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This Mini-Special Issue of the IEEE Transactions on Microwave Theory and Techniques includes five expanded papers from the IEEE International Conference on Numerical Electromagnetic Modeling and Optimization for RF, microwave, and terahertz applications (NEMO), held in Beijing, China, July 27–29, 2016. [ABSTRACT FROM PUBLISHER]

Presents the author's comments on a study of microwave conductivity of a polymeric material with potential applications in absorbers and shielding. Shielding effectiveness; Return loss of a double-layer electric Salisbury screen with the same conditions.

This Transactions’ Mini-Special Issue includes four papers from the 2018 IEEE Radio and Wireless Week (RWW 2018) held in Anaheim (Garden Grove), CA, USA, January 14–17, 2018. RWW consists of five conferences focusing on the wireless communication theory, systems, circuits, and device technologies. They include the Radio and Wireless Symposium, Topical Conference on Power Amplifiers for Wireless and Radio Applications, Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Topical Conference on Wireless Sensors and Sensor Networks, and Topical Workshop on The Internet of Space. The program included parallel track technical sessions, three workshops, an Internet of Things (IoT) summit, a plenary session on IoT within 4G/5G networks, a panel session on the role of the device in power amplifier design, a joint RWW student paper contest, and a demo track session. A total of 243 papers were submitted to the RWW 2018 Technical Program Committee and 177 papers were accepted for presentation at the meeting and publication on the IEEE Xplore website. [ABSTRACT FROM AUTHOR]

This paper is aimed to compare the performance of toroidal inductors and planar spiral inductors in multilayered technologies, in terms of achievable inductance density. The optimization of planar toroidal inductors in multilayered substrates is investigated theoretically, and closed formulae are derived for their inductances as a function of geometrical parameters. The obtained model is validated by experimental results and electromagnetic simulation. From the comparison of the inductance of toroidal inductors and compact spiral inductors, a selection rule is proposed to choose the most suitable topology that leads to the most compact design. [ABSTRACT FROM AUTHOR]

The article calls for papers related to microwave theory for the periodical.

These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal. [ABSTRACT FROM AUTHOR]

These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal. [ABSTRACT FROM AUTHOR]

This paper provides theoretical and experimental evidence that, contrary to what is a widely reported belief, the capture time constant of GaN high-electron-mobility transistor (HEMTs) deep-level traps is not infinitesimally shorter than the modulation envelope time features of usual excitation signals. Instead, it can have a nonnegligible impact on their power amplification. A specifically conceived test bench, capable of measuring capture time constants at guaranteed invariant thermal dissipation conditions, revealed that the capture process can range from less than a microsecond up to a few tens of milliseconds. Furthermore, a theoretical justification based on the Shockley–Read–Hall statistics is provided to explain this widespread time constants’ behavior of deep-level traps. As a practical application example of these findings, the detailed characterization of the capture time constants performed in this paper proved to constitute a valuable tool in understanding the behavior of GaN power amplifiers (PAs) designed for pulsed radar signals. [ABSTRACT FROM AUTHOR]

Time reversal (TR) relies on the reciprocity nature of the wave equation. Waves diverging away from a source can be time reversed and back-propagated to focus back at the source. The transmitting and receiving antenna arrays utilized for TR are collectively termed as the TR mirror (TRM). TR imaging in the microwave regime has shown its promise in nondestructive inspection and target localization. This paper deals with the design of a microwave TRM for the detection of breast tumors. The first part of this paper discusses TR simulations based on a signal processing algorithm, to obtain the tumor location from the total fields. The processed time-reversed fields can be back-propagated in a numerical model to focus the wave at the tumor locations. Simulation results aid in investigating the feasibility and the robustness of the method. The second part of this paper deals with experimental studies for the breast tumor detection, using a pulsed time-domain system and the back-propagation model. The successful detection of single and multiple tumors embedded in a liquid breast tissue-based phantom is shown using the microwave system. [ABSTRACT FROM AUTHOR]

