Quality Factor Tuning Research Articles

Low-Noise Quality Factor Tuning in Nondegenerate MEMS Gyroscope Without Dedicated Tuning Electrode

Quality factor tuning is attractive in degenerate (DE) and nondegenerate (NDE) MEMS gyros for drift suppression or shock and vibration immunity. This paper proposes three resistance-based Q-factor tuning approaches without dedicated electrodes for NDE gyro. The inherent sensing capacitance is utilized as a Q-tuning mechanism for low C-SWaP (cost, size, weight, and power). Routing traces on MEMS or ASIC chips as well as the input impedance of charge-sensitive-amplifier (CSA) are utilized as damping sources, respectively. The theoretical and experimental results indicate Q-tuning utilizing the CSA's input impedance doesn't deteriorate the gyro's noise floor (ARW = 0.01°/√h, BI = 0.12°/h). Large-scale Q-tuning using the regulation of polarization voltage reduces the sensing Q-factor from 38k to 3k. The gyro's settling time after shock is also reduced from 1.4s to 0.13s after Q-tuning. Besides, a frequency-independent fine Q-tuning using tail current regulation in Opam is proposed to correct the thermal variation of the sensing Q-factor. It improves the gyro's bias drift from 1.5°/s to 0.2°/s. This work presents a low C-SWaP Q-tuning solution for high-end industrial MEMS gyro.

A novel CMOS active inductor with high quality factor, high linearity and mutually independent tuning of inductance and quality factor

A novel CMOS active inductor (CAI) circuit topology is proposed. It consists of two identical gyrators, a voltage-controlled negative resistance cell (VCNRC) and a voltage-controlled current source (VCCS). And each gyrator is composed of a feedforward transistor, a feedback transistor, a cascaded transistor, a common-source (CS) transistor, and a feedback resistor. Moreover, these two gyrators are symmetric and form a differential structure. By above building blocks configuration and cooperation, the CAI can achieve following different performances. First, high quality factor (Q) can be achieved by a combination of the VCNRC, the cascaded transistors and the feedback resistors due to the decrease in the equivalent resistance losses; Secondly, high linearity can be realized by the additional CS transistors due to the compensation for the nonlinear drain current of the feedback transistors. Thirdly, mutually independent tuning of inductance (LCAI) and Q can be achieved by tuning three external bias voltage terminals respectively configured in the cascaded transistors, the VCNRC and the VCCS. The verification results show that at the frequency of 2.0 GHz, the peak Q can be tuned from 555 to 2780 with a large tuning range of 400.9 %, while the LCAI can be maintained within a small variation of only 0.9 %; on the other hand, LCAI at 2.0 GHz can also be tuned from 158 nH to 212 nH while the Q value has a variation of only 4.2 %; moreover, the CAI also is demonstrated to have inductance linearity as high as +0.17 dBm, and occupies a compact effective area of 43 μm × 52 μm. In addition, the output noise voltage at 2 GHz is 3.1 nV/√Hz, and both LCAI and Q values also exhibit good robustness against process corner and temperature variations. These comprehensive results highlight the CAI excellent performances in terms of size, Q value, linearity, mutually tunability of LCAI and Q, noise performance as well as the robustness against process and temperature variations.

High quality factor tuning fork resonators with various resonance frequencies

High quality factor tuning fork resonators with various resonance frequencies

High Quality Factor and Low Motional Impedance Aluminum Nitride Tuning Fork Resonators Vibrating in In-Plane Flexural Mode

This letter presents a piezoelectric tuning fork resonator vibrating in in-plane flexural mode with a high quality factor (Q) and low motional impedance. A novel double-sided actuating design is implemented based on unimorph structure with a 2.5- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thick AlN film as passive layer. The design significantly improves the Q and motional impedance compared with the conventional single-sided actuating design thanks to an increase of static capacitance without change of material interfaces. The proposed double-sided actuating device shows an excellent Q measured as 11272 with an extracted motional impedance of 7.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> in vacuum. The measured Q-pressure relationship shows that a vacuum level <100 Pa would ensure a sufficiently high Q value, which can be easily achieved through wafer-to-wafer bonding with getters in the future. Furthermore, the impact of AlN passive layer thickness on the resonator performance is analyzed. The proposed device would find applications in sensing fields as miniaturized and high-performance resonator-based solutions, such as gyroscopes, accelerometers and pressure sensors.

