Microstrip Line Circuit Research Articles

A microwave sensing system combination of interdigital structure (IDS)-based microstrip line and RF circuits for extracting complex permittivity of liquid samples

In this manuscript, a microwave sensing system for extracting complex permittivity of binary aqueous solutions based on a modified microstrip line with interdigital structure (IDS) etched is proposed. The passive resonance unit and active circuits constitute the microwave sensing system. The passive resonance unit is evolved from conventional microstrip line with the characteristic impedance of 50Ω, then the IDS is etched on the top surface of passive resonance unit to enhance the confinement of electrical field. The modified passive sensor can produce two resonant modes, i.e., odd-mode 1 and odd-mode 2, the electrical fields of these two modes are both concentrating at IDS, and odd-mode 1 with higher density of electrical field is adopted to retrieve complex permittivity of liquid samples. Except for the passive sensor, the sensing system consists of power divider, low noise amplifier (LNA), isolator, orthogonal hybrid coupler, phase shifter, mixer, and low-pass filter (LPF). The proposed microwave sensing system has two output DC voltages, i.e., channel-I and channel-Q. The mathematical relationship between complex permittivity and resonant frequency shift can be transformed into the relation between complex permittivity and two DC voltages by the proposed microwave sensing system, which is beneficial to discard the use of VNA. The two output voltages of microwave sensing system will be changed according to the injections of liquid samples with different complex permittivity, then the mathematical models can be established by summarizing the rule between complex permittivity and DC voltages. Finally, the established mathematical models can be adopted to predict the binary aqueous solutions with unknown complex permittivity. In measurement, the proposed microwave sensing system has the average sensitivities of about 2.478 mV/εr′ and 1.418 mV/εr′ for channel-I and channel-Q, respectively, which are several times higher than other reported ones. Low-cost, high sensitivity, convenient measurement, and easy fabrication are the merits for the proposed sensing system, and it is a good template in the region of detecting liquid samples.

Development and validation of a novel bias network design method for a class AB PA

AbstractIn this paper, the impact of the bias networks on a radio frequency (RF) power amplifier (PA) is analyzed and discussed comprehensively. Both the different sizes and positions of the bias microstrip line circuit have been studied for a broadband class AB PA. Both simulations and measurements show that the performance of the PA can be greatly improved with the adjustment of the bias circuit by effecting the harmonic impedance of the whole matching circuit. Compared with the existing works, the fabricated PA based on the proposed technique provides the best performance, thereby demonstrating the effectiveness of the developed bias circuit optimization method.

Numerical Short-Open-Load (SOL) Calibration Technique for Accurate Extraction of Electrically-Small Planar/Non-Planar Microstrip-Line Circuits

This article presents a numerical short-open-load (SOL) calibration technique for accurate extraction of electrically small planar/nonplanar microstrip-line (MSL) circuits and elements in the interface of 3-D full-wave algorithm or simulator. An additional matched-load condition is established at the reference plane and employed in the whole calibration process. In comparison with the traditional short-open calibration (SOC) method, the proposed SOL technique implemented in the interface of software does not inquire prior simulation of the internal current/voltage at the reference plane of two calibration standards but only needs to know the external port impedances of three calibration standards. After the description of entire extraction process, a few typical electrically small planar circuits, such as MSL open-end and step discontinuities, are first numerically deembedded, and their extracted circuit parameters are evidently confirmed with other published ones. Then, a nonplanar structure of a vertically placed shorting pin in the middle of MSL is studied with different sizes and positions to effectively extract the circuit parameters in the two presented equivalent models. Finally, a third-order Chebyshev filter is designed with pin-loaded MSL structures. Its frequency response is synthesized on the proposed SOL method to validate the correctness of the extracted circuit parameters and further demonstrate the usefulness of this method in synthesis design of electrically large microwave circuits. Good agreement among the filtering frequency responses from equivalent circuit model, full-wave simulation, and measurement has well revealed that the proposed SOL method is indeed accurate in numerical extraction of circuit elements and efficient in synthesis design of an entire circuit with prescribed specifications.

