38 results about "Doppler rate" patented technology

Described is a method for compensation of an OFDM signal propagating through Doppler-distorted, time-varying multipath channels. The method is based on low-complexity post-FFT signal processing. Minimum mean square error combining of signals is performed for signals received at spatially-distributed receiver elements using adaptive channel estimation and phase tracking. Doppler shifts are modeled as a consequence of motion-induced time compression and dilation. The Doppler rate is assumed constant over one OFDM block but can vary between OFDM blocks. Thus a non-constant Doppler shift is accommodated by the method. Non-uniform Doppler compensation across subchannels is based on adaptive estimation and prediction of the Doppler rate. A single adaptively estimated parameter is used to track the phases of all the carriers and channel estimates are updated on a block by block basis.

The invention discloses a bistatic forward-looking synthetic aperture radar ground moving target detecting method and imaging method. The detecting method includes the steps of firstly, utilizing Bulk-Deramp filtering to eliminate Doppler blurs and reducing space variations of the Doppler rate; secondly, utilizing first-order Keystone conversion to complete range migration correction of a static target and a ground moving target; then, utilizing extended orientation nonlinear frequency modulation and frequency scaling operation to equilibrate the Doppler rate of the static target; meanwhile, enabling the Doppler rate of the ground moving target to be different from the Doppler rate of the static target; finally, building a second-order fuzzy function product, completing detection on the ground moving target and estimating the Doppler rate of the ground moving target. The problem that the moving target and the static target are hard to distinguish when BFSAR is under a background with strong clutter is solved. According to the imaging method, after the detection on the ground moving target is completed, an echo of the moving target is focused by using the estimated Doppler rate of the ground moving target, and then imaging the ground moving target is completed.

A system and method for determining timing offset errors in a low earth orbit satellite system based upon Doppler and Doppler rate of change is provided. A user terminal determines first and second timing offsets respectively associated with first and second satellite beams from respective first and second satellites. Next, the user terminal determines the Doppler and Doppler rate of change associated with the first and second satellite beams. A timing offset is estimated from the measured Doppler and Doppler rate of change and is then compared with the user terminal's own determined timing offset. If the comparison does not produce a value within a predetermined threshold, a beam identification error is declared.

The invention belongs to the technical filed of radar and discloses an unmanned aerial vehicle synthetic aperture radar imaging range-dependant map drift method, improving the estimation precision of doppler rate. The range-dependant map drift method includes receiving the echo signal in the set time period, and performing coarse compensation, distance unit migration correction and distance matching filtering in order to obtain coarse image data; segmenting the coarse image data in the azimuth direction to obtain N sub-aperture data blocks; azimuthally de-skewing the sub-aperture data blocks, dividing the sub-aperture data blocks into L distance units, and estimating the second order phase error of each sub-aperture data block; solving the phase error function corresponding to each distance unit in each sub-aperture data block and compensating the residual phase error compensation for the corresponding distance unit; and azimuthally compressing the data after residual phase error compensation to obtain the focused SAR image.

The invention belongs to the technical field of radar real-time imaging processing, and particularly relates to an SAR real-time imaging processing method based on an FPGA and multiple DSPs. The processing method includes the following steps that echo data are pre-processed by means of an FPGA chip, so that subaperture data are obtained; the subaperture data are sent to the first DSP sequentially by means of the FPGA chip and are alternately forwarded to the third DSP, the fourth DSP and the seventh DSP by means of the FPGA chip for Doppler center estimation, range migration correction, Doppler rate estimation and motion parameter estimation, and the processed data are forwarded to the eighth DSP sequentially through the first DSP; each subaperture datum is divided into three blocks in the range direction through the eighth DSP and the three blocks of each subaperture datum are sent to the second DSP, the fifth DSP and the sixth DSP respectively for motion parameter fitting, phase compensation, direction pulse pressure and multiview processing, so that corresponding blocked image data are obtained; the blocked image data are transmitted to the eighth DSP for image quantization and image splicing processing, and ultimately an SAP image is obtained.

The invention relates to a method for accurately estimating the Doppler rate in a large-strabismus SAR imaging mode. The method comprises the steps that 100) distance walk compensation, distance bending correction and secondary distance compression are implemented on echo data to obtain a double-time-domain signal which is compressed in the distance direction; 101) a dechirp processing is implemented on the distance compressed data in an orientation time domain by utilizing a reference function Sdechirp(t); 102) FFT (Fast Fourier Transform) is implemented on the orientation direction data to change the data from the orientation time domain to an orientation frequency domain; 103) a special display point is selected from each distance door in a maximal energy method, the orientation-direction position of the point is estimated, and a compensation function Scomp(t) of each special display point is calculated according to the orientation-direction position; 104) windowing is implemented, data within the main fuzzy width of the special display point selected from each distance door is reserved, and data which has no contribution to estimation of the Doppler rate is abandoned; 105) reverse Fourier transformer is implemented, and space change phase is compensated in the orientation time domain; and 106) the Doppler rate is estimated in a classic MD algorithm.

