Search

The editor reflects on the special issue of the periodical which is based on the 2012 International Microwave Symposium held on June 17-22, 2012 in Montreal, Quebec. He mentions that due to increased number of submissions to the special issue, it has been divided into two issues the first one was published in December 2012, and the next one in January 2013. He adds that the aim behind including conference papers in the issue is to present results that might help improve engineering designs.

Compact and high-data density microwave encoders useful for motion control and near-field chipless radio frequency identification (chipless-RFID) applications are proposed in this paper. The encoders are chains of metallic strips etched on a dielectric substrate. The reader consists of a microstrip line loaded with a pair of identical open-ended folded stubs located at different positions and oriented face-to-face by their extremes. By displacing the encoder over the extremes of the stubs, interstub coupling arises when a strip is located on top of the stubs, thereby generating two transmission zeros (rather than one) in the frequency response of the line. Thus, the presence of a strip on top of the face-to-face stubs produces a variation in the transmission coefficient of the line, which in turn can be detected by feeding the line with a harmonic signal, conveniently tuned. Encoder motion generates an amplitude modulated (AM) signal at the output port of the line with peaks, or dips, separated by a time distance dictated by the relative velocity between the reader and the encoder. Moreover, by making certain strips of the chain inoperative (e.g., by cutting them), it is possible to encode information that can be read as the absence (logic state “1”) or presence (logic state “0”) of peaks, or dips, at predefined positions in the output AM signal of the reader line. Since short strips suffice to generate interstub coupling, unprecedented data density per surface (DPS = 26.04 bit/cm2) is obtained, as revealed by the implementation of 6.4 mm $\times60$ mm 100-bit encoders. [ABSTRACT FROM AUTHOR]

The application of stacked-FETs in power amplifiers allows for a supply voltage higher than supported by the breakdown voltage of a single transistor. Potential benefits of the increased supply voltage are reduced supply currents and a lower matching ratio at the output of the amplifier. Furthermore, an increased output power per chip area is obtained due to the reduction in passive structures resulting in more area-efficient power combining. In this paper, the procedure for the design of integrated microwave stacked-FET is discussed. Several options for the correct distribution of RF voltage and current swings are investigated and the relationship between the number of stacked transistors and bandwidth is addressed. The procedure is demonstrated by the design of an S-band GaAs stacked-FET containing three transistors. This stacked-FET is applied in an S-band HPA that has a PAE of more than 40% at an output power of 20 W, which is more than twice the output power of any previously reported GaAs stacked-FET HPA. [ABSTRACT FROM AUTHOR]

This paper demonstrates direct detection of weak signals at microwave frequencies based on parametric frequency conversion. The atomic medium is optically pumped by a resonant light field and prepared in a coherent atomic superposition by a weak microwave field. The coherent atomic superposition causes a parametric modulation of the polarization of a probe light field at the microwave field frequency. An upper limit magnetic field component sensitivity of 1.2(1.0) pT/Hz1/2, corresponding to 3.7(3.1)- $\mu $ V/cm/Hz1/2 electric field component sensitivity, is achieved at ~6.835 GHz with a 33-mm3 vapor cell. [ABSTRACT FROM AUTHOR]

This Special Issue is formed by collecting 46 regular papers on the topic of systems and applications, which reflects the latest progress in microwave systems and applications from MHz to THz. All those 46 papers are divided into six subtopics, namely, digital predistortion of RF power amplifiers (five articles), radar systems and applications (14 articles), wireless systems (nine articles), detectors and imaging (ten articles), microwave applications (five articles), and microwave power transfer technologies (three articles). [ABSTRACT FROM AUTHOR]

Large metallic losses and short propagation lengths associated with surface plasmons (SPs) have long been considered as the obstacles which severely limit the practical applications of surface plasmonic waveguides. In this paper, we introduce the concept of dielectric spoof SPs (SSPs) and show that subwavelength high-contrast gratings (HCGs) offer a route to effectively suppress the losses and hence dramatically increase the propagation length of surface electromagnetic waves. We experimentally realized a wideband ultra-low-loss high-confinement plasmonic waveguide constructed by a high refractive-index dielectric array with deep-subwavelength periodicity on a metal substrate. Simulation and measurement results on the nearfield distributions and S-parameters at microwave frequencies provide explicit evidences of strong field localization and show excellent transmission efficiency of HCGs-based SSPs across a broad frequency band. More importantly, the propagation length of the HCGs-based SSPs is proved to be at least more than one order of magnitude larger than that of metallic gratings-based SSPs at the same or even higher level of field confinement. Thus, the SSPs as experimentally realized in this paper hold great promise for numerous practical applications in ultra-low-loss and long-range transmission SP devices and circuits and may open up new vistas in SP optics. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental measurement of power threshold levels for the multipactor effect between samples of ferrite material typically used in the practical implementation of L- and S-band circulators and isolators. For this purposes, a new family of wideband, nonreciprocal rectangular waveguide structures loaded with ferrites has been designed with a full-wave electromagnetic simulation tool. The design also includes the required magnetostatic field biasing circuits. The multipactor breakdown power levels have also been predicted with an accurate electron tracking code using measured values for the secondary electron yield (SEY) coefficient. The measured results agree well with simulations, thereby fully validating the experimental campaign. [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]

