Optimum Impedance Research Articles

A multi‐variable double impedance matching network design algorithm with design example of a low noise amplifier

In this article, we propose a matching network design algorithm based on the segmentation of the real and imaginary part of optimum source impedance curve with respect to space variable x $$ x $$ and frequency ω $$ \omega $$ , respectively. The impedance curve (comprising of real and imaginary parts) is approximated as a collection of n $$ n $$ linear segments, represented by the weighted sum of n $$ n $$ semi-infinite linear functions. Using the numerical method, optimum weight vectors that maximize transducer power gain are obtained to model the real and imaginary parts of the source impedance curve. We get the values of optimum weight vectors and the rational input impedance function for the matching network, which are then synthesized in the desired topology by a continued partial fraction. Experimentally, we validate the novelty of the proposed method by designing matching networks of a wideband custom monolithic microwave integrated circuit (MMIC) low noise amplifier (LNA) in 1.3–2.3 GHz frequency band. The measured results of the designed LNA are significantly close to the simulated results. We bias our LNA at (5 V, 150 mA) and achieve a maximum noise figure of 1.25 dB, OP1dB of 26 dBm, and an average TOI of 38 dBm. Moreover, our design of custom LNA MMIC has an integrated ESD structure while occupying only 0.32 mm2 of chip area.

Optimizing the microwave absorption feature of LaCoO3/Bi2S3 nanocomposite by regulating the filler loading content tested via waveguide and free-space methods

Electromagnetic absorbent materials have received significant attention, recently, due to the growing concern about microwave contamination caused by widespread electronic devices. So, a lot of work has been done to develop advanced absorbing materials with excellent performance. Here, Bi2S3 decorated LaCoO3 nanocomposite has been fabricated via a solvothermal method. To study the microwave absorption properties, LaCoO3@ Bi2S3 nanocomposites with 5, 15, 25, 35 and 40 wt% loadings were prepared. With optimal microwave absorption performance, a 35 wt% sample has decent minimum reflection loss (RLmini) with qualified frequency bandwidth (RL > 10 dB) covering nearly the whole X-band. Enhancements in microwave absorption efficiency of 35 wt% sample are ascribed to the highest dielectric loss, highest magnetic loss, maximum attenuation constant, as well as optimal impedance matching value. Furthermore, the optimal sample is tested via two measurement techniques; waveguide and free-space methods. A Comparison has been drawn between the variation of reflection loss measured by both methods. The free-space approach proves a good alternative measurement technique with contact-free and non-destructive benefits. Our findings may be useful in the design and fabrication of LaCoO3@ Bi2S3 nanocomposites for efficient microwave absorbers.

Multifunctional elastic rGO hybrid aerogels for microwave absorption, infrared stealth and heat insulation

The application of advanced radar and infrared detection technology promotes the development of microwave-infrared compatible stealth technology, but also poses great challenges. Especially for the new generation of stealth fighters, how to facilely prepare a lightweight stealth material in both microwave and infrared is urgent. Herein, hierarchically porous reduced graphene oxide (rGO)/graphene oxide nanoribbon (GONR) aerogels (GG) with excellent stealth properties were prepared through green reduction and pyrolysis of the gel formed by GO and GONR. Remarkably, the aerogel (0.008 g/cm3) shows strongest yet broadest electromagnetic absorption when the percentage of GO and GONR is equal (GG33). Its effective absorption bandwidth (EAB) achieves 8.45 GHz and RL is up to −63.52 dB measured by coaxial method. In addition, the plane of GG33 exhibits a broad EAB of 8.52 GHz verified by the arch method. These are mainly attributed to the optimal impedance matching characteristics and increased polarization centers. Moreover, the porous structure formed by the rGO adsorbed with GONR ensures its eminent thermal insulation (less than 0.06 Wm/K), which is the key to infrared stealth. Interestingly, GG aerogels display great elasticity with reversible compressibility, fatigue resistance (100 % recovery after 1000th cycles under 30 % strain), and compression resistance sensitivity. In short, these excellent properties make ultra-lightweight multifunctional aerogels promising for various applications such as microwave-infrared compatible stealth aircrafts and portable electronic devices.

