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We present a salient object detection method in this paper. It uses a lightweight network based on multi-scale information aggregation (MIA) module and bidirectional cross-stage feature fusion (BCF2) module to speed up the reasoning process. Besides, it designs a stepwise coupling optimization strategy based on positive-incentive pseudo label to alleviate the miss detection rate for small objects and the false detection rate for big objects. It is worth noting that the positive-incentive pseudo label generation mechanism can increase the ratio of salient pixels in small objects to alleviate the severe category imbalance problem, while the stepwise coupling optimization strategy can avoid the misguidance of pseudo label to big objects. In addition, the experimental results demonstrate that our method is fairly efficient, its frame rate in reasoning phase reaches 275.6 FPS on NVIDIA RTX3080 GPU when the input resolution is set to $336\times 336$ .

In this study, a highly efficient harmonic suppressed dual-band power amplifier (PA) for harmonic radar systems is proposed. The proposed PA incorporates a harmonic-controlled dual-band matching network (HCDMN) comprising $\lambda $ /4 open stubs at the second-harmonic frequencies and series transmission lines. The HCDMN can effectively suppress unwanted second-harmonic signals and control the fundamental and second harmonic impedances to operate in continuous class-F1 mode at two operating frequencies. The implemented PA has dimensions of 75.3 mm $\times 54.9$ mm. Measurement results demonstrate that the PA achieves an exceptional performance, with peak drain efficiencies (DEs) of 81.5 and 71.8 %, saturated output powers of 40.3 and 41.9 dBm, and second harmonic levels of −75.6 and −49.4 dBc at 2.3 and 3.35 GHz, respectively. Furthermore, the DEs remain above 65 % in the two frequency bands of 2.2–2.5 and 3.3–3.45 GHz.

The DC microgrid with energy storage cells has strong stability, simple control, and a convenient power supply for DC loads, increasingly becoming the grid-connected structure of distributed generation systems. This paper presents an isolated high voltage gain soft-switching dc-dc converter suitable for DC microgrid applications. The converter comprises a dual-switch quasi-z-source network, multiplier voltage cell, and transformer. It has advantages such as high voltage gain, zero voltage switching (ZVS) of switches, zero voltage zero current switching (ZVZCS) turn-on and turn-off of diodes, and low input ripple current. The converter can achieve high voltage gain with an appropriate duty cycle and transformer turns ratio, reducing leakage inductance of transformer, which decreases the power loss and voltage spike of switch. Soft-switching of active devices increases the efficiency and decreases the output voltage ripples of the converter. The steady-state characteristics of the converter, voltage and current stress of components, the efficiency of the converter, and the selection of converter parameters are analyzed in detail. Finally, a 200 W experimental prototype is built in the laboratory for experimental verification, and the experimental results are consistent with the theoretical analysis.

This paper presents a design method for a watt-level high-efficiency broadband power amplifier (BPA) with a generalized parallel-circuit (PC) Class-E model. A combination of the single-reactance compensation technique (S-RCT) and Chebyshev low-pass (LP) impedance matching network (MN) is used for achieving PA’s broadband characteristics. The analytical expression of the operation and power loss mechanisms of PC Class-E PA, which includes the effects of a finite DC-feed inductance, transistor on-resistance, and a broadband MN, is elaborated. As an example, a highly-efficient broadband PC (BPC) Class-E PA operating at 12 V drain supply voltage is implemented and verified experimentally. The designed PA exhibits high-efficiency characteristics of 82.15%-86.3% drain efficiency (DE) and 36.92-38.57 dBm output power ( $P_{out}$ ) with 19.95-23.11 dB power gain in the band from 7 MHz to 9.4 MHz. The measured results show good agreement with the theoretical and simulated results.

A novel dual-port multiple-input-multiple-output (MIMO) antenna arrangement is introduced for attaining quasi-omnidirectional circular polarization (OCP) towards device-to-device (D2D) integrated sensing and communications (ISAC) deployment in sixth generation (6G) networks. The antenna architecture comprises of three dielectric laminates arranged one below/above the other with each substrate juxtaposed to its counterpart by the air cavity. The upper laminate encompasses solitary element frequency selective surface (FSS) etched on both fronts. Impedance matching transmission lines and partly reactive impedance surfaces (RIS) were printed on the top and bottom region of the middle substrate, respectively. The lower laminate features microstrip feed lines on the top side and semi ground planes on the bottom. The MIMO antenna was made up of two ports and fed through proximity coupling from the opposite ends of the middle substrate’s top surface to resonate with a −10 dB impedance bandwidth (I-BW) of $\sim $ 35%. The partial RIS enabled $>$ 20 dB of isolation between the ports while the air cavities between the laminates contributed to achieve a realized gain of $>$ 7 dBi. The antenna occupies $1.2\lambda \times 1.2\lambda $ footprint and $0.1\lambda $ height at 12 GHz to exhibit quasi-OCP in the azimuth plane with axial ratio (AR) of < 3 dB and efficiency of $>$ 90%. The envelope correlation coefficient (ECC), diversity gain, specific absorption rate (SAR), and power density (PD) at the band of interest were < 0.1, $\sim $ 10 dB, < 1.6 W/kg, and < 10 W/ $\text{m}^{2}$ , respectively. The results of the Ansys HFSS simulations and the measurements taken within the anechoic chamber exhibited good agreement. In contrast to state-of-the-art quasi-OCP antennas operating in the 12 GHz spectrum, the novelty of the proposed MIMO antenna includes a straightforward and compact configuration that is integrated synergistically to provide reasonably high gain and efficiency values.

