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This paper presents a novel design method for a dual-band power amplifier (PA) with widely-spaced frequency bands, suitable for concurrent sub-6 GHz and millimeter-wave 5G band operation. The approach de-couples the design of the high- and low-frequency impedance matching networks, so that the high-frequency matching network can be fully designed before the low-frequency path is added. The circuit architecture includes a built-in bias structure for the high-frequency band so that a separate broadband or multiband bias network is avoided. This design process is first described theoretically, and a detailed design example of a C/Ka concurrent dual-band MMIC using quarter-wavelength lines implemented in a 150 nm GaN process is described. The MMIC is measured in CW with 32.5 dBm and 33% peak power and PAE in C band and 31 dBm and 24% peak power and PAE in Ka-band. Measurements with 100-MHz LTE-like modulated signals are also shown, including both individual and concurrent operation of the two bands.

Abstract A novel chip to double‐ridge rectangular waveguide transition, with an ultra‐broadband operation bandwidth exceeding three standard rectangular waveguide (WR) bands of WR15, WR12, and WR10 is demonstrated for the first time in this letter, to the best of authors' knowledge. This bandwidth is achieved by coupling the microstrip mode directly to the fundamental TE mode of the waveguide. A unique feature of this transition is that the transition design can be implemented on substrates with a high dielectric constant, which makes it suitable for integration with monolithic microwave integrated circuits (MMICs). A back‐to‐back transition is realized using a split‐block assembly and 254 μm thickness alumina substrate (εr=9.8 at 80 GHz). The latter acts as an MMIC substrate substitute, including a tapered microstrip and a 50 Ω coplanar waveguide pad for probe‐based measurement. Two novel mechanical assembly concepts, involving die‐attach‐foil and indium solder, are used to build two split‐block prototypes. The simulated and measured S‐parameters of the transition are demonstrated from 35 to 125 GHz.

A novel chip to double‐ridge rectangular waveguide transition, with an ultra‐broadband operation bandwidth exceeding three standard rectangular waveguide (WR) bands of WR15, WR12, and WR10 is demonstrated for the first time in this letter, to the best of authors' knowledge. This bandwidth is achieved by coupling the microstrip mode directly to the fundamental TE mode of the waveguide. A unique feature of this transition is that the transition design can be implemented on substrates with a high dielectric constant, which makes it suitable for integration with monolithic microwave integrated circuits (MMICs). A back‐to‐back transition is realized using a split‐block assembly and 254 μm$\umu {\rm {m}}$ thickness alumina substrate (εr=9.8$\varepsilon _{\text{r}}=9.8$ at 80 GHz). The latter acts as an MMIC substrate substitute, including a tapered microstrip and a 50 Ω$\Omega$ coplanar waveguide pad for probe‐based measurement. Two novel mechanical assembly concepts, involving die‐attach‐foil and indium solder, are used to build two split‐block prototypes. The simulated and measured S‐parameters of the transition are demonstrated from 35 to 125 GHz. [ABSTRACT FROM AUTHOR]

Abstract 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.

Oscillation-based testing (OBT) and Oscillation-based built-in self-testing (OBIST) circuits enable detection of catastrophic faults in analogue and RF circuits, but both are sensitive to process, voltage and temperature (PVT) variation. This paper investigates 15 OBT and OBIST feature extraction strategies, and four approaches to threshold selection, by calculating figure-of-merit (FOM) across PVT variation. This is done using a 2.4 GHz LNA in $0.35 \mu \mathrm{m}$ CMOS as DUT. Of the 15 feature extraction approaches, the OBT approaches are found more effective, with some benefit gained from switched-state detection. Of the four approaches to threshold selection (nominal-ranged static thresholds, extreme-range static thresholds, temperature dynamic thresholds, and simple noise-filtered tone detection), dynamic thresholds resulted in the highest average FoM of 0.919, with the best FoM of 0.952, with a corresponding probability of test escape $P\left(T_E\right)$ and yield loss $P\left(Y_L\right)$ of $5 \cdot 10^{-2}$ and $1.89 \cdot 10^{-2}$ respectively but requires accurate temperature measurement. Extreme static threshold selection resulted in a comparable average FoM of 0.912, but with less susceptibility to process variation and without the need for temperature measurement. Binary detection of a noise-filtered oscillating tone is found the least complex approach, with an average FoM of 0.891.

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]

When the power transformer is connected to power grids, due to the existing remanent magnetism (RM) and the voltage transient component, the transformer will generate a large magnetizing inrush current (MIC). The MIC not only seriously threatens the safe operation of the transformer, but also causes the misoperation in the differential protections. To solve the aforementioned problems, a novel MIC elimination strategy of the hybrid transformer (HT) based on an asynchronous closing technology is proposed in this article. First, through the rational design of the HT topology, the parallel auxiliary winding (PAW) of the HT is established and the magnetic coupling mechanism is realized, which lay the magnetic circuit foundation for the MIC management. Second, a step-type synchronous magnetic field is established through PAW without considering RM. After the action of step-type magnetic field, the core flux increases sinusoidal linearly and enters into the rated steady stable. Finally, by controlling the stabilization time of the oblique wave and the primary voltage signal of the power grid, when the core flux is stabilized, the nonsynchronous closing of the HT can effectively alleviate the generation of the MIC. The validity and feasibility of the proposed scheme are verified by building an HT prototype platform, which provides some reference for the difficulty of measuring RM and avoiding MIC in the power system. [ABSTRACT FROM AUTHOR]

Abstract This letter presents a novel method to implement a 10–20 GHz low‐noise amplifier (LNA) with simultaneous noise and input matching performance. That is, the Mille effect caused by the gate‐drain parasitic capacitance Cgd is eliminated by converting the succeeding‐stage impedance into the required load using frequency‐dependent negative feedbacks and a π‐type network. The corresponding analytical equation is also derived for the first time. To verify the feasibility, the circuit is fabricated via a 0.15‐μm GaAs p‐HEMT process with a compact size of 0.9×1.9 mm2. The measured results show that the proposed LNA features a peak gain of 26.1 dB, a minimum noise figure of 1.08 dB, and an input return loss of less than −15.8 dB.

