Tunable Inductor Research Articles

End-to-end deep learning pipeline for microwave kinetic inductance detector resonator identification and tuning

We present the development of a machine learning-based pipeline to fully automate the calibration of the frequency comb used to read out optical/IR microwave kinetic inductance detector (MKID) arrays. This process involves determining the resonant frequency and optimal drive power of every pixel (i.e., resonator) in the array, which is typically done manually. Modern optical/IR MKID arrays, such as the DARK-Speckle Near-Infrared Energy-Resolving Superconducting Spectrophotometer and the MKID exoplanet camera, contain 10 to 20,000 pixels, making the calibration process extremely time-consuming; each 2000-pixel feedline requires 4 to 6 h of manual tuning. We present a pipeline that uses a single convolutional neural network to perform both resonator identification and tuning simultaneously. We find that our pipeline has performance equal to that of the manual tuning process and requires just 12 min of computational time per feedline.

Magnetoelectric materials and devices

Over the past few decades, magnetoelectric (ME) materials and devices have been investigated extensively, which is one of the most interesting research topics since the revival of multiferroic laminates with large ME coupling coefficients. The existence of two or more ferroic properties in the ME systems plays key roles in the next generation of novel multifunctional devices. Strong ME coupling has been demonstrated in various ME systems, including single-phase bulk or thin-film materials and bulk or thin-film composites such as piezoelectric/magnetostrictive heterostructures. Based on the coupling mechanisms, a variety of device applications have attracted ever-increasing attention, such as magnetic field sensors, voltage tunable inductors, mechanical ME antennas, which are compact, lightweight, and power-efficient. These novel ME materials and devices provide great opportunities for next-generation magnetic field sensing, communication systems, spintronics, nonvolatile memory applications, etc. In this paper, we try to summarize the most recent progress on ME materials, phenomena, and devices in the past few years, with emphasis on thin-film composite materials and devices. Some unsolved questions and future directions where the community could head for are also provided.

An Ultra-Compact Multi-Band VCO Achieving − 196 dB FoMA with Single-Ended Tunable Active Inductor

This paper presents a wide tuning-range LC-tank voltage controlled oscillator (VCO). To perform large frequency tuning range, the proposed circuit topology uses a tunable active inductor (TAI) for the coarse frequency tuning, while the fine-tuning is controlled only by a MOS varactor. The TAI design is based on toggling varactor arrays by which four channels are able to be selected for multi-band applications. The proposed VCO is designed in 90-nm CMOS process. Simulation results show that the VCO can operate from 760 MHz to 4.370 GHz representing an FTR of 140.74%, with a tuning gain Kvco from 654 to 1882 MHz/V. The achieved phase noise is lower than − 105 dBc/Hz at an offset frequency of 1 MHz from the carrier tuned to 2.52 GHz. The VCO core circuit draws 3.3 mA from a 1V voltage supply and occupies a small active area of (45 × 37) μm2. The fully implemented VCO provides excellent performances such as attractive FOMA value of − 196 dBc/Hz.

A Quadrature Digital Power Amplifier With Hybrid Doherty and Impedance Boosting for Complex Domain Power Back-Off Efficiency Enhancement

A quadrature digital power amplifier (PA) with hybrid Doherty and impedance boosting (HDIB) technique is presented for deep power back-off (PBO) efficiency enhancement in the complex domain. Less power-combining ways and dc power supplies are required for proposed PA comparing to previously reported works with deep PBO efficiency enhancement. A reconfigurable matching network (RMN) based on a novel reconfigurable transformer is proposed with more freedom to achieve a flexible load impedance tuning range of the sub-PAs. The characteristics of the reconfigurable transformer based on tunable inductors are analyzed. Efficiency enhancement is achieved at 3-/6-/9-/12-/15-dB PBOs without any supply switching or PA short-switches. The PA is fabricated in 40-nm CMOS technology with a core size of 0.83 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Operating at 2.3-3.4 GHz, it introduces 24.2-dBm peak P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> with 38.5% peak drain efficiency (DE) at 2.8 GHz. It achieves 38.5%/29.6%/18.4% at 2.8 GHz and 34.7%/26.6%/17.8% DE at 3.3 GHz for 0-/6-/12-dB PBO, 39.3%/29.5%/14.9% at 2.8 GHz, and 35.3%/27.9%/15.9% DE at 3.3 GHz for 3-/9-/15-dB PBO, respectively. For 10-MHz 256-QAM modulation signal, it delivers 16.22-/15.50-dBm average P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> with EVM of -32.3/-33.0 dB, average DE of 24.6%/22.7%, and ACLR of -33.20/-31.54 dBc at 2.8/3.3 GHz, respectively. For 20-MHz 64 QAM modulation signal, it exhibits 16.42-/15.52-dBm average P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> with EVM of -29.1/-29.3 dB, average DE of 24.9%/22.78%, and ACLR of -30.78/-30.74 dBc at 2.8/3.3 GHz, respectively.

