LC Resonator Research Articles

Low-Profile Omnidirectional WIFI Antennas With Pattern Reconfigurability Inspired by Meta-Resonators

A family of low-profile, omnidirectional antennas inspired by metamaterial resonators (meta-resonators) for WIFI applications is proposed. Two novel meta-resonators with an inductive feeding are presented. They can be considered as an LC resonant tank. Arbitrary size miniaturization could be obtained. Three rotated metamaterial unit cells constitute a ring-shaped structure, which generates a horizontally polarized, omnidirectional radiation. A direct microstrip power divider is used to excite them in-phase, achieving a small and low-profile magnetic dipole-like antenna. Their working principles are illustrated in detail by equivalent circuit and current distribution. Two omnidirectional antennas based on different meta-resonators and one pattern-reconfigurable antenna are fabricated and measured, respectively. Their measured −10 dB frequency bandwidth, peak gain, and radiation efficiency are greater than 2.4–2.48 GHz, 1.17 dBi, and 80%, respectively. They demonstrate superior advantages in terms of a miniaturized/low-profile size, simple structure, good bandwidth, and omnidirectional radiation performance, which are well positioned for 2.40 GHz WIFI router or indoor communications.

Passive wireless sensors fabricated by spark plasma sintering for ultra-high temperature measurements

A passive and wireless sensor based on LC resonator for ultra-high temperature measurement was designed and fabricated. The sensor consisted of a molybdenum split-ring resonator (SRR) encapsulated by an alumina ceramic matrix. The alumina ceramic matrix served as not only a dielectric material for sensing the temperature variation, but also a protective material for the SRR. The SRR was made of molybdenum by chemical etching, while the alumina ceramic shield was fabricated by spark plasma sintering (SPS). Small amount of MgO was doped into alumina powder to assist the sintering of a fully dense ceramic, preventing the molybdenum ring from high-temperature oxidation. A high temperature measurement system was built to investigate the performance of the fabricated sensor. The temperature measurement ability of the sensor was verified up to 1200 °C, with high sensitivity and good temperature resolution.

Synthesis Design on Wideband Single-Ended and Differential Dual-Band Filtering Impedance Transformer

In this brief, a novel dual-band wideband impedance transformer (IT) integrated with the function of dual-band bandpass filtering was proposed for the first time. The presented design, based on the equivalents of dual-band J-inverters and LC resonators, has a simple structure with parallel open/short-circuited stubs and cascading transmission lines. Analysis results show that the considered ITs can work at two separate uncorrelated frequency bands with arbitrary terminated real impedances. For demonstration, a wideband single-ended dual-band filtering impedance transformer (DBFIT) with the filtering order n = 4, and a differential DBFIT with n = 3, are designed. In particular, the common-mode rejection of the differential circuit is well considered. The simulated and measured results are recorded in good agreement, well verifying the design concept.

Electrical and plasma characterization of a hybrid plasma source combined with inductively coupled and capacitively coupled plasmas for O atom generation

We developed a hybrid plasma source combined with an inductively coupled plasma (ICP) antenna and a capacitively coupled plasma (CCP) electrode. The ICP antenna and the CCP electrode are connected to a single RF power generator in parallel and a variable capacitor Cv is connected to the ICP antenna in series. The currents flowing through each source and the CCP electrode voltage are measured for analysis of the electrical characteristics, and the ion densities are measured while adjusting the capacitance of the Cv. Interestingly, when a series LC resonance occurs between the inductance of the ICP antenna and the capacitance of the Cv, different trends are observed depending on the discharge mode. In capacitive mode (E-mode), the ion density is minimized and is controlled by the CCP current. On the other hand, in inductive mode (H-mode), the ion density is maximized and is affected by the ICP current. The change of the ion density can be explained by the balance between the total power absorption and power dissipation. It is also in good qualitative agreement with the calculated plasma density from the power balance equation. By adjusting the Cv, linear control of the ion density can be achieved. To evaluate the proposed source in terms of O atom generation, the number density ratio of O atom nO to Ar nAr is obtained by using the optical emission spectroscopy actinometry method. These results show that nO/nAr is controlled. Our source can be applied to plasma processing, in which ion density and O atom generation controls are important factors.

