  This work demonstrates the first non-reciprocal network based on switched
low-loss acoustic delay lines. A 21 dB non-reciprocal contrast between
insertion loss (IL=6.7 dB) and isolation (28.3 dB) has been achieved over a
fractional bandwidth of 8.8% at a center frequency 155MHz, using a record low
switching frequency of 877.22 kHz. The 4-port circulator is built upon a newly
reported framework by the authors, but using two in-house fabricated low-loss,
wide-band lithium niobate (LiNbO3) delay lines with single-phase unidirectional
transducers (SPUDT) and commercial available switches. Such a system can
potentially lead to future wide-band, low-loss chip-scale nonreciprocal RF
systems with unprecedented programmability.
