Hossein Miri Lavasani

Thin-film piezoelectric-on-silicon resonators for high-frequency reference oscillator applications

This paper studies the application of lateral bulk acoustic thin-film piezoelectric-on-substrate (TPoS) resonators in high-frequency reference oscillators. Low-motional impedance TPoS resonators are designed and fabricated in 2 classes--high-order and coupled-array. Devices of each class are used to assemble reference oscillators and the performance characteristics of the oscillators are measured and discussed. Since the motional impedance of these devices is small, the transimpedance amplifier (TIA) in the oscillator loop can be reduced to a single transistor and 3 resistors, a format that is very power-efficient. The lowest reported power consumption is ~350 muW for an oscillator operating at ~106 MHz. A passive temperature compensation method is also utilized bThis paper studies the application of lateral bulk acoustic thin-film piezoelectric-on-substrate (TPoS) resonators in high-frequency reference oscillators. Low-motionalimpedance TPoS resonators are designed and fabricated in 2 classes--high-order and coupled-array. Devices of each class are used to assemble reference oscillators and the performance characteristics of the oscillators are measured and discussed. Since the motional impedance of these devices is small, the transimpedance amplifier (TIA) in the oscillator loop can be reduced to a single transistor and 3 resistors, a format that is very power-efficient. The lowest reported power consumption is ~350 muW for an oscillator operating at ~106 MHz. A passive temperature compensation method is also utilized by including the buried oxide layer of the silicon-on-insulator (SOI) substrate in the structural resonant body of the device, and a very small (-2.4 ppm/degC) temperature coefficient of frequency is obtained for an 82-MHz oscillator.y including the buried oxide layer of the silicon-on-insulator (SOI) substrate in the structural resonant body of the device, and a very small (-2.4 ppm/degC) temperature coefficient of frequency is obtained for an 82-MHz oscillator.

A 76 dB

This paper reports on the design and characterization of a high-gain tunable transimpedance amplifier (TIA) suitable for gigahertz oscillators that use high-Q lateral micromechanical resonators with large motional resistance and large shunt parasitic capacitance. The TIA consists of a low-power broadband current pre-amplifler combined with a current-to-voltage conversion stage to boost the input current before delivering it to feedback voltage amplifiers. Using this approach, the TIA achieves a constant gain of 76 dB-Ohm up to 1.7 GHz when connected to a 2 pF load at the input and output with an input-referred noise below 10 pA/√(Hz) in the 100 MHz to 1 GHz range. The TIA is fabricated in a 1P6M 0.18 μm CMOS process and consumes 7.2 mW. To demonstrate its performance in high frequency lateral micromechanical oscillator applications, the TIA is wirebonded to a 724 MHz high-motional resistance (Qunloaded ≈ 2000, Rm ≈ 750 Ω, CP ≈ 2 pF) and a 1.006 GHz high-parasitic (Qunloaded ≈ 7100, Rm ≈ 150 Ω, CP ≈ 3.2 pF) AIN-on-Silicon resonator. The 724 MHz and 1.006 GHz oscillators achieve phase-noise better than -87 dBc/Hz and -94 dBc/Hz @ 1 kHz offset, respectively, with a floor around -154 dBc/Hz. The 1.006 GHz oscillator achieves the highest reported figure of merit (FoM) among lateral piezoelectric micromechanical oscillators and meets the phase-noise requirements for most 2G and 3G cellular standards including GSM 900 MHz, GSM 1800 MHz, and HSDPA.

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This paper reports on the implementation and characterization of a low phase-noise oscillator based on a very high quality factor (Q) 145MHz capacitive silicon micromechanical resonator. The utilized resonator is a silicon bulk acoustic resonator (SiBAR) operating in its first width-extensional mode with a maximum Qunloaded~74,000 that is specifically optimized for low motional impedance. The sustaining circuitry is a 3.6mW CMOS transimpedance amplifier (TIA) that uses common source topology with local shunt-shunt feedback. The measured phase-noise of the oscillator at 1kHz offset from the carrier is -111dBc/Hz with phase-noise floor reaching below -133dBc/Hz.

1.7 GHz 0.18

This paper reports on the demonstration of series tuning for lateral micromechanical oscillators and its application for electronic temperature compensation of piezoelectric lateral bulk acoustic resonator (LBAR) micromechanical oscillators. Two aluminum nitride-on-silicon (AlN-on-Si) piezoelectric LBARs, one operating at 427 MHz (Rm ≈180 Ω, Qunloaded ≈ 1400) and the other operating at 541 MHz (Rm ≈ 55 Ω, Qunloaded ≈ 3000) are interfaced with a 13 mW three-stage tunable TIA implemented in 0.18 μm 1P6M CMOS process to sustain the oscillation. Recognizing the impact on the frequency tuning range due to the body capacitances appearing in parallel with the ports of the resonator, the TIA uses parasitic cancellation techniques to neutralize this effect and boost the tuning range of 427 MHz and 541 MHz oscillators, by as much as 12× to 810 ppm and 1,530 ppm, respectively, with negligible impact on the phase noise performance. The shunt parasitic capacitor is either resonated out with an active inductor or is cancelled out by using a single-terminal negative capacitor of equal value. However, the oscillator that uses negative capacitance parasitic cancellation yields larger tuning. This extended tuning range is used for temperature compensation. A 2 mW bandgap-based temperature compensation circuit which uses second-order parabolic approximation is fabricated on the same chip. Using this temperature compensation circuit has lowered the overall frequency drift of a 427 MHz tunable oscillator using negative capacitance cancellation from ±390 ppm to ±35 ppm in the -10°C to 70°C temperature range. The phase noise of this oscillator reaches -82 dBc/Hz at 1 kHz offset. The total phase noise variation for offset frequencies below 10 kHz is under 5 dB within the specified tuning range, and the best phase noise floor is under -147 dBc/Hz . Due to the higher Q and lower insertion loss of the resonating tank, the 541 MHz oscillator achieves -86 dBc/Hz at 1 kHz offset, and lower phase noise floor of -158 dBc/Hz.

