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In this letter, a novel dual-band coupler made of only three coupled microstrip-slotline (CMSL) sections is proposed to achieve a tight coupling with a high band ratio in a small size. A desired dual-band operation can be obtained by proper design of the coupling levels of the CMSL sections. Explicit design equations of the proposed coupler were derived by the method of even- and odd-mode excitations, and the characteristics of the CMSL were studied. For demonstration, a 3-dB dual-band CMSL coupler operating at 1 and 3 GHz is designed, fabricated, and measured. The proposed coupler has the advantages of small size, tight coupling, and high isolation.

An approach for implementing compact multichannel substrate integrated waveguide (SIW) diplexers is presented based on orthogonal dual modes and split-type multiband responses. By coupling multiple TE $_{101}$ -based bandstop single-mode cavities to TE $_{201}$ /TE $_{102}$ -based bandpass dual-mode cavities, one or both of the two passbands constructed by TE $_{201}$ and TE $_{102}$ modes could be split into multiple subpassbands. Additionally, by arranging two output ports at central positions of adjacent sides of the last cascaded dual-mode cavity, isolations between these two output ports can be achieved and then further improved by tiny offset locations benefitting from the orthogonal characteristics of TE $_{201}$ and TE $_{102}$ modes. Three experimental prototypes, including a 1 + 2 type tri-channel SIW diplexer, a 3 + 1 type quad-channel SIW diplexer, and a 2 + 2 type quad-channel SIW diplexer, are synthesized, designed, fabricated, and measured to demonstrate and validate the proposed mode-collaborative design concepts.

Miniaturized substrate integrated waveguide (SIW) diplexers with widely separated channel passbands using common half-mode dual-mode SIW junction-cavities are presented and developed for 5G sub-6 GHz communications and wireless systems. With this kind of half-mode dual-mode junction-cavities to eliminate the conventional T-junctions and also to produce one transmission pole in each channel passband, significant circuit miniaturization can be achieved for SIW diplexers. Additionally, by exploiting the first dual modes in the half-mode SIW junction- cavities, flexibly allocated fractional bandwidths (FBWs) for the two channels can be realized through FBW design graphs, large frequency ratios can also be accommodated, which is difficult to implement using the whole-mode SIW cavity scheme due to spurious problems. Two compact SIW diplexers with large frequency ratios are synthesized, designed, fabricated, and measured for demonstration, including a third-order direct-coupled prototype centered at 3.5 and 5.0 GHz with a frequency ratio of 1.43 based on the TE₁₀₁/TE₃₀₁ half-mode dual-mode junction-cavity and a fourth-order cross-coupled prototype centered at 3.5 and 5.5 GHz with a frequency ratio of 1.57 based on the TE₁₀₁/TE₁₀₂ half-mode dual-mode junction-cavity.

Radio frequency (RF), microwave, and millimeter-wave (mmW) multiport interferometric receivers present a competitive solution for the front-end reception of low-power multistandard and multifunction wireless applications. The systematic generation of rectified waves in a conventional direct-conversion interferometric receiver is highly related to temporal and power changes and the number of subsignals in the frequency band of interest. It can cause the receiver to saturate and, thus, requires auxiliary power-hungry tunable amplifiers and a data converter for compensation. This work presents a heterodyne detection in an RF/microwave interferometric receiver, the first of its kind, which separates the desired frequency signals from the rectified wave components with two output ports through a frequency offset. This architecture also makes use of the field-effect transistor (FET)-based power detectors to combine the received and reference signals, which reduces a theoretical multiport junction loss of 6 dB to 3 dB. In this way, the proposed receiver is set to support the development of an ultralow-power concurrent dual-band wireless system using a single wave-correlator circuit. A mathematical model of the proposed system is derived and subsequently prototyped using off-the-shelf components to evaluate its carrier-to-noise power ratio (CNR) and error vector magnitude (EVM) performances, which can be extended for integrated circuits (ICs) implementation, such as CMOS and III–V ICs. The power detectors only require a bias voltage at gate terminals with zero direct current (dc) power consumption for optimum voltage responsivity and CNR performances. The demodulation of various modulated digital signals, including QPSK, QAM-16, QAM-32, and QAM-64, has been successfully demonstrated in the 24- and 28-GHz mmW frequency bands at 4 MSps of the symbol rate with a maximum EVM of 11.43% root-mean-square (rms) free from any postprocessing linearization and calibration.