Thermal-piezoresistive pumping on double SiC layer resonator for effective quality factor tuning

Active techniques that pump energy into MEMS mechanical resonant devices to improve their performance have attracted great research attention. Herein, we introduce a new concept of bi-layered monolithic silicon carbide resonators utilizing thermal-piezoresistive pumping to boost the quality factor. The device operates based on the electrothermal actuation as a result of a superimposed alternating and direct voltages. The structural stress modulates the electrothermal force generated in the device through the piezoresistive effect. Due to the negative piezoresistive coefficient of the actuator, the mechanical vibration of the structure is fed from the DC bias applied to the structure. The unique design of the double SiC layer allow energy pumped into the system via the thermal-piezoresistive coupling in highly doped SiC nano-film, enabling the enhancement of effective quality factor up to 15.5 %, from 12,200 to 14,100. The change in frequency related to the applied power was measured to be less than 1 % of the designed value. The saturation threshold of the pumping effect was reached at an applied power of 0.18 W. This works provides an avenue to improve the effective quality factor in MEMS bridge structure resonators by the coupling of the thermal-piezoresistive pumping and electrothermal actuation.

Varactor-graphene-based multi-reconfigurable triplet filter with independent tuning of frequency and amplitude

In this paper, a multi-reconfigurable filter which consists of three identical varactor-graphene-loaded coaxial substrate integrated waveguide (SIW) resonators is presented. The center frequency and transmission amplitude of the proposed filter is independently reconfigurable by means of electrically controlling the values of the varactor capacitance and the graphene resistance, respectively. Tuners and their bias circuits are mounted on the surfaces of the SIW resonator to adjust the tuning of resonant frequency and unloaded quality factor, which enable to realize the frequency and amplitude of the presented multi-reconfigurable filter. In addition, the proposed filter applies a cascaded triplet topology to generate a transmission zero at the upper side in order to enhance skirt selectivity and out-of-band rejection. The circular shape of the resonator provides great flexibility and produces an additional compactness of the filter. The proposed multi-reconfigurable coaxial SIW filter is designed and fabricated, with high-Q varactors and graphene thin sheets as frequency and amplitude tuning elements, respectively, exhibiting the following reconfigurable characteristics: (a) a wide tuning range of 0.58–1.01 GHz with a constant 1 dB fractional bandwidth of 2 ± 0.2%. (b) A continuous tuning range of amplitude at any center frequency in the achievable frequency band. For instance, the proposed filter can be tuned with an amplitude range of 3.02–19.8 dB by varying the value of the graphene sheet resistance at 1.01 GHz. (c) Free combination of the arbitrary center frequency and attenuation level. The proposed filter with tunable filtering and attenuating responses has widely potential in reconfigurable wireless communication systems and radar systems due to its high integration and versatility.

Triple Mass Resonator for Electrostatic Quality Factor Tuning

In this paper, a triple mass resonator (TMR) with a high capability to independently tune both resonant frequency and quality factor (Q-factor) is reported. An additive oscillating structure is designed into a conventional dual-mass resonator to control the modal shape. The theoretical studies revealed that the amplitude ratio between the outer masses, which mainly determine the Q-factor through the anchor loss, is sensitive to both suspension and inner springs because of mode coupling, while the resonant frequency is only sensitive to the suspension spring. Through this mechanism, the quality factor related to the anchor loss, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{\mathrm {Anchor}}$ </tex-math></inline-formula> , can be adjusted by electrostatic tuning of the inner spring, while the resonant frequency keeps almost constant. On the other hand, the eigenfrequency could be significantly tuned by the electrostatic tuning of the suspension spring. The experimental results showed the Q-factor could be tuned as large as 19% by a DC bias of 15 V at the inner electrode, while the resonant frequency change was only as small as 162 ppm. In contrast, when the DC bias was applied to soften the suspension stiffness, the resonant frequency could be tuned as high as 7023 ppm with Q-factor change of 16%. [2021-0167]

Electronically tunable mixed mode universal filter employing grounded capacitors utilizing highly versatile VD-DVCC

