Search

Multiwalled carbon nanotubes (MWNTs) are characterized at X-, Ku-, Ka-, and Q-bands by rectangular wave- guide measurements. The scattering parameters (S-parameters) of thin MWNT papers containing a large ensemble of randomly oriented nanotubes are measured by a vector network analyzer from 8 to 50 GHz. A rigorous extraction algorithm has been developed to compute the effective complex permittivity (ϵ = ϵ′ - jϵ″) and permeability (μ = μ′ - jμ″) of the nanotube papers from the measured S-parameters. The extracted effective medium parameters are verified by finite-element simulations using Ansoft's High Frequency Structure Simulator (HFSS). The uncertainties for this characterization method are analyzed. The systematic uncertainties are found larger at lower frequencies than at higher frequencies. The extracted conductivity of the nanotube papers is in the range of 810-1500 S/m and the dielectric constant is from 250 to 700. The extracted complex permittivity can be fitted with the Drude-Lorentz model for the 8-50-GHz frequency range. The effective medium theory is then applied to remove the impact of air in the nanotube paper. [ABSTRACT FROM AUTHOR]

Presents a paper which focuses on the use of the finite-difference time-domain (FDTD) method in conjunction with the generalized pencil of function (GPOF) technique, to evaluate the reflection coefficient from shorted slotlines and coplanar waveguides, on anisotropic substrates. Identification of finite-difference time-domain solutions; Conclusions of the paper.

Multiarm slotline stubs have been used to increase the bandwidth of slotline open circuits in transitions between microstrip and slotline and between coplanar waveguide and slotline. The model used in prior papers is a series connection of the short-circuit terminated stubs, resulting in an increase in the input impedance by a factor of $N$ , where $N$ is the number of stubs. In this paper, it is shown that this model cannot be applied for slotline with finite width metal planes or coplanar stripline (CPS), because it does not account for higher order modes that are necessarily excited on the multiarm structure. This paper presents a physical explanation and model that accounts for the higher order modes on the structure and explains how the multiarm finite width slotline/CPS stub structure increases the bandwidth of the transitions between slotline and other transmission lines. With the correct model presented in this paper, it is expected that improved slotline or CPS circuits can be developed. [ABSTRACT FROM AUTHOR]

Research in millimeter dielectric waveguides is experiencing a growing interest for data communication and sensor systems. This paper fully analyzes the properties of the HE11 mode in hollow fibers. It will provide a theoretical background that can then be used to choose an appropriate channel for a dielectric waveguide system. The focus of this paper will be primarily laid on linking properties like propagation constant, dispersion, and attenuation with the geometry and frequency. Secondly, as a small cladding is needed in practical millimeter-wave fibers, evaluating the power leaking out of the fiber by means of the evanescent field is addressed. Finally, all theories are extensively verified with measurements and both agree very well. [ABSTRACT FROM PUBLISHER]

This paper presents several V-band (50–75 GHz) WR-15 and W-band (75–110 GHz) WR-10 waveguide components fabricated using both direct metal laser sintering in aluminum, nickel-chromium, maraging steel (MS), and copper alloys and stereolithography in copper-coated plastic. Printing resolution is analyzed with respect to feature creation. The RF performance and surface roughness are measured, and the loss due to surface roughness quantified. The measured loss for WR-10 at 92.5-GHz ranges from 5.5 dB/m for the copper-plated plastic waveguides to 36.9 dB/m for the nickel alloy and for WR-15 at 62.5-GHz ranges from 11.0 dB/m for the aluminum alloy to 14.4 dB/m for the MS alloy. From a loss budget study, it is found that standard models do not accurately predict loss due to surface roughness for rough surfaces where the height variation is much larger than skin depth $\delta$ . It is also found that for internally complex printing, the MS alloy versions maintain the closest structure to designed components and expected RF performance. This paper presents the current state-of-the-art in available additive-manufactured waveguide components at V- and W-bands. [ABSTRACT FROM PUBLISHER]

The eigenvalue diagram at the Dicke planes of the E-plane tee junction is not unlike that of the H-plane geometry available in the literature. The purpose of this paper is to remedy the situation. It includes an investigation of such a junction loaded with both inductive and capacitive vanes at its symmetry plane. This paper also introduces an alternate definition of the Dicke planes in terms of the location of a piston in the main waveguide, which produces a bandstop response between the other two and that of a similar piston in the side waveguide, which establishes a bandpass between the other two. The electrical symmetrical cases at the Altman and Dicke ports for which the magnitudes of the scattering parameters are those of a symmetrical wye junction are separately realized. Each solution has a distinct eigenvalue diagram, which is symmetric about the real axis. This paper includes the realization and fabrication of one device and is in excellent agreement with the theory. The work is undertaken in WR75 waveguide at a frequency of 13.25 GHz. [ABSTRACT FROM PUBLISHER]

On-wafer probing with ground–signal–ground (GSG) probes contributes a variety of side effects, which are related to the measured line type, the carrier material, the layout with the neighboring structures, and the probe. Thus, the size and shape of the probe together with the measured line type and the neighboring circuits influence the quality of the calibrated measured result. This paper presents corresponding results when using the multiline-thru-reflect-line (mTRL) calibration, which is commonly accepted as one of the most accurate calibration algorithms, and concentrates on the impact of the probe construction together with neighboring elements, for the most common planar transmission lines, coplanar waveguides (CPWs), and thin-film microstrip lines (TFMSLs). For the first time, design guidelines with regard to the layout, the measurement environment, and the construction of the probes are given. [ABSTRACT FROM AUTHOR]

