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This paper proposes a frequency selective absorber with a notch reflection band. It consists of a lossy layer and a metal ground. The lossy layer is composed of the octagonal ring and meander‐line resonators connected in parallel on the same plane, which are used to obtain a wide absorption band and a notch reflection band, respectively. The simulation results show that there are two absorption bands from 2.22 to 6.8 GHz and 7.94 to 8.54 GHz, and there is a −3dB reflection band from 7.14 to 7.68 GHz. Moreover, the absorber also has the characteristics of compact structure, polarization‐independent, and angular stability. The equivalent circuit has been established and explained the performance of the proposed band‐notched absorber. The proposed band‐notched absorber is manufactured and measured, and the results are generally in good agreement with the full‐wave simulation results. [ABSTRACT FROM AUTHOR]

This study proposes an improved broadband equivalent circuit model for millimeter‐wave and illustrates that the real part of the Z‐parameter (like Z21, Z31, and Z41) cannot be neglected. This improved model contains multiple‐coupled inductors on silicon with effective substrate current loops. And it is fabricated and measured in four‐port and in two‐port on the basis of 0.18 μm and 40 nm CMOS technology, respectively. Moreover, this proposed model is applied to a 22–31 GHz three common‐source stages differential gm‐boost low‐noise amplifier for 5G communication in 65 nm CMOS process. According to the measurement, the minimum noise figure is 2.5 dB at 23 GHz and the maximum gain is 22.2 dB at 24.5 GHz. The chip size is 0.5 mm × 0.92 mm with all pads. [ABSTRACT FROM AUTHOR]

An efficient time domain hybrid method is proposed, which integrate transmission line (TL) equations, finite‐difference time‐domain (FDTD) method, Norton and Substitution theorems together, to predict the EM fields coupling with the penetrated wire connecting two electronic devices. Within this method, the geometry of penetrated wire is divided into external and internal TLs according to the shielded enclosures of two devices firstly. Then the equivalent circuit model of penetrated wire is established by the Norton and Substitution theorems, which can represent the discontinuity of impedance between external and internal TLs and the transmitting of interference signals between terminal loads of the wire. Finally, the TL equations combined with FDTD method is utilized to compute the transient responses on external and internal TLs respectively. Numerical simulations of penetrated wire connecting two shielded enclosures in different environment are employed to verify the accuracy and efficiency of the presented method. [ABSTRACT FROM AUTHOR]

A polarization‐independent reconfigurable frequency selective rasorber (FSR)/absorber with low‐insertion loss (IL) based on diodes is proposed in this article. The presented structure consists of a lossy layer based on square loops and a bandpass frequency‐selective surface. These two layers are separated by an air layer. Each layer has an embedded bias network that provides the bias voltage to the diodes through metallic via. This configuration can avoid undesirable effects associated with the additional biasing wire. When the diodes are in off‐state, the structure is in FSR mode and exhibits a transmission window at 4.28 GHz with only 0.69 dB IL within the absorption bands. While diodes are in on‐state and the structure switches to absorber mode, it achieves perfect absorption with absorptivity of over 90% ranging from 2.8 to 5.2 GHz. An equivalent circuit model is developed to analyze the physical mechanism of the structure. A prototype of the proposed architecture is fabricated and measured, where reasonable agreements between simulations and measurements are observed, verifying the effectiveness of this design. [ABSTRACT FROM AUTHOR]

In this study, an improved RF CMOS transistor compact equivalent circuit model is presented. Due to the finite resistivity of the substrate, the magnetic coupling effect between the interconnection line and the substrate affects the signal propagation at mm‐wave frequency range. To characterize transistors in the terahertz band, a sophisticated network is introduced to represent the magnetic field of interconnection lines and substrate image current. In addition, the parameters of the proposed model are extracted by an analytical method. By comparison with the reported model, the proposed model can significantly improve the phase accuracy. The comparison of calculation results and experimental data shows that the proposed model can well characterize the transistor up to 220 GHz. [ABSTRACT FROM AUTHOR]

