interference ability of the signal and the like.