33results about How to "Small loss of signal-to-noise ratio" patented technology

The invention discloses a signal detection and judgment method and device in the capture of a weak satellite navigation signal. In a weak-signal environment, a high-sensitivity satellite navigation receiver needs to accumulate correlated results of a pseudo code for a long time so as to meet the sensitivity gain requirement of capture. The invention aims to reduce the SNR (Signal-to-Noise Rate) loss brought from a detection and judgment process of the correlated results by using a signal-based PAPR (Peak-To-Average Power Ratio) judging method and provides a self-adaptive treatment method for judging a threshold. Meanwhile, in the invention, the influence of a near-far effect is considered, and a judging module for removing cross correlation after primarily judging signal existence is provided so as to weaken the influence of the cross correlation interference of C/A (Coarse/Acquisition) codes. A control module carries out two-dimensional search on a capturer, and a method for detecting a maximum value falling trend is used for judging Doppler frequency shift existing in the current signal so as to shorten the search time of a frequency dimension and increase the capture efficiency. The invention is suitable for systems such as a GPS (Global Positioning System), BD-2 (BeiDou-2), and the like and can achieve the cold-boot capture sensitivity up to -145dbm.

The invention provides a method for disturbing and inhibiting fractional fourier transformation through adding window segmentation overlapped processing, which comprises: firstly, utilizing the differences between the noise characteristics of a direct-spread communication signal on a fractional fourier region and the energy focusing characteristics of a sweep frequency interfering signal on a corresponding order, finishing the separation between the communication signal and the sweep frequency interference, then, utilizing window functions to inhibit the characteristics of side lobes of the sweep frequency interference, reducing the side lobe leakage of the interfering signal after transformation, enabling the energy of the sweep frequency interference on the fractional fourier region to focus on a major lobe, thereby effectively separating the interference and an useful signal, finally, adopting a method of segmentation overlapped processing, solving the problem that the energy of an edge signal is low due to adding window, inhibiting the energy of the sweep frequency interfering signal to the maximum, simultaneously, guaranteeing signal energy loss as little as possible, achieving higher code error rate performance, and guaranteeing reliable communication of a direct-spread system.

A parallel magnetic resonance imaging device comprises a plurality of imaging channels, a collection module, an initialization module, an operation module and a reconstruction module, wherein the collection module is used for collecting an undersampling matrix di (i is the serial number of each imaging channel and i > 0) from the plurality of imaging channels in an undersampling method and according to undersampling factors, the initialization module is used for acquiring an initialization image matrix rho and an initialization sensitivity matrix si (i is the serial number of each imaging channel and i > 0) of the imaging channels, the operation module is used for optimization iteration solving of a constraint function by means of the conjugate gradient algorithm according to the undersampling matrix di, the initialization image matrix rho and the initialization sensitivity matrix si to obtain a reconstructed image matrix rho and a sensitivity matrix si, and the reconstruction module is used for reconstructing an image according to the reconstructed image matrix rho and the sensitivity matrix si. When the parallel magnetic resonance imaging device is used for image reconstruction, imaging speed is effectively increased, and signal to noise ratio loss is small.

The invention discloses a pulse compression method for the field of linear frequency modulation signals. The method comprises the following steps: the orthogonal demodulation is implemented for the linear frequency modulation signals in the time domain; the low-pass filtering is implemented for the orthogonally demodulated linear frequency modulation signals in the time domain; the Fourier transform and the frequency band transfer are sequentially implemented for the low-pass filtered linear frequency modulation signals in the time domain to obtain linear frequency modulation signals in the frequency domain; the Fourier transform and the frequency band transfer are sequentially implemented for matched filtering signals in the time domain to obtain matched filtering signals in the frequency domain; the matched filtering signals in the time domain are converted to the matched filtering signals in the frequency domain; the complex conjugate multiplication is implemented for the linear frequency modulation signals in the frequency domain and the matched filtering signals in the frequency domain to obtain pulse compression signals in the frequency domain; and the Fourier inversion is implemented for the pulse compression signals in the frequency domain to obtain pulse compression signals in the time domain. The pulse compression method of the invention can improve the range resolution, reduce the loss of signal-to-noise ratio, and modify the image quality.

The present invention discloses a low loss interface device between coherent detection of combined frame synchronization and soft-decision decoding, which relates to a digital signal processing apparatus of anti-fading frame synchronization and low signal-noise ratio loss fading phase ambiguity demodulation. The low loss interface device is composed of an orthogonal down converter, a coherent detector, a soft-decision decoder, a low loss phase ambiguity demodulator, a frame synchronization extractor, a power supply and other components. The low loss interface device adopts a digital signal processing technique, uses frame header information of an encoder/decoder to perform phase recognizing, combines frame synchronization extraction and realizes the low loss interface between the low loss interface between the coherent detection and soft-decision decoder. And the present invention also has features of simple circuit structure, high integration degree, stabilized and reliable performance, portability, low-cost and so on. The low loss interface device is specially suitable as an interface circuit device between the coherent detection and soft-decision decoding in the long-term fading large-capacity communicating system required for low signal-noise ratio loss.