This article presents a compact, low-power, yet efficient wireless sensing platform to detect the angular displacement of an object with a reoriented complementary split-ring resonator (RCSRR). This RCSRR sensor belongs to the CSRR family, consisting of a 90° feedline on the stator and slots on the rotor. The reflected signal of the sensor experiences a monolithic phase response to the angular displacement because of its asymmetricity. In the platform, the sensor acts as a variable load of the multiport interferometer. The multiport converts the reflected signal into dc voltage readouts representing the real and imaginary parts of the phase of the reflection coefficient. Moreover, this platform operates at a fixed frequency (i.e., 2.4 GHz), and it requires only a biasing power as low as −30 dBm. This platform prevents ponderous system architecture and power consumption. This innovative wireless sensing platform has been designed, implemented, and tested. The experimental results show good agreement with their theoretical counterparts, and the standard deviation of angular displacement uncertainty is only $10^\prime $ .

In this work, we propose, develop, and demonstrate a fundamental and comprehensive theoretical foundation for the first time to formulate and devise known and unknown reciprocal and/or nonreciprocal ferrite components with arbitrarily concurrent multimode features based on the substrate-integrated waveguide (SIW) technology. To achieve such a universal design, a nonreciprocal unit cell (NRUC) is first defined and characterized. Then, an approach is proposed and investigated to deploy a sufficient number of NRUCs next to each other as a kernel multimode SIW topology. The kernel configuration transforms the incident guided-wave into several separate segments, propagating in parallels independently and along each NRUC, which can be manipulated separately. This methodology grants a general solution to forge ferrite components in a multimode configuration, discussed in detail to corroborate the proposed generalized theory. Finally, two multimode components are studied and demonstrated for the first time as application examples for the proposed theory. Namely, a dual-mode circulator and a triple-mode gyrator are prototyped, fabricated, and measured, exhibiting an excellent agreement with simulation results that effectively validate the presented theoretical foundation in this work.

When a fluid-filled cube rotating rapidly about an axis passing through two opposite vertices is subjected to harmonic modulations of its rotation rate (librations) at a modulation frequency that is $2/\sqrt {3}$ times the mean rotation frequency, all walls of the cube have critical reflection slopes. As such, all inertial wave beams emitted from edges and vertices of the cube in response to the librations are trapped in thin oscillatory boundary layers for forcing amplitudes (Rossby numbers) below a critical value which depends on the Ekman number (ratio of rotation to viscous time scales). How the resulting oscillatory boundary layer flow, referred to as a boundary-confined wave, depends on Ekman and Rossby numbers is examined in detail over several decades. Of particular interest is how the mean flow grows with increasing forcing amplitude, leading to instability resulting from nonlinear interactions between the mean flow and waves in the oscillatory boundary layers, injecting intense small-scale structures throughout the cube.

It all started with a spark. Let us rewind back to 1887, in Germany. The days were getting cooler in the garden of the Technische Hochschule in Karlsruhe as Heinrich Rudolf Hertz was setting up the first-ever far-field wireless power transmission with increasingly more power [1]. He was striving to demonstrate the wireless nature of electromagnetic waves and propagation. Moreover, as no high-frequency (nearly 100 MHz) voltmeter was available at that time for his experiment, he had to transmit enough power to generate a spark-hundreds of volts!-at the receiver to validate the famous theory of James Clerk Maxwell.

Two-dimensional (2D) transition metal dichalcogenide (TMD) has emerged as an effective optoelectronics material due to its novel optical properties. Understanding the role of defects in exciton kinetics is crucial for achieving high-efficiency TMD devices. Here, we observe defects induced anomalous power dependence exciton dynamics and spatial distribution in hexagonal heterogeneous WS2. With transient absorption microscopy study, we illustrate that these phenomena originate from the competition between radiative and defect-related non-radiative decays. To understand the physics behind this, a decay model is introduced with two defect-related channels, which demonstrates that more excitons decay through non-radiative channels in the dark region than the bright region. Our work reveals the mechanisms of anomalous exciton kinetics by defects and is instrumental for understanding and exploiting excitonic states in emerging 2D semiconductors.