Wideband Tunable Radio Frequency Integrated Circuit Inductors Integrated With Domain-Patterned Permalloy

For wideband frequency-agile radio frequency integrated circuits (RFIC), tunable components are essential. It has been a great challenge in RF electronics to utilize a magnetic tunable inductor for ultra wideband applications. This paper demonstrates an electrically tunable RF inductor encompassing a broad range of frequencies from 4 GHz to 20 GHz. This is achieved by integrating domain patterned permalloy with various thicknesses like 20 nm, 60 nm and 92 nm. There is a performance boost of the inductor and also tunable inductor is achieved by applying DC current. Experimental results show that amongst all the permalloy patterns, 11 m x 13 m provides the highest inductance tunability of 15.8% at 20 GHz for 60 nm patterns, 10.8% at 15.1 GHz for 92 nm and 4.3% at 15.7 GHz for 20 nm. This is the highest inductance tunability obtained so far for spiral inductors integrated with 60 nm permalloy patterns using the dc bias method. The 15.8%, 10.8% and 4.3% inductance tunability provides 8%, 5.7% and 2.1% frequency tuning correspondingly.

Theoretical model and tunability optimization of magnetoelectric voltage tunable inductor

Magnetoelectric voltage tunable inductor (ME-VTI) realizes the modulation of electric field to inductance based on magnetoelectric effect. Compared with other adjustable inductors, it has the advantages of low energy consumption, small volume, large tunability and continuity. However, previous reports on ME-VTI mainly focused on structure and magnetostrictive materials, resulting in the complexity of inductor structure and slight improvement of tunability. This study focuses on the influence of field-induced strain in piezoelectric materials on inductance tunability by constructing a theoretical model. The magnetoelectric laminate of Metglas/ PMN-PT single crystal /Metglas is employed as a magnetic core to design ME-VTI. The tunability is as high as 680% at 1 kHz, which is over 2.4 times larger than that of the Metglas/PZT/Metglas magnetic core. The quality factor of the PMN-PT based ME laminate reaches 15.6, which is 2.8 times higher than that of the PZT-based one. The proposed PMN-PT based ME-VTI provides an alternative approach for developing the integrated and miniaturized devices, and has an important prospect of application in the field of power electronics.

A Switched Tunable Inductor Based on Magnetic Flux Linkage Modification

An on-chip switched tunable inductor based on magnetic flux linkage modification is proposed. The magnetic flux linkage was adjusted through an auxiliary coil that was connected to a flip-flop in parallel with a MOS switch. The inductance was monotonically tuned by applying MOS gate voltages, which had a broad tuning range of 1.32–2.03 nH (42.4%) at 8 GHz. A high quality factor of 61.6 at 8 GHz was achieved because the flip-flop provided negative resistance.

Probabilistic Analysis of Tunability of Step-Edge Josephson Junction Arrays’ Inductance in HTS Microwave Metamaterials

Josephson junction in superconductor circuits and metamaterials is modeled as a tunable inductance. The Josephson inductance is tunable by the bias current passing through it and can be tuned from an initial value to a very large value as much as one can push bias current near the critical current but not exceeding it. Tunability by bias current allows design of programmable metamaterials with flexible functions in microwave regime. In High-Temperature Superconductivity (HTS) tunable metamaterials, Josephson junctions should be used in series configuration to give usable tunable inductance. Each Step-Edge Josephson junction (SEJs) in HTS has a critical current that is dependent on its geometrical dimensions such as the width of the junction. In a practical fabrication process, the widths and critical currents will be distributed with a Gaussian Probability Distribution Function (PDF). This will decrease the tunability of the Josephson inductance of the array. We have calculated the tunability of an array with defined critical current distribution, in terms of probabilistic analysis.

