Impedance Conversion Research Articles

A compact broadband RF rectifier using two‐stage microstrip lines

AbstractThis paper simulates and measures a compact broadband rectifier for voltage doubler Schottky diode. Among them, a two‐stage microstrip line impedance matching network for voltage doubling circuits is used. The imaginary part of the diode impedance is limited by the short‐circuit branch. The impedance conversion transmission line matches the impedance to 50 Ω. The impedance matching in the circuit is only realized by two‐stage microstrip lines, which reduces the physical size of the rectifier and makes the rectifier more compact. Judging the measurement results from 0.8 to 2.5 GHz, the conversion efficiency is greater than 30% at 0 dBm, the bandwidth is 103%, and the maximum conversion efficiency reaches 66.3% at 8 dBm. In addition, the compact size of the rectifier is 23 × 20 mm2.

An ultra-wideband power amplifier designed through a bandwidth expansion strategy

Abstract A bandwidth expansion strategy for ultra-wideband power amplifiers (PAs) is presented in this letter by adopting a parallel impedance matching architecture. This design strategy can effectively reduce the impedance conversion ratio between the load and the target impedance of the PA, thereby providing a feasible solution for broadband impedance matching. Subsequently, a commercially available 10 W gallium nitride device and a two-stage Wilkinson power divider network are combined to achieve the verification of the proposed theory. The results of the measurement show that within the target frequency band of 0.9–3.9 GHz, 58.5–71.2% of the drain efficiency and 9.1–12 dB of gain can be achieved with a saturated output power of 39.1–42 dBm.

A Novel Cascaded Buck Active Rectifier With Arbitrary Impedance Conversion Ratio for Inductive Power Transfer System

A Novel Cascaded Buck Active Rectifier With Arbitrary Impedance Conversion Ratio for Inductive Power Transfer System

A 8–12 GHz power amplifier with high out-of-band rejection

This paper proposes an 8–12 GHz monolithic power amplifier (PA) with high out-of-band rejection. This PA adopts an impedance conversion technique to reduce the Q of the output impedance of the amplifiers for all stages, which is used to achieve broadband matching performance. In addition, the bandpass matching structures and a trap circuit are adopted to effectively suppress out-of-band signals. The proposed PA is fabricated by using a 0.5 μm GaAs pHEMT process. The measurement results show that the PA has an in-band small signal gain of 23 dB ± 0.7 dB, input and output return loss are both better than −14dB, the saturation output power is about 23dBm, the power-added efficiency (PAE) is better than 20 %, and rejection ratios are 65dBc and 51dBc at 3 GHz and 17 GHz respectively. The area is of 2.3mm × 1.1 mm.

Characterization of Mechanical Oscillations in Bismuth Selenide Nanowires at Low Temperatures.

A single transistor preamplifier circuit was designed to facilitate electrical detection of mechanical oscillations in nanoelectromechanical systems (NEMSs) at low temperatures. The amplifier was integrated in the close vicinity of the nanowire inside the cryostat to minimize cabling load and interference. The function of the circuit was impedance conversion for current flow measurements in NEMSs with a high internal resistance. The circuit was tested to operate at temperatures as low as 5 K and demonstrated the ability to detect oscillations in double-clamped bismuth selenide nanowires upon excitation by a 0.1 MHz-10 MHz AC signal applied to a mechanically separated gate electrode. A strong resonance frequency dependency on temperature was observed. A relatively weak shift in the oscillation amplitude and resonance frequency was measured when a DC bias voltage was applied to the gate electrode at a constant temperature.

Design of the Wilkinson power divider with multi harmonic suppression

Abstract A Wilkinson power divider (PD), which can suppress the second, third, and fourth harmonics is proposed. The PD is implemented based on an asymmetric meta-structure. The meta-structure is constructed be combing defect ground structure (DGS) and spoof surface plasmon polariton (SSPP). It can not only realize the impedance conversion function in the operating frequency band, but also realize the suppression of the second, third, and fourth harmonics. The simulation and measurement results show that this structure can achieve −32 dB suppression for the second harmonic, −31 dB suppression for the third harmonic, and −28 dB suppression for the fourth harmonic respectively.