Design of a Novel Broadband Microstrip Line-Suspended Microstrip Line Transition Circuit

Based on the application requirements of the suspended microstrip circuit, a novel broadband microstrip line-suspended microstrip line transition circuit is designed in this paper. The transition structure uses “V-grooved” ground structure to realize the transition from microstrip line to suspended microstrip line in the direction of electric field, and uses gradient signal line for impedance matching to expand the bandwidth. The final simulation results show that the echo loss of the structure is better than 15 dB and the insertion loss is less than 0.165 dB in the frequency range of 0-40 GHz, and the sensitivity of circuit performance to circuit size is low. This design combines the ultra-low loss suspension line with the most commonly used microstrip line circuit, and has the advantages of broadband, low insertion loss, easy processing and compact structure. It improves the application scope of the suspension microstrip circuit and can be better integrated with other circuits or systems.

Far-End Crosstalk Noise Reduction Using Decoupling Capacitor

In this paper, a coupled miscrostrip line using the front-end decoupling capacitor is proposed to suppress the far-end crosstalk noise of the coupled microstrip line. The far-end crosstalk noise is greatly reduced from 63 to 25.7 mV. In order to further reduce the far-end crosstalk noise, a coupled microstrip line using the distributed decoupling capacitors is proposed. As compared with the coupled microstrip line using the front-end decoupling capacitor, the far-end crosstalk noise is further reduced from 25.7 mV to nearly 0 mV. In order to verify the simulation results, two coupled microstrip line circuits are fabricated and measured where the measurement results are in good agreement with the simulation results.

Triple‐band impedance transformers using equal‐length serial transmission lines

A new formulation of the fundamental load impedance circuit in the z -plane is employed to study transformers. The design employs prototypes of transfer function, parametric modelling techniques, and optimisation methods; a model describing multisection transmission-line transformers is proposed to match load impedance for use in wireless and mobile communication applications. Configuration of the transformer consists of multisection serial transmission lines. This transformer was designed on a PCB FR4 substrate featuring a permittivity of 4.4, a loss tangent of 0.0245, and a thickness of 1.6 mm. Microstrip line circuits were fabricated to verify the feasibility of the technique. The simulation and measurement results show that real and complex load impedances can be matched simultaneously at three different frequency bands. The characteristic impedance values of the transmission lines synthesising the transformers were adjusted according to the autoregressive process by using optimisation algorithms. The experimental results are in agreement with theoretical values.

Design of Compact Composite Microstrip Low Pass Filter Using MEMS Technology

This paper presents the design technique of a compact composite microstrip filter operating at ultra high frequency (UHF) band and its fabrication using micro-electro mechanical system MEMS technology. The fringing compensation method is applied into the design of the microstrip line transformation from lumped element. The filter lumped circuits and microstrip line circuit were designed and simulated using Advanced Design Software (ADS) and fabricated on silicon substrates to obtain the best filter characteristic based on S-parameter. The measured and simulated results have achieved a good agreement within the frequency of interest. This shows that the fringing compensation method of transforming lumped element into microstrip line is able to solve the conventional design of complexity size of circuit of composite low pass filter (LPF) into microstrip line. The proposed filter design can replace the conventional filters in wireless communication as they offer better performance at lower cost in the RF microwave communication applications.

An analysis of electromagnetic interference on RF circuits based on electromagnetic topology

ABSTRACTIn this article, we propose a method of analysis of the intentional electromagnetic interference (IEMI) in radio frequency circuits that are directly exposed to an external electromagnetic wave, using electromagnetic topology (EMT). EMT solves IEMI problems, by a fast and efficient transformation of the main penetrating channels of the external electromagnetic wave in the target, into general equivalent transmission lines. To handle nonlinear devices, we combined EMT with the harmonic balance method, by applying the least square method to the experimental data of the devices. To verify the proposed method, we applied it to microstrip line circuits with passive loads, a dipole antenna, and a low noise amplifier, and compared the results with the experimental ones. The two results were in good agreement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2784–2789, 2014

Measurement of the Permeability in a Ferrite Core by Superimposing Bias Current

AbstractIn this study, we investigate measurement of the magnetic permeability in a ferrite core at RF frequencies when bias current is superimposed on an RF signal with a view to adaptively controlling performance of RF transformers using ferrite cores. A measurement arrangement used comprises a short microstrip line (MSL) circuit including a coaxial conductor (CC) structure consisting of an electrically grounded metal pipe, a center conductor and a sample between them. A bias tee network is incorporated into this MSL-CC circuit in order to superimpose direct current on an RF signal. Using this arrangement, a dependence of permeability on an amplitude of superimposed bias current was measured at frequencies of 10 MHz to 500 MHz. Reliability of the measurement results is discussed based on several experimental data, implying that the method has an accuracy less than 10% at most of the above frequencies.