The invention provides a dual-station SAR receiver kinematic error compensating method based on navigation satellite signals. The method includes the steps of establishing a Doppler rate and kinematicerror relation model, estimating and compensating for receiver method planar kinematic errors, and estimating and compensating for receiver cruise direction kinematic errors. The method has the advantages that according to the structural characteristics of a dual-station SAR based on the navigation satellite signals, the method based on the instantaneous Doppler rate is put forward to correct thekinematic errors of a receiving platform; the real model of three-dimensional movement errors is sufficiently considered in the method, and the kinematic error estimating and compensating can be effectively conducted; no interpolation or iteration treatment needs to be conducted in the method, the processing efficiency is high, and a good imaging result is obtained.

A method for real-time communication of large dynamic Doppler scene of hypersonic aircraft includes steps of: at the sending end, pre-coding a transmitting signal, inserting pilot data and sending; atthat receive end, extracting pilot data; on the one hand, coarsely capturing doppler frequency offset and doppler primary change rate by using pilot information; on the other hand, estimating channelstate information by using pilot information; in the aspect of acquisition, by using the method of fft-based parallel segmentation, accomplishing fast and coarse acquisition; after coarse acquisitionof doppler frequency offset and doppler rate of change, manually shifting the received data, and estimating channel state information and merging diversity. The invention can meet the requirements ofreal-time telemetry communication of a hypersonic aircraft, has the characteristics of short time consumption and low complexity, and has important significance for the real-time communication of thehypersonic aircraft.

The invention relates to a filtering method of a ground expressway target of an onboard warning radar, belongs to the radar technology field and particularly to the filtering method of the onboard expressway target of the onboard warning radar based on Doppler characters. The filtering method of the onboard expressway target of the onboard warning radar solves a technical problem of exactly identifying flight paths of the ground expressway target and an aerial target which are generated by the onboard warning radar to filter ground targets which interfere with the flight paths. The filtering method of the onboard expressway target of the onboard warning radar comprises Doppler speed and positive and negative of the Doppler rate mainly according to Doppler character differences of the ground expressway target and the aerial target and enables target classification criterion to be designed according to distance distribution difference of the ground expressway target and the aerial target to achieve exact identification and classification of the ground expressway target and the aerial target. The filtering method of the onboard expressway target of the onboard warning radar has the advantages of being high in identification rate of the ground target and the areal target, accordingly good in filtering of the ground target and capable of being applied to optimization of a target flight path of the onboard warning radar.

The invention provides a fast capturing method of a high-dynamic weak L1CP signal. The technical scheme comprises following steps: a step S1 of using a receiver to receive a satellite signal, carryingout down-conversion, sampling and demodulation on the received satellite signal to obtain a baseband signal; a step S2 of generating a local code sequence of the receiver; a step S3 of determining aparameter; a step S4 of segmented correlation on the baseband signal and a local pseudo code in the frequency domain; a step S5 of estimating a Doppler value and a Doppler rate-of-change value; and astep S6 of capturing a decision. By means of segmented correlation, a receipt signal is compensated through the estimated Doppler value and the estimated Doppler rate-of-change value, coherent loss brought by high dynamics can be effectively reduced, and the capturing performance is greatly improved.

The invention, which belongs to the field of signal processing, claims for protection of a PMF-FRFT acquisition algorithm for BOC signals in a highly dynamic environment. Discrete polynomial phase transform is carried out on a received high dynamic signal to carry out order determination and if the received signal contains a Doppler secondary change rate, order reduction is carried out and then aPMF-FRFT algorithm is used; and if the received signal only contains a Doppler primary change rate, the PMF-FRFT algorithm is used directly. Since the partial matching filtering is a low-pass filtering process, the received signal is multiplied by a combined spreading code and then PMF processing is carried out to realize speed reduction; FRFT processing is carried out on the data after speed reduction to find out an optimal order number; and an obvious peak occurs under the optimal order number and when the spectrum peek exceeds the threshold, the capturing success is realized. The experiments show that the problem that the BOC signal with the Doppler rate can not be captured by the traditional method is solved by the PMF-FRFT algorithm. On the basis of the study on the BOC signals in a highly dynamic environment, the algorithm has the important significance in capturing signals in actual application.

