Differential RF Front End Filtering for Harmonic Cancellation

Instead of using aggressive filtering to suppress harmonics, the patent converts the harmonic problem into a benefit by utilizing the harmonics themselves for cancellation. The differential filter generates identical even-order harmonics in both paths, which then cancel each other out through differential subtraction, achieving harmonic suppression without the need for aggressive filtering and associated insertion losses.

The patent changes the approach from filtering (removing harmonics) to cancellation (using harmonics). By modifying the filter configuration to a differential topology, the system changes the parameter of harmonic handling from suppression to exploitation, where the same harmonic components that were previously harmful are now used constructively for cancellation.

The patent segments the filtering function into two identical differential paths, each containing its own bandpass filter. This segmentation allows each filter to generate identical even-order harmonics that can then be canceled through differential subtraction, providing superior harmonic cancellation compared to a single filter followed by a balun conversion.

The patent employs asymmetric signal paths in terms of their function within the differential pair. While the physical structure may be symmetric, the signal processing is asymmetric - one path's harmonics are subtracted from the other path's harmonics, creating a differential cancellation effect that is more effective than symmetric single-ended filtering.