A Radio Frequency Non-Reciprocal Network Based on Switched Low-Loss Acoustic Delay Lines

This work demonstrates the first 4-port radio frequency circulator based on switched low-loss acoustic delay lines. The 4-port circulator is built upon a recently reported frequency-independent, programmable, and non-reciprocal framework based on switched delay lines. Large delays provided by the in-house fabricated, low-loss, and wide-band lithium niobate (LiNbO3)SH0 mode acoustic delay lines are leveraged to produce high performance and reduce the modulation effort simultaneously for enabling non-reciprocity. The implemented 4-port circulator has been demonstrated with an 18.8 dB non-recip-rocal contrast between the insertion loss (IL = 6.6 dB)and isolation (25.4 dB)over a fractional bandwidth of 8.8% at a center frequency 155 MHz, using a record low switching frequency of 877.19 kHz. The circulator also shows 25.9 dB suppression for the intra-modulated tones. Upon further development, such a system can potentially lead to wide-band, low-loss chip-scale nonreciprocal RF systems with unprecedented programmability.