39results about How to "Improve Frequency Estimation Accuracy" patented technology

The invention discloses a joint estimation method for synchronizing frames, frequencies and fine symbols for orthogonal frequency division multiplexing (OFDM). The method comprises the following steps: carrying out autocorrelation operations of small point length and big point length on base band data sequences at the receiving terminal in parallel; jointly determining the frame synchronization position in real time and in parallel according to the small point autocorrelation peak and the big point autocorrelation peak; computing integer frequency offset coarse estimation value and decimal fraction frequency offset coarse estimation value according to the small point autocorrelation peak and the big point autocorrelation peak; estimating the final frequency offset detection value from the integer frequency offset coarse estimation value and the decimal fraction frequency offset coarse estimation value with a frequency offset dereferencing decision device; carrying out frequency offset correction on the base band data sequences according to the estimated final frequency offset detection value; and carrying out cross-correlation on the corrected base band data sequences and the local data sequences and determining the accurate fine symbol synchronization position through the cross-correlation peak. The contradiction of complex system measure function hardware design in the traditional time-domain joint estimation systems is solved by using the method.

The invention provides a synchronous phasor measurement method based on a self-adoption variable window, which is used for the field of a synchronous phase measurement of a power system. When being variable, a signal frequency is measured in real time, and the signal frequency in the next sampling time is estimated. The method used by the invention is used for keeping a sampling frequency unchanged rather than adjusting the sampling frequency fs. A data length N belonging to current calculation can be automatically adjusted according to an estimation frequency, so as to keep N*Ts=T (Ts=1/fs is a fixed sampling period, fs is the sampling frequency, T=1/f is an actual signal period value, and f is a signal frequency). Thus, the error compensation precision is improved; the frequency estimation precision is greatly improved. The synchronous phasor measurement method provided by the invention is applicable to synchronous phasor measurement calculation and frequency calculation correction in a ship power system.

The invention relates to the field of digital wireless communication and discloses a frequency shift estimation method and system for coherent demodulation frequency shift keying modulating signals. According to the method and the system, prefix signals of GFSK (Gaussian Frequency Shift Keying)/FSK (Frequency Shift Keying) signals are designed to a string of fixed-length codes with altering 0 and 1, and according to the prefix signals, an ideal receiving signal c(i) can be completely eliminated from an x(i) under the condition that a receiver does not need to copy the ideal receiving signal c(i), thereby solving the problem that as the frequency modulation index of the GFSK/FSK signal can not be obtained accurately and can change along with time and temperatures, a receiving terminal can not accurately copy the ideal receiving signal c(i), so as to improve the accuracy of the frequency shift evaluation. Therefore, by virtue of the iteration-combination of frequency evaluation results of R(N), R(2N),..., R (KN), the phase ambiguousness caused by the large frequency shift can be eliminated, and the precision of the frequency shift evaluation can be improved further.

The invention discloses a power frequency sinusoidal AC electrical signal zero-crossing time detection system and method thereof, relating to the time detection technology in the electrical signal measurement field. The system is characterized in that a power frequency sinusoidal AC signal source (100), an AD sampling circuit (210), a logic-to-logic circuit (221), and a pulse drive circuit (240) are successively connected; and a pulse generating circuit (230) and acontroller (222) are connected to a logic and calculation circuit (221). The method includes (1) initialization, (2) frequency parameter estimation; (3) phase parameter estimation; and (4) zero-crossing time reckoning and output. The power frequency sinusoidal AC electrical signal zero-crossing time detection system and method can effectively detect the zero-crossing time of the power frequency AC analog electrical signal; and controls the error within 1micron second, can be used for the minimal phase error measurement between the analog and digital signals, and facilitates the value traceability of phase accuracy.

