Impedance Matching Technique Research Articles

광대역 초음파 변환기를 위한 전기 임피던스 정합 연구

초음파탐상법을 이용하여 마이크로미터의 크기 작은 결함을 검출하기 위해서는 높은 공진주파수와 큰 분해능의 초음파 변환기가 필요하다. 초음파 변환기의 공진주파수와 분해능은 변환기에 사용된 압전소자의 두께, 후면재 및 탐상 시스템 간의 전기 임피던스 정합과 밀접한 관련이 있으며, 이 중 전기 임피던스 매칭은 초음파 변환기와 초음파탐상 시스템 사이의 서로 다른 입 출력단을 연결하는 과정에서, 두 연결단의 전기적 임피던스 차이에 의한 에너지 반사와 손실을 줄이는 중요한 역할을 한다. 임피던스 정합에서 흔히 많이 사용하는 방법은 LC-정합회로이다. 이러한 LC-정합을 통해 탐상 시스템과 초음파 변환기의 전기 임피던스를 <TEX>$50{\Omega}$</TEX>으로 맞추어 두 연결단 사이의 임피던스 차이를 보정해 줌으로서 초음파 변환기에서 발생되는 전기신호의 손실을 줄 수 있다. 본 연구에서는 15 MHz의 공진주파수를 가지는 광대역 수침형 초음파 탐촉자를 제작하고 광대역 특성을 갖는 초음파 변환기를 위한 LC 임피던스 정합법을 적용하였다. Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of <TEX>${\mu}m$</TEX>) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately <TEX>$50{\Omega}$</TEX> to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.

Impedance Matching Techniques for Microstrip Patch Antenna

Objective: To present a concise and comprehensive summarization of various impedance matching techniques for microstrip patch antennas. Method: Designing an impedance matching network is a central issue for optimum performance in every part of RF systems like transceiver, amplifier and antenna to ensure maximum power transfer. Various design formulae to calculate the input impedance of patch antenna and techniques to design a matching network should be known to RF designer. Finding: In this paper various impedance matching techniques along with their design equations are presented that utilize quarter wave transformer, taper lines, open or short stubs and lumped elements etc. Methods to calculate the input impedance for various antenna structures like rectangular, circular and triangular patch antenna are described. Application: This paper concisely covers some of the existing techniques to design an impedance matching network that can be used to solve the impedance matching problem encountered during antenna design.

Compact log‐periodic dipole array antenna with bandwidth‐enhancement techniques for the low frequency band

A compact planar log-periodic dipole array (LPDA) antenna operating from 0.55 to 9GHz with high measured gain is proposed to be implemented in a reverberation chamber as a source antenna. To minimise the total size of the LPDA antenna, variants of top-loading techniques are utilised, and a much smaller spacing factor is opted to specify the spacing between the elements. However, miniaturisation of the LPDA antenna limits the antenna's wideband characteristics over the desired range of frequencies. Hence, a feedline meander and a trapezoidal stub are incorporated into the design as impedance matching techniques to effectively enhance the bandwidth performance especially for the lower band of the antenna's operating frequency range. The LPDA antenna exhibits radiation patterns with and without a radome having the measured gain ranging from 2.48 to 7.89 dBi and from −1.20 to 7.94 dBi, respectively.

A Performance Enhanced Port Extended Dual-Band Wilkinson Power Divider

A novel dual-band 3-dBWilkinson power divider (WPD) is presented that requires only partial port extension. The design methodology is based on the impedance matching technique and is very simple and intuitive with very simple closed-form formulations. The proposed technique has free variable(s) that add extra flexibility during the design and implementation. Continuous variation of isolation element(s) with band ratio ( $= f_{2}/f_{1}$ ) is no more required and is a distinct feature of this approach when compared with the conventional port extension technique. To enhance the band-ratio further, a technique, which utilizes port extension on all ports, is also demonstrated through an example. The band ratio of the proposed WPD is moderately wide, starting from 1.5 and going beyond 4. A flowchart of the proposed scheme is also reported that aids the systematic design procedure. The presented theory is validated through design and measurement of a prototype fabricated to operate at 0.9/3.5 GHz concurrently. The simulation and the measurement exhibit good agreement.

Design and Simulation for a High-efficiency Class-B Power Amplifier

A class-B power amplifier with high output power and high power added efficiency (PAE) is designed in this paper. Based on the ADS tools of load-pull and source-pull, the optimal load impedance and source impedance can be obtained, respectively. Then, the matching circuit have been achieved by combining the impedance matching technique. Simulation results show that the class-B power amplifier has the PAE of 69.386% and output power of 45.32dBm with the working frequency of 960MHz. Therefore, It is a high-efficiency class-B power amplifier.

