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A novel wideband dual‐band bandstop filter with multi‐transmission zeros and multi‐reflection zeros is presented. It consists of two pairs of symmetric open‐ended coupled lines at two sides and (2N − 1) pairs of coupled‐line sections with an open‐circuited stub in the middle. Through even‐ and odd‐mode analyses, general simultaneous equations for characteristic impedances are derived with the proposed algorithm. By suitably selecting all the design parameters, the proposed topology could not only provide a controllable equal‐ripple response in the passband but also control the stopband rejection, bandwidth (BW), and centre frequency ratio in the stopband flexibly. For verification, one prototype circuit is finally fabricated and measured in the experiment. Good agreement between the measured and simulated results is attained so as to successfully validate the correctness of the proposed design method. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of coplanar waveguide (CPW) structures loaded with symmetric circular and polygonal split-ring resonators (SRRs) for microwave and RF applications, leveraging their unique electromagnetic properties. These properties make them suitable for metamaterials, sensors, filters, resonators, antennas, and communication systems. The objectives of this study are to analyze the impact of different SRR shapes on the transmission characteristics of CPWs and to explore their potential for realizing compact and efficient microwave components. The CPW-SRR structures are fabricated on a dielectric substrate, and their transmission properties and spectrogram are experimentally characterized in the frequency range of 4 GHz to 10 GHz with the rotation angles of the SRR gap. The simulation results demonstrate that the resonant frequencies and magnitude of the transmission coefficient of the CPW-SRR structures are influenced by the geometry of the SRR shapes and the rotation angles of the SRR gap, with certain shapes exhibiting enhanced performance characteristics compared to others. Moreover, the symmetric circular and polygonal SRRs offer design flexibility and enable the realization of miniaturized microwave components with improved performance metrics. Overall, this study provides valuable insights into the design and optimization of CPW-based microwave circuits utilizing symmetric SRR shapes, paving the way for advancements in the miniaturization and integration of RF systems. [ABSTRACT FROM AUTHOR]

In this article, a 7–11.5 GHz 2‐W power amplifier (PA) based on cascode transistors is developed using 0.15‐µm GaAs pHEMT. This design facilitates impedance matching in the broadband range by using a cascode structure. A double‐cascode transistors structure is used as a unit cell to combine radio frequency voltage swings to achieve a broad bandwidth (BW). In addition, power synthesis techniques are used to achieve higher power output. Ultimately, based on the above two structures, a four‐way power‐synthesized PA is designed. The fabricated PA shows a peak power of 33.8 dBm at 9 GHz with a power‐added efficiency (PAE) of 43%. The output power is higher than 32 dBm at frequencies from 6 to 11.5 GHz with a PAE of more than 25%. The fractional 3‐dB output power BW is 80%. The chip area is 3.6 × 1.8 mm2, including the input and output test pads. [ABSTRACT FROM AUTHOR]

Geometry scaling of microwave circuits is an essential but challenging task. In particular, the employment of a given passive structure in a different application area often requires re-adjustment of the operating frequencies/bands while maintaining top performance. Achieving this necessitates the utilization of numerical optimization methods. Nonetheless, if the intended frequencies are distant from the ones at the starting point, local search procedures tend to fail, whereas global search algorithms are computationally expensive. As recently demonstrated, a combination of large-scale concurrent geometry parameter scaling with intermittent local tuning allows for dependable re-design of high-frequency circuits at low CPU costs. Unfortunately, the procedure is only applicable to single-band structures due to synchronized modifications of all operating bands under scaling. This article discusses a novel procedure that leverages a similar overall concept, but allows for independent control of all center frequencies. To achieve this goal, an automated decision-making procedure is developed in which a set of orthogonal scaling directions are determined based on their effect on individual circuit bands, and using auxiliary optimization sub-problems. The scaling range is then automatically computed by solving an appropriately-defined least-square design relocation problem. The methodology introduced in the work is illustrated using two planar passive devices. In both cases, wide-range operating frequency re-design has been demonstrated and favorably compared to conventional gradient-based tuning. Furthermore, the presented procedure has been shown to be computationally efficient. It is also easy to implement and integrate with a variety of gradient-based optimization procedures of a descent type. [ABSTRACT FROM AUTHOR]

Metamaterial components and antennas are based on the general understanding that an artificial structure composed of adequately designed and manufactured elementary cells or arrays has unusual resonance and propagation properties. Metamaterials exhibit equivalent values of the dielectric constant and magnetic permeability that are both negative simultaneously, in contrast with ordinary materials. Single elements, periodic, or quasi-periodic configurations can be suitable for a metamaterial response. In this paper, equivalent circuits for microwave propagation and resonance are compared, deriving a lumped element modeling complementary to those already available in the literature, with a particular focus on planar resonating devices and calculating the effective value for the dielectric constant and the magnetic permeability directly from experimental findings using the impedance (Z-parameters) notation. [ABSTRACT FROM AUTHOR]

A 90° hybrid coupler operating at a central frequency of 5.40 GHz is introduced, offering high-performance characteristics with compact dimensions of 616.65 mm² (33.3 mm × 18.5 mm). These features are achieved while maintaining a design that makes it easy to produce. The unique aspect of this microstrip FR4 substrate-based design is the consistent S-parameters, which remain steady despite changes in structural dimensions, thereby making it adaptable to fabrication variations. The reported S-parameters measured in 5.4 GHz are as follows:|S11|= –29.46 dB,|S21|= –4.11 dB,|S31|= –3.96 dB, and|S41|= –21.23 dB. This hybrid coupler operates over a bandwidth of 0.8 GHz (16%), demonstrating remarkable performance within this spectrum. In addition to its design, the coupler exhibits robust resilience against changes in substrate parameters and structural dimensions, ensuring reliability during the fabrication process. Following thorough simulation studies, a physical prototype of the coupler was constructed and subjected to laboratory measurements. The experimental results align closely with the simulation data, validating the accuracy and predictability of the design. In comparison with other studies and designs documented in the literature, this compact, high-performance 90° hybrid coupler exhibits clear advantages in terms of size, isolation, phase deviation, and structural complexity. Therefore, the benefits and applicability of this presented structure in the context of microwave circuits and systems are underscored. It's noteworthy to mention that the central frequency of 5.4 GHz falls within the sub-6 GHz 5G band range. [ABSTRACT FROM AUTHOR]