Separated Circular Capacitive Coupler for Reducing Cross-Coupling Capacitance in Drone Wireless Power Transfer System

Capacitive power transfer (CPT) system can be employed for wireless charging of drone applications. However, in the CPT system, cross-coupling capacitance caused by coupling of the two pairs of plates on different sides, which do not form the main capacitance must be considered. Designs that do not properly consider the cross-coupling capacitance can cause decrease in the efficiency of the system. In this article, we propose a separate circular capacitive coupler for the CPT system. To reduce the cross-coupling capacitance in drone applications, the plates on the same side are separated. The circuit model of the coupler is presented; it considers a total of six coupling capacitances. For maximum power transfer efficiency, impedance of the receiver is considered to determine the parameter value of the LC resonance. Through simulation and measurement, we verified that the proposed separated circular coupler can reduce the cross-coupling capacitance. The plate-to-plate power transfer efficiency is maintained at 89.4% with 100-W output power.

Recent developments of modulation and control for high-power current-source-converters fed electric machine systems

The pulse-width-modulated (PWM) current-source converters (CSCs) fed electric machine systems can be considered as a type of high reliability energy conversion systems, since they work with the long-life DC-link inductor and offer high fault-tolerant capability for short-circuit faults. Besides, they provide motor friendly waveforms and four-quadrant operation ability. Therefore, they are suitable for high-power applications of fans, pumps, compressors and wind power generation. The purpose of this paper is to comprehensively review recent developments of key technologies on modulation and control of high-power (HP) PWM-CSC fed electric machines systems, including reduction of low-order current harmonics, suppression of inductor-capacitor (LC) resonance, mitigation of common-mode voltage (CMV) and control of modular PWM-CSC fed systems. In particular, recent work on the overlapping effects during commutation, LC resonance suppression under fault-tolerant operation and collaboration of modular PMW-CSCs are described. Both theoretical analysis and some results in simulations and experiments are presented. Finally, a brief discussion regarding the future trend of the HP CSC fed electric machines systems is presented.

In brief

PAGE 1072 Chinese researchers demonstrate an eight-channel hybrid-integrated laser light source with 100 GHz channel spacing. Side mode suppression ratios of better than 40 dB were obtained via grating couplers under eight-channel simultaneous operation at a continuous wave current of 600 mA and 25°C. PAGE 1056 A robust and efficient long-term tracker based on local feature matching and density clustering is proposed by Chinese researchers for use in UAV-based tracking systems. The tracker used a novel density-based clustering method to locate an occluded target by using local collected features. Experiments show favourable performance of the algorithm compared to other related trackers. Schematic of 8-channel hybrid-integrated laser array. PAGE 1036 A collaboration of researchers from Malaysia and Bangladesh present a single switched-capacitor and series LC resonant converted based active voltage balancing circuit. The balancing circuit directly transfers energy from higher capacitive energy storage cells to lower energy storage cells. Experimental analysis demonstrates the performance of the system. The overall framework of the proposed tracker. The tracking module and re-detection module are shown in blue and red, respectively. PAGE 1091 Researchers from Mexico have developed a new subcarrier allocation scheme for NOMA systems based on the evaluation of the instantaneous behaviour of wireless channels using the condition number of the channel matrix. Simulation results reveal that the proposed scheme increases the total sum rate of the system compared to previous methods. Proposed balancing circuit schematic diagram. PAGE 1065 Researchers from the Republic of Korea present a wideband on-chip Wilkinson power divider (WPD) using lumped-element transition lines with 2-port negative capacitance circuits providing phase response with a positive slope and broadband port impedance. Experimental comparisons against other similar devices show the superior performance of this WPD. Evaluation process. Fabricated WPD chip.

