Electronically Tunable Research Articles

Correction: Low-Frequency Resistorless Electronically Tunable Quadrature Oscillator Based on an EX-CCCII

Correction: Low-Frequency Resistorless Electronically Tunable Quadrature Oscillator Based on an EX-CCCII

Ionic Chiral Ferrocene Doped Cholesteric Liquid Crystal with Electronically Tunable Reflective Bandwidth performance.

Cholesteric liquid crystals (CLC) were widely used in optical devices as one-dimensional photonic crystals. However, their reflective bands cannot be adjusted, which limits their wide application in many fields. In this paper, a series of ionic chiral ferrocene derivatives (CD-Fc+) as dopants were designed and prepared, and their doping into negative liquid crystal matrix was investigated to develop cholesteric response liquid crystal composites with electrically tunable reflective bands. The effects of electric field frequency, voltage, retention time of voltage and molecular structure on the broadening of reflection bandwidth were investigated in detail.

Synthesis of High-Input Impedance Electronically Tunable Voltage-Mode Second-Order Low-Pass, Band-Pass, and High-Pass Filters Based on LT1228 Integrated Circuits

This paper introduces two new high-input impedance electronically tunable voltage-mode (VM) multifunction second-order architectures with band-pass (BP), low-pass (LP), and high-pass (HP) filters. Both proposed architectures have one input and five outputs, implemented employing three commercial LT1228 integrated circuits (ICs), two grounded capacitors, and five resistors. Both proposed architectures also feature one high-impedance input port and three low-impedance output ports for easy connection to other VM configurations without the need for VM buffers. The two proposed VM LT1228-based second-order multifunction filters simultaneously provide BP, LP, and HP filter transfer functions at Vo1, Vo2, and Vo3 output terminals. The pole angular frequencies and the quality factors of the two proposed VM LT1228-based second-order multifunction filters can be electronically and orthogonally adjusted by the bias currents from their corresponding commercial LT1228 ICs, and can be independently adjusted in special cases. In addition, both proposed VM LT1228-based second-order multifunction filters have two independent gain-controlled BP and LP filter transfer functions at Vo4 and Vo5 output terminals, respectively. Based on the three commercial LT1228 ICs and several passive components, simulations and experimental measurements are provided to verify the theoretical predictions and demonstrate the performance of the two proposed high-input impedance electronically tunable VM LT1228-based second-order multifunction filters. The measured input 1-dB power gain compression point (P1dB), third-order IMD (IMD3), third-order intercept (TOI) point, and spurious-free dynamic range (SFDR) of the first proposed filter were -7.1 dBm, -48.84 dBc, 4.133 dBm, and 45.02 dBc, respectively. The measured input P1dB, IMD3, TOI, and SFDR of the second proposed filter were -7 dBm, -49.65 dBc, 4.316 dBm, and 45.88 dBc, respectively. Both proposed filters use a topology synthesis method based on the VM second-order non-inverting/inverting HP filter transfer functions to generate the BP, LP and HP filter transfer functions simultaneously, making them suitable for applications in three-way crossover networks.

Electronic Tunability and Cancellation of Serial Losses in Wire Coils.

This work presents a novel methodology to adjust the inductance of real coils (electronically) and to cancel out serial losses (up to tens or even hundreds of Ohms in practice) electronically. This is important in various fields of electromagnetic sensors (inductive sensors), energy harvesting, measurement and especially in the instrumentation of various devices. State-of-the-art methods do not solve the problem of cancellation of real serial resistance, which is the most important parasitic feature in low- and middle-frequency bands. In this case, the employment of serial negative resistance is not possible due to stability issues. To solve this issue, two solutions allowing the cancellation of serial resistance by the value of the passive element and an electronically adjustable parameter are introduced. The operational ranges are between 0.1 and 1 mH and 0.1 and 10 mH, valid in bandwidths from hundreds of Hz up to hundreds of kHz. The proposed concepts are experimentally tested in two applications: an electronically tunable oscillator of LC type and an electronically tunable band-pass RLC filter. The presented methodology offers significant improvements in the process of circuit design employing inductors and can be beneficially used for on-chip design, where serial resistance issues can be very significant.