Recent developments of microwave ablation systems pursue a treatment monitoring technique in order to provide a curative therapy option for cancer patients. In this paper, such an approach is realized by a dual-mode microwave applicator that enables the permittivity extraction of the tissue surrounding the applicator during the intervention. The additional sensing mode facilitates the positioning of the applicator by detecting dielectric contrasts to indicate the presence of tumors as well as providing tissue state information during the thermal therapy. This feature is based on a one-port calibration scheme which is applied before each intervention. Measurements of various sodium chloride solutions reveal a measurement error below 4%. Furthermore, ex-vivo liver ablation experiments with the input powers of 10 and 20 W are performed to evaluate the treatment monitoring feature and ablation efficacy. A significant permittivity drop down to 82% of the initial permittivity value can be observed after 2 min of ablation. The achieved ablation zones show a preferably spherical shape and clinically relevant volumes with a maximum size of 7.1 cm3. [ABSTRACT FROM AUTHOR]

In this paper, a fast solution for microwave through wall imaging (TWI) with nonlinear inversion is proposed to reconstruct the unknown targets embedded in an inhomogeneous background medium. We treat inhomogeneous background, i.e., the wall around bounded in a finite domain as a known scatterer, which has the advantage of avoiding the time-consuming calculation of inhomogeneous background Green’s function. Under this scheme, a new approach under the framework of difference integral equation model, i.e., difference Lippmann–Schwinger integral equation, with modified enhanced Levenberg–Marquardt algorithm is proposed. In particular, we used a hybrid regularized technique, i.e., generalized cross-validation and truncated singular value decomposition, to stabilize the inversion. It is shown that the proposed method runs fast and is stable in presence of noise. Also, it is able to alleviate the nonlinearity and reconstruct unknown scatterers of high contrast with respect to the background. Both the numerical and experimental TWI tests validate the efficiency of the proposed inversion method. [ABSTRACT FROM AUTHOR]

Microwave cavity perturbation measurements are a useful way to analyze material properties. Temperature changes can be introduced during these measurements either intentionally or as a result of some other process. The microwave cavity itself also has a temperature-dependent response, which can affect the results. A common method to correct is to use another resonant mode separately to the measurement mode, which is not affected by the sample. Instead of using independent modes, this paper describes a method to use split degenerate TMm10 modes of cylindrical cavities. TMm10 consists of two modes with identical field patterns with a relative rotation between them and identical resonant frequencies. A strategically placed perturbation reduces the frequency of one of the TMm10 modes and affects the coupling of both modes by reconfiguring the fields. This can be used for temperature correction by placing a sample such that both modes are equally coupled. The lower frequency, the perturbed mode is used as a measurement mode. The higher mode is used as a reference for temperature correction as it is unaffected by the sample. This technique was verified by measuring the permittivity of pure water using an aluminum microwave cavity resonator at 3.96 GHz. The temperature was swept between 20 °C and 60 °C, and the results was verified against the literature. [ABSTRACT FROM AUTHOR]

A robust cavity technique is proposed to quite accurately measure the complex permeability of the magnetic materials, which gives promising results for arbitrary length samples. This technique takes into account many factors such as magnetic field correction inside the sample under test, the effect of demagnetization, and the image theory, which was not considered in past. In this paper, a numerical model of the magnetometric demagnetization factor is developed, which precisely considers the effects of the relative permeability of sample and the nonuniform magnetic field over sample volume. The sensitivity of proposed technique is better than conventional and recently modified technique assuming arbitrary length sample. The proposed scheme typically provides 98% accurate result for the sample length greater than $0.15\times $ the width of the rectangular cavity. The proposed method is quite novel and can be appreciated due to the fact that it gives higher accuracy for all the cases when compared with other standard cavity techniques. [ABSTRACT FROM AUTHOR]

