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31results about How to "Lower SNR Threshold" patented technology

Data-assisted satellite-borne AIS (automatic identification system) signal synchronization parameter estimation method and system

A data-assisted satellite-borne AIS signal synchronization parameter estimation method comprises that an antenna receives a radio frequency signal emitted by an earth ship AIS system and sends the radio frequency signal to a receiver; the receiver demodulates the received radio frequency signal into a baseband signal and inputs the demodulated radio frequency signal into an FPGA (field programmable gate array) data acquisition module; the FPGA data acquisition module subjects the received baseband signal to analog-digital conversion to obtain a digital baseband signal and inputs the digital baseband signal into a signal processing module; the signal processing module processes the received digital baseband signal to obtain correct AIS ship information and to send the correct AIS ship information into a data storage module; and the data storage module stores the received AIS ship information. The data-assisted satellite-borne AIS signal synchronization parameter estimation method has the advantages that under signal downsampling and by introducing the self-correlation operation and the maximum likelihood operation, the performance of large estimation range and small estimation error of frequency offset of the satellite-borne AIS signal can be achieved; and through the accumulation argument operation and the accumulation module value operation, high-accuracy timing estimation, phase shift estimation and amplitude estimation are achieved.
Owner:山东星通易航通信科技有限公司

Maneuvering target detection method based on time-frequency analysis

The invention provides a maneuvering target detection method based on time-frequency analysis. The maneuvering target detection method based on time-frequency analysis comprises the following steps that radar echo signals of a sky wave radar in a first position range are obtained as first radar echo signals, wherein the radar echo signals comprise maneuvering target echoes; phase transformation is carried out on the first radar echo signals, and second radar echo signals are obtained; a joint domain based on time and instant frequency change rates is obtained by carrying out matching Fourier transformation related to the instant frequency change rates of a maneuvering target on the second radar echo signals at different moments respectively; in an established coordinate system with the time and the instant frequency change rates as coordinate axes, integration is carried out on the joint domain along a straight line which is parallel to the time coordinate axis and corresponds to different instant frequency change rates, and an energy function of the accumulated maneuvering target is obtained; whether the energy function is smaller than a preset energy threshold value or not is judged; when the energy function is larger than or equal to the energy threshold value, it is determined that the maneuvering target is within the first position range.
Owner:UNIV OF ELECTRONICS SCI & TECH OF CHINA

Adaptive turbo equalization method, equalizer and underwater acoustic communication system

The invention relates to an adaptive turbo equalization method, an equalizer and an underwater acoustic communication system. The method comprises the following steps: calculating a primary symbol estimated value (the formula is as shown in the specification) according to a received symbol sequence r (i) and a priori symbol mean vector (the formula is as shown in the specification); calculating a symbol estimated value (the formula is as shown in the specification) fed back by a prior variance according to the primary symbol estimated value (the formula is as shown in the specification) and a prior symbol variance v (i); and calculating an output log likelihood ratio LLR of each symbol according to the symbol estimated value (the formula is as shown in the specification) fed back by the prior variance. The priori symbol information is mapped to obtain a priori symbol mean and a priori symbol variance. According to the adaptive turbo equalization method provided by the invention, the priori symbol information output by an SIOS decoder is better utilized, the communication performance under time-varying multipath is improved, and the signal to noise ratio threshold is reduced.
Owner:INST OF ACOUSTICS CHINESE ACAD OF SCI

Stochastic resonance and wavelet transform combined symbol rate estimation method and device under low signal to noise ratio condition