Single-Stage Active Rectifier With Wide Impedance Conversion Ratio Range for Inductive Power Transfer System Delivering Constant Power

Compared with the constant current (CC) charging mode, the constant power (CP) charging mode can speed up the battery charging rate and free the charger from excessive thermal design problems. However, the range of the battery's equivalent resistance in CP mode is wider than that in CC mode, which makes it difficult to track the optimal resistance of the inductive power transfer (IPT) system for efficiency enhancement. To solve this problem, this paper proposes a single-stage active rectifier (SSAR) integrating an interleaved buck converter with a full-bridge active rectifier (FBAR). Compared with the traditional FBAR, the resistance conversion ratio range of the SSAR is extended from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8/\pi ^{2}]$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8]$</tex-math></inline-formula> , and the output current ripple is reduced due to the interleaved operation. A novel optimal phase angle control strategy is correspondingly proposed for the IPT system with the SSAR, which features advantages of wide impedance conversion ratio range, zero voltage switching (ZVS) turn-on of all MOSFETs, and no communication between the primary and the secondary sides. A 150 W experimental prototype is provided to verify the effectiveness of the proposed rectifier.

Experimental Study on Response of Non- and Externally-Gapped Metal-Oxide Arresters Excited by Nanosecond-Level Transient Electromagnetic Disturbances

Metal-oxide arresters (MOA), including the non-gapped MOAs (NG-MOA) and externally-gapped MOAs (EG-MOA), are the main equipment applied to protect the power system against conducted transient electromagnetic disturbances (TED). However, MOAs exhibit quite different electrical characteristics under microsecond-level and nanosecond-level transients. In order to figure out the response of MOAs under nanosecond-level TED, experimental platforms are built which contain a pulse generator with the amplitude of pulse current adjustable from 0 kA to 5 kA and the rise time of 20 ns. Then the dynamic hysteresis loops, the static V-I characteristics, the response time delay and the full response process of five types of 10-kV MOAs are investigated. From the dynamic hysteresis loops of NG-MOAs, the impedance conversion process can be seen clearly and can be explained by the grain-boundary theory. But EG-MOAs has not this conversion process due to the air-gap. And the experimental results demonstrate that there is no noticeable nanosecond-level conduction delay on NG-MOAs whereas the electric field non-uniformity of the air-gap has a significant influence on the time delay of the EG-MOAs. The response time delay of EG-MOAs changes ranging from tens of nanoseconds to hundreds of nanoseconds. This feature makes EG-MOAs more likely to raise insulation risks under nanosecond-level TED compared with NG-MOAs.

24–35 GHz Filtering LNA and Filtering Switch Using Compact Mixed Magnetic-Electric Coupling Circuit in 28-nm Bulk CMOS

This paper presents compact 24–35 GHz filtering low noise amplifier (LNA) and filtering switch in 28-nm CMOS technology. A compact mixed magnetic-electric coupling circuit is designed, where a transmission zero is introduced out of the passband due to the cancellation of the magnetic and electric couplings. By analyzing the impedance characteristics, this structure can be designed with the impedance conversion function to replace the widely used transformers in integrated circuit designs. It shows the advantages of easy control of coupling coefficient and out-of-band rejection. Then, an LNA employing the magnetic-electric coupling circuits as impedance matching networks is designed. Image rejection can be achieved without increasing the circuit area. Moreover, by loading transistors to this mixed magnetic-electric coupling circuit, the input impedance can be controlled by the parasitic components of the transistor. Subsequently, a filter passband can be switched on and off, realizing a very compact filtering single-pole single-throw (SPST) switch. The fabricated filtering LNA is measured with a 3-dB bandwidth of 24–35 GHz, a noise figure (NF) of 2.4-3.6 dB, a maximum gain of 22 dB, and suppression of better than 25 dBc below 18 GHz. The filtering switch shows a minimum on-state loss of 2.1 dB at 28.6 GHz with better than 12.9 dB rejection below 16 GHz and off-state isolation of higher than 19 dB.

