Adaptive Noise Cancellation for Two Frequency Radar Using Frequency Doubling Passive RF Tags

The use of an adaptive noise-cancellation technique has been explored in order to separate multiple sources of motion for a two-frequency Doppler radar system. A 2.45-GHz fundamental Doppler radar system was used together with a harmonic Doppler radar receiver to measure and identify two moving reflectors; one with a harmonic tag and one without. While the tagged motion alone was detected by the harmonic receiver, least mean squares and normalized least mean squares algorithms were applied to the fundamental receiver output to filter out the tagged-related motion content and successfully isolate the information content associated with only the non-tagged motion. Simulations were performed to study the effect of various parameters on the performance of the algorithms, and experiments were conducted to validate the feasibility of the method.