PurposeThis paper aims to achieve two main objectives. First, to introduce to the literature a new versatile active building block, namely, voltage differencing differential voltage current conveyor (VD-DVCC) for analog signal processing applications. Second, to design a novel electronically tunable mixed-mode universal filter. The designed filter provides low-pass, high-pass, band-pass, band-reject and all-pass responses in voltage-mode (VM), current-mode (CM), trans-impedance-mode (TIM) and trans-admittance-mode (TAM).Design/methodology/approachThe proposed filter uses two VD-DVCCs, three resistors and two capacitors. All the capacitors used are grounded, which is advantageous from the monolithic integration point of view. The VD-DVCC is designed and validated in Cadence software using CMOS 0.18 µm process design kit from Silterra Malaysia at a supply voltage of ±1 V.FindingsThe proposed novel filter enjoys many attractive features including as follows: the ability to operate in all four modes, no requirement of capacitive matching, tunability of quality factor (Q) independent of pole frequency, availability of both inverting and non-inverting outputs for VM and TIM mode, high output impedance explicit current output for CM and TAM, no requirement for double/negative input signals (voltage/current) for response realization and low active and passive sensitivities. The filter is designed for a pole frequency of 5.305 MHz. The obtained results bear a close resemblance with the theoretical findings.Originality/valueThe proposed novel filter structure requires a minimum number of active and passive components and provides operation in all four operating modes. The filter will find application in structures of mixed-mode systems.

An Active Bandpass Filter for LTE/WLAN Applications Using Robust Active Inductors in Gallium Nitride

This brief demonstrates the performance of the first active bandpass filter to implement an active inductor in gallium nitride (GaN) technology. Fabrication of the filter and inductor was done using a 0.5 μm pHEMT GaN process with the system implemented on one 2 mm by 2 mm die. The tuning range of the active filter was measured to be 749 MHz at a centre frequency of 3.39 GHz with separate amplitude and quality factor tuning. An amplitude range for S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> was measured to be from -12.2 dB to 13.7 dB within the operating frequency range. Taking advantage of the active inductor's negative impedance the filter was able to produce a quality factor of 138. On-chip, the active inductor occupies an area of 350 μm by 175 μm compared to approximately 350 μm by 350 μm for their passive counterparts of similar inductance (a 50% decrease in size). The filter was designed for LTE/WLAN applications to demonstrate the capabilities of the active inductor.

Novel Electronically Tunable Biquadratic Mixed- Mode Universal Filter Capable of Operating in MISO and SIMO Configurations

In this paper, a novel electronically tunable biquadratic universal mixed-mode filter is presented. The filter is based on extra X current conveyor transconductance amplifier (EXCCTA), recently introduced by authors. The proposed filter employs two EXCCTAs, two capacitors, a switch, and four resistors. The filter can work in both multi-input-single-output (MISO) and single-input-multi-output (SIMO) configurations without change in its structure. The filter provides low-pass (LP), high-pass (HP), band-pass (BP), band-reject (BR) and all-pass (AP) responses in voltage-mode (VM), current-mode (CM), transimpedance-mode (TIM), and transadmittance-mode (TAM). The attractive features of the filter include (i) ability to operate in both MISO and SIMO configurations in all four modes, (ii) no requirement of capacitive matching, (iii) high output impedance in SIMO (CM & TAM) configuration, (iv) tunability of quality factor ( Q ) independent of natural frequency ( ) in MISO & SIMO configurations, (v) use of grounded capacitors in SIMO configuration, (vi) low output impedance for MISO (VM & TIM), (vii) high output impedance explicit current output for MISO (CM & TAM), and (viii) no requirement for double/negative input signals (voltage/current) in MISO configuration. The non-ideal gain and sensitivity analysis is also carried out to study the effects of process variations and passive components spread on filter performance. The filter is designed in Cadence Virtuoso using Silterra Malaysia 0.18µm PDK. The complete layout of the EXCCTA is designed and the parasitic extraction is done. The filter is tested at a supply voltage of ±1.25 V and the obtained results validate the theoretical findings.

Digitally-Controlled Bondwire Inductor with High Quality Factor and Wide Tuning Range

A tunable bondwire inductor (TBI) with high-quality factor and wide tuning range is presented. The proposed TBI is fabricated on a single chip by combining a single-pole four-throw (SP4T) switch integrated circuit (IC) and four bondwire inductors on a package substrate. The SP4T switch IC is fabricated using 180 nm silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) technology. The fabricated TBI chip exhibits a 521% tuning range of inductance from 1.77 to 11 nH at 0.1 GHz and a relatively high-quality factor. To the knowledge of the authors, the results of this work demonstrate the best combined performance of inductance tuning range and quality factor.

