Line Characteristic Impedance Research Articles

Transmission lines characteristic impedance versus Q-factor in CMOS technology

AbstractThis paper presents a systematic comparison of the relationship between transmission line characteristic impedance and Q-factor of CPW, slow-wave CPW, microstrip, and slow-wave microstrip in the same CMOS back-end-of-line process. It is found that the characteristic impedance for optimal Q-factor depends on the ground-to-ground spacing of the slow-wave transmission line. Although the media are shown to be similar from a mode of propagation point of view, the 60-GHz optimal Q-factor for slow-wave transmission lines is achieved when the characteristic impedance is ≈23 Ω for slow-wave CPWs and ≈43 Ω for slow-wave microstrip lines, with Q-factor increasing for wider ground plane gaps. Moreover, it is shown that slow-wave CPW is found to have a 12% higher optimal Q-factor than slow-wave microstrip for a similar chip area. The data presented here may be used in selecting Z0 values for S-MS and S-CPW passives in CMOS that maximize transmission line Q-factors.

Performance of ultra‐wide band DCBLNA with suspended strip line radiator for human breast cancer diagnosis medical imaging application

This study presents the performance of differential cascode balun low noise amplifier (DCBLNA) with ultra-wideband (UWB) for human breast cancer diagnosis. The proposed DCBLNA design-I with bulky spiral inductors achieves insufficient bandwidth with large power consumption of 10.8 mW. To attain the proper UWB band of operation, suspended strip line (SSLIN) radiators have employed in the proposed design-I. The performance of SSLIN is evaluated in terms of line capacitance and characteristic impedance by optimising its width. It is observed that best 50 Ωn-II. DCBLNA design-II using SSLIN have achieving a desired band of operation ranging from 1.5 to 15.7 GHz and best NF of 0.5 dB. The gain and phase imperfections are simulated to characterise balun networks. The smallest gain imperfection achieved is 0.1 dB at 10 GHz while the simulated phase imperfection turns out to be sufficiently good with 2.35° at 8 GHz. The proposed DCBLNA design-II is implemented and fabricated using RFCMOS 45 nm Taiwan Semiconductor Manufacturing Company (TSMC) process under commercial conditions. The highest figure of merit comes out to be 3.2 that ensures good accuracy of medical imaging for breast cancer diagnosis.

Modeling and Analysis of Terahertz Graphene Switches for On-Wafer Coplanar Transmission Lines

We present an analysis of graphene-loaded transmission line switches for sub-millimeter wave and terahertz applications. As such, we propose equivalent circuit models for graphene-loaded coplanar waveguides and striplines and examine the switching performance under certain parameters. Specifically, we identify the optimum design of graphene switches based on transmission line characteristic impedance, scaling factor, graphene shape, and topology (series or shunt). These parameters are varied to obtain the insertion loss and ON/OFF ratio of each switch configuration. The extracted results act as the design roadmap toward an optimum switch topology and emphasize the limitations with respect to fabrication challenges, parasitic effects, and radiation losses that are especially pronounced in the millimeter wave/terahertz bands. This is the first time that such an in-depth analysis is carried out on graphene-loaded transmission line switches, enabling the development of efficient millimeter wave/terahertz tunable topologies in terms of insertion loss and ON/OFF ratio. Specifically, the optimized switches can be integrated with antennas or employed for the development of tunable phase shifters, leading to the implementation of efficient reconfigurable reflective surfaces (e.g., reflectarrays) or coded phased arrays either for imaging or wireless communication applications. In our models, we use measured graphene values (sheet impedance) instead of theoretical equations, to obtain the actual switching performance. Moreover, the proposed study can be easily expanded to other thin film materials that can be characterized by a sheet impedance including vanadium dioxide and molybdenum disulfide. Finally, the proposed equivalent models are crucial for this in-depth study; since we simulated more than 2,000,000 configurations, a computationally challenging task with the use of full-wave solvers.

Transmission Line Impedance Characterization Using an Uncalibrated Vector Network Analyzer

For determining the line characteristic impedance ${Z}_{1}$ of uniform transmission lines, it is typically necessary to use a calibrated vector network analyzer (VNA), whose calibration reference impedance ${Z}_{2}$ is known. Using the eight-error term model for modeling a VNA and based on the fact that the values of the error terms are unique and independent of the calibration structures used to determine them, a new method for determining the line characteristic impedance of uniform transmission lines is presented. The main feature of the new method is that it only uses $S$ -parameter measurements of a thru-line and a thru-load combination measured with an uncalibrated VNA.

