Coupled Coplanar Waveguide Research Articles

Compact filtering power divider for mm‐wave applications using integrated passive device technology

AbstractWe present a compact, filtering power divider (FPD) using integrated passive device technology (IPD) for mm‐wave applications. Our proposed FPD design integrates quarter‐wavelength coupled‐resonator bandpass filters with a Wilkinson power divider, using size reduction techniques. Coupled coplanar waveguides provide excellent coupling while occupying a small area, and metal‐insulator‐metal capacitors offer the required λ/4 phase shift without length extension. The center frequency of the filtering power divider/combiner (FPD/C) is located at 30‐GHz. We demonstrate our FPD design by fabricating four prototypes with parameter variations. The insertion loss, fractional bandwidth, and size of the FPD/C designed in this study are from 2.56 to 3.3 dB, from 9.67% to 19.4%, and from 0.592 to 0.220‐mm2, respectively. In addition, the return loss of all models at the center frequency is 28.5 dB or more, and the isolation is 16.6 dB or more.

Fuzzy models for quasi‐static calculations of single ground plane coupled CPW by CADMFILT software

AbstractIn this paper, two new subdesign tools including the quasi‐static and fuzzy model calculations for the electrical parameters of the coupled planar transmission lines used in the design of microwave communication subsystems including resonators, filters, and multiplexers are presented for CADMFILT software. Proposed subdesign tools have properties such as electrical parameter calculations for microwave circuit analysis/synthesis, fuzzy logic model applications, comparisons, and graphical demonstrations. The first subdesign tool can calculate the electrical parameters of the coupled planar transmission lines by using the quasi‐static analysis method. The other tool is based on subtractive fuzzy clustering, which can offer approximate solutions as an alternative to numerical and analytical closed‐form expressions of quasi‐static analysis. The proposed subdesign tools have a competent and efficient algorithm to provide fast, accurate, and sensitive results. To test the accuracy of these tools, a coupled coplanar waveguide with a single ground plane structure has been performed. The results obtained from the subdesign tools for both approaches have been compared. The proposed fuzzy logic models use the electrical parameters calculated from the quasi‐static analysis as training and control data files. The accuracy of each model has been tested by error analysis and the validity of the model results has been demonstrated by comparing them with the results of the quasi‐static approach. It is expected that the developed efficient, fast, and versatile subdesign tools will help researchers to simplify their designs by providing a control mechanism in the RF/microwave circuit design processes.

A Nanoplasmonic Branchline Coupler for Subwavelength Wireless Networks

This article presents the new nanoplasmonic branchline coupler (BLC) by using an edge coupled coplanar waveguide (CPW) with a finite length suspended backed conductor. The proposed coupler is designed by using the theoretical transmission line (TL) method, which is established based on the basic characteristics of the related CPW structures. For this purpose, the normalized propagation constant, propagation length, and characteristic impedance of the conductor backed coplanar waveguide (CBCPW) structure are studied and analyzed by applying a fullwave analysis using CAD simulation software tool CST microwave studio suite. Mainly, the coupling coefficient of the BLC can be controlled by changing the length of the backed conductor. In this article, the BLC is designed and analyzed by using a finite length backed conductor based on the theoretical TL method at a 3-dB coupling coefficient. This newly designed coupler can operate at two arbitrary optical frequency bands (O-band and L-band). Hence, it allows us to exchange many other couplers with their narrow bandwidths using this branchline coupler for subwavelength nanoscale wireless network applications and photonic integrated circuits (PICs).

Up to 80 Gbaud DP‐16QAM operation using InP‐based high‐bandwidth coherent driver modulator

The authors obtained very good back-to-back bit error rate performance in up to 80 Gbaud DP-16QAM operation by using their coherent driver modulator of a 3-dB electro-optic bandwidth of over 50 GHz. To achieve high bandwidth and good signal integrity, they used double ultra-low loop wires between the driver IC and the modulator and a differential capacitively loaded travelling-wave RF electrode based on straight coupled coplanar waveguide with a ground-signal-signal-ground configuration for their InP modulator. As far as they know, this is the highest bandwidth and baud rate operation so far for the high-bandwidth coherent driver modulator configuration.