This paper presents the design of a buck converter for use in low-power system-on-chips (SoCs) with a ripple voltage small enough to directly power sensitive analog circuits without the help of low-dropout voltage regulators (LDOs). To minimize the ripple voltage while maximizing the converter’s light-load efficiency, we employ a pulse-frequency modulation (PFM) scheme and a fast duty-cycled comparator to control the converter’s output voltage. The duty cycling of the comparator, automatically performed by the Sleep State Controller (SSC), helps improve the light-load efficiency by 48%. Fabricated in a 0.18- $\mu \text{m}$ CMOS process with an active area of $0.42 ~\mathrm {mm}^{2}$ , the proposed low-ripple buck converter achieves the ripple voltage of $1.6~ \mathrm {mV_{pp}}$ and the overall efficiency of higher than 74.4% over the load current range from $1.2 \mu \text{A}$ to 1.8 mA.

A high infrared-to-green conversion efficiency laser is demonstrated by extra-cavity frequency-doubling of a master oscillator power amplifier (MOPA) laser. The oscillator is a diode-side-pumped acousto-optic Q-switched Nd:YAG laser at 1064 nm with an average output power of 38.2 W and a beam quality factor M2 = 1.15, operating at a 2 kHz repetition rate and a 38.3 ns pulse duration. After a dual-rod double-pass amplifier, the fundamental seed power is amplified to 89.4 W with the beam quality of M2 = 1.41 and pulse duration of 56.4 ns. Using a type I lithium triborate (LiB3O5, LBO) crystal for second-harmonic generation (SHG), an average power of 67.4 W at 532 nm is generated with a beam quality factor of 1.31, operating at 41.8 ns of pulse duration. The corresponding frequency doubling efficiency is as high as 75.4%, which is, to the best of our knowledge, the highest doubling efficiency reported ever for 532 nm source by an extra-cavity SHG laser system.

Metasurfaces have been widely used in the manufacture of various optical components in recent years. Based on all-dielectric metasurfaces, we proposed broadband, high-efficiency (over 83%) quarter-wave plates (QWP) and half-wave plates (HWP), respectively. The structure of the HWP we designed is equivalent to the superposition of two QWPs. The proposed QWP and HWP have high transmission efficiency, with bandwidths of 1376–1624 nm and 1411–1584 nm, respectively. Furthermore, based on the three-layer all-dielectric metasurfaces structure, we proposed a reversible bifunctional metasurface, which can realize the function of QWP and the effect of light deflection. This work may be conducive to the miniaturization and integration of polarization conversion devices.

In this brief, a compact high-efficiency broadband rectifier with an extended range of input power is proposed for the applications in wireless energy harvesting (EH). In the rectifier, a coupled transmission line is connected in series with a Schottky diode to compensate its capacitive reactance, compress its impedance variation when the frequency or input power varies. The coupled transmission line facilitates the impedance matching circuit and reduces the insertion loss. High RF-dc conversion efficiency will be achieved consequently. A rectifier is fabricated and measured based on analysis and simulation on the coupled transmission line. The measured results show a good agreement with the simulation results. The rectification efficiency of the rectifier is over 70 % from 1.6 to 2.8 GHz (a bandwidth of 54.5%) with the input power range from 11 to 14 dBm. The efficiency remains above 50% from 1.5 to 2.85 GHz with input power from 5 to 18 dBm,and over 40% within 1.7–2.8 GHz when the input power decreases to 0 dBm. The maximum measured efficiency is 78.63% at an input power of 16 dBm. [ABSTRACT FROM AUTHOR]

A high-efficiency wideband double-layer transmitarray antenna (TA) using miniaturized array elements is proposed in the study for millimeter-wave (mm-Wave) applications. The transmitarray consists of 484 dual-polarized elements. Each element is composed of only two layers of identical modified Jerusalem crosses printed on a dielectric substrate. Additional stubs are used for size reduction, leading to a compact size with a periodicity of only $0.44 \lambda _{0}$. It contributes to a high aperture efficiency for the proposed TA. TA is designed, fabricated, and measured. It achieves a peak gain of 28.67 dBi at 31 GHz and a high aperture efficiency of 44%–61.3% within the 1 dB gain bandwidth, which is 10.3% (29.5–32.7 GHz) in the measurement. The proposed dual-polarized double-layer TA demonstrates simplified design complexity, reduced thickness and mass, and lower cost compared with the conventional TAs. It also exhibits high radiation gain and high aperture efficiency. [ABSTRACT FROM AUTHOR]

A high-efficiency dual-band dielectric filtering antenna based on three parallel placed dense dielectric strip resonators (DDSRs) is proposed for the self-filtering property. That means both the filtering responses of the two bands are only determined by the three DDSRs themselves without extra filtering circuits. The even-mode coupling of the TM1δ mode (TM3δ mode) between the middle and two-sided DDSRs is used to form the first (second) radiation band, while the odd-mode coupling contributes one radiation null at the upper edge of each radiation band. Therefore, the proposed dual-band dielectric antenna exhibits relatively high total efficiency benefited from the self-filtering characteristic. Additionally, the presented one without extra filtering circuits obtains the features of low profile, enhanced bandwidth, and gain. For test and verify, a prototype was measured at 7.7 and 13.35 GHz with the fractional bandwidths of 11.4% and 4.8%, the peak gains of 7.65 and 10.5 dBi, and the total efficiencies of 89% and 87%, respectively. Radiation nulls are generated at 8.5 and 13.8 GHz, respectively. [ABSTRACT FROM AUTHOR]