Compact reconfigurable bandpass filter with wide frequency tuning range

ABSTRACTA compact reconfigurable bandpass filter with wide tuning range is proposed in this letter. The reconfigurable function is realized by utilizing two varactor diodes at the end of the bandpass filter. Instead of using the coupling gap to create the desired coupling coefficients, a high characteristic impedance line is applied. A compact reconfigurable filter is designed, fabricated and measured. The measured tuning frequency ranges from 0.38 GHz to 0.96 GHz, which is about 86.6% of the central frequency. The measured insertion loss of the proposed reconfigurable filter is less than 2.5 dB, while the measured return loss is greater than 11 dB.

Parallel ring‐line rat‐race circuit with very loose coupling

AbstractThis article describes rat‐race circuits (RRCs) in which a pair of ring‐lines have parallel lines of ±180‐degree difference for electrical length to realize the RRC with very loose coupling such as −10 dB or less. The proposed RRCs with parallel ring‐lines realize a coupling factor of −10 dB and −20 dB by using moderate characteristic impedance lines with a view point of fabrication tolerance for general PCB technologies. We confirm the validity of this circuit construction and design method using a commercial electromagnetic simulator and decide the circuit pattern for fabrication at a center frequency of 2.45 GHz. The fabricated RRCs with parallel ring‐lines realize the desired coupling factors and in‐/out‐of‐phase outputs, and the measurement results of scattering parameters for −10 dB and −20 dB RRCs are in good agreement with the simulation results.

Thru-Reflect-Line Calibration Technique: Error Analysis for Characteristic Impedance Variations in the Line Standards

In this paper, we analyze the impact of characteristic impedance variations among standards on the accuracy of the thru-reflect-line (TRL) calibration technique. The impedance transformer method is adopted to derive the expressions of the calibration coefficient errors due to the manufacturing tolerances. It is found that three factors can affect the magnitude of the errors in the calibration coefficients (c/a and b terms), which are crucial to get the final calibrated results. The first factor is related to the original parameters of the error networks (test fixtures): the larger the insertion losses, the smaller the error in b ; the error in c/a may see an opposite trend if the error network is lossy instead of lossless. The second factor is denoted as the phase contribution (one of the three multipliers of the derived error expression): the magnitude of this error contributing item is approximately equal to the ratio of two hyperbolic sine functions, the variables of which are the length of Line and the length difference between Line and Thru, respectively. The third factor comes from the impedance differences between Thru and Line: the smaller the impedance variation, the smaller the error. The error analysis, presented here, can help engineers evaluate the calibration accuracy by analyzing the error contributing items. It also can be further used to guide test fixture designs to maximize TRL's error immunity to the transmission line characteristic impedance variations.

A Novel Wideband Balanced-to-Unbalanced Power Divider Using Symmetrical Transmission Lines

A novel wideband balanced-to-unbalanced power divider using symmetrical transmission lines is proposed. Due to the symmetry of the power divider circuit, even/odd-mode analysis method is applied to derive the even/odd-mode values and transmission line characteristic impedance. A resistor in the middle of two single-ended output ports is used to realize high isolation for the power division ports. One prototype of the wideband balanced-to-unbalanced power divider operating at 2.2 GHz (1.24–3.20 GHz) is designed and measured to prove the proposed methods.

Seven-Port Unequal Power Divider with Broadband and Large Division Ratio Characteristics Based on T-shape Stub

AbstractA broadband seven-port unequal power divider with large division ratio is designed based on the technique of T-shape stub. A T-shape stub is introduced to replace the conventional design for high characteristic impedance line in realization due to very small line width. The theoretical basis of the proposed T-shape stub is analyzed in detail using the Method of Matrix Algebra Analysis. The proposed design is simulated, fabricated and measured. The measured results are in good agreement with the simulated ones, and a large division ratio of 1:6 is achieved. The operation bandwidth of the proposed design is about 12 % (from 4.8 to 5.4 GHz).

Detectability of Degraded Joint Discontinuities in HV Power Lines Through TDR-Like Remote Monitoring

The aim of this paper is to clarify some important aspects associated with the possibility to detect degraded compression and bolted joints in power transmission lines using a time-domain reflectometry (TDR)-based remote monitoring. The optimization of a TDR-based remote monitoring method is discussed, studying the effects of the source impedance, source-to-line connection, line characteristic impedance, and scope settings, providing useful guidelines for a future method and instrumentation refinement. The experimental results are presented consisting in the inclusion of lumped resistors of several values along a 130-kV power transmission line. The minimum detectable resistance is discussed based on the present available hardware. The TDR-based method is shown to be able to also identify the main features of the line layout such as phase transpositions and different heights of adjacent towers. This paper represents a preliminary base to keep developing the proposed method, with the aim to overcome the actual limitations (costs, reliability, etc.) in power line monitoring.

