Study On Interference Suppression Technology Based On Fractional Transform

Interference suppression is always be paid much attention in communication domain. Now , plenty of mature theory and technology has been proposed in this aspect. Technology based on adaptive-filter, transform domain, code-aid and so on offer reliable and effective tool to the narrow-band interference suppression. But, as deeply into the study and the increase need of the practical application, broadband interference suppression become the new focus on that direction. Under this condition, as present technology had defects while be used in the broadband suppression, people beginning to search new tools to achieve the purpose of broadband interference suppression.Fractional transforms is a new time-frequency analysis tool which be paid close attention of late years, which gained by the fractional though expanded in all sort of conventional transform. Not only they have the specially characteristic that could reflect the time-frequency property of the signal as fairly good as the general time-frequency analysis tools, but also most of them are one dimension transform. Because of that, fractional transform has the advantage as general time-frequency analysis tool has while using in the broadband interference suppression, even more, the computation of fractional transform is much less. However, this transform is also under study, there are many problem not well deal with in the basic theory, that limit the application of the fractional transform in the practical.Fractional Fourier transform is a special fractional transform, that the fractional though is gained by the expansion from the common Fourier transform to it. The research of this special fractional transform is the most broadly and integrity in all fractional transform. There are success algorithms in its basis theory, the application in signal processing and other domain. It also be the first one of the fractional transform in the interference suppression domain, there was algorithm of the time-domain elimination, the suppression of special broadband interference-linear frequency modulation interference in fractional Fourier domain. But this algorithm has some shortage.The main substance of my research is use the fractional Fourier transform to the broadband interference suppression of the spread spectrum communication system. It based on the necessary known of the basic mathematic theory of the fractional transform, and take the advantage of the broadband nonstational signal processing by the fractional Fourier transform.The introduction of this thesis introduce the background and the research purport of the thesis, and the context of the fractional transform;the second secession is the simple introduce of the basic theory of the fractional transform;the third secession is the practical application in signal processing of the fractional Fourier transform;the main point of the thesis is in the forth secession, it focus on the interference suppression in DSSS system based on the FRFT, and theimprovement of this algorithm is given. The last section concludes the thesis.