Directly Matching an MMIC Amplifier Integrated with MIMO Antenna through DNNs for Future Networks.

Due to the exponential growth of data communications, linearity specification is deteriorating and, in high frequency systems, impedance transformation leading to power delivering from power amplifiers (PAs) to antennas is becoming an increasingly important concept. Intelligent-based optimization methods can be a suitable solution for enhancing this characteristic in the transceiver systems. Herein, to tackle the problems of linearity and impedance transformations, deep neural network (DNN)-based optimizations are employed. In the first phase, the antenna is modeled through the DNN with using the long short-term memory (LSTM) leading to forecast the load impedances in the a wide frequency band. Afterwards, the PA is modeled and optimized through another LSTM-based DNN using Multivariate Newton’s Method where the optimal drain impedances are predicted from the first DNN (i.e., modeled antenna). The whole optimization methodology is executed automatically leading to enhance linearity specification of the whole system. For proving the novelty of the proposed method, monolithic microwave integrated circuit (MMIC) along with the multiple-input multiple-output (MIMO) antenna is designed, modeled, and optimized concurrently in the frequency band from 7.49 GHz to 12.44 GHz. The proposed method leads to enhancing the linearity of the transceiver in an effective way where DNN-based PA model gives rise to a solution for achieving the most optimal drain impedance through the modeled DNN-based antenna.

Theoretical study of S wave passing through a double-layer wave impeding block in the unsaturated soil

In foundation vibration control, the multi-layer isolation barrier has a good vibration isolation effect due to its ability to block the propagation of elastic waves multiple times. In this paper, using the double-layer wave impeding block(WIB) as an example, the calculation model of a double-layer WIB as a vibration isolation barrier in the unsaturated soil foundation is established. The analytical solution of the transmission/reflection amplitude ratio when the S wave passes through the double-layer WIB in the unsaturated soil foundation is calculated by using the Helmholtz vector decomposition theorem. In addition, the influence of parameters such as the wave impedance ratio, saturation, shear modulus and density on the vibration isolation performance of the WIB are analyzed by numerical examples. The results show that the wave impedance ratio, shear modulus and density of the WIB material have a significant influence on the transmission/reflection amplitude ratio. Saturation has little effect on the transmission/reflection amplitude ratio of P1 and S waves but has a great effect on the amplitude ratio of P2 and P3 waves. The best vibration isolation effect can be obtained by selecting the optimal wave impedance ratio and shear modulus of the double-layer WIB material.

Tunable and ultraefficient microwave absorptivity in SnO2/Sn/rGO composites via enhanced polarization effect

Absorbing materials featuring effective frequency modulation are expected to meet the requirements for practical application, but remain a significant challenge. To this end, a high efficiency and absorption-range electromagnetic wave absorber was hereby proposed, and a series of rGO-based composites and the realization of effective frequency modulation in 8–14 GHz (<−10 dB) were successfully obtained by controlling the interface components (SnO2/Sn). This ascribes to the adjustable relaxation polarization, which plays a decisive role in microwave loss and the frequency modulation mechanisms. Besides the ideal regulation range of relaxation polarization for dielectric loss materials was confirmed (0.09–3.1) by conforming to the optimal impedance matching principle. In addition, the Sn/rGO and paraffin composite absorbers with reflection loss values of − 39.5 dB at 3 mm were obtained in X-band (5 wt%). The enhanced polarization loss and microwave absorptivity can be explained in terms of the intrinsic carrier concentration and the carrier migration. Overall, the hereby proposed strategy and theoretical analysis do provide a new perspective for designing absorbing devices in practical application.

