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 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.