3results about How to "Increase processing gain" patented technology

The invention provides a time reversal processing method for detecting an underwater moving target, which comprises the following steps of: transmitting a predetermined underwater sound signal s (t) at a transmitting platform for the first time, and receiving a first echo signal x (t) at a receiving platform; self-adaptively estimating H (.) according to the underwater acoustic signal s (t) transmitted for the first time and the echo signal x (t) for the first time, wherein H (.) represents underwater acoustic environment parameter information between an underwater acoustic signal transmitting platform and the underwater moving target, Doppler information of target movement and current channel response information; acquiring a data segment containing channel broadening and target impact response broadening from the first echo signal x (t), and performing time reversal processing to obtain an underwater acoustic signal simulating second active emission; calculating and simulating the underwater acoustic signal actively transmitted for the second time by using H (.), and carrying out convolution to obtain a corresponding second time echo signal; and processing the second echo signal to detect the underwater moving target.

This invention discloses a signal receiving method for spread spectrum underwater acoustic communication in long-distance time-varying channels, comprising: acquiring the received communication signal, obtaining a baseband signal through down-conversion and low-pass filtering, and dividing the baseband signal into blocks according to pilot signals and spread spectrum sequence signals after synchronization; performing initial channel estimation using the pilot signals to obtain initial Doppler estimates, time delay estimates, and amplitude response estimates for each path; performing frequency offset compensation and resampling on the first spread spectrum sequence received signal using the estimated Doppler; constructing a Rake receiver for the first spread spectrum sequence signal to be estimated using the estimated time delay and amplitude response; combining the Rake receiver and using maximum likelihood estimation to realize the decision on the current spread spectrum sequence and the log-likelihood ratio of each corresponding bit; estimating the Doppler, time delay, and amplitude response of the current spread spectrum sequence signal using the decided spread spectrum sequence; and so on, completing the decision on all spread spectrum sequences. This invention can effectively reduce the demodulation bit error rate.

The application relates to a direction-finding method based on array-received data reconstruction, and belongs to the technical field of array signal processing. The application first calculates the covariance matrix of array-received signals, then combines the array flow characteristics to use the elements in the covariance matrix to perform array-received data reconstruction, and finally performs direction finding based on the reconstructed received data matrix, so that the processing gain and the direction-finding precision are further improved. The application can improve the processing gain of array signals and the spatial resolution of array direction finding without increasing the number of array elements and the array aperture. Compared with the traditional beam synthesis method, the application has higher direction-finding precision and sidelobe suppression ratio.