This paper presents a detailed modeling and analysis regarding the dispersion characteristics of multilayered open coaxial waveguides or cables. The electromagnetic model is based on a layer recursive computation of axial-symmetric fields in connection with a magnetic frill generator excitation that can be calibrated to the current measured at the input of the cable. The layer recursive formulation enables a stable and efficient numerical computation of the related dispersion functions, as well as a detailed analysis regarding the analytic and asymptotic properties of the associated determinants. Modal contributions as well as the contribution from the associated branch-cut (nondiscrete radiating modes) are defined and analyzed. Measurements and modeling of pulse propagation on an 82-km-long HVDC power cable are presented as a concrete example. In this example, it is concluded that the contribution from the dominating axial-symmetric transverse magnetic mode is sufficient, and that the contribution from the branch-cut is negligible for all practical purposes, and in particular if the exterior domain is lossy. The main contribution of this paper is to provide the necessary modeling and analysis tools for a quantitative study of these phenomena. [ABSTRACT FROM PUBLISHER]

In this paper, we report on the numerical simulation of a multiphysic electromagnetic/mechanical problem, as a further step toward the development of microwave circuits based on phonon propagation at micro and nanoscale. In the future, this kind of circuits is likely to integrate optomechanically pumped phonon sources and detectors, as well as phonon processing components (waveguides, splitters, and memories) to process information by means of phonons. In particular, we propose a rigorous approach for the solution of the electromagnetic/mechanical system of equations governing light behavior in optomechanical cavities, with the help of the transformation optics method. Such a kind of calculation allows the development of an efficient generation of microwave coherent phonon sources, by engineering their propagation or coupling with phonon waveguides. [ABSTRACT FROM AUTHOR]

This paper addresses the robust mode computation of the metallic hollow cylindrical waveguide with parabolic contour. Although this waveguide can be solved by separation of variables, it has not been fully characterized in a systematic way in the past. This is not only due to its challenging manufacture, which nowadays can be addressed by modern techniques, but also because of its more complex resolution, involving root finding in a pair of coupled functions with two variables. In order to solve this system, this paper proposes the use of a recently published algorithm for bivariate problems, which is applied for the first time to waveguide mode computation. The method, properly combined with the even and odd Taylor functions, allows obtaining the modes in a systematic and robust way, avoiding, in comparison with previous works, graphical means and the use of starting points from which to iterate. All the modal solutions for symmetrical and asymmetrical cases are solved at once over a wide domain of search with proven high accuracy (relative difference with respect to results from a finite-element method in the order of 10^-5 for more than 1600 modes). [ABSTRACT FROM PUBLISHER]

A new cavity-based method to measure the complex permittivity of dielectric materials is presented here. The method uses a double-ridged waveguide for the cavity instead of the widely used rectangular waveguides, thus enhancing the operational frequency bandwidth by twofold. The bandwidth enhancement is advantageous when measuring the permittivities of frequency dispersive specimens. Building on the perturbation theory, this paper develops the measurement equations required for permittivity extraction. The measurement errors induced by the approximations in the perturbation theory are evaluated using numerical simulations, and the errors are quantified for different specimen sizes and dielectric constants. The experimental results are also presented. The complex permittivities of three common plastic specimens are measured at frequencies of around 3, 5, and 8 GHz using one double-ridged cavity. For comparison purposes, the same samples are also measured using two rectangular cavities operating in the S- and X-bands. Good agreement in the measured permittivity values is observed. [ABSTRACT FROM PUBLISHER]

A novel substrateless power amplifier module realized by ridge gap waveguide (RGW) technology is proposed in Ka-band. Up to our knowledge, this is the first time that an active device is directly integrated with an RGW structure. No substrate is used in the RF section of the implemented power amplifier and the whole structure is made by machining a piece of metal. The amplifier was made of two pieces and was easily assembled without needing a precise contact between the two sections. The cavity resonance of the amplifier is suppressed using a pining structure. The fabricated amplifier module is self-packaged and does not need any packaging. It is shown that the simulated and measured results are in good agreement. This paper shows the capability of RGW technology for implementing the whole RF frontend in microwave- and millimeter-wave systems. [ABSTRACT FROM PUBLISHER]

This paper presents an extension of the variational meshless method to the calculation of the dispersion diagram of metallic waveguides including inhomogeneous dielectric regions. The method is based on the combination of the variational formulation of a 2-D boundary problem and of the meshless method using radial basis functions. The problem requires a vector representation of the field, and it leads to a well-conditioned, real, and symmetric eigenproblem, where the matrices depend on the propagation constant $\beta $. By solving the eigenproblem for several values of $\beta $ , a spurious-free dispersion diagram of the guiding structure is obtained. Several structures are studied to demonstrate the accuracy and reliability of the proposed technique. The simulation results are compared with the analytical ones, when available, and with those given by a commercial FEM code, always showing a very good agreement with a smaller number of unknowns. [ABSTRACT FROM AUTHOR]

