A Modulation-Defined RF Micro-Acoustic Delay Line based on ScAlN MEMS Resonators for Self-Interference Cancellation

We present and demonstrate a time-modulated tunable bandwidth (BW) and group-delay (GD) filter, exploring a slow-modulation operating region of N-path filters to extend the BW of conventional passive micro-acoustic filters. An array of MEMS resonators is fabricated with custom in-house ScAlN process, and heterogeneously integrated on PCB with commercial RF switches to showcase ultra-low modulation frequency, 2 to 6 % of the filter center frequency, with wide maximum BW (11.6 % with a $k_t^2 = 2.5\% $ at 430 MHz), three-fold wider than passive topologies, enabling reconfiguration while requiring no tunable passive. We show that the proposed prototype is suitable as a Self-Interference Canceler (SIC) in full-duplex scenarios, where real-time GD tunability is required. When used as an SIC, 40 dB SI cancellation within 14 % BW is achieved. Thanks to the slow-modulation approach, a 17 dBm power handling is demonstrated, along with a low −28 dBc distortion.