This paper presents a miniaturized contact-based system for dielectric spectroscopy using time-domain (TD) technique in ultrawideband (UWB) frequency range. The system consists of a miniaturized UWB transmitter, a planar sensor having direct contact with a liquid material under test (MUT), and a high-speed oscilloscope receiver. In the transmitter, a baseband (BB) pulse with 3.5-GHz bandwidth is generated from a square-wave input signal by employing a step recovery diode and a short-circuited stub. Then, the BB pulse is upconverted by a UWB mixer with 6.5-GHz local oscillator frequency, creating a 3–10-GHz passband pulse. After being amplified, the passband pulse excites the miniaturized sensor, including two stages of microstrip open-circuited stub between meander inductors. This sensor has a small area, requires only 0.3 $\mu \text{L}$ of liquid MUT for accurate sensing, and responds to both $\epsilon '$ and $\epsilon ''$ properties. The sensor output is captured by the oscilloscope in TD and then converted to frequency domain (FD) by the fast Fourier transform operation. Considering $\epsilon '$ and $\epsilon ''$ of MUT simultaneously affect both phase and magnitude of output signal in FD, the behavior of the system is described by testing 12 reference MUTs. From the behavioral model of the system, three unknown MUTs are characterized with errors less than $0.1|\epsilon ^{*}|$ in both $\epsilon '$ and $\epsilon ''$ from 3.28 to 10 GHz. [ABSTRACT FROM AUTHOR]

The behavior of a power amplifier (PA) is substantially affected by the output mismatch and mutual coupling in modern compact transmitters. To date, different works in the literature address the problem of coupling and mismatch separately, which are limited in terms of performance with a higher level of mismatch and mutual coupling. This paper identifies the reflection at the PA–antenna interface to be an effective parameter to unify the problem of mismatch and mutual coupling. Thus, a reflection-aware PA modeling and linearization method is proposed to compensate the adverse effect of mismatch and/or mutual coupling. The performance of the proposed method is investigated with a class AB and a Doherty PA under wide range of output mismatch and/or mutual coupling conditions with a 20-MHz WCDMA signal. The proposed method shows robust performance with an average adjacent channel power ratio better than 45 dBc. Such robust linearization performance under diverse output mismatch and mutual coupling conditions is highly desirable for modern and future communication systems that are subject to undergo rapid fluctuations under antenna matching and cross-coupling conditions. [ABSTRACT FROM AUTHOR]

This paper introduces an efficient radar transmitter with improved spectral confinement, enabled by a pulse waveform that contains both amplitude and frequency modulation. The theoretical behavior of the Class-B power amplifier (PA) under a Gaussian envelope is compared to that of a Class-A PA. Experimental validation is performed on a 4-W 10-GHz GaN monolithic microwave integrated circuit PA, biased in Class B with a power-added efficiency (PAE) of 50%. When driven with a Gaussian-like pulse envelope with a 5-MHz linear frequency modulation (LFM), the PA demonstrates a 31% average efficiency over the pulse duration. To improve the efficiency, a simple resonant supply modulator with a peak efficiency of 92% is used for the pulse Gaussian amplitude modulation, supplemented by pre-distortion on the PA input, while the LFM is provided through the PA input. This case results in a five-point improvement in system efficiency with an average PAE=40\\% over the pulse duration for the PA alone, and with simultaneous 40-dB reduction in spectral emissions relative to a rectangular pulse with the same energy. [ABSTRACT FROM PUBLISHER]

This paper presents a center frequency and bandwidth reconfiguration mechanism for waveguide microwave bandpass filters. The filters are designed to be used in the output section of a satellite communication system. While the center frequency of a bandpass filter can be tuned by changing the lengths of the filter resonators, the coupling irises as practical realizations of the impedance inverters cannot easily be adapted to a new value. The novel approach chosen in this paper is to replace the impedance inverters by a novel type of coupling structure. This coupling structure allows adjustment of the coupling by changing the length of a transmission line, which is equivalent to changing the resonant frequency of a coupling resonator. Design equations are presented to transform an impedance inverter into the proposed coupling structure. A synthesis procedure for bandwidth reconfigurable filters is proposed. The feasibility of coupling adaptation is proven based on a full-wave model of the coupling structure. The synthesis process is applied to a four-pole Chebyshev sidewall-coupled circular waveguide filter with 54- and 72-MHz bandwidth settings. The filter is built up and measured. The measured results prove that the filter can be tuned to both bandwidths over a center frequency range of 200 MHz with excellent return loss and insertion loss. [ABSTRACT FROM PUBLISHER]