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]

Microfluidic impedance cytometry (MIC) has wide applications in single-cell analysis. However, the complex microelectrode fabrication process seriously restricts the miniaturization and commercialization of MIC devices. Common microelectrode configurations such as a coplanar electrode, a symmetric electrode, and a liquid electrode have difficulties in meeting the requirements of high detection accuracy and simple fabrication at the same time. Hence, a simple 3-D symmetric microelectrode fabrication process is developed in this article. We design a microchip containing both a microfluidic channel and a microelectrode channel. The alloy with high surface tension and low melting point is used to fabricate the 3-D microelectrodes by injecting the melted alloy into the microelectrode channel with a properly controlled driving pressure. The melted alloy flows into the microelectrode channel and automatically stops at the end of the microelectrode channel due to the effect of surface tension. This process intrinsically provides a high-precision alignment for the 3-D microelectrodes. The fabricated MIC chip is experimentally tested, and the results show that it can effectively count and classify microspheres of different sizes. This study can facilitate the development and commercialization of MIC devices. [ABSTRACT FROM AUTHOR]

Using artificial neural networks (NNs) in microwave medical diagnosis is recently of great interest in various problems such as early breast cancer detection, brain stroke, and leukemia monitoring. NNs facilitate the process by directly assessing the presence and properties of the tissues based on the scattered field values. Although the reported studies obtained successful results through the application of NNs to microwave diagnostic problems, they used large numbers of input data. The NN input, referred to as features, for microwave diagnosis is composed of scattered fields namely antenna transmission and reflections at the frequency of choice. Large input data increase both the number of required training samples and computational cost. Optimizing the number of antennas and frequency of operation is therefore critical to improving the performance of NN-based medical diagnosis. This work considers the correlations between the effects of different frequencies and receiver/transmitter (Rx/Tx) antennas separately in order to objectively reduce the number of features. Optimized feed-forward NNs are applied to detect the presence of object(s) with permittivity value above the predefined level within the solution domain. It is performed by designating various permittivity values to the internal object(s). Promising results were obtained by reducing the number of features approximately seven times. [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]

The design of miniaturized microwave components is largely based on computational models, primarily, full-wave electromagnetic (EM) simulations. The EM analysis is capable of giving an accurate account for cross-coupling effects, substrate and radiation losses, or interactions with environmental components (e.g., connectors). Unfortunately, direct execution of EM-based design tasks, such as parametric optimization or uncertainty quantification (UQ), may turn prohibitively expensive in computational terms. A workaround has been offered by surrogate-assisted procedures that capitalize on replacing expensive EM simulations by fast metamodels, notably data-driven ones. However, the construction of general-purpose metamodels is impeded by the curse of dimensionality as well as a limited capability of approximation techniques to represent highly nonlinear responses of microwave devices. This article proposes a novel technique that integrates the performance-driven modeling paradigm as well as variable-resolution EM simulations. The former focuses on the construction of the surrogate in the parameter space subset encompassing high-quality designs, which effectively addresses the dimensionality issues. The latter—realized through co-kriging—contributes to further computational savings by executing the majority of circuit evaluations at the level of coarse-discretization EM analysis. Verification experiments conducted for three microstrip components demonstrate the superiority of the proposed approach over existing performance-driven techniques, let alone conventional modeling procedures, both with respect to accuracy and computational cost of the surrogate construction. [ABSTRACT FROM AUTHOR]

This article presents an overview of artificial neural network (ANN) techniques for a microwave computer-aided design (CAD). ANN-based techniques are becoming useful for performing forward/inverse modeling for active/passive components to enhance a circuit design. With measured or simulated data of microwave devices, ANNs can be trained to learn relevant microwave relationships, which are, otherwise, computationally expensive or for which efficient analytical formulas are not available. Fundamental concepts of the ANN structure and training, such as feedforward neural networks (FFNNs), recurrent neural networks (RNNs)/dynamic neural networks (DNNs)/time-delay neural networks (TDNNs), deep neural networks, and neural network training and extrapolation, are described. Knowledge-based neural networks (KBNNs) are described for improving the accuracy and reliability of modeling and design optimization. Various advanced ANN techniques, such as neuro-transfer function (neuro-TF) modeling, neural network inverse modeling, and deep neural network modeling, are discussed. The existing and emerging applications of ANN in microwave CAD are identified, such as electromagnetic (EM)/multiphysics modeling, modeling of nonlinear circuits and transistors, filter design, very large-scale integration (VLSI) interconnects, oscillator, transmitter and receiver modeling, and CAD applications in such as gallium nitride (GaN) high electron-mobility transistor (HEMT), wireless power transfer (WPT), microelectromechanical system (MEMS), and substrate-integrated waveguide (SIW). [ABSTRACT FROM AUTHOR]