On-Wafer Coplanar Waveguide Standards for S-Parameter Measurements of Balanced Circuits Up to 40 GHz

The multimode thru-reflect-line (TRL) calibration technique is applied to perform on-wafer mixed-mode scattering-parameter (S-parameter) measurements for differential circuits. This paper describes the first design and realization of a coupled coplanar waveguide (CCPW) calibration kit on a quartz substrate in the ground-signal-ground-signal-ground configuration. CCPW integrated verification elements such as attenuators, and matched and mismatched transmission lines are simulated and measured to validate the design of the multimode TRL calibration kit as well as the calibration algorithm itself. With the advent of four-port vector network analyzers supporting true mode stimulus, at least two approaches are available for mixed-mode S-parameter measurements. The first one is the one-tier measurement using the single-ended stimulus with the multimode TRL calibration technique. The second one relies on the two-tier measurement with a short-open-load-reciprocal thru calibration at the first tier and the multimode TRL calibration at the second tier. From the viewpoint of metrology, the one-tier approach is preferable as it requires fewer standards and connections. The good agreement between simulation and measurement results performed on different verification elements demonstrates the validity of both methods up to 40 GHz.

Design of Miniaturized Vertical Split-Ring Resonator Based on Coupled Coplanar Waveguide

In this letter, a vertical split-ring resonator (VSRR) based on a coupled coplanar waveguide (CCPW) is proposed to reduce the longitudinal length of a VSRR. The resonant condition of the proposed resonator is obtained using the transmission line theory and the odd-mode analysis. The longitudinal length of the resonator is reduced using the CCPW. From full-wave simulations, the relationship between the loaded bandwidth and design parameters is investigated. The proposed design to miniaturize the resonator was fabricated and measured, and it is verified that the effective longitudinal length of the proposed VSRR based on CCPW is reduced by 50% compared with the previous VSRR.

Quality factor of a transmission line coupled coplanar waveguide resonator

We investigate analytically the coupling of a coplanar waveguide resonator to a coplanar waveguide feedline. Using a conformal mapping technique we obtain an expression for the characteristic mode impedances and coupling coefficients of an asymmetric multi-conductor transmission line. Leading order terms for the external quality factor and frequency shift are calculated. The obtained analytical results are relevant for designing circuit-QED quantum systems and frequency division multiplexing of superconducting bolometers, detectors and similar microwave-range multi-pixel devices.

Negative-Inductance Superconducting Quantum Interference Device With Energy Dissipation of 1.38 zJ/bit Measured by Inductively Coupled Coplanar Waveguide Resonator

High energy-efficient superconducting circuits are increasingly desirable for information technology. Negative-inductance superconducting quantum interference device (nSQUID) is considered to have the capability of approaching the physical limit of irreversible computing. Superconducting coplanar waveguide (CPW) resonator of high quality factor Q is widely used for detecting extremely small signals. To measure the energy dissipation in nSQUID, we have designed and fabricated an nSQUID with its common mode flux control inductively coupled to a superconducting CPW resonator. The energy dissipation can be obtained from the changes in transmission spectra of the coupled circuit at different input powers. Low temperature experimental results at 1.07 K show that the bit operation energy in nSQUID operating at 2.19 GHz is about 1.38 zJ.

A micro compact coplanar power divider at X-band with finite-width ground plane based on GaAs MMIC technology

A micro coplanar Wilkinson power divider at X-band on GaAs substrate is presented in this paper. The proposed power divider introduces a size reduction method, and the length of the transmission line is reduced to λ/8 (at 10 GHz). Since the two segments of the two edge coupled quarter-wave asymmetric coplanar striplines (ACPSs) with finite-width ground plane are closed to each other, their characteristic parameters, such as characteristic impedance and attenuation coefficient, are obtained using the quasi-static conformal mapping technique (CMT) of coupled coplanar waveguide (CCPW) with finite-width ground plane. S-parameters for the power divider are deduced in the case of quasi-static TEM even–odd mode. The fabrication process is compatible with the GaAs MMIC process. The measured S-parameters are compared with the simulated results of HFSS v.11 and the calculated results of TEM even–odd analysis. Simulated results show that it has reflection loss less of 16.5 dB and insertion loss less of 3.6 dB. Measured results show that the divider has reflection loss less of 15.0 dB and insertion loss less of 3.5 dB. Compared with conventional Wilkinson power divider, the length of the power divider is shortened from 2,620 to 1,570 μm.