InactiveCN108737302AMake up for the shortcomings of easy divergenceLower SNR ThresholdData rate detection arrangementsFrequency spectrumIntermediate frequency
The invention belongs to the technical field of digital communication and particularly relates to a stochastic resonance and wavelet transform combined symbol rate estimation method and device under alow signal to noise ratio condition. The method comprises the steps of carrying out digital sampling on sending signals in a channel, thereby obtaining high power sampled signals; shifting spectrum of the high power sampled signals to intermediate frequency, obtaining intermediate frequency signals, and determining bistable stochastic resonance system parameters; and carrying out iterative processing on the intermediate frequency signals through a bistable stochastic resonance system; carrying out wavelet transform on the signals after the iterative processing; and calculating modulus spectrum for the signals after the wavelet transform, and obtaining symbol rate estimation through observation of peak positions. According to the method and the device, influences that an effect is poor anda wavelet scale is difficult to determine when stochastic resonance is employed independently are compensated, the accurate estimation for symbol rates of weak MPSK and MQAM intermediate frequency signals under a low signal to noise ratio is realized. A simulation experiment shows that output peaks are improved to a certain degree, a signal to noise ratio threshold is reduced, and the method andthe device are significant in the symbol rate estimation under the low signal to noise ratio.
Owner:PLA STRATEGIC SUPPORT FORCE INFORMATION ENG UNIV PLA SSF IEU

Underwater acoustic communication transmission method based on Farrow filtering and codeword matching

The invention relates to an underwater acoustic communication transmission method based on Farrow filtering and codeword matching. The method comprises the steps: 1) setting a simulation underwater acoustic FTN channel, and setting an irregular code matched with the channel; 2) realizing the FTN quick forming by a transmitting end based on a Farrow filter; 3) realizing the Doppler compensation andFTN quick sampling by a receiving end based on Farrow filtering; and 4) realizing the direct adaptive turbo equalization by the receiving end based on the irregular code, wherein for the received symbol sequence obtained in the step 3), inter-symbol interference caused by time-varying underwater acoustic channel and FTN pulse forming is eliminated based on direct adaptive turbo equalization, anda decoder adopted by a receiving end is the decoder of the irregular code matched with the channel in the step 1). Through the method and the device, a self-adaptive filter parameter setting mechanismcan be established, the method and the device are suitable for FTN transmission at any symbol rate. Meanwhile, a channel coding mode is matched with actual channel characteristics.
Owner:INST OF ACOUSTICS CHINESE ACAD OF SCI

Burst frame detection and timing synchronization method and system based on Wi-SUN system

The invention relates to a burst frame detection and timing synchronization method and system based on a Wi-SUN system. According to the burst frame detection and timing synchronization method and system, in cross-correlation burst frame detection, peak merging and peak-to-average ratio calculation are added, and the signal-to-noise ratio threshold of burst frame detection is reduced. According tothe invention, the repetition and inversion characteristics of the short predecessor are utilized; a specific local correlation sequence is constructed; a conventional multi-peak maximum evaluation timing correction method is converted into single-peak timing estimation, so that the system avoids the problem of main and auxiliary peak position exchange caused by multi-peak noise interference in alow signal-to-noise ratio environment, the timing calibration reliability is improved, and wider working conditions are provided for accurate timing and frequency offset adjustment of a subsequent long-lead sequence.
Owner:北京中宸微电子有限公司

Method for estimating direction of coherent source based on central symmetry of uniform circular array

The invention provides a method for estimating the direction of a coherent source based on the central symmetry of a uniform circular array. The method comprises the following steps: 1, calculating amode space conversion matrix T for the data X(t) received by a UCA, and multiplying the data X(t) by a transformation matrix T to obtain the mode space data Y(t); 2, solving the data Z(t) after conjugate averaging; 3, solving a reconstructed Hermitian Toeplitz matrix RToe; 4, performing characteristic decomposition of RToe, and outputting an estimation result of the DOA of the coherent source through employing a Root-MUSIC algorithm. The method is simple in implementation, and is small in the calculation burden. The method has the advantages of strong decoherence capability, high DOA estimation precision and low signal to noise ratio threshold. A simulation result shows that the method can correctly estimate the DOA of the coherent source, and is higher in resolution than MODEFBSS and MODETOEP. The method has stronger decoherence and higher DOA estimation accuracy at low SNR and small number of snapshots.
Owner:HARBIN ENG UNIV

Underwater acoustic communication balanced decoding method based on recursive chaotic code

