Magnetic-free electrical circulator based on AlN MEMS filters and CMOS RF switches

Xu, Cheng; Calayir, Enes; Piazza, Gianluca

doi:10.1109/memsys.2018.8346665

Cited by 19 publications

(3 citation statements)

References 11 publications

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“…In [25], three series resonators are connected in a Y topology to simplify the bias circuit. Three film bulk acoustic resonators (FBAR) in [27] and MEMs resonators in [28] are used in the same fashion to achieve non-reciprocity with a very small modulation frequency. Differential circulators are presented in [28]- [30] to cancel the undesired intermodulation products, which helps to improve the insertion loss, impedance matching, bandwidth, and noise figure.…”

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confidence: 99%

“…Three film bulk acoustic resonators (FBAR) in [27] and MEMs resonators in [28] are used in the same fashion to achieve non-reciprocity with a very small modulation frequency. Differential circulators are presented in [28]- [30] to cancel the undesired intermodulation products, which helps to improve the insertion loss, impedance matching, bandwidth, and noise figure. Three identical BPFs are used to broaden the isolation bandwidth of such spatiotemporally modulated circulator in [31].…”

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confidence: 99%

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Isolating Bandpass Filters Using Time-Modulated Resonators

Liu

Hickle

et al. 2019

IEEE Trans. Microwave Theory Techn.

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In this paper, we demonstrate for the first time an isolating bandpass filter with low-loss forward transmission and high reverse isolation by modulating its constituent resonators. To understand the operating principle behind the device, we develop a spectral domain analysis method and show that same-frequency non-reciprocity is a result of non-reciprocal frequency conversion to the intermodulation (IM) frequencies by the time-varying resonators. With appropriate modulation frequency, modulation depth, and phase delay, the signal power at the IM frequencies is converted back to the RF frequency and add up constructively to form a low-loss forward passband, whereas they add up destructively in the reverse direction to create the isolation. To validate the theory, a lumped-element 3-pole 0.04-dB ripple isolating filter with a center frequency of 200 MHz, a ripple bandwidth of 30 MHz, is designed, simulated, and measured. When modulated with a sinusoidal frequency of 30 MHz, a modulation index of 0.25, and an incremental phase difference of 45 • , the filter achieves a forward insertion loss of 1.5 dB and a reverse isolation of 20 dB. The measured non-modulated and modulated results agree very well with the simulations. Such nonreciprocal filters may find applications in wide-band simultaneous transmit and receive radio front-ends.

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Isolating Bandpass Filters Using Time-Modulated Resonators

Liu

Hickle

et al. 2019

IEEE Trans. Microwave Theory Techn.

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“…However, the ferromagnetic films are not CMOS process compatible and the technique does not scale favorably with volume reduction. Magneticfree circulators have been demonstrated by spatio-temporal modulation of a resonant cavity using varactors or switches [1][2][3][4][5]. Further improvements in the insertion loss (IL), isolation bandwidth (BW), and linearity (no side bands) have been reported by using differential modulation of LC tanks or FBARs [3,6,7].…”

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confidence: 99%

Mechanically Modulated Microwave Circulator

Torunbalcı

Sridaran

Ruby

et al. 2019

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems &Amp; Eurosensors XXXIII (TRANSDUCERS &Am

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This work presents a differential FBAR circulator that uses the bending mode to mechanically modulate the FBAR mode without any varactors or switches. The differential FBAR circulator achieves a 61.5 dB isolation (IX) with an insertion loss (IL) of 1.8 dB at 2.68 GHz, demonstrating the first MEMS-only circulator. The isolation bandwidth at -25 dB is 4.7 MHz and power handling of the circulator is limited by the FBARs to +34 dBm.

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A Generalized Model for Linear-Periodically-Time-Variant Circulators

Piazza

2019

Sci Rep

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Magnetic-free non-reciprocity based on linear-periodically-time-variant (LPTV) circuits has received significant research and commercial attention since it could revolutionize wireless communications. LPTV circuits are formed by two main components: linear-time-invariant (LTI) networks and periodically-modulated switches. The modulated switches are the core elements to break the reciprocity of LTI networks. To understand and design LPTV circulators, a universal and intuitive analytical model is required. However, such model does not exist as it is extremely challenging to accurately model and fully understand the LPTV behaviour of energy storage networks. To address this limitation, this work introduces a novel analysis method, which is broadly applicable to any LPTV networks, and validates it experimentally. The novelty of this methodology comes from two main contributions: (1) modelling of the switch as a resistor in parallel with a current-controlled current source; (2) the decomposition of the LPTV network into the linear superposition of two LTI networks. We apply this technique to model the exact behaviour of an LPTV circulator in the frequency domain.

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Magnetic-free electrical circulator based on AlN MEMS filters and CMOS RF switches

Cited by 19 publications

References 11 publications

Isolating Bandpass Filters Using Time-Modulated Resonators

Isolating Bandpass Filters Using Time-Modulated Resonators

Mechanically Modulated Microwave Circulator

A Generalized Model for Linear-Periodically-Time-Variant Circulators

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