To satisfy the simultaneous requirements of future wireless communication systems on short-range high-speed data transmission and long-distance basic coverage, the coexistence of the millimeter-wave and microwave technologies becomes the inexorable trend. However, it is difficult for the existing dual-/ tri-band filter configurations to achieve a frequency ratio larger than three. In this paper, the new use of aperture coupling mechanism is proposed to combine two bandpass elements for dual-/tri-band operation with large frequency ratio but comparable sizes. For this purpose, a microwave BPF with wide stopband up to millimeter-waveband is implemented based on the complementary frequency response characteristics of the stepped-impedance resonator bandpass filter and low-pass filter. The millimeter-wave BPF can be simply designed using the air-filled substrate-integrated waveguide circular cavities, which exhibit the natural low-frequency cutoff characteristics. Based on the proposed design concept and two BPF elements, the dual-/ tri-band bandpass filters with frequency ratio up to 12.59 and 12.7 were designed, fabricated, and measured. Owing to the independence of the two elements, a diplexer with large frequency ratio can be simply implemented based on the previous dual-band filter. All the simulation and measured results are in good agreement, validating the proposed structures. [ABSTRACT FROM AUTHOR]

In this paper, the generalized substrate integrated waveguide (SIW) cavity technique is presented for the retrieval of broadband complex permittivity of medium loss dielectrics using a number of higher order modes of the proposed cavity. The proposed SIW cavity design improves the coupling by implementing a novel feeding topology to achieve a better quality factor for the higher order TE $_{10n}$ modes as compared with the conventional SIW feeding arrangement. The conventional SIW cavity perturbation formula is modified to overcome various limitations of the SIW topology, such as the lower $Q$ -factor, lower sample to cavity volume ratio, and larger frequency shifts observed for the higher order modes. The applicability of the proposed technique is first numerically validated using independent data obtained with the help of full-wave electromagnetic solver, and then, the accuracy is compared with various cavity-based techniques available in the literature. Finally, the proposed SIW cavity sensor is fabricated on Rogers’ RT5880 substrate, where a number of standard RF substrates are tested using the network analyzer. The proposed generalized scheme based on the improved SIW cavity provides reasonably accurate values of the complex permittivity of the medium-loss dielectric substrates at multiband of microwave frequency in the range of 10–20 GHz. [ABSTRACT FROM AUTHOR]

This paper outlines the conversion of a domestic microwave oven for use in composite curing applications. It compares several strategies for temperature control. The converted oven has vacuum ports, connectors, and fiber optic thermocouple sensors. Experimental data are provided for each control strategy based on a 200~\text mm \times 200 mm eight-ply prepreg laminate. The degree of cure is established for the test samples by thermal analysis techniques. Multiphysics simulation is used to model the electromagnetic and heating effects in the system, and a common and inexpensive method of approximating the available microwave power is used. The low cost of the microwave components and the ease of conversion are desirable characteristics in this application. [ABSTRACT FROM PUBLISHER]

This Special Issue of IEEE Transactions on Microwave Theory and Techniques (TMTT) is comprised of the expanded papers from the 2021 IEEE Microwave Theory and Techniques Society (IEEE MTT-S) International Microwave Symposium (IMS2021), held in Atlanta, GA, USA, on June 2021. The IEEE MTT-S International Microwave Symposium is the world’s major event of microwave technologies annually organized by the IEEE MTT-S as the society’s premier flagship conference. The conference represents a unique opportunity to bring together researchers and practitioners with diverse technical backgrounds to share the most recent advances in MHz-to-THz technologies and systems. Due to the unprecedented pandemic situations, the IMS2021 was held in a hybrid format, comprised of in-person and virtual participation options. The in-person event was held on June 7–10, 2021, at the Georgia World Congress Center, Atlanta. A virtual event followed on June 20–25, 2021. [ABSTRACT FROM AUTHOR]

This paper proposes a pole-residue-based adjoint neuro-transfer function (neuro-TF) technique with electromagnetic (EM) sensitivity analysis for parametric modeling of EM behavior of microwave components with respect to changes in geometrical parameters. The purpose is to increase model accuracy by utilizing EM sensitivity information and to speed up model development by reducing the number of training data required for developing the model. The proposed parametric model consists of original and adjoint pole-residue based neuro-TF models. New formulations are derived for calculating the second-order derivatives for training the adjoint pole-residuebased neuro-TF model. An advanced pole-residue tracking technique is proposed to exploit the sensitivity information to track the splitting of poles as geometrical parameters change. This pole-residue tracking technique allows the model to bridge the differences of the orders of transfer function over different regions of the geometrical parameters, and ultimately form smooth and continuous functions between the pole/residues and the geometrical variables. The proposed technique addresses the challenges of tracking pole splitting when training data are limited. By exploiting the sensitivity information, the proposed technique can speed up the model development process over the existing pole-residue parametric modeling method which does not use sensitivity analysis. [ABSTRACT FROM AUTHOR]