In this letter, a new technique based on passive two-dimensional (2-D) Huygens metasurface (HMS) is investigated to control the beam of a linear polarized horn antenna. In this proposed method, the spherical electromagnetic waves inside the horn are expanded to plane wave terms in spectral-domain for dominant mode. Then, using these plane waves, enforcing two conditions of local power conservation and local impedance equalization, the required surface electrical and magnetic impedance equivalent to HMS are calculated. Using this method, two different structures are designed and simulated for the deviation of the main beam on the H-plane and creating an orbital angular momentum wave at 10 GHz. Then, one sample is fabricated and measured. The results show improvement in aperture efficiency in comparison to similar works. [ABSTRACT FROM AUTHOR]

A linear polarization matching with fixed linear-polarized conical beam antenna has the superiority in some applications compared with the radially linear-polarized conical beam antenna. In this communication, a transmitarray illuminated by a pencil beam source to obtain conical beam with fixed linear polarization (FLP) is presented. The pencil beam source is also used to obtain the conical beam with circular polarization (CP). To achieve good circumferential symmetry, the transmitarray elements are distributed on rings. And the dimensions of the double-ring elements on the surface of the transmitarray are adjusted to compensate for the phase delay of the wave from the horn phase center and form a desired phase distribution on the transmitarray aperture. Based on this mechanism, three different cone angles of the FLP conical beam transmitarray are designed. A transmitarray illuminated by a horn to obtain conical beam with the radius of $4.25\lambda $ has been designed and fabricated. The simulated results show that its gain is higher than 9 dBi at the designed frequency 12.5 GHz with a cone angle of 40°. Measured results agree reasonably well with the simulated ones. The conical beam antenna with CP has also been simulated and designed using the circular polarized feed source illumination. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a novel lateral-zigzag PN junction for silicon modulator working in C and O bands. The designed PN junction exhibits characteristics of large bandwidth, high modulation efficiency, and easy fabrication. For demonstration, it is embedded in a 220 nm silicon rib waveguide on a 2 $\mu \text{m}$ thick buried oxide layer to form a micro-ring modulator. The measured 3 dB electro-optic bandwidth of the fabricated modulator is 42 GHz while the resistor-capacitor (RC) bandwidth is measured and calculated to be 174 GHz. Clear and open eye diagrams are obtained for 50 Gb/s non-return zero (NRZ) and 100 Gb/s four-level pulse amplitude modulation (PAM4) signals. The modulation power consumption is only 14 fj/bit. [ABSTRACT FROM AUTHOR]

Inspired by the recent progress of metasurfaces, a novel wideband and high-efficiency electronically reconfigurable transmitarray (TA) is presented that can enable two-dimensional (2-D) beam steering and multiple beam mode switching in a digital manner. The proposed unit cell consists of a reconfigurable anisotropic metallic resonator, which locates between a pair of orthogonally oriented subwavelength metal gratings. One-bit phase quantization is obtained by controlling the ON or OFF state of two positive-intrinsic-negative (p-i-n) diodes integrated on the anisotropic metallic resonator layer. To choke the radio frequency (RF) signal effectively, a bias layer is connected by the metallic via hole to the center of the resonator, where the electric field is minimal. The simulated results show that the proposed unit cell can achieve a low insertion loss of 1 dB from 9.3 to 10.9 GHz for two phase states. Then, the radiation performance of a 10 $\times\,\,10$ element array fed by a pyramidal horn antenna is theoretically calculated, simulated, and measured. The measured maximum gain is 19.1 dBi at 10.0 GHz with an aperture efficiency of 25.8% and a 3 dB gain bandwidth of 15.9%. The measured results demonstrate the 2-D beam scanning capability within the 50° range. [ABSTRACT FROM AUTHOR]

A high-efficiency W-band 12-way power combiner system based on the TM01 mode in a circular waveguide has been presented in this study. It is a radial structure composed of three elements: a circular waveguide TM01-mode transducer, an isolated 12-way radial power combiner, and amplifier modules. The measured passive combining efficiency is observed to be greater than 89.5% over the range of 85–100 GHz. The isolation between the inputs is better than 10 dB, with a maximum back-to-back return loss of 13 dB. By using 12 GaN monolithic microwave integrated circuit (MMIC) 2-W power amplifiers, the active combiner system produces a maximum power output of up to 22 W with an average combining efficiency of 81.7% within the band of 92–97 GHz. The power-added efficiency within the operating band has been measured to be up to 20.8%. [ABSTRACT FROM AUTHOR]

In this article, a novel high-efficiency harmonic beamforming technique based on time-modulated arrays (TMAs) with multistate time modulators is proposed. The typical single-sideband TMAs suppress the image harmonic components in the radio frequency (RF) channel, which means low power conversion efficiency, large power consumption, and a major heat dissipation problem. To circumvent these constraints, we present a novel phase modulation (PM) waveform with a linear phase that can be easily constructed using multiple fixed delay lines and a pair of single-pole-multi-throw (SPMT) RF switches. This fundamental PM waveform enables the creation of uniform radiation patterns. Furthermore, two complementary methodologies are proposed for synthesizing more advanced radiation patterns that need nonuniform array weights. One method is to change the linear phase slope of PM waveforms that exhibit sideband radiation but have 100% feeding network efficiency. The other option is to investigate hybrid amplitude and PM (HAPM) waveforms, which suffer from inefficiencies in the feeding network but do not exhibit sideband radiation. Besides, the comprehensive efficiency evaluation formulas have been effectively derived. Simulations have been done to verify its effectiveness. [ABSTRACT FROM AUTHOR]