Substrate-integrated waveguide (SIW) filtering crossovers featuring wide-stopband characteristics and flexibly allocated center frequencies (CFs) and bandwidths (BWs) for two intersecting channels are presented and studied. The development is devised upon a scheme of an over-mode dual-mode substrate-integrated rectangular cavity (SIRC) coupled with multiple single-mode cavities. First, by exploiting the orthogonal TE102 and TE201 modes in the dual-mode SIRC, cross transmission and acceptable isolation can be obtained and implemented for the dual channels. Furthermore, by controlling the resonant frequencies and mutual couplings of the coupled cavities accordingly, especially the over-mode dual-mode SIRC, both the CFs and BWs of the two channels can be allocated flexibly. In addition, by incorporating three kinds of intrinsic spurious-mode suppression techniques, namely, the harmonic staggered technique, centered coupling windows, and offset centered feeding ports, wide-stopband characteristics can be achieved intrinsically and uniquely. Four practical design examples, including fifth-order direct-coupled and fifth-order cross-coupled SIW filtering crossovers with identical channel CFs and BWs, a third-order crossover with the same channel CFs but different channel BWs and another third-order case with different channel CFs but the same channel BWs are synthesized, designed, fabricated, and tested to demonstrate and validate the proposed collaborative design concepts.

A distinct usage of the conventional multiport architecture is introduced in this work to explore the compendious scheme of a concurrent dual-band interferometric receiver. Dual RF signals at individual frequency channels are received simultaneously, and only a single low-power local oscillator (LO) source is deployed for frequency translation or conversion to the same intermediate frequency (IF) band. Although these signals are spectrally overlapped, they can be extracted with a simple and efficient algorithm with good channel-to-channel isolations. Compared to the conventional multiport configuration, the power detectors are replaced by analog-to-digital converters (ADCs) to process the signals in this proposed scheme. The underlying physics of the concurrent receiving operation is explained and derived analytically. Some experiments are also presented to investigate various performance indexes, including signal linearity, noise behavior, interchannel interference, and so forth. Lastly, multiple $M$ -quadratic-amplitude modulation (QAM) signals are applied to evaluate the communication behavior of the proposed receiver architecture. Distortions due to frequency drift, channel imbalance, and in-phase and quadrature (IQ) imbalance are studied, and bit-error-rates (BER) are measured and compared with their theoretical counterparts. All obtained results confirm that the proposed interferometric receiver provides good communication performances.

This work proposes to enlarge the maximum readout distance of battery-free harmonic transponders through a careful Schottky diode selection and a consideration of low-temperature operations. Diode SMS7621 is identified to deliver lower conversion loss (CL) of harmonic transponders based on a diode selection guide. Moreover, an analytical method for studying temperature effects on the transponder CL performance is introduced and derived with satisfactory accuracy. A diplexer inserted in the harmonic transponder design can help reduce the antenna number. To mitigate matching difficulties at both fundamental and second-harmonic frequencies, a third-order diplexer is developed to enhance its bandwidth performance. Experimental verification has shown that low-temperature operations can effectively reduce the CL of the SMS7630-based harmonic transponder, thus increasing its readout distance. Specifically, its maximum readout distance at −40 °C has increased by more than 10%, from 6.4 to 7.1 m, compared with that at +40 °C. A complete harmonic transponder based on SMS7621, with dimensions of 85 mm $\times45$ mm has reached a maximum readout distance of 8 m when the fundamental frequency is 3.5 GHz.