Developments in microwave and millimeter-wave systems have enabled remote sensing techniques traditionally used in long-range applications to be employed in the relatively closer range applications of detection and classification of human presence and measurement of human properties. This paper reviews the techniques used in microwave remote sensing of humans and discusses prominent examples of experimental systems from the literature. Radar techniques have been developed for measuring the time-varying scattering returns from the various parts of the human body during motion, which are used for human presence detection and the classification of human activities. The effects of breathing and heartbeat are also detectable using Doppler radar techniques, which is applicable to medical applications as well as search-and-rescue and security. Recent developments in distributed radars have enabled the direct measurement of the angular velocity of moving people, and passive systems have also been developed which provide a complementary detection mode that can aid in detection and classification of humans. [ABSTRACT FROM AUTHOR]

Several different microwave circuits, including beamforming networks and balanced amplifiers, make use of 3-dB power dividers and combiners. A well-known architecture able to work over large bandwidths, a critical request for many applications, is based on E-plane three-port waveguide structures, where a lossy element is added to overcome the inherently poor isolation given by lossless three-port junctions. While a standard implementation based on normal rectangular waveguides often results in large and heavy structures, an implementation based on substrate-integrated-waveguide (SIW) technology offers advantages in terms of compactness, weight reduction, cost minimization, and integration possibilities with active stages. This paper presents the design, fabrication, and characterization of two SIW E-plane 3-dB power divider/combiners where the lossy element is realized using a resistive layer. The prototypes cover the entire $X$ -band from 8 to 12 GHz, and the resistive layers are realized according to two different manufacturing techniques to investigate the potentials of both approaches. The optimization of the resistive layer geometry and resistivity, a critical aspect for low-profile SIW circuits, is discussed in detail. In particular, an analytical formula is derived, which allows to determine the optimum values for the resistive layers’ principal parameters, namely the length and resistivity, without the use of full-wave numerical solvers. [ABSTRACT FROM AUTHOR]

Moving elements have been widely used to improve heating uniformity in microwave applicators, such as rotating turntables and mode stirrers. However, it remains a challenge to compute the heating process due to the difficulty of meshing the element’s dynamic locations. In this paper, we propose a novel algorithm to solve this problem accurately and efficiently. Being surrounded by moving elements with a time-varying anisotropic layer on the basis of transformation optics, the electromagnetic field inside applicators can be computed with consideration of continuous motion of moving elements. A 2-D applicator model with a rotating turntable is used to illustrate the proposed algorithm in detail. Furthermore, we also compute the heating process of a practical 3-D applicator model with a rotating turntable. Compared with the conventional method, the proposed algorithm is more efficient and accurate. The computational results are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to the identification of output power and efficiency contours in microwave power transistors in compressed regime. The formulation is based on a polynomial representation of the drain–source voltage profile accounting for the knee region. Closed-form equations for the output power and efficiency as function of the fundamental load are demonstrated, enabling the plot of contours on a Smith Chart. From these, a further simplified drawing procedure for approximated contours is also derived, differentiating between two families of output characteristic. The first, with smooth knee, is usually experienced in GaN devices, while the second exhibits a steep knee which can be associated with GaAs devices’ typical behavior. A 5-W GaN HEMT, a 2.5-W GaN HEMT, and a 0.7-W GaAs pHEMT are characterized with load-pull measurements. In all the three cases, the proposed method results in a very accurate contour construction, despite being based on an approximated output current/voltage profile and on a rough estimate of output equivalent capacitance. [ABSTRACT FROM PUBLISHER]

A theoretical comparison of the fundamental limitations on the output power and the third-order distortion of balanced diode mixers and even harmonic mixers is described in this paper. In the authors’ previous work, formulas for the output power limitations of the mixers in a modulator operation were described. Using the described formulas, the output power and the third-order distortion of the mixers are calculated for a mixer operation and are represented as universal charts. Further, the closed-form formulas for the output power at a 1 dB gain compression and the intercept point of the third-order intermodulation products are presented. As mixers in a modulator operation, it is clarified that even harmonic mixers have a lower output power capability than balanced diode mixers. All the derived formulas were confirmed with experimental investigations at 100 MHz. [ABSTRACT FROM AUTHOR]

Microwave photonics is a rapidly-growing interdisciplinary field linking microwave and optical technologies. This paper intends to trace the evolution of microwave photonics over the last three decades emphasizing some major research areas and application fields. Currently, microwave photonics is a vivid research area with several practical applications. In this paper, we attempt to project potential future trends as well. [ABSTRACT FROM PUBLISHER]

