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

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 embodiment discloses a method and a device for transmitting / receiving signals in a microwave system, belonging to communication field. The transmitting method includes that transmitted signals are received through optical fiber, and the transmitted signals are modulated; intermediate RF transmission processing is performed on the modulated transmitted signals; the transmitted signals processed with intermediate RF processing are isolated with signals received by an antenna and transmitted by the antenna. The receiving method includes that signals received by the antenna are isolated with the transmitted signals and processed with intermediate RF transmission processing, and demodulated and transmitted through optical fiber. The transmission device comprises an optical fiber signal interface, a signal receiving module, a modulation module, an intermediate RF transmission module, a duplexer, a control module and a power supply interface. The embodiment adopts optical fiber to transmit and receive signals, and realizes large capacity microwave application; meanwhile, the cost is greatly reduced.

The present invention provides a design method of L-band SAR (synthetic aperture radar) satellite and navigation receiver anti-co-channel interference. According to the design method, an electronic microwave switch which works in a linkage manner with SAR pulse signals is additionally installed on a navigation receiver so as to suppress co-channel interference; the microwave switch is mainly used for isolating co-channel interference signals which are generated by an SAR load at the frequency point of the navigation receiver, the impulse power of the SAR load being higher than one kilowatt; the switching on and switching off of the microwave switch are controlled through timing signals generated by an SAR sub-system; compared with PRF (pulse repetition frequency) signals transmitted and received by the SAR sub-system, the timing signals are broadened; and the microwave switch is built in the navigation receiver in an integrated manner. With the design method adopted, the problem of the co-channel interference of an L-band SAR load and a global satellite navigation system can be solved, and the design of the SAR load is more free, navigation accuracy is ensured, and after-event processing is relatively simple.

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 embodiment of the invention provides a coherent multi-carrier capturing method and device, and the method comprises the steps: generating a Doppler factor / code phase two-dimensional plane of a subcarrier for a received signal of a subcarrier signal, searching a code phase maximum value on the two-dimensional plane, and the code phase maximum value serving as a code phase estimation value; calculating a carrier phase compensation amount of the subcarriers according to the code phase estimation value, obtaining a receiving signal subjected to carrier phase compensation by combining a two-dimensional plane, and carrying out coherent combination on the receiving signals subjected to carrier phase compensation of all subcarriers; and comparing the merged received signal with a preset monitoring threshold to obtain a correlation peak exceeding the monitoring threshold, and respectively obtaining the frequency offset value and the propagation delay of the subcarrier according to the Doppler factor and the code phase of the correlation peak on the two-dimensional plane of the subcarrier. According to the embodiment of the invention, the defects of a non-coherent capturing method in a high-dynamic, large-frequency-point coverage range and weak-signal environment are overcome, the capturing performance is greatly improved, and the average capturing time is shortened.

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.

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 discloses a method and a system for rapidly capturing a relay satellite measurement and control system signal. The method comprises the following steps: S1, analog-to-digital conversion: performing band-pass sampling on an analog intermediate-frequency signal through a high-speed analog-to-digital converter by comprehensive digital baseband equipment to obtain a digital intermediate-frequency signal; S2, down-sampling processing; S3, implementation of a capturing time shorter than a data sampling time: controlling two memories to implement seamless caching of data streams, wherein a caching depth is a sampling number of coherent integration, and a switching interval between the two memories is a sampling time of captured data; and S4, implementation of a search of a signal dynamic range: converging a Doppler frequency range by adopting a two-round frequency search according to a speed of outputting a frequency search unit result in a data sampling period, and obtaining a code phase offset of cached data in a third-round phase search. The system is used for implementing the method. The method and the system have the advantages of easiness in implementation, high accuracy, capability of satisfying a current engineering condition, and the like.

The invention discloses a symbol jumping resistant direct spread spectrum signal dynamic focusing method based on KT-LVT. The invention adopts a KT-LVT dynamic focusing method for resisting symbol jumping based on delay correlation, the influence of the symbol jumping is eliminated when the pseudo-code phase distance migration and the Doppler frequency migration are eliminated, so that the direct spread signal dynamic focusing under the low signal to noise ration and high dynamic scene is realized. Compared with the non-search type dynamic focusing method, the signal to noise ratio loss caused by non-linear operation in the method is small, the processing gain is high, good noise resistance is provided, and the method is more suitable for capturing a weak signal; and meanwhile, this method is unnecessary to timely traverse and compensate the local pseudo code rate and the Doppler frequency, and unnecessary to search the symbol jumping edge, so that the computation burden is low, the storage content is small and the instantaneity is high in comparison with the non-iterative non-search type dynamic focusing method.

The invention discloses a matching compression device for linear frequency modulation signals and a matching compression method. The matching compression device comprises a linear frequency modulation signal source (1), a first power distributor (2), a digital control oscillator (3), a second power distributor (4), a 90-degree phase shifter (5), a first frequency mixer (6), a second frequency mixer (7), a first low-pass filter (8), a second low-pass filter (9), a first data acquirer (10), a second data acquirer (11), a matching filter (12) and a computer (13). Compared with pulse compression devices and compression directions in the prior art, the matching compression device and the matching compression method disclosed in the invention can improve the range resolution, reduce the signal-to-noise-ratio loss, and modify the image quality. The matching compression device and the matching compression method disclosed in the invention can be used for signal processing of radar and earthquake detecting systems.

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 lossinterface 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.