Actively tunable terahertz electromagnetically induced transparency analogue based on vanadium-oxide-assisted metamaterials

Recently, phase-change materials (PCMs) have drawn more attention due to the dynamically tunable optical properties. Here, we investigate the active control of electromagnetically induced transparency (EIT) analogue based on terahertz (THz) metamaterials integrated with vanadium oxide (VO2). Utilizing the insulator-to-metal transition of VO2, the amplitude of EIT peak can be actively modulated with a significant modulation depth. Meanwhile the group delay within the transparent window can also be dynamically tuned, achieving the active control of slow light effect. Furthermore, we also introduce independently tunable transparent peaks as well as group delay based on a double-peak EIT with good tuning performance. Finally, based on broadband EIT, the active tuning of quality factor of the EIT peak is also realized. This work introduces active EIT control with more degree of freedom by employing VO2, and can find potential applications in future wireless and ultrafast THz communication systems as multi-channel filters, switches, spacers, logic gates and modulators.

Quality factor tuning of micromechanical resonators via electrical dissipation

Sensitive capacitive transduction of micromechanical resonators can contribute significant electrical dissipation, which degrades the quality factor of the eigenmodes. We theoretically and experimentally demonstrate a scheme for isolating the electrical damping of a mechanical resonator due to Ohmic dissipation in the readout amplifier. The quality factor suppression arising from the amplifier is strongly dependent on the amplifier feedback resistance and parasitic capacitance. By studying the thermomechanical displacement noise spectrum of a doubly clamped micromechanical beam, we confirm that electrical dissipation tunes the actual, not effective, quality factor. Electrical dissipation is an important consideration in the design of sensitive capacitive displacement transducers, which are a key component in resonant sensors and oscillators.

New Signal Processing for Fast and Precise QEPAS Measurements.

Quartz-enhanced photoacoustic spectroscopy (QEPAS) gas sensors have been widely developed over the last decade. This technique takes the advantage of a high quality factor tuning fork to enable high-sensitivity and high-selectivity miniature gas sensors. Lock-in detection is classically used to measure the resonator amplitude, which is proportional to the gas concentration, but this technique is slow and leads to measurement drifts as it does not follow the resonator frequency drifts over temperature and pressure. This article presents a new QEPAS signal processing technique that allows faster and more stable measurements that will enable accurate and fast multigas sensors.

Novel current mode universal filter and dual-mode quadrature oscillator using VDCC and all grounded passive elements

ABSTRACTThe paper introduces a universal filter operating in current mode and a quadrature oscillator operating in current and voltage mode, employing Voltage Differencing Current Conveyor as active device along with all grounded passive elements. Apart from providing all five filter responses, i.e. low pass, high pass, band pass, band reject and all pass, the filter configuration also supports independent tunability of quality factor. The oscillator configuration can be easily realised with slight modifications in filter circuit, and features like low component count, use of grounded capacitors for supporting efficient integrated circuit implementation and availability of explicit current outputs are witnessed in both the devised networks. In the oscillator, network’s condition and frequency of oscillation can be independently tuned. For practical validation of the proposed network, PSPICE simulation software is used. The simulation results include two sets of outputs, one using CMOS (Complmentary Metal Oxide Semiconductor) implementation of Voltage Differencing Current Conveyor (VDCC) and another using off the shelf IC (Integrated Circuit) implementation of VDCC.

A fully reconfigurable bandpass-to-bandpass-with-embedded-stopband filter with an ultra-wide 0.09–1.41 GHz bandwidth tuning range

AbstractA varactor-based fully reconfigurable microstrip bandpass-to-bandpass-with-embedded-stopband filter is presented in this paper. This filter offers wide center frequency and bandwidth tuning flexibility under both bandpass mode and bandpass-with-embedded-stopband mode. The entire tuning ability is based on multiple mode resonator theory and external quality factor tuning structure for bandpass mode and the introduction of transmission zeros (TZs) for bandpass-with-embedded-stopband mode. Under the bandpass mode, the center frequency tuning range is 0.96–1.45 GHz and the bandwidth can be tuned from 0.09 to 1.41 GHz with a fixed center frequency at 1.22 GHz. Under bandpass-with-embedded-stopband mode, the center frequency and bandwidth can be tuned from 0.94 to 1.61 GHz and 0.2–0.33 GHz, respectively. Good agreements are shown between simulated and measured results.

