Conjugately Characteristic-impedance Transmission Lines Research Articles

Generalized Complex-to-Complex Impedance Transformers Based on Conjugately Characteristic-Impedance Transmission Lines

The novel technique of generalizing complex-to-complex impedance transformers (CCITs) with miniaturization is introduced in this paper. The generalized CCITs are designed based on conjugately characteristic-impedance transmission lines (CCITLs) along with the Meta-Smith charts (MSCs), resulting in convenient design equations. For illustration, a prototype of generalized CCITs is designed, simulated, and implemented with an asymmetric compact microstrip resonant cell (ACMRC), which is one of the CCITLs. The measurement results confirm that the proposed technique offers approximately 28.5% shorter in physical length compared to the CCIT designed using standard transmission lines.

Design of Reactance-to-Reactance Impedance Transformers Based on Conjugately Characteristic-Impedance Transmission Lines (CCITLs) and Meta-Smith Charts (MSCs)

Design of Reactance-to-Reactance Impedance Transformers Based on Conjugately Characteristic-Impedance Transmission Lines (CCITLs) and Meta-Smith Charts (MSCs)

An efficient analysis of the far-field radiation of an electric/magnetic Hertzian dipole embedded in electromagnetic bandgap structures of periodic lossless multilayers using the equivalent CCITL model

In this paper, the far-field radiation of a Hertzian dipole embedded in electromagnetic bandgap structures of periodic lossless multilayers is studied analytically and numerically. To simplify the analysis of this radiation problem, the equivalent transmission line (TL) model based on conjugately characteristic-impedance TLs (CCITLs) is employed to efficiently compute the far-field radiation of the Hertzian dipole due to the periodic nature of the problem, where associated reflection coefficients, which are useful in computing far fields, can be determined effectively. It is found that numerical results based on the equivalent CCITL model are in very good agreement with those obtained from a commercial electromagnetic software.

Forbidden regions of L‐section impedance matching networks on Meta‐Smith charts for conjugately characteristic‐impedance transmission lines

ABSTRACTIn this article, the ZY Meta‐Smith chart (MSC) is applied to intuitively determine a forbidden region for all eight L‐section matching networks associated with conjugately characteristic‐impedance transmission lines (CCITLs) with nonnegative characteristic resistances (NNCRs), where a load impedance cannot be matched to a CCITL. Due to the fact that the ZY MSC for CCITLs with NNCRs depends on the argument ϕ of the characteristic impedances of CCITLs (which can be negative, zero, or positive), three cases for each L‐section matching network are considered to determine the effect of the argument ϕ on forbidden regions, resulting in a total of 24 cases for all L‐section matching networks. It is found that the ZY MSC for CCITLs with NNCRs is indeed a useful graphical tool for enabling intuition for radio‐frequency engineers with additional physical insight into impedance matching of L‐section matching networks. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:874–879, 2015

Effective Analysis of Terminated Lossless Planar Multilayer Periodic EBG Structures Using an Equivalent Transmission‐Line Model with Meta‐Smith Charts

ABSTRACTLossless planar multilayer periodic electromagnetic bandgap (EBG) structures of dielectric media, illuminated by an oblique electromagnetic plane wave and terminated in a surface impedance with an arbitrary number of multilayers in a unit cell, can be effectively analyzed using an equivalent transmission‐line (TL) model based on conjugately characteristic‐impedance TLs (CCITLs). In this article, both characteristic impedances with nonnegative characteristic resistances (NNCRs) and negative characteristic resistances (NCRs) associated with CCITLs are considered. It is found that the equivalent CCITL model yields accurate results, and can simplify the analysis of these EBG structures with some physical insight. In addition, Meta‐Smith charts (MSCs) can be employed to further simplify the analysis. It is found that MSCs can provide clearer data set than the standard Smith chart with accurate results, and the bilinear transformation can be effectively used to transform dataset between MSCs and the Smith chart. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2222–2228, 2013

Physical interpretation of negative characteristic resistances associated with lossless periodic transmission line structures

AbstractThis article presents a physical interpretation of negative characteristic resistances (NCRs) associated with lossless periodic transmission line (TL) structures using the model of conjugately characteristic‐impedance transmission lines (CCITLs).Interestingly, the CCITL model of lossless periodic TL structure can exhibit both non‐negative characteristic resistances (NNCR) and NCRs with appropriate propagation constants. Nevertheless, the physical meaning for the NCR case is still ambiguous. To physically interpret the NNCR and NCR cases, it is found that the propagation constant plays an important role. In addition, the suitable definitions of incident and reflected waves for both NNCR and NCR cases are also provided. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1180–1183, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26796

THEORETICAL STUDY OF MICROWAVE TRANSISTOR AMPLIFIER DESIGN IN THE CONJUGATELY CHARACTERISTIC-IMPEDANCE TRANSMISSION LINE (CCITL) SYSTEM USING A BILINEAR TRANSFORMATION APPROACH

Conjugately characteristic-impedance transmission lines (CCITLs) are a class of transmission lines possessing conjugately characteristic impedances (Z § 0 ) for waves propagating in the opposite direction. A typical Z0 uniform transmission line is a special case of CCITLs whose argument of Z § is equal to 0 - . This paper aims to generalize the CCITL system by demonstrating a theoretical study of CCITLs and their applications in the microwave transistor amplifler design. It is found that the bilinear transformation plays an important role in transforming circles in the re∞ection coe-cient i0-plane in the Z0 system to the i-plane in the CCITL system. In addition, Meta- Smith charts, a graphical tool developed for solving problems in the CCITL system, are employed to design matching networks to achieve desired amplifler properties. Results show that stability regions on Meta-Smith charts can be determined, and source and load re∞ection coe-cients can be selected properly to obtain desired operating power gain. In addition, an example shows that Meta-Smith charts ofier a simple approach for matching network design using open-circuited single-stub shunt tuners.