A miniaturised high‐isolation K‐/Ka‐band diplexer with exceeding adjacent channels using 3D antarafacial channel integration and vertical‐quasi‐coaxial‐based matching network is proposed. For smaller size, lower loss and lower channel interference, the high‐order low‐pass filter for the K‐band channel and the four‐line‐interdigital‐coupled wideband bandpass filter for the Ka‐band channel are respectively designed on two low‐loss glass‐based substrates, and these two substrates are integrated on the two antarafacial surface of the mounting board. The vertical‐quasi‐coaxial (VQC) embedded in the mounting board is not only used as three‐dimensional (3D) interconnection of the two antarafacial channels but also designed as the constituent part of the matching/isolation network, and this can effectively decrease the impedance traction caused by the Ka‐band filter for the K‐band channel of the diplexer. In addition, four transmission zeros of the K‐band filter are designed at the whole passband of the Ka‐band channel to improve the isolation to the K‐band channel for guaranteeing the performance of the diplexer at the Ka‐band channel. Furthermore, working principle, design method and test solution of this proposed K‐/Ka‐band diplexer are well illustrated, and the high‐isolation (>40 dB) in very adjacent wideband channels at K‐band (18–23.5 GHz) and Ka‐band (25.8–31.6 GHz) is achieved within a tiny size of 9 × 4 × 0.87 mm. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid technique‐based compact narrow band stop filter design for broadband applications. It provides the rejection of 60 dB at the centre frequency of 2.25 GHz without any stop band harmonics over the required frequency band of operation, i.e. 1–10 GHz. This filter is highly appropriated for the rejection of undesired bands for RADAR, electronic warfare, and military communications. [ABSTRACT FROM AUTHOR]

High‐throughput satellite (HTS) is an ideal way to realize cross‐regional massive, multifaceted digital exchange services, and it requires a signal processing module that can be massively multiplexed and has high flexibility. Due to the limitations of the frequency characteristics, microwave integrated circuits are difficult to meet this requirement. One solution to this problem is photonic integrated circuits (PICs). However, full‐size PIC satellite payloads containing main optoelectronic components are extremely challenging to implement on monolithic or hybrid integrated platforms. Here, the study demonstrates a hybrid integrated on‐chip microwave‐photonic satellite repeater with large‐scale multiplexing potential and high flexibility. This is a demonstration of a hybrid integration of a InP/Si3N4 external cavity laser, arrayed InP modulators, and semiconductor optical amplifiers (SOAs), as well as multifunctional Si3N4 signal processors, to fulfill a 1 × 4 Ka‐band repeater module with on‐chip arrayed frequency down‐conversion and outstanding narrowband photonic channelization. When combined with the full‐chip photonic RF repeater, broadband, highly integrated, and cost‐effective communications satellite payloads will become realizable more quickly in the near future. [ABSTRACT FROM AUTHOR]

We have proposed and experimentally verified a local method of microwave resonant spectroscopy of semiconductors. The microwave circuit of the spectrometer based on the Cascade Microtech probe station is equipped with a coaxial resonator of special geometry. As result, the measurement accuracy of the previously developed volt-impedance spectroscopy method was greatly increased. A technique for spectrometer calibration and resonant measurements of the complex impedance of the probe-sample system has been developed. We have measured the impedance of test structures with Schottky contacts of 30–60 μm in diameter on a single-crystal GaAs wafer at several discrete frequencies in the range of 50–250 MHz. The nontrivial resistive properties of the structures are studied, which consist of the excess resistance that is 1–2 orders higher than the spreading resistance for the alternating current in the unperturbed region of the semiconductor. The discovered effect is presumably associated with the a.c. charge modulation on deep levels of the semiconductor. A model calculation of the impedance spectrum has been performed, which demonstrates a good agreement with the experimental spectra. [ABSTRACT FROM AUTHOR]

Integration of planar circuits been considered a credible technique for low-cost mass production of microwave and millimeter-wave circuits and systems. For the first time, in this research a dual-post band-pass filter is designed and simulated in a three-layer substrate integrated gap groove waveguide (SIGGW) for 5G millimeter-wave frequency band applications. The filter includes 12 posts ( 6 × 2 ). Also, the structure facilitates to use resonant posts and so we can design the posts to add a transmission zero in lower rejection band. The design theory algorithm and its limitations are investigated based on the circuit model of filter. The results shows that FBW of 5% and a lower band transmission zero for the proposed 12 posts filter. Also, the results are verified by simulation using CST. According to the results, the proposed filter is a good option for Ka-band applications and can be used as the building block for suppressing the LO leakage that is commonly used for up-converting the 5G signal to Ka band. [ABSTRACT FROM AUTHOR]

Superconducting microwave resonators are crucial elements of microwave circuits, offering a wide range of potential applications in modern science and technology. While conventional low-T c superconductors are mainly employed, high-T c cuprates could offer enhanced temperature and magnetic field operating ranges. Here, we report the realization of YBa 2 Cu 3 O 7 - δ superconducting coplanar waveguide resonators, and demonstrate a continuous evolution from a lossy undercoupled regime, to a lossless overcoupled regime by adjusting the device geometry, in good agreement with circuit model theory. A high-quality factor resonator was then used to perform electron spin resonance measurements on a molecular spin ensemble across a temperature range spanning two decades. We observe spin-cavity hybridization indicating coherent coupling between the microwave field and the spins in a highly cooperative regime. The temperature dependence of the Rabi splitting and the spin relaxation time point toward an antiferromagnetic coupling of the spins below 2 K. Our findings indicate that high-Tc superconducting resonators hold great promise for the development of functional circuits. Additionally, they suggest novel approaches for achieving hybrid quantum systems based on high-T c superconductors and for conducting electron spin resonance measurements over a wide range of magnetic fields and temperatures. [ABSTRACT FROM AUTHOR]