This paper presents a seven-port modulator capable of switching the polarization state of the transmitting signal. Similar to the six-port modulator, the proposed device modulates the carrier signal through the reflection coefficients generated by four variable loads. The additional seventh port allows feeding two antennas or a dual-port antenna. The loads control both the complex envelope and the polarization of the transmitted carrier signal. The mathematical model of the device, developed in this paper, is applied to analyze its performance and different modes of operation. For validation, a prototype is manufactured for a center frequency of 1575.42 MHz. It is used to generate M-quadratic-amplitude modulation at different polarizations. The signals recorded at the output of the prototype show good agreement with the values predicted by the model. [ABSTRACT FROM AUTHOR]

This paper presents a new bandwidth tuning theory for Butterworth-response resonator filters. The presented theory shows that the bandwidth of odd-order Butterworth filters can be varied by adjusting only two interresonator coupling structures while maintaining a perfect impedance matching at the center frequency. In other words, this paper presents an analytic approach to reduce the number of tunable coupling structures when designing a bandwidth-tunable resonator filter. Theories for third- and fifth-order direct-coupled filters are discussed in detail, and it is shown that only two interresonator coupling structures are required to be tunable. In addition, for verifying the new bandwidth tuning method, a fifth-order cylindrical cavity filter has been designed, fabricated, and measured. The fabricated filter has an 11:1 bandwidth tuning range. [ABSTRACT FROM AUTHOR]

This paper proposed a method of synthesizing absorptive common-mode filters (A-CMFs) analytically with high absorption efficiency and two designable absorption bands. The proposed method is carried out by a novel circuit architecture and its analysis procedure. In differential mode, the integrity of the differential signals is maintained, and in common mode (CM), two absorption frequency bands can be obtained theoretically. These bands are designable with the analytical equations derived in this paper, so a dual-band or broadband A-CMF design can be easily synthesized by our proposed method. The authors also show that this method can make any one of R-CMFs “upgrade” to an A-CMF by simply adding an additional circuit, and this might be a revolutionary progress for the currently used CM-suppression techniques. To make the proposed concept more understandable, an example is used to demonstrate how the synthesizing methodology works, where a broadband A-CMF with its absorption bands located at 2.4 and 3.6 GHz is designed and implemented. Furthermore, a test sample of this A-CMF is fabricated on a four-layer printed circuit board. It is measured on a probing station, and the measured results are very similar to the simulated results. Finally, a comparison table of all the related works is given, showing that this proposed method really makes a significant improvement for A-CMF techniques. It is worth noting that this circuit design can provide a broadest 95%-absorption band to our best knowledge. [ABSTRACT FROM AUTHOR]

This paper presents a set of wideband, fully integrated E-band power amplifiers (PAs) designed in 0.12- $\mu \text{m}$ silicon-germanium (SiGe) BiCMOS and working in the range of 60–75 GHz. The single PA is based on common-emitter (CE) driver stages followed by a CE output stage. A three-stage and four-stage versions of the single-PA as well as four- and eight-way combined variants of the four-stage PA are measured and compared. The single, four-way, and eight-way combined PAs achieve saturated output powers of 16, 19.5, and 24 dBm with peak power-added efficiencies (PAEs) of 18%, 11%, and 12%, respectively. Modulated waveforms are passed through each amplifier and data rates as high as 32 Gb/s are demonstrated for all amplifiers when driven in the linear mode. Measurements of how error-vector magnitude (EVM) and PAE degrade versus output power are presented and it is demonstrated that the eight-way combined PA can deliver 17–20 dBm of average power in a 64-quadratic-amplitude modulation, 1-Gbaud waveform (6 Gb/s), with an EVM of −32 to −24 dB and a PAE of 3%–5% without predistortion. To the author’s knowledge, this is the first paper reporting detailed measurements of PA EVM and PAE versus output power at these frequencies. [ABSTRACT FROM AUTHOR]