A scalable planar 2-D active array antenna configuration that can realize amplified radiation through co-existing active devices is proposed, studied, and demonstrated in this work. The input and output of these amplifying active devices are directly integrated with the feed network and array elements, respectively, thereby eliminating the matching networks typically required in an amplifier circuit. A comprehensive analysis of the rectangular patch antenna (RPA) performance with different feeding techniques is initially analyzed and the choice of nonradiating edge feed RPA as array elements is justified for not only realizing the maximum radiation efficiency but also facilitating the direct active device integration. Subsequently, a physical arrangement of these array elements is devised to reduce cross-polarization. The design of $4\times {2}$ active array antenna unit cell operating at 5.8 GHz is then discussed through extensive analysis of active devices, optimization procedure, potential excitation signal control, and influence of faulty transistors. From simulations, this active array scheme has realized a higher matching bandwidth and exhibited an amplifier gain of around 13.6 dB, compared with its passive counterpart. Eventually, these unit cells are integrated through an equal power hybrid feed network for realizing an $8\times {8}$ active array antenna configuration that is fabricated and measured. The measured results of the experimental prototype match reasonably well with the simulation results, thereby confirming the proposed integration technique. The resulting paralleled configuration promises efficient handling of greater powers, making them suitable for high-power applications.

A fluid-filled cube rotating about an axis passing through the midpoints of opposite edges is subjected to small librations (i.e. modulation of the mean rotation). Low viscosity regimes, with Ekman number as small as $10^{-8}$ and equally small relative forcing amplitude, are explored numerically. The full inertial range of forcing frequencies, from 0 to twice the mean rotation rate are considered. The response flows are dominated by inertial wavebeams emitted from edges and/or vertices, depending on the forcing frequency. How these reflect on the cube's walls and focus onto edges and vertices lead to intricate patterns. Most of the results can be reconciled using linear inviscid ray-tracing theory with careful attention to wavebeam emissions and reflections. However, even at the low Ekman number and relative forcing amplitude considered, other effects are discernible which are not captured by ray tracing. These include a symmetry breaking due to viscous effects and a progressive wave, retrograde to the mean rotation and localized in the boundary layers of the cube, due to nonlinear effects and the librational forcing.

This article presents a novel class of dual-mode substrate-integrated waveguide (SIW) bandpass filters exploiting perturbed SIW rectangular cavities. By introducing metallized via-holes along the central line of an SIW rectangular cavity, the resonant frequency of TE101 mode can be shifted close to that of TE201 mode, thus creating a dual-mode resonator. This structure implements a doublet, which provides two poles and one or two transmission zeros (TZs). The pass bandwidth, spurious-free bandwidth, and positions of the TZs can be fully controlled by modifying the length of the perturbation, the side ratio of the rectangular cavity, and the offset of the input/output ports, respectively. Eight two-pole SIW filters are designed and investigated to demonstrate the high design flexibility. Moreover, a four-pole SIW filter with the asymmetric response and a five-pole SIW filter with quasi-elliptic response are designed, fabricated, and measured to describe the extension of the proposed approach to higher order filters.

This letter presents a novel class of compact dual-mode bandpass filters based on half-mode substrate-integrated waveguide (HMSIW) cavities. By using both TE102 and TE301 modes of the HMSIW rectangular cavity as resonant modes and TE101 mode as nonresonating mode, a novel HMSIW doublet with two poles and two transmission zeros (TZs) is implemented. The TZs can be located at one side or both sides of the passband. Therefore, flexible responses can be obtained. A two-pole HMSIW filter with asymmetric response and a four-pole HMSIW filter with quasi-elliptic response have been designed, fabricated, and measured, to demonstrate and verify the proposed structure. Compared with substrate-integrated waveguide (SIW) counterparts, the dual-mode HMSIW filters have the advantage of smaller size.

In this work, we present a comprehensive analysis of port impedance effects on a signal coupled across two-port networks, derive an equation to evaluate the impedances for a specified coupling, and demonstrate two beam-shaping active array antenna prototypes to validate the theory. In this context, the generalized S-parameters are theoretically studied and verified through an example. Subsequently, a closed-form equation is derived to accurately evaluate the port impedances that enable the achievement of a desired magnitude and phase of the signal coupling across the two-port network. The meaningfulness of all the potential results and the additional capabilities of derived equations are then discussed. With this understanding, a general modeling procedure is formulated to achieve the simultaneous amplification and phase shifting only through the active devices, without resorting to any additional passive circuitry. As a proof of concept, two $1 \times 5$ active array antenna prototypes are developed and fabricated at 5 GHz: one for broadside radiation with a sidelobe level of less than −20 dB requirement, and the other for flat-top radiation beam between −10° and 30°. They are integrated with a $1 \times 5$ Wilkinson power divider that is designed for radiation pattern measurements, and the corresponding results agree reasonably well with the simulated counterparts and theory, thereby proving the developed concept. Such solutions demonstrate the inherent advantages of being low-loss, compact, and efficient, which are essential for the next generation of wireless systems.