A microwave transmitter/receiver using the low-temperature co-fired ceramic substrate and ball grid array packaging demonstrates superior properties, including high integration, miniaturization, and high electromagnetic shielding. However, it holds limitations of inadequate hermeticity (that is, gas or moist impermeability), high cost, and low reproducibility. In this work, we aim to overcome these difficulties by introducing a new packing technique. The packaging utilizes an electroless plated Ni/Pd/Au surface, resulting in a significant enhancement of the packaging hermeticity by orders of magnitude, approaching the level of <5 × 10−9 Pa·m3/s. Both Sn63Pb37 and Au80Sn20 solder alloys demonstrate exceptional solderability, attributed to Pd atoms diffusing to the Au layer during soldering at 310 °C. A reliability test of the packaging shows that the shear strength of the solder balls drops after thermal shocks but negligibly affects the hermeticity of the packaging. Furthermore, a meticulously designed internal vertical interconnect structure and I/O interconnections were engineered in the ball grid array packaging, showcasing excellent transmission characteristics within the 10–40 GHz frequency range while ensuring effective isolation between ports. [ABSTRACT FROM AUTHOR]

A new design of single‐layered balanced filtering crossover with high selectivity based on square patch resonator is proposed. Originated from the degenerate modes, that is, TM12 and TM21 on square patch resonators, the feasibility of intrinsic common‐mode (CM) suppression and channel isolation is conceived. For demonstration, a first‐order balanced crossover prototype is designed. Afterwards, to enhance selectivity, a square patch resonator is subtly divided into two identical parts and then introduced into the prototype. Hence, a balanced filtering crossover with a fifth‐order Chebyshev response is formed. Furthermore, stubs are deployed between adjacent patch resonators to introduce mixed couplings. Thus, two controllable transmission zeros are obtained, and better out‐of‐band suppression is achieved. Ultimately, the proposed crossover is fabricated and measured. High performance in terms of differential‐mode filtering response, in‐band CM suppression and channel isolation demonstrates the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Superconducting microwave resonators are crucial elements of microwave circuits, offering a wide range of potential applications in modern science and technology. While conventional low-T c superconductors are mainly employed, high-T c cuprates could offer enhanced temperature and magnetic field operating ranges. Here, we report the realization of YBa 2 Cu 3 O 7 - δ superconducting coplanar waveguide resonators, and demonstrate a continuous evolution from a lossy undercoupled regime, to a lossless overcoupled regime by adjusting the device geometry, in good agreement with circuit model theory. A high-quality factor resonator was then used to perform electron spin resonance measurements on a molecular spin ensemble across a temperature range spanning two decades. We observe spin-cavity hybridization indicating coherent coupling between the microwave field and the spins in a highly cooperative regime. The temperature dependence of the Rabi splitting and the spin relaxation time point toward an antiferromagnetic coupling of the spins below 2 K. Our findings indicate that high-Tc superconducting resonators hold great promise for the development of functional circuits. Additionally, they suggest novel approaches for achieving hybrid quantum systems based on high-T c superconductors and for conducting electron spin resonance measurements over a wide range of magnetic fields and temperatures. [ABSTRACT FROM AUTHOR]

Flexible and stretchable materials have attracted significant interest in wearable electronics and bioengineering fields. Recent developments also incorporate embedded microwave circuits and systems with engineered flexible materials that operate over a broad frequency range (≈1–100 GHz). Herein, a simple flip‐chip technique is used to evaluate frequency‐dependent electromagnetic properties of flexible materials and applied to evaluate engineered microwave absorbers based on self‐biased barium hexaferrite composites. On‐wafer error correction and de‐embedding techniques are applied to determine broadband electromagnetic properties of the material‐loaded transmission lines by placing the materials on top of coplanar waveguide transmission lines. Finite‐element simulations along with broadband measurements were employed to estimate the electromagnetic material properties. To demonstrate, flexible polydimethylsiloxane (PDMS) composites are fabricated with barium hexaferrite nanoparticles and complex permittivity and permeability of the composites are quantified under zero magnetic field bias up to 110 GHz. Frequency‐dependent composite permeability is fitted to models describing the ferromagnetic resonance of the self‐biased barium hexaferrite nanoparticles in polydimethylsiloxane, and constituent nanoparticle properties are estimated using the Maxwell–Garnett mixing model. This study paves the way to exploit a wide range of engineered materials in flexible, wearable, and biomedical electronics applications and presents a convenient methodology to extract important broadband electromagnetic properties of nanoparticles for customized electromagnetic applications. [ABSTRACT FROM AUTHOR]

We outline calibrated measurements of the microwave reflection coefficient from the tunnel junction of an ultra-high vacuum low temperature scanning tunneling microscope. The microwave circuit design is described in detail, including an interferometer for an enhanced signal-to-noise ratio and a demodulation scheme for lock-in detection. A quantitative, in situ procedure for impedance calibration based on the numerical three-error-term model is presented. Our procedure exploits the response of the microwave reflection signal due to the change of the tunneling conductance caused by sub-nm variation of the tunneling distance. Experimental calibration is achieved by a least-squares numerical fit of simultaneously measured conductance and microwave reflection retraction curves at finite conductance. Our method paves the way for nanoscale microscopy and spectroscopy of dielectric surface properties at GHz frequencies and cryogenic temperatures. This opens a promising pathway even for dielectric fingerprinting at the single molecule limit. [ABSTRACT FROM AUTHOR]