Enhancing the Measurement Sensitivity and Repeatability of Electrolyte-Insulator-Semiconductor Capacitor Sensor With Impedance Conversion

The measured performance of the electrolyte-insulator-semiconductor capacitor (EISCAP) is related not only to the device structure and technology, but also to the measurement methods. For the conventional amplitude measurement method, since the capacitance of EISCAP is very small, the measurement procedure is easily affected by the fluctuation of reference electrode and solution impedance, which leads to low sensitivity and poor repeatability. In this study, a measurement method with impedance conversion is proposed for enhancing the measured sensitivity and repeatability of the EISCAP. Different from the conventional measurement method, an impedance conversion stage is inserted in front of the transimpedance amplifier in this approach; thus, the fluctuation of impedance of solution and reference electrode is suppressed, and the measurement repeatability is improved. At the same time, the capacitance of the sensor has been significantly amplified, so that the sensitivity can be improved. Under the condition of 2 kHz, compared with the traditional measurement method, the measurement sensitivity and repeatability with the proposed approach were improved by 13.81% and 63.64%, respectively.

A novel L-band metamaterial slow wave structure with low space charge effect and high field uniformity

A novel L-band metamaterial slow wave structure with a weak space charge effect and high field uniformity is proposed. The slow wave structure is composed of two identical all-metal resonant elements. In order to weaken the space charge effect, a long drift tube is adopted as a metal joint, connecting the front periodic unit with the rear one. Moreover, the novel metamaterial structure exhibits higher field uniformity by rotating one of the resonant elements 45° relative to the other. Electromagnetic calculation indicates that the average fluctuation in the electric field dropped from 3% to 0.5%. Based on the novel metamaterial slow wave structure, an L-band Cerenkov oscillator model is built, and a preliminary particle-in-cell simulation is carried out. Under the condition of an acceleration voltage of 500 kV, beam current of 8 kA, and magnetic field of 1 T, a 1.64 GW average output microwave power at 1.30 GHz is obtained. The corresponding conversion efficiency is 41%. The simulation results prove the advantages of the metamaterial Cerenkov oscillator, such as low magnetic field, low impedance, miniaturization, and high conversion efficiency.

Compact Wideband and Variable Impedance Transformation Ratio Balun for Folded Dipole

Aiming at dipoles with different impedances, a wideband balun with adjustable impedance for the balanced port is proposed in this communication. The balun is directly connected to the dipole to form an antenna element, so it also needs to meet: no connection line is required; the overall size is less than a quarter of the wavelength. The proposed balun realizes balanced–unbalanced conversion through aperture coupling, and dual slot ensures its wide-band characteristics. Due to the high-impedance characteristics of the folded dipole (FD), the balun has achieved impedance conversion ratios of 6:1, 8:1, 10:1, and 12:1, and the corresponding bandwidths are 82.1%, 67.1%, 53.7%, and 44.4%, respectively. Finally, three types of wideband dipoles with different characteristic impedances are fabricated to verify the versatility of the balun.

Influence of dimensions of wooden samples for determination of acoustic parameters and sound timbre

Wood is a popular material used in almost all areas of acoustics. The main reason for its vibro-acoustic properties is associated with orthotropic visco-elasticity, describing the ability to conduct, amplify or damp the sound vibrations in different applications. With modern technologies, it is possible to upgrade non-destructive material analysis to more detailed level. This study is dedicated to assess the vibro-acoustic properties of wood using frequency response to an impact excitation. Using one-axis sensors, the parameters such as dynamic modulus of elasticity, radiation coefficient, acoustic impedance, damping coefficient, and acoustic conversion efficiency were determined depending on the anatomical direction of wood. The dependence of sample dimensions and scale of measured parameters was evaluated. Broader description of the damping includes mode shape, its rank, direction and frequency. Comparison of vibro-acoustic behavior across important European species was performed. Results show samples with higher slenderness have smaller differences between MOED calculated from the first bending or first longitudinal mode shape. Analysis of the damping coefficient shows, mode shape, its rank and sample size have greater effect on material damping than frequency of vibrations.

Photonic spiking neural networks with event-driven femtojoule optoelectronic neurons based on Izhikevich-inspired model.