International audience; Properties of polyhydroxycompounds, such as sugars and polyols, which are used to stabilize various pharmaceuticals and biological objects during freezing, desiccation, and storage, depend on water content. In this investigation, glycerol-water mixtures containing 40 to 0 wt% water are studied by FTIR spectroscopy and molecular dynamics simulation. The HOH bending (approx. 1640 cm−1) band in the FTIR spectra is essentially independent of water content in the range of 0 to approx. 12 wt% water, whereas a red shift to lower wavenumbers is observed as water content increases beyond 12 wt%. Water clustering patterns, which obtained from MD simulations, show a gradual decrease of unclustered water molecules at a higher water concentration, with the corresponding increase in small (3–4 water molecules) water clusters. Large water clusters (>30 molecules) appear at 9 to 12 wt% water; at 25 wt% water, smaller water clusters disappear, with essentially all water molecules belonging to continuous water domain. The water clustering and hydrogen bonding patterns are discussed in view of fundamental physical chemical processes including proton transfer, water catalysis of chemical reactions, and freezing behavior.

This article introduces two-way broadband air-filled substrate integrated waveguide (AFSIW) isolated power dividers/combiners based on surface mounted absorbing materials. The proposed structures take advantage of the AFSIW multilayer feature. The absorber implementation is found highly tolerant of variations in dimensions and positioning. Three different power dividers/combiners topologies are analyzed theoretically, simulatively, and experimentally. The measurement results validate the broadband responses of the fabricated Ka-band demonstrators. The proposed power dividers/combiners are intended to exploit high-power AFSIW system on substrate (up to few hundred watts).

A generalized mesh-network equivalent model for a microstrip rectangular patch antenna (RPA), which is simple yet efficient is proposed, studied, and demonstrated in this article. The mesh-network equivalent model is established through the segmentation of RPA width and radiation parameters into $M$ sections, as well as the segmentation of RPA length into $N$ sections. A general design procedure to realize the mesh-network equivalent model is addressed and described for any number of RPA segmentations, as desired by specific applications. Subsequently, the proposed mesh-network equivalent model is used to accurately evaluate the input impedance responses at various feed positions along the length of RPA. In addition, to include the effects of a slot etched inside the RPA geometry, a generalized microstrip coupled line equivalent model is proposed, analyzed, and discussed in detail. Eventually, the microstrip coupled line model in conjunction with the proposed mesh-network equivalent model can accurately estimate the input impedance response of a slotted RPA, and has been verified for RPA with center slot, edge slot, and multiple slots as examples in this work. Two cases with multiport excitation of RPA are also analyzed and presented as a part of this work. For demonstration purposes, all these prototypes are designed, fabricated, and measured at 28 GHz. The proposed equivalent model-based results are validated by measured and simulated counterparts. Furthermore, the extension of the proposed mesh-network model to accommodate slots of smaller size inside RPA, RPA loaded with via, inverted-F antenna, and multimode operation are demonstrated and discussed through a comparison between mesh-network modeling results and simulation results.

Emerging and disruptive information and communication technology (ICT) RaD is principally driven by the growing needs of signal generation, collection, transmission, processing, and storage as well as the applications of massive data sets in our fast-evolving information society. Such data set-related operations call for fundamental wireless- and wireline-empowered capabilities as well as many others. The next breed in ICT is closely related to, and enabled on a large scale by, the much-publicized 5G and future heterogeneous wireless systems [1]-[4], which in the future will connect everyone and everything at different speeds for various functions and services. This will propel us toward a much more connected, smarter world.