SABRE and PHIP pumped RASER and the route to chaos

In a RASER (Radio-frequency Amplification by Stimulated Emission of Radiation), the fast relaxing electromagnetic modes of an LC resonator are enslaved by the slow nuclear spin motion, whose coherence decays with the transverse relaxation rate γm=1/T2∗. Such a system obeys the slaving principle, mathematically identical with the adiabatic elimination procedure, leading to multi-mode RASER equations. If the pumping rate of nuclear spin polarization Γ>>γm, a second adiabatic elimination process applies and the spectral properties of the RASER can be predicted. The resulting model is similar to the model of two non-linear coupled oscillators and predicts the observed RASER phenomena, including frequency combs and mode collapse. If the second adiabatic elimination is not applicable, mode collapse is completely absent and successive period doubling processes and chaos occur at very high population inversions. We compare these theoretical predictions with experimental results from a PHIP (Para-Hydrogen Induced Polarization) pumped 1H RASER. Moreover, in SABRE (Signal Amplification By Reversible Exchange) pumped 1H experiments, RASER revivals are observed long after the parahydrogen pumping source has been switched off. All these findings shed light onto the links between NMR spectroscopy, RASER physics, synergetics and chaos theory. Several new applications are envisioned in the fields of quantum sensor technology, structure investigation or magnetic resonance imaging (MRI).

A wireless passive extra-arterial implantable blood pressure monitoring sensing system for rats

A novel, wireless, passive, extra-arterial implantable blood pressure monitoring system was designed, fabricated, and tested. The measurement system is composed of an implantable sensor in-vivo and a readout system in-vitro. It was designed to balance the measurement accuracy and arterial invasiveness in continuous blood pressure monitoring. The passive LC resonant circuit was formed by a variable parallel-plate capacitance and a planar spiral inductor. It was fabricated and implanted in the necks of the rats to detect blood pressure changes. The variation of blood pressure was transduced into a change of the capacitance value of the variable parallel-plate capacitor, which caused a variation of the resonant frequency of the LC circuit. A readout probe with inductor coil was then used to measure the change of the resonant frequency of the LC circuit, and therefore indirectly measure the variation of blood pressure wirelessly. By measuring the resonant frequency with electromagnetic coupling of the implanted LC resonant sensor and the external inductor coil, a sensitivity of 8.53 kHz/mmHg for blood pressure measurement had been successfully achieved. The sensing distance is longer than 22 mm, which is enough for implementation of the wireless measurement. The overall size of the implantable sensor is 5 mm × 1.1 mm. The wireless implantable blood pressure sensor may be used in biomedical research for continuous, accurate and arterial trauma free blood pressure monitoring.

Probing Composite Vibrational Fingerprints in the Terahertz Range With Graphene Split Ring Resonator

Sensors with single resonant mode often produce false positive when detecting the composite vibrational fingerprints of molecules in the terahertz (THz) range. In this study, a multi-resonant plasmonic structure, consisting of periodic graphene split ring resonator (SRR) arrays, is proposed for THz sensing. The effective detection of ultrathin (0.1 μm) lactose layer is given as an example to demonstrate the detection sensitivity. The vibrational fingerprints of lactose at 0.53 THz and 1.37 THz are enhanced in transmission spectra. Besides, resonant frequencies could be actively adjusted with the gate voltage applied on the SRR array. The physical mechanism of multi-resonance can be explained by a combination of LC resonance and dipole resonance of the structure, which can be observed in the electric field distributions. Moreover, the sensing performance can be further optimized by varying geometric parameters. Furthermore, the refractive index sensing performance of the sensor is also investigated by altering the surrounding medium on the surface. The designed sensor can work under an oblique incidence, which provides potential applications in biological analysis and medical diagnostics.

LC resonant circuits based matching networks for continuous mode MMIC power amplifiers

AbstractThis article presents a practical design methodology to construct output matching networks for broadband continuous mode monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). Unlike conventional harmonic manipulation approaches, combinations of parallel and series LC resonant circuits are utilized to build the matching networks as it can generate frequency‐dependent components and locate the varying impedance of continuous mode. With a proper design, the impedance variation in frequency domain can be mapped to the frequency response of the matching network at the fundamental frequency and the second harmonic simultaneously. Matching network design procedures are demonstrated and results show that the frequency response of the network has very good approximation with the desired continuous mode conditions. A prototype PA is implemented on 0.25‐μm gallium nitride (GaN) MMIC process, and tested with both continuous‐wave and modulated signals. Measurement results show 50.82% maximum drain efficiency and 8.5 dB gain can be achieved across the operation bandwidth of 5.4 to 6.4 GHz.

