Passive Intermodulation Interference Suppression through Sparse Discrete Fractional Fourier Transform

Abstract

With the wide application of duplex mode antenna, passive intermodulation (PIM) interference has become a severe problem. And the traditional methods have shortcomings that can not be overcome. In order to solve this issue, this paper proposes an algorithm to suppress passive intermodulation (PIM) interference based on digital signal processing (DSP). We choose power series model to express PIM signal, which is also called PIM interference model. In the proposed scheme, satellite transmit pilot signal during the pilot period. With the transmitted pilot signal and the received signal, the real-time parameters of PIM interference model can be obtained. Then during the data transmission period, data is transmitted in uplink and downlink separately. The PIM interference can be rebuilt through the downlink transmitted data and the PIM interference model. In this way, the PIM interference is suppressed. We chose chirp signal to be pilot signal for its wide bandwidth, which can cover all frequency in modulated system. In order to obtain the PIM interference model parameters, we use Sparse Discrete Fractional Fourier Transform (SDFrFT) through Pei method due to its low computational complexity. The simulation results show that this algorithm can reconstruct the original signal with a relatively low complexity.