To improve the power handling capability at ground stations of a 5.8-GHz solar space power satellite using microwave power transmission, a power charge-pump meta-semiconductor field-effect transistor (MESFET)-based rectifier is presented in this article. Unlike conventional microwave Schottky diodes, diode-connected MESFETs, whose nonlinear characteristics help them to have a unique current–voltage (I-V) curve that overcomes the limitations of a Schottky diode. Thus, the maximum input power of the proposed rectifier is extended up to 251.2 mW by replacing a Schottky diode with a diode-connected MESFET. Additionally, a class F harmonic processing network is introduced to control the voltage and current waveform at the load of the rectifier. Consequently, the RF-dc conversion efficiency is increased since the power dissipation is limited at the junction resistance of both the drain and the source of the MESFET. Owing to the abnormal characteristics of the diode-connected MESFET, the measured conversion efficiency of our rectifier is approximately 73.2% at 126 mW, and the input power range for rectifier efficiency higher than 50% is between 16 and 224 mW. The proposed rectifier for the space solar power satellite application is demonstrated and verified using a microwave wireless power transmission system. [ABSTRACT FROM AUTHOR]

In this work, an electromagnetic black hole based on gradient-index metamaterials is designed and fabricated by drilling holes in easily available materials to achieve efficient microwave heating in multimode cavities. This black hole shows superior performance in improving the utilization of microwave energy when the real part of the relative permittivity varies from 10 to 80 and the loss tangent of the heated material changes within 0.1–1. Different volume fractions of ethanol aqueous solution are used as test material to verify the effectiveness of electromagnetic black hole, and the experimental results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

In this letter, a novel impedance matcher (IM) is designed based on Zeta converter to overcome the shortcomings of other impedance matching methods and improve the load range in low resistances. System-level verification demonstrates that the novel IM has a potential application value for microwave wireless power transmission (MWPT) system. Measurement results show the maximum power conversion efficiency (PCE) of the novel rectifier with IM can reach 73% when the input power is 32 dBm. In addition, the proposed rectifier circuit with IM can operate with above 60% overall efficiency when the load varies from 0.01 to 10 $\text{k}\Omega $ (1:1000) as input power of 32 dBm. Compared with that without IM, the application of IM can increase the load range by at least 1100% when the rectifier efficiency is >50.7%. The measurement results demonstrate that the rectifier circuit has a better performance when connected to the novel IM. [ABSTRACT FROM AUTHOR]

Abstract The goal is to illustrate new errors about using the figures‐of‐merit NF and IIP, by investigating an AGC‐less microwatt ultrawideband gm‐boosted CMOS RF system with noise/distortion cancellation. The system composed of limiter and LNA is designed for 0.3–10.7 GHz at 1.8 V. Thanks to the limiter, the impact of noises and distortions is cancelled and the LNA acts linear without any saturation or block, as well as, it becomes AGC‐less. Additionally, achievements prove that NF and IIP sometimes can be accompanied by error, hence engineers must always consider all aspects of a system together during their evaluations. Although this work is not experimental, it applies different methods such as “Regenerating”, “Comparing Calculations with Simulations” and “Monte Carlo” to demonstrate the reliability of achievements for applying in a SAW‐less RFIC.

Abstract In this paper a novel tuneable LNA is presented. This LNA is designed with two separated structures which both of them utilize noise cancellation technique and some other approaches such as gain boosting and T‐transformer feedback. Each proposed LNA has two stages that the first stage is designed based on noise cancellation and the second stage uses common gate structure. The proposed LNA type (A) utilises the switched capacitance in the first stage to tune the centre frequency and a gain boosting in the second stage to increase the gain. The second proposed LNA type (B) has implemented the parallel networks to decrease the change in the gain values of the LNA in different channels. The T‐transformer approach is used in each parallel network to decrease the inductors value and improve the input matching. In the second stage, the negative feedback is also employed to control the bandwidth. The proposed LNA is simulated in ADS software with TSMC 130 nm CMOS technology and the layout is designed by Cadence. The LNA type (A) has 22.7 dB gain in 28.8 GHz and the noise figure of 2 dB. The IIP3 for this LNA is 0 dBm in 25.42 GHZ. For the LNA type (B), the gain and noise figure standard deviations are 0.25 and 0.057 respectively which shows minimum variations by frequency tuning. For this LNA, the maximum gain is 20.5 dB and the noise figure is 2 dB at 31.42 GHz. Finally the performances of the proposed LNAs have been compared with those of LNAs which have been recently published.

