A Study on Transmitter-receiver Isolation Based on Adaptive System Identification

Transmitter-receiver isolation is a inevitable problem for airborne jammer. Lower efficiency of jammer and even self-excitation might be caused by lower degree of transmitter-receiver isolation. Transmitter-receiver isolation is not satisfactory when the fixed step size normalized least mean square (NLMS) algorithm is implemented because of worse estimation accuracy. To solve this problem, a variable step-size NLMS algorithm based on prior estimation error is proposed in this paper. The correlation coefficient of the adjacent moment prior estimation error is employed in this NLMS algorithm to control the step size adaptively. The estimation accuracy as well as the isolation performance is improved by weakening the impact of syetem noise in this step size update scheme. The theory analysis and simulation results demonstrate that the performance of transmitter-receiver scheme based on the proposed variable step-size NLMS algorithm is better than schemes which are based on other least mean square algorithms.