In this article, a metamaterial absorber structure is analyzed using the transmission line method (TLM) considering the normal incidence of the wave. The unit cell of the presented absorber structure is a composite geometry providing dual‐band absorption. Peak absorptivities of 95.02% and 99.84% are obtained at 4.215 GHz and 10.95 GHz, respectively. The experimentally validated simulated reflection response is used as a reference to validate the analytical response of the absorber structure. To obtain the equivalent circuit model, the frequency selective surface (FSS) forming the absorber top layer is considered as a combination of two simpler FSS. The individual absorbers formed by two such FSS are correctly modeled using TLM. The obtained equivalent circuits are then combined suitably by incorporating the involved coupling capacitances into the calculation. The analytical and simulated response of the presented absorber structure is found in good agreement. The presented decomposition approach for the development of a circuit model of the composite FSS is promising and it would pave the way in obtaining the good physical insight of the multiband metamaterial absorber structures. [ABSTRACT FROM AUTHOR]

A high‐capacitive frequency selective surface (FSS) is proposed with the aim of achieving a small array periodicity composed of four folded arms spiral conductors with 90° rotation symmetry. The electromagnetic response of the proposed FSS can be analyzed by an equivalent circuit model where the circuit parameters (L, C) are dependent on the geometries of conductors. A high value of capacitance was predicted arising from the inter‐plane and intra‐plane couplings between the folded spiral conductors distributed over large effective segments with a small gap spacing. However, the value of the total equivalent inductance decreases due to the parallel circuit connection of the shunted inductance of each arm. Parametric analysis on the geometrical effect was also conducted to validate the applied equivalent circuit model. [ABSTRACT FROM AUTHOR]

Abstract: In this letter, an ultra‐thin triple‐band metamaterial absorber with high absorptivity in each band of operation is presented. The unit cell of the proposed structure consists of an outer circular metal ring and an inner Jerusalem cross on top of a thin dielectric substrate backed by metallic ground plate. Simulation responses exhibit that the proposed absorber is polarization insensitive and has a stable performance to the oblique incidence angles for both the TE and the TM polarizations. A simple equivalent circuit model and a multi‐reflection interference theory are also investigated to quantitatively explain the physical absorption mechanism. Finally, an experiment demonstration is conducted and the measurement response indicates the validity of the proposed design and the analysis methodologies. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the design of stacked suspended plate transmitter antenna for digital video and audio broadcasting. Contrary to conventional dipole structures, we have designed the antenna in VHF band (174–254 MHz) with two plates for wideband matching and design flexibility. Radiating primary plate has been excited by novel wideband modified inverted L‐type probe. Parasitic secondary plate, and vertical wall between primary plate, and ground plane have been used for further matching and beamwidth adjustment. A bandwidth of 42% and gain of 8.5 dBi is obtained at center frequency. Together with equivalent lumped element circuit model of designed antenna and experimental results for S11, gain, and radiation pattern are presented. To the best of authors knowledge this is the first stacked suspended plate antenna achieving a record bandwidth of 42% in VHF band. [ABSTRACT FROM AUTHOR]

A triband monopole patch antenna with high figure-of-merit (FoM) for WiMAX and WLAN applications has been proposed. It consists of a rectangular patch with two asymmetrical L-shaped slots, where L-slots generate two lower resonance frequencies and patch the higher. A parametric study to optimize the slot length is carried out to achieve the desired frequency bands. An equivalent circuit model of the antenna is developed and analyzed for loss due to input impedance mismatch at each resonance frequency. The simulated results of return loss of antenna and radiation patterns are validated with experimental results. [ABSTRACT FROM AUTHOR]

The microwave transmission properties of suspended, quasi-metallic individual single-walled carbon nanotubes (SWCNTs) with a bottom gate field-effect transistor (FET) configuration have been investigated up to 10 GHz by standard two-port S-parameter measurements under different gate bias voltages. A tapered coplanar waveguide (CPW) transmission-line test fixture is designed to overcome the parasitic and mismatch issues. An open-through de-embedding algorithm has been applied to extract the intrinsic properties of SWCNTs. And an equivalent circuit model has been proposed to fit the extracted measurement data as a function of the bottom gate bias voltage, facilitating the applications of CNTs into high-frequency nanocircuits. Moreover, the properties of our transistor device are found to change after a period of time. [ABSTRACT FROM AUTHOR]

