38 results about "Doppler rate" patented technology

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.

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.

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.

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 invention belongs to the technical field of wireless communication, and discloses a method for real-time communication of hypersonic aircraft large dynamic Doppler scene, including: at the sending end, precoding the sending signal, inserting pilot data before sending; at the receiving end, extracting Pilot data, on the one hand, use the pilot information to roughly capture the Doppler frequency offset and Doppler primary rate of change, and on the other hand, use the pilot information to estimate the channel state information; in terms of capture, the method based on FFT parallel segmentation is used to complete fast and rough capture ; After the Doppler frequency offset and the Doppler change rate are roughly captured, the received data is manually moved, and the channel state information is estimated to perform diversity combining. The invention can meet the requirements of real-time telemetry communication of the hypersonic aircraft, has the characteristics of short time consumption and low complexity, and is of great significance to the real-time communication of the hypersonic aircraft.

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 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 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.

The invention discloses a spread spectrum signal accurate acquisition system, which has good real-time processing performance, small frequency measurement error, high estimation accuracy and low adaptive signal-to-noise ratio. The present invention is realized through the following technical solutions: the sampling cache module performs down-sampling processing on the received signal, and controls the ping-pong reading and writing of the sampling data; The frequency compensation of the Doppler frequency shift and the phase correction of the Doppler frequency shift of the pseudo-code; the parallel search of the phase of the pseudo-code is realized by using double-block expansion technology and fast Fourier transform; Double measurement of full coherent integration and carrier Doppler frequency shift and its rate of change; use the method of comparison and search for all integral processing data to obtain the relevant information of the integral peak, and calculate the accurate starting phase of the pseudo code and the multiplicity of the pseudo code of the spread spectrum signal. Doppler shift, Carrier Doppler shift, and Carrier Doppler rate of change.

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.