392results about How to "Downsampling" patented technology

The invention discloses a co-channel full-duplex system based on MPPSK modulation. After the system isolates receiving and sending signals at the radio-frequency head normally, cancellation conducted on leakage self-interference signals is finished on a digital baseband; the cancellation method is conducted after conducting shock filter on MPPSK receiving and sending aliasing signals, extracting and multiplying by coherent carrier, band-pass filtering and digitizing, the result of initial channels of all self-interference channels between the output end of a modulator and a receiver ADC is estimated before formal communication, self-interference offset signals are rebuilt by the adoption of the estimated result, further residual errors are filtered out with the combination of methods of coding rate filtering and double matched filtering of a method of shock filtering-multiplying by the coherent carrier-band-pass filtering-coherent demodulation, and MPPSK receiving signals are demodulated reliably. The co-channel full-duplex system based on MPPSK modulation is free of radio-frequency self-interference cancellation, has low requirements for the dynamic range and sampling rate of the ADC, has high isolation degree for the self-interference signals, and is simple in structure, low in complexity, high in spectrum efficiency and good in demodulation performance.

The invention provides a method based on linear programming for locating near-field targets and a system thereof, particularly a method for locating near-field targets on the basis of the compressivesensing theory. The method comprises the following steps: selecting a reference array element under the condition that the signal form is unknown, allowing the reference array element to work at the normal sampling frequency, and the other array elements to work at far below the Nyquist sampling frequency; taking the output signal of the reference array element as the reference target signal, to acquire the sample data of all the array elements; generating a time-delay table and a sparse basis array; generating a random mapping array and obtaining a coefficient array; obtaining a sparse vectorby linear programming solution; and acquiring the location information of the near-field target from the predetermined location-distance collection on the basis of the acquired estimation results ofthe sparse vector. According to the invention, the sensor does not need to work beyond the Nyquist sampling frequency, thereby greatly reducing the sampling rate, reducing the operating energy consumption of the sensor and improving the resource utilization rate of the system; and the method has no limits to the target bandwidth, so that the method is applicable to the target location of both narrowband and wideband, and the method is further applicable to non-Gaussian target location.

The invention provides a simulation method for a linear frequency modulation continuous wave synthetic aperture radar video signal, which comprises the following steps: simulated synthetic aperture radar system parameter information is set and read; the information parameter of a target is set; a simulated time is treated with discretization; the instantaneous positions of a radar platform and the target are respectively calculated, and a distance vector between a phase center and the target is obtained according to geometric position relation; a one-dimension echo signal is obtained by combining the echo signal mathematic model of the synthetic aperture radar and radar system parameters; the one-dimension signal is divided according to pulse repetition period and formatted into a two-dimension signal, the two-dimension signal with Na multiplied by Nr is obtained after the total data is stored, thus finishing the fine simulation of the linear frequency modulation continuous wave synthetic aperture radar video signal. The more accurate echo simulation signal can be obtained by utilizing the simulation method, and the simulation method is especially suitable for a frequency modulation continuous wave signal with high-speed movement, long distance and severe oblique observation condition of the radar and has more excellent realization efficiency, and stronger adaptability and compatibility.

The invention relates to a compressive-sensing-based sparse signal under-sampling method and an implementation device, which are used for lowering a sampling rate of frequency-domain sparse signals on the premise of guaranteeing the restoration effect of the signals. The method comprises the following steps of: generating a trigger signal and an m sequence by an FPGA (Field Programmable Gate Array), carrying out frequency mixing on the m sequence and the measured sparse signal after the m sequence is modulated, and carrying out filtering by a low pass filter; sampling the filtered signal and storing sampled data by a data sampling module after the data sampling module detects the triggering signal; and calculating a transfer function of a system and the m sequence corresponding to the sampled data when the signal is reconstructed, and then restoring the original signal by an OMP (Orthogonal Matching Pursuit) signal reconstructing algorithm. The compressive-sensing-based sparse signal under-sampling method and the implement device are suitable for the under-sampling of frequency-domain sparse analogue signals.

