RFIC Inductorless, Widely-Tunable N-Path Shekel Circulators Based on Harmonic Engineering

Recently demonstrated non-magnetic circulators rely on the interference between an LPTV non-reciprocal gyrator and reciprocal transmission-line circuits, which limits their form factor and compromises the tunability of N-path circuits. In this paper, a new class of non-magnetic inductorless widely-tunable non-reciprocal circulators based on harmonic engineering is introduced. LPTV circuits rely on modulating the input signals with a square-wave clock waveform that can contain multiple harmonics. The harmonic engineering concept controls the response to various harmonics of the clock signal, the superposition of which results in the desired functionality. Two prototype N-path Shekel circulators have been implemented in 65nm CMOS. The first prototype, operating in the large-RC-regime can be reconfigured for operation across 0.1-1.1 GHz, with losses ranging from 2.4-3.4 dB. It has a form factor of λ
²
/2,000,000 at 500 MHz, with a power consumption of 9.6 mW. The second prototype operates in the low-RC-regime with a tuning range of 0.28-1.15 GHz and a loss of 2.3-3.3 dB, and achieves more than 20 dB isolation across a 233 MHz BW (38%) within a λ
²
/1,500,000 form factor at 600 MHz.