55results about How to "Estimated range is large" patented technology

A joint estimation method of timing frequency offset of satellite borne automatic identification system (AIS) signals comprises that an antenna receives radio frequency signals sent by a ground ship AIS and inputs the radio frequency signals to a receiver; the receiver demodulates the received radio frequency signals into baseband signals and inputs the baseband signals to a field-programmable gate array (FPGA) data collection module; the FPGA data collection module carries out analog-digital conversion of the received baseband signals and obtains digital baseband signals and transmits the digital baseband signals to a signal processing module; the signal processing module processes the received digital baseband signals and obtains accurate AIS ship information and transmits the accurate ship information to a data storage module; and the data storage module stores the received AIS ship information. The joint estimation method of the timing frequency offset of the satellite borne AIS signals has the advantages of eliminating the problem of poor estimation precision in an easy timing estimation working mode by introducing an autocorrelation operation and a weighting multiplication operation, confirming sampling sites by utilizing a timing estimated value, and achieving the frequency offset estimation of being largest in estimation range and smallest in estimation variance on the satellite borne AIS signals by using the autocorrelation operation, a maximum likelihood operation and signal drop sampling.

The invention discloses an adaptive free space optical communication (FSO)-orthogonal frequency division multiplexing (OFDM) transmission system. The transmission system comprises an adaptive orthogonal frequency division multiplexing (AOFDM) transmission part, an optical up-conversion module, an optical down-conversion module and an AOFDM receiving part which are sequentially connected. An adaptive FSO-OFDM transmission method of the invention has the advantages of expanding a carrier deviation estimation range and simultaneously solving problems on the estimation of carrier deviations underthe condition of inconsistency of each carrier deviation caused by the frequency-selective fading characteristic of an atmosphere channel by adopting a high-order cumulant-based carrier blind-synchronization algorithm, providing an effective way for improving a transmission rate and reducing the bit error rate of the system for free space optical communication by realizing the modeling of the optimal adaptive FSO-OFDM transmission system with maximum transmission capacity, and providing novel methods and theoretical bases for further improving the transmission efficiency of the adaptive system and improving system performance by adopting high-order cumulant-based blind channel estimation and blind signal detection technology.

The invention discloses a satellite-borne AIS signal serial separation method based on parameter estimation. The method comprises the steps that a cross-correlation algorithm is used for conducting time delay and frequency offset combined estimation on mixed satellite-borne AIS baseband signals, and the signals are corrected according to an estimation result; incoherent detection and CRC verification are conducted on the corrected signals to obtain a correct sequence, parameter estimation under data assistance is conducted by using the sequence to obtain amplitude information and phase information of the mixed signals; number re-modulation is conducted on the detected code element sequence by using delay, frequency offset, phase and amplitude which are obtained through estimation to construct one route of modulation signal, the route of constructed signal is subtracted from the mixed signals, and then separation of one route of signal is realized; repeated separation is conducted on the rest of the mixed signals, and then serial separation of the mixed signals is realized. The satellite-borne AIS signal serial separation method based on parameter estimation solves the problem that in a satellite-borne AIS system, correct detection is hard to realize due to aliasing caused by slot collision which is generated when the receiving end of a satellite receives signals.

The invention discloses an SOQPSK carrier synchronization method based on pilot frequency and coding joint aiding. The SOQPSK carrier synchronization method based on pilot frequency and coding joint aiding mainly solves the problems that with an existing technology, the estimation complexity is high and the estimation range is small. The SOQPSK carrier synchronization method based on pilot frequency and coding joint aiding includes the implementation steps that first, rough estimation parameters and fine estimation parameters are determined; second, rough estimation is performed through the rough estimation parameters to obtain the rough estimation value f<co> of frequency offset and the rough estimation value fai<co> of phase offset; third, fine estimation is performed through the fine estimation parameters to obtain the fine estimation value f<in> of frequency offset and the fine estimation value fai<in> of phase offset; fourth, the final estimation value f=f<co>+f<in> of frequency offset is obtained through the rough estimation value f<co> of frequency offset and the fine estimation value f<in> of frequency offset; fifth, the final estimation value fai=fai<co>+fai<in> of phase offset is obtained through the rough estimation value fai<co> of phase offset and the fine estimation value fai<in> of phase offset. Through the method, the estimation normalized frequency offset range can be widened to the range from -0.5 to 0.5, the estimation complexity is low, and the SOQPSK carrier synchronization method based on pilot frequency and coding joint aiding can be used for carrier synchronization and wireless channel estimation of a wireless communication system.

The invention discloses an integer frequency bias estimation and fine synchronization method of a receiver and discloses a device thereof, for processing integer frequency bias estimation on the received signals of different frame head sequence modes and carrier frequency bias. The method comprises that: (1) a receiver first processes synchronous capture on the received signals, to attain the coarse synchronization positions and the frame head modes of the received signals; (2) the receiver processes decimal frequency bias estimation on the received signals and then processes decimal frequency bias compensation on the received signals; (3) the receiver attains the real phase of the pseudo random sequence of the frame head with the frame head mode having phase rotation; (4) according to the coarse synchronization position, the frame head mode and the phase of the frame of the received signals, the receiver processes integer frequency bias estimation on the received signals after the decimal frequency bias compensation. The invention can realize integer frequency bias estimation on the receiver of a DTMB system, having better estimation performance and large estimation range.