Standard operation of a conventional microwave oven 2.45-GHz “cooker” magnetron with 4.0–4.3 kV of pulsed applied voltages at 0.17–0.19-T magnetic fields results in generation of pulsed microwave power 1.8–2.8 kW, which is recalculated to an average microwave power 0.9–1.9 kW when the “cooker” magnetron operates with 50% duty cycle while driven by a “rectified” ac voltage from the wall-plug. It has been shown in many experimental studies of “cold-start” operation of a standard ten-vane 2.45-GHz “cooker” magnetron that it readily sustains, when properly conditioned, up to ~10-kV dc and up to ~14 kV of peak-to-peak ac applied voltage with just a few microamphere cold (field emission) leakage (anode) current. The latter suggests that a standard 2.45-GHz “cooker” magnetron may successfully operate in the desired, lowest $\pi $ -mode with much more output microwave power at even higher magnetic fields when driven by up to ~10 kV of dc or quasi-dc appropriate, synchronous applied voltage. Results of improved concurrent electromagnetic particle-in-cell (ICEPIC) simulations of magnetron operation at different magnetic fields with synchronous applied voltages show that, for example, with 8.0-kV applied voltage at 0.35-T magnetic field, the 2.45-GHz “cooker” magnetron is able to generate up to 6.0 kW of pulsed microwave power with an anode current of ~0.9 A. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a photonic scheme to generate reconfigurable radar waveforms based on an integrated silicon in-phase and quadrature-phase (IQ) modulator. It has significant advantages over commercial LiNbO3 modulator-based schemes in terms of the compatibility with CMOS technology, compact size, light weight, low cost and low power consumption. Experimentally, multi-format radar waveforms, including dual-chirp microwave waveforms, phase-shift keying signals, and amplitude-shift keying signals are successfully generated. The generated waveforms have flexible tunability of center frequency and bandwidth. Our scheme shows the great potential of an on-chip scheme to generate multi-format microwave waveforms for modern radars and electronic warfare systems. [ABSTRACT FROM AUTHOR]

This article proposeda SPICE-compatible model to fast simulate the buzz noise problem in a camera device. Based on the reciprocity theorem, the proposed SPICE-compatible model consists of cascaded scattering (S) parameters extracted from the field coupling. It can provide an accurate estimation of the buzz noise transfer function (TFtotal) between the radio-frequency antenna and the audio system within an average error of 1 dB. Besides, the proposed model allows for coupling decomposition by separating the audio system into different regions, fast buzz noise mitigation by adding filtering circuits, and fast antenna evaluation/selection by characterizing the TFtotal with different antenna structures. The advantage of the proposed model is that, instead of multiple 3-D simulations during the predesign-stage troubleshooting, it is a fast SPICE-compatible method with SPICE simulation time of 4.5 min and one-time 3-D full-wave simulation on the camera system studied. It provides quick estimation on the potential buzz noise problems, coupling decomposition,buzz noise mitigation methods, and selection of antenna structures. [ABSTRACT FROM AUTHOR]

Recent investigations using polarimetric decomposition and numerical models have helped to improve the understanding of how radar signals interact with lake ice. However, further research is needed on how radar signals are impacted by varying lake ice properties. Radiative transfer (RT) models provide one method of improving this understanding. These are the first published experiments using the snow microwave RT (SMRT) model to investigate the response of different frequencies (L-, C-, and X-band) at horizontal-horizontal (HH) and vertical-vertical (VV) polarizations using various incidence angles (20°, 30°, and 40°) to changes in ice thickness, porosity, bubble radius, and ice–water interface roughness. This is also the first use of SMRT in combination with a thermodynamic lake ice model. Experiments were for a lake with tubular bubbles and one without tubular bubbles under difference scenarios. An analysis of the backscatter response to different properties indicates that increasing ice thickness and layer porosity have little impact on backscatter from lake ice. X-band backscatter shows increased response to surface ice layer bubble radius; however, this was limited to other frequencies except at shallower incidence angles (40°). All three frequencies display the largest response to increasing root mean square (rms) height at the ice–water interface, which supports surface scattering at the ice–water interface as being the dominant scattering mechanism. These results demonstrate that the SMRT is a valuable tool for understanding the response of backscatter to changes in freshwater lake ice properties and could be used in the development of inversion models. [ABSTRACT FROM AUTHOR]

This study characterizes the marginally known angular-dependent polarization difference (PD) of the land surface emissivity (LSE), using the microwave humidity sounder (MWHS) onboard China’s Sun-synchronous satellite FengYun-3B (FY-3B). The instrument has two quasi-polarization channels at 150 GHz in addition to the three water-vapor absorption channels in the vicinity of 183 GHz, allowing observations at quasi-vertical and quasi-horizontal polarizations with its cross-track scanning geometry. The Saharan and Taklimakan deserts are taken as examples due to the relatively homogeneous surface conditions. In the two 150-GHz channels of MWHS, the polarization bias is corrected according to the measurements at the Earth incidence angle (EIA) of 0°. The monthly mean quasi-polarization difference (QPD) at 150 GHz is found to be varying with the EIA and exhibits seasonal variations over deserts. The QPD reaches a maximum value at the EIA of ~35°, while the zero value appears near the EIA of ~53° [equal to the satellite viewing angle (VA) of 45°] as expected. In contrast to the relatively stable and low QPD over Sahara, the QPD, quasi-polarized emissivity difference, and pure polarized emissivity difference (PPED) are generally larger in the Taklimakan Desert, where the maximum monthly QPD is ~4 K and the polarized emissivity difference increases monotonously to ~0.2 at the EIA of 50°. The complex surface parameters and temporal variabilities impinge on the uncertainties of the land polarization. The increasing soil moisture due to precipitation damps the dichroic ability of the land surface, while the frozen surface due to snowfalls in cold seasons enhances the polarization. [ABSTRACT FROM AUTHOR]

