Duplexer Cancellation Path for RF Leakage Isolation

The patent converts the harmful transmit signal leakage into a beneficial cancellation mechanism by capturing the leaked signal through a coupling element, processing it through a cancellation path with phase shifters and amplifiers, and then subtracting it from the receive path. This transforms the harmful leakage energy into a useful cancellation signal that actively removes interference without requiring stronger attenuation filters.

The patent introduces a cancellation path as an intermediary system between the transmit and receive paths. This intermediary includes a coupling element that taps the leaked signal, a processing path with phase shifters and amplifiers that condition the signal, and a subtraction mechanism that removes the interference. This intermediary approach achieves better isolation without increasing the attenuation of the main signal path, thereby avoiding increased insertion loss.

Instead of using complex high-order attenuation filters to reduce leakage, the patent converts the leakage problem into a benefit by using the leaked signal itself for cancellation. This approach replaces complex filter construction with a cancellation path that uses simpler components like couplings, phase shifters, and amplifiers, thereby reducing overall device complexity while achieving better isolation.

The patent changes the approach from passive attenuation (using fixed filter parameters) to active cancellation (dynamically adjusting phase and amplitude parameters). The cancellation path uses variable phase shifters and amplifiers to adaptively match and subtract the leakage signal, providing flexible isolation control without requiring complex fixed filter designs. This parameter-based approach simplifies the overall filter construction.