A method for estimating the position of a terminal in a satellite communication at either the ground station or in the satellite is described. The method uses estimates of the time delay, Doppler and / or Doppler Rate of signals transmitted from the terminal to the satellite together with an estimate of the satellite position. The method can be used with both synchronised terminals and unsynchronised terminals provided they have a stable time or frequency reference as well as with low earth orbit satellites both with and without on-board global position and timing references. Additionally the method can also use estimates of the time delay, Doppler or Doppler rate of beacon signals received by either the satellite or terminals. These beacon signals may include GPS L1 signals. In contrast to standard GPS receivers, the method does not require the terminal to store GPS ephemeris data or to operate continuously.

The present invention proposes a method capable of effectively tracking Doppler frequency change rate signals with extremely low signal-to-noise ratio, aiming to provide a method that can more accurately and effectively track extremely low SNR Doppler frequency change rate signals in deep space measurement and control. Technical methods for measuring and controlling signals. The present invention is realized through the following technical solutions: the measurement and control receiver obtains the received signal through A / D sampling, and locks and tracks through the ultra-narrowband third-order phase-locked loop in the mathematical model of the phase-locked loop, and extracts the signal Doppler from the loop. Le, the received signal enters the intermediate frequency ultra-narrowband digital phase-locked loop, and the Doppler frequency and Doppler change rate are sent to the third-order phase-locked loop, and then the ultra-narrowband phase-locked loop and the digital third-order phase-locked loop are used to Narrowband carrier loop to track deep space measurement and control signals with extremely low signal-to-noise ratio and Doppler frequency change rate. The invention combines extremely narrow carrier loop bandwidth and digital third-order phase-locked loop to effectively solve the problem of tracking the measurement and control signal by the download wave loop under the condition of multiplier frequency change rate when the signal-to-noise ratio of the received signal is very low.

The invention belongs to the technical field of wireless communication, and discloses a hypersonic flight vehicle large dynamic Doppler rapid capture method and a communication system, and the methodcomprises the steps: employing a blind rapid estimation algorithm to carry out the rapid estimation of the Doppler rate of a received signal; compensating the received signal by using the estimated Doppler rate, performing Fourier transform on the compensated received signal on a plurality of continuous symbols, and then performing square cumulative average on Fourier transform results of the plurality of symbols; and finally, carrying out peak value search on the accumulation result, wherein the maximum peak value is the captured Doppler frequency offset value, and the Doppler rate of the received signal is obtained through a blind estimation algorithm. The Doppler search range correction link based on flight condition estimation limits spectral peak search within a smaller range so as tofurther improve the capture precision and capture speed of carrier signals. According to the invention, the carrier signal capture probability and capture speed are improved, and the method can be applied to rapid / real-time measurement and control communication of hypersonic aircrafts.

The embodiment of the invention provides an incoherent joint capture method and device, and the method comprises the steps: dividing an input signal into M groups of sub-input signals, carrying out the FFT conversion of the sub-input signals, and carrying out the circumferential shift of the M groups of FFT sequences; carrying out full-coherence accumulation on M groups of circumference correlation results of the subcarriers to obtain an output plane of the coherence accumulation results, and replacing the frequency offset dimension of the output plane with a Doppler rate dimension; accumulating coherence of doppler rate-code phase two-dimensional plane of all subcarriers; and comparing each peak value on the statistical plane with a preset monitoring threshold to obtain a correlation peakexceeding the monitoring threshold; and according to the Doppler factor and the code phases of the correlation peaks on the Doppler rate-code phase two-dimensional planes of the subcarriers, respectively obtaining the frequency offset value and the propagation delay of the subcarrier. According to the embodiment of the invention, the total spread spectrum gain distributed on each subcarrier is fully utilized, and the signal-to-noise ratio performance of the capturing system is improved on the basis of not increasing the algorithm complexity.

The invention discloses a micro vessel examination and identification system and method. The system comprises a multifrequency ultrasound angiography probe, a multiplexer, a T / R conversion switch, a user-controlled input system, an adjustable pulse transmitter, an echo receiver, a time gain compensation unit, an AD converter, a beam synthesis unit, a signal processing unit, an image processing unit, a blood vessel examination and identification system and a display system. According to the micro vessel examination and recognition system, the high frequency ultrasound probe is adopted for detecting microvessels, the multifrequency detection probe and an ultra-fast composite Doppler imaging technology are adopted, very low velocity microvessel detection can be achieved without a contrast agent, different working frequencies and working modes are selected according to different detection areas and different degrees of imaging resolution / speed sensitivity, and the functions of dynamic Doppler rate review and three-dimensional reconstruction of vascular microstructures are achieved; doctors can observe and evaluate repeatedly conveniently, and doctors are helped to diagnose.