In the 3-D density inversion calculation of gravity data, the entire subsurface space is discretized into rectangular prisms, and the density value of each prism is calculated. However, the method of dividing the entire space often results in invalid calculations. In this study, we proposed a highly efficient density inversion method using a locally adaptive unstructured mesh. In this method, the inversion scope is reduced by using the feature that the zero value of the tilt angle method corresponds to the edge of the field source. In addition, the local inversion area is divided by unstructured meshes, which can better represent irregular geological bodies and undulating terrain. In the proposed method, the size of the grid cells is changed according to the value of the tilt angle to reduce the amount of mesh, which reduces the computational complexity and improves the computational efficiency. In addition, by introducing a volume weighting function, the sensitivity of grid cells of different sizes can be balanced. Through synthetic modeling experiments, we verified that the locally adaptive unstructured mesh method can improve the efficiency and accuracy of inversion, flexibly deal with undulating terrain, and obtain the distribution features of irregular bodies. We applied this method to gravimetric data of the North Qinling region of the Shaanxi province, which clearly shows the spatial distribution information of five high-density geological bodies, and the depth range of ore bodies formed is from 240 to 1481 m according to our inversion results. [ABSTRACT FROM AUTHOR]

The availability of energy is one of the major hindrances to unlocking the massive potential of electronic devices. Powering a highly connected network of devices requires multiple access and a wireless power transfer (WPT) solution that is scalable and capable of maintaining a constant power flow regardless of reconfiguration (mutability) and electromagnetic environment (power flow selectivity). In this paper, we present a framework for the implementation of code division multiple access wireless power transfer (CDMA-WPT) for enabling WPT among multiple transmitters and multiple receivers simultaneously. CDMA-WPT maintains power flow selectivity and is easily scalable. An inverter/rectifier topology is presented for the hardware implementation of CDMA-WPT. A design process for practical co-design of high-performance hardware and obtaining a code set is also presented. We demonstrate the hardware implementation of CDMA-WPT using two transmitters and two receivers maintaining a nearly constant 5W operation with nearly 75% dc-dc efficiency, and four transmitters and four receivers maintaining a constant 4W operating with greater than 70% dc-dc efficiency. This paper is accompanied by a video hardware demonstration in real-time the difference between using orthogonal codes in CDMA versus conventional single-frequency WPT using 4 transmitter-receiver pairs; conventional single-frequency WPT shows up to a 82% deviation from the intended transfer power as opposed to 8.1% for orthogonal codes in CDMA.

In this article, a high-efficiency broadband millimeter-wave (mm-Wave) integrated power amplifier (PA) with a low-loss slotline-based power combing technique is proposed. The proposed slotline-based power combiner consists of grounded coplanar waveguide (GCPW)-to-slotline transitions and folded slots to simultaneously achieve power combining and impedance matching. This technique provides a broadband parallel–series combining method to enhance the output power of PAs at mm-Wave frequencies while maintaining the compact area and high efficiency. As a proof of concept, a compact four-to-one hybrid power combiner is implemented in a 130-nm SiGe BiCMOS back-end-of-line (BEOL) process, which leads to a small die area of 126 $\mu \text{m}\,\,\times $ 240 $\mu \text{m}$ and a low measured insertion loss of 0.5 dB. The 3-dB bandwidth is over 80 GHz covering the whole G-band (140–220 GHz). Based on this structure, a high-efficiency mm-Wave PA has been fabricated in the 130-nm SiGe BiCMOS technology. The three-stage PA achieves a peak power gain of 30.7 dB, 3-dB small-signal gain bandwidth of 40 GHz from 142 to 182 GHz, a measured maximum saturated output power of 18.1 dBm, and a peak power-added efficiency (PAE) of 12.4% at 161 GHz. The extremely compact power combining methodology leads to a small core area of 488 $\mu \text{m}\,\,\times $ 214 $\mu \text{m}$ and an output power per unit die area of 662 mW/mm2. [ABSTRACT FROM AUTHOR]

In this article, a slot array with double-layered full-corporate-fed distribution network by ridge gap waveguide (RGW) in the G-band is presented. The array antenna proposed in this article contains 16 × 16-element radiation slots fed by air-filled ridge gap waveguide distribution network that achieves high-efficiency. Gap waveguide technology avoids the demand for perfect electrical contact in millimeter waves, therefore the expensive diffusion bonding and the laser welding processes are not demanded. Moreover, the high-accurate Computerized Numerical Control (CNC) machining is applied for the fabrication. Due to the limited layout space for the distribution network, two types of universal stepped cavity power dividers are presented in this article. The proposed array antenna is fed by a standard WR-5 waveguide at the bottom. Furthermore, the tested outcomes show that the proposed 16×16-element array has a gain larger than 30 dBi with over 50% antenna efficiency in the frequency range of 155-171 GHz.

This paper proposes two permanent magnet vernier machines (PMVM) operation modes, for wide-speed and high efficiency operation. In mode-1, the machine operates as a conventional PMVM with a wye connected stator winding mode. In mode-2, the machine stator winding is switched to a wye-delta winding mode. Contrary to the existing dual-inverter PMVM topology with two additional bidirectional thyristor switches, the proposed topology utilizes a single inverter with six additional bidirectional thyristor switches to change mode. A theoretical discussion of the proposed idea is further verified via finite element analysis (FEA) simulations. The basic electromagnetic characteristics, such as the flux linkage, back electromotive force, torque, and phase voltages of the machine are investigated using wye and wye-delta stator winding configurations, and subsequently, compared with the existing topology that used a dual-inverter PMVM. The FEA results show that the proposed PMVM has low over-all losses, consequently resulting in improved efficiency compared to the existing topology. The speed increases by almost 9 times using the proposed single-inverter PMVM. Transient analysis using FEA is also conducted in this paper.