ABSTRACT This letter presented a novel compact continuously tunable low-pass filter (LPF) using varactor-loaded coupled rhombic stubs. The proposed LPF demonstrated excellent roll-off selectivity, wide stopband range as well as good cut-off frequency tunability. This LPF consisted of three varactor-tuned coupled rhombic stubs loaded on a section of high-impedance microstrip line symmetrically and two coupled line LPFs which could further improve the stopband performance. A detailed explanation of the tuning mechanism was illustrated by adopting lumped-element equivalent circuit model. The measured results showed not only a wide cut-off frequency tuning range of 56% from 350 to 800 MHz, but also an excellent steepness factor of less than 1.14. Additionally, a rejection level of greater than 20 dB up to 8 GHz (>10 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents an equivalent circuit model for a stepped U-slot defected ground structure (DGS). For a stepped U-slot DGS, the defected structure is simply modeled using a short-circuited stepped impedance coplanar waveguide (CPW) combined with a gap capacitor. The proposed circuit model is advantageous in its ability to accurately control the ratio ( η = fs1 /fr) of the fundamental resonance frequency ( fr) to first spurious resonance frequency ( fs1) by changing the impedance and the electrical length of the CPW in each step. By using this property, two types of resonators with normalized first spurious resonance frequencies ( η = fs1 /fr) of 4 and 2 were designed and fabricated. Good agreement between the EM simulations and the experimental results were achieved. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:583-587, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a modified equivalent circuit model for analysis of terahertz (THz) photoconductive antennas has been introduced to investigate the effect of temperature on the performance of this device. Based on this modified equivalent circuit model, the effect of temperature on various parameters of a THz photoconductive antenna such as excited THz photocurrent, radiated electromagnetic field and optical-to-THz power conversion efficiency has been studied. The model predicts that an increase in the operational temperature of photoconductive antennas results in lower induced THz photocurrent, lower radiated electromagnetic field and also lower optical-to-THz power conversion efficiency which is in accordance with experimental results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2475-2479, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a reconfigurable monolithic step-up autotransformer. In addition, its reconfigurable operation has been analyzed using a proposed nonideal transformer model. A corresponding complete model for a reconfigurable autotransformer has also been developed on a silicon substrate case. The proposed reconfigurable autotransformer was fabricated using a standard 65-nm CMOS process. The measurement results demonstrate that the fitted curves using the proposed complete model agree well with the measured results. The proposed reconfigurable autotransformer can perform the required impedance changes depending on the power amplifier output power change with low insertion loss. The 50-Ω load impedance is transformed to a low value of 3.28 Ω in high power (HP) mode operation, and it is transformed to a high value of 12.26 Ω in low power (LP) mode operation at 0.9 GHz. The transformer insertion losses in HP and LP mode operations are −1.424 dB and −0.706 dB at 0.9 GHz, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1662-1666, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents an equivalent circuit model for a dumbbell-shaped defected ground structure (DGS) in a microstrip line. The effects of equivalent circuit elements of a dumbbell-shaped DGS and their magnetic coupling to the host transmission line are modeled as a simple lumped-element circuit. By adding a virtual capacitor on the narrow etched gap, the values of inductance and capacitance of the dumbbell-shaped DGS in the ground plane were extracted. Also, other main circuit parameters of the proposed circuit model were extracted using EM simulation result. This article provides one approach for understanding the operating principle of the DGS structures. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2910-2913, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT This article proposes a printed loop tag antenna placed near a human body for use on student radio frequency identification cards. The proposed tag antenna printed on a polyvinylchloride card is a one-wavelength loop fed by a T-matching transformer. An equivalent lumped-circuit for the T-matching transformer is presented to synthesize the T-matching feeding structure. A four-layer stratified elliptical cylinder with physical parameters is utilized as a human model for EM simulations. The simulated bandwidth of the T-matching loop tag antenna is 91 MHz (866-957 MHz, 10%). The T-matching structure allows the loop antenna to have wideband characteristics. Experiments revealed that the reading distance ranges from about 3.3 to −6 m when the tag was placed in different positions on the human chest in the open space environment. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1194-1200, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a dual band-notched ultrawideband (UWB) antenna is investigated by the equivalent circuit model and time domain characteristics. Transmission line model and L-C resonant circuit model of the antenna are presented. Transfer function and pulse waveforms are also studied to evaluate the proposed antenna. Experimental results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with voltage-standing wave ratio <2, while avoiding the interference from WiMAX and 5-GHz wireless local area network. Radiation patterns and antenna gain study show that the stable radiation characteristics at different frequencies are obtained. The proposed antenna has a compact size, good radiation characteristics, and UWB behaviors to satisfy the requirement of the current UWB wireless communications systems. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2993-3000, 2013 [ABSTRACT FROM AUTHOR]