Analytical design of MEMS variable capacitors based on shaped-finger comb-drives

A variable capacitor is one of the widely used components in radio frequency (RF) circuits. Variable capacitors can benefit from the microelectromechanical systems (MEMS) technology, to be equipped with attractive characteristics such as high quality factor and wide tuning range. One of the design goals for MEMS varactors has been to realize linear capacitance–voltage (C–V) characteristics, for which a design method is proposed in this paper, based on shaped-finger comb-drive actuators. The shaped-finger design method, originally developed for a tunable optical filter application by the author, is redeveloped in this work for a linear C–V varactor. Moreover, the conformal mapping method is employed in calculation of capacitances, making the whole design process more time-efficient, being almost all-analytical with the minimum usage of numerical analysis methods. Effects of sense capacitor finger shapes to the optimized drive capacitor finger shapes and the corresponding C–V characteristics are investigated as well. Variable capacitors with the shaped-finger design show linearity factor (LF)—defined as the maximum deviation from the perfect linear relationship—as good as 0.4%, enormously improved from that of the conventional constant-finger-gap devices (LF: 49.9%). Further probed by 3-D numerical analysis, the C–V characteristics of the designed variable capacitor show LF better than 2.62% in the case of constant-gap sense capacitors, and as good as 0.77% in the case of shaped-finger sense capacitors. Versatility of the design method is further demonstrated by presenting a varactor for linear resonant frequency–voltage (f–V) characteristics in voltage-controlled oscillator (VCO) applications. Finally, effects of etch bias, one of common fabrication imperfections, to the linearity of C–V characteristics are studied. The developed analytical design method with shaped fingers can find a wide range of applications where comb-drive actuators are used.

A fully reconfigurable bandpass‐to‐notch filter with wide bandwidth tuning range based on external quality factor tuning and multiple‐mode resonator

AbstractA fully reconfigurable microstrip bandpass‐to‐notch filter based on varactors is presented in this article. This filter offers wide center frequency and bandwidth tuning flexibility under bandpass mode and wide notch tuning range under notch mode. The entire tuning ability is based on multiple‐mode resonator (MMR) theory and tunable external quality factor for bandpass mode and the introduction of transmission zero (TZ) for notch mode. Under the bandpass mode, the center frequency tuning range is 0.9 to 1.42 GHz, and the bandwidth can be tuned from 0.09 to 1.44 GHz at a fixed center frequency 1.28 GHz. Under notch mode, the notch can be tuned from 0.98 to 2.02GHz. Good agreement can be observed between simulated and measured results.

Effective quality factor tuning mechanisms in micromechanical resonators

Quality factor (Q) is an important property of micro- and nano-electromechanical (MEM/NEM) resonators that underlie timing references, frequency sources, atomic force microscopes, gyroscopes, and mass sensors. Various methods have been utilized to tune the effective quality factor of MEM/NEM resonators, including external proportional feedback control, optical pumping, mechanical pumping, thermal-piezoresistive pumping, and parametric pumping. This work reviews these mechanisms and compares the effective Q tuning using a position-proportional and a velocity-proportional force expression. We further clarify the relationship between the mechanical Q, the effective Q, and the thermomechanical noise of a resonator. We finally show that parametric pumping and thermal-piezoresistive pumping enhance the effective Q of a micromechanical resonator by experimentally studying the thermomechanical noise spectrum of a device subjected to both techniques.

Nonlinearity modulation based multiple Fano resonance and multi-spectral switching in a nanoplasmonic waveguide-coupled cavity system

Dual and multiple asymmetric Fano resonance are theoretically explored in a subwavelength plasmonic cavity-coupled waveguide system incorporated with a third order Kerr nonlinear medium. The degree of asymmetry and the number of multiple resonances are controlled by an external pump beam which modulates the Kerr permittivity thereby dictating the resonant behavior. Electromagnetically induced transparency in plasmonic systems, referred to as plasmon induced transparency, is a special case of Fano resonance and plays a key role for the occurrence of multiple Fano excitations. Plasmon induced transparency appears as induced reflectance dips when analyzed in reflection mode. Though geometrical dependency of dual and multiple Fano effect is demonstrated, the main interest and importance is focused on the generation and manipulation of multiple Fano resonances by intensity modulation of the pump beam and its application in multispectral switching and quality factor tuning at a fixed operating frequency.