This paper proposes a new design methodology of dual-band stripline circulator for wireless communications applications. As far as the monoband classic circulator is based on coupling the counter-rotating fundamental modes, the operating principle of dual-band phenomenon is based on studying both fundamental and upper resonant modes within ferrite disks. Electromagnetic (EM) simulations have shown that two categories of dual-band operation could be obtained: simple (unidirectional) and left-handed /right-handed (LH–RH) circulators. The application dedicated to these two original concepts will be discussed, and simulation results will be ensured by the measurement of two prototypes in order to validate the methodology’s reliability. [ABSTRACT FROM AUTHOR]

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]

In the recent years, Wireless Power Transfer (WPT) related technologies experienced a great growth. With the introduction in 2010 of the Qj standard, many wireless rechargeable devices appeared on the market, calling for solution of several classes of problems ranging from EMC, health compliance, and power efficiency, representing a stimulating field of activity for scientists and researchers. Beside this leading application area, great interest is being received by two other application categories: Electric Vehicles (EV) and long range electromagnetic transmission of energy. The first is about to approach the market as testified by recent demonstration activities carried on by leading car makers (mostly from Japan). The second is mostly driven by the Internet of Things (loT) perspective evolution that requires energizing plenty of contactless devices, often non-precisely referred in space. It is clear, even from this very synthetic description of the WPT scenario, how WPT actually is an inclusive, multidiscipline field of different but dependent researches. This special issue aims at evidencing, within this scientific vastness, those aspects more precisely related to RF and microwave technologies in a wide extent (from MHz up to THz). Authors should see http://www.mtt.org/transactions/34-author-information-transactions.html for submission instructions. [ABSTRACT FROM PUBLISHER]

Wireless Power Transfer (WPT) related technologies have experienced a great growth. With the introduction in 2010 of the Qj standard, many wireless rechargeable devices appeared on the market, calling for solution of several classes of problems ranging from EMC, health compliance, and power efficiency, representing a stimulating field of activity for scientists and researchers. Beside this leading application area, great interest is being received by two other application categories: Electric Vehicles (EV) and long range electromagnetic transmission of energy. The first is about to approach the market as testified by recent demonstration activities carried on by leading car makers (mostly from Japan). The second is mostly driven by the Internet of Things (loT) perspective evolution that requires energizing plenty of contactless devices, often non-precisely referred in space. It is clear, even from this very synthetic description of the WPT scenario, how WPT actually is an inclusive, multidiscipline field of different but dependent researches. This special issue aims at evidencing, within this scientific vastness, those aspects more precisely related to RF and microwave technologies in a wide extent (from MHz up to THz). Authors should see http://www .mtt.org/transactions/34-author-information-transactions.html for submission instructions. [ABSTRACT FROM AUTHOR]

This paper presents a broadband poly-harmonic behavioral model for microwave mixers operating in the linear regime. It is extracted from large-signal vector measurements and predicts the response with respect to an arbitrary local oscillator (LO) phase. The model is capable of estimating the performance of the converted signals and the main mixing products for an intermediate frequency that spans within an a priori defined bandwidth. This paper gives a detailed model analytical treatment along with a discussion of its properties and the description of the characterization method. The model validation is achieved by the characterization of a subharmonic mixer implemented in the hybrid technology that operates with a 2.229-GHz LO, an intermediate frequency bandwidth of 732–754 MHz, and a corresponding radio frequency bandwidth of 5.191–5.211 GHz. Independent experimental validation is achieved by an image rejection mixer composed of two nominally identical mixers, individually characterized by the proposed technique. Validation is concluded with experimental data, demonstrating the model’s capability to deal with a phase-modulated LO signal. [ABSTRACT FROM PUBLISHER]

Self-tracking receivers have been suggested for satellite and mobile communication applications. In this paper, we propose and demonstrate an array receiver (Rx) architecture based on phase-locked loops. The system is capable of automatically tracking a moving source and providing direction-of-arrival (DOA) estimates calculated from array signal phase differences. After deriving the system transfer functions, we show a digital implementation of the receiver and experimentally prove its phase detection capability. In combination with an eight-element linear array and analog front ends, we build a hybrid receiver and demonstrate its DOA estimation performance in static and dynamic outdoor setups. This paper gives the details about theoretic principles, implementation concept, and realization of the proposed receiver. We demonstrate DOA errors below 4° and show the reproducibility of the results. Using dynamic experiments, we verify the tracking ability of the system, which makes it applicable to retrodirective antennas. [ABSTRACT FROM PUBLISHER]