A 10:1 unequal gysel power divider/combiner

ABSTRACTThis article introduces a modified Gysel power divider, providing high power division ratios, alongside the advantage of high power handling. To overcome fabrication limitations of high characteristic impedance line, caused by the anticipated high power division ratio, a coupled line structure with two shorts is used. This proposed structure makes closed‐form equations available for design and leads to a simple microstrip fabrication. A 10:1 unequal Gysel power divider is presented and fabricated as a design example and a satisfactory agreement between measurements and simulation results is verified. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2689–2692, 2016

Design and synthesis of flexible switching 1 × 2 antenna array on Kapton substrate

Flexible front- and back-end RF/analogue system antennas were recently emerged. However, little flexible antenna system design is available so far, in planar hybrid technology with surface mounted components. This paper describes the design feasibility of flexible switching 1 × 2 antenna array system. It acts as a switching antenna implemented in hexapole configuration. The system is comprised of a key element RF switch terminated by two identical patch antennas associated to half-wave elementary transmission lines (TLs). A detailed theory illustrating the global S-parameter model determination in function of the given RF-switch return and insertion losses is established. In difference to the conventional microwave circuit theory, the proposed equivalent S-parameter model is originally built with the non-standard optimized antenna load. Thus, the synthesis method of the terminal antenna input impedance and the output access line characteristic impedance is formulated in function of the specified return and optimal transmission losses. The design method and theoretical approach feasibility is verified with the demonstrator of flexible switching 1 × 2 antenna array printed on Kapton substrate. The circuit prototype is implemented in hybrid planar technology integrating patch antenna operating at about 6 GHz and a packaged GaAs RF switch associated to the RF/DC signal decoupling accessory mounted surface components. Simulations of the designed circuit transmission and isolation losses from 5.5 GHz to 7 GHz were carried out by using the commercial RF switch S-parameter touchstone model provided by the manufacturer. The simulated and measured return losses are compared and discussed. Then, the measured radiation patterns confirm the proposed switched antenna concept feasibility.

Novel Unequal Dividing Power Divider With 50 Characteristic Impedance Lines

In this letter a novel power divider (PD) structure with uniformed characteristic impedance lines and a fixed isolation resistor equal to source and load impedances has been proposed. Unlike traditional power dividers, the electrical lengths of the uniformed 50 $\Omega$ branches are the only parameters that need to be adjusted to achieve any required power division ratios, which makes it a flexible and adaptable layout for most desires. Arbitrary power division ratio, especially large dividing ratio that is difficult to achieve by conventional Wilkinson PD, can be obtained easily by applying the proposed structure. For verification, the measured results of a 2 : 1, a 4 : 1 and a 9 : 1 PDs operating at 3 GHz are shown in this letter.

Study of the Impact of H+ Mobile Ions on RF Performances of PECVD TEOS Silicon Dioxide Deposited at Low Temperature

In this paper, we study the impact of H+ mobile ions on Radio Frequency (RF) performances of silicon dioxide deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at low temperature (200°C), using a tetraethylorthosilicate (TEOS) - oxygen mixture as gas precursor. The presence of H+ ions within the dielectric is related to the low temperature deposition of the dielectric combined with exposition to moisture; the phenomenon is proven with Fourier Transform Infrared Spectroscopy (FTIR) and electrical methods as Transient Voltage Sweep (TVS) and C-V (capacitance-voltage) experiments on MOS (Metal Oxide Semiconductor) capacitors. A CoPlanar Waveguide (CPW) structure is employed to evaluate the RF behavior of the dielectric. It will be shown that the variation of CPW characteristics such as line loss (α) and characteristic impedance (Zc) is due to the interaction between the H+ ions and the substrate.

Measurement of Telephone Line Parameters using the Three Voltmeter Method

Egypt Company (TE) is the unique fixed telephone line company in Egypt. Due to the huge demand for high data rates for personals and companies, the performance of the copper network needs to be evaluated to assess its capability for transmitting high data rates to meet the increased demand on data transmission. The most commonly used testing and measuring instrument in TE is Dynatel 965DSP, which has some drawbacks. This paper introduces a new methodology for measuring the telephone line parameters. This method is based on the three voltmeter method for measuring resistors, capacitor, inductors and vector impedances. This method is automated by using NI-6008 USB data acquisition DAQ card. The frequency range of interest extends from 0.8 KHz to 196 KHz. The experimental results of the transmission line parameters, R, C, characteristic impedance, phase constant and attenuation constant have acceptable accuracy, while the results of the inductance and conductance have errors greater than the acceptable values.

