Design and Analysis of Digital-to-Analog Hybrid RF Interference Cancellation System Based on Multitap Structure

The analog control circuit of existing RF interference cancellation system is too complex, and the convergence speed cannot be flexibly tuned. This article proposes a digital-to-analog hybrid RF interference cancellation system based on multitap structure (MDARFICS), where the analog control circuit is digitized, so it can be highly integrated and easily tuned. The analytical theory model of the MDARFICS is established for the first time, which can suppress interference with a large power dynamic range and bandwidth. The factors that affect the cancellation performance, i.e., stability, wideband interference cancellation ratio (WICR), and convergence speed, are studied. The stability criterion is obtained, that is, loop gain, sample rate, and tap delay affect the stability cooperatively, and it is found that the sample rate must be selected according to tap delay. Studies show the MDARFICS can effectively suppress wideband interference. The larger the number of taps and control step size, the smaller the bandwidth and delay difference between the tap and interference channel, and the larger the WICR. The convergence speed accelerates as the control step size and filter coefficient increase. Simulations and experiments verify the theoretical analysis. The research results are of much value to the implementation of the MDARFICS.