Research on dual‐frequency modulation strategy of wireless power transfer system

AbstractCompared with traditional wired power transmission, wireless power transfer(WPT) has fully exhibited its key advantages of better safety and convenience, stronger reliability and electrical isolation, and less maintenance. Although the phase‐shift modulation strategy has been widely used in various WPT applications, it has certain limitations in terms of high‐frequency hard‐switching, which increases the power loss of the WPT system during voltage regulation. To achieve efficient operation over a wide range of load power, this paper proposes a dual‐frequency modulation strategy for the WPT system. The advantages of the dual‐frequency modulation strategy are the simple modulation logic and the lower switching loss. It maintains the optimal load impedance during constant voltage output and improves the overall efficiency of the system. For validation, we designed the control circuit and wrote the control program and built the experimental prototype of the WPT system to carry out the phase‐shift modulation experiment and the dual‐frequency modulation experiment, respectively. The experimental results show that the soft switching range and efficiency of the WPT system under the dual‐frequency modulation strategy are better. At the rated output power, the efficiency of the WPT system under dual‐frequency modulation strategy is 89.75%. The feasibility of the dual‐frequency modulation strategy has been confirmed.

Learning-based Adaptive Optimal Impedance Control to Enhance Physical Human-robot Interaction Performance

Learning-based Adaptive Optimal Impedance Control to Enhance Physical Human-robot Interaction Performance

Constructing reduced graphene oxide and polypyrrole coatings on glass fiber to enhance its absorbing performance

AbstractIn this work, a new route for improving the absorbing performance of glass fibers (GFs) composites by introducing the reduced graphene oxide (RGO)/polypyrrole (PPy)/RGO coatings through the self‐assembly method and then the in‐situ polymerization method was proposed. The corresponding microstructure and electromagnetic parameters were measured by scanning electron microscopy, X‐ray photoelectron spectroscopy, and vector network analyzer. The result indicated that the RGO/PPy/RGO coatings can adjust the absorbing performance of GFs composites by its synergistic effect, thus exhibiting optimum impedance matching degree and high conduction loss ability. The minimum reflection loss value of the synthesized RGO/PPy/RGO/GFs composite can reach −55.8 dB with the thickness of 4.3 mm, and the effective absorption bandwidths (≤−10 dB) covered the entire X‐band. This work proved that the RGO/PPy/RGO coatings can be used to adjust the radar absorbing performance of GFs composites.

Theoretical study of P1 wave passing through a double-layer wave impeding block in the unsaturated soil

Based on the propagation theory of elastic waves in unsaturated porous medium and single-phase elastic medium, the calculation model of a double-layer wave impeding block (WIB) as vibration isolation barrier in unsaturated soil foundation is established. The analytical solution of the transmission/reflection amplitude ratio of P1 wave passing through a double-layer WIB in unsaturated soil foundation are derived by Helmholtz vector decomposition theorem. The influences of physical and mechanical parameters such as saturation, wave impedance ratio, density, and shear modulus on the vibration isolation effect of the double-layer WIB when P1 wave passing through the double-layer WIB in the unsaturated soil foundation are analyzed by parametric studies. The results show that the saturation has a small effect on the transmission/reflection coefficients of P1 and S waves and a significant effect on the transmission/reflection coefficients of P2 and P3 waves. The wave impedance ratio and the shear modulus and density of the double-layer WIB have a significant effect on the transmission/reflection coefficients. The optimal shear modulus and wave impedance ratio of the double-layer WIB can be selected to obtain the best vibration isolation effect, which provides theoretical guidance for the application of the double-layer WIB in the field of unsaturated ground vibration control.