Maximum Crosstalk Estimation in Lossless and Homogeneous Transmission Lines

In earlier papers, analytical formulas were derived to estimate the maximum crosstalk in the frequency domain for systems with electrically long signal lines. These formulas were developed to give designers intuitive feedback as to the causes for crosstalk problems and methods for maximum crosstalk reduction. In one of these papers, the maximum crosstalk estimates are based on intuitive relationships for infinitely long transmission lines. While the resulting model is quite simple and easy to understand, its limitations are poorly understood. In another paper, the maximum crosstalk estimates are based on a mathematically rigorous integral formulation, but the resulting model is relatively complex. This rigorous model is derived assuming the signal lines are weakly coupled and the transmission line characteristic impedances are approximately the same over the entire lengths of the aggressor and victim circuits. The following paper illustrates how the less rigorously developed estimates, based on infinitely long transmission lines, may be derived from the mathematically rigorous maximum crosstalk estimates for lossless and homogeneous transmission lines in the frequency domain. The resulting derivation provides insight into the limitations and mathematical validity of the less rigorous estimates that are not available in the original paper. The mathematically rigorous maximum crosstalk estimates are shown to have fewer and less restrictive assumptions than the estimates based on infinitely long transmission lines. Measurements and simulations are presented that validate results and illustrate maximum crosstalk estimate limitations.

An active resonance damper which avoids the estimation of the line characteristic impedance

The authors propose an active power filter as a means to damp the harmonic resonance along the power distribution line. The main advantage of the proposed damper is that of avoiding the estimation of the characteristic impedance of the distribution line. The effectiveness and the robustness of the proposed damper are verified by computer simulation with Simplorer. A comparison with a well-designed damper proposed by others is also provided.

A Comparison between Electric and Magnetic Parallel Plane Strip Transmission Lines in the Framework of a Quasi-TEM Analysis

This paper presents a performance evaluation of the parallel-plane magnetic strip transmission line in the framework of the frequency-domain quasi-TEM approach considering the case of wide strips. The transmission properties of the magnetic transmission line (attenuation, phase velocity, group velocity, dispersion, and characteristic wave impedance) are evaluated and compared with those describing the dual configuration of familiar parallel-plane electric strip transmission lines. Results obtained show that, for very high frequencies, the magnetic line can perform better than the corresponding electric line. This suggests that the parallel plane magnetic strip line can be useful for microwave and terahertz applications, provided that new-generation high-permeability high-frequency magnetic materials can be produced

A WIDEBAND QUADRATURE POWER DIVIDER/COMBINER AND ITS APPLICATION TO AN IMPROVED BALANCED AMPLIFIER

In this paper, a novel broadband quadrature power divider and its robust design method are presented. The QPD consists of a two-section power divider in combination with a 90-degree difierential phase shifter. The two-section power divider is calculated to provide equal power split, high output port isolation, and good return loss at all three ports. The difierential phase shifter consists of a composed right/left handed transmission line and pure-right handed transmission line named CRLHu-TL and PRHd-TL, respectively. The CRLHu-TL is divided into two parts; one of them consists of a pure-left handed section whose parasitic pad efiects are represented by means of a pure right handed section named PRHp. On the other hand, the PRHd- TL is composed by a microstrip transmission line of characteristic impedance 50› and electrical length 50 - and two sections equivalents to PRHp. The proposed circuit is applied to develop a broadband balanced amplifler with measured fractional bandwidth (FBW) of 124.4% at the center frequency of 2GHz.

Optimized Load Modulation Network for Doherty Power Amplifier Performance Enhancement

In this paper, a new load modulation network (LMN) is proposed for the Doherty power amplifier (DPA). By adjusting the transmission line characteristic impedances in the LMN, efficiency degradation due to the incomplete load modulation caused by the current unbalance between sub-amplifiers can be alleviated. Comprehensive theoretical analysis is conducted to investigate the impact of imperfect current profile on the overall efficiency and give rise to the judicious solution. To validate the new theory, two DPA prototypes based on GaAs pseudomorphic HEMTs are implemented for comparative purposes. Measurement results show that 8% and 13% greater power-added efficiency values are achieved at saturation and 6-dB output back-off point with the proposed method when compared with that of the conventional one. Additionally, the output 1-dB compression point is also improved by 2.9 dB. In particular, to the best of the authors' knowledge, this work provides a solution to address the inherent lower current driving ability for the peaking amplifier directly at the output part of a single-input DPA.