Photonic spiking neural networks (PSNNs) potentially offer exceptionally high throughput and energy efficiency compared to their electronic neuromorphic counterparts while maintaining their benefits in terms of event-driven computing capability. While state-of-the-art PSNN designs require a continuous laser pump, this paper presents a monolithic optoelectronic PSNN hardware design consisting of an MZI mesh incoherent network and event-driven laser spiking neurons. We designed, prototyped, and experimentally demonstrated this event-driven neuron inspired by the Izhikevich model incorporating both excitatory and inhibitory optical spiking inputs and producing optical spiking outputs accordingly. The optoelectronic neurons consist of two photodetectors for excitatory and inhibitory optical spiking inputs, electrical transistors' circuits providing spiking nonlinearity, and a laser for optical spiking outputs. Additional inclusion of capacitors and resistors complete the Izhikevich-inspired optoelectronic neurons, which receive excitatory and inhibitory optical spikes as inputs from other optoelectronic neurons. We developed a detailed optoelectronic neuron model in Verilog-A and simulated the circuit-level operation of various cases with excitatory input and inhibitory input signals. The experimental results closely resemble the simulated results and demonstrate how the excitatory inputs trigger the optical spiking outputs while the inhibitory inputs suppress the outputs. The nanoscale neuron designed in our monolithic PSNN utilizes quantum impedance conversion. It shows that estimated 21.09 fJ/spike input can trigger the output from on-chip nanolasers running at a maximum of 10 Gspike/second in the neural network. Utilizing the simulated neuron model, we conducted simulations on MNIST handwritten digits recognition using fully connected (FC) and convolutional neural networks (CNN). The simulation results show 90% accuracy on unsupervised learning and 97% accuracy on a supervised modified FC neural network. The benchmark shows our PSNN can achieve 50 TOP/J energy efficiency, which corresponds to 100 × throughputs and 1000 × energy-efficiency improvements compared to state-of-art electrical neuromorphic hardware such as Loihi and NeuroGrid.

Recent Progress of Switching Power Management for Triboelectric Nanogenerators.

Based on the coupling effect of contact electrification and electrostatic induction, the triboelectric nanogenerator (TENG) as an emerging energy technology can effectively harvest mechanical energy from the ambient environment. However, due to its inherent property of large impedance, the TENG shows high voltage, low current and limited output power, which cannot satisfy the stable power supply requirements of conventional electronics. As the interface unit between the TENG and load devices, the power management circuit can perform significant functions of voltage and impedance conversion for efficient energy supply and storage. Here, a review of the recent progress of switching power management for TENGs is introduced. Firstly, the fundamentals of the TENG are briefly introduced. Secondly, according to the switch types, the existing power management methods are summarized and divided into four categories: travel switch, voltage trigger switch, transistor switch of discrete components and integrated circuit switch. The switch structure and power management principle of each type are reviewed in detail. Finally, the advantages and drawbacks of various switching power management circuits for TENGs are systematically summarized, and the challenges and development of further research are prospected.

Harmonic Balance/Full-Wave Analysis of Wearable Harmonic Transponder for IoT Applications

The article presents a novel design of a compact wearable harmonic transponder with double-plane symmetry, composed of a dual-band patch-type antenna loaded by an HSMS-2820 Schottky diode, operated as a proof of concept at ISM UHF 869 and 1734 MHz frequencies. The antenna is analyzed and optimized for a minimum ground plate size by means of the CST Microwave Studio electromagnetic simulator, and its reflection coefficient is incorporated into the equivalent circuit model for a combined harmonic balance (HB) and full-wave analysis using the AWR Microwave Office commercial simulator. The transponder performance, including the complex input impedance matching and conversion loss (CL) between the fundamental and second harmonic frequencies on the diode, was evaluated both in free space and when attached to a human muscle phantom. The total harmonic transponder CL, including diode CL, antenna transponder gains, and impedance mismatching, is 6.2 dB for an excitation power of −25 dBm at the antenna–diode interface. The measured reading distances are 9.0 and 8.8 m for equivalent isotropically radiated power (EIRP) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=20$ </tex-math></inline-formula> dBm when the transponder is placed in free space and on the human body, respectively. As a means of machine-to-person communication, the transponder is suitable for the Internet of Things (IoT) concept, e.g., for the identification of pedestrians in traffic, i.e., in a complex environment with unwanted radiation clutter and multipath fading.