The invention belongs to the field of digital signal processing, and provides a low-rate end frequency estimation method of a rapid convolution adjustable filer group, for realizing the purposes of determining relative positions between an output frequency spectrum and an input frequency on a corresponding filter passband, estimating the frequency of high-rate input signals at a low-rate end, and substantially inhibiting an error diffusion effect. The technical scheme employed by the invention is as follows: the low-rate end frequency estimation method of the rapid convolution adjustable filer group is divided into the following two phases: 1, a rapid convolution phase: step 1, performing overlapping segmentation on input signals x(n); step 2, performing N-point fast Fourier transform (FFT) on each segment; step 3, observing FFT amplitude output corresponding to each sub-band; step 4, performing Lk-point inverse FFT on a result after the sub-band is weighed; and step 5, repeating the previous four steps to obtain P time domain output samples each with a length of L<S,k>; and a frequency spectrum correction phase. The method provided by the invention is mainly applied to digital signal processing.

The invention relates to the technical field of space-air-ground-sea integrated communication, in particular to a low-orbit satellite low-signal-to-noise-ratio high-dynamic burst signal carrier synchronization method. According to the method, burst signal Doppler frequency offset, Doppler frequency offset change rate and carrier phase parameter estimation and correction are realized step by step by adopting a forward structure. The parameter estimation precision of Doppler frequency offset and frequency offset change rate is improved by combining FFT with a quadratic inner difference algorithm; and the phase parameter estimation value of the outburst signal is obtained by using a linear interpolation mode, the estimation precision can obtain higher carrier synchronization under the conditions of high dynamic and low signal-to-noise ratio of a low-orbit satellite, the operation complexity is moderate, and the requirement of engineering application can be met.

The invention relates to a radar micro-Doppler signal extraction method of a rotor unmanned aerial vehicle, belongs to the technical field of target signal detection, and aims to perform time-frequency analysis on echo signals of the rotor unmanned aerial vehicle and improve the operation efficiency. The method comprises the following steps: firstly, carrying out fractional order Fourier transformprocessing on a signal, and then filtering the signal; secondly, performing inverse fractional order Fourier transform, natural logarithm transform and Fourier transform on a processed result to estimate frequency parameters of a micro-Doppler signal; and finally, realizing the detection of the multi-component micro-Doppler signal by using different sampling interval processing methods. The method can greatly reduce impacts on the rotor micro-Doppler frequency from the Doppler frequency of a vehicle body, can complete the quick detection of a plurality of micro-Doppler component signals, andis higher in application value in the classification and recognition of unmanned aerial vehicles.

The invention belongs to the technical field of communication and relates to a multi-tone interference parameter estimation method based on three-order iteration. The method can accurately estimate amulti-tone interference parameter, and comprises firstly cancelling out the mutual interference between multiple tones by first-order iteration and a three-point interpolation formula so as to obtainthe initial estimated value of the multi-tone interference parameter; then according to the initial estimated value, further cancelling out the mutual interference between the multiple tones by second-order iteration and the three-point interpolation formula so as to obtain a new estimated value; and finally, according to the new estimated value, improving the frequency estimation accuracy by third-order iteration and a two-point interpolation formula to obtain a final estimated value. The method can overcome the mutual interference between multiple tones, and obtain a parameter estimated value that approximates a CRLB, reconstructs an interference signal through the frequency domain, avoids repeated DFT operations in an iterative process, is easy to implement, and has a good application value.

The invention claims a short burst carrier frequency offset estimation method, relates to the field of communications and in particular relates to a short burst carrier frequency offset estimation method unique words in a mobile communication system. When a received signal is a short burst signal in the frequency tracking process of a communication receiving end, a short burst frequency offset estimation method comprises the following specific process: firstly, demodulating and decoding the received short burst signal to obtain signal bit information; secondly, re-coding and re-modulating the signal bit information to obtain an estimated received signal; and finally, extracting partial data symbols from the estimated received signal as unique words, and performing carrier frequency offset estimation of the unique words and the unique word information of the received signal, respectively, to obtain a final frequency offset estimated value, and then compensating the frequency of receiving signals by use of a carrier tracking loop. The short burst carrier frequency offset estimation method is capable of reducing the length of the obtained information bits and also improving the frequency estimation accuracy.