The invention discloses an underwater acoustic communication balanced decoding method based on a recursive chaotic code, and the method comprises: step 1, inputting an information source information sequence into a recursive chaos model by a coding sending end, carrying out the recursive chaotic coding, generating a symbol frame sequence, generating an information sub-frame, and sending the information sub-frame after signal modulation to a coding receiving end; step 2, the coding receiving end demodulating the received information subframes to generate a symbol sequence, and generating a joint equalization decoding tree according to the number of information fragments in the symbol sequence and the number of information fragments in the information source information sequence; and step 3,the coding receiving end calculating the Euclidean distance between the symbol sequence in each branch and the symbol sequence which is actually received, selecting the branch with the minimum Euclidean distance, and marking the branch as a decoding result. Through the technical scheme provided by the invention, the bit error rate performance of the underwater acoustic communication system is improved, the influence of strong inter-code crosstalk of the underwater acoustic channel and the complexity of a joint equalization decoding algorithm are reduced, and the transmission reliability of the underwater acoustic channel is improved.
Owner:INST OF ACOUSTICS CHINESE ACAD OF SCI

Method and device for estimating frequency ramp and frequency deviation in satellite mobile communication system

The invention discloses a method and a device for estimating a frequency ramp and a frequency deviation in a satellite mobile communication system. The method comprises the following steps of: according to parameters of an actual communication system, obtaining a range of a normalized frequency ramp value aD and calculating a trial interval delta aD of the frequency ramp value; carrying out repeated test on the normalized frequency ramp value aD by utilizing a frequency deviation estimating method, wherein the test interval each time is delta aD, one or a plurality of (aD, fD) number pairs are obtained in each trial process, and a set is formed by all the (aD, fD) number pairs after all the test processes are completed; and substituting all the (aD, fD) number pairs in the set into a likelihood function G (aD, fD), searching the (aD, fD) number pair capable of ensuring the likelihood function to attain the maximum value and using the (aD, fD) number pair as estimation values of the frequency ramp and the frequency deviation. The method and the device have the advantages of low SNR (Signal to Noise Ratio) threshold, low computational complexity and high estimation accuracy. In the actual application, the existing module can be continuously used in the method for estimating the frequency deviation, the estimation on the frequency ramp can be realized without great improvement, and the method and the device are very convenient.
Owner:PEKING UNIV

QFM signal parameter evaluation method based on four-order asymmetrical product type kernel function

The invention belongs to the technical field of radar signal detection and evaluation, and particularly relates to a QFM signal parameter evaluation method based on a four-order asymmetrical product type kernel function. The method includes the steps of firstly, calculating the initial signal energy, setting a circulation initial value and establishing a matrix used for storing all subsequent component parameter estimation values; secondly, multiplying the time delay function of the four-order asymmetrical product type kernel function with the conjugation time delay function of the four-order asymmetrical product type kernel function, and conducting phase matching and converting on phases of the four-order asymmetrical product type kernel function, wherein the estimation values of the second parameters of the signal components can be obtained in the positions of frequency domain peak values; thirdly, constructing a new four-order asymmetrical product type kernel function for signals with compensation conducted on the second parameter estimation values, and conducting fast Fourier transform to obtain a frequency-frequency change rate two-dimensional distribution diagram, wherein third parameter estimation values and third parameter estimation values of the signal components can be obtained from the positions of the peak values; fourthly, filtering the signal components, estimated in the steps, out of the signal; fifthly, resetting cyclic variables and a signal, and calculating the ratio of the total energy of the signal to the initial signal energy.
Owner:XIDIAN UNIV

Non-equal probability constellation labeling method based on absolute phase shift keying (APSK) constellation diagram

Disclosed is a non-equal probability constellation labeling method based on an absolute phase shift keying (APSK) constellation diagram. The non-equal probability constellation labeling method based on the APSK constellation diagram is characterized by comprising the steps that: the APSK constellation diagram is constructed, number of steps of the constellation labeling is M, M=2m, and m is a positive integer, numbers of constellation points on each ring is the same, phase deviations of each ring are also the same; a constellation labeling mode of the APSK constellation diagram is designed, and the constellation labeling mode is enabled to be a gray labeling; the constellation points are grouped, and constellation points on the same ring are combined to be a new constellation point; labeling bits of the prior constellation points on the same ring are distributed to the new constellation point in sequence. According to the non-equal probability constellation labeling method based on the APSK constellation diagram, the inhomogeneous constellation diagram and a non-equal probability labeling technology are adopted, distribution of output signals of the constellation labeling is enabled to be close to Gaussian distribution, shaping gain is achieved, performance of a coded modulation system is improved, and signal to noise ratio in a modulation process is reduced.
Owner:TSINGHUA UNIV +1