ABSTRACT An equivalent circuit model is proposed to estimate the absorbance characteristics of the proposed terahertz wave absorber based on metamaterial. The component can be optimized to achieve high absorption of different frequency of the incident electromagnetic wave by adjusting physical dimensions and material parameters. The fabricated device was characterized by using a Fourier transform infrared spectrometer. The designed absorber demonstrated excellent absorbance compared with previously reported metamaterial-based terahertz wave absorbers, which exhibited 99.3% absorbance at 0.575 THz. The simulation and measurement results show that the absorber is an excellent terahertz wave collector. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2195-2198, 2013 [ABSTRACT FROM AUTHOR]

ABSTRACT We present a compact printed ultra-wideband (UWB) antenna with a band-notched characteristic. A modified ground plane is introduced to achieve a wide impedance bandwidth from 3 to 13.4 GHz with S11<- 10dB. By inserting an arc-shaped slot in the radiating patch, the notch frequency band at 3.4-3.7 GHz is obtained. An equivalent circuit model and parametric studies are given to explain the principle of the proposed UWB antenna. The relationship between the current distributions and radiation patterns is discussed. Simulated and measured results show that the proposed antenna has good impedance matching, stable radiation patterns and constant gain. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2236-2240, 2013 [ABSTRACT FROM AUTHOR]

In this article, the equivalent circuit model of an electro-absorption modulator (EAM) with planar isolated pedestal GSG contact is built to investigate the high-speed performances. A novel broadband impedance matching method for the microwave packaging of the EAM is presented. With this matching network, RF return loss can be great suppressed in a wide frequency range up to 40 GHz, along with an extended 3-dB bandwidth to 38.8 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2026-2032, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27040 [ABSTRACT FROM AUTHOR]

A novel composite right/left-handed transmission line is presented which is synthesized by etching Koch fractal shape slot in the ground plane and series capacitive gap in the conductor strip. Unlike the structures loaded with complementary split ring resonators, the proposed structure can operate at very wideband and is used to design an ultra-wideband (UWB) filter. The UWB filter is fabricated and tested. The relative bandwidth of the -10 dB return loss is 128% and the insertion loss is larger than -1.5 dB except at high frequencies. The equivalent circuit model of the proposed structure is presented and the electrical parameters are also extracted. The circuit model results are compared with the simulation and measurement results which verify that not only the extracted parameters are exact but also the equivalent circuit model is reasonable. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2160–2163, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24553 [ABSTRACT FROM AUTHOR]

A novel interconnect model is used in the postlayout simulation of a broadband transimpedance amplifier. Simulation results employing the proposed model are verified by on-wafer measurement results. The impact of interconnect effects on the circuit performance is analyzed. The importance of incorporating an adequate interconnect model is demonstrated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3017–3020, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23878 [ABSTRACT FROM AUTHOR]

The segmented analysis method of a finite planar ridged tapered slot antenna (RTSA) array is presented to develop a wideband phased array with a triangular lattice. The RTSA array is segmented into two-parts with a feeder and the arrays of tapered slot antenna (TSA) and these scattering parameters are analyzed respectively. This proposed method gives the merit of a great reduction of computational cost. To verify the advantage of this method, we build the numerical model of only one feeder and dual polarized arrays of TSA with 10 × 12 elements. The measured results of the fabricated array meet the design goals of 3:1 bandwidth, scan volume of ±45°, active VSWR (AVSWR) below 3:1. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1140–1143, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23314 [ABSTRACT FROM AUTHOR]

In this letter, a novel broadband dipole antenna for UHF RFID transponder, which offers global functionality across different regulatory areas is proposed. The proposed antenna has a measured bandwidth from 0.83 to 1 GHz (18.5%) where the power reflection coefficient is below -10 dB for conjugate matching with an EPC class 1 Gen 2 chip, which is sufficient to cover the whole band (0.86–0.96 GHz) regulated by EPC global class 1 Gen 2 protocol (ISO/IEC 18000 6c). Additionally, an equivalent circuit model for such kind of antenna is presented to illustrate the broadband impedance matching characteristic between the antenna and the chip. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2795–2798, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22877 [ABSTRACT FROM AUTHOR]

