摘要 :
This paper investigates the impedance boundary of impedance matching networks analytically, graphically representing the resultant impedance matching domains. A set of explicit equations is derived to allow the rapid development o...
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This paper investigates the impedance boundary of impedance matching networks analytically, graphically representing the resultant impedance matching domains. A set of explicit equations is derived to allow the rapid development of the impedance boundary of such networks. The equations are analyzed thoroughly, such that the impact each component has upon the resultant domain may be obtained. These equations are then developed further to provide a design procedure enabling a matching network to be designed to achieve impedance matching in a specific impedance domain given the source impedance and operating frequency.
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In this study, a practical and useful dual-frequency property of two-section transmission line (TSTL) terminated into a real impedance is reported. Moreover, to demonstrate some of its potential applications for the performance en...
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In this study, a practical and useful dual-frequency property of two-section transmission line (TSTL) terminated into a real impedance is reported. Moreover, to demonstrate some of its potential applications for the performance enhancement in dual-frequency impedance transformation problems, modified L- and T-type dual-frequency matching networks are presented. Specifically, the property is used to modify the conventional L-type matching network to improve its transformation-ratio and frequency-ratio performance. Furthermore, improvement in conventional dual-frequency T-type matching network is also demonstrated through the incorporation of the TSTL. All the results are analytical and in closed form with simple design equations. For validation, prototypes of the proposed L- and T-type matching networks operating concurrently at 1 GHz/1.45GHz and 1 GHz/2GHz, respectively, are designed and fabricated on FR-4 substrate. The obtained simulated and measured results clearly exhibit the usefulness of the proposed design schemes.
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The impedance of an antenna changes heavily with changing EM environments, while RF power amplifiers (PAs) are optimized for driving a well-defined load impedance. As a solution, switchable matching networks are used in automatic ...
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The impedance of an antenna changes heavily with changing EM environments, while RF power amplifiers (PAs) are optimized for driving a well-defined load impedance. As a solution, switchable matching networks are used in automatic antenna tuners to match the antenna impedance to (about) the desired PA load impedance. This paper presents a theoretical treaty of the minimum number of required states for switchable matching networks to achieve sufficient matching from a certain load VSWR to a sufficiently low input VSWR. First for an arbitrary passive lossless switchable matching network, the mathematical minimum required number of states as a function of the required input VSWR and of the required load VSWR is derived. Several variants are analyzed and benchmarked: single-stage one-ring configuration, single-stage two-ring configuration, two-stage one-ring configuration and three-stage one-ring configuration showing that single-ring configurations are optimum. An extension towards the required number of states for lossy matching networks is also provided.
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This paper presents a procedure for determining the practically achievable bandwidth of a strongly frequency-dependent load impedance when using a simple matching circuit. The main target application is mobile handset antennas, wh...
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This paper presents a procedure for determining the practically achievable bandwidth of a strongly frequency-dependent load impedance when using a simple matching circuit. The main target application is mobile handset antennas, which might be inherently nonresonant and thus the achievable bandwidth is not known from the input impedance. A straightforward and efficient algorithm for determining various bandwidth estimators is presented. A compact dual-band WLAN antenna is then designed, manufactured, and measured as an example application of utilizing the bandwidth estimators. Another example demonstrates how the bandwidth estimators can be used to determine a matching and decoupling circuit for a symmetrical dual-element antenna. The results show that the bandwidth estimators can be used as a supplementary tool in antenna design, transferring a part of the design challenge from electromagnetics to circuit design.
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Electrical impedance matching network (EIMN) is important for the piezoelectric transducer to transmit high-power acoustic signal over a wide bandwidth. Different from the impedance matching between transducers and interface devic...
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Electrical impedance matching network (EIMN) is important for the piezoelectric transducer to transmit high-power acoustic signal over a wide bandwidth. Different from the impedance matching between transducers and interface devices with a fixed impedance of 50 Omega, this paper presents a novel method of designing an EIMN between transducer and power amplifier (PA) based on matching transformer. First, the equivalent model of the transducer is identified through nonlinear regression process. Then, the matching transformer is designed to meet the specifications of impedance matching and high power operation. To ensure the maximum output power of the PA, a matching transformer is designed to match the impedance of the transducer to a specific resistance which is equal to the ratio of the maximum voltage to the maximum current of the PA. The proposed approach contributes to determining the optimal turns ratio of the matching transformer based on the calculation of the optimal output impedance of the PA. Simulation results demonstrate that the transformer-based EIMN, whose design process is simpler, performs as well as LC-based EIMNs. Experiment based on a B class PA proves the effectiveness and desired performance of the transformer-based EIMN.
