Research On Short-Wave Adaptive De-noising Technology

Due to the transmission simple equipment, long distance, mature technology and high security, short-wave radio communication has been widely used in the military. But short-wave communication is highly susceptible to noise of nature and human. The noise in the short-wave can seriously interfere with the receiving of the signal, which reduces communication quality deeply. Therefore, how to effectively suppress and filter noise contained in the short-wave has always been a hot research and focal point. Combined with the noise issue in the reality short-wave receiving and in-depth study of short-wave de-noising algorithms, this paper proposes two different de-noising algorithm including adaptive median threshold de-noising algorithm based on frequency domain amplitude estimating and de-noising technology based on filter algorithm. The primary contents of the thesis are as following:1.De-noising technology based on median filter of noise basal estimate:As the issue of noise in the short-wave communication has impacted the detection and low alarm rate of the signal, the paper uses the different frequency amplitude(energy) feature between the background and the short-wave in different frequency point. Namely, the general noise amplitude throughout the bandwidth will be smaller than the signal amplitude, and the energy of the signal will just concentrate on several fixed frequency band. On this basis, we make the received signals do short-time Fourier transform, and then adopt adaptive threshold algorithm to anticipate the base of the shortwave signal. So, we can set an appropriate threshold and the threshold do minus operation with the original signal according to certain false alarm rate, so that the noise in the signal can be removed. The paper proposes a median algorithm which treats the signal spectrum as one gray scale to achieve short-wave signal de-noising. Results show that the median algorithm is effective for unknown short-wave de-noising and suppressing pulse, it also can reduce the false alarm rate.2.Adaptive de-noising technology based on QR-LSL filter algorithm:After the receiver pro-processing the short-wave, if the further processing is not be taken, the issue of remained noise will affect the detection of module type.while adaptive filter algorithm can be directly used to filter for the signal in time domain which makes the receiver signal processing unit structure get simple. And the adaptive filtering algorithm has the advantage of fast convergence speed, stable performance and good accuracy, which can satisfy the high real- time demand. so an adaptive filter algorithm is carried out. First of all, through the analysis, this paper demonstrates the feasibility of this method. On this basis, a new improved adaptive algorithm is adopted. QR-LSL algorithm is applied to shortwave signal processing, the proposed algorithm can achieve better de-noising performance compared with other adaptive filter algorithms.