Development of a single LMS loop three channels analog adaptive co-site interference cancelling system

Co-site interference is becoming prominent on some independent platforms (e.g., airplanes, satellites, space stations, and vessels). Although many digital multichannel cancellation algorithms have been investigated, the saturation problem of the receiver front-end caused by severe co-site interference should be addressed first with analog RF cancellation. Many studies are currently being conducted to develop an analog adaptive co-site interference cancellation system (AACICS). However, double LMS (Least Mean Square) loop in every channel raises the complexity and implemented difficulty. Above all, the interference cancellation in the scene of antenna swaying has received little attention, which severely limits the effective suppression of wideband interference. This study developed an analog 3-channel adaptive co-site wideband interference cancellation system (AACWICS-3ch) with one LMS loop in every channel and established the equivalent model of the AACWICS-3ch. The steady-state weight and interference cancellation ratio (ICR) were obtained by analyzing and solving the equivalent model. An in-depth analysis was conducted on the quantitative relationship correlations between the interference cancellation bandwidth, ICR, system gain, and antenna swing amplitude. Results reveal that AACWICS-3ch can greatly enhance the interference cancellation performance compared to 2-channel analog adaptive co-site interference cancellation system (AACICS-2ch). The maximum improved ICR is greater than 30 dB, and it overcomes the complexity of double LMS loop cancellation system with the increasing of channel. Finally, simulations and experiments validated the improvement of interference cancellation performance in AACWICS-3ch.