Modern microwave devices are designed to fulfill stringent requirements pertaining to electrical performance, which requires, among others, a meticulous tuning of their geometry parameters. When moving up in frequency, physical dimensions of passive microwave circuits become smaller, making the system performance increasingly susceptible to manufacturing tolerances. In particular, inherent inaccuracy of fabrication processes affect the fundamental operating parameters, such as center frequency or bandwidth, which is especially troublesome for narrow-band structures, including notch filters. The ability to quantify the effects of tolerances, and—even more—to account for these in the design process, are instrumental in making the designs more reliable, and to increase the likelihood that adequate operation is ensured despite manufacturing errors. This paper proposes a simple yet computationally efficient and reliable procedure for statistical analysis and yield optimization of resonator-based notch filters. Our methodology involves feature-based surrogate models that can be established using a handful of training data points, and employed for rapid evaluation of the circuit fabrication yield. Furthermore, a yield optimization procedure is developed, which iteratively sets up a sequence of feature-based models, constructed within local domains relocated along the optimization path, and uses them as predictors to find a robust (maximum yield) design at a low computational cost. The presented approach has been demonstrated using two complementary split ring resonator (CSRR)-based notch filters. The cost of statistical design is about a hundred of EM simulations of the respective filter, with yield evaluation reliability corroborated through EM-based Monte Carlo analysis. [ABSTRACT FROM AUTHOR]

Bromine in waste printed circuit boards has caused serious harm to the environment. How to deal with it safely is a problem. In this paper, the debromination of waste printed circuit boards by microwave gasification pyrolysis was studied, and the properties of pyrolysis products and the migration of bromine were analyzed. The optimum pyrolysis conditions of microwave steam atmosphere were 600 °C, 1000 W, 50 min, 2 mL/min. Compared with conventional pyrolysis and conventional steam pyrolysis, less solid products (60.39 wt %) were obtained, and more metal copper was enriched. The content increased from 27.46 % and 28.35 % to 30.63 %, respectively, and the diffraction peak intensity of copper was also enhanced. There is no obvious change in the type of functional groups of the solid product, and its microscopic morphology is smoother. Compared with conventional pyrolysis, the phenolic compounds in pyrolysis oil decreased, and increased compared with conventional steam pyrolysis. The content of H2 in the pyrolysis gas increased significantly, and the content of CO decreased significantly. Compared with conventional pyrolysis, the bromine content in pyrolysis gas and pyrolysis oil decreased from 94.5 % and 5.5 % to 1 %, respectively, and more bromine (98 %) in the raw material entered the aqueous solution. [ABSTRACT FROM AUTHOR]

In recent years, the spinel structures of the ferrite compounds are known for their remarkable versatile applications. In this work, CuFe2O4 nanoparticles were successfully synthesized by sol–gel combustion technique. The properties of the samples were analyzed by Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, Transmission Electron Microscope, Vibrating Sample Magnetometer. The complex permittivity (ε) and the complex permeability (μ) of the Cu-ferrites have been measured using the waveguide technique at frequency range 8–12 GHz and 12–18 GHz which represent X-band and Ku-band, respectively. It is found to increase the dielectric and magnetic properties with thicknesses increases but is almost constant with the frequency of both frequencies. The results illustrate, the potentiality used this nanomaterial for applications like suppression of electromagnetic interference in microwave circuits. The spinel CuFe2O4 nanoparticles showed sphere-like spherical particles with an average size of about 30 nm. [ABSTRACT FROM AUTHOR]

A vector method for recording phase-dynamic radio images is proposed by forming and numerically analyzing the S-parametric scattering matrix of multidisciplinary signatures of material media and objects. The key advantages of aperture capture of signal radio images by the method of a frequency-synthesized power spectral density function of a scattered wave radio profile are determined. On the basis of a vector analyzer of microwave circuits and broadband antennas of the Vivaldi type, an experimental laboratory installation for signal registration of time-scale radio images in the spectral region of 0.03–6.0 GHz has been built. The dependences of the influence of the angular characteristics of the object on the spectral-temporal structure of the formation of phase-dynamic radio images have been experimentally established. As the time-scale postprocessing of radio images, a method of cepstral transformation of S-parametric characteristics with convolution of basic signatures in the radiogenic part of the irradiated object is proposed. A series of cepstral convolutions of phase-dynamic radio images was obtained, establishing a functional relationship between the change of the signature of an object in time with its radio genome. [ABSTRACT FROM AUTHOR]

Superconducting microwave resonators are crucial elements of microwave circuits, offering a wide range of potential applications in modern science and technology. While conventional low-T c superconductors are mainly employed, high-T c cuprates could offer enhanced temperature and magnetic field operating ranges. Here, we report the realization of YBa 2 Cu 3 O 7 - δ superconducting coplanar waveguide resonators, and demonstrate a continuous evolution from a lossy undercoupled regime, to a lossless overcoupled regime by adjusting the device geometry, in good agreement with circuit model theory. A high-quality factor resonator was then used to perform electron spin resonance measurements on a molecular spin ensemble across a temperature range spanning two decades. We observe spin-cavity hybridization indicating coherent coupling between the microwave field and the spins in a highly cooperative regime. The temperature dependence of the Rabi splitting and the spin relaxation time point toward an antiferromagnetic coupling of the spins below 2 K. Our findings indicate that high-Tc superconducting resonators hold great promise for the development of functional circuits. Additionally, they suggest novel approaches for achieving hybrid quantum systems based on high-T c superconductors and for conducting electron spin resonance measurements over a wide range of magnetic fields and temperatures. [ABSTRACT FROM AUTHOR]

This paper introduces a novel algorithm for designing a low-pass filter (LPF) and a microstrip Wilkinson power divider (WPD) using a neural network surrogate model. The proposed algorithm is applicable to various microwave devices, enhancing their performance and frequency response. Desirable output parameters can be achieved for the designed LPF and WPD by using the proposed algorithm. The proposed artificial neural network (ANN) surrogate model is employed to calculate the dimensions of the LPF and WPD, resulting in their efficient design. The LPF and WPD designs incorporate open stubs, stepped impedances, triangular-shaped resonators, and meandered lines to achieve optimal performance. The compact LPF occupies a size of only 0.15 λg × 0.081 λg, and exhibits a sharp response within the transmission band, with a sharpness parameter of approximately 185 dB/GHz. The designed WPD, operating at 1.5 GHz, exhibits outstanding harmonics suppression from 2 GHz to 20 GHz, with attenuation levels exceeding 20 dB. The WPD successfully suppresses 12 unwanted harmonics (2nd to 13th). The obtained results demonstrate that the proposed design algorithm effectively accomplishes the LPF and WPD designs, exhibiting desirable parameters such as operating frequency and high-frequency harmonics suppression. The WPD demonstrates a low insertion loss of 0.1 dB (S21 = 0.1 dB), input and output return losses exceeding 30 dB (S11 = −35 dB, S22 = −30 dB), and an output ports isolation of more than 32 dB (S23 = −32 dB), making it suitable for integration into modern communication systems. [ABSTRACT FROM AUTHOR]