The invention provides an A/D quantization bit conversion system and method in a GNSS receiver. The system comprises a comparison module and a threshold adjustment module, wherein the comparison module and the threshold adjustment module work simultaneously, high-order quantized signals are input to the first input end of the comparison module, the comparison module converts the input high-order quantized signals into low-order quantized signals according to threshold values, and then the low-order quantized signals are output from the first low-order output end of the comparison module. The second low-order output end of the comparison module is connected with the input end of the threshold adjustment module, the second input end is connected with the output end of the threshold adjustment module, the threshold adjustment module is used for adjusting threshold values so that the low-order quantized signals output by the comparison module can conform to the corresponding best probability distribution. According to the A/D quantization bit conversion system and method, on the premise that complexity and cost of an existing GNSS receiver are not increased, an anti-interference technique can be applied to the existing low-order quantization GNSS receiver.

One or more embodiments of the present specification provide an anti-interference communication method and electronic equipment, which can solve the problem of reduced communication quality caused byinter-symbol interference and narrowband interference. The electronic equipment includes a memory, a processor, and a computer program stored on the memory and operable on the processor for performingan anti-interference communication method. The anti-interference communication method comprises the following steps that: a signal sending end allocates an information symbol of initial modulation information to a delay-Doppler domain resource grid to obtain a mixed jump symbol signal, carries out inverse symplectic Fourier transform and Hesenberg transform on the mixed jump symbol signal to obtain a time-domain sending signal, transmits the time-domain sending signal to a communication channel; and a signal receiving end receives the corresponding time-domain receiving signal, carries out Wigner transform and symplectic Fourier transform on the time-domain receiving signal to obtain a receiving signal, performs information symbol sequence detection on the receiving signal, and determinescommunication information sent by the signal sending end.

A multi-frequency programmable matching filter belongs to the field of digital signal spread spectrum communication. Every order of matching filters are composed of two matching filters, wherein the frequency of one matching filter is corresponding to an upper limit frequency of carrier signals, and the other matching filer is corresponding to a lower limit frequency of carrier signals. Frequencies of the two matching filters in every order vary according to the frequencies of input carrier signals, and at the same time, filter orders of the multi-frequency programmable matching filter are adjustable. Difference comparison between the data output by the matching filter and a local carrier template is conducted, and if an output signal is smaller than the difference of the local carrier template, the programmable matching filter outputs the output signal to a next-order matching filter for filtering until the output carrier signal being larger than the value of the local carrier template. Since multi-order filtering is performed on the carrier signals, useful components of the output carrier signals are enhanced as much as possible and a signal to noise ratio is increased.

The invention discloses a Doppler measurement method for solving target migration through range cell. The method is a speed measurement algorithm of a full-phase circular array pulse Doppler radar, and the target speed in different speed ranges can be precisely measured, and the migration through range cell can be solved. The signal to noise ratio loss problem caused by the migration through rangecell of the targets in different speeds can be solved by simultaneously using multi-order MTD filters, and the precise measurement on the target speed is realized by crossly comparing the multi-orderMTD filters used as the same time; since the accumulation time of the different filter groups is different, the signal to noise ratio loss caused by the migration through range cell of the target canbe reduced; and for the condition that partial speed range can be free from the signal to noise ratio, the probability of detecting the small target can be improved. By using the filters with different orders, the speed measurement precision on the target can be improved by using the high-order filter.

The invention provides a sidelobe suppression method for an OFDM communication signal. The sidelobe suppression method comprises the following steps of: S1, determining an OFDM signal parameter and generating a radar communication integrated transmitting signal according to the OFDM signal parameter; S2, performing mismatch processing on the transmitting signal to generate a receiving end reference signal, and performing linear convolution on the transmitting signal and the receiving end reference signal to generate a point spread function; S3, performing linear convolution on an echo signal obtained after the integrated transmitting signal is reflected by a space target and the receiving end reference signal to generate a pulse compression signal; S4, taking the pulse compression signal and the point spread function as an input signal and a reference signal of an LMS filter respectively, and then completing sidelobe suppression through the LMS filter.

The invention discloses a method for improving target angle measurement precision of an NLFM waveform radar. The method comprises the steps of carrying out first pulse compression processing on a radar target echo signal to obtain a first pulse pressure echo signal; performing beam forming processing on the first pulse pressure echo signal to obtain a beam forming result; carrying out Doppler frequency shift processing on the beam forming result through a Doppler filter to obtain a Doppler frequency estimated value; performing second pulse compression processing on the radar target echo signalaccording to the Doppler estimation value to obtain a second pulse pressure echo signal; and performing sum-difference beam phase comparison monopulse angle measurement on the second pulse pressure echo signal to obtain the radar target measurement angle. According to the method for improving the target angle measurement precision of the NLFM waveform radar provided by the invention, the completely matched pulse response filter is designed by utilizing the Doppler frequency estimation of the radar target echo signal, the pulse compression processing of the radar target echo signal is carriedout, and the signal-to-noise ratio loss of angle estimation data is reduced, so that, the angle measurement precision is improved, and the performance is stable.