The invention discloses a precise focusing method for high-resolution scanning synthetic aperture radar (ScanSAR). The method comprises the steps that two-dimensional sub-aperture segmentation is carried out on ScanSAR data of each sub surveying and mapping zone, and Doppler rate error (DRE) estimation is carried out on each two-dimensional sub-aperture; range-dependent DRE estimation is carried out on ScanSAR data of a whole surveying and mapping zone; azimuth error estimation is carried out on the ScanSAR data obtained after the range-dependent DRE estimation is carried out; full aperture phase error correction and azimuth compression are carried out on the ScanSAR data of each sub surveying and mapping zone. The invention further discloses a precise focusing device for the high-resolution ScanSAR.

A method for reconstituting a signal due to a flow distortion in a mud-pulse telemetry system, having steps of obtaining at least one parameter to be transmitted by a transmitter to a receiver through the mud-pulse telemetry system, estimating a change in a flow rate in a borehole fluid along a trajectory of the mud-pulse telemetry system undergoing a fluid distortion, estimating a Doppler rate of the signal traveling through the borehole fluid along the trajectory of the mud-pulse telemetry system, calculating a Doppler compensation value for the signal sent along the trajectory in the borehole fluid, transmitting the signal of the at least one parameter through the mud-pulse telemetry system, receiving a portion of the signal of the at least one parameter and reconstituting at least a portion of the signal using the Doppler compensation value.

A CUDA-based method for fast acquisition of multi-system signal frequencies is characterized in that: based on a high-performance PC, using the CUDA architecture, the fast acquisition of multi-system signal frequencies is realized in a parallel manner; the implementation steps include: setting Doppler and multi-system Segmentation of the Puller rate of change, determine the number of thread blocks of each GPU kernel function and the number of threads in each thread block, read the signal data into the global storage space of the GPU card, start the down-conversion and integration modules, and perform parallel FFT operations to The parallel reduction method finds the maximum spectral line and the corresponding Doppler rate of change segment and Doppler segment, and calculates the carrier frequency offset and Doppler rate of change estimate to complete the capture. The invention makes the signal frequency fast capture algorithm conform to the CUDA framework and the working characteristics of the GPU, can give full play to the parallel computing capability of the GPU, is suitable for signals of various systems, effectively improves the capture speed and is easy to implement.

The invention discloses a method for accurately estimating the carrier frequency of a high-dynamic PCM / FM signal, and aims to provide an estimation method with high carrier frequency estimation accuracy and small measurement error. The present invention is realized through the following technical solutions: a PCM / FM signal frequency measurement system is composed of a filter sampling module, a frequency modulation frequency positive and negative compensation parallel branch, a peak search module, and a frequency calculation module; the high dynamic PCM / FM signal passes through a band After passing through the filter module, the arbitrary down-sampling process is completed, and the down-sampled data enters the frequency modulation frequency positive and negative compensation parallel branch respectively; the sampling data is sequentially subjected to frequency modulation frequency pre-compensation, carrier Doppler change rate compensation, and mode control to complete carrier recovery; After FFT frequency measurement and non-coherent integration and accumulation, the peak search module finds the largest peak value and the corresponding change rate sub-slot in the integration result; the frequency calculation module estimates the carrier Doppler of the high dynamic PCM / FM signal according to the peak value result Le frequency shift, carrier Doppler rate of change, search time and other information.

The invention relates to a method for accurately estimating the Doppler rate in a large-strabismus SAR imaging mode. The method comprises the steps that 100) distance walk compensation, distance bending correction and secondary distance compression are implemented on echo data to obtain a double-time-domain signal which is compressed in the distance direction; 101) a dechirp processing is implemented on the distance compressed data in an orientation time domain by utilizing a reference function Sdechirp(t); 102) FFT (Fast Fourier Transform) is implemented on the orientation direction data to change the data from the orientation time domain to an orientation frequency domain; 103) a special display point is selected from each distance door in a maximal energy method, the orientation-direction position of the point is estimated, and a compensation function Scomp(t) of each special display point is calculated according to the orientation-direction position; 104) windowing is implemented, data within the main fuzzy width of the special display point selected from each distance door is reserved, and data which has no contribution to estimation of the Doppler rate is abandoned; 105) reverse Fourier transformer is implemented, and space change phase is compensated in the orientation time domain; and 106) the Doppler rate is estimated in a classic MD algorithm.