  Previously, we presented a non-magnetic, nonreciprocal N-path-filter-based
circulator-receiver (circ.-RX) architecture for full-duplex (FD) wireless which
merges a commutation-based linear periodically-time-varying (LPTV) non-magnetic
circulator with a down-converting mixer and directly provides the baseband (BB)
receiver signals at its output, while suppressing the noise contribution of one
set of the commutating switches. The architecture also incorporates an on-chip
balance network to enhance the transmitter (TX)-receiver (RX) isolation. In
this paper, we present a detailed analysis of the architecture, including a
noise analysis and an analysis of the effect of the balance network. The
analyses are verified by simulation and measurement results of a 65 nm CMOS 750
MHz circulator-receiver prototype. The circulator-receiver can handle up to +8
dBm of TX power, with 8 dB noise figure (NF) and 40 dB average isolation over
20 MHz RF bandwidth (BW). In conjunction with digital self-interference (SI)
and its third-order intermodulation (IM3) cancellation, the FD circ.-RX
demonstrates 80 dB overall SI suppression for up to +8 dBm TX average output
power. The claims are also verified through an FD demonstration where a -50 dBm
weak desired received signal is recovered while transmitting a 0 dBm
average-power OFDM-like TX signal.