In this communication, an $S$ -band wide-bandwidth and wide-beamwidth full-metal circularly polarized (CP) cavity-backed slot antenna is proposed. A pair of triangular prisms placed at the corners of the cavity is introduced to produce TE101 and TE011 modes with orthogonal electric fields. These two modes are used to achieve the CP radiation and radiate the energy through a single-circular slot. By simultaneously varying the prisms’ size and slot radius, the axial ratio (AR) bandwidth (ARBW) improves. The ARBW is further improved by replacing the circular slot with an elliptical slot. As a result, the ARBW increases from 1.0% to 10.3% without complicating the antenna structure and without enlarging the antenna size. Besides, the antenna still operates at two degenerate modes to introduce stable radiation gain and pattern. In addition, the proposed CP slot antenna features a wide ARBW. The final measurement shows that the proposed CP antenna can achieve a 9.5% bandwidth, a stable gain of 7.65 dBic ± 0.15 dBic, and higher than 140° ARBWs in a wide frequency range. The peak total radiation efficiency and aperture efficiency are about 97% and 91%, respectively. [ABSTRACT FROM AUTHOR]

This article presents a 2.4 GHz and high-efficiency wireless power receiver (Rx) integrated with a low-power transmitter (Tx) for wireless charging of the Internet-of-Things (IoT) or wearable devices. A single pole double throw (SPDT) circuit isolates the operation of the Rx from Tx, thereby offering the capability of sharing antenna between them. The Rx employs a high-efficiency radio frequency (RF)-dc converter, which is facilitated with threshold voltage cancellation technique for enhancing the efficiency, and adjustable internal impedance matching network to compensate the nonlinear behavior of the input impedance with respect to input power level. In addition, it includes a boost dc-dc converter to charge the storage element with a fixed voltage and current. The Tx utilizes a low-power phase-locked loop (PLL) and a class-D power amplifier (PA). Several techniques are adopted to achieve low power consumption. The chip is implemented in a 180 nm CMOS process with a die size of $2.3\,\,\mathrm {mm} \times 5\,\,\mathrm {mm}$. The Rx shows the measured RF to dc maximum power conversion efficiency (PCE) of 53.8% at the input power level of 0 dBm. The Tx achieves a variable output power range of −10 to 10 dBm, while consumes 4 and 23 mA at 0 and 10 dBm output power, respectively. [ABSTRACT FROM AUTHOR]

This article presents the analysis and design of a Class- $\text{E}_{\mathrm {M}}/\text{F}_{\mathrm {n}}$ power amplifier (PA). The high peak switch voltage factor of the classical Class- $\text{E}_{\mathrm {M}}$ PA is reduced by 27.3% through the adoption of the Class- $\text{F}^{-1}$ third-harmonic termination on the main circuit, resulting in a novel topology called the Class- $\text{E}_{\mathrm {M}}/\text{F}_{\mathrm {n}}$. The adoption of a finite dc-feed inductance enables the introduction of the design parameter $k$ , which can be exploited to extend the maximum operating frequency of the PA. The idealized voltage and current waveforms of the PA show that the main circuit fulfills not only zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) conditions as in the Class-E but also zero-current switching (ZCS) and zero-current derivative switching (ZCDS) conditions as in the Class- $\text{E}^{-1}$ , thus minimizing power dissipation during OFF-to-ON and ON-to-OFF transitions. The load-network parameters of the main and auxiliary circuits are derived, and harmonic-balance simulations are performed to confirm the analytical results. A Class- $\text{E}_{\mathrm {M}}/\text{F}_{3,5}$ PA employing a transmission-line load network was designed and implemented using GaN HEMTs. The constructed Class- $\text{E}_{\mathrm {M}}/\text{F}_{3,5}$ PA delivered a drain efficiency of 83%, a power-added efficiency of 76%, and an output power of 42.3 dBm at 1.8 GHz. [ABSTRACT FROM AUTHOR]

In this article, a parallel-circuit class-EF power amplifier with a shunt quarter-wave transmission-line for driving signals with arbitrary duty cycles is proposed and investigated. At the particular condition of duty cycle = 1/3, the values of the elements in the output network, as well as, some critical design parameters are analyzed and optimized. This leads to a series of significant improvements in the peak drain voltage (Vmax), the maximum operating frequency (fmax), and the power output capability (cp). Furthermore, in order to verify the advantage of the proposed new amplifier and its feasibility in realistic situations, a proof-of-concept circuit is designed and fabricated. Finally, at the operating frequency of 3.59 GHz, excellent performance has been achieved with the power-added efficiency of 79.9% and output power of 40.7 dBm. [ABSTRACT FROM AUTHOR]

This paper presents a fully integrated C-band Doherty power amplifier (DPA) based on a 0.25-μm GaN-HEMT process for the 5G massive MIMO application. The performance degradation caused by nonlinear output capacitance is analyzed, and a novel compensation technique is proposed. A low-Q output network is employed to broaden the bandwidth, and its insertion loss in the back-off region is demonstrated to be mainly decided by the Q-factor of the drain bias inductor of the main PA. Hence, by adopting on-chip transmission lines with high Q-factors for drain biasing, a full integration, and a low loss can be achieved simultaneously. Reversed uneven power splitting and back-off input matching are proposed for gain enhancement. The fabricated DPA demonstrates a small-signal gain of 8.6-11.6 dB, an output power of 40.4-41.2 dBm, a 6-dB back-off drain efficiency (DE) of 47% - 50%, and a saturation DE of 55%-63% across a wide bandwidth from 4.5 to 5.2 GHz, with an ultra-compact size of 2.2 mm × 2.1 mm. Using a 40-MHz LTE signal with a 7.7-dB peak-to-average power ratio at the carrier frequency of 4.9 GHz, the measured average output power and efficiency are 33 dBm and 43%, respectively. The raw adjacent channel power ratio is -29 dBc and is improved to -46 dBc by applying digital predistortion.