Active voltage balancing circuit using single switched‐capacitor and series LC resonant energy carrier

Single switched-capacitor and series LC resonant converter-based active voltage balancing circuit are presented in this Letter. This converter is proposed to balance the cell voltage in series-connected electrochemical energy storage devices namely battery or supercapacitor. This balancing circuit directly transfers the energy from higher capacitive energy storage cells to lower energy storage cells in the string. It realises the maximum energy recovery and zero voltage gap between the cells and overcomes the drawback of switching loss, conduction loss, balancing time duration, and the voltage difference between the cells of conventional switched-capacitor as well as single LC converter. The details of the balancing circuit operation, theoretical, and mathematical analysis are presented. The experimental result demonstrated that the balancing circuit result where the voltage difference is 451–0 mV in 124 min for two 12 V, 4.5 Ah lead-acid batteries.

A 1.5-to-3.0GHz Tunable RF Sigma-Delta ADC With a Fixed Set of Coefficients and a Programmable Loop Delay

In this brief, we present a tunable bandpass RF Sigma-Delta modulator with a fixed set of feedback DAC coefficients. The sampling frequency, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , is tuned with the center frequency, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , in order to maintain a fixed normalized center frequency, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> . Any variation in the loop delay is compensated to maintain a fixed normalized loop-delay t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> /T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> . The bandpass Sigma-Delta, reported in this brief, is based on an LC resonator with tunable center frequency from 1.5 to 3.0 GHz and a corresponding sampling frequency from 6.0 to 12.0 GHz. For an oversampling ratio of 64, the ADC achieves the same SNDR of 37 dB and the same Dynamic Range of 45 dB over the complete tuning range. This performance is achieved for a bandwith of 47 MHz at 1.5GHz and a Bandwidth of 93 MHz at 3 GHz. The ADC, fabricated in a 65 nm CMOS process, consumes only 13 mW from a 1.2 V supply. In order to compare this circuit with the state of the art, we use not only the conventional ADC Figure of Merit but we also use a Figure of Merit dedicated to RF circuits. In this case, the measured chip center frequency, noise figure and non-linearity are also taken into account in the comparison.

A Wide Dynamic Range Laser Radar Receiver Based on Input Pulse-Shaping Techniques

This paper presents a Time-of-Flight laser radar receiver based on pulse-shaping at the input to the receiver channel, in which the first zero-crossing point of the converted pulse is marked as the timing moment. In this technique, an LC resonator is combined with a nonlinear feedback TIA to achieve high accuracy and high precision within a wide dynamic range. The key advantage is that the receiver does not require any post compensation or gain control techniques so that the total complexity of the TOF radar is reduced considerably. Measurements made in a $0.35~\mu m$ standard CMOS process show a bandwidth of $230MHz$ and an input-referred noise of $70nA$ RMS. The receiver chip consumes $155mW$ power from a $3.3V$ supply. The single-shot precision and accuracy of the receiver within a dynamic range of 1:50,000 are $ \sim 15mm(SNR=12)$ and $\sim \pm 15mm$ respectively. A wider dynamic range can be achieved with a larger accuracy tolerance. The functionality of the proposed receiver channel is also verified over an input pulse variation and temperature range of $0~^{\mathrm {o}}\text{C}$ to $50~^{\mathrm {o}}\text{C}$ .

A broadband asymmetric microwave metamaterial based on LC and standing-wave resonances

Three metamaterial samples were simulated, numerically analyzed, and fabricated with different resonator lengths on similar unit cells. According to the results in addition to conventional LC resonance of the resonator, standing wave resonance was also observed within the resonator-dielectric-grounded back wire waveguide. We observed that the orientation of the sides of this waveguide relative to the polarization of the incident electromagnetic wave has a direct effect on the resonant frequency. The best asymmetric shape of the resonator with the minimum reflection coefficient in a wide frequency range of about 5.5 GHz with only 3% of reflection was introduced. According to the results, metamaterial polarizers and optical filters can be produced based on the standing wave resonances.