New resistor-less tunable floating and grounded FDNR simulators

ABSTRACT This article proposes new electronically tunable simulation configurations of synthetic grounded and floating frequency-dependent negative resistances (FDNRs) without using any resistances. The presented simulators have been realised by using two voltage differencing transconductance amplifiers (VDTAs) along with two capacitances. As per the knowledge of the authors, the depicted VDTA-based simulator circuits are the most compact configurations as compared to any other VDTA-based pure FDNR simulator reported so far. The circuits possess the feature of electronic tunability which means that the realised FDNR value can be controlled by using bias currents of employed VDTAs. Moreover, the reported structures simulate ideal FDNR behaviour without any requirement of fulfiling the parameter-related conditions. An analysis has been presented and discussed to find the behaviour of the presented circuits under non-ideal effects. The operation of the simulated FDNRs has been checked by constructing higher-order CDR filters. The working of the designed circuits has been shown through the simulation results generated using PSPICE with 0.18 um CMOS technology. Finally, the experimental results using commercial IC have been discussed.

Electronic Tuneable Grounded and Floating FDNR using FTFNTA

ABSTRACT In this manuscript, an electronically tunable resistor-less grounded and floating FDNR (Frequency-Dependent Negative Resistance) is presented. The proposed circuit uses two FTFNTAs (Four Terminal Floating Nullor Transconductance Amplifier) and three capacitors for the design of floating FDNR; while only one FTFNTA and two capacitors are used for the design of grounded FDNR. The electronic tunability is achieved by altering the bias current of the FTFNTA. The workability of the proposed FDNR is demonstrated through the implementation of 4th order Butterworth band pass filter (BPF) and 2nd order low pass filter (LPF). The PSPICE simulation results are included to verify the theoretical interpretation.

New CMOS Realizable All-Pass Frequency Selective Structures

This paper deals with the realization of two first-order all-pass filter (APF) structures. First structure provides both inverting and non-inverting voltage-mode APF functions. This structure utilizes one differential difference dual-[Formula: see text] second generation current conveyor (DD-DXCCII) without [Formula: see text] terminals, one active resistor and one capacitor only. The use of active resistor makes the proposed structure electronically tunable. Therefore, the attributes such as use of single DD-DXCCII without [Formula: see text] terminals and electronic tunability make the proposed structure simple and attractive. Conversely, second proposed circuit structure of first-order APF enriches the quality of this paper as both inverting and non-inverting APF functions in both voltage and current forms are available simultaneously within the same circuit structure. This circuit is realized with the help of one DD-DXCCII, three active resistors and one capacitor. The second circuit structure also enjoys gain controllability feature along with electronically tunable pole frequency that proves to be very essential in many of the applications. Additionally, the proposed APF structures provide the demanding feature of cascadability along with chip fabrication support. Furthermore, the performance of proposed circuits is less affected by the non-idealities and parasitic of DD-DXCCII. PSPICE simulations are provided to validate the theoretical presumptions.

Frontispiece: BIAN‐NHC Ligands in Transition‐Metal‐Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N‐Heterocyclic Carbenes?

Frontispiece: BIAN‐NHC Ligands in Transition‐Metal‐Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N‐Heterocyclic Carbenes?

BIAN-NHC Ligands in Transition-Metal-Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N-Heterocyclic Carbenes?