Improving electric field controlled magnetism of micron-scale-thickness Fe71Ga17B12 film on Pb(Mg1/3Nb2/3)0.7O3-PbTi0.3O3 by multilayer preparation method

Enhancing electric field controlled magnetism of micron-scale-thickness ferromagnetic film is of great significance to improve the performance of magnetoelectric (ME) sensors, ME tunable inductors and other ME devices. In order to achieve above purpose, multilayer preparation method was proposed and validated by experiment studies on multilayer (Cu(10 nm)/(FeGaB(100 nm)/Cu(5 nm))10) and monolayer (Cu(10 nm)/FeGaB (1000 nm)/Cu(5 nm)) samples, respectively. The results show the electric field controlled magnetism could be enhanced obviously by the multilayer preparation method. Meanwhile, the finite element simulation model was established to analyze possible causes for the improvement of electric field controlled magnetism in multilayer sample. The model revealed that multilayer preparation can reduce the in-plane demagnetizing factor and increase the internal magnetic field of the magnetic materials, thus enhancing electric field controlled magnetism. This work is conducive to the development of micron-scale-thickness films in electric field control of magnetism, which contributes to the application of ferroelectric/ferromagnetic heterostructures in ME devices.

Electric Field Control of Magnetic Permeability in Co-Fired Laminate Magnetoelectric Composites: A Phase-Field Study for Voltage Tunable Inductor Applications.

Control of magnetic permeability through electric field in magnetoelectric materials promises to create novel voltage tunable inductors (VTIs). VTIs synthesized using co-fired ceramic processing exhibit many advantages over traditional epoxy bonding method, but the internal residual stress in co-fired VTIs resulting from thermal expansion mismatch hinders a full exploitation of the tunability of permeability. To find the optimal condition for high tunability of co-fired VTIs, domain-level phase field modeling and computer simulation are employed to study co-fired magnetoelectric composites comprising NiZn ferrite and PZT. Two key factors important toward increasing the inductor tunability are systematically investigated: intrinsic magnetocrystalline anisotropy of the ferrite material and internal residual stress caused by the co-firing process. The simulations indicate that in order to achieve a large tunability, the tuned permeability should be confined within the linear region of the reciprocal of susceptibility and stress. Additionally, both magnetocrystalline anisotropy and residual stress should be as small as possible. These results provide a design strategy for realizing high-tunability co-fired VTIs.

Controlling the proximity effect in a Co/Nb multilayer: the properties of electronic transport.

We present both theoretical and experimental investigations of the proximity effect in a stack-like superconductor/ferromagnetic (S/F) superlattice, where ferromagnetic layers with different thicknesses and coercive fields are made of Co. Calculations based on the Usadel equations allow us to find the conditions at which switching from the parallel to the antiparallel alignment of the neighboring F-layers leads to a significant change of the superconducting order parameter in superconductive thin films. We experimentally study the transport properties of a lithographically patterned Nb/Co multilayer. We observe that the resistive transition of the multilayer structure has multiple steps, which we attribute to the transition of individual superconductive layers with the critical temperature, Tc, depending on the local magnetization orientation of the neighboring F-layers. We argue that such superlattices can be used as tunable kinetic inductors designed for artificial neural networks representing the information in a “current domain”.

Nonlinearity in a Medical Ultrasound Probe Under High Excitation Voltage

Tissue harmonic imaging is often the preferred ultrasound imaging modality due to its ability to suppress reverberations. The method requires good control of the transmit stage of the ultrasound scanner, as harmonics in the transmitted ultrasound pulses will interfere with the harmonics generated in the tissue during nonlinear propagation, degrading image quality. In this study, a medical ultrasound probe used in tissue harmonic imaging was experimentally characterized for transmitted second-harmonic distortion to identify and compare the sources of nonlinear distortion in the probe and transmit electronics. The system was tested up to amplitudes above what is found during conventional operation, pushing the system to the limits in order to investigate the phenomenon. Under these conditions, second-harmonic levels up to -20 dB relative to the fundamental frequency were found in the ultrasound pulses transmitted from the probe. The transmit stage consists of high-voltage transmit electronics, cable, tuning inductors, and the acoustic stack. The contribution from the different stages in the ultrasound transmit chain was quantified by separating and measuring at different positions. Nonlinearities in the acoustic transducer stack were identified as the dominating source for second harmonics in the transmitted ultrasound pulses. Contribution from other components, e.g., transmit electronics and cable and tuning circuitry, were found to be negligible compared with that from the acoustic stack. Investigation of the stack's electrical impedance at different driving voltages revealed that the impedance changes significantly as a function of excitation voltage. The second-harmonic peak in the transmitted pulses can be explained by this nonlinear electrical impedance distorting the driving voltage and current.

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.

