The Study Of Modulation Recognition In Shortwave Communication

In the modern warfare, electronic detection is the main intelligence source of accumulating and grasping situation of enemy and making strategies. Ground detection of electronic detection is used mainly to detect enemy’s shortwave or ultra-shortwave communications, but the shortwave communication brings about fading and delaying due to the multipath transmission. Meanwhile, the security of communication is increasingly valued, the modulation types of signal and the difficulty of modulation recognition are both increasing. Therefore, how to improve the existing modulation mode and recognition algorithms to adapt the shortwave channel has become the main problem that needs to be solved in the electronic detection at present.Therefore, this paper in the background of modulation recognition engineering application of the shortwave communication detection, based on the theory of shortwave channel and modulation recognition technology, fully analysed the modulation recognition technology, all-round summarized the current research situation. The characteristic of the shortwave channel were analysed to detail the key technology of how to recognize the modulation mode of the shortwave communication. Therefore this paper focused on the major project problem such as shortwave channel modeling and modulation recognition of the shortwave communication and so on. The main research and relation fruits are as follows.1. Detailed the characteristic of the shortwave channel, and modeling it by the Watterson shortwave channel model; the shortwave channel is well modeled by this model.2. According to the modulation type of the digital signal, a method that uses high order cumulates, discrete wavelet transform, fractal dimension and transient characteristics of feature extraction vector classification by support vector machine device for modulation recognition was proposed, and it improves recognition rate in the low SNR.3. The proposed method was applied to the modulation mode recognition project in the shortwave communication detection, and to cancel the effect of the symbols interference that caused by multipath transmission the CMA blind equalization was used.Series experiments proved that the proposed algorithm has certain robustness, and it can satisfy the recognition requirements of the shortwave channel, ensure the stability of signal modulation recognition, and also can be applied effectively to practical shortwave communication detection projects.