This paper presents, to the best of the authors’ knowledge, the first realizations of the Gysel-type power combiner/divider in ridge waveguide technology with two different configurations. Gysel combiners exhibit wider bandwidths than traditional combiners, while offering compact designs when implemented in ridge waveguide, compared with traditional waveguide combiners. In addition, Gysel combiners provide relaxed requirements on the power handling capability of the terminating loads in the case of fault conditions, which may result from imbalance between different inputs. The ridge waveguide designs offer better power handling capabilities, especially in comparison with planar designs. These advantages are shown with two different realizations, in top–bottom and side-by-side configurations, exhibiting very wide bandwidths while occupying very compact volumes. These two designs have been simulated, fabricated, and tested. Excellent test results have been obtained, confirming the validity of the concept. [ABSTRACT FROM AUTHOR]

This paper describes the novel design concept of a wideband noncircular choke flange for connecting two contactless waveguide joints with the variable air gap. Resonant enhancement of transmission loss is observed in the experiment as well as the numerical simulation in Ansys HFSS software when a 2-D standing wave is excited in the narrow air gap. The shape of the choke groove is designed in such a way that ensures standing waves cannot be excited in the frequency band of interest, even considering possible linear and rotational misalignments between the connecting joints during practical operation, thereby making the design very robust. The eigenmode analysis is performed to decompose the mixed excitation mode into the fundamental and higher order modes, and for the case of misalignment, revealing why the electric field changes the direction of rotation above and below the resonant frequency. Experimental measurement results of the fabricated egg-choke flange showed that the transmission loss is less than 0.1 dB in the 2.5-GHz bandwidth from 8.5 to 11 GHz with possible misalignment which validates the design. Other choke shapes are possible following the same design methodology with different scaling parameters depending on the desired frequency band of the user application. [ABSTRACT FROM AUTHOR]

Circular corrugated waveguides are often used in fusion applications at single, multiple, or broadband millimeter frequencies due to their low ohmic loss, expected large frequency bandwidth, and direct coupling to free-space Gaussian modes. For single-frequency corrugated waveguide systems, transmission line components can be optimized to the desired frequency. For broadband or multiple-frequency applications, this is not possible. The goal of this paper is to demonstrate that the frequency bandwidth of circular corrugated waveguides can be compromised by diffraction losses to miter bends and gaps. It is shown that if the corrugation depth differs significantly from $\lambda $ /4, a theory can substantially underpredict the gap and miter bend losses. The simulations are also shown to compare favorably to experimental measurements. To improve the transmission line performance in large frequency bandwidth systems, such as 33–165 GHz reflectometry, reducing the number of miter bends may, therefore, be necessary. For the improvement of performance in narrower frequency bandwidth or multiple-frequency systems, especially high-powered systems, wavelength-dependent techniques may be applicable. One such application is shown for a Bragg reflection technique to reduce the thermal load to insulating ceramic rings in a dc break component for multiple-frequency ITER electron cyclotron heating transmission lines. [ABSTRACT FROM AUTHOR]

It is very difficult to analyze electromagnetic (EM) responses of electrically large and complex objects because this requires a large amount of computing resources or extremely long calculation times. The EM topology (EMT) technique has been developed as a potential solution to overcome this resource-consuming limitation. The EMT technique can reduce computing resource by recombining EM analysis results of physically or electrically divided subblock models, instead of an entire model. However, the EMT technique still has some shortcomings to be overcome when applied to complex electrical systems subject to arbitrarily directional incoming sources. In this paper, we propose a wideband coupling analysis method by arbitrarily incoming sources based on the EMT technique for complex waveguide structures including a printed circuit board. A topological network is proposed that takes into account the effect on arbitrarily directional incoming sources with their polarization (vertical, horizontal, and circular). Explanations and definitions of several parameters for the proposed topological network are discussed. S-parameters are obtained using the CST-MWS tool. The analysis results of the proposed method, the entire model by the CST-MWS, and measurement results from a reference paper are compared, and the validity of the approach is verified. [ABSTRACT FROM AUTHOR]

This paper presents an airflow analysis and a shielding effectiveness (SE) analysis for a multilayered waveguide-below-cutoff array (WBCA) used to prevent electromagnetic penetration. The performance of the conventional unit square WBCA and the multilayered WBCA is compared. For the airflow analysis, the simulations are performed at the entrance and exit of the shielding structure when an airflow velocity of 1 m/s is injected at the inlet. The velocity loss and pressure difference of the multilayered WBCA are improved compared with the unit square WBCA. In terms of the shielding, the SE of the multilayered WBCA is compensated by increasing the number of overlapping layers. Furthermore, a new SE equation is derived by modifying that of the unit square WBCA. [ABSTRACT FROM AUTHOR]

Focuses on Eisenhart and Khan's scientific paper on waveguide circuit which serves as the basis for the selection of the 1999 Microwave Pioneer Award at the International Electrical and Electronics Engineering Microwave and Technology Society's International Microwave Symposium. Contribution to the field of microwave technology; Brief history of how the paper was written; Contents.