Estimation Method of Low Elevation Angle for Meter Wave Radar Based on Minimum Redundancy Linear Sparse Subarray

ActiveCN103885049BGood angle measurement performanceIncrease the number ofWave based measurement systemsDecompositionTarget signal
The invention discloses a meter-wave radar low elevation estimating method based on a minimum redundancy linear sparse submatrix. The meter-wave radar low elevation estimating method based on the minimum redundancy linear sparse submatrix mainly solves the problem that errors of estimation of meter-wave radar low elevations are large in the prior art. The meter-wave radar low elevation estimating method based on the minimum redundancy linear sparse submatrix comprises the implementation steps of (1) structuring a minimum redundancy linear sparse submatrix meter-wave radar, (2) extracting target signals from radar echoes, (3) calculating auto-covariance matrixes of submatrixes and cross covariance matrixes among the submatrixes, (4) structuring an augmented matrix of whole array data covariance matrixes, (5) restoring the rank of the augmented matrix by applying a spatial smoothing algorithm of distributed submatrixes, (6) carrying out characteristic decomposition on the covariance matrixes to obtain signal subspaces, (7) obtaining direction cosine non-fuzziness coarse estimation, (8) obtaining direction cosine fuzziness fine estimation, and (9) solving the fuzziness of the fine estimation by using the coarse estimation to obtain low elevation estimation with high precision and without fuzziness. According to the meter-wave radar low elevation estimating method based on the minimum redundancy linear sparse submatrix, the aperture of the meter-wave radar is expanded, the threshold of the signal to noise ratio is lowered, the precision of the lower elevation estimation is improved, and the method can be used for positioning and tracking targets.
Owner:XIDIAN UNIV

Space maneuvering target ISAR imaging method, device and equipment and storage medium

The invention provides a space maneuvering target ISAR imaging method, device and equipment and a storage medium, and the method comprises the steps: carrying out the pulse compression and motion compensation of an echo signal, obtaining an original signal, carrying out the order reduction of the original signal through a high-order fuzzy function, achieving the parameter estimation through a coherent accumulation cubic phase function, and reconstructing the original signal, thereby achieving the ISAR imaging. According to the scheme, the second-order parameter and the third-order parameter of the original signal can be estimated at the same time, the calculation efficiency is high, and the calculation complexity is reduced; and meanwhile, by increasing self-term energy, the signal-to-noise ratio threshold is reduced, and the robustness of parameter estimation under the low signal-to-noise ratio is improved.
Owner:北京理工大学重庆创新中心 +1

A light source arrangement method for an indoor visible light communication system

The invention relates to the visible light communication, the indoor visible light illumination, the indoor plastic optical fiber communication and the indoor plastic optical fiber illumination fields, and more particularly to a light source arranging method for an indoor visible light communication system. The method comprises: establishing a three-dimensional model based on the indoor spatial parameters; and calculating the light source power at each position of the entire ceiling plane by minimizing the variance of the received plane signal-to-noise ratio to ensure the indoor reliable and uniform communication quality and ensure that the illumination plane satisfies the minimum illumination intensity standard. According to the calculation result, the light source is divided into two types and the commercial LED light source with the corresponding emission power is arranged as the main light in the first type light source position, and a part of the light emitted from the LED light source is optically coupled into the plastic optical fiber through an optical device and is guided to the second type light source position as a secondary light source, therefore achieving indoor visible light communication and illumination combined by the LED and plastic optical fiber. The method can be performed simply, and at a low cost, the reliability and the uniformity of the communication quality are ensured, delivering the goal of conserving energy.
Owner:ZHONGTIAN BROADBAND TECH +1

Parameter estimation method of qfm signal based on fourth-order asymmetric product kernel function