This paper proposes a new topology for a broadband low-noise-amplifier (LNA). A common-gate (CG) amplifier with a matching inductor composes a unit cell, and the unit cells are cascaded to increase gain. As both the input and output impedances of the unit cell are matched to 50 Ω for a wide frequency range, it is possible to increase the gain while maintaining wide bandwidth. Thus, high-gain and broadband performance can be obtained using this topology. The other features of the amplifier are its small size, low power consumption, and current reuse topology. This paper presents the design methodology of a multistage CG amplifier with a matching inductor. Fabricated in an 80-nm InP HEMT process, we developed an ultra-broadband LNA. The LNA with a three-stage CG amplifier exhibited a gain of 18 dB and a noise figure of 3.5 dB from 68 to over 110 GHz. The power consumption was 12 mW under a power supply voltage of 3 V. The chip size is 0.55 x 0.75 mm². Furthermore, we developed a receiver for passive millimeter-wave imagers by integrating a six-stage LNA with a power detector. The chip size of the receiver is 1.1 x 0.75 mm². The sensitivity of the pre-amplified detector was more than 2 000 V/mW from 75 to 100 GHz. These results show that the topology is one of the best candidates for high-gain and broadband LNA with small size and low power consumption. [ABSTRACT FROM AUTHOR]

A comparative study of state-of-the-art behavioral models for microwave power amplifiers (PAs) is presented in this paper. After establishing a proper definition for accuracy and complexity for PA behavioral models, a short description on various behavioral models is presented. The main focus of this paper is on the modeling accuracy as a function of computational complexity. Data is collected from measurements on two PAs--a general-purpose amplifier and a Doherty PA designed for WiMAX--for different output power levels. The models are characterized in terms of accuracy and complexity for both in-band and out-of-band error. The results show that, among the models studied, the generalized memory polynomial behavioral model has the best tradeoff for accuracy versus complexity for both PAs, and can obtain high performance at half of the computational cost of all other models analyzed. [ABSTRACT FROM AUTHOR]

This paper describes a method to extract the relative complex dielectric permittivity from propagation coefficient measurements on microstrip lines. The material characteristics of microstrip lines fabricated on two different types of substrates commonly used in microwave circuit and printed circuit boards are investigated. The mechanisms that cause the effective permittivity of microstrip lines to be dispersive are explored. The technique includes creating closed-form effective permittivity equations to relate the effective permittivity of the microstrip lines to the real part of the dielectric permittivity of the substrate. Curve-fitting methods are used to create causal dielectric material models that relate the imaginary part of the dielectric permittivity to its real part. The methods developed in this paper can be used to characterize low-loss dielectric materials whose polarization is dominantly dipolar within the microwave frequency range in high-speed packaging applications. [ABSTRACT FROM AUTHOR]

This paper proposes new solutions for implementing wideband large switch matrices. These solutions are based on crossbar and L-shaped topologies. This paper introduces a high-performance wideband switch cell to build up scalable N × N switch matrices and gives an account of the design, fabrication, and characteristics of the switch cell and a 3 × 3 crossbar switch matrix. The chosen design procedure is seen to be appropriate since it produces valid measured results. In addition, this paper presents an RF microelectromechanical systems L-shaped switch matrix, which indicates less variation of characteristics for certain types of connectivity. It also demonstrates that for a 4 × 4 switch matrix, there is a 50% improvement in insertion loss and phase-shift variation. [ABSTRACT FROM AUTHOR]

Randomly dispersed particles in a material can be forced to align due to the presence of an externally applied field. These self-aligning materials are examples through which order is obtained through structure created internally which alters the bulk properties of the material. One such material is a magnetically aligned anisotropic conductive adhesive which uses the alignment of ferromagnetic particles in order to create current flow in only one direction. This paper discusses microwave application of such a material. We demonstrate that the magnetically aligned Z-axis anisotropic conductive adhesive works at microwave frequencies interconnecting silicon substrates through 90 GHz. The Z-axis material is found to be a suitable replacement for solder bumping even at high frequencies of operation. The effect of material composition and the radio frequency design is discussed in this paper. Finally, the Z-axis anisotropic conductive adhesive is found to be a suitable cost-effective replacement for solder bumps at high frequencies. [ABSTRACT FROM AUTHOR]

Crosstalk induced in a meander delay line produces a significant amount of waveform distortion and data-dependent jitter at the output port. This paper introduces an interpretation of the eye-diagram distortion and the jitter generation mechanism based on a time-domain even- and odd-mode analysis of a coupled transmission line structure. From the proposed analysis, this paper proposes jitter-estimation equations for both the short and long unit line delay cases. The eye-diagram distortion and timing jitter are predicted and estimated, respectively. In order to verify the jitter-estimation equations, a series of microstrip-type printed circuit board test vehicles with the meander delay line are fabricated and tested. The measured jitter shows good agreement with the proposed jitter-estimation equations. [ABSTRACT FROM AUTHOR]