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This paper presents a 496 MHz low phase-noise reference oscillator using a high-Q lateral-mode AlN-on-Si micromechanical resonator that does not require DC voltage for operation. The sustaining amplifier consists of an inductorless high-gain CMOS transimpedance amplifier (TIA) that is optimized for low phase-noise. The resonator is designed to have a high quality factor in air (Q-3800) with low motional impedance. The measured phase-noise at 1 kHz offset is -92 dBc/Hz with phase-noise floor below -147 dBc/Hz (exceeding GSM phase-noise requirement by 2 dB and 28 dB, respectively).

m CMOS Tunable TIA Using Broadband Current Pre-Amplifier for High Frequency Lateral MEMS Oscillators

This paper reports on the first demonstration of a low phase-noise 467 MHz temperature-compensated oscillator based on a ZnO-on-nanocrystalline diamond lateral bulk acoustic resonator (LBAR). The temperature compensation is achieved by using a thin silicon-dioxide buffer layer on the surface of the diamond film. The oscillator performance is compared with an uncompensated 496 MHz AIN-on-silicon oscillator. The sustaining circuitry is comprised of a 9.4 mW tunable transimpedance amplifier (TIA) in 0.18 mum CMOS. The phase-noise is measured below -80dBc/Hz at 1kHz offset with temperature drift of < -4ppm/degC from -5degC to 90degC.

A 145MHz low phase-noise capacitive silicon micromechanical oscillator

This paper presents a fully integrated tunable lumped filter on silicon using a low-temperature silver micromachining process. A prototype 836-MHz bandpass filter with a 3-dB bandwidth of 5.9% and insertion loss of 4.8 dB is demonstrated in a second-order coupled-resonator configuration. Continuous tuning of 50 MHz is achieved by electrostatically actuating the lateral air-gap capacitors of the filter. To control the bandwidth while tuning the center frequency, reconfigurable termination impedance is proposed. As a proof of concept, a low-noise amplifier with tunable input impedance is designed to interface with the bandpass filter. The tunable impedance is realized at the input of the low-noise amplifier using a shunt positive metal-oxide-semiconductor transistor. The fabrication, design, and measurement results of the filter are detailed, and future research directions to improve the performance of such filters are discussed.

Electronic Temperature Compensation of Lateral Bulk Acoustic Resonator Reference Oscillators Using Enhanced Series Tuning Technique

This paper reports on the design, implementation, and phase-noise optimization of low-power interface IC for dual-frequency oscillators that utilize two high quality factor (Q) width-extensional bulk acoustic modes of the same AlN-on-silicon resonator. Two 0.5-μm CMOS transimpedance amplifiers (TIA) have been designed, characterized, and interfaced with two dual-mode resonators operating at 35.5/105.7 MHz (first/third order modes) and 35.5/174.9 MHz (first/ fifth order modes). One TIA uses open-loop regulated cascode (RGC) topology in the first stage to enable low power operation, whereas the second one uses an inverter with shunt-shunt feedback to deliver higher gain with lower phase noise. An on-chip switching network is incorporated into each TIA to change the oscillation frequency based on the different phase shift. The effect of TIA on the phase-noise performance of oscillators is studied and compared for both topologies. The measured phase noise of low- and high-frequency modes at 1 kHz offset from carrier are -114 and -108 dBc/Hz for the 35/105 MHz oscillator, and -108 and -105 dBc/Hz for the 35/175 MHz oscillator, respectively, whereas the far-from-carrier reaches below -140 dBc/Hz in all cases.

A 500MHz Low Phase-Noise A1N-on-Silicon Reference Oscillator

This paper reports on the first demonstration of series tuning for lateral micromechanical oscillators and its application in a temperature-compensated 427MHz AlN-on-Si reference oscillator. The sustaining amplifier is a 13mW tunable TIA implemented in 0.18µm CMOS that uses shunt-parasitic cancellation to increase the tuning by 12× to 810ppm. The tunable oscillator along with a 2mW on-chip temperature compensation circuit has reduced the overall frequency drift to 70ppm in −10°C to 70°C. The phase-noise of the oscillator reaches −82dBc/Hz at 1kHz offset with floor below −147dBc/Hz.

Low phase-noise UHF thin-film piezoelectric-on-substrate LBAR oscillators

Fully integrated low insertion loss micromachined band-pass filters are designed and fabricated on the silicon substrate (ρ = 10‐20 � cm, er = 11.9) for UHF applications. Filters are made of silver, which has the highest conductivity of all metals, to minimize the ohmic loss. A detailed analysis for realizing low insertion loss and high out-of-band rejection filters using elliptic magnitude characteristics is presented, and a comprehensive model to take into account inductive parasitics of the interconnects is developed. Temperature characteristics of the filters are measured and show stable performance. The presented filters are different from the previously reported lumped element filters in that all filters are fully integrated on silicon substrate and occupy a remarkably smaller die area. Two filters are fabricated using the silver micromachining technique with center frequencies at 1.05 and 1.35 GHz. The filters have a constant 3 dB bandwidth of 300 MHz (28.6% and 22.2%) and an insertion loss of 1.4‐1.7 dB. The low insertion loss and CMOS compatibility make the presented filters suitable candidates for radio frequency integrated circuits. (Some figures in this article are in colour only in the electronic version)