Digital zero intermediate frequency self-adaptation wave trapping method based on FPGA (filed programmable gate array)

Abstract

The invention discloses a digital zero intermediate frequency self-adaptation wave trapping method based on FPGA (filed programmable gate array). The method includes the steps of firstly, using FFT (fast Fourier transform) to transform the sampled intermediate frequency signal into a frequency domain; secondly, performing frequency spectrum statistic analysis and threshold judgment on the intermediate frequency signal in the frequency domain, and judging NBI number and NBI central frequency; thirdly, turning to the seventh step if no interference exists; if interference exists, using an orthogonal digital down converter to perform orthogonal demodulation on the sampled intermediate frequency signal, using a low-pass filter to only remain the positive frequency component of the sampled intermediate frequency signal, and converting to obtain a baseband signal; fourthly, performing frequency spectrum shifting on the baseband signal, shifting the first interference point to the zero frequency, using a high-pass filter to filter interference frequency spectrum components so as to restrain the first interference point; fifthly, repeating the fourth step until all the interference points are restrained; sixthly, transforming the signal after interference restraining into the actual signal; seventhly, by a baseband processing module, performing demodulation output.

Description

Technical field [0001] The invention belongs to the field of communication technology, relates to strong narrow-band interference suppression in a spread spectrum communication system, and in particular relates to an FPGA-based digital zero-IF adaptive trap. Background technique [0002] In direct-spread communication systems (DDDS), typical signals with low probability of interception are transmitted. The signal occupies a wide spectrum and low power density. It has good suppression performance against various types of interference, but in practice it is often limited by the system bandwidth. The inherent spreading gain of the system itself is not enough to suppress the high-power strong narrow-band interference NBI (Narrow-Band Interference). Therefore, it is necessary to use signal processing technology to suppress strong narrowband interference without increasing the signal bandwidth before despreading, and improve the anti-interference ability of the system. [0003] At prese...

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Problems solved by technology

figure 1 The traditional NBI suppression model of the spread spectrum system based on these three technologies is given. It can be seen from the figure that this method closely combines interference detection and interference suppression. Before NBI detection, the original signal x(t ) for preprocessing, no matter whether the system has NBI or not, it will damage x(t) to a certain extent. Although various methods are used to compensate and restore the intermediate frequency signal in the later stage, it increases the complexity of system design and hardware overhead. difficult to achieve

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