This paper presents generalized Chebyshev microstrip filters with box-like coupling schemes. The box-like coupling schemes taken in this paper include a doublet, extended doublet, and fourth-order box section. The box-like portion of the coupling schemes is implemented by an E-shaped resonator. Synthesis and realization procedures are described in detail. The example filters show an excellent match to the theoretical responses. [ABSTRACT FROM AUTHOR]

This paper presents a coupled electrothermal, electromagnetic, and physical model for microwave power field-effect transistors (FETs). The resulting model is used to investigate large gate periphery pseudomorphic high electron-mobility transistor devices. The contribution to the output power of each cell of the transistor is simulated, as well as their contribution to the heating of the device. This approach allows the investigation of the interaction between the thermal behavior, the dc bias, and the microwave circuit operating conditions. This paper reveals for the first time a more complex interaction between the thermal and microwave behavior of large-power FETs [ABSTRACT FROM PUBLISHER]

This paper presents the analysis and the design rules of bipolar junction transistor (BJT) class-F power amplifier operating at a frequency comparable with the transition one. Since the impulse of collector current becomes stretched with operation frequency increasing, its spectral content is changed. Thus, the requirements for the amplifier's output network and bias conditions should be corrected compared with the classic low-frequency case in order to achieve high-efficiency class-F operation. Using the simple BJT model, these new requirements were obtained in this paper. The presented results of simulation and experimental verification show the advantages of proposed approach. [ABSTRACT FROM AUTHOR]

A set of design criteria for the radio-frequency (RF) section of long-range passive RF identification (RFID) transpon- ders operating in the 245-GHz or 868-MHz industrial, scientific, and medical (ISM) frequency ranges is derived in this paper, focusing in particular on the voltage multiplier, the power-matching network, and the backscatter modulation. The paper discusses the design tradeoffs between the error probability at the reader receiver and the converted RF-dc power at the transponder, determining the regions of the design space that allow optimization of the operating range and the data rate of the RFID system. [ABSTRACT FROM AUTHOR]

This paper addresses the properties of a surface-passivated (enhanced) high-resistivity silicon (HRS) substrate for use in monolithic microwave technology. The detrimental effects of conductive surface channels and their variations across the wafer related to the local oxide and silicon/silicon-dioxide interface quality are eliminated through the formation of a thin amorphous layer at the wafer surface. Without passivation, it is found that the surface channels greatly degrade the quality of passive components in HRS by masking the excellent properties of the bulk HRS substrate and by causing a spread in parameters and peak values across the wafer. Moreover, it is seen that the surface passivation leads to excellent agreement of the characteristics of fabricated components and circuits with those predicted by electromagnetic (EM) simulation based on the bulk HRS properties. This is experimentally verified for lumped (inductors and transformers) and distributed (coplanar waveguide, Marchand balun) passive microwave components, as well as for a traveling-wave amplifier, through which also the integration of transistors on HRS and the overall parameter control at circuit level are demonstrated! The results in this paper indicate the economically important possibility to transfer microwave circuit designs based on EM simulations directly to the HRS fabrication process, thus avoiding costly redesigns. [ABSTRACT FROM AUTHOR]

This paper introduces nonlinear transmission lines based on left-handed (LH) media and simulates harmonic generation and parametric generation in a material that, in two dimensions, could also focus microwaves. This paper discusses physical phenomena that lead to and affect self-supporting harmonic generation and parametric generation in LH nonlinear transmission-line media and outline advantages of these media for developing new types of compact and efficient frequency multipliers and "active lens" devices. [ABSTRACT FROM AUTHOR]

Microwave imaging via space-time (MIST) beam-forming has been proposed recently for detecting small malignant breast tumors. In this paper, we extend the previously presented two-dimensional space-time beamformer design to three dimensional (3-D), and demonstrate its efficacy using experimental data obtained with a multilayer breast phantom. The breast phantom consists of a homogeneous normal breast tissue simulant covered by a thin layer of skin simulant. A small synthetic malignant tumor is embedded in the breast phantom. We have developed several tumor simulants that yield the range of dielectric contrasts between normal and malignant tissue that are expected in clinical scenarios. A microwave sensor comprised of a synthetic planar array of compact ultrawide-band (UWB) antennas is immersed in a coupling medium above the breast tissue phantom. At each position in the array, the antenna transmits a synthetically generated pulse (1-11 GHz) into the phantom. The received backscatter signals are processed by a data-adaptive algorithm that removes the artifact caused by antenna reverberation and backscatter from the skin-.breast interface, followed by 3-D space-time beamforming to image backscattered energy as a function of location. Our investigation includes a numerical (finite difference time domain) and experimental study of the UWB antenna performance in the immersion medium, as well as a study of the influence of malignant-to-normal breast tissue dielectric contrast on dynamic range requirements and tumor detectability. This paper represents the first experimental demonstration of 3-D MIST beamforming in multilayer breast phantoms with malignant-to-normal dielectric contrasts down to 1.5: 1 for a 4-mm synthetic tumor. [ABSTRACT FROM AUTHOR]