Compact Design of Circularly Polarized Antenna with Vertical Slotted Ground for RFID Reader Application

A novel compact circular polarization (CP) microstrip antenna is proposed for UHF ultrahigh frequency (UHF) radio frequency identification (RFID) reader applications. The proposed antenna is composed of a corner truncated square-ring radiating patch on a substrate and a vertical slotted ground surrounding four sides of the antenna. A new feeding scheme is designed from flexible impedance matching techniques. The impedance bandwidths for S11&lt;-10 dB and 3 dB axial ratio (AR) bandwidth are 12.1% (794.5–896.5 MHz) and 2.5% (833.5–854.5 MHz), respectively.

레일 전력선통신을 위한 임피던스 정합방안 연구

장대 터널 및 급곡선 구간과 같은 시계 확보가 어려운 지역에서 위험 및 안전 정보를 함께 공유하기 위해서는 기관사, 열차 관제사 및 현장 작업자 사이에 보조적인 실시간 열차 정보 통신시스템의 개발이 필요하다. 이에 적합한 열차 정보 통신시스템을 개발하기 위하여 본 연구에서는 작은 노이즈와 신호 감쇄를 동시에 갖도록 하는 레일 전력선 통신을 제안하였다. 이에 대한 레일 전력선 통신의 기초 연구 일환으로서, 본 통신기법의 전송 특성을 향상할 수 있는 레일에 대한 임피던스 측정 및 정합특성 평가가 중요하다. 본 연구에서는 자체 제작한 임피던스 정합 트랜스포머와 네트워크 분석기를 이용하여 레일에 대한 반사 및 전파 특성을 평가하였다. 대향 접속방식의 임피던스 반사특성 시험결과로부터 레일 전력선 통신에 적합한 정합용 트랜스포머의 정합비율은 1:3.28임을 알 수 있었다. 또한, 제작한 임피던스 정합용 트랜스포머는 레일 전력선통신에서 투과 신호 전송을 향상할 수 있음을 확인하였다. An auxiliary real-time train communications system among drivers, train-traffic controllers and field workers is necessary to share hazard information (i.e. rockfall detection, track maintenance) in low visibility zones (long tunnels and steep curved track). To develop the appropriate communication system, this paper proposes a new way of power line communication using the rail track (Rail - PLC), which has little noise and distortion of attenuation. Therefore, it is important to measure the impedance of the rail and to apply an impedance matching technique to increase the transmission characteristic of the Rail - PLC. This study would evaluate the reflection and the transmission characteristics of the rail using a network analyzer and an impedance matching transformer. The suitable impedance matching ratio was 1:3.28 from the result of back-to-back testing. The results confirmed that the transformer can improve the performance of the transmission signal in Rail - PLC using an impedance matching technique.

Wireless power transfer based on dielectric resonators with colossal permittivity

Magnetic resonant wireless power transfer system based on dielectric disk resonators made of colossal permittivity (ε = 1000) and low loss (tan δ = 2.5 × 10–4) microwave ceramic is experimentally investigated. The system operates at the magnetic dipole mode excited in the resonators providing maximal power transfer efficiency of 90% at the frequency 232 MHz. By applying an impedance matching technique, the efficiency of 50% is achieved within the separation between the resonators d = 16 cm (3.8 radii of the resonator). The separation, misalignment and rotation dependencies of wireless power transfer efficiency are experimentally studied.

Measurements of the principal Hugoniots of dense gaseous deuterium−helium mixtures: Combined multi-channel optical pyrometry, velocity interferometry, and streak optical pyrometry measurements

The accurate hydrodynamic description of an event or system that addresses the equations of state, phase transitions, dissociations, ionizations, and compressions, determines how materials respond to a wide range of physical environments. To understand dense matter behavior in extreme conditions requires the continual development of diagnostic methods for accurate measurements of the physical parameters. Here, we present a comprehensive diagnostic technique that comprises optical pyrometry, velocity interferometry, and time-resolved spectroscopy. This technique was applied to shock compression experiments of dense gaseous deuterium–helium mixtures driven via a two-stage light gas gun. The advantage of this approach lies in providing measurements of multiple physical parameters in a single experiment, such as light radiation histories, particle velocity profiles, and time-resolved spectra, which enables simultaneous measurements of shock velocity, particle velocity, pressure, density, and temperature and expands understanding of dense high pressure shock situations. The combination of multiple diagnostics also allows different experimental observables to be measured and cross-checked. Additionally, it implements an accurate measurement of the principal Hugoniots of deuterium−helium mixtures, which provides a benchmark for the impedance matching measurement technique.