This article proposes an ultrawideband rectifier with high efficiency at wide input power range. It consists of a wideband impedance compression network (WICN) and two subrectifiers. The proposed impedance compression network (ICN) offers a more universal design method and higher design flexibility. Thus, the impedance variation of subrectifiers at wide input power range can be reduced at several frequencies. With proper setting of these frequencies, the rectifier can maintain stable, high efficiency at wideband, and wide input power range simultaneously. Besides, the proposed network can also realize impedance matching, hence saving extra matching components. The mechanism of the proposed rectifier is analyzed. For verification, a prototype is implemented and measured. The optimal efficiency of 72.2% is found at 6.5 dBm and 1.2 GHz. The prototype can maintain an efficiency beyond 70% of the peak value at frequencies ranging from 1.0 to 2.7 GHz. The relative bandwidth (91.9%) is so far the widest among the rectifiers with resistance compression networks (RCNs)/ICNs. At the operating band, the rectifier can maintain an efficiency beyond 70% of the peak at input power ranging from −6.2 to 13 dBm. The total size is as compact as $0.19\lambda \times 0.16\lambda $ at the central frequency. [ABSTRACT FROM AUTHOR]

Predicting the insulation performance of SF6 substitute gases through gas molecular structures has been a popular topic worldwide. There is a lack of research on the relationship between the critical reduced electric field and molecular structure under low pressure. The critical reduced electric field intensity and boiling temperature (BT) of gas are used as inputs to extract the important molecular structure parameters (MSPs) of gas at low pressure by using the maximum information coefficient (MIC) method. Through multivariate nonlinear fitting, the structure–activity relationship model of important MSPs of gas is established. The model is verified by the critical reduction strength and MSPs of C4F7N, CF3SO2F, and SF6 gases. The results show that the model has reliable predictive ability. In this study, the micro mechanism of gas discharge under low pressure and a dc electric field is revealed at the molecular level, and the insulation performance of gas is quantitatively predicted, providing a reference for the analysis of SF6 replacement gas performance. [ABSTRACT FROM AUTHOR]

In this letter, a quasi nondiffraction beam is designed and implemented for microwave power transmission (MPT) application. To generate a quasi nondiffraction beam, a new formula is derived to calculate the phase distribution on the metasurface (MS), and a phase shifting unit with 360° transmission phase coverage and transmission amplitude better than −3 dB is designed to achieve desired phase. The simulated and measured results demonstrate that a quasi nondiffraction beam can be generated by the proposed MS. In order to prove that the quasi-nondiffraction beam can be used for microwave power transfer, a miniaturized MPT system is built and measured. The system-level measurement results indicate that the proposed transmitting antenna helps the receiving terminal to harvest more power and improves the power transmission efficiency of the system. [ABSTRACT FROM AUTHOR]

Cycle skipping modulation (CSM) was previously demonstrated for efficiency improvement in different converters intended for photovoltaic module-level applications. Currently, galvanically isolated buck–boost converters (IBBCs) have attracted increased attention in these applications due to the uptake of dc microgrids. This article revisits the topic of CSM and applies it to a quasi-Z-source-based IBBC. Two new CSM schemes are proposed for the given converter. Power losses in components are estimated for different CSM schemes to predict efficiency improvement that could be attained. A 300-W prototype was built to verify the efficiency estimation results. The efficiency trends are the same between the theoretical estimations and experimental measurements. Converter operation was studied for two bell-shaped solar irradiance daily profiles using a solar array simulator. The converter demonstrates efficiency improvement during morning and evening hours for a sunny day and during the whole day for overcast sky conditions. [ABSTRACT FROM AUTHOR]

A fully differential transmitter front‐end with multistage power amplifiers and a 7‐bit phase shifter were implemented in a 180‐nm CMOS process. RC feedback and cross‐coupling circuits were adopted to improve the stability of the power amplifiers. For the final power stage, a four‐transistor in‐parallel architecture was used to obtain a large total gate width, while maintaining a compact size with relatively small parasitic effects. The measured saturated output power (Psat) of the fabricated transmitter chip is 21.3−22 dBm, with a system efficiency of 24%−28.2% at 5−7 GHz, and the root‐mean‐square phase and gain error are below 1.40° and 0.28 dB, respectively, with 7‐bit phase resolution. [ABSTRACT FROM AUTHOR]

Radio-frequency interference (RFI) is an increasing problem particularly for Earth observation using microwave radiometry. RFI has been observed, for example, at L-band by the European Space Agency’s (ESA’s) soil moisture and ocean salinity (SMOS) Earth Explorer and by National Aeronautics and Space Administration’s (NASA’s) soil moisture active passive (SMAP) and Aquarius missions, as well as at C-band by Advanced Microwave Scanning Radiometer (AMSR)-E and AMSR-2, and at 10.7 and 18.7 GHz by AMSR-E, AMSR-2, WindSat, and GPM Microwave Imager (GMI). Therefore, systems dedicated to interference detection and removal of contaminated measurements are nowadays a must in order to improve radiometric accuracy and reduce the loss of spatial coverage caused by interference. In this work, the feasibility of using the empirical mode decomposition (EMD) technique for RFI mitigation is explored. The EMD, also known as Hilbert–Huang transform (HHT), is an algorithm that decomposes the signal into intrinsic mode functions (IMFs). The achieved performance is analyzed, and the opportunities and caveats that this type of methods present are described. EMD is found to be a practical RFI mitigation method, albeit presenting some limitations and considerable complexity. Nevertheless, in some conditions, EMD exhibits a better performance than other commonly used methods (such as frequency binning). In particular, it has been found that EMD performs well for RFI affecting the $< 25\%$ lower part of the intermediate frequency (IF) bandwidth. [ABSTRACT FROM AUTHOR]