The invention is a self-correlation carrier frequency deviation estimation algorithm based on known serial correlation and the implementation device thereof, belonging to the field of digital information transmission technology. The algorithm comprises: coherent demodulating the original receiving sequence to get a coherent demodulation receiving sequence by emitted known sequence; self-correlation calculating the coherent demodulation receiving sequence to get a self-correlation sequence; phase angle calculating the self-correlation sequence to get original self-correlation phase angle sequence; differentiating, modular operating and summarizing the original self-correlation phase angle to get a new self-correlation phase angle sequence; and calculating carrier frequency deviation estimation according to the new self-correlation phase angle sequence and original self-correlation phase angle result. By introducing phase angle differentiation, modular operation and summarization, the invention eliminates the phase angle blurring problem in simple frequency deviation estimation algorithm, realizes linear frequency deviation estimation having maximal estimated scope and minimum variance; the invention also further lowers the linear frequency deviation estimation of estimated variance when maximizes the estimated scope.

The invention discloses a satellite-borne AIS signal differential detection implementation method under frequency deviation compensation. The method comprises the following steps: according to intermediate frequency digital signals obtained through front-end processing of a satellite-borne AIS receiver, estimating Doppler frequency deviation of a received signal by utilizing a waveform matching method; on the basis of the estimated Doppler frequency deviation, enabling the intermediate frequency digital signals to pass through a delay differential detector under the frequency deviation compensation to conduct decoding, and realizing delay differential detection of AIS signals when the Doppler frequency deviation is larger. According to the method, the problem that under the condition that the Doppler frequency deviation of the satellite-borne AIS received signal is larger, the differential detection decoding is hard to realize is solved.

The invention discloses a parameter estimation range expansion method of a sea clutter Pareto distribution model. The method mainly solves the problem of effective estimation range limitation during the sea clutter shape parameter estimation in the prior art, and uses the realization scheme of 1, building a Pareto distribution model f<N>(z) of the sea clutters according to the composite model theory of the sea clutters; 2, using the Pareto distribution possibility density function of the sea clutters in N times of observation to deduce the r-odor origin matrix estimation expression <z<r>> of the practical observation value z of the sea clutters; 3, enlarging the value range of the r to the negative number range; estimating the sea clutter shape parameter alpha to obtain the estimated expression of the alpha; 4, when the observation times N is greater than 2, estimating the Pareto distribution parameter of the shape parameter in the range that alpha is an element of a set from 0 to positive infinity. The parameter estimation range expansion method has the advantages that the shape estimation range of the sea clutters is effectively enlarged; the estimation efficiency is improved; the method can be used for target detection.

The invention relates to a digital signal adaptive code rate estimation method and device based on multi-wavelet basis combination. The method comprises two steps of preprocessing and adaptive code rate estimation. In the preprocessing step, original I/Q data of an observation window is used as input, and a bandwidth rough estimation result and baseband I/Q data in a specified oversampling range are output through fast Fourier transform, frequency estimation, bandwidth rough estimation, down-conversion and down-sampling processing; in the adaptive code rate estimation step, the wavelet transform scale is adaptively selected according to a bandwidth rough estimation result, wavelet transform is carried out on the baseband I/Q data, jump information after transform is extracted, and finally,the code rate of a digital signal and a wavelet basis for signal acquisition are output through adaptive decision. According to the method, the problems of single wavelet basis application range andlow estimation precision of the traditional wavelet transform-based digital signal code rate estimation are solved, the accuracy of the digital communication system code rate estimation under the non-cooperative condition is improved, and the method can be applied to the fields of spectrum monitoring, electromagnetic reconnaissance and the like.

The invention discloses an estimation method of integral multiple subcarrier frequency offset of a robust. In the method, by means of a known frequency domain training sequence in an orthogonal frequency division multiplexing (OFDM) system and the cross-correlation characteristic between a received signal and a known ideal signal, a channel frequency domain response is obtained by descrambling; and after time frequency domain conversion, an offset value of the integral multiple carrier frequency offset is judged according to the amplitude value of the obtained channel time domain pulse response. The estimation method can realize full multiplexing of a fast Fourier transform (FFT) module in the OFDM system and is slightly affected by multi-path channel attenuation; and the estimation method has the characteristics of simple implementation, high judgment accuracy and the like, thus being applicable to any OFDM communication system with the training sequence.