This paper addresses the estimation and compensation of I/Q imbalance, one of the most prominent impairments found in wideband zero-intermediate frequency transceivers (TRxs). The I/Q imbalance encountered in this kind of TRx comprises not only frequency-selective gain and phase imbalance but also delay imbalance. Unless appropriate compensation is applied, the I/Q imbalance significantly degrades the performance of a communication system. This paper presents a novel compensation technique for transmitter I/Q imbalance based on built-in-self-calibration, a low cost and robust compensation technique that enables manufacturing as well as in-field calibration with low computational complexity. The method's performance is evaluated in a TRx with 64-quadratic-amplitude modulation and 2 GHz of bandwidth implemented with real hardware. The measurements show that the proposed technique achieves an image rejection ratio greater than 35 dB in the entire 2 GHz bandwidth and an error vector magnitude lower than 3%. [ABSTRACT FROM AUTHOR]

This paper presents a new spiral inductor based on substrate integrated suspended line (SISL) technology. SISL is a new type of transmission line, which has many merits, such as low loss, low dispersion, and self-packaging. New series of spiral inductors based on this advanced SISL platform is proposed and modeled in this paper. SISL to microstrip transition is designed for the measurement of the SISL inductor, and an open-short deembedding method is introduced for the accurate extraction of inductor network parameters. A $\pi$ equivalent circuit model is applied for modeling of the SISL inductor and new double-sided SISL (DSISL) inductor, and the accurate empirical expression of inductance L$ , peak quality factor Q_{\mathrm {max}} , and self-resonance frequency are given. The typical relative error of each expression is less than 8%. Finally, a new DSISL inductor with patterned substrate is proposed, which can significantly improve the quality factor up to 40%. Simulation and measurement results show good agreement. [ABSTRACT FROM PUBLISHER]

The article presents information related to paper submission, submission format, and open access for the author of the periodical.

These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal. [ABSTRACT FROM AUTHOR]

This paper presents an integral-equation formulation specialized for the analysis of capacitive waveguide circuits, which include arbitrarily shaped conducting and homogeneous magnetic/dielectric objects. The technique benefits from the symmetry of the structure by formulating a 2-D scattering problem with oblique angle of incidence, combined with the use of the parallel-plate Green’s functions. As practical applications, the paper proposes novel low-pass filter designs loaded or coated with dielectric and magnetic homogeneous materials. If the filter is properly designed, the use of these materials could improve the filter response, selectivity, or out-of-band performance, and power-handling capabilities. Some novel filter design implementations, showing these kinds of benefits, are presented for the first time in this paper. For validation, a commercial full-wave simulator is employed, showing the validity, accuracy, and computational efficiency of the novel software tool. [ABSTRACT FROM PUBLISHER]

Editorial. Discusses the changes in the publication of papers in the "IEEE Transactions on Microwave Theory and Techniques". Criteria for publication; Decision not to accept short papers.

This Mini-Special Issue of the IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES (TMTT) is devoted to the 2019 Asia-Pacific Microwave Conference (APMC 2019), Singapore, December 10–13, 2019. APMC is one of the premier international conferences in the microwave community. The conference brought in a unique mix of high-quality keynote, invited, and contributed papers by world-class speakers from academia and industry, providing an opportunity for microwave family members to exchange their visions, insights, challenges, and progress in microwaves. It received a total submission of 1064 papers covering microwave to terahertz spectrum with a variety of applications by the authors from 56 countries/regions and finally accepted 720 papers after careful and rigorous peer review. The conference consisted of 71 technical oral and poster sessions from 53 technical tracks, eight workshops/short courses, 29 invited talks, and two plenary talks. In particular, 17 special sessions are convened by session organizers to discuss emerging technologies. [ABSTRACT FROM AUTHOR]