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Many antennas can be characterized by their radiation Q (the ratio of reactance to radiation resistance). A classic problem is determining the maximum possible bandwidth, constrained by the maximum permissible reflection magnitude...
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Many antennas can be characterized by their radiation Q (the ratio of reactance to radiation resistance). A classic problem is determining the maximum possible bandwidth, constrained by the maximum permissible reflection magnitude, and the number of tuned circuits in the impedance-matching circuit. This paper presents a review on theoretical limitations of narrowband impedance matching.
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High-power radio frequency (RF) heating system in the frequency range of ion cyclotron range of frequencies (ICRF) on tokamak needs a mechanism for matching impedance seen by the antenna in presence of plasma to the generator outp...
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High-power radio frequency (RF) heating system in the frequency range of ion cyclotron range of frequencies (ICRF) on tokamak needs a mechanism for matching impedance seen by the antenna in presence of plasma to the generator output impedance for maximum transfer of RF power to the plasma with minimum reflections to avoid damage to the generator. The impedance of the antenna is strongly dependent on edge plasma parameters and the impedance sometimes changes as fast as 10(-4) s, while the RF generators used can deliver full power only into constant load impedance. Hence, the matching system with dynamic response in between generator and antenna is very much essential for high power ICRF experiments when the plasma is of longer duration with variable load impedance. For ICRF system on SST-1 tokamak, two automatic matching systems are employed each for one transmission line, which consists of motorized stub tuners and phase shifters to match the antenna impedance in the time scale of 120 ms. As a part of initial testing, online impedance matching system is tested with individual transmission lines and then both the lines are matched simultaneously on a variable dummy load which simulates the plasma load. In order to deliver power to both the lines from a single RF generator, hybrid coupler is used which also protects RF generator from reflections up to certain extent. However for hybrid coupler has to work properly and both the lines should see same load impedance. The automatic matching system is installed on tokamak state super-conducting tokamak (SST-1) and is tested up to 140 kW power in the vacuum vessel of the tokamak. Here we present the details of the online matching system and its testing results. The significant result is that we could match the variable load impedance with the generator impedance within 120 ms by suitably adjusting the step counts of the motor controller. (C) 2015 Elsevier B.V. All rights reserved.
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This letter presents analysis and design considerations for lumped (inductor and capacitor) matching networks operating at high efficiency ($≫$95%). Formulas for calculating matching network efficiency are given, and it is shown ...
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This letter presents analysis and design considerations for lumped (inductor and capacitor) matching networks operating at high efficiency ($≫$95%). Formulas for calculating matching network efficiency are given, and it is shown that efficiency can be expressed as a function of inductor quality factor$Q_L$, capacitor quality factor$Q_C$, and transformation ratio. These formulas are used to evaluate the optimum number of$L$-section matching stages as a function of conversion ratio. Both simulation and experimental results are presented that validate the analytical formulation.
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Based on Wheeler's transformation of multilayer microstrip line, velocity and impedance matching have been analyzed for polymer electro-optic (EO) modulator. Due to the advantages of polymer materials, velocity-matching and impeda...
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Based on Wheeler's transformation of multilayer microstrip line, velocity and impedance matching have been analyzed for polymer electro-optic (EO) modulator. Due to the advantages of polymer materials, velocity-matching and impedance-matching can be simultaneously achieved by optimized design for multilayer microstrip electrode. A modified modulator structure has been introduced with a compensation layer placed on the electrode to adjust the microwave index and characteristic impedance. The optimal thicknesses of electrode and compensation layer, and optimal width of electrode can make the EO modulator achieve both velocity matching and impedance matching.
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The simplest network for matching a load resistance to a source resistance at a single frequency is analyzed to find an expression for the matching bandwidth with a specified tolerance on the reflection coefficient. The results ...
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The simplest network for matching a load resistance to a source resistance at a single frequency is analyzed to find an expression for the matching bandwidth with a specified tolerance on the reflection coefficient. The results are used to find the characteristics of dual- and triple-frequency impedance matching networks, designed by applying frequency transformation to the single-frequency network. Finally, comments are made about some general features of multiple-frequency matching networks.
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