This paper presents a systematic investigation of quarter-mode filters in substrate integrated waveguide (SIW) technology. This class of filters is particularly convenient because it combines the features of SIW structures with the improvement of size reduction. After a thorough analysis of the quarter-mode SIW cavity, this paper presents different coupling mechanisms and feeding techniques for the design of quarter-mode SIW filters: side coupling and corner coupling are considered, highlighting the advantages and disadvantages of the two techniques. Novel filter topologies are introduced, with the design and experimental verification of simple filters and their extension to higher order filter structures. Techniques to introduce transmission zeros are described and demonstrated. Moreover, the combination of quarter-mode SIW cavities and coplanar waveguide resonators leads to increasing the filter order to higher order and allows the implementation of quasi-elliptic filters. [ABSTRACT FROM PUBLISHER]

In this paper, a guided-wave structure, the half-mode composite waveguide (HMCW) is proposed and presented. Similar to the conventional mode composite wave- guide (MCW), the HMCW also has an inner and outer waveguides, each working in its half-mode operation, respectively. In the HMCW structure, the signal propagates in the inner waveguide with quasi- $\text{TE}_{0.5-0}$ mode and along the outer waveguide with the quasi-TEM mode. The HMCW’s half-mode operation principle, impedance, loss, and propagation characteristics including higher order modes are analyzed. Compared to its full-size counterpart, the HMCW only occupies half the space, when operating within the same frequency band. Simulation results show that the transmission loss of the HMCW is comparable to that of the full-size MCW. Thus, it is also suitable for both low- and high-frequency design and applications. To measure and integrate the HMCW with other planar circuits, a joint feeding network for the HMCW is also proposed. Its circuit prototype is fabricated on three layers of substrate using a multilayer substrate integration technique. This joint feeding network can simultaneously excite the inner and outer waveguides, respectively, in an independent manner. In measurements, both the inner and outer waveguides are transitioned to microtrip lines, and a good matching is achieved from 4.4 to 11.2 GHz with a relative bandwidth of 87.2% for the outer waveguide at low frequency and from 18.6 to 32.6 GHz with a relative bandwidth of 54.7% for the inner waveguide at high frequency, respectively. [ABSTRACT FROM AUTHOR]

The objective of this paper is to use electromagnetic-based computer-aided design (CAD) tools to investigate the maximum tuning range of channel filters, typically used in satellite payloads. Both circular and rectangular waveguide technologies are investigated. The results of the investigation show that single-mode rectangular waveguide implementations offer substantially wider tuning range, as opposed to classical dual-mode circular waveguide implementations. In addition to simulations, measurements are also presented indicating very good agreement with theory, thereby fully validating the CAD procedure. [ABSTRACT FROM PUBLISHER]

In a metallic waveguide filled with a lossless anisotropic medium, do independent transverse electric (TE) and transverse magnetic (TM) modes exist? If so, under what conditions? This is a fundamental problem in the electromagnetic waveguide theory, but so far no definitive answers have been published in existing references. This paper proposes a sufficient and necessary condition for this theoretic electromagnetic waveguide problem based on both classic waveguide theory in electromagnetics and basic knowledge in mathematics. Moreover, we prove that for the independent TE modes, the propagation constants obtained from both the longitudinal scalar magnetic field simulation and the transverse vector electric field simulation are the same, and for the independent TM modes, the propagation constants obtained from both the longitudinal scalar electric field simulation and the transverse vector magnetic field simulation are the same. Finally, we validate the correctness of this sufficient and necessary condition by several numerical experiments based on the finite-element method. Therefore, this is a new theoretical result in the electromagnetic waveguide theory, and is expected to be valuable for the design of waveguides filled with anisotropic media. [ABSTRACT FROM PUBLISHER]

This letter is intended to point out a few typing mistakes in the above paper , which discusses computing the complex permittivity of a dielectric material embedded in a rectangular waveguide or a microstrip line, and to suggest corrections to its formulation. [ABSTRACT FROM AUTHOR]

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure. [ABSTRACT FROM AUTHOR]

In this paper, a novel and general method to synthetize microwave waveguide tapers intended for single-mode operation is proposed. The technique is based on the use of an exact series solution of the inverse scattering synthesis problem. An additional strategy necessary for dealing with waveguides where the propagation constant varies with the position is included. The coupled-mode theory is employed to model the electromagnetic behavior of the taper with the inherent mismatch caused by the connection of the waveguides with different cross sections. The novel method allows us to synthesize the (classical) transmission line taper functions of Klopfenstein and Hecken, making them suitable for general waveguide tapers with single-mode operation. Additionally, a new type of taper functions, also suitable for general waveguide tapers, is presented. The novel functions are obtained by partially employing the frequency response of multisection transformers, resulting in fully smooth tapers that can offer shorter lengths than the classical proposals. The taper synthesis procedure is demonstrated in rectangular waveguide technology, by requiring realistic and challenging specifications for different cases with different waveguide cross sections to be matched: height mismatch, width mismatch, and simultaneous height and width mismatch. Several prototypes of Klopfenstein, Hecken, and novel function tapers have been fabricated in an aluminum alloy by means of an Additive Manufacturing technique (Direct Metal Laser Sintering). The simulation and measurement results obtained for the rectangular waveguide taper prototypes confirm the accuracy of the novel synthesis technique proposed. [ABSTRACT FROM AUTHOR]