Design of a simple coplanar waveguide (CPW)-fed patch antenna for radio frequency identification (RFID) application is presented. The radiation mechanism of such an antenna has been investigated, based on a moment-method numerical analysis and experimental measurement. The antenna with a symmetrical folded slot to become a U-shaped monopole can excite 5.8 GHz resonance mode with impedance bandwidth of 490 MHz, average antenna gain of ≥4.1 dBi, and monopole-like radiation patterns but has a compact antenna size. These properties make the antenna suitable for use in RFID tags. In addition, an equivalent circuit model for such kind of antenna is also presented to account for its radiation characteristics. Good agreement between the simulated and modelled results has been obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 71–74, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22051 [ABSTRACT FROM AUTHOR]

A large-signal equivalent-circuit model of quantum-well lasers is developed in this paper. This model is based on three-level rate equations, including carrier transport effects and the role of the gateway state at the quantum well. The experiential formula of the optical peak gain variation with carrier density is given. Turn-on delay and modulation frequency response of QW lasers are obtained using a SPICE simulator. The simulation results of the frequency response show excellent agreement with experimentally obtained data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 295–298, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11195 [ABSTRACT FROM AUTHOR]

A multi-pole gap-coupled unidirectional dielectric radiator (UDR) is proposed for broadband applications in the millimeter-wave band. The advantages of gap-coupled UDR include ease of planar integration, low loss, and low cost. Design parameters of the gap-coupled UDR, such as resonator length and gap distance, are determined using an equivalent circuit model of an evanescent nonradiative dielectric (NRD) guide. Prototypes of the gap-coupled UDR are designed and measured at 38 GHz. The measured results show good agreement with simulated data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 498–501, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11102 [ABSTRACT FROM AUTHOR]

The existing equivalent circuit model of space-harmonic coupled-cavity slow-wave structures was extended to model structures with double slots and tapered or step-tapered ferrules. This model was validated by comparing its results for dispersion and total impedance characteristics of typical slow-wave structures operating in S-band, with those obtained by computer simulation using the 3D Maxwell equation solver MAFIA.* This model was also validated with the experimental results of a particular double-slot structure at S-band. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 322–326, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10596 [ABSTRACT FROM AUTHOR]

An equivalent circuit approach to modeling of the electro-optic sampling structure is proposed for the first time. The influence of the optical probe to S parameters of the coplanar waveguide test structure is modeled by an equivalent circuit consisting of the analytic approximations and lumped circuit elements. The model coefficients are optimized by fitting the full-wave field simulation results. The model is dependent on the test structure geometry and material parameters. [ABSTRACT FROM AUTHOR]

The microwave impedance of a current-rectifying Al, Ga[sub 1-i] As ramp heterostructure is measured from 0.1 to 12 Ghz over a temperature range of 20 to 300 K. The elements of a small-signal equivalent circuit model are optimized to fit the experimental impedance data over the full temperature and de bias ranges. These circuit elements are identified with the physical structures and carrier transport mechanisms in the device. [ABSTRACT FROM AUTHOR]

ABSTRACT For a microstrip line with an asymmetric spiral-shaped defected ground structure (DGS), an equivalent circuit model is presented. From the lumped-element circuit model describing the asymmetric properties in circuit elements as well as in their magnetic coupling to the host line, the two rejection frequencies are derived. The equivalent circuit model provides physical insight into the dual-frequency operation of the asymmetric spiral-shaped DGS. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1222-1224, 2014 [ABSTRACT FROM AUTHOR]

Characterization of on-wafer vias using a 0.18-μm RF CMOS technology is presented. Equivalent resistance and inductance of a single via and multiple vias with different physical arrangements are extracted from full wave simulations up to 30 GHz. An equivalent circuit model with frequency-independent components is proposed to model the frequency-dependent characteristics of the vias. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 713–715, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23173 [ABSTRACT FROM AUTHOR]

An improved equivalent lumped-element circuit model for predicting the transmission characteristics of spiral inductors is presented in this Letter. The improved model can simulate the forward transmission coefficient more accurately than the traditional model. By adding a shunt RC arm, the effects of the substrate, which become dominant at high frequencies, are well taken into account. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 35–37, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10365 [ABSTRACT FROM AUTHOR]