The invention belongs to the technical field of radar signal detection and evaluation, and particularly relates to a QFM signal parameter evaluation method based on a four-order asymmetrical product type kernel function. The method includes the steps of firstly, calculating the initial signal energy, setting a circulation initial value and establishing a matrix used for storing all subsequent component parameter estimation values; secondly, multiplying the time delay function of the four-order asymmetrical product type kernel function with the conjugation time delay function of the four-order asymmetrical product type kernel function, and conducting phase matching and converting on phases of the four-order asymmetrical product type kernel function, wherein the estimation values of the second parameters of the signal components can be obtained in the positions of frequency domain peak values; thirdly, constructing a new four-order asymmetrical product type kernel function for signals with compensation conducted on the second parameter estimation values, and conducting fast Fourier transform to obtain a frequency-frequency change rate two-dimensional distribution diagram, wherein third parameter estimation values and third parameter estimation values of the signal components can be obtained from the positions of the peak values; fourthly, filtering the signal components, estimated in the steps, out of the signal; fifthly, resetting cyclic variables and a signal, and calculating the ratio of the total energy of the signal to the initial signal energy.
Owner:XIDIAN UNIV

Bidirectional frequency domain Turbo equalization method adopting expected propagation

The invention discloses a bidirectional frequency domain Turbo equalization method adopting expected propagation, and the method comprises the steps: S1, receiving a transmission signal of an underwater acoustic or wireless channel, and approximately deducing the posteriori distribution characteristics of symbol bits of a received signal through employing an EP soft mapping method; S2, processingthe received signal by adopting a bidirectional frequency domain soft equalization method to obtain equalization external information; S3, combining the bidirectional equalization external informationby using a covariance-assisted bidirectional combination method; S4, inputting the combined external information into a Log-MAP decoding judgment method to obtain decoded external information, inputting the decoded external information into an EP soft mapping method as priori, and repeating the steps S1-S4; S5, determining whether the number of iterations reaches a preset number of iterations ornot, and if not, continuing to execute the steps S1-S4; and if so, determining decoding by utilizing a Log-MAP decoding judgment method, and outputting a decoding code word.
Owner:HANGZHOU DIANZI UNIV

A data-assisted method and system for estimating synchronization parameters of spaceborne AIS signals

A data-assisted satellite-borne AIS signal synchronization parameter estimation method comprises that an antenna receives a radio frequency signal emitted by an earth ship AIS system and sends the radio frequency signal to a receiver; the receiver demodulates the received radio frequency signal into a baseband signal and inputs the demodulated radio frequency signal into an FPGA (field programmable gate array) data acquisition module; the FPGA data acquisition module subjects the received baseband signal to analog-digital conversion to obtain a digital baseband signal and inputs the digital baseband signal into a signal processing module; the signal processing module processes the received digital baseband signal to obtain correct AIS ship information and to send the correct AIS ship information into a data storage module; and the data storage module stores the received AIS ship information. The data-assisted satellite-borne AIS signal synchronization parameter estimation method has the advantages that under signal downsampling and by introducing the self-correlation operation and the maximum likelihood operation, the performance of large estimation range and small estimation error of frequency offset of the satellite-borne AIS signal can be achieved; and through the accumulation argument operation and the accumulation module value operation, high-accuracy timing estimation, phase shift estimation and amplitude estimation are achieved.
Owner:山东星通易航通信科技有限公司

GPS satellite M code signal demodulation method based on combination of short code dispreading and timing recovery

The invention provides a GPS satellite M code signal demodulation method based on combination of short code dispreading and timing recovery. The mutual promotion relation of short code dispreading and timing recovery is utilized, the signal-to-noise ratio threshold of demodulation can be effectively reduced, the antenna aperture is equivalently reduced, and the construction cost is saved. Firstly, the carrier frequency and carrier phase of a GPS satellite navigation signal are obtained through a typical carrier estimation method, carrier recovery and IQ separation are conducted, and extraction of a GPS M code signal is further achieved through band-pass filtering; and short code decoding is performed on the GPS M code signal to obtain coding gain, timing synchronization is performed by adopting blind processing for the first time on the basis, M code streams including innovation of the M code signals is solved after judgment, and the innovation is fed back to a front end to perform timing synchronization operation on the signals again. The timing synchronization precision can be improved.
Owner:中国人民解放军63891部队

Method and device for estimating frequency ramp and frequency deviation in satellite mobile communication system