NON-UNIQUENESS OF T-CHARTS FOR SOLVING CCITL PROBLEMS WITH PASSIVE CHARACTERISTIC IMPEDANCES

Conjugately characteristic-impedance transmission lines (CCITLs) implemented by lossless periodic transmission-line struc- tures have found various applications in microwave technology, and the T-chart was developed to perform the analysis and design of CC- ITLs efiectively. Originally, the normalization factor used in defln- ing normalized impedances of the T-chart is the geometric mean of characteristic impedances of CCITLs, which is not only one possible choice. By using other normalization factors based on characteristic impedances, difierent graphical representations can be obtained; i.e., T-charts for CCITLs with passive characteristic impedances are not unique, and it depends on the associated normalization factor. In this study, three more possible normalization factors related to char- acteristic impedances of CCITLs are investigated. It is found that all T-charts for each normalization factor are strongly dependent on the argument of characteristic impedances of CCITLs in a complicated fashion. The original T-chart based on the geometric mean of char- acteristic impedances is found to be the most convenient graphical representation for solving CCITL problems.

EQUIVALENT GRAPHICAL SOLUTIONS OF TERMINATED CONJUGATELY CHARACTERISTIC-IMPEDANCE TRANSMISSION LINES WITH NON-NEGATIVE AND CORRESPONDING NEGATIVE CHARACTERISTIC RESISTANCES

EQUIVALENT GRAPHICAL SOLUTIONS OFTERMINATED CONJUGATELY CHARACTERISTIC-IMPEDANCE TRANSMISSION LINES WITH NON-NEGATIVE AND CORRESPONDING NEGATIVE CHAR-ACTERISTIC RESISTANCESD. Torrungrueng and S. LamultreeDepartment of Electrical and Electronic EngineeringFaculty of Engineering and TechnologyAsian UniversityChon Buri, 20250, ThailandAbstract—This paper presents the graphical solutions of conjugatelycharacteristic-impedance transmission lines (CCITLs) implemented byperiodically loaded lossless transmission lines (TLs), which can exhibitboth non-negative (NNCR) and negative characteristic resistances(NCR) with the corresponding propagation constants. The standardT-chart and the extended T-chart are employed to solve CCITLproblems with NNCR and NCR cases respectively, depending on theargument of CCITL characteristic impedances. The range of plottingof the standard T-chart and the extended T-chart is always insideor on the unit circle, and always outside or on the unit circle of thevoltage reflection coefficient plane, respectively. Two examples of finiteperiodicTLstructuresprovidingbothNNCRandNCRcasesaregiven.It is found that both T-charts provide the same input impedance ofthe corresponding CCITLs as expected, and the standard T-chart ismore familiar and easier to deal with.1. INTRODUCTIONOne class of transmission lines (TLs), called conjugately characteristic-impedance transmission lines (CCITLs), has been introduced recentlyin the literature [1–7]. By definition, a CCITL possesses conjugatecharacteristic impedances

Theory of Small Reflections for Conjugately Characteristic-Impedance Transmission Lines

In this letter, the standard theory of small reflections (TSR) is generalized for the case of multi-section transformers, composed of conjugately characteristic-impedance transmission lines (CCITLs) connected in cascade, with small discontinuities. Using the assumption of small reflections, the total voltage reflection coefficient looking into the input of the transformer can be approximated, resulting in the TSR for multi-section CCITL transformers with small discontinuities. Numerical results, some physical interpretations and potential applications of results will be discussed in this letter.

A graphical tool for analysis and design of bi‐characteristic‐impedance transmission lines

AbstractThe bi‐characteristic‐impedance transmission lines (BCITLs) are generally lossy transmission lines that possess different complex characteristic impedances for waves propagating in forward and reverse directions. Because of complicated equations associated with BCITLs, a graphical tool is necessary in the analysis and design. In this article, the standard T‐chart developed for conjugately characteristic‐impedance transmission lines (CCITLs) is generalized to treat BCITL problems, called a generalized T‐chart. It is found that the way of using this new graphical tool is similar to that of the standard T‐chart. However, the magnitude of the voltage reflection coefficient associated with BCITLs may be greater than unity for some passive load terminations. An example of using a generalized T‐chart is provided in this paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2368–2372, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22801

An extended ZY T‐chart for conjugately characteristic‐impedance transmission lines with active characteristic impedances

AbstractIt has been shown recently in the literature that the conjugately characteristic‐impedance transmission lines (CCITLs) implemented by periodically loaded lossless lines can exhibit active characteristic impedances (i.e., negative characteristic resistances). In this case, the magnitude of the voltage reflection coefficient is always greater than or equal to unity for passive load termination. Because of this reason, some modifications to the standard T‐chart, a graphical tool for solving CCITL problems, is necessary. The modified chart is called as an extended ZY T‐chart, where the range of plotting is always outside or on the unit circle of the voltage reflection coefficient Γ plane. It is found that the extended chart depends on the angle ϕ, the argument of the CCITL characteristic impedances, in a complicated fashion. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1961–1964, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22626