The invention discloses an FMCW radar distance and speed joint estimation method based on all-phase Fourier transform, and relates to the technical field of radar signal processing, and provides a three-point frequency deviation estimator based on apFFT in order to solve the problem that in the prior art, an FMCW radar is poor in estimation precision of the target distance and speed. A three-pointfrequency deviation estimator based on apFFT is provided, the frequency deviation of a spectral peak can be estimated from an all-phase frequency spectrum of a signal sequence, and compared with a simple apFFT algorithm, the frequency estimation precision of the signal is improved; interpolation calculation and iterative calculation of an all-phase frequency spectrum are avoided, and the calculation complexity of the algorithm is effectively reduced compared with Li-algorithm; and the detection of the FMCW radar on the target distance and speed depends on the estimation of the intermediate frequency and phase of the echo signal, the estimation precision of the phase of the echo signal is improved by using the apFFT, and the estimation precision of the frequency of the echo signal is improved by using the three-point frequency deviation estimator, so that the estimation precision of the FMCW radar on the target distance and speed is improved.

The present invention provides a high-dynamic fast/precise acquisition method for an NSCC signal. The method comprises a step of performing a Zoom-FFT operation on each subcarrier in an NSCC digital intermediate frequency signal according to a selected frequency band to be analyzed and obtaining refined spectral information, a step of searching for a frequency domain peak point after the Zoom-FFToperation, reading a peak point corresponding frequency, and determining a frequency range to be updated and monitored with the peak point corresponding frequency as a center according to a Doppler dynamic change range, a step of performing a sliding FFT operation on the frequency range to be updated and monitored to accurately estimate the frequency information of each subcarrier of the NSCC in real time in a sliding recursive mode to complete the update/monitoring of each subcarrier peak of the NSCC, a step of carrying out interpolation estimation based on a sinc function by using the peak point and adjacent peak information, and a step of obtaining the real-time precise Doppler shift value of each subcarrier of the NSCC based on an interpolation result to achieve high-dynamic precise acquisition. According to the method, the accurate estimation of the Doppler shift of each carrier of the NSCC during an acquisition phase can be achieved with a small computational cost.

The invention discloses a GNSS-IR height measurement method suitable for a navigation receiver. The method comprises the following steps of: acquiring a satellite in-orbit position coordinate, a signal-to-noise ratio and a user receiver position coordinate by using observation data of a common navigation type GNSS receiver, and calculating a satellite elevation angle and an azimuth angle according to original observed quantity; screening proper satellites according to space-time distribution of an observation scene, and preprocessing a signal-to-noise ratio time sequence by using a moving average method; separating reflection components in a signal-to-noise ratio of each satellite by using a local weighted regression method, performing spectral analysis on the signal-to-noise ratio sequence residual error based on elevation angle reordering, estimating the oscillation frequency of the signal-to-noise ratio of a reflection signal, and calculating the reflection height corresponding to a single satellite according to the oscillation frequency; and optimizing a measurement result of the reflection height through weighting. According to the GNSS-IR height measurement method, the application range is expanded, data resources of the navigation type receiver are fully utilized, the under-fitting problem of a traditional low-order polynomial method can be effectively solved, and the measurement precision and stability are improved.

The invention belongs to the field of space optical communication, and particularly relates to a data recovery and open-loop synchronization method for an optical PPM asynchronous sampling signal based on MPPC detection. The method comprises the following steps: firstly, carrying out fast Fourier transform (FFT) on a PPM asynchronous sampling signal, and then estimating the initial frequency offset and phase offset of the signal by using Quinn, Jacobsen and MacLed algorithms respectively; and performing photon number recovery on the PPM signal by frequency offset and phase offset estimation values through correlation operation, further solving time slot log likelihood ratio sequences corresponding to Quinn, Jacobsen and MacLed algorithms, and finally selecting a sequence with the maximum standard deviation from the three groups of time slot log likelihood ratio sequences as the input of an error correction decoder. The time slot synchronization method provided by the invention has veryhigh synchronization precision under extremely low optical power, is high in operation speed, and has relatively strong robustness compared with a single ratio method; for 64PPM modulation signals, the photon number recovery method provided by the invention only needs to detect 1.2 photons on average in each signal time slot, so that the bit error rate can be less than 1.0 e-4.