Trans-directional coupler with capacitor-shunted ground-defected coupled CPWs and inductor-loaded ACPWs for weak coupling applications

Trans-directional (TRD) couplers with capacitor-shunted ground-defected coupled coplanar waveguides (CPWs) and inductor-loaded asymmetric coplanar waveguides are proposed for weak coupling applications. To achieve weak coupling as well as perfect impedance match, unequal shunt capacitors and same series inductors are loaded on the coupled CPWs. In addition, a defected-ground structure is etched under the coupled CPWs for realizing high-impedance coupled lines with the printed circuit board technology. Two TRD couplers with coupling values of 10 and 20 dB are investigated theoretically and experimentally. The measured results show that the directivity of the proposed TRD coupler is better than that of conventional parallel-coupled microstrip-line coupler.

등각사상방법을 이용한 도체로 보강된 결합 도파 선로의 정전기장과 전위 분포 해석

본 논문에서는 등각사상 방법(conformal mapping method)을 사용하여 도체로 보강된 결합 도파 선로(conductor-backed coupled coplanar waveguide)의 정전기장 분포와 전위 분포를 계산하는 해석적인 수식을 유도하였다. 그리고 유도한 수식을 사용하여 결합 도파 선로 구조 전체에 분포하는 정전기장과 전위분포를 계산하고 이를 분석하였다. 논문에서 사용한 방법은 반복계산 과정을 필요로 하지 않으므로 이를 사용하면 전파해석방법(full-wave analysis method)보다 전기장분포를 빠르고 간편하게 계산할 수 있다. 이 방법은 결합기, 필터, 마이크로스트립 안테나와 같은 결합선로를 사용한 마이크로파집적회로의 분석에 폭 넓게 응용될 수 있다.

Accurate Synthesis of Four-Line Interdigitated Coupler

We present an accurate synthesis method for the design of a four-line interdigitated coupler in this paper. With the derivation of an admittance matrix of four coupled transmission lines and the use of an interconnecting condition, only half of the original coupled-line structure should be considered with its symmetric plane replaced by a perfect electric wall and/or perfect magnetic wall. Subsequently, two new mode admittances are, respectively, calculated from the propagation constants and the line impedances of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> - and pi-modes, which are extracted from full-wave simulation. In this way, a reference chart is generated that presents the relation between the two mode admittances and physical dimensions of the coupled lines. With any prescribed performance, the physical dimensions of a four-line interdigitated coupler can effectively be synthesized by looking up this reference chart. Two examples are given to demonstrate the accuracy and flexibility of our proposed scheme. One is a conventional 3-dB four-line Lange coupler fabricated by a miniature hybrid microwave integrated circuit process. The other is a composite microstrip coplanar waveguide coupler made by a standard printed circuit board process. For both couplers, simulated and measured results are in good agreement. The proposed method is useful for the accurate synthesis and design of four-line couplers having an interdigitated topology.

MULTILAYER PERCEPTRON NEURAL ANALYSIS OF EDGE COUPLED AND CONDUCTOR-BACKED EDGE COUPLED COPLANAR WAVEGUIDES

In recent years, Computer Aided Design (CAD) based on Artiflcial Neural Networks (ANNs) have been introduced for microwave modeling, simulation and optimization. In this paper, the characteristic parameters of edge coupled and conductor-backed edge coupled Coplanar Waveguides have been determined with the use of ANN model. Eight learning algorithms, Levenberg-Marquart (LM), Bayesian Regularization (BR), Quasi-Newton (QN), Scaled Conjugate Gradient (SCG), Conjugate Gradient of Fletcher-Powell (CGF), Resilient Propagation (RP), Conjugate Gradient back-propagation with Polak-Ribiere (CGP) and Gradient Descent (GD) are used to train the Multi-Layer Perceptron Neural Networks (MLPNNs). The results of neural models presented in this paper are compared with the results of Conformal Mapping Technique (CMT). The neural results are in very good agreement with the CMT results. When the performances of neural models are compared with each other, the best results are obtained from the neural networks trained by LM and BR algorithms.