General Method for Characterization of Power-Line EMI/RFI Filters Based on S-Parameter Evaluation

This paper deals with a general working approach for determining the lowest possible insertion loss of power-line interference filters in their stop bands at high megahertz or gigahertz frequencies. It is shown that at these frequencies, the measurement methods recommended for testing of interference filters in available standards for frequencies up to 1 GHz fail in determining their lowest possible insertion loss. This problem is solved by the newly developed method which also enables the characterization of concerned filters in a completely impedance unknown environment. It is based on two-port vector network analyzer measurement and postmeasurement data processing applying an impedance matching technique. Experimental verification of the new method using two Maury Microwave automated tuners and a cascade of low-pass coaxial filters was performed in the frequency band from 6 to 12 GHz. The results show that measurement-evaluation procedures performed according to the newly developed method provide more reliable and precise results when compared to measurement procedures corresponding to methods described in common standards. The new method was also applied to the characterization of a professional EMI/RFI filter from 1 to 10 GHz.

Droplet sensing using small and compact high-Q planar resonator based on impedance matching technique.

In this paper, we demonstrate the sensing feasibility of the proposed high-Q resonator using a phosphate-buffered saline droplet at microwave frequencies. In the experimental results, the resonant frequency, signal level, and Q-factor of the S21-parameter with and without a 1-μl droplet were changed to about 230 MHz, 32 dB, and 1500, respectively. The resonator system was found to be suitable for droplet sensing with a small volume due to its small and compact scheme. This resonator system is expected to play an important role in droplet sensing with different dielectric constants.

A Novel Six-Band Dual CP Rectenna Using Improved Impedance Matching Technique for Ambient RF Energy Harvesting

A novel six-band dual circular polarization (CP) rectenna for ambient radio frequency (RF) energy harvesting is presented. Due to the nonlinearity and complex input impedance of the rectifying circuit, the design of a multiband and/or broadband rectenna is always challenging and its performance can be easily affected by variation in the input power level and load. Therefore, an improved impedance matching technique is introduced, which is aimed to improve the performance of the rectifier with a varying condition. A broadband dual CP receiving antenna is proposed, which has a very wide bandwidth (from 550 to 2.5 GHz) and a compact size. An annular ring structure and a novel feeding technique are employed in order to reduce the size and improve the antenna performance. As a result, the proposed rectenna is the first design that covers six frequency bands, including part of the digital TV and most cellular mobile and WLAN bands in the U.K., while the optimal load range for a constant conversion efficiency is from 10 to 75 $\text{k}\Omega $ . The measured results show that the maximum harvested dc power of the rectenna in typical outdoor and indoor environments are 26 and 8 $\mu \text{W}$ , respectively; it can therefore be applied to a range of low-power wireless applications.

Fishbone-Like High-Efficiency Low-Pass Plasmonic Filter Based on Double-Layered Conformal Surface Plasmons

In this work, we report a fishbone-like high-efficiency low-pass plasmonic filter based on a double-layered conformal surface plasmon waveguide (CSPW) which consists of double-layered symmetrical metal gratings (SMGs) of fishbone shape. Efficient mode conversion between the quasi-transverse electromagnetic (TEM) waves in the microstrip line and the conformal surface plasmons (CSPs) on the double-layered CSPW is realized by using gradient double-layered SMGs and impedance matching technique. Experimental results of the transmission and reflection coefficients of the straight sample show excellent loss-pass performance and agree well with the numerical simulations. The curved samples exhibit low radiation loss when the double-layered CSPW is conformal or even bent thanks to the high confinement of CSPs. The proposed structure can find potential applications in integrating conventional circuits with CSPs devices at microwave and terahertz frequencies.

Improving the bandwidth of the transimpedance amplifier based on CS stages in cascode configuration using impedance matching techniques

This paper describes a matching technique to improve the bandwidth of multi-GHz frequency ranges for the transimpedance amplifier. It is shown that by simultaneously using of series input matching ...

Impedance Matching for Compact Multiple Antenna Systems in Random RF Fields

We investigate the maximization of the received power from compact multiple antenna systems in random RF fields, using two novel impedance matching approaches. The first approach is based on optimal impedance matching where we use convex optimization to propose a sparse optimal impedance matching technique. The second approach is obtained by further relaxing the sparse optimal impedance matching method to obtain a suboptimal impedance matching (SOM) method we refer to as multiport ladder matching (MLM). Simulation results show that the sparse optimal impedance matching approach provides the maximum received power while MLM can capture more power than conventional single-port matching (SPM). Additionally, they can maintain good bandwidth indicating the effectiveness of the sparse optimal and multiport ladder impedance matching approaches.

