Optimized Interference Canceling for Colocated Base Station Transceivers

Strong jamming signals from colocated transmitters can cause intermodulation and desensitization in receiver circuits. Cancellation circuits can remove interference but generate noise and distortion of their own. We analyze such a system using a signal-to-interference-and-noise ratio (SINR) measure. We show that the cancellation coupler can be optimized to maximize the SINR. The optimum coupler value is proportional to the expected level of the jammers. A hardware prototype reduced the jammers by 46 dB in a controlled experiment and by 25 dB in an over-the-air experiment. A convergence time of 8.4 ms was sufficient for this application.