As the number of spectrum users continues to grow, the need for efficient use of spectral resources grows along with it. SSDL, which stands for Sequentially-Switched Delay Lines, provides a solution to this issue. The SSDL concept is a time-switching strategy, which uses a set of switches and transmission lines to simultaneously route transmitted and received waveforms to their respective ports over a broad bandwidth.

M. M. Biedka, R. Zhu, Q. M. Xu and Y. E. Wang, "Ultra-Wide Band On-Chip Circulators for Full-Duplex Communications," 2018 IEEE/MTT-S International Microwave Symposium - IMS, 2018, pp. 987-990, doi: 10.1109/MWSYM.2018.8439445.

We explore a non-degenerate phase independent parametric quality factor (Q)-enhancement technique for aluminum nitride (AlN) Lamb wave resonators. Unlike other active Q-enhancement techniques which require precise phase control of the electronic feedback

loop, this technique is implemented by parametrically pumping AlN material stiffness to realize a negative resistance seen at the signal path.

Appl. Phys. Lett. 118, 254101 (2021); https://doi.org/10.1063/5.0053818