The Compensation Of Passive Intermodulation Based On Digital Signal Processing

Passive intermodulation is a passive device nonlinear characteristics appear in certain environments, to produce a phenomenon new frequency components. In current wireless communications and satellite communications, and generally take the form of receiving common antenna, so that transmit signals via a passive antenna, diplexer and other passive components generated when the intermodulation interference that may fall within the frequency band of the received signal, for received signal interference. This paper may fall into the receiver band passive intermodulation products, the use of Volterra series established its mathematical model. Designed a passive intermodulation interference cancellation method, based passive intermodulation interference mathematical model to estimate the actual interference, and thus its cancellation. Wherein, when the received signal at the receiver passive intermodulation interference frequency, phase and delay estimation, analogy paired carrier multiple access technique, by calculating the received signal and the local passive intermodulation interference model correlation value The method and frequency of the interference signal when the two-dimensional estimation, to give actual delay and frequency interference signal with the local interference model offset. After carrying out the delay and frequency offset compensation, related cumulative method can also take advantage of the phase shift can be calculated. Finally, the use of LMS adaptive filter for interference signal estimation and tracking, in response to passive intermodulation interference when varying characteristics. In order to verify the above algorithm, designed and implemented a set of complete transmission link, the error rate can be tested hardware verification platform FPGA-based implementation of the IF signal generated in processing, and can be IF and RF modes working. On the platform to achieve the above-mentioned passive intermodulation interference suppression algorithm, the algorithm has been tested and verified with good performance, you can get more than 20 dB gain error rate.