32‐GHz dual‐termination coupled CPW bandpass filter on HR‐SI

AbstractBandpass filter is an important device in portable communication and other RF systems. A dual‐termination coupled coplanar waveguide (CPW) bandpass filter (BPF) has been designed by HFSS. This dual‐termination coupled structure improves the coupling capacitances between the central metal and the matching transmission lines so that the insertion loss can be reduced. The filter has been fabricated on a high resistivity silicon substrate (ρ ≥ 1000 Ω cm) with 1 μm SiO2. It has −2.16‐dB low insertion loss at peak transmission of about 32 GHz. This filter shows good s‐parameter characteristics and it is attractive for RF ICs. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1705–1706, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23464

Six-Port Reflectometer Based on Modified Hybrid Couplers

Six-port reflectometers have traditionally employed hybrid couplers as their building blocks, but the instruments reported thus far in the literature do not comply with the optimum design specifications. This paper describes a six-port reflectometer based on four-port coplanar-waveguide couplers that have been modified so as to meet such design requirements. Additional design parameters have been incorporated so that adjustments may be made to correct for residual hardware imperfections. Laboratory tests have confirmed an operating bandwidth of 90% (from 1.1 to 2.9 GHz) for the resulting reflectometer.

A Novel 3-dB Directional Coupler With Broad Bandwidth and Compact Size Using Composite Right/Left-Handed Coplanar Waveguides

A wideband composite right/left-handed (CRLH) coplanar waveguide (CPW) coupler with 3-dB coupling value and quadrature phase difference is presented. Compared with the conventional edge-coupled CPW coupler, this symmetrical structure, consisting of a gap capacitor, a broadside-coupled capacitor, and a meandering short-circuited stub inductor, achieves wider operating bandwidth and larger coupling level. The 3-dB CRLH CPW coupler with 0.7mm spacing between coupled lines exhibits an amplitude balance of 2dB and a phase balance of 900 plusmn 50 from 3.2 to 7.6GHz. The coupled-line length and the port impedance of the proposed structure are approximately lambda/4 and 50Omega, respectively, which makes it more compact than the cascaded CRLH microstrip coupled-line coupler. To characterize this structure, the equivalent circuit model including the unique coupling mechanism within CRLH CPWs is established and verified by measurement. The signal with less dispersion on output ports is demonstrated based on the standard deviation of group delay time

Experimental and Numerical Investigation of Crosstalk Effect in Coupled Coplanar Waveguides—Part I: Bi-Mode Coupled-Line Representation

The effect of square-wave propagation along coupled coplanar waveguides (C-CPWs) is presented in this paper. Developed numerical tools combining full-wave calculations of the frequency-dependent guided-mode parameters and the network theory formalism enable the determination of port voltages under specified linear termination conditions. Propagation constants and characteristic impedances of coupled lines have been determined for fundamental guided modes using the spectral domain technique combined with Galerkin's procedure. The scattering matrix of the four-port structure has further been used for the calculation of port voltages. Analysis has been performed by taking into account the bi-mode operation resulting from the assumption of the ideal electrical connection of distributed ground plane conductors. Simulation results have been compared with experimental data, and very good agreement has been found, proving the usefulness of the developed numerical tools

Experimental and Numerical Investigation of Crosstalk Effect in Coupled Coplanar Waveguides—Part II: Multimode Coupled Line Representation

An approach for the crosstalk effect description in coupled coplanar waveguides with ideally grounded central strip conductor (C-CPWGS) that, for the first time, takes into account nonideal grounding by means of multimode propagation is presented in this paper. The frequency-domain full-wave computations of modal eigenvectors and propagation delays combined with multiconductor transmission line equations have been employed to obtain near- and far-end crosstalk waveforms. Developed theory has been verified experimentally by comparison with results of the time-domain crosstalk measurement of selected test structures. A very good degree of coherence between numerically computed and experimentally measured data has been achieved

Analysis of coupled coplanar waveguide with ideal bonding wires between ground conductors

A novel approach that simplifies analysis of signal propagation along multiconductor coplanar lines, based on the example of the coupled coplanar waveguide with ideally grounded centre-strip conductor (C-CPWGS), is presented. The original spectral-domain approach (SDA) algorithm is modified to include additional boundary conditions induced by the presence of bonding wires. The results of the numerical simulations are experimentally verified and good agreement with the measurements is achieved. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 310–313, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21154

Analytical analysis of a rectangular shielded multilayer coupled coplanar waveguide

AbstractThe closed‐form expressions for calculating the quasi‐static parameters of a rectangular shielded multilayer coupled coplanar waveguide (RSMCCPW) are presented. Expressions of the odd‐ and even‐mode characteristic impedances, which can provide accurate and fast calculations, are derived by using conformal‐mapping techniques. The numerical results are obtained and compared with those available in the literature for similar unshielded structures. Good agreement between the results is observed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 392–395, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20149