A 44–64-GHz mmWave Broadband Linear Doherty PA in Silicon With Quadrature Hybrid Combiner and Non-Foster Impedance Tuner

The proliferation of millimeter-wave (mmWave) bands across 24–90 GHz and the strict spectral efficiency requirements demand future transmitter front ends to operate across multiple bands with simultaneously back-off efficiency and high linearity—characteristics that typically trade off strongly with each other. In this article, we propose a simultaneously broadband, back-off efficient and linear mmWave Doherty power amplifier (PA) architecture with a quadrature hybrid, and a non-Foster inspired impedance tuner on-chip. The combination of transformer-based hybrid and the quasi-non-Foster tuner allows the architecture to synthesize optimal impedances to the PA across the 2-D variations of power back-off and frequency, enabling high back-off efficiency across a broad frequency range. In addition, the unique location of the tuner at the isolation port of the hybrid allows us to exploit its benefits while shielding the architecture from effects of tuner non-linearity, power losses, and typical stability concerns of traditional non-Foster circuits. For high linearity, we implement an emitter follower-based class-C bias network with boosting effect. The PA is implemented in a 130-nm SiGe BiCMOS process. Across 44–64 GHz, the PA achieves 18.5–21.5-dBm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {sat}}$ </tex-math></inline-formula> , the peak collector efficiency of 26%–34.7% and 14%–23.2% at 6-dB back-off, maintaining back-off enhancement ratio of 2.77/2.53/2.37 (1.39/1.27/1.19) at 46/52/62 GHz compared to the class-A (class-B) operation. It supports 6-gigabit-per-second (Gb/s) 64-QAM signal with −26.5-dB/−28.3-dBc error vector magnitude (EVM)/adjacent channel leakage ratio (ACLR) at average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {out}}$ </tex-math></inline-formula> /power added efficiency (PAE) of 14.6 dBm/15% at 54 GHz. This work achieves the state-of-the-art bandwidth among silicon-based mmWave PAs where higher than class-B back-off efficiency is achieved.

A New Biorecognition-Element-Free IDμE Sensor for the Identification and Quantification of E. coli.

The label-free biosensor has emerged as an effective tool for the purpose of early detection of causative pathogens such as Escherichia coli as a preventive measure. In this study, a biorecognition-element-free interdigitated microelectrode (IDμE) sensor is designed and developed with this in mind, with good reliability and affordability. Results show that the designed sensor can identify E. coli with good selectivity using an impedance and capacitance of 7.69 MHz. At its optimum impedance of 1.3 kHz, the IDμE sensor can reliably quantify E. coli in a range of measurement (103.2~106 cfu/mL), linearity (R2 = 0.97), sensitivity (18.15 kΩ/log (cfu/mL)), and limit of detection (103.2 cfu/mL). In summary, the IDμE sensor developed possesses high potential for industrial and clinical applications.

A Compact and High-Efficiency Design of 0.915/2.45 GHz Dual-Band Shunt-Diode Rectifier for Wireless Power Transfer

In this letter, a novel structure is proposed for designing dual-band (DB) concurrent operation for the single shunt-diode rectifier configuration, at two highly spaced separate frequency bands, that is, 0.915 and 2.45 GHz for wireless power transfer (WPT). The structure consists of two main parts. The first part uses three transmission lines (TLINs) to match simultaneously optimal impedances from the diode side to the source of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> . The matching TLIN parameters are investigated in the closed-form design equations. The second one acts as a tuning mechanism using a capacitor connected in shunt with the diode to adjust optimal impedances for validating the first-part TLIN parameters in practice. The HSMS2860-based prototype shows that the highest power conversion efficiency (PCE) is achieved at 82.57% and 71.85% for 0.9 and 2.4 GHz, respectively, with the input power of 14 dBm and the resistance load of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$620~\Omega $ </tex-math></inline-formula> . The 50%-over PCE remains within a wide dynamic range of around 14 dB for both frequencies. Compared to the previous state-of-the-art designs, the proposed design exhibits advantages of compactness and high efficiency.