The discovery of NHCs (NHC = N-heterocyclic carbenes) as ancillary ligands in transition-metal-catalysis ranks as one of the most important developments in synthesis and catalysis. It is now well-recognized that the strong σ-donating properties of NHCs along with the ease of scaffold modification and a steric shielding of the N-wingtip substituents around the metal center enable dramatic improvements in catalytic processes, including the discovery of reactions that are not possible using other ancillary ligands. In this context, although the classical NHCs based on imidazolylidene and imidazolinylidene ring systems are now well-established, recently tremendous progress has been made in the development and catalytic applications of BIAN-NHC (BIAN = bis(imino)acenaphthene) class of ligands. The enhanced reactivity of BIAN-NHCs is a direct result of the combination of electronic and steric properties that collectively allow for a major expansion of the scope of catalytic processes that can be accomplished using NHCs. BIAN-NHC ligands take advantage of (1) the stronger σ-donation, (2) lower lying LUMO orbitals, (3) the presence of an extended π-system, (4) the rigid backbone that pushes the N-wingtip substituents closer to the metal center by buttressing effect, thus resulting in a significantly improved control of the catalytic center and enhanced air-stability of BIAN-NHC-metal complexes at low oxidation state. Acenaphthoquinone as a precursor enables facile scaffold modification, including for the first time the high yielding synthesis of unsymmetrical NHCs with unique catalytic properties. Overall, this results in a highly attractive, easily accessible class of ligands that bring major advances and emerge as a leading practical alternative to classical NHCs in various aspects of catalysis, cross-coupling and C-H activation endeavors.

Electronically Tunable ACO Based Fuzzy FOPID Controller for Effective Speed Control of Electric Vehicle

The phenomenal growth of the Electric Vehicle (EV) technology demands efficient and intelligent control strategies for the propulsion system. In this work, a novel fuzzy fractional order PID (FOPID) controller using Ant Colony Optimization (ACO) algorithm has been proposed to control EV speed effectively. The controller parameters and the fuzzy logic controller's membership functions are tuned and updated in real-time using the multi-objective ACO technique. The proposed controller's speed tracking performance is verified using the new European driving cycle (NEDC) test in the MATLAB-Simulink platform. The proposed controller outperforms the ACO-based fuzzy integer-order PID (IOPID), FOPID, and traditional IOPID controllers. The sensitivity analysis confirms the robustness of the proposed controller for varying parameters of the EV model. The stabilization of EV speed in the presence of external disturbance is also confirmed. In the proposed work, an attempt is made to analyze the system's stability using Matignon's theorem, considering the linearized EV model. The proposed controller gives optimum speed tracking performance compared to the Genetic Algorithm (GA) and the Particle Swarm Optimization (PSO) based fuzzy FOPID controllers. Additionally, the optimized fuzzy FOPID controller is realized using a second-generation current conveyor with extra inputs (EX-CCII) and fractional-order capacitors with electronic tunability. The controller circuit's performance evaluation is carried out in the Cadence Analog Design Environment using GPDK 180 nm CMOS process.

A New Extremely Low Power Temperature Insensitive Electronically Tunable VCII-Based Grounded Capacitance Multiplier

In this brief, a new circuit topology to realize an electronically tunable grounded capacitor multiplier with extremely low power consumption and low supply voltage requirement is investigated. The proposed circuit uses an electronically tunable second generation voltage conveyor (VCII) and a single floating capacitor. Owing to the translinear principle, current gain of VCII is varied through a control current and, as a result, the value of simulated capacitor is also varied. Favorably the obtained gain is temperature insensitive. Both of the required supply voltage and control currents are very low because all transistors are biased in subthreshold region: therefore, electronic tunability is achieved while the power consumption is kept at very low value. In addition, the circuit realization is very simple since only twelve transistors are required. Simulation results, performed at schematic level in 0.18 $\mu \text{m}$ CMOS technology and supply voltage of ±0.3V, are presented. It is shown that a multiplication factor from 1 to 100 is possible while the power consumption varies from 10 nW to 67 nW.