The invention discloses a frequency offset estimation method based on adjustability of data-aided accuracy. According to the method, by calculating angle difference values of x adjacent R functions, a frequency offset value is estimated, wherein the R functions are functions which are calculated by a receiver according to a received symbol sequence and carry angle deflection angles. Formulas of calculating the frequency offset value are that: (with reference to the specification), and x is smaller than or equal to N-1 and greater than or equal to 2 and is an even number; (with reference to the specification), and x is smaller than or equal to N-1 and greater than or equal to 3 and is an odd number; and m is smaller than or equal to N and greater than or equal to 1, and N is a positive integer not greater than L-1. Under the flat fading channel condition, the method has higher accuracy than an M&M algorithm and has a wider estimation range than an L&R algorithm and a Fitz algorithm.

This invention relates to one cross multiplex signal frequency bias estimation method based on rapid Fourier exchange in wireless local zone system, which comprises the following steps: a, wireless local network system base band receives time simultaneous data sequence through proper exchange and sending the exchange data into Fourier exchange; b, researching the exchanged data from Fourier to get rough bias estimation of frequency to compensate data; c, processing accurate bias frequency estimating on compensated data.

The invention discloses a decimal frequency bias estimation method of a receiver and a relative device, for processing decimal frequency bias estimation on the received signals with different frame head sequence modes and carrier frequency bias. The method comprises: (1) setting all frame head sequence modes into a same structure as N+L+N, setting delta B=F/N+L, wherein F is the base band sampling rate of the system; (2) receiving the received signals with carrier frequency bias, synchronously capturing the received signals to attain the frame head sequence mode of the received signals, and selecting corresponding N and L according to the frame head sequence mode; (3) according to the selected N and L, processing sliding auto correlation on the received signals to attain the output result of the sliding auto correlation; (4) according to the output result of the sliding auto correlation, estimating decimal frequency bias. The inventive decimal frequency bias estimation has the advantages of wide application and high estimation effect.

The invention belongs to the technical field of communication, and relates to a multilevel frequency offset estimation method based on FFT. The method provided by the invention mainly comprises the following steps: setting carrier frequency offset estimation to multiple frequency offset estimation levels, which is characterized in that a lower extraction ratio corresponding to the frequency offset estimation increases with the increase of the frequency offset estimation levels; carrying out the frequency offset estimation starting from the first level frequency offset estimation, and calculating the frequency offset estimation result of each level before the frequency offset estimation level reaches a preset total level; and accumulating the frequency offset estimation result of each level, and using the obtained accumulated value as a final frequency offset estimation result. The multilevel frequency offset estimation method provided by the invention has the beneficial effects that compared with the traditional frequency offset estimation method based on the FFT, on the basis of guaranteeing the estimation range, the frequency offset estimation precision can be greatly improved.

The invention is concerned with the symbol timing migration method in the radio communications system, which the method includes: to confirm the channel frequency response of the opposite known pilot frequency point of each of the received symbol; to conduct combining to each of the symbol to form the perfect pilot frequency; to complete combination of each of the symbol and to obtain the timing migration value of the symbol by using the channel frequency response value constructs the frequency response of the channel.

The invention discloses a BPSK signal-to-noise ratio calculation design method based on an FPGA ARM. The method comprises the following steps: step 1, data sampling transmission: acquiring a BPSK sampling signal from an information source through a matched filter, preprocessing the BPSK sampling signal, acquiring virtual and real data in the signal power of the BPSK sampling signal according to phase offset, and transmitting the virtual and real data to an accumulation calculation module for processing; and step 2, accumulation calculation: accumulating virtual and real data after signal square processing is carried out through an accumulation calculation module. According to the method, the phase modulation in the signal is removed by utilizing the quadratic method, so that data assistance is not needed any more; the in-phase channel and the orthogonal channel are respectively processed, and the phase offset influence of the demodulation carrier is processed according to a well combination estimation result; grouping estimation is directly carried out on the sample values obtained after analog-to-digital conversion, symbol synchronization is not needed, the estimation range is wide, and the BPSK signal-to-noise ratio calculation design method based on the FPGA ARM is low in complexity and high in calculation precision.

The invention relates to a steep terrain orientation angle estimation method based on a fully-polarized SAR. The method comprises the steps that an orientation angle without a certain reference axis of a steep terrain is calculated according to fully-polarized synthetic aperture radar (SAR) data, self-adaptive expansion selection parameters are determined, the orientation angle without the certainreference axis is expanded to be an included angle between the steep terrain and a vertical polarization axis v, and therefore a correct estimation value of the orientation angle of the steep terrainis acquired. The invention furthermore provides a steep terrain orientation angle estimation system based on the fully-polarized SAR. The system comprises a coherence matrix acquisition module, a parameter calculation module, a calculation module of the orientation angle without the certain reference axis, a self-adaptive expansion selection parameter calculation module and a steep terrain orientation angle estimation module. According to the fully-polarized SAR data, a compressed polarization orientation angle of a target without the certain reference axis is calculated, the reference axis of the orientation angle is determined and expanded, the estimation range of the orientation angle is effectively expanded, and the purpose of accurately estimating the orientation angle of the steep terrain is achieved.