In this paper, a new transversal configuration is presented for waveguide bandpass filters (BPFs) on stacked rectangular $ H$ -plane waveguide cavities. Different from the conventional ladder BPFs, cavities constituting the proposed transversal BPFs are arrayed in a stacked manner. Odd- and even-mode resonators of transversal BPF are realized by TE101 and TE102 modes of rectangular $ H$ -plane waveguides, respectively. Using the configuration proposed herein, the realization of an $N$ th-order filter could be decomposed into realizations of $N$ first-order subfilters, and each subfilter could be realized independently, which is guaranteed by the unique array of resonators of transversal filters. Therefore, the complexity of realizing BPFs could be reduced, especially for filters with multiple transmission zeros (TZs). A class of transversal filters, including BPFs and dual-band filter, are synthesized, fabricated, and measured to verify the approach. [ABSTRACT FROM AUTHOR]

This paper investigates the fabrication accuracy and repeatability of micromachined quadruplet filters designed at a center frequency of 270 GHz with a 5-GHz bandwidth using a versatile multilayer chip platform which allows for axially arranged waveguide ports. A large number of narrowband silicon-micromachined filters arranged on multiple chips are investigated for fabrication imperfections, assembly misalignment, and fabrication yield, employing fabrication-prediction and different chip-to-chip self-alignment feature strategies. A numerical technique for characterization of the entire fabrication process of the filters through extracting the error statistics for coupling coefficients of a large number of different samples from separately assembled chips is proposed. A total of 47 test filters in effectively 15 different design variants have been fabricated in two fabrication runs, evaluated, and analyzed. The most critical sources of errors are determined. The expected accuracy of the entire filters fabrication process is demonstrated through the yield analysis based on the collected error statistics. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of probe excitations for 7- and 10.5-T traveling-wave wide-bore magnetic resonance imaging systems. The probes are 297- and 447-MHz coaxially fed microstrip patches, designed to give a circularly polarized magnetic field when placed in the metallic bore waveguide. Images of a water phantom using the patch probes are obtained and compared with full-wave electromagnetic simulations. Additionally, periodic axial metal strip cylinders are inserted into the bore, resulting in improved field uniformity in a phantom with a simultaneous increase in SNR. The numerical analysis for nonquasi-static fields can be computationally intensive, and the numerical error for finite-element simulations is quantified using modified boundary conditions of the system. When the waveguide effects are taken into account, the mode content in the images compares well to full-wave simulations. [ABSTRACT FROM PUBLISHER]

Numerical results generated by computer codes written based on a full-wave modal analysis of transverse corrugated circular waveguides with segmented grooves and a waveguiding core that is stratified into concentric layers, as detailed in a previous paper, are presented here. It is shown that the reduction of metal losses and enhancement of the aperture efficiency of the operational mode can be achieved by ceramic linings of the groove floors as well as the surface of the corrugations. The benefits of chamfering the groove-floor coating are also demonstrated. Dielectric losses and thermal and RF breakdown are also studied. [ABSTRACT FROM AUTHOR]

This paper presents a new class of dual-band filters and diplexers, realized based on dual-band resonators. The proposed dual-band filter and diplexer do not require junctions and can achieve equivalent performance with fewer cavities, thus offering a significant reduction in size compared with traditional approaches. The concept is potentially applicable to most dual-band cavities and is demonstrated in this paper using elliptical and rectangular waveguide cavities. The first design is an inline structure employing elliptical cavities, whereas the second design is implemented through a unique layout that combines the use of dual-band and single-band rectangular cavities. The result is a group of highly compact dual-band filters and diplexers that offer increased Q and an improved spurious-free window. To verify the concept, an eighth-order Ku-band elliptical dual-band filter and a fourth-order Ku-band rectangular diplexer are designed, manufactured, and tested to allow comparisons with traditional designs. [ABSTRACT FROM AUTHOR]

Deembedding a device mounted between a pair of identical transitions requires the transition two-port parameters. These can be obtained using the through-line (TL) deembedding method requiring only through and uniform line deembedding standards. Other related deembedding methods introduce factors to scale a pair of eigenvectors to obtain the transition two-port parameters. In this paper, it is shown that these scaling factors are interdependent and provide a corrective reference plane adjustment. Moreover, the transition wave-transmission matrix can be factored into two wave-transmission matrices with one encapsulating the transition discontinuity and the other of a matched line to provide a corrective reference plane shift. This factorization permits incorporation of desired and corrective reference plane shifts, using data from a second matched line standard. With an emphasis on substrate-integrated waveguide, the proposed TL deembedding method is verified. [ABSTRACT FROM PUBLISHER]