Single-phase matrix converters (MCs) are undergoing rapid developments due to their bipolar voltage gain (as required in dynamic voltage restorers) and step-changed frequency operation (used in high step-up ac–dc rectifiers, and to provide medium frequency isolation in traction and wind turbine converters, etc.). However, existing buck–boost MCs require high-voltage/current rating devices, and suffer from large component voltage/current stresses and ripples, significantly degrading their efficiency. This article proposes a highly efficient single-phase buck–boost MC; consisting of eight IGBTs (implemented using two full-bridge IGBT modules), second-order input and output filters, and a small value film capacitor. Efficient discrete inverting and noninverting buck and boost operations are proposed (same as that of sixteen-switch cascaded buck–boost MC) with significantly lower component voltage/current stresses and ripples. In addition, flexible inverting and noninverting buck–boost operations are proposed with independent control of buck and boost duty ratios. All of the proposed operations are free of commutation issues, compatible with reactive loads, and provide smooth input and output currents. Furthermore, all the switches have same voltage stresses, and all four switches in a full-bridge module experience the same current stresses. A comprehensive description of circuit operation is presented based on a number of proposed switch modulation strategies with a nonunity power factor load, followed by design guidelines, and comparative evaluations with existing topologies. Finally, experimental verification results are presented, using a 400-VA laboratory prototype converter. [ABSTRACT FROM AUTHOR]

This letter presents a broadband self-driving radio frequency-to-direct current (RF-dc) rectifier design realized on the CG2H40010F Cree’s GaN device. First, the transistor modeling parameters for the reverse-biased I – V characteristics have been obtained to achieve the high-frequency rectification at negative drain biasing. Besides, an enhanced self-synchronization is achieved across the operating bandwidth through an additional microstrip open-stub line at the gate input matching network. Thus, an additional line maintains a fixed 180° phase offset between drain and gate voltages. Finally, the rectifier efficiency of >60% has been measured from 2.65 to 2.95 GHz for 10-W RF input power. The designed rectifier has been outperformed the recent designs in terms of operational bandwidth (300 MHz) and rectification efficiency. [ABSTRACT FROM AUTHOR]

This letter presents a simple method to design dual-band high-efficiency power amplifiers (PAs). The dual-band coupler is exploited to design the output circuits of the PA. By proper selection of impedance conditions of terminal ports, the dual-band coupler can convert the fundamental impedance of transistor to the standard 50- $\Omega $ load at two frequencies. At the same time, the second harmonic impedance is also controlled without the need for additional tuning. For validation, a dual-band high-efficiency PA is designed and fabricated by using CGH40010F GaN HEMT. Measurements indicate that the designed PA can deliver saturated output power of 41.6 and 42.1 dBm at 1 and 2.3 GHz, respectively. Also, the obtained drain efficiency exceeds 72% at both frequencies. [ABSTRACT FROM AUTHOR]

The LLC resonant converter is one of the most attractive topologies in many applications, due to its simple structure and zero-voltage-switching capability. However, under wide-input-voltage condition, it has large primary conduction and turn-off switching losses because of small magnetizing inductance. Thus, in this article, the LLC resonant converter using three switches is proposed for high-efficiency under wide universal ac input voltage. These three switches can make two operating modes of LLC resonant converter according to low/high line input conditions. As a result, the proposed converter can be designed with larger magnetizing inductance, resulting in high efficiency. The validity of the proposed converter is verified with a 60-W prototype for high efficiency, almost maintaining the system size, compared with the conventional LLC converter. [ABSTRACT FROM AUTHOR]

A high-power, high-efficiency, and high-speed white light-emitting-diode (LED) wireless transmitter is presented in this paper. This transmitter system consists of a gallium nitride field effect transistor (GaN FET) driver with push-pull structure, freewheeling circuit, and remaining carriers sweep-out circuit based on a phosphorescent white LED. A novel push-pull circuit structure with intensity modulation is used to increase the efficiency of the proposed transmitter to 94.2% at 12 Mb/s theoretical baud rate. Generally speaking, LED transmission speed is restricted by the remaining carriers in the junction capacitance. In this paper, we introduce an improved adjustable carrier sweep-out circuit to resolve this problem. High-frequency components in the signal are preemphasized by adding parallel freewheeling diodes between the drain and source of the GaN drivers. Test results show that the power efficiency is 93.17% with -3 dB bandwidth at 8.3 MHz. The results also show that the architecture proposed in this paper allows the baud rate of the transmitter to reach 10 Mb/s with bit error rate below 10-5, which meets the IEEE 802.11 b requirements at distances farther than 1 m.

In this paper, a design approach for a high-efficiency concurrent dual-band power amplifier (PA) with precise harmonic control up to third order is proposed. With the precise harmonic control approach, the high-efficiency performance of the PA can be improved at two arbitrary wide interval frequencies. Based on the inherent impedance matching flexibility of the continuous Class-F (CCF) operating mode, the design spaces of fundamental and harmonic impedances of the PA are largely expanded. The optimal impedances of a CCF PA mode at the internal current-generator (I-gen) plane and package plane are investigated, respectively, and a novel dual-band matching network topology is designed to simultaneously present required load impedances at the fundamental and harmonic impedances of both operation frequencies. First, a harmonic control network is designed to control the harmonic impedances precisely for CCF operation. Then, the fundamental impedances are synthesized using the real frequency technique. To verify the validity of proposed methodology, a dual-band CCF PA operating at 2.6 and 3.5 GHz is designed, fabricated, and measured. The measurement results show that the peak drain efficiency is 76.7% with an output power 42.4 dBm at the lower band and 72.8% with an output power 41.1 dBm at the upper band.