The temperature spike or sparking is vital to the catalytic effect with metallic powders in microwaves, but the mechanism is still unclear. In this article, the local field enhancement (LFE) of periodical metallic powders in microwaves is studied. It shows that microwaves can get through the separations among metallic powders with the LFE, which provides a preliminary understanding of the temperature spike or sparking among metallic powders. First, for simplicity, metallic powders are simplified to 2-D periodical metallic bars, which can be analyzed by the transmission line model and full-wave simulations. When the incident electric field is perpendicular to the separations among metallic bars, the electric field can be compressed. Specifically, even with the volume fraction of 99% metals, microwaves can pass through the separations well with intensive LFEs. Then, metallic powders are simplified to 3-D periodical spherical metallic powders. In this case, microwaves propagate at the slow wave mode with the LFE. Finally, the proposed models are validated by measuring reflectivity and observing the discharge in neon (Ne) gas at atmosphere in a rectangular waveguide at the TE10 mode. This work provides a way of controlling LFEs for enhancing reaction reactivity and creating plasma. [ABSTRACT FROM AUTHOR]

Early diagnosis is currently the most effective way of saving the life of patients with neuropsychiatric systemic lupus erythematosus (NPSLE). However, it is rather difficult to detect this terrible disease at the early stage, due to the subtle and elusive symptomatic signals. Recent studies show that the $^{1}$ H-MRS (proton magnetic resonance spectroscopy) imaging technique can capture more information reflecting the early appearance of this disease than conventional magnetic resonance imaging techniques. $^{1}$ H-MRS data, however, also presents more noises that can bring serious diagnosis bias. We hence proposed a noise-immune extreme ensemble learning technique for effectively leveraging $^{1}$ H-MRS data for advancing the early diagnosis of NPSLE. Our main results are that 1) by developing generalized maximum correntropy criterion in the kernel extreme learning setting, many types of non-Gaussian noises can be distinguished, and 2) weighted recursive feature elimination, using maximal information coefficient to weight feature’s importance, helps to further alleviate the bad impact of noises on the diagnosis performance. The proposed method is assessed on a publicly available dataset with 97.5% accuracy, 95.8% sensitivity and 99.9% specificity, which well demonstrates its efficacy. [ABSTRACT FROM AUTHOR]

The freeze-thaw (FT) status of soil regulates ecological and hydrologic processes and is, therefore, a vital component of land surface models. This study utilizes a hidden Markov model (HMM) to retrieve surface FT status from L-band [Soil Moisture Active Passive (SMAP)] and Ka-band [Advanced Microwave Scanning Radiometer (AMSR)] satellite microwave brightness temperatures in cold-constrained lands north of $45 ^\circ \text{N}$. The HMM, parameterized on a per-gridcell basis such that there are two possible states and emissions probabilities are assumed to be a two-component Gaussian Mixture, produces the posterior probability (a continuous variable between 0 and 1) that the surface is frozen given the radiometer input. HMM classification accuracy, averaged over five core validation networks, is acceptable (Ap > 80%) when judged against in situ air and soil temperature measurements from individual validation sites and is comparable to that of current FT products that produce a discrete state. Patterns in performance across variable land class, open water fraction, and elevation are assessed from 91 sparse network weather stations within 87 gridcells in the domain. The resulting satellite data record provides a continuous variable estimate of the daily probability of frozen conditions over northern land areas experiencing widespread thawing of permafrost and a shrinking frozen season due to global warming. [ABSTRACT FROM AUTHOR]

Transmitted and received power must be controlled quickly and accurately to comply with government regulations, minimize interference, and optimize power consumption. Microwave power detectors (PDs) are critical building blocks employed in applications such as integrated circuit tests and measurements, wireless communication, and automatic-gain-control (AGC) circuits to monitor signal power level. PDs are utilized as received signal strength indicators (RSSIs) to adjust the gain of the intermediate frequency/RF signal via an AGC circuit. They are also used in mobile terminals to monitor the transmitted power, thereby optimizing power consumption. Two popular methods employed to measure the power signal level are root mean square (RMS) value and peak value. Peak detectors capture the input’s peak power to provide power information, whereas the RMS PD provides information about the average power. shows a conventional block diagram of a microwave PD employed in an RF transmitter. The directional coupler is used to couple the output signal from the power amplifier to a PD. The signal is then converted to a dc voltage that the power controller utilizes to change the power amplifier’s gain, thereby improving the transmitter’s linearity. [ABSTRACT FROM AUTHOR]

This letter presents a transition from a top layer grounded coplanar waveguide (GCPW) to an inner layer air-filled substrate-integrated waveguide (AFSIW). Such type of transition is crucial for the interconnection of top layer surface-mounted radio-frequency integrated circuits (RFICs), toward the integration of complete microwave and millimeter-wave systems taking advantage of the low-cost and high-performance AFSIW technological platform. To fulfill the new space application needs, the proposed transition has been developed in the satellite downlink Ka-band ranging from 27.5 to 31 GHz. The structure is detailed with design guidance. For experimental evaluation, a back-to-back prototype has been fabricated and measured. In the operating frequency range, the proposed transition achieves a simulated and measured insertion loss (IL) as low as 0.135 ± 0.015 dB and 0.3 ± 0.18 dB, respectively. [ABSTRACT FROM AUTHOR]

