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

Abstract

Recently demonstrated non-magnetic circulators rely on the interference between a linear periodically time-varying nonreciprocal gyrator and reciprocal passive microwave circuits, which limits their form factor and tunability. In this work, a new class of widely tunable non-magnetic inductorless nonreciprocal circulators based on harmonic engineering is introduced. LPTV circuits rely on modulating the input signal with a square-wave clock that contains multiple harmonics. The introduced harmonic engineering concept controls the response of the circuit to various harmonics of the clock waveform, the superposition of which results in the desired functionality. Two miniaturized N-path Shekel circulators have been implemented in 65-nm CMOS. The first prototype, which uses a four-path structure operating in the large- RC-regime, can be reconfigured for operation across 0.1-1.1 GHz with losses ranging from 2.5 to 3.4 dB. It has a form factor of (λ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> )) at 500 MHz, with a power consumption of 3-21 mW. The second prototype uses an eight-path structure and operates in the low- RC-regime with a tuning range of 0.28-1.15 GHz and losses of 2.3-3.3 dB and achieves more than 20-dB isolation across a 233-MHz BW (38%) within a (λ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> )) form factor at 600 MHz consuming 26-67 mW of power. To date, this work has the smallest form factor reported among the state of the art.