In this paper, mode composite waveguide (MCW) is proposed, which consists of inner and outer wave-guiding duo structures. The outer structure acts as a rectangular coaxial line suitable for lower frequency operation for its compact size, while the inner structure works as a rectangular waveguide suitable for higher frequency operation thanks to its simple structure and low loss. The MCW can propagate signals in the inner waveguide with TE10 mode and/or the outer waveguide with TEM mode depending on frequency to achieve optimal performance for both low- and high-frequency operations. In this paper, the fundamental waveguide parameters and higher order modes of the duo waveguides are examined. The proposed MCW prototypes are fabricated on a triple-layer PCB structure using the emerging substrate integration techniques. The MCW is fabricated and measured through the proposed microstrip line to the inner and outer waveguide transitions, and an MCW simultaneous feeding circuit is also presented. For this simultaneous feeding circuit, the good matching is achieved from 7.5 to 10.5 GHz for the low-frequency operation and from 25 to 39 GHz for the high-frequency operation, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, we present a comparative study of S-parameter measurements of electronic components on planar substrates performed with a waveguide module and in a conventional on-wafer probing environment. Measurements were conducted at three well-established measurement laboratories for the investigation of reproducibility at frequencies from 110 to 170 GHz. For the comparison, we fabricated waveguide modules for six passive structures, including devices under test (DUTs). Four of these structures are related to using a second tier calibration to achieve the same reference planes for the waveguide module measurements as used for the on-wafer probing measurements. Additionally, we processed three complete on-wafer calibration sets, including DUTs, equipped with different probe-to-pad interfaces. In this comparison, the DUT measurement from the waveguide module acts as a reference standard, with reduced crosstalk behavior in comparison to the on-wafer measurement. With the waveguide reference, we are able to assess the ability of two techniques to compensate for crosstalk and higher order modes influencing the on-wafer S-parameter measurements. On the one hand, we use a shielded probe-to-pad transition and on the other hand, we use an algorithm-based crosstalk correction scheme. To the best of our knowledge, this is the first time that such a comparison has been undertaken, comparing well-established waveguide calibrations with an equivalent on-wafer calibration. [ABSTRACT FROM AUTHOR]

In this paper, it is provided a full characterization analysis of the losses contributing to the series resistance of ground-shielded coplanar waveguide interconnects. For this purpose, the loss components associated with the signal trace, the ground path, the shield, and radiation are separately determined by processing experimental data and electromagnetic simulations. This also allowed for the identification of the impact of the skin effect on the losses occurring within the ground shield. Experimental curves corresponding to lines exhibiting different shields are represented up to 30 GHz using the proposal. Furthermore, different resistive components are obtained as a function of the trace width and spacing to figure out the effect of geometry on the series resistance. In addition, a time domain analysis is included to assess the impact of neglecting each one of the resistive components on the quality of a multigigabit-per-second digital signal. [ABSTRACT FROM AUTHOR]

In this paper, a bandpass frequency selective surface (FSS) based on substrate-integrated waveguide (SIW) technology is presented for airborne radome application. The proposed FSS element consists of a tapered cross-slot on either side of the substrate surrounded by metallic vias. The structure selectively allows the impinging electromagnetic (EM) wave through it in the specified frequency band. The element shows very stable frequency response for oblique incidence and the sharp roll-off performance characteristics at the edges of operating region in the rejection band. The −10 dB relative bandwidth (BW) of the element is 12.8% from 9.5 to 10.8 GHz with a very good insertion loss (IL) of 0.1 dB. Furthermore, the spectacular advantages of the FSS element based on SIW have been used for modeling the airborne radome application. The proposed radome structure is operating at 10 GHz with a relative 10 dB BW of 25.0% (8.20–10.6 GHz) with maximum (IL) better than 0.1 dB in its passband. The behavior of the FSS radome has been analyzed at different conformal sectors and thickness is optimized for optimal performance. The key parameters of radome such as transmission performance, radiation efficiency, and radar cross section (RCS) have been studied. Experimental verifications are carried out to prove the validity of the estimated results. The results show promising performance of the proposed FSS based on SIW technology for airborne radome application. [ABSTRACT FROM AUTHOR]

This paper presents the proposal and design of multistate diplexer on uniform- and stepped stub-loaded resonators, that is, a three-state diplexer (TSD) and a four-state diplexer (FSD). The two proposed diplexers have an attractive application in a frequency-hopping system with miniaturization in their overall size. Next, three and four sets of second-order bandpass filters are applied to form the three and four filtering channels, respectively. These filtering channels are then used to comprise these multiple-state diplexers. In this way, compact size and high-frequency selectivity have been well achieved. For the purpose of demonstration, the prototypes of TSD and FSD are fabricated and measured. The measured results are found in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

A Ka-band broadband TE01-mode overmoded waveguide bend based on an elliptical waveguide structure is proposed for high-power transmission line in this paper. To investigate the mode conversion inside the waveguide bend, the mode coupling coefficients of elliptical waveguide bend are theoretically deduced. The influence of the cross section on the power-handling capacity and the transmission efficiency is studied. Calculation and simulation results present that the proposed overmoded waveguide bend has a propagation bandwidth of 7 GHz (relative bandwidth of 21%) with an efficiency over 95%. A prototype is fabricated and measured. The average transmission efficiency is over 93% in the range of 29–36 GHz according to the S-parameter measurement. The results of near-field test demonstrated that a TE01 mode with high purity is obtained at the output port of waveguide bend. The high-power performance is investigated by connecting it with a Gyrotron traveling wave tube, and the waveguide bend works stable under a maximum output power of 150 kW. The measurement results demonstrate that a novel approach is proposed successfully for the design of high-power waveguide bend. [ABSTRACT FROM AUTHOR]