Emergency exit lights in public buildings are necessary for safety and evacuation. International safety standards require such lighting in many public places, like airports, schools, malls, hospitals, and other spaces, to prevent human casualties in emergencies. Emergency exit lights have become an essential part of casualty reduction projects. They can pose several application problems, including fire safety concerns. The issue of providing a safe way and operating emergency exit lights along one side of a long path arises during an emergency. Many studies in this field consider the case in which emergency exit lights' battery or main power fails. Power failures in dangerous situations such as fires or terrorist attacks make it difficult for people to escape. The lighting in open areas and stairwells during an emergency should be at least 2 lux. This work proposes an innovative technique for wirelessly powering emergency lights using microwave energy. Specifically, the study designed and fabricated a new wirelessly powered emergency lighting prototype. This prototype's wireless power transfer (WPT) base comprises an RF/DC converter circuit and an RF microwave transmitter station. The device can harvest RF microwave energy to energize the emergency light. This research aimed to develop a compact device that captures maximum RF strength to power emergency lights. As a prototype, the proposed device was designed to provide sufficient microwave energy to power an emergency light at 3 W over a 62 m distance. [ABSTRACT FROM AUTHOR]

This letter presents a compact fully differential branch‐line coupler. It is composed of folded substrate integrated suspended parallel strip line (SISPSL), which can generate slow‐wave effect and help reduce the circuit size. The used SISPSL type line is a fusion of double‐sided parallel‐strip line (DSPSL) and substrate integrated suspended line (SISL), which has the advantage of self‐packaging as compared with traditional DSPSL exposed to air. A DC to 30‐GHz differential transition from grounded coplanar waveguide (GCPW) to SISPSL is designed to test the SISPSL differential coupler. The implemented SISPSL branch‐line coupler has a compact size of 0.056 λg × 0.05 λg. This letter presents a compact fully differential branch‐line coupler using folded substrate integrated suspended parallel strip line (SISPSL), which has a compact size of 0.056 λg × 0.05 λg. A DC to 30‐GHz differential transition from grounded coplanar waveguide (GCPW) to SISPSL is designed to test the SISPSL differential coupler. [ABSTRACT FROM AUTHOR]

To improve the RX‐mode isolation of asymmetric T/R switches, a new circuit topology is proposed. The proposed asymmetric T/R switch topology features a second‐order band‐stop filter in its TX path, which extends the bandwidth of isolation in the RX mode. Based on the proposed topology, a Q‐band asymmetric T/R switch is designed and implemented in a 0.15‐µm GaAs pHEMT technology. Measured isolation in the RX mode is greater than 18.4 dB from 31.7 to 46.3 GHz, corresponding to a 1.46:1 bandwidth. [ABSTRACT FROM AUTHOR]

We report on the generic classical electric circuit modeling that describes standard single-tone microwave optomechanics. Based on a parallel R L C circuit in which a mechanical oscillator acts as a movable capacitor, derivations of analytical expressions are presented, including key features such as the back-action force, the input–output expressions, and the spectral densities associated, all in the classical regime. These expressions coincide with the standard quantum treatment performed in optomechanics when the occupation number of both cavity and mechanical oscillator are large. Besides, the derived analytics transposes optical elements and properties into electronics terms, which is mandatory for quantitative measurement and design purposes. Finally, the direct comparison between the standard quantum treatment and the classical model addresses the bounds between quantum and classical regimes, highlighting the features which are truly quantum, and those which are not. [ABSTRACT FROM AUTHOR]

Accurate measurement of the permittivity and loss tangent of low-loss materials is essential due to their special applications in the field of ultra large scale integrated circuits and microwave devices. In this study, we developed a novel strategy that can accurately detect the permittivity and loss tangent of low-loss materials based on a cylindrical resonant cavity supporting the TE111 mode in X band (8–12 GHz). Based on an electromagnetic field simulation calculation of the cylindrical resonator, permittivity is precisely retrieved by exploring and analyzing the perturbation of the coupling hole and sample size on the cutoff wavenumber. A more precise approach to measuring the loss tangent of samples with various thicknesses has been proposed. The test results of the standard samples verify that this method can accurately measure the dielectric properties of samples that have smaller sizes than the high Q cylindrical cavity method. [ABSTRACT FROM AUTHOR]

Dielectric resonator antenna (DRA) has secured an esteemed position in the field of antenna engineering technology due to its versatile features, including compactness, light-weight, low loss, high radiation efficiency, ease of excitation, diverse feeding techniques, multiple excitation modes, ease of integration with passive and active microwave integrated circuit components, a wide variety of available materials, simple fabrication techniques, and high degree of flexibility over wide frequency range. This article presents a comprehensive up-to-date review of research carried out in the field of DRA technology which includes an overview of DRA technology, its history, present status, and prospects. The basic parameters of microwave dielectric ceramic materials and the classification of materials based on utilization and material parameters are briefly discussed. The applications of DRA in different fields of science, engineering, and technology, overview of different reported DRA shapes, and the feeding techniques used to excite different modes of DRA are mentioned. Based on the control of DRA permittivity, shape/geometry, feeding techniques, and structural modifications, performance parameters engineering of DRA and its achievable performance in terms of low profile, compactness, high gain, wide beam, circular polarization, wide bandwidth, DRA decoupling methods for multiple input multiple output arrays, dielectric patch antenna, filtering DRA, and reconfigurable DRA are discussed. Different techniques used to attain and enhance the particular performance of DRA are highlighted. This review article also dilates upon the fabrication processes and characterization methods of DRA microwave dielectric ceramics, which play a very vital role in controlling the performance and properties of DRA. [ABSTRACT FROM AUTHOR]

