Research On Detecting Direct Spread Signal Based On Wavelet Transform (Institutions Of Higher Education Teacher)

The communication system of direct-sequence spread-spectrum (DSSS) has two characteristics of stochastic coding modulate and signal correlation processing, which make it has many excellence, such as restraining noise and interference, working under low density of spectrum, keeping secret, multi-address and choosing address arbitrarily .measure in high precision and so on. Now it is widely used in many areas of numeric communication, such as keeping secret communication, multi-address communication, secondary planet navigate positioning system.Now researching on DSSS is based on knowing the PN serial .But in anti-collaboration communication, the receiving doesn't know the PN serial that DSSS uses. In this case, how to detect the message becomes the first important problem that must to be solved.In the real signal processing, the signal we get always contains lots of noise. In order to get the useful message from the signal with noise, we must use some methods to de-noise in the message. Wavelet is a signal processing technology that develops recently, and it is the development of Fourier, which is a signal processing method that can analysis signal locally both in time-area and frequency-area. Wavelet transforms modulus maxima has predominance in detecting the singularity and break configuration of the signal, so it can get the singularity message on the given signal nicely. Signal and noise shows different properties through wavelet transform, so wavelet can be used to separate the signal and the noise. Because of the inherence characteristics such as auto-correlation and cross-correlation, by de-noising using modulus maxima, we can observe the data's function of auto-correlation which is cumulated many times to detect whether there is DSSS or not. This thesis has introduced in detail the principles of wavelet transform modulus maxima de-noising method and studied the auto-correlation detection method of the DSSS signal based on the features of the DSSS signal, taking the BPSK signal as an example. Finally, simulation is given in this paper, using Matlab to validate the research on detecting direct spread signal based on wavelet transform method.