The invention discloses a method and device for measuring the frequencies of high-frequency cosine signals under the undersampling rate, and relates to the field of digital signal processing. By combining the type of the zero crossing point with the distribution characteristic of apFFT phase spectrums, L spectrum position index values are selected from 2L peak value magnitude spectrum positions; according to the remainder selecting result, each apFFT phase spectrum is corrected through the all-phase ratio interpolation method so that the frequency of the apFFT phase spectrum can be estimated; the frequency estimation value obtained after each apFFT phase spectrum is corrected is used as a remainder, the remainders are processed according to the Chinese remainder theorem of the closed analysis form, and the frequencies of the original high-frequency signals are reconstituted through the frequency estimation values. According to the method and the device, the frequencies of the multiple paths of high-frequency cosine signals under the undersampling rate are measured, and the measuring range of the frequencies of the high-frequency signals is greatly widened; the novel spectrum correction method is adopted, and therefore the measuring accuracy of the frequencies of the high-frequency cosine signals is improved, and novel anti-noise performance of the high-frequency cosine signals under the low undersampling rate is ensured.

The invention discloses a broadband spectrum sensing method based on a space-frequency joint compressed sensing. The method comprises the technology of synchronization of compressing and sampling and direct-acquisition of compressed data and wireless sensor network spectrum sensing technology, and constructs a spatial wavelet and a two-dimensional compaction of airspace and a frequency domain method. The broadband spectrum sensing method based on the space-frequency joint compressed sensing has the advantages of improving detection probability of a spectrum hole by perceiving double sparsity of electricity in airspace and frequency domain on the premise that a compression ratio is not increased.

The invention discloses a voltage and power balance control method for a modular power electric transformer. The power electric transformer to which the method is applied to comprises an input stage, an isolation stage and an output stage; the input stage adopts common duty ratio control based on single phase dp decoupling, so that stable control of high voltage side direct current voltage and flexible adjustment of sine and power factors of input current are achieved; the isolation stage adopts a voltage power double loop control strategy without a current sensor, the output voltage outer loop adjustment generates a unified reference value of each power inner loop, and the adjustment of each power inner loop generates a phase shifting angle of each module of the isolation stage; and two types of control strategies of the input stage and the isolation stage act synergistically, so that voltage and power balance of each module of the power electric transformer is achieved.

The invention provides a compressed spectrum sensing method based on autocorrelation matrix reconstitution and mainly solves the problem that an existing sensing algorithm is high in sampling speed and large computation overhead. The compressed spectrum sensing method comprises that a secondary user obtains an observation sequence of a frequency spectrum environment through compressed sensing and obtains an autocorrelation matrix estimated value of Nyquist sampling by utilizing autocorrelation vector quantity of a autocorrelation matrix reconstitution Nyquist sample sequence of the observation sequence; a multi-signal classification MUSIC algorithm is adopted to obtain an estimated value of occupied channel number according to a characteristic value of the autocorrelation matrix estimated value; a characteristic spectrum is constructed according to the characteristic value and the estimated value of the occupied channel number, spectral amplitude values corresponding to characteristics of channels are added to obtain a sum, and mark numbers of the occupied channels are judged. By means of the compressed spectrum sensing method, the sampling speed of a secondary user receiving machine can be reduced, algorithm complexity at the reconstitution end is low, and spectral amplitude occupying situation in a cognitive radio system can be judged quickly.

A method for realizing total digital wireless communication system utilizing quick Fourier conversion is that at the emit end, the transmitted data is in the structure of burst based on packets to form a symbol stream used in transmission by channel encoding, channel interlace and symbol image device and to turn the serial into the parallel as the input of orthogonal modulator which caries out P times orthogonal modulation to each set N point input symbol sequence in the following steps: carrying out frequency domain phase rotation to the input N points symbol sequence, quickly inverting the Fourier conversion then to rotate the time domain phase, regulate the sequence via parallel/serial conversion, adding circulation prefix and modules converter to be emitted, at the receive end, signals received by the antenna are turned to output data by modules conversion, serial/parallel conversion and phase rotation N points quick Fourier conversion, channel estimation frequency balance, parallel/serial conversion, symbol inversed image channel de-interlace and channel decode.