Uncovering low frequency band gaps in electrically resonant metamaterials through tuned dissipation and negative impedance conversion

A new class of electromechanically coupled metamaterial is presented which relies on magnetic field interactions between the host structure and a local resonator circuit to realize novel vibration control capabilities. The metamaterial chain exhibits a highly tunable vibration band gap which can be easily placed at a desired frequency using the resonant circuit parameters, providing a robust mechanism to independently alter the band gap width, depth, and frequency of maximum attenuation. In its dissipative form, the electromechanical metamaterial is shown to exhibit electrical metadamping as a function of the local resonance circuit resistance. The impact of the damping ratio as a function of the electrical resistance is characterized in frequency and time domains, and related to the infinite system dynamics. A robust experimental realization of the system is constructed which achieves electromechanical coupling through a moving coil and magnet system. The apparatus is used to show that the band gap location and depth can be readily tuned with the circuit elements. The presented metamaterial has potential for meaningful vibroacoustic practical applications in addition to revealing fundamentally new properties of damped electrically-resonant structures.

Analysis and design of diode physical limit bandwidth efficient rectification circuit for maximum flat efficiency, wide impedance, and efficiency bandwidths

Generally, a conventional voltage doubler circuit possesses a large variation of its input impedance over the bandwidth, which results in limited bandwidth and low RF-dc conversion efficiency. A basic aspect for designing wideband voltage doubler rectifiers is the use of complex matching circuits to achieve decade and octave impedance and RF-dc conversion efficiency bandwidths. Still, the reported techniques till now have been accompanied by a large fluctuation of the RF-dc conversion efficiency over the operating bandwidth. In this paper, we propose a novel rectification circuit with minimal inter-stage matching that consists of a single short-circuit stub and a virtual battery, which contributes negligible losses and overcomes these existing problems. Consequently, the proposed rectifier circuit achieves a diode physical-limit-bandwidth efficient rectification. In other words, the rectification bandwidth, as well as the peak efficiency, are controlled by the length of the stub and the physical limitation of the diodes.

Comprehensive modelling framework for a low temperature gradient thermoelectric generator

Thermoelectric energy harvesting (TEH) is a promising technology enabling the self-sustainable operation of ultra low-power sensing devices performing monitoring tasks. Conventional TEH research mainly focuses on the improvements of the material properties (i.e thermoelectric figure of merit ZT) and thermoelectric module (TEM) geometry. However, enhanced performance of the thermoelectric generator (TEG) can not be practically achieved without optimal integration of the novel TEM with the DC-DC converter. The power converter, having its own input impedance requirements and conversion efficiency curve, may keep the operation point of TEG far from the maximum power point of TEM, leading to power loss. Furthermore, since the physical processes in the thermoelectric transducer are coupled with the electrical processes in the DCDC converter, both components should be analyzed together to achieve the best harvesting performance. Given the system complexity, an accurate simulation model is required to estimate the output power and make an optimal system design. We report on a simulation approach for low temperature gradient TEG that accounts for both the thermoelectric and the power conversion processes. The proposed approach was validated on the TEG testbed by imitating the realistic ambient conditions for thermoelectric transducer connected to a commercial off-the-shelf DC-DC converter. Experimental results are characterized by 9% mean percentage error of power estimation which outperforms the methods based on conventional TEG representations.

A Broadband Asymmetrical GaN MMIC Doherty Power Amplifier with Compact Size for 5G Communications

This paper proposes a broadband asymmetrical monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) using 0.25-μm gallium-nitride process with a compact chip size of 2.37 × 1.86 mm2 for 5G communication. It adopts an unequal Wilkinson’s power divider with a ratio of 2.5:1, where 71.5% of the total power is transferred to the main amplifier for higher gain. Different input matching networks are used to offset phase difference while completing impedance conversion. This design also applies a novel topology to solve the problem of large impedance transformer ratio (ITR) in conventional DPA, and it optimizes the ITR from 4:1 to 2:1 for wider band. Moreover, most of the components of the DPA including power divider and matching networks use lumped inductors and capacitors instead of long transmission line (TL) for a smaller space area. The whole circuit is designed and simulated using Agilent’s advanced design system (ADS). The simulated small-signal gain of DPA is 8–11 dB and the saturation output power is more than 39.5 dBm with 800 MHz band from 4.5 GHz to 5.3 GHz. At 6-dB output power back-off, the DPA demonstrates 38–41.3% power added efficiency (PAE), whereas 44–54% PAE is achieved at saturation power.