Tunable active inductor based VCO and BPF in a single integrated design for wireless applications in 90 nm CMOS process

AbstractThis article proposes a tunable active inductor (AI)‐based voltage‐controlled oscillator (VCO) andbandpass filters (BPF) on a single integrated design in 90 nm CMOS process for wireless applications. By exploiting component sharing technique through single pole double throws switching method, a common AI is shared between VCO and BPFs. As the passive inductor is replaced by the AI and shared, silicon area consumption is significantly reduced. Transforming the inductor in tunable mode benefits to eliminate MOS varactors for tuning purposes; one step forward to reduce silicon area consumption. Operating as VCO, its frequency ranges from 1.93 to 6.22 GHz (tuning scope is 105%) for tuning voltage of 0.2 ∼ 1 V. The DC power consumption varies from 1.83 to 3.84 mW, and differential output power is 3.39 to − 2.99 dBm. The phase noise varies from − 81.32 to − 76.89 dBc/Hz, and the figure of merit has a value of − 148.74 dBc/Hz at 5.03 GHz frequency. While acting as BPF, two approaches of center frequency tuning are applied. The voltage tuning yields center frequency of 8.43 ∼ 7.08 GHz along with the maximum gain of 10.29 dB at 7.81 GHz. The capacitive tuning outputs frequency tuning of 7.64 ∼ 7.06 GHz. The BPF consumes DC power of 2.56 to 2.27 mW (voltage tuning) and 2.40 mW (capacitive tuning). The proposed design occupies a layout area of 1215.6 μm2. All the simulations have been performed considering parasitic elements evolved from the extraction of layout. Finally, a quantitative comparison and justification of the proposed design are made with respect to other published works.

Design and Analysis of Varactorless 65 nm MMW Voltage Controlled Oscillator

In this work a novel inductive tuning technique for millimeter wave (mmw) applications is presented. Fine frequency tuning is performed using a transformer. For the LC tanks inductive element, transformer is used. To tune the VCO MOS switch is placed at center tapping of the secondary coil of the transformer. The simulation shows that by changing the operating condition of MOS switch frequency band from 59.1 GHz to 64.6 GHz is obtained. The proposed 60 GHz VCO is designed using UMC 65 nm CMOS single Poly eight Metal (1P8M) Technology. Obtained Frequency Tuning Range (FTR) is 8.89% and the corresponding phase noise variation is from − 112.4 dBc/Hz to − 115.9 dBc/Hz at 10 MHz offset from the carrier. The worst phase noise value is − 112.4 dBc/Hz which is obtained at 0.3 V tuning voltage. For 0.8 V supply voltage 7.44 mW of power is dissipated. And the calculated Figure of Merit (FOM) for whole FTR, ranges from − 179.89 dBc/Hz to − 182.62 dBc/Hz.

Ultraminiature Circularly Polarized RFID Antenna Inspired by Crossed Split-Ring Resonator

This article presents a novel ultraminiature circularly polarized (CP) antenna inspired by crossed split-ring resonators (SRRs), and its derivative forms with frequency and polarization re-configurability for radio frequency identification (RFID) applications. A novel resonator structure with two metal–insulator–metal (MIM) capacitors that is inspired by vertical SRR (VSRR) is first proposed, which could be easily miniaturized while achieving a reasonable high radiation gain. Two crossed dual-capacitance ring resonators (C-DRRs), which can be equivalent to two crossed magnetic dipoles, are then arranged perpendicularly and excited simultaneously with an SMA connector. Only an aluminum ground sheet, metallic screws, and a thin low-cost dielectric PCB board are used, where the dielectric loss is substantially minimized. This SRR-inspired CP antenna, as well as its frequency and polarization reconfigurable derivative by introducing a mechanically tunable inductor or using electrically controllable components, are analyzed and experimentally demonstrated, respectively. The developed antenna achieves an electrically small size of 0.135 $\lambda _{0}\,\,\times $ 0.135 $\lambda _{0}\,\,\times $ 0.045 $\lambda _{0}$ , and its size is considerably smaller than other reported compact RFID reader antennas. The measured −10 dB bandwidth, peak gain, and radiation efficiency are 3.1% (900–928 MHz), 5.51 dBic, and 86.5%, respectively, which agree perfectly with the simulation. They demonstrate superior advantages in terms of ultracompact size, low-cost, wide axial ratio (AR) beam-width, high efficiency, and easy fabrication/assembling for RFID-related applications.