High-Efficiency Broadband Class-E PAs for More Than One Octave: Analysis and Design

This article presents a solution based on continuous mode for designing broadband class-E power amplifiers (PAs), which is realized by transmission of the second-harmonic current with appropriate phase to load network of a class-E PAs. This theory allows selecting appropriate second-harmonic impedance causing part of efficiency to be sacrificed to get a bandwidth over one octave. The mathematical formulation for optimum load impedance in main harmonic, second harmonic, output power, drain efficiency (DE), and load quality factor (QL) is developed in this case. Theoretical results are compared with conventional narrowband class-E counterparts. To check the authentication of mathematical analysis and simulation results, a proof-of-concept broadband continuous-mode class-E PAs is fabricated using the CGH40025F transistor. The manufactured PAs show 43-dBm output power, with average DE 70&#x0025; over the 0.6&#x2013;1.8-GHz frequency range. Also, a narrowband conventional class-E PA for frequency range 1.2&#x2013;1.8 GHz with the same transistor as broadband class-E PA is fabricated for better comparison. The output power and average DE of the conventional class-E PA are 42.5 dBm and 80&#x0025;, respectively.

Design of an Efficient 24–30 GHz GaN MMIC Power Amplifier Using Filter-Based Matching Networks

A broadband GaN MMIC power amplifier (PA) with compact dimensions of 1.94 × 0.83 mm2 is presented for 5G millimeter-wave communication. To guarantee output capability at the operating band edges where serious performance degradation is likely to occur, the appropriate large-signal matching model and optimal impedance domain need to be carefully determined through load-pull analysis. Broadband matching networks (MNs) in the lowpass form are thereafter developed based on the Chebyshev filter synthesis theory. Using high-pass interstage MN in conjunction with parallel RC lossy circuits to compensate for the transistor’s negative gain roll-off slope ensures a flat frequency response. The input MN is designed as a band-pass filter due to the reactance extracted from the input side of the stabilized device exhibiting series LC resonance characteristics. Measured on-wafer pulsed results for the proposed three-stage PA demonstrate up to 30.9 dBm of output power, more than 28.6 dB of small-signal gain, and a peak power-added efficiency (PAE) of 35.6% at 27 GHz. Both uniform gain and saturated output power (Psat) are achieved across 24–30 GHz with fluctuations of less than 0.8 dB.

Compact resonant systems for perfect and broadband sound absorption in wide waveguides in transmission problems

This work deals with wave absorption in reciprocal asymmetric scattering problem by addressing the acoustic problem of compact absorbers for perfect unidirectional absorption, flush mounted to the walls of wide ducts. These absorbers are composed of several side-by-side resonators that are usually of different geometry and thus detuned to yield an asymmetric acoustic response. A simple lumped-element model analysis is performed to link the dependence of the optimal resonators surface impedance, resonance frequency, and losses to the duct cross-sectional area and resonator spacing. This analysis unifies those of several specific configurations into a unique problem. In addition, the impact of the potential evanescent coupling between the resonators, which is usually neglected, is carefully studied. This coupling can have a strong impact especially on the behavior of compact absorbers lining wide ducts. To reduce the evanescent coupling, the resonators should be relatively small and therefore their resonances should be damped, and not arranged by order of increasing or decreasing resonant frequency. Finally, such an absorber is designed and optimized for perfect unidirectional absorption to prove the relevance of the analysis. The absorber is 30 cm long and 5 cm thick and covers a single side of a 14.8 × 15 cm2 rectangular duct. A mean absorption coefficient of 99% is obtained experimentally between 700 and 800 Hz.