The invention discloses a method and a device for estimating a frequency ramp and a frequency deviation in a satellite mobile communication system. The method comprises the following steps of: according to parameters of an actual communication system, obtaining a range of a normalized frequency ramp value aD and calculating a trial interval delta aD of the frequency ramp value; carrying out repeated test on the normalized frequency ramp value aD by utilizing a frequency deviation estimating method, wherein the test interval each time is delta aD, one or a plurality of (aD, fD) number pairs are obtained in each trial process, and a set is formed by all the (aD, fD) number pairs after all the test processes are completed; and substituting all the (aD, fD) number pairs in the set into a likelihood function G (aD, fD), searching the (aD, fD) number pair capable of ensuring the likelihood function to attain the maximum value and using the (aD, fD) number pair as estimation values of the frequency ramp and the frequency deviation. The method and the device have the advantages of low SNR (Signal to Noise Ratio) threshold, low computational complexity and high estimation accuracy. In the actual application, the existing module can be continuously used in the method for estimating the frequency deviation, the estimation on the frequency ramp can be realized without great improvement, and the method and the device are very convenient.
Owner:PEKING UNIV

Bit interleaving method for digital TV ground transmission

The present invention discloses one kind of bit interleaving method for digital TV ground transmission. The method performs bit interleaving treatment of data block TPC(M2XN2) obtained via coding TPC(M2, M1, N2, N1), and there are K data blocks TPC(M2XN2) after TPC coding in the bit interleaving of each time. In the first step, the bit data in the same position of the TPC blocks from 1 to K are output successively and the data in all TPC blocks are output in diagonal order; and in the second step, the bit flow is divided into L blocks of P bits each and the data in [L / 2] or [L / 2]+1 blocks have the adjacent bits exchanged while maintaining the other blocks unchanged. The present invention can further strengthen the burst error resisting ability of digital TV ground transmission system.
Owner:SHANGHAI JIAO TONG UNIV

Real value rooting multiple signal classification method and system, computer equipment and application

PendingCN112965059ASolve the problem of insufficient estimation precisionReduce real-time processing pressureComplex mathematical operationsRadio wave reradiation/reflectionRadar systemsComputation complexity
The invention belongs to the technical field of radars, and discloses an actual value rooting multiple signal classification method and system, computer equipment and application. The method comprises the following steps: carrying out dimension reducing treatment on received data; splicing a real part and an imaginary part of the received data in a low-dimensional space by using the non-circular characteristic of the signal to obtain real value received data with the number of virtual array elements doubled; constructing a new steering vector and a new noise subspace, and constructing a real coefficient polynomial according to the orthogonality of the new steering vector and the new noise subspace; and obtaining the estimation of the target orientation by solving the root of the real coefficient polynomial. The angle estimation precision of a subspace estimation algorithm can be greatly improved, the problem that the estimation precision of the subspace algorithm is insufficient under the condition that the signal-to-noise ratio is low and the number of snapshots is limited is solved, and a better reality scheme is provided for MIMO radar target angle estimation on occasions with low snapshots and the low signal-to-noise ratio. Meanwhile, the problem of calculation complexity is considered, and the real-time processing pressure of a radar system is relieved by jointly adopting a dimension reduction method and a real-valued method.
Owner:XIAN UNIV OF POSTS & TELECOMM

Symbol rate estimation method and device of stochastic resonance joint wavelet transform under low signal-to-noise ratio

InactiveCN108737302BMake up for the shortcomings of easy divergenceLower SNR ThresholdData rate detection arrangementsFrequency spectrumAlgorithm
The invention belongs to the technical field of digital communication and particularly relates to a stochastic resonance and wavelet transform combined symbol rate estimation method and device under alow signal to noise ratio condition. The method comprises the steps of carrying out digital sampling on sending signals in a channel, thereby obtaining high power sampled signals; shifting spectrum of the high power sampled signals to intermediate frequency, obtaining intermediate frequency signals, and determining bistable stochastic resonance system parameters; and carrying out iterative processing on the intermediate frequency signals through a bistable stochastic resonance system; carrying out wavelet transform on the signals after the iterative processing; and calculating modulus spectrum for the signals after the wavelet transform, and obtaining symbol rate estimation through observation of peak positions. According to the method and the device, influences that an effect is poor anda wavelet scale is difficult to determine when stochastic resonance is employed independently are compensated, the accurate estimation for symbol rates of weak MPSK and MQAM intermediate frequency signals under a low signal to noise ratio is realized. A simulation experiment shows that output peaks are improved to a certain degree, a signal to noise ratio threshold is reduced, and the method andthe device are significant in the symbol rate estimation under the low signal to noise ratio.
Owner:PLA STRATEGIC SUPPORT FORCE INFORMATION ENG UNIV PLA SSF IEU