Fabrication and Characterization of Ferrofluidic-Based Wire-Wound and Wire-Bonded Type Inductor for Continuous RF Tunable Inductor

This paper reports on the novel implementation of a tunable solenoid inductor using the fluid-based inductance varying technique. The concept utilized material permeability variation that directly modifies self-induced magnetic flow density inside the coil, which in turn creates a variation of the inductance value. The core is formed by a channel which allows the circulation of a liquid through it. The liquid proposed for this technique has ferromagnetic behavior, called ferrofluid, with a magnetic permeability higher than unity. To evaluate the proposed technique, two different types of solenoid inductor were designed, simulated and measured. The two structures are wire-wound and wire bond solenoid inductors. The structures are simulated in a 3D EM analysis tool followed by fabrication, test and measurement. The wire-bonded-based inductor showed a quality factor of 12.7 at 310 MHz, with 81% tuning ratio, by using ferrofluid EMG 901. The wire-wound-based inductor showed that the maximum tuning ratio is 90.6% with quality factor 31.3 at 300 MHz for ferro fluidic EMG 901. The maximum measured tuning ranges were equal to 83.5% and 56.2% for the wire-wound type and the wire-bonded one, respectively. The measurement results for the proposed technique showed a very high tuning range, as well as high quality factor and continuous tunability.

High-Power Magnetoelectric Voltage Tunable Inductors

Magnetoelectric voltage tunable inductors (VTIs) offer a new paradigm for power electronics circuit design. Here, air-gapped VTIs are demonstrated exhibiting a large inductance tunability of 220% with applied fields under 20 kVcm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and operational stability up to 5 MHz that covers the full frequency range of the state-of-the-art power electronics. The design of air-gapped VTI comprises of two C-shaped ferrite cores, one permeability-variable magnetic flux valve (MFV) in between C-shaped cores, and slotted air gap between cores and MFV. The tunability of VTIs is achieved through the electric field modulation of permeability in the MFV based on the magnetoelectric effect. There is a tradeoff between the tunability and saturation current. The introduction of air gap significantly reduces the tunability but provides methodology toward increasing the saturation current and power handling capability due to the increased reluctance. The inductance and tunability reduces by 50% with increase in the air-gap width from 0.07 mm to infinity (condition with no C-shaped cores). Phase field simulations demonstrate that the air gap affects the magnetization, permeability, and tunability of VTIs by tailoring the demagnetization field that further influences the magnetic domain rotation process. VTIs with increased frequency range and saturation current will strengthen the continued development of tunable power electronics.

Experimental validation of piezoelectric shunt tuning with residual mode correction: Damping of plate-like structures

The effective vibration mitigation properties of piezoceramic patches with inductive-resistive shunts are investigated experimentally. A shunt tuning method is proposed, in which a consistent correction for the influence from residual vibration modes is included by an effective modal capacitance, evaluated from measured charge and voltage amplitudes in short- and open-circuit conditions, respectively. The robustness of the proposed method is verified experimentally for both a free beam and a free plate structure with four shunted piezoceramic patch pairs. A stable and fully passive inductor is produced by winding a copper wire around a magnetic core, which requires precise inductance tuning to determine the final number of turns. It is demonstrated that the effective modal capacitance interpolates consistently between the blocked and static capacitances, commonly used for single-mode tuning of piezoelectric inductive-resistive shunts. By imposing pseudo-random vibrations, the piezoelectric current and voltage signals are measured and evaluated by their frequency response functions. Spectrum peak values determine the apparent short-circuit charge to open-circuit voltage ratio for each shunt, which directly determines the shunt components by explicit tuning formulas. Good correlation between numerical and experimental results are obtained for the free beam, while for the free plate experiment effective multi-mode shunt tuning is obtained by a modified effective electromechanical coupling coefficient.

A Digitally Programmable Wide Tuning-Range Active Transformer for Inductorless BPF and DCOs

In this brief, a programmable active transformer based on cascode grounded active inductor is proposed. The coarse tuning is achieved by programming the digitally controlled current mirrors (DCCMs), while the fine tuning is obtained by an analog voltage applied to the varactors. A wide tuning range, high-Q LC-oscillator and an active band-pass filter (BPF) are demonstrated using the proposed active transformer. The circuits are designed and simulated in a 0.13 $\mu \text{m}$ standard CMOS technology. An inductance tuning range from 7.91 nH to 4.4 $\mu \text{H}$ is achieved for the active transformer. A frequency range from 0.25 GHz to 5.3 GHz and a quality factor of 24697 are obtained at the frequency of 2.46 GHz. Using 6-bit digital code, the output frequency of inductorless oscillator is programmed from 215 MHz to 2.85 GHz. For the BPF, a central frequency from 170 MHz to 2.9 GHz is obtained. A power from 21.96 mW to 28.15 mW using a supply voltage of 1 V is consumed. The proposed active transformer occupies an area of 0.004 ${mm^{2}}$ . A prototype of inductorless oscillator is implemented by CD4007UBE ICs to verify the concept.