Electronically Tunable VDTA-Based Multi-function Inverse Filter

An electronically tunable realization of voltage differencing transconductance amplifier (VDTA)-based multi-function inverse filter circuit is proposed in this letter. Various responses namely inverse low pass, inverse high pass, inverse band pass, and inverse band reject are achieved through switch settings. The proposed circuit uses only grounded capacitors and adds electronic tunability to filter parameters through bias currents of VDTA. SPICE simulations using TSMC 180 nm CMOS technology parameter are carried out to examine operation, total harmonic distortion and noise performance of proposal. Monte Carlo simulations are performed to study performance of the proposal under simultaneous variation in passive component values, oxide thickness and transistor threshold voltage.

Realization of Resistorless and Electronically Tunable Inverse Filters Using VDTA

This paper presents resistorless realization of inverse filters using voltage differencing transconductance amplifier (VDTA). First, four topologies are proposed which provide inverse low-pass, high-pass, band-pass, and band-reject responses. Subsequently, a unified inverse filter is also derived by incorporating two switches in the combination of proposed inverse low-pass and inverse band-pass topologies. This topology is capable of providing inverse low-pass, inverse high-pass, inverse band-pass, and inverse band-reject responses by appropriate switch settings. The proposed inverse filter structures are electronically tunable and use only grounded capacitors. The behavior of the proposed filters is also investigated for nonidealities. To verify the functionality of the proposed inverse filter circuits, SPICE simulation is carried out using 0.18-[Formula: see text]m CMOS technology parameters from TSMC. The effect of deviation in the active and passive component values on angular frequency is tested through Monte Carlo simulation.

Design of Voltage Mode Electronically Tunable First Order All Pass Filter in ±0.7 V 16 nm CNFET Technology

A novel voltage mode first order active only tuneable all pass filter (AOTAPF) circuit configuration is presented. The AOTAPF has been designed using ±0.7 V, 16 nm carbon nanotube field effect transistor (CNFET) Technology. The circuit uses CNFET based varactor and unity gain inverting amplifier (UGIA). The presented AOTAPF is realized with three N-type CNFETs and without any external passive components. It is to be noted that the realized circuit uses only two CNFETs between its supply-rails and thus, suitable for low-voltage operation. The electronic tunability is achieved by varying the voltage controlled capacitance of the employed CNFET varactor. By altering the varactor tuning voltage, a wide tunable range of pole frequency between 34.2 GHz to 56.9 GHz is achieved. The proposed circuit does not need any matching constraint and is suitable for multi-GHz frequency applications. The presented AOTAPF performance is substantiated with HSPICE simulation program for 16 nm technology-node, using the well-known Stanford CNFET model. AOTAPF simulation results verify the theory for a wide frequency-range.

Electronically controlled spoof localized surface plasmons on the corrugated ring with a shorting pin

We have demonstrated that spoof localized surface plasmons (LSPs) can be controlled by loading a shorting pin into the corrugated ring resonator in the microwave and terahertz (THz) frequencies. Electronical switchability and tunability of spoof LSPs have been achieved by mounting Schottky barrier diodes and varactor diodes across the slit around the shorting pin in the ground plane. An electronically tunable band-pass filter has been demostrated in the microwave frequencies. Such electronically controlled spoof LSPs devices can find more applications for highly integrated plasmonic circuits in microwave and THz frequencies.

Quadrature voltage control oscillator with a linear tuning law

New realisation scheme of linear voltage-controlled quadrature oscillator (QO) is proposed. The active building block is electronically tunable (ET) differential voltage current conveyor transconductance (gm) amplifier configured with current feedback amplifier and multiplication mode current conveyor devices. The designs are essentially tuned-inductor–capacitor oscillator, wherein the electronically variable lossless grounded inductor (L) had been simulated at suitable nodes of the active building block. Subsequently, with slight modification of the block, an ET floating-lossless immittance function generation is presented. Effects of device port mismatch error and parasitic capacitances are analysed. Albeit sensitivity relative to port mismatch error is negligible, the parasitic components tend to limit the higher-usable frequency range; appropriate design equations are derived for a true bilinear admittance function realisation and their applications to filter and sinusoid oscillator design are included. Experimental results on the QO with linear fo-tuning law are satisfactorily verified up to 8.7 MHz at low total harmonic distortion.