Analysis and Design of a 0.3-THz Signal Generator Using an Oscillator-Doubler Architecture in 40-nm CMOS

This paper presents the analysis and design of an oscillator-doubler architecture which is used to generate THz signals. In this architecture, the doubler obtains the optimum fundamental-frequency load impedance for second harmonic generation without causing problems related to instability. The oscillator creates voltages close to the optimum voltage condition, which leads to maximum power being delivered to the doubler connected to the oscillator tank. Compared to a signal generator composed of an oscillator and a conventional doubler with short-circuit load at the fundamental frequency, the proposed circuit has higher output power and DC-to-THz conversion efficiency. Based on this architecture, a 0.3-THz signal generator is designed in 40-nm CMOS. In this 0.3-THz signal generator, an inductor-sharing configuration is proposed to increase the transistor size in the cross-coupled oscillator, thus increasing the power density of the signal generator. Besides, the impact of the doubler fundamental-frequency load impedance on the conversion gain of the doubler is introduced. Also, a method of suppressing the unwanted mode in the cross-coupled oscillator is proposed. The output of this circuit is radiated through on-chip antennas. The measured radiated power and the DC-to-THz efficiency of the chip are -3.8 dBm and 0.37&#x0025;, respectively, with an output frequency tuning range of 4.8&#x0025;.

Parameter Optimization of a Magnetic Coupled Piezoelectric Energy Harvester with the Homogenized Material—Numerical Approach and Experimental Study

This paper presents the process optimization of some key parameters, such as beam spacing, flux density and optimal impedance load matching of magnetic coupled piezoelectric harvesters. In order to do this, the distributed parameters model of this structure, containing macro-fiber components (MFC) with homogenous material in the piezoelectric fiber layer, was determined. Next, the computational model of this structure was designed on the basis of the first-order shear theory (FOST). The performed analysis of the calculated voltage outputs on the basis of the theoretical approach and finite element model by various beam spacing allowed us to indicate that optimized parameters play an important role in enhancing the efficiency of the system. Experiments carried out in a laboratory stand for this structure, allowed for the verification of the numerical results. In the effect, it can be noted that magnetic coupled harvesters will be relevant for a wide range of application sectors, as well as useful for the evolving composite industry.

Thinner Substrate Designs of Modified Ground Plane E–shape Microstrip Antennas for Wideband Response

ABSTRACT Wideband designs of a coaxially fed pair of slot cut square, circular, and equilateral triangular microstrip antennas employing the H-shaped or Bow-tie shaped ground plane profile are presented on an electrically thinner substrate (ht ~ 0.04λg). The modified ground plane yields an optimum impedance matching for the response inside VSWR = 2 circle that gives a wider bandwidth. Among all the slot cut regular shaped microstrip antennas, an optimum response in terms of the bandwidth and gain against the substrate thickness reduction is achieved in E-shaped square microstrip antennas backed by the Bow-tie shaped ground plane. Against the thicker substrate design (ht ~ 0.07λg), it yields bandwidth increment by > 10% and reduction in the substrate thickness by 0.03λg, with a peak broadside gain of 6.2 dBi. An experimental validation is carried out in all the proposed configurations that show close matching with the simulations.

Structure regulation in N-doping biconical carbon frame decorated with CoFe2O4 and (Fe,Ni) for broadband microwave absorption

The typical environment pollution of superfluous microwave radiation has become an urgent problem to be solved at current stage. Herein, a new-style composite of unique biconical carbon framework decorated with CoFe2O4 and (Fe,Ni) nanoparticles was obtained by the co-hydrothermal and pyrolysis route. With the temperature-depended adjustability in microstructure, the composite calcined under 600℃ possesses the largest length–width ratio of amorphous carbon skeleton and the smallest median diameter of decorated NPs among all the samples. This could promote the interface polarization ability and geometrical anisotropy for conductivity, together with N-doping induced dipole polarization, the composite represents excellent dielectric loss capacity for microwave absorption. Moreover, the eddy current effect of magnetic alloy and natural resonance associated with ferrite also assist to this wastage. Under the optimal impedance matching, this composite owns maximal RL of −34.3 dB at 12.92 GHz for 2.0 mm with its broadest effective absorption bandwidth of 6.55 GHz at only 1.87 mm, covering the whole Ku and partial X bands. This work offers a novel microwave absorber with appropriate absorbing intensity and excellent bandwidth for practical usage.