Research On Array Processing Algorithm For Radio Reconnaissance

Radio communication reconnaissance is an essential way of communication intelligence interception. With rapidly development of communication technology in recent years, the increasingly complex electromagnetic environment resulted from hostile, non-hostile interferences makes our existing military reconnaissance equipment detect poorly for enemy's communication signals. This problem has become increasingly prominent. How to improve the overall performance of communication reconnaissance is currently an important topic to study.The main work of this dissertation is to study the related technologies involved in the radio communication reconnaissance system. It includes software radio based digital array receive and channelization, wideband DOA estimation algorithm, direction pattern synthesis and interference nulling of uniform circular array, sub-array DBF based DOA estimation algorithm. Finally, the validities of the above technology are verified by a practical system.The main contribution of this dissertation includes the following aspects:Firstly, this dissertation studies the basic theory and techniques related to software radio and the structure of hybrid radix FFT based polyphase channelized receiver, and proposes a FIR filter design method—clock selection algorithm that is able to simultaneously realize decimation and filter and reduces the computation complexity while decimating. An efficient implementation method of decimation and filtering in digital down-converter circuit is also studied and this achieves a reasonable and efficient use of resources.The algorithms related with wideband DOA estimation technology, ISM algorithm, CSM algorithm, TOPS algorithm and consistent focusing algorithm, are in-depth studied and their performance analysis are given. Under the condition of wideband reception, a fast realization algorithm of simultaneously estimating DOA for multiple channels, fast space spectrum direction finding technology, is proposed, which replaces spectral peak searching with circular convolution by using the cyclical nature of steering vector and further replaces circular convolution with the product of fast Fourier transform. This scheme greatly reduces the computation burden. Simulation results show that the results of proposed method and classical MUSIC algorithm are fully consistent with each other.For increasingly complex electromagnetic environment, using adaptive beamforming technology to achieve high-quality signal reception is proposed. Through analysis of various adaptive criteria, a pattern synthesis algorithm (PSA) of uniform circular array is proposed and this algorithm is extended to directional uniform circular array. Finally, by reconstructing block matrix, an interference nulling technique is proposed which can effectively eliminate the main lobe interference of uniform circular array.An adaptive beamforming technology based DOA estimation method is proposed, which firstly employs beamforming technology to suppress interferences and then performs DOA estimation. This method is able to suppress the effect of interferences on DOA estimation with the greatest degree and effectively improves the performance of DOA estimation. Subsequently, a sub-array DOA based M-SBDOA algorithm is studied which can detect weak signal detection in the context of strong interferences, effectively suppress the effects of strong interferences, and estimate the DOAs of weak signals. The proposed algorithm has low computation complexity, simple structure and high estimation accuracy. Considering the shortcoming of uniform linear array itself, a SBDOA algorithm is proposed which is based on the mode space transformation method of uniform circular array. This algorithm overcomes the phased ambiguity of uniform linear array due to the particularity of its mode space and is able to estimate the source number larger than the number of array elements.The performance of DOA estimation and adaptive beamforming algorithms are verified by an array processing experimental system. The DOA estimation algorithm is realized by a fast spatial spectrum direction finding technology and can achieve real-time direction finding of eight signals in 30MHz bandwidth. This dissertation presents an analog and digital mixing beamforming method, which firstly generates a group of directional beams with high gain by analog beamforming, and then uses directional array PSA algorithm. This method can obtain synthetic beam meeting the demands of practical application.