Microwave properties of microstrip line circuits used for Josephson voltage standard arraysat 70 GHz

The microwave properties of microstrip lines used for Josephson voltage standard circuitsat frequencies from 70 to 75 GHz were investigated at a temperature of 4.2 K. Ourmeasurements quantify the different loss sources. The excitation of a parasitic substratemode is postulated, demonstrated by microwave modelling and confirmed byexperiments. These modes dominate the losses for wafers with a thickness above500 µm. The substrate modes can induce an inhomogeneous microwave distribution in theJosephson junction array, thereby causing poor operation of the voltage standard circuits.Silicon dioxide fabricated in various PECVD processes was used as the dielectric layer inthe microstrip line circuits. Permittivity and losses of silicon dioxide and thesilicon substrate were determined, as well as the surface resistance of niobium.

Accuracy in Permeability Measurement by a Combined Microstrip Line-Coaxial Conductor Method

In this paper, accuracy or error in permeability measurement using a combined microstrip line-coaxial conductor method was investigated. The measurement circuit used in this study is composed of a microstrip line (MSL) circuit and a grounded metal pipe with a center conductor passing through it coaxially. A sample is placed between the metal pipe and the center conductor. We evaluated the measurement accuracy for this measurement arrangement with electromagnetic simulation for the case where there are gaps between the sample and the holder. As a result, it has been shown that the normalized errors for this method have similar gap size dependence to the conventional coaxial method, but are about 10 to 20 percent greater than the coaxial method. With a view to improving the measurement accuracy, a correction method for the error is also discussed.

Improvements in a Ferrite Core Permeability Dispersion Measurement Based on a Microstrip Line Method

In this work, errors in a ferrite core permeability dispersion measurement using a microstrip line (MSL) method, where three kinds of MSL circuits are used, are evaluated by both an electromagnetic simulation technique and experiments. The computer simulated results have shown that although the measurement errors decrease according to the diameter of the winding wire which passes through a sample ferrite core becomes larger, that is the spacing between the wire and the core gets narrower, a certain amount of error still remains. In order to overcome this problem and improve the measurement accuracy, a metal pipe electrically connected to a ground plane for shielding is placed around the wire of the non-magnetic core circuit which is one of the three MSL circuits noted above.

Left‐handed behavior in a microstrip line loaded with squared split‐ring resonators and an EBG pattern

AbstractCombining an electromagnetic band‐gap structure (EBG) and squared split‐ring resonators (SSRRs) in a planar microstrip line circuit, negative values of electric permittivity and magnetic permeability can be obtained. This phenomenon arises thanks to the negative permeability of the SSRR particles when they operate in the vicinity of their quasi‐static resonance frequency, and the negative permittivity due to the behavior of the EBG structure within the rejected frequency band. Therefore, a novel approach is presented in this article to synthesize a left‐handed media in microstrip technology. Full wave simulation results as well as measurement results from a fabricated prototype confirm the left‐handed behavior of the interaction. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2689–2692, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22841

Measurement Method for Ferrite Core Permeability Dispersion Using a Microstrip Line

This paper describes a method for measuring magnetic permeability dispersion of ferrite cores widely used in RF devices such as splitters in CATV systems. The present method has a step of measuring reflection coefficients for three kinds of microstrip line circuits, one having a test sample (ferrite core) mounted on it, one with a non-magnetic core instead of the ferrite, and one with an impedance matching resistor only. From the three reflection coefficients derived, the impedances of the coils with the ferrite and non-magnetic cores, respectively, are calculated and the complex permeability is determined by dividing the impedance of the ferrite core coil by the reactance component of the non-magnetic core coil. In this paper, the accuracy of the proposed method is discussed through a electromagnetic simulation and then the calculated results are compared with the experiments, indicating the validity of the method.

On the Quasi-Left-Handed Transmission Line with Gyrator Loading

This paper treats transmission characteristics of periodic structure of ferrite gyrator circuit with both theory and experiment, which is loaded into usual distributed constant line with and without lumped capacitor. Following three types of periodic structure of gyrator circuit are proposed: basic structure of periodic gyrator circuit, quasi-LH gyrator circuit with series capacitance loading, and quasi-LH gyrator circuit with parallel capacitance loading. Moreover, replacing the parallel capacitance with a resistance, a periodic structure of isolator circuit is proposed. Scattering parameters of gyrator circuit are derived with help of equivalent circuit model. Left handed transmission behavior of backward wave is discussed from dispersion curves. Experiments were undertaken using periodic structure of dielectric microstrip line and gyrator circuit fabricated on the ferrite substrate. Experimental results having wide band nonreciprocal characteristics are discussed with theory.