In this paper, a new version of the iterative multiscaling method (IMM) is proposed for reconstructing multiple scatterers in two-dimensional microwave imaging problems. This paper describes the new procedure evaluating the effectiveness of the IMM previously assessed for single object detection. Starting from inverse scattering integral equations, the problem is recast in a minimization one by defining iteratively (at each level of the scaling procedure) a suitable cost function, firstly allowing a detection of the unknown objects, successively a location of the scatterers, and finally, a quantitative reconstruction of the scenario under test. Thanks to its properties, the approach allows an effective use of the information achievable from inverse scattering data. Moreover, the adopted kind of expansion is able to deal with all possible multiresolution combinations in an easy and computationally inexpensive way. Selected numerical examples concerning dielectric, as well as dissipative objects in noisy environments or starting from experimentally acquired data are reported in order to confirm the usefulness of the introduced tool and of the effectiveness of the proposed procedure. [ABSTRACT FROM AUTHOR]

Dual-behavior resonators (DBRs) are based on the parallel association of two different bandstop structures, which implies a constructive recombination. Two kinds of stubs, stepped-impedance and different-length stubs, are examined in this paper. The first section concerns stepped-impedance stubs. We have previously reported some simplifications of the fundamental equations. Here, we propose a new simplification together with synthesis; both allow an independent control of the two attenuated bands. In a second section, a DBR composed of two uniform stubs of different lengths is studied instead of two stepped-impedance open-circuited stubs. This implies a greatly simplified synthesis and implementation. Some other structures combining short- and open-circuited stubs are also introduced. Throughout the paper, simulations are proposed to illustrate the possibilities offered by such topologies. Experimental results in microstrip technology are also presented in order to validate our idea. Finally, benefits and drawbacks of the different structures are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the analysis of a wide variety of microwave components like posts, circular junctions, or corners in rectangular waveguides. The method gives the impedance or admittance matrix of the microwave component by applying discrimination between the localized and accessible modes in the indirect mode matching (IMM) formulation. In this way, the method is more simple and versatile than previous modeling techniques where IMM is involved, since no use of a Green's function is required for the coupling between different ports. Furthermore, additional obstacles, like posts at the center of a circular junction, can be considered as different terminations of the corresponding transmission lines. The formulation is given for a two-port as well as a multiport system, and in the present paper numerical demonstration is provided for an abrupt and a step H-plane transition from a rectangular to a radial waveguide, a centrally located H-plane circular post in a rectangular waveguide, and a two-port circular junction between rectangular waveguides. The results are compared with the High Frequency Structure Simulator. In all of the aforementioned cases, the method proved to be fast, very accurate, and easy to implement. [ABSTRACT FROM AUTHOR]

In this paper, we present a method for designing temperature-compensated cavity resonators using shape memory alloys (SMAs). This paper gives an expression for the temperature drift of resonant frequency, which is valid for any conductor-loaded cavity regardless of its shape. This formula, combined with a field perturbation model, is used to derive the resonant frequency of an SMA-compensated resonator subject to temperature fluctuation. Experimental results are given that confirm the feasibility of the proposed design approach. A design method is proposed for specifying SMA alloys to build the actuator. An expression is derived to accurately predict the performance of an actuator design. Index Terms—Cavity resonator; filter; temperature compensation. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

The article outlines the procure for the Paper Submission in Electronic Form for authors. Topics include the guidelines provided by the journal "IEEE Transactions on Microwave Theory & Techniques"; Microsoft Word is the preferred format for this final submission, page charges for traditional submissions.

A general approach for calculating tip–sample capacitance variation in near-field scanning microwave microscopy is presented. It can be applied to arbitrary tip shapes, thick and thin films, and variation due to inhomogeneous perturbation. The computation domain for the tip–sample interaction problem is reduced to a block perturbation area by applying Green’s theorem, and thus it can save substantial time and memory during calculating either electric field or contrast capacitance for three-dimensional models of near-field microwave microscopy. We show that this method can accurately calculate capacitance variation due to inhomogeneous perturbation in insulating or conductive samples, as verified by finite-element analysis results of commercial software and experimental data from microwave impedance microscopy. More importantly, the method in this paper also provides a rigorous framework to solve the inverse problem, which has great potential to improve resolution by deconvolution. [ABSTRACT FROM PUBLISHER]