In this paper, a new methodology using a distributed ladder structure with finite transmission zero at finite frequencies is proposed for designing a broadband high-efficiency continuous Class-F (CCF) power amplifier (PA). The approach of realizing finite transmission zeros in Richard domain using Real Frequency Technique is first presented. By applying the proposed approach, the characteristics of the driving point impedance (DPI) of the proposed structure can be deduced and obtained in theory. Furthermore, the synthesis methods in Richard domain are extended to synthesize the DPI of the proposed structure. Four types of distributed elements are investigated to synthesize the DPI of the proposed structure. This proposed structure can improve the performance of the CCF PA when the bandwidth approaches an octave as the finite transmission zero can be used to control the second harmonic impedance of the lower frequency which is near the upper frequency of the operation band. To verify the validity of the proposed method, a broadband high-efficiency CCF PA working from 1.15 to 2.2 GHz is designed. Experimental results show that the fabricated PA achieves 11.3-13.7 dB power gain and 40.5-43.2 dBm output power in the operation band. And the PA has also achieved a high-efficiency characteristic of 70%-83% drain efficiency (DE) over the whole operation bandwidth.

In this article, we discuss the use of a third harmonic component to the drive voltage on the grid of an inductive output tube (IOT). High-efficiency IOTs are typically characterized by efficiencies up to 70%–75%. However, the achievement of efficiencies greater than 80% would substantially reduce the operating costs of next-generation accelerators. In order to achieve this goal, we consider the addition of a third harmonic component to the drive signal on the grid of an IOT. The use of a third harmonic drive component in IOT guns has been considered in order to apply such a gun as the injector of radio frequency linear accelerators (RF linacs). Here, we consider that the IOT will be used to provide the rf power to drive RF linacs and apply the third harmonic with the intention of increasing the efficiency of the RF output of the IOT. We consider a model IOT with a 700-MHz resonant cavity and using an annular beam with a voltage of 30 kV, an average current of 6.67 A yielding a perveance of about $1.3~\mu \text{P}$. We simulate this IOT using the NEMESIS simulation code which has been successfully validated by comparison with the K5H90W-2 IOT developed by Communications and Power Industries. It is found that the effect of the third harmonic on the efficiency is greatest when the phase of the third harmonic is shifted by $\pi $ radians with respect to the fundamental drive signal and with third harmonic powers greater than about 50% that of the fundamental drive power. For the present example, we show that efficiencies approaching 86% are possible by this means. [ABSTRACT FROM AUTHOR]

This article presents a low-cost, high-efficiency, and full-metal reflectarray (RA) antenna with mechanical beam-steerable capabilities. A unit cell (UC) implemented by a metal cylinder with a cuboid-shaped notch is proposed to achieve a 1 bit reflection phase (0 and $\pi $) for the transverse electric (TE) and transverse magnetic (TM) normal incidence waves. The proposed UCs can be employed to construct an RA antenna with 2-D beam-steerable abilities. For demonstration, the RA antennas with six different beam directions are presented as examples, by simply adjusting the rotations of the UCs. The impedance matches of the RA antenna are all below −10 dB from 22 to 33 GHz, and the measured radiation patterns of the RA antenna are all highly consistent with the simulated counterparts for the six different beam direction scenarios. A 1.5 dB gain drop bandwidth of approximately 20% from 24.7 to 30 GHz and a peak realized gain of 18.9 dBi at 26 GHz are experimentally obtained for the RA antenna with radiation patterns at broadside. Compared to the substrate-based UCs loaded with p-i-n diodes, the proposed UCs have full-metal structures without using any active RF components and dielectric substrates, leading to the high total efficiency of the proposed RA antenna. Due to the low-cost, high-efficiency, and high-power handling properties, the proposed RA antenna can provide a fixed or scanning beam and is a good candidate for 5G millimeter-wave communication applications. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of Nd3+-doped phosphate glass for three-level laser were investigated for the first time. A 60 nm blue-shift of the three-level transition fluorescence spectrum was achieved by changing the host material from traditional silica glass to phosphate glass. An 880-nm all-fiber laser with a world-record slope efficiency of 42.8% was demonstrated with 25-cm-long 0.25-wt.% Nd3+-doped phosphate fiber. Our research shows that Nd3+-doped phosphate glass is a high-efficiency material for laser operation below 900 nm. [ABSTRACT FROM AUTHOR]

In contrast to traditional multilayer transmitarray designs, a novel dual-layer transmitarray antenna, consisting of two metallic layers printed on opposite sides of a single dielectric substrate, is proposed to achieve high transmission efficiency. First, it is theoretically derived that a dual-layer element, using the circular polarization conversion approach, can achieve a high transmission magnitude and a full transmission phase coverage. Next, a split-ring element has been designed as an example to demonstrate the theoretical analysis, where a full 360° transmission phase range with better than −1.0 dB transmission magnitude has been obtained. To experimentally validate the proposed concept and design, a circular transmitarray prototype is designed, simulated, fabricated, and tested at Ka-band. The diameter of the circular aperture is 405 mm ($27\lambda$), and the thickness of the transmission surface is 3.18 mm ($0.2\lambda$). The measured peak gain of the designed transmitarray is 36.1 dBic at 19.4 GHz with the aperture efficiency of 60.2%, while the measured 1 dB gain bandwidth is 9.5% (19.0–20.9 GHz). [ABSTRACT FROM AUTHOR]

This article presents a high data rate, high-efficiency 60-GHz on–off keying (OOK) CMOS transmitter and receiver. The transmitter consists of a voltage-controlled oscillator (VCO) and a modulator. The receiver consists of a low-noise amplifier, detector, and limiting amplifier (LA) and has a compact design. An analysis of the on–off isolation of the modulator and bandwidth of the LA reveals that the proposed transformer (TF) between the modulator and the VCO can improve the on–off isolation, and the feedforward capacitor can enhance the bandwidth. Implemented in the 65-nm CMOS technology, the transmitter and the receiver consume dc powers of 12.1 and 21 mW, respectively, at 12.5 Gb/s. Moreover, they occupy core chip areas of 0.09 and 0.06 mm2, respectively. The transceiver system is constructed with on-board Yagi–Uda antennas, and it achieves 12.5 Gb/s wireless OOK data transmission for a pseudorandom binary sequence of length 27 −1 with a bit error rate of less than 10−12. The proposed transceiver system achieves an energy efficiency of 2.65 pJ/bit. [ABSTRACT FROM AUTHOR]