This paper describes a simple analysis of the guided waves in an eccentric circular waveguide based on the bipolar coordinate system (BCS). The separation of the variable technique is used for the solution. The structure under study is an infinite perfect electric conductor (PEC) cylinder in the z-direction, which encloses eccentrically another infinite PEC cylinder. The modal analysis has been conducted using an analytical method, solving the TE and TM modes by the aid of electromagnetic formulation. Despite previous studies which mostly rely on numerical techniques or otherwise considering the dominant TEM mode, in this paper, the analytical solution is proposed for the electromagnetic fields which consequently lead to the characterization of the cutoff wavenumbers of higher order modes and explicit solution to electric and magnetic fields in BCS. The solution of the Helmholtz equation in BCS using the technique of separation of variables exhibits as a one of the contributions of this paper, and the validity range of the answer is discussed. The values of the cutoff wavenumbers for the first few modes are calculated and compared with the benchmark results. The precise correspondence of the obtained values with the proposed method with those of the previous studies and computer simulations, along with the high speed and simplicity in implementation, introduces the present method as an appropriate option for analyzing eccentric circular cylindrical structures. [ABSTRACT FROM AUTHOR]

This paper reports precision measurements of the electromagnetic permittivity of five highly refractive, single-crystal materials, SrTiO3, KTaO3, rutile TiO2, LiTaO3, and LiNbO3, using a single, well-controlled, frequency-scalable procedure over the frequency ranges 25–110 and 140–220 GHz. Real permittivity values were highly consistent for different samples measured across multiple frequency bands. For SrTiO3, KTaO3, and TiO2, real permittivities were more consistent with lower frequency values than typically reported in the millimeter-wave region of the spectrum. Real permittivities of LiTaO3 and LiNbO3 agreed with most reported data. The intrinsic dielectric loss of SrTiO3, KTaO3, and the extraordinary axis of rutile TiO2 was also characterized over the ranges 25–110 and 140–220 GHz, and intrinsic loss per unit frequency was found to be consistent with values measured at other frequencies by dielectric resonators and quasi-optical techniques. [ABSTRACT FROM AUTHOR]

Additive manufacturing technology has enabled the manufacturing of complex structures, especially those with intricate internal features. This paper proposes a method for building complex-structured millimeter-wave waveguides using a strategy that combines digital light processing 3-D printing technology, a curved corner design, an off-axis print angle of 45°, and a robust postmetallization process. To demonstrate the capability of this combined-strategy method, a traditional magic tee prototype and an adapted inherently matched magic tee prototype are fabricated for use in the W-band. The measured performance of the fabricated inherently matched magic tee demonstrates return loss better than 13.5 dB, isolation coefficients higher than 15.7 dB, insertion losses smaller than 1.3 dB, and a magnitude imbalance of less than 1.3 dB across 80–105 GHz. The 3-D printed magic tee has a comparable performance to a W-band CNC-machined magic tee but weighs 77.5% less than the metallic one. [ABSTRACT FROM AUTHOR]

This paper proposes and describes in detail a new approach to the design of very compact active microwave compressors capable of providing rectangular pulses of up to 100 ns. The approach consists in using a storage cavity, which comprises linear waveguide sections connected by tees such that the cavity geometry can be 2-D or 3-D or can be variable to allow direct space-saving integration of a compressor into a microwave source. Also presented are the scattering matrix data on uniform wave propagation along the storage cavity with little reflection and on conditions necessary for such uniformity. The S-band experiments demonstrate the capability of storage cavities with two and three parallel waveguide sections of about 1 m long to produce rectangular pulses of duration 5, 15, and 25 ns with a power gain and output power of about 16 dB, 80 MW; 15 dB, 60 MW; and 13 dB, 40 MW, respectively. Our estimates suggest that 12 waveguide sections can provide a rectangular pulse of 100 ns with a power gain 10 dB. [ABSTRACT FROM AUTHOR]

In this paper, a novel waffle-iron filter with transmission zeros at multiple frequencies, along with its design procedure, is presented. The proposed filter features a high-power behavior and a wide rejected band in a single compact structure by means of a set of transmission zeros that can also be placed close to the passband. Its design method rests on a divide-and-rule strategy, where the physical dimensions of the constituent design entities can be easily computed in a very short time. A novel high-power compact waffle-iron filter with transmission zeros at multiple frequencies has been designed as well as several classical waffle-iron filters with transmission zeros at one frequency only, using a detailed step-by-step procedure which avoids the brute-force optimizations needed until now. Multipactor and corona simulations have been conducted proving a high-power handling capability of 1.8 kW and 78.6 W, respectively. A prototype of the novel filter has been fabricated, obtaining a remarkable accordance between the simulated and measured results. [ABSTRACT FROM AUTHOR]

A new approach for the design of a balanced bandpass filter (BPF) is presented in this paper. Stemming from the mode degeneration properties of a square patch resonator, a complete set of resonant modes in a right-angled isosceles triangular patch resonator (RAITPR) is thoroughly investigated so as to construct a modified RAITPR with one electric wall and two magnetic walls along its three sides for filter design. This proposed resonator can support the half-TM10-mode of the RAITPR, and thus, it is named as the half-mode RAITPR here. By properly adopting the relationship between one RAITPR and two coupled half-mode RAITPRs, a second-order coupling topology is presented. Its working principle is then explained by using the field distribution of the desired resonant modes involved. A few high-order balanced filters are in final implemented and fabricated to evidently demonstrate their good differential-mode filtering selectivity and high common-mode suppression. Good agreement is achieved between the simulated and measured results for all the designed three balanced BPFs. To further improve the concerned out-of-band rejection performance, the feeding scheme of the modified structure has been discussed. [ABSTRACT FROM AUTHOR]