A method for detecting the number of sources of acoustic vector circular array based on eigenvalue multi-threshold correction

The invention belongs to the acoustic vector sensor array signal processing field, and more specifically relates to an acoustic vector circular array source number detection method based on characteristic value multiple threshold correction which is applied to underwater target remote passive detection. The method comprises establishing an acoustic vector circular array signal receiving model, obtaining acoustic vector circular array receiving acoustic pressure data, radial vibration velocity data and tangential vibration velocity, constructing a covariance matrix of acoustic vector circular array acoustic pressure and vibration velocity combined treatment, and decomposing characteristic values; and performing multiple threshold division treatment on a characteristic value set obtained by decomposing the covariance matrix to obtain a signal and noise corresponding characteristic value set. The method dynamically integrates an information theory detection method based on characteristic value multiple thresholds and the sound anti-noise performance of an acoustic vector circular array, obviously reduces the signal to noise ratio threshold of a detection algorithm, and overcomes the disadvantages that traditional detection methods such as MDL, diagonal loading MDL, and GDE are more sensitive to noise characteristic value change.
Owner:HARBIN ENG UNIV

Estimation Method of Weak Ofdm Subcarrier Number Based on Stochastic Resonance

The invention belongs to the field of communication technology, and particularly to a weak OFDM subcarrier number estimation method based on random resonance. The method comprises the steps of settinga sampling frequency, wherein the sampling frequency is N times of a lowest sampling frequency, wherein N is not less than 50; selecting a bistable random resonance system parameter; for aiming at asignal which passes a bistable random resonance system, calculating a cepstrum and / or performing Haar wavelet transformation, and calculating an actual subcarrier number. The method of the invention is based on a cepstrum method and a wavelet improvement method. A random resonance method is used for reinforcing the weak OFDM signal. Compared with a traditional method, the weak OFDM subcarrier number estimation method has advantages of increasing an output peak value, improving detecting performance, reducing signal-to-noise ratio threshold, exerting an advantage on the condition of severe channel environment, improving estimation precision, improving algorithm performance for estimating the number of OFDM signal subcarriers to a relatively high extent, performing certain advantage on the condition of low signal-to-noise ratio, realizing better effectiveness and robustness, and performing an important function for restoring information of the OFDM signal on the condition of low signal-to-noise ratio, etc.
Owner:PLA STRATEGIC SUPPORT FORCE INFORMATION ENG UNIV PLA SSF IEU

Method for estimating frequency modulation rate of linear frequency modulation signal

The invention discloses a method for estimating the frequency modulation rate of a linear frequency modulation signal, which comprises the following steps of: 1, performing discrete polynomial transformation on a received multi-component linear frequency modulation signal to obtain a mixed signal m(t) of a complex sinusoidal signal containing frequency modulation rate information and the linear frequency modulation signal; 2, constructing a Hankel matrix for the mixed signal, and then separating a complex sinusoidal signal through singular value decomposition; and 3, carrying out cycle estimation on the complex sinusoidal signal, then carrying out whole-cycle truncation, carrying out discrete Fourier transform to obtain the frequency, and finally obtaining the frequency modulation rate of each component. According to the method, each frequency modulation rate of the multi-component linear frequency modulation signal can be accurately estimated, and compared with an existing estimation method for the frequency modulation rate of the multi-component linear frequency modulation signal, the method has the advantage that the signal-to-noise ratio threshold can be reduced while the small calculation complexity is kept. The method is suitable for a multi-component scene containing strong noise.
Owner:HARBIN ENG UNIV
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