In this brief, analysis of class-F high-efficiency power amplifiers (PAs) when adding a second-harmonic input voltage to the gate node of the transistor is derived. The theoretical formulations of the drain current, output power, and drain efficiency are elaborated for this case. Based on them, the maximum output power and drain efficiency can be obtained from the closed-form solution set of the initial amplitude and phase of second-harmonic input voltage component. Calculations show that, with a proper second harmonic voltage adding to the input of the transistor, the performance of class-F PAs can be improved evidently. Besides, to validate the theoretical analysis, a simulation using a real GaN transistor has been presented. The relative errors of drain efficiency and output power between the results of theory and simulation are only 1.3% and 2.4%, respectively. To the best knowledge of the author, this is the first full theory to illustrate the performance enhancement of class-F PAs with a second-harmonic input voltage manipulation. [ABSTRACT FROM AUTHOR]

A high-power, high-efficiency, and high-speed white light-emitting-diode (LED) wireless transmitter is presented in this paper. This transmitter system consists of a gallium nitride field effect transistor (GaN FET) driver with push–pull structure, freewheeling circuit, and remaining carriers sweep-out circuit based on a phosphorescent white LED. A novel push–pull circuit structure with intensity modulation is used to increase the efficiency of the proposed transmitter to 94.2% at 12 Mb/s theoretical baud rate. Generally speaking, LED transmission speed is restricted by the remaining carriers in the junction capacitance. In this paper, we introduce an improved adjustable carrier sweep-out circuit to resolve this problem. High-frequency components in the signal are preemphasized by adding parallel freewheeling diodes between the drain and source of the GaN drivers. Test results show that the power efficiency is 93.17% with −3 dB bandwidth at 8.3 MHz. The results also show that the architecture proposed in this paper allows the baud rate of the transmitter to reach 10 Mb/s with bit error rate below 10 $^{-5}$ , which meets the IEEE 802.11 b requirements at distances farther than 1 m. [ABSTRACT FROM AUTHOR]

This paper introduces a non-isolated high step-up dc–dc converter with dual coupled inductors suitable for distributed generation applications. By implementing an input parallel connection, the proposed dc–dc structure inherits shared input current with low ripple, which also requires small capacitive filter at its input. Moreover, this topology can reach high voltage gain by using dual coupled inductors in series connection at the output stage. The proposed converter uses active clamp circuits with a shared clamp capacitor for the main switches. In addition to the active clamp circuit, the leakage energy is recycled to the output by using an integrated regenerative snubber. Indeed, these circuits allow soft-switching conditions, i.e., zero voltage switching and zero current switching for active and passive switching devices, respectively. The mentioned features along with a common ground connection of the input and output make the proposed topology a proper candidate for transformer-less grid-connected photovoltaic systems. The operating performance, analysis and mathematical derivations of the proposed dc–dc converter have been demonstrated in the paper. Moreover, the main features of the proposed converter have been verified through experimental results of a 1-kW laboratory prototype. [ABSTRACT FROM PUBLISHER]

A method enabling the codesign of a high-efficiency power amplifier (PA) and a ring-resonator microstrip bandpass filter is proposed in this paper. Even–odd-mode analysis and a series of continuous modes (SCMs) are combined to realize broadband or multiband impedance matching as well as the suppression of undesired signals. The proposed codesign method can achieve both broadband and multiband frequency responses, and the designed component is relatively easy to analyze and fabricate due to its microstrip structure. For verification, a broadband and triband PA-filter components are designed and fabricated separately. The first component operates across 0.8–3.2 GHz (120%) with 39.7–42.9-dBm maximum output power and 57%–74% drain efficiency (DE). The second component, which has three passbands, covers several commercial frequencies with a measured output power of 39.6–41.3 dBm and DE from 62% to 68%. When these two components are driven by a 20-MHz long-term evolution signal with a peak-to-average power ratio of 6.2 dB, adjacent channel leakage ratios from −26.4 to −33.8 dBc and from −29.4 to −33.1 dBc are measured, respectively. [ABSTRACT FROM AUTHOR]

The high-efficiency current-mode (CM) and voltage-mode (VM) Class-E power amplifiers (PAs) for MHz wireless power transfer (WPT) systems are first proposed in this paper and the design methodology for them is presented. The CM/VM Class-E PA is able to deliver the increasing/decreasing power with the increasing load and the efficiency maintains high even when the load varies in a wide range. The high efficiency and certain operation mode are realized by introducing an impedance transformation network with fixed components. The efficiency, output power, circuit tolerance, and robustness are all taken into consideration in the design procedure, which makes the CM and the VM Class-E PAs especially practical and efficient to real WPT systems. 6.78-MHz WPT systems with the CM and the VM Class-E PAs are fabricated and compared to that with the classical Class-E PA. The measurement results show that the output power is proportional to the load for the CM Class-E PA and is inversely proportional to the load for the VM Class-E PA. The efficiency for them maintains high, over 83%, when the load of PA varies from 10 to 100  $\Omega$, while the efficiency of the classical Class-E is about 60% in the worst case. The experiment results validate the feasibility of the proposed design methodology and show that the CM and the VM Class-E PAs present superior performance in WPT systems compared to the traditional Class-E PA. [ABSTRACT FROM AUTHOR]