The invention discloses a UHV DC transmission line protection method utilizing current abrupt change characteristics based on a distributed parameter model. The UHV DC transmission line protection method comprises the steps of processing voltage and current signals measured by transformers at both ends of a DC line by means of an intelligent electronic device (IED), and identifying internal and external faults according to polarities of current abrupt variables. The UHV DC transmission line protection method adopts a distributed parameter model for carrying out distributed capacitive current compensation, eliminates the influence of asynchronization of the distributed capacitive current and data. A protection criterion selects components with the frequency band of [0,100] Hz in current information, avoids the electromagnetic coupling between DC side characteristic harmonics and a bipolar DC line and the influence of lightning interference. The polarities of current abrupt variables at both ends of the line are Boolean quantities, and the communication traffic of longitudinal channels is small. The UHV DC transmission line protection method utilizing the current abrupt change characteristics based on the distributed parameter model only utilizes polarities of the current abrupt variables for identifying the internal and external faults, is simple in principle and small in communication traffic, and is stable and reliable.

The invention relates to a method for acquiring a wide-band frequency modulation stepped chaos radar signal, which comprises the following steps: acquiring an echo baseband signal rn(t) of each subpulse; then, correspondingly carrying out matched filtering or correlation processing on the baseband echo signal rn(t) of each subpulse and the respective baseband chaos sequence, thus obtaining a frequency domain signal Un(f) of each subpulse; carrying spectral migration on the frequency domain signal Un(f) of each subpulse, and then carrying out de-overlapping and phase compensation, wherein the frequency shift quantity of the spectral migration is equal to the frequency interval DELTAf of a local frequency source; and carrying out coherence stack on the subpulse signal subjected to de-overlapping and phase compensation, thus obtaining a synthesized large wide-band signal, wherein the band width of the synthesized wide-band signal is B+(N-1)DELTAf. The invention provides a new technical route for realizing a chaos radar signal having an ultra large band width. By combining the chaos signal and the frequency stepped signal, the advantages of the both are combined. The method provided by the invention is simple and clear, is easy to realize, is applicable to frequency linear/nonlinear stepping and has important practical meanings in an actual system.

The invention discloses a passive underwater target positioning method based on the compressed sensing of a multipath time delay structure. The method includes dividing a positioned three-dimensional region into N grid points; distributing a plurality of underground nodes on the shallow seabed, and positioning according to sea surface reflection path signals of nodes and delays of direct path signals of reference paths; performing sparse representation on the receive signals of the nodes under different delays of reference signal receive nodes; then comprising and sampling node data except for the reference nodes by means of random sampling matrix, positioning the central node and acquiring the target position by acquiring the target position sparse vectors by the compressed sensing recovery algorithm according to node observation data. By the aid of the method, the sampling rate of underground nodes can be decreased greatly, the requirements on underwater communication bandwidth are lowered, and the method is adaptive to target positioning in the multipath underwater environment, is easy to implement and has high practical applicant value.

The invention relates to the field of voice talkback, in particular to a voice talkback device and method based on a LORA (Long Range) technology. The device comprises a gateway and a node, wherein the gateway is in a communication connection with the node; the gateway is equipment in which a LoRa gateway and a server are integrated; the node is LoRa talkback equipment; the gateway comprises a gateway microcontroller, a gateway LoRa radiofrequency module and a gateway power supply module; the gateway LoRa radiofrequency module and the gateway power supply module are connected with the gateway microcontroller respectively; the node comprises a node microcontroller, a node LoRa radiofrequency module, a node power supply module, a play module and an audio encoder/decoder; and the node LoRa radiofrequency module, the node power supply module, the play module, an input module and the audio encoder/decoder are connected with the node microcontroller respectively. Through adoption of a LoRa communication technology and the audio encoder/decoder, the problems of large size and short standby time of an existing interphone are solved by means of the characteristics of low power consumption, long distance and low price of LoRa.