Stretchable chipless RFID multi-strain sensors using direct printing of aerosolised nanocomposite

Wireless communicated sensors currently play a major role in due to the importance of data for internet-of-things (IoT) devices. Specifically, chipless radio frequency identification (RFID) technology is a widely used technique for communication of data due to its printability, simplicity, and low cost. Here, stretchable and chipless RFID strain sensors were fabricated by direct printing of aerosolized nanocomposites using an aerodynamically focused nanomaterial printing system, which is a direct printing process for conductive and stretchable pattern printing onto flexible substrate. In particular, microscale porous conductive patterns composed of silver nanoparticle and multi-walled carbon nanotube composites were printed onto polydimethylsiloxane. The fabricated sensor exhibited motion with a high degree of freedom, including the ability to be stretched, twisted, or folded. Moreover, it demonstrate a gauge factor >0.5 and maximum strain limit >20 %, with resonance frequency controllability due to regulation of the geometrical properties of LC resonance circuits. Because the original sensor characteristics allowed independent sensing in a single direction, we fabricated an RFID strain sensor that could measure normal strain, as well as shear strain in all directions. Finally, we directly printed the sensor onto air tubes and verified its performance.

Single event transient study on PMOS-NMOS cross-coupled LC-VCO using PLL

ABSTRACT A theoretical analysis for single event transient phenomena in a cross-pair LC-VCO (Inductor Capacitor-VCO) is presented. The analytical model developed using unit step approximation for the dual double exponential SET current pulse closely captures the SET phenomenon in the LC resonant tank. Also, a model developed to capture the increase or decrease in the transconductance of the cross pair VCO in response to SET hit in the tail transistor and the transistor connected to the output of the VCO is presented. The developed model helps to capture the voltage and phase variation caused by the SET pulse more accurately in the oscillator. Further, the performance of LC-VCO under SET hit has been observed within PLL for different swing values. The simulation result shows that the recovery time and phase displacement produced by SET can be reduced by biasing the LC-VCO in the current limited regime and by having a large swing. The simulation results for cross-coupled LC-VCO are validated with 90 nm CMOS process technology.

Double Fano Resonances in S-Shaped Plasmonic Metasurfaces in Terahertz Region

We numerically and experimentally demonstrated double Fano resonances in a simple S-shaped plasmonic metasurface in the terahertz frequency range. Apart from the LC resonance and electric dipole (ED) resonance, two trapped modes are excited in two different types of asymmetric S-shaped structures in the frequency range 0.2–1.4 THz, which are mainly attributed to a magnetic dipole (MD) and an electric quadrupole (EQ). Thereafter, double Fano resonances (one Fano and one electromagnetically induced transparency (EIT) resonance) are achieved via the coupling of the two dark trapped modes and a broad bright ED at normal incidence of the metasurfaces. Furthermore, under oblique incidence, strong Fano responses can be observed; they are considerably enhanced in asymmetric structures, and even in a symmetric structure. The proposed S-shaped plasmonic metasurfaces are easy to fabricate and have potential applications in multi-wavelength optical switches, filters‚ and sensors.

Monolithic CMOS Microwave Heater With Programmable Thermostat Function for Thermotherapy

A monolithic microwave heater with programmable thermostat function is implemented for thermotherapy. To achieve microwave heating, the heater adopts a 2.4-GHz oscillator to generate the microwave and uses an amplifier with LC resonance load to enhance the signal strength. Consuming the power of 113.0 mW, the amplifier delivers the power of 13.2 dBm. The microwave heater is integrated with temperature sensors, an 11-bit SAR-ADC and a comparator to achieve the programmable thermostat function. For 3-mm thick agar phantoms, the heating rate is around 0.16°C/min. The heater successively achieves the programmed temperature increases of 1.5, 3.0 and 4.5°C, with the standard deviation <; 0.19°C under the thermostat condition.

Analysis and Design of Series LC Resonance-Pulse Based Zero-Current-Switching Current-Fed Half-Bridge DC–DC Converter

This article investigates upon partial resonance in current-fed converter using series LC resonant circuit to attain zero-current-switching (ZCS) of the semiconductor devices. A resonance pulse appears during overlap conduction time of the semiconductor devices causing natural current reduction in an outgoing device to zero before the gating signal is forced-off achieving ZCS commutation of the devices. Soft device turn-off eliminates the turn-off switching losses and more importantly, avoids the traditional requirement of additional snubber to clamp the voltage across the semiconductor devices in current-fed converters. Partial resonance reduces the circulating current and so rms current through the devices limiting the conduction losses. The proposed idea is analyzed and implemented on current-fed half-bridge isolated voltage doubler topology. It has been experimentally demonstrated to achieve wide range ZCS operation along with high efficiency.