Electronically tunable MOSFET-only current-mode biquad filter

A novel current mode MOSFET-only structure with multi-input single-output (MISO) is proposed. The proposed circuit is free from passive circuit elements like resistors and capacitors and able to realize low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) filter functions with using the same circuit configuration. It is also important to note that the proposed filter has electronic tunability property. The proposed circuit is laid-out in the Cadence environment using 0.18µm TSMC CMOS technology parameters. The layout area is only 408μm2 and the power consumption is about 0.6mW. Furthermore, to investigate the performance of the BP filter output of the proposed MISO filter, Monte Carlo and corner analyses are also presented. It is shown that the mismatches and the process variations cause only small deviations for the BP filter configuration. Furthermore, the noise performance of the proposed filter is also investigated.

Electronically Tunable Fractional Order Filter

In this paper, an electronically tunable resistorless fractional order filter (FOF) based on operational transconductance amplifier (OTA) is presented. It uses two fractional capacitors (FC) of same order and provides fractional order low-pass filter and fractional order band-pass filter responses simultaneously. Mathematical formulations are outlined for various critical frequencies and transfer function sensitivities for presented FOF. The FCs of orders 0.5 and 0.9 are considered for illustrating the proposal. The FCs are realized using the fourth-order continued fraction expansion-based RC ladder and are characterized using SPICE simulations. Functional verification of presented FOF with FC of orders 0.5 and 0.9 is exhibited through SPICE simulations. The OTA is implemented using $$0.5\,\upmu \hbox {m}$$ CMOS technology model parameters. Electronic tunability of half power and right-phase frequencies of presented FOF is achieved through bias current variation of OTA. The transfer functions’ sensitivity with respect to various circuit parameters is also examined through simulations, and it is found that the values remain well within unity for most of the circuit parameters. Furthermore, the presented FOF is attractive from integration viewpoint as it achieves tunability via bias current variation in contrast to tuning through resistor variation in existing FOFs.

All-Pass Filter Based Linear Voltage Controlled Quadrature Oscillator

A linear voltage controlled quadrature oscillator implemented from a first-order electronically tunable all-pass filter (ETAF) is presented. The active element is commercially available current feedback amplifier (AD844) in conjunction with the relatively new Multiplication Mode Current Conveyor (MMCC) device. Electronic tunability is obtained by the control node voltage (V) of the MMCC. Effects of the device nonidealities, namely, the parasitic capacitors and the roll-off poles of the port-transfer ratios of the device, are shown to be negligible, even though the usable high-frequency ranges are constrained by these imperfections. Subsequently the filter is looped with an electronically tunable integrator (ETI) to implement the quadrature oscillator (QO). Experimental responses on the voltage tunable phase of the filter and the linear-tuning law of the quadrature oscillator up to 9.9 MHz at low THD are verified by simulation and hardware tests.

A new electronically tunable universal mixed-mode biquad filter

This paper introduces a new electronically tunable universal mixed-mode biquad filter topology which mainly consists of single newly introduced modified current conveyor trans-conductance amplifier (MCCTA) as active element and two capacitors, two resistors as passive elements. The filter topology can realize low pass (LP), band pass (BP), high pass (HP), band reject (BR) and all pass (AP) filtering responses in four different possible modes of operation namely, current-mode (CM), voltage-mode (VM), trans-impedance-mode (TIM), and trans-admittance-mode (TAM), through applying appropriate conditions and selection of inputs and outputs. While operating, the circuit does not need any inverted type and/or scaled type current/voltage input signal(s) for any of the filtering response realization. It is also encouraging to sustain the feature of interactive electronic tunability of quality factor as well as band-width independent of pole frequency variation, only through single biasing current of the active element. The proposed filter is simulated through PSPICE software using standard CMOS technology and offers low incremental active and passive sensitivities.