Quantum entanglement is a key resource in currently developed quantum technologies. Sharing this fragile property between superconducting microwave circuits and optical or atomic systems would enable new functionalities, but this has been hindered by an energy scale mismatch of <104 and the resulting mutually imposed loss and noise. In this work, we created and verified entanglement between microwave and optical fields in a millikelvin environment. Using an optically pulsed superconducting electro-optical device, we show entanglement between propagating microwave and optical fields in the continuous variable domain. This achievement not only paves the way for entanglement between superconducting circuits and telecom wavelength light, but also has wide-ranging implications for hybrid quantum networks in the context of modularization, scaling, sensing, and cross-platform verification. [ABSTRACT FROM AUTHOR]

In this article, a narrow-band rejection plasmonic filter based on spoof surface plasmons polariton is reported. The structure is composed of a coplanar waveguide constructed with two defects at the bottom, periodic arc branches and metal strips. Varying the radian of the arc branch controls the frequency range of the filter's narrow band and the change of metal strip height enhances the rejection ability of filter. The filter is simulated and fabricated. Its simulation daters are consistent with the experimental daters. The proposed rejection filter exhibits a strong stopband in 4.8–5.0 GHz, whose transmission coefficient is less than − 35 dB in simulation. In the passband, the transmission loss is around 1 dB. It is hoped that this filter may have better application prospect in integrated circuits and microwave communication devices. [ABSTRACT FROM AUTHOR]

Josephson microwave circuits are essential for the currently flourishing research on superconducting technologies, such as quantum computation, quantum sensing, and microwave signal processing. To increase the possible parameter space for device operation with respect to the current standards, many materials for superconducting circuits are under active investigation. Here, we present the realization of a frequency-tunable, weakly nonlinear Josephson microwave circuit made of the high-temperature cuprate superconductor YBa2Cu3O7 (YBCO), a material with a high critical temperature and a very high critical magnetic field. An in situ frequency-tunability of ∼ 300 MHz is achieved by integrating a superconducting quantum interference device (SQUID) into the circuit based on Josephson junctions directly written with a helium ion microscope (HIM). Our results demonstrate that YBCO-HIM-SQUID microwave resonators are promising candidates for quantum sensing and microwave technology applications. [ABSTRACT FROM AUTHOR]

Purpose: The design and implementation of a broadband quasi-monolithic microwave integrated circuit (q-MMIC) power amplifier (PA) is presented for 0.2 to 2.2 GHz applications. Design/methodology/approach: To obtain an efficient, high-gain and high-power performance with in a compact and low-cost size, the prototype is based on Gallium nitride (GaN) on SiC 0.25-µm transistors, whereas the passive matching networks are realized on an AlN substrate as thin film circuit. Findings: Measured results of the q-MMIC PA across the 0.2 to 2.2 GHz band show at least 32 ± 3 dB small-signal gains, an output power of 7 to 12 W and an average power add efficiency greater than 54%. The q-MMIC occupies an area of 12.8 × 14.5 mm2. Originality/value: To the best of the authors' knowledge, this work reports the first full integrated PA which covers the frequency range of 0.2 to 2.2 GHz and achieves the combination of highest gain, about 10 W output power, together with the smallest component size among all published GaN PAs to date. [ABSTRACT FROM AUTHOR]

Hybrid dynamic systems have recently gained interest with respect to both fundamental physics and device applications, particularly with their potential for coherent information processing. In this perspective, we will focus on the recent rapid developments of magnon-based hybrid systems, which seek to combine magnonic excitations with diverse excitations for transformative applications in devices, circuits, and information processing. Key to their promising potentials is that magnons are highly tunable excitations and can be easily engineered to couple with various dynamic media and platforms. The capability of reaching strong coupling with many different excitations has positioned magnons well for studying solid-state coherent dynamics and exploiting unique functionality. In addition, with their gigahertz frequency bandwidth and the ease of fabrication and miniaturization, magnonic devices and systems can be conveniently integrated into microwave circuits for mimicking a broad range of device concepts that have been applied in microwave electronics, photonics, and quantum information. We will discuss a few potential directions for advancing magnon hybrid systems, including on-chip geometry, novel coherent magnonic functionality, and coherent transduction between different platforms. As a future outlook, we will discuss the opportunities and challenges of magnonic hybrid systems for their applications in quantum information and magnonic logic. [ABSTRACT FROM AUTHOR]

The Goubau line is a unique transmission line that consists of only a single conductor. Its unique properties make it a solid candidate for low-loss RF propagation and wireless power transfer applications. However, the applied theory of this line that has been established thus far is missing key details of the line's characteristics. Namely, no discussion has been made on the Goubau line's ohmic current distribution or its effective characteristic impedance that would be used in RF/microwave circuit analysis scenarios. Furthermore, the method previously used to solve the waveguide mode is laborious and obsolete when considering current computational methods. In this work, an updated, efficient mode solution process for the Goubau line will be presented, and the current, loss, and characteristic impedance of the line will be discussed. Additionally, all other waveguide parameters such as wave velocity, guide wavelength, propagation constant, etc. will be investigated. [ABSTRACT FROM AUTHOR]

We investigate highly confined and isolated surface modes in a phononic crystal plate based on pillars with cap layers. The structure is made of a thin membrane supporting periodic pillars each composed of one cylinder surmounted by a disk shaped cap layer. An optimal choice of the geometrical parameters and material composition allows the structure to support isolated radial contour modes confined in the cap layer. In this study, we consider diamond and gold (Au) as the pillar and cap layers, respectively, and aluminum nitride as a thin membrane owing to the strong contrast in their elastic and density properties and to their compatibility with the integrated circuit technology and microwave electroacoustic devices. The phononic crystal based on diamond pillars allows us to induce a wide stop band frequency, and the addition of the Au disk shaped layer on diamond pillars enables us to introduce flat modes within the bandgap. We demonstrate that one can optimize the flat mode frequencies by varying the geometrical parameters of the Au cap layer. The quality factor (Q) of a cavity resonator composed of one line gold/diamond pillar surrounded by an array of diamond pillars on both sides has been investigated. These results clearly show that, using this design approach, one can (i) reduce the acoustic energy leakage out of the resonator and (ii) optimize the cavity resonator's Q factor by varying only the geometrical parameters of the gold cap layer. The proposed design provides a promising solution for advanced signal processing and sensing applications. [ABSTRACT FROM AUTHOR]