Numerical studies of stripline-typed photonic band-gap (PBG) structures using finite difference time domain (FDTD) method

One of the major topics in the areas of microelectronics and communications today is the study of photonic band-gap (PBG) structures using planar transmission lines. In fact, structures using microstrip-line circuits have been comprehensively applied in recent years. However, studies involving transmission lines using striplines (STP) have not been commonly conducted. In this paper, a number of PBG structures constructed on the STP are studied by using a well-known numerical method, the finite-difference time-domain (FDTD) method. Results show the band-stop filter behavior of these structures, and the computed results match generally well with the ones published in literature through solver validation. To improve the narrow bandwidth of regular PBG structures, a chirping and tapering technique is introduced. The proposed STP PBG structures may be considered as alternatives to the conventional microstrip-line typed PBG structures.

Low-loss terahertz ribbon waveguides

The submillimeter wave or terahertz (THz) band (1 mm-100 microm) is one of the last unexplored frontiers in the electromagnetic spectrum. A major stumbling block hampering instrument deployment in this frequency regime is the lack of a low-loss guiding structure equivalent to the optical fiber that is so prevalent at the visible wavelengths. The presence of strong inherent vibrational absorption bands in solids and the high skin-depth losses of conductors make the traditional microstripline circuits, conventional dielectric lines, or metallic waveguides, which are common at microwave frequencies, much too lossy to be used in the THz bands. Even the modern surface plasmon polariton waveguides are much too lossy for long-distance transmission in the THz bands. We describe a concept for overcoming this drawback and describe a new family of ultra-low-loss ribbon-based guide structures and matching components for propagating single-mode THz signals. For straight runs this ribbon-based waveguide can provide an attenuation constant that is more than 100 times less than that of a conventional dielectric or metallic waveguide. Problems dealing with efficient coupling of power into and out of the ribbon guide, achieving low-loss bends and branches, and forming THz circuit elements are discussed in detail. One notes that active circuit elements can be integrated directly onto the ribbon structure (when it is made with semiconductor material) and that the absence of metallic structures in the ribbon guide provides the possibility of high-power carrying capability. It thus appears that this ribbon-based dielectric waveguide and associated components can be used as fundamental building blocks for a new generation of ultra-high-speed electronic integrated circuits or THz interconnects.

Two Dimensional Electric Field Measurement in Microstrip-Line Circuits by Coaxial-Type Probe

A detailed investigation of the electromagnetic field distributions in high frequency printed circuits and high-speed interconnects is very useful for physical understanding, studies of electromagnetic coupling effects for EMC and EMI and for optimization of electromagnetic circuit designs. The aim of this paper is to show how to measure the electric field distributions in electromagnetic circuits. An electromagnetic analysis for microstrip-line circuits is carried out by using a finite-difference time domain technique and its measurement is carried out by using a small probe antenna. The measurement results are in fairly good agreement with those of the numerical analysis using the FDTD method. Thus, the measurement system offers a valid means for predictions in the theoretical analysis of more complicated discontinuity problems.

A Yee-based expanded node with dielectric boundary conditions for the TLM method

The Yee-based expanded node with dielectric boundary conditions is introduced here for the TLM method to simulate the electromagnetic characteristics of microwave circuits. This numerical structure is presented graphically, and at the same time, related to the conventional bases straightforwardly. In application, microstrip line circuits including the microstrip line and interdigital structure are analyzed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 398–403, 1999.

Analysis of a partially sealed package for microstrip-line circuits

A partially sealed package formed by two metal diaphragms with or without an absorber is proposed and analyzed for shielded microstrip-line circuits. The mode-matching method, method of lines, and finite-element method are mixed appropriately to investigate the package. For a specific analysis, an electric current filament and a microstrip-line gap are chosen to simulate, respectively, an active circuit element (CE) and a passive CE to be packaged. The suppression effect of the package on the spurious (higher order) modes and the influence on the dominant mode are fully studied by comparing the excitation and scattering characteristics of the CE's with and without the package.