The Hugoniot and chemistry of ablator plastic below 100 GPa

The equation of state of glow discharge polymer (GDP) was measured to high precision using the two-stage light gas gun at Lawrence Livermore National Laboratory at pressures up to 70 GPa. Both absolute measurements and impedance matching techniques were used to determine the principal and secondary Hugoniots. GDP likely reacts at about 30 GPa, demonstrated by specific emission at 450 nm coupled with changes to the Hugoniot and reshock points. As a result of these reactions, the shock pressure in GDP evolves in time, leading to a possible decrease in pressure as compression increases, or negative compressibility, and causing complex pressure profiles within the plastic. Velocity wave profile variation was observed as a function of position on each shot, suggesting some internal variation of GDP may be present, which would be consistent with previous observations. The complex temporal and possibly structural evolution of GDP under shock compression suggests that calculations of compression and pressure based upon bulk or mean measurements may lead to artificially low pressures and high compressions. Evidence for this includes a large shift in calculating reshock pressures based on the reflected Hugoniot. These changes also suggest other degradation mechanisms for inertial confinement fusion implosions.

Two-side Impedance Matching for Maximum Wireless Power Transmission

ABSTRACTThe research on high-efficient non-radiant wireless power transmission (WPT) system using high-quality factor resonant coupled coils has become remarkable for powering various portable household devices, biomedical implants, and electrical vehicles since last decade. Therefore, practical WPT must be able to support complicated coil configurations and keep following magnetic resonant conditions with maximum power transfer capability during coupling distance variation. In this paper, an adaptive two-side impedance matching technique using self-tuned L-matching circuits at both the transmitting and receiving sides is proposed for maximizing transmission efficiency in resonant coupled WPT system. The tuning value of inductance and capacitance for matching networks are derived based on the Q-based design principle, and extracted impedance ratios and S-parameters. The feasibility of the theoretical model is testified against simulation and measured data. The developed model shows that using two-side matching technique maximizes transmission efficiency over 80% for a range of 15–35 cm. The proposed technique also successfully retains the resonant frequency and is much more potential to provide maximum efficiency for the resonant coupled WPT system.

Range-Adaptive Wireless Power Transfer Using Multiloop and Tunable Matching Techniques

In this paper, a range-adaptive wireless power transfer (WPT) system is proposed to achieve high efficiency over a wide range of distances by using tunable impedance matching techniques. A multiloop topology is employed to greatly reduce the variation in the input impedance of the WPT system with respect to the distance, where one of the four loops with a different size is selected, depending on the distance. It enables the design of a simple tunable matching circuit using a single variable capacitor. An algorithm is written to find the optimum loop and capacitance in the matching network, based on the measured input return loss using a directional coupler and rectifiers. The fabricated WPT system shows a range-adaptive operation with high efficiency over a wide range of distances. It attains 48% efficiency at a distance of 100 cm with a maximum efficiency of 92% at a distance of 10 cm.

Broadband high performance laterally diffused metal–oxide–semiconductor power amplifier for mobile two‐way radio applications

This paper highlights achievement of broadband high performance power amplifier (PA) line up for mobile two-way radio applications. In typical two-way radio applications the input radio-frequency signal to the first PA stage comes directly from the voltage controlled oscillator, with typically 3 dBm power. Owing to high output power requirement (∼80 W) of mobile radio applications, up to three PA device stages are normally cascaded (pre-driver, driver and final PA stage). The key point in the design of the PA line up concerns the final stage. Here, this paper introduces a design methodology based on parallel-combined impedance matching technique (from theoretical derivation) enables the designers to develop broadband PA with actual PA device impedance (implementation of new generation laterally diffused metal–oxide–semiconductor device). Experimental results demonstrated output power of ∼80 W and gain of 45 dB, while preserving efficiency of 55% over the bandwidth from 760 to 870 MHz. According to author's knowledge, this amplifier demonstrated highest efficiency with 13 V DC supply (operating at 80 W) in UHF broadband frequency with high gain operation (more than 45 dB) up to date.

Low‐cost E‐band Lange coupler with vialess load

A vialess E-band Lange coupler is presented. The design combines a novel `pseudo-dot' termination with impedance matching techniques. The multiple stage impedance matching network technique is used to design a 50 Ω Lange coupler. The `pseudo-dot' termination provides a suitable load to the isolation port, avoiding via connection to ground, thus reducing the cost of the fabrication process. The design achieves better than 2 dB insertion losses in the through and coupled paths with <;0.8 dB amplitude and ±2° phase errors for the entire E-band.