Arctic sea-ice thickness and salinity retrievals are simulated to explore the performance of nadir-observing microwave radiometry operating with up to 16 frequency channels in the 0.5–2-GHz frequency range. A radiative transfer model is used to create lookup tables of the circularly polarized thermal emissions of first-year (FY) and multiyear (MY) sea ice, and the performance of two distinct retrieval methods is examined. The first method retrieves only sea-ice thicknesses, while the second retrieves both ice thickness and ice salinity. Retrieval errors are simulated for both FY and MY sea ice as a function of ice thickness, salinity, and temperature to investigate the impact of radiometric uncertainty, the frequency channels used, and any errors in ancillary information. To gain further insight into Arctic scale retrieval performance, a simulated brightness temperature dataset is produced for Arctic sea ice for the period October 2020–March 2021 using sea-ice thicknesses from the SMOS-CryoSat-2 algorithm. Compared to existing sea-ice thickness retrievals obtained from 1.4-GHz microwave radiometers, the results demonstrate that 0.5–2-GHz radiometry can achieve higher sensitivity to a sea-ice thickness within the range 0.5–1.5 m for FY sea ice and enable the retrieval of multiple sea-ice parameters (thickness and salinity) simultaneously. [ABSTRACT FROM AUTHOR]

Low frequency primary calibrations of condenser microphones are the basis of accurate measurement of low frequency sound and infrasound. Prior arts on the primary phase calibrations differ greatly, simultaneous primary amplitude and phase calibrations are rarely seen. Recently, two infrasonic sensitivity models of condenser microphones based on the pistonphone technique, for the vent immersed in sound field and outside are derived. The relevant models can explicitly characterize the influence of pistonphone, microphone and environment on the voltage output and sensitivity of the microphone. On this basis, simultaneous primary amplitude and phase calibration tests are evaluable. Based on adequate performance tests of the designed laser pistonphone, this paper carries out in-depth primary microphone calibrations. The calibrated infrasonic amplitude and phase sensitivities are in good agreement with theoretical results, thus proves their values to reveal and quantify the influence of various factors on the calibration results based on the pistonphone technique. [ABSTRACT FROM AUTHOR]

In high-speed digital systems containing dense digital devices, such as microcontrollers, microprocessors, graphic processors, network processors, switching hubs, field-programmable gate arrays, and application-specific integrated circuits (ICs), the interconnects are no longer transparent. This has been the case for systems since clock frequencies rose above 50 MHz, which includes just about all digital products used today. Unless special care is taken in their design and implementation, a high-speed system will fail due to one or more problems generally grouped into the families of signal integrity (SI), power integrity (PI), or electromagnetic interference (EMI). [ABSTRACT FROM AUTHOR]

Microwave-induced thermoacoustic (TA) imaging, combining high microwave contrast with high ultrasonic resolution has the potential to revolutionize applications such as continuous healthcare monitoring, point-of-care imaging, and biometric authentication. However, the size, cost, and integration of a high-power microwave transmitter is a key bottleneck in making TA imaging truly portable, affordable, and ubiquitous. Toward that end, this work presents a compact 4.9-GHz pulsed power amplifier (PA) with a 4.87-mm2 active area implemented in a 55-nm BiCMOS technology, operating in a duty-cycled mode and achieving 37.3-dBm peak output power—the highest demonstrated peak power in PAs fabricated on a silicon substrate with deep submicron CMOS integration. We also reconstruct the first known high-fidelity TA images of tissue phantoms using an integrated silicon PA. [ABSTRACT FROM AUTHOR]

This article proposes a novel surrogate-assisted multistate tuning-driven electromagnetic (EM) optimization technique to address the challenges of microwave tunable filter design with multiple tuning states. The desired multiple tuning states are satisfied simultaneously using the proposed surrogate-assisted technique. The proposed surrogate model is composed of several subsurrogate models. Each subsurrogate model is developed to perform the optimization for each tuning state. The subsurrogate models share the same values of nontunable parameters and possess different values of tunable parameters. The overall surrogate model is developed to find a single set of optimal solutions for nontunable parameters and multiple sets of optimal solutions for tuning parameters simultaneously. Parallel computation scheme is exploited to generate the training samples for establishing the proposed surrogate model. Furthermore, a new trust-region updating formulation specifically for multistate tuning is proposed to improve the convergence of the proposed optimization algorithm. Using the proposed optimization technique, different tuning states are considered together and optimized simultaneously. The values of nontunable design parameters are constrained by all tuning states and consequently there is a higher chance that more suitable solutions can be found to satisfy all the desired tuning states simultaneously. The proposed technique for the tunable filter design with multiple tuning states has a better capability of avoiding local minima and can reach the optimal solution more effectively in comparison with the existing optimization method. Two microwave examples are used to validate the proposed technique. [ABSTRACT FROM AUTHOR]

This letter presents a novel method to implement a 10–20 GHz low‐noise amplifier (LNA) with simultaneous noise and input matching performance. That is, the Mille effect caused by the gate‐drain parasitic capacitance Cgd is eliminated by converting the succeeding‐stage impedance into the required load using frequency‐dependent negative feedbacks and a π‐type network. The corresponding analytical equation is also derived for the first time. To verify the feasibility, the circuit is fabricated via a 0.15‐μm GaAs p‐HEMT process with a compact size of 0.9×1.9 mm2. The measured results show that the proposed LNA features a peak gain of 26.1 dB, a minimum noise figure of 1.08 dB, and an input return loss of less than −15.8 dB. [ABSTRACT FROM AUTHOR]