In this study, a K‐band CMOS low‐noise amplifier (LNA) with a 180° phase shift function is presented to reduce the chip area of the beamforming system. The proposed LNA is composed of three stages, and the last stage is designed with a differential cascode structure for 180° phase shift function. The 180° phase shift function was implemented by dividing one cascode transistor into two transistors. As a result, it is possible to equip the 180° phase shift function without an additional chip area. The LNA was designed with a 65‐nm CMOS process to verify the feasibility of the proposed technique. The core size was 0.66 × 0.41 mm2. The measured phase difference between 0° and 180° phase shift modes was approximately 178° in the operating frequency of 22.0 GHz. The measured noise figure and gain were 3.8 and 12.7 dB, respectively. [ABSTRACT FROM AUTHOR]

A compact front module with integrated miniaturised antenna in package for parabolic reflector antenna is presented for GEO‐KOMPSAT‐2A (GK‐2A) satellite ground terminal application at 1692 MHz. The active feeder antenna module consists of four parts: a pair of miniaturised slot antennas, a pair of differential feeding lines, a metal shielding box, and front circuits, including a low noise amplifier (LNA) and a surface acoustic wave bandpass filter (SAW BPF). To reduce the lateral size of the feeder antennas and obtain required radiation patterns, meandered radiation slots are suggested and fed by a pair of differential coplanar waveguide (CPW) lines. The antenna substrate serves as the module cover and the electromagnetic shielding with a lateral size of 48 × 48 mm2 (0.27 × 0.27 λ2 ${\lambda }^{2}$). Additionally, the feeder antenna module is proven to work with the specified parabolic reflector, both in theory and simulation. The front module with the packaged antenna is fabricated, and the measured output gain exceeds 20 dBi within a desired narrow band. Moreover, the module also achieves excellent performance in the GK‐2A satellite signal‐receiving experiment when used to feed the parabolic reflector antenna. The entire front module exhibits good package integration and application performance. [ABSTRACT FROM AUTHOR]

An integral equation technique for the analysis of multiport H‐plane microwave circuits composed of an unlimited number of arbitrarily shaped metallic and/or dielectric elements is proposed. The structure under study is divided into different regions after the application of the surface equivalence principle. Following this approach, the access waveguide ports are modelled by means of parallel plate Green's functions, whereas the central region is characterised by 2D rectangular cavity Green's functions. The use of this kind of Green's functions represents a novelty for solving H‐plane integral equation problems. For the first time, the Ewald method has been employed in order to accelerate the computation of the 2D rectangular cavity Green's functions and their derivatives, needed in the integral equation. In addition, convergence studies show the numerical convenience of using the Ewald method to achieve a fast and accurate evaluation of these Green's functions. Results show that the analysis can be very efficient if the structure is segmented in a proper way based on fitting the cavity resonator within the geometry of the structure under analysis. In fact, all the walls of the structure that are coincident with the auxiliary resonator need not to be discretised during the numerical solution. Finally, several simulation examples of practical inductive microwave circuits are presented and discussed, showing a good agreement and higher computational efficiency when compared to results provided by commercial full‐wave software tools and measurements. [ABSTRACT FROM AUTHOR]

Electromagnetic pollution has become an increasingly hot issue due to the rapid development of wireless communications and microwave circuits in the GHz frequency range. Electromagnetic interface (EMI) shielding materials have received more and more attention due to their promising application potential. Aerogel-based composites have low density, large porosity, and high specific surface area for EMI shielding fields. This mini-review article briefly describes the research progress of aerogel-based composites for EMI shielding applications. Four types of aerogel-based composites are reviewed comparably such as carbon-based composites, MXene-based composites, biomass-based composites, and conductive polymer-based composites. The interface or surface between the filler/fiber and matrix favors the increase of EMI value due to its synergistic effect. Moreover, the current problems and future developments of aerogel-based composites are also suggested for EMI shielding applications based on our knowledge. It is expected to provide a reference for improving applications of aerogel-based composites in EMI shielding fields. [ABSTRACT FROM AUTHOR]

In this article, a novel nonisolated multiple input dc-dc converter (MIC) is proposed for all-electric hybrid energy storage systems. The proposed MIC is capable of bidirectional operation in noninverting buck–boost configuration and can accommodate the simultaneous energy transfer from multiple sources of different voltage levels to the dc bus. As compared to counterparts, the proposed MIC utilizes a smaller number of inductors and requires only one bidirectional switch to integrate any extra energy storage. Within the framework, a novel voltage transformation, operation modes, and control method are presented in detail. The performance and key features of operation with varying voltage levels and duty cycles of the proposed MIC are numerically verified through a high-fidelity hardware-in-the-loop platform and experimentally validated on an in-house test rig. [ABSTRACT FROM AUTHOR]

The rapid progress in quantum information processing leads to a rising demand for devices to control the propagation of electromagnetic wave pulses and to ultimately realize universal and efficient quantum memory. While in recent years, significant progress has been made to realize slow light and quantum memories with atoms at optical frequencies, superconducting circuits in the microwave domain still lack such devices. Here, we demonstrate slowing down electromagnetic waves in a superconducting metamaterial composed of eight qubits coupled to a common waveguide, forming a waveguide quantum electrodynamics system. We analyze two complementary approaches, one relying on dressed states of the Autler–Townes splitting and the other based on a tailored dispersion profile using the qubits tunability. Our time-resolved experiments show reduced group velocities of down to a factor of about 1500 smaller than in vacuum. Depending on the method used, the speed of light can be controlled with an additional microwave tone or an effective qubit detuning. Our findings demonstrate high flexibility of superconducting circuits to realize custom band structures and open the door to microwave dispersion engineering in the quantum regime. [ABSTRACT FROM AUTHOR]