This paper presents a simple, low-cost, hours-long fabrication method for microwave waveguide components of high RF performance. The technique combines 3-D-printed configurations with liquid metal waveguide structures. As a demonstration, a fused deposition modeling multimaterial 3-D consumer-grade printer and liquid gallium were used. A conductive polylactic acid (PLA) waveguide flange was 3-D printed along, in-one-go, with standard PLA for the rectangular waveguide liquid metal enclosures. Microwave WR62 waveguides, resonators, and filters operating in Ku-band were designed, fabricated, and tested. The RF performance of the fabricated waveguide devices is in agreement with the simulations demonstrating better than 1.29 dB/m attenuation in the waveguide and better than 1000 $Q$ -factor for the resonator and the filter at 13 GHz. The fabricated devices demonstrate a new option of an economical fabrication technology for high RF performance microwave waveguide-based devices that can be delivered in hours-time, anywhere, anytime with minimal equipment deployment and investment. [ABSTRACT FROM AUTHOR]

This paper reports on, for the first time, the design of filtering couplers with reconfigurable frequency. The reconfigurable filtering transmission lines (RFTLs) with 90° or −90° phase shift are first designed, and then the reconfigurable filtering couplers are constructed by substituting the basic unit of quarter-wavelength ($\lambda/4$) transmission line in the conventional couplers with the proposed RFTL. The tunable capacitor loaded half-wavelength ($\lambda/2$) resonators are used to tune the center frequency of RFTL. By properly controlling the electric or magnetic coupling between the resonators, the phase shift of 90° or −90° of the RFTLs can be realized, respectively, while maintaining a near constant bandwidth. The external coupling along with a pair of transmission zeros is achieved by asymmetric tap feeding of the RFTLs. For verification, a class of frequency-reconfigurable filtering couplers is designed and fabricated. First, a reconfigurable filtering rat-race coupler is designed and fabricated. The measured center frequency is tuned from 700 to 1840 MHz while maintaining a 3-dB fractional bandwidth of 13% ± 0.5%/13.7% ± 0.6%, insertion loss of 8.1–6.9/8.3–5.9 dB, return loss of better than 13 dB, and isolation of better than 21 dB. Second, a reconfigurable filtering quadrature coupler is designed and fabricated. The measured center frequency is tuned from 947 to 1775 MHz while maintaining a 1-dB bandwidth of 75 ± 5/65 ± 10 MHz, insertion loss of 8.3–6.9/8.3–7.1 dB, return loss of better than 14 dB, and isolation of better than 14 dB. [ABSTRACT FROM AUTHOR]

This paper presents a new class of cavity-based triple-band filters employing resonators that support three operation modes. The proposed triple-band filters do not require junctions and can achieve an equivalent Chebyshev performance with fewer cavities, thus significantly reducing the footprint when compared to traditional approaches. The filter facilitates a systematic design approach starting from the coupling-matrix generation to the overall response optimization. The concept is potentially applicable to most triple-mode resonators and is demonstrated in this paper using waveguide and dielectric resonators. The first design is an inline structure employing elliptical waveguide cavities, whereas the second design is a folded structure using rectangular waveguide cavities. The third design is implemented by dielectric loaded cavity resonators. All the proposed triple-band filter designs offer high Q and allow for independent control of each frequency and coupling parameter. To verify the concept, three triple-band filter examples with different realizations are designed, manufactured, and tested to allow comparisons. [ABSTRACT FROM AUTHOR]

The two-port reflection gyromagnetic waveguide switch described in this paper consists of a 90° Faraday rotator in a re-entrant or an inverted re-entrant turnstile geometry in the E-plane at the junction of two H-plane rectangular waveguides. It adjustment is a two-step eigenvalue problem. One adjustment fixes the electrical length of the circular Faraday rotator waveguide and produces a passband in its frequency response and the other fixes its gyrotropy and produces a stopband there. This paper also includes the separate synthesis of the passband condition in a WR75 waveguide at a frequency of 13.25 GHz using two different processes. The switch has two passband conditions at the design frequency, each of which is verified experimentally The stopband is separately established experimentally by magnetizing the gyromagnetic resonator. [ABSTRACT FROM AUTHOR]

In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26–33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K. [ABSTRACT FROM PUBLISHER]

In this paper it is shown that the traditional shunt admittance represented by a rational function yields an accurate wideband equivalent circuit for multi-aperture waveguide irises. The electromagnetic analysis of the structures reveals two different types of resonant phenomena. The first type of resonance is associated with the cutoff frequency of the TE10 mode. The second type or antiresonace corresponds to short-circuit TEM modes. These antiresonances are generated when the asymmetry of the iris allows the excitation of electric fields with opposite phases at contiguous apertures. The proposed equivalent circuit is a shunt admittance represented by a rational function. This rational function is analytically obtained from the singular points (resonances and antiresonances) identified in the full-wave analysis. It is straightforward to obtain the circuit elements from the rational function by following the classical one-port synthesis leading to Foster’s or Cauers’s canonical realizations. One advantage of the proposed equivalent circuit is that it represents the electromagnetic behavior of complicated structures with a minimum number of circuit elements or degrees of freedom. Several examples, with different number of apertures and symmetry, are presented to illustrate the proposed general equivalent circuit. Finally, the proposed procedure is extended to the case of arbitrary shaped irises, such as those used in frequency-selective surfaces. [ABSTRACT FROM PUBLISHER]