The invention relates to an ultra-wideband receiving method based on the frequency division section parallel sampling and mainly comprises the following steps: converting multi-channel analog signals treated by each radio frequency module into multi-channel digital baseband signals; carrying out the pretreatment of synchronization and frequency-offset correction of the digital baseband signals; carrying out frequency diversity of pretreated data on different carrier frequencies; recovering and treating the data after the frequency diversity and obtaining the received data needed. The invention also relates to a receiving terminal which realizes an ultra-wideband system. A receiving method and the receiving terminal thereof which can realize the ultra-wideband system take full advantages of richer spectrum resources of the ultra-wideband system and adopt a baseband treatment scheme based on the frequency division section parallel sampling and the frequency diversity, which can effectively reduce the sampling rate of ADC and the operation bandwidth of radio frequency devices such as a low-noise amplifier, a frequency mixer, and the like, thus greatly reducing the difficulty and the complexity of designing ultra-wideband chips and realizing the system.

The invention discloses an island microgrid hierarchical control strategy based on an event triggering mechanism. According to the control strategy, a primary control model dominated by droop controlis established and is responsible for reasonably distributing active power and reactive power; and the problem of voltage and frequency deviation is solved. A control strategy based on centralized event triggering is designed; an auxiliary centralized controller is used for generating a DG synchronous trigger signal to update control input; on the basis, a voltage control strategy based on distributed event triggering is designed and popularized to frequency and active power control, each DG generates asynchronous triggering signals through a local controller of the DG to update respective control input, and complete distributed event triggering control is achieved. Compared with a traditional control strategy, invalid sampling signals are reduced, the economical efficiency of system operation is improved, and meanwhile the degree of dependence of secondary control on a communication network is reduced.

The invention provides a dechirp receiving method of a radar echo signal. The method comprises the following steps: A, performing analog-digital conversion for a received radar echo signal in an analog form to obtain a radar echo signal in a digital form; B, generating a reference local oscillator signal in the digital form; C, multiplying the radar echo signal in the digital form by the reference local oscillator in the digital form so as to counteract a secondary phase term of which the frequency linearly changes over time in the digital echo signal and obtain a dot frequency signal related to a target position, thus finishing the dechirp receiving of the radar echo signal. According to the dechirp receiving method of the radar echo signal, a dechirp reference signal in the digital form is adopted, an analog dechirp reference signal can be avoided generating, and therefore, the size, power consumption and interference are reduced while the difficulty and complexity are lowered down.

The invention discloses a partial K space sequence image reconstruction method based on self-adapted double-dictionary learning, and the method is mainly used for solving the problems of an existing method that the quality of a reconstructed image is more seriously reduced under the condition of sampling under 10 times. The partial K space sequence image reconstruction method comprises the following main steps of: collecting partial K space data and utilizing the correlation between the partial K space data to be integrated into complete K space data; obtaining a training image by the complete K space data; utilizing a KSVD (Kernel Singular Value Decomposition) algorithm to train the training image to obtain dictionaries with high and low resolution ratios; and utilizing a relation between the dictionaries with the high and low resolution ratios to reconstruct the input partial K space data, and carrying out residual error compensation on the reconstructed image to obtain a more accurate reconstruction result. According to the partial K space sequence image reconstruction method disclosed by the invention, the quality of the reconstructed image can be effectively improved under the condition of sampling under 10 times; and the partial K space sequence image reconstruction method can be used for reconstructing MRI (Magnetic Resonance Imaging) sequence images of a plurality of parts.

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 method includes following steps: through software, a radiotechnics is introduced into demodulator based on structure of limiter coupling with discriminator to make the angle resolution of demodulator is not limited by sampling rate; the reception matched filter adopts root raised cosine filter (RRCF) to make problem of which demodulator with structure of hardware limiter is sensitive to roll-off factor of root raised cosine filter is solved. The invention can be applied in PHS and PCS system, signal demodulation based on PSK modulation technology like satellite communication system.