High-power microwave-induced low-pressure discharges seriously threaten the reliability of space payload systems. Under extremely low-pressure conditions, the evolution of ionized and secondary electrons at the initial stage of discharge is crucial to figure out the discharge process. Therefore, this paper investigates the development of multiple electrons in the discharge process under a highly low-pressure environment using numerical simulation. A three-dimensional simulation model based on the Monte Carlo algorithm is established by considering various electron-gas collisions and secondary electron emissions from different material surfaces. The evolution characteristics of various electrons' populations, energy, and distribution patterns during the discharge process are analyzed. In addition, the influence of the critical conditions at different air pressures on the electron evolution during the discharge process and the intrinsic causes are also investigated. This study is significant in revealing the transition characteristics between multipactor and low-pressure discharge and exploring their inherent mechanisms. [ABSTRACT FROM AUTHOR]

This article demonstrates a deep learning (DL)-based methodology for the rapid simulation of planar microwave circuits based on their layouts. We train convolutional neural networks (CNNs) to compute the scattering parameters of general, two-port circuits consisting of a metallization layer printed on a grounded dielectric substrate, by processing the metallization pattern along with the thickness and dielectric permittivity of the substrate. This approach harnesses the efficiency of CNNs with pattern recognition tasks and extends previous efforts to employ neural networks for the simulation of parameterized circuit geometries. Furthermore, we integrate this CNN in a hybrid network with a long-short term memory (LSTM) module that uses coarse mesh finite-difference time-domain (FDTD) simulation data as an additional input. We show that this hybrid network is computationally efficient and generalizable, accurately modeling geometries well beyond those that the network has previously seen. [ABSTRACT FROM AUTHOR]

Microwave filters are indispensable passive devices for modern wireless communication systems. Nowadays, electromagnetic (EM) simulation-based design process is a norm for filter designs. Many EM-based design methodologies for microwave filter design have emerged in recent years to achieve efficiency, automation, and customizability. The majority of EM-based design methods exploit low-cost models (i.e., surrogates) in various forms, and artificial intelligence techniques assist the surrogate modeling and optimization processes. Focusing on surrogate-assisted microwave filter designs, this article first analyzes the characteristic of filter design based on different design objective functions. Then, the state-of-the-art filter design methodologies are reviewed, including surrogate modeling (machine learning) methods and advanced optimization algorithms. Three essential techniques in filter designs are included: 1) smart data sampling techniques; 2) advanced surrogate modeling techniques; and 3) advanced optimization methods and frameworks. To achieve success and stability, they have to be tailored or combined together to achieve the specific characteristics of the microwave filters. Finally, new emerging design applications and future trends in the filter design are discussed. [ABSTRACT FROM AUTHOR]

This article proposes a novel parametric modeling technique incorporating a joint polynomial-transfer function with neural networks (short for neuro-PTF) for electromagnetic (EM) behaviors of microwave filters. In the proposed technique, the polynomial function is introduced together with the pole-residue-based transfer function to represent the EM responses. The pole-residue-based transfer function is used to represent the whole EM response at the beginning and is subsequently divided into multiple subtransfer functions where each subtransfer function contains one pair of pole/residue. A novel smoothness-discriminating algorithm is proposed to judge the smoothness of each subtransfer function response and separate the pole/residue pairs whose subtransfer function response is determined to be smooth. The proposed method introduces low nonlinear polynomial functions to re-fit the smooth parts of subresponse and remains the nonsmooth parts of subresponse for the highly nonlinear transfer functions to represent. By this way, the proposed method avoids the discontinuity problems of nonunique parameter extraction caused by fitting smooth curves using the highly nonlinear transfer function. Neural networks are proposed to learn the relationship between the polynomial coefficients/poles/residues and the geometrical parameters. Utilizing both advantages of the polynomial functions and transfer functions, the proposed method can produce more accurate models than the existing neuro-TF methods, especially with large geometrical variations. The accuracy and robustness of the proposed technique are demonstrated using three EM application examples of microwave filters. [ABSTRACT FROM AUTHOR]

Design of microwave circuits require extensive simulations, which often take significant computational time due to design complexity. This can be addressed through neural networks (NNs) that provide predictive capability. Predictions often come with uncertainties that need to be quantified. Moreover, optimization and inverse designs are better done using probabilities. This article describes the use of Bayes theorem and machine learning (ML) for solving complex microwave design problems. [ABSTRACT FROM AUTHOR]

Geometry parameters of contemporary microwave passives have to be carefully tuned in the final stages of their design process to ensure the best possible performance. For reliability reasons, the tuning has to be carried out at the level of full-wave electromagnetic (EM) simulations. This is because traditional modeling methods are incapable of quantifying certain phenomena that may affect the operation and performance of these devices, such as cross-coupling effects. As a consequence, the designs yielded with the use of equivalent network models may only serve as starting points that need further refinement. Unfortunately, simulation-driven numerical optimization is computationally demanding even in the case of local search procedures. Thus, significant research efforts have been aimed toward identifying effective ways of expediting EM-driven optimization procedures, critical from the point of view of cost of design cycles. Among these, one may list the recently proposed multifidelity optimization frameworks. Another option for accelerating simulation-driven design procedures is sparse sensitivity updating schemes, where costly gradient estimation through finite differentiation (FD) is suppressed for selected variables. This work proposes a novel algorithm that capitalizes on both aforementioned mechanisms to reduce the optimization cost of local gradient-based parameter tuning of compact microwave components. In our approach, multifidelity optimization is further expedited by replacing expensive FD sensitivity updates with the Broyden formula for selected design variables. Verification using two microwave structures, a branch-line coupler and a power divider, demonstrates average savings of around 80% over the basic trust-region (TR) routine, with only minor degradation of the design quality. [ABSTRACT FROM AUTHOR]