This letter proposes an ultra‐wideband switched T‐type phase shifter, which covers the whole X/Ku band. The proposed switched T‐type phase shifter integrates a switched filter compensation structure, achieving a flat relative phase shift in broadband, which the conventional one cannot acquire. In addition, the designed T‐type phase shifter can further reduce the phase error and improve the phase shift capability with a phase shift greater than 45°. Employing the proposed architecture, a 90° T‐type phase shifter is designed and fabricated in 0.15‐μm GaAs pHEMT process. The measured results show that the proposed T‐type phase shifter achieves a stable 90° phase shift at 8 to 18 GHz with a phase error of less than ±2°, and an insertion loss (IL) of 2.4 to 4.2 dB. And the chip size of the switched T‐type phase shifter is 0.62 × 0.75 mm2. Thanks to its good performance, the proposed T‐type phase shifter is very suitable for various radar and satellite communication systems. [ABSTRACT FROM AUTHOR]

This paper presents a general overview of substrate integrated transmission lines, from the perspective of historical background and progress of guided-wave structures and their impacts on the development of microwave circuits and integration solutions. This is highlighted through a technology roadmap involving the categorized five generations of microwave circuits. In particular, the substrate integration technologies are reviewed and discussed with focus on technical features, design highlights, component developments, structures evolution, and systems integration. A number of examples are presented to showcase some of the selected milestone research and development activities and accomplishments in connection with substrate integrated transmission line technologies, with particular focus on substrate integrated waveguide (SIW) techniques. Practical applications and industrial interests are also presented with key references and technical results, which show more and more product developments in the end-user sectors. It can be found that the popularity of SIW techniques is closely related to the achieved seamless integration of planar and non-planar structures into a unified design space, thereby allowing the possibility of combining major advantages of all the structures while alleviating their potential drawbacks. The future perspectives of the substrate integration technology are discussed through five major research directions, which suggest potential impacts in the development of future generations of circuits and systems such as system-on-substrate (SoS).

Moving models, such as translation, rotation, and other motion modes, are widely applied to improve the microwave heating uniformity. However, due to a variety of motion modes, the deformation of mesh, including discontinuity, crossing, and winding, usually occurs in the process of microwave heating calculation. It is a great challenge to numerical simulation of moving samples because of the lack of a common calculation method. In this article, a novel inheritance algorithm, which inherits both the grid and temperature distribution of the sample, can be used to calculate arbitrary moving models of microwave heating process. It is adopted to inherit the grid and temperature distribution in the finite element method to ensure that each temperature calculation result can perfectly correspond to the temperature value of these mesh nodes. By building a 3-D mathematical model of translation, swing, and rotation, the coupling process of electromagnetic field and thermal phenomena in microwave heating was performed and the proposed method was clearly illustrated. Finally, the calculated results are consistent with the experimental results, confirming the accuracy of the algorithm. Compared with the conventional algorithm, the proposed algorithm has a higher precision and practically and can be used to simulate microwave heating of arbitrary motions. [ABSTRACT FROM AUTHOR]

Inferring appropriate information from large datasets has become important. In particular, identifying relationships among variables in these datasets has far-reaching impacts. In this article, we introduce the uniform information coefficient (UIC), which measures the amount of dependence between two multidimensional variables and is able to detect both linear and non-linear associations. Our proposed UIC is inspired by the maximal information coefficient (MIC) [1].; however, the MIC was originally designed to measure dependence between two one-dimensional variables. Unlike the MIC calculation that depends on the type of association between two variables, we show that the UIC calculation is less computationally expensive and more robust to the type of association between two variables. The UIC achieves this by replacing the dynamic programming step in the MIC calculation with a simpler technique based on the uniform partitioning of the data grid. This computational efficiency comes at the cost of not maximizing the information coefficient as done by the MIC algorithm. We present theoretical guarantees for the performance of the UIC and a variety of experiments to demonstrate its quality in detecting associations. [ABSTRACT FROM AUTHOR]

Miniaturized microwave cavities constructed by the parallel-plate waveguide (PPW) becomes one of the main propagation pathways of the radio-frequency interference (RFI) in 3-D integrated circuits. It is still challenging to suppress RFI in the practical cavities, where the space is extremely constrained. In this work, the working mechanism and design method of the noise suppression sheet (NSS) is quantitatively studied, serving as an efficient approach to suppress RFI within an electrically small size in these microwave cavities. The analysis is based on the dispersion relationship derivation of the NSS-loaded PPW structure. Both the derived formulas and the numerical study reveal that the imaginary part of the permeability, that is, $\mu _{i}$ , of the NSS plays a key role in increasing the reflection and attenuation loss, and thus obtaining a high RFI suppression level. Further study indicates even when the NSS’s profile is lower than 10% of the cavity’s height and the length is lower than $0.1\lambda _{0}$ , its suppression level up to 10 dB can be well accomplished, which is deemed difficult to achieve by using conventional methods. Moreover, this method is, respectively, applied in three practical engineering scenarios for the RFI suppression, that is, heatsink package above a chip, power distributed network (PDN), and flexible circuit. Good agreement is observed between the measurement results and the simulated ones, which confirmed the efficacy of our quantitatively developed NSS. The proposed method is promising for broad industrial applications, such as tiny chip packages, multi-channel systems, and flexible electronics. [ABSTRACT FROM AUTHOR]