Search

Ultra‐wideband (UWB) systems utilise a broad frequency spectrum to achieve high data transmission rates and enhanced precision, creating a demand for specialised UWB antennas. Circularly Polarised (CP) antennas are considered essential for maintaining robust performance under varied environmental conditions. Among them, the crossed dipole is effective for UWB CP applications, but its relatively large size could limit its use in various systems. A miniaturised crossed dipole design employing the Koch fractal structure is proposed and the measurement results are presented. The prototype antenna achieved an effective bandwidth covering 88% of the frequency range from 1.4 to 3.6 GHz. Additionally, a 4 × 4 array using this design was tested in the same frequency band, demonstrating beam‐steering capabilities up to 30°. The proposed antenna has demonstrated effective deployment in diverse communication systems and phased array applications within ultra‐wideband (UWB) CP environments. [ABSTRACT FROM AUTHOR]

This study investigated a frequency-selective surface (FSS) that is used to suppress harmonics affecting the performance and accuracy of radar systems. One side of the FSS features a metal grid structure, and when converted into an equivalent circuit model, it exhibits the characteristics of a band-pass filter with an L and C parallel structure. The other side of the FSS features a metallic loop structure and when represented as an equivalent circuit model, it exhibits the characteristics of a band-stop filter with an L and C series structure. The reflection coefficient ( S 11 ) and transmission coefficient ( S 21 ) of the FSS designed based on theory are compared using a CST studio suite and Keysight's Advanced Design System. In addition, the transmission coefficients are verified through actual measurements, wherein the measured transmission coefficient is −0.1 dB at 3.0 GHz and approximately −50 dB at the harmonic frequency of 6.0 GHz. The designed FSS is attached to an actual radar system, and the 2D radiation pattern and maximum gain are measured during steering in boresight, azimuth ( 30 ∘ ) and elevation ( 30 ∘ ) directions. At 3.0 GHz, the maximum gain in boresight is 17.25 dB without the FSS and 17.12 dB with the FSS. At 6.0 GHz, the maximum gain is 12.79 dB without the FSS and 2.69 dB with the FSS. At 3.0 GHz, the maximum gain during azimuth steering is 16.13 dB without the FSS and 16.68 dB with the FSS, and the maximum gain during elevation steering is 15.74 dB without the FSS and 15.90 dB with the FSS. [ABSTRACT FROM AUTHOR]

This paper presents the design of a two-port dual-band dual-circularly-polarized dielectric resonator antenna (DRA). The proposed DRA is formed by stacking two dielectric resonators (DRs) of different shapes, including a hexagonal DR on top and a cross-shaped DR on the bottom. It is designed to resonate at two near-degenerate orthogonal modes of TE111 and TE113, and an aperture-coupled feeding through a cross-like slot is used to achieve dual-band impedance matching simultaneously for right- and left-handed circular polarizations. Tests were conducted on a prototype working in C-band to verify the design concept. The experiment results demonstrate that the proposed DRA has exceptional performance with measured −10 dB reflection bandwidths of 24.4% and 17.4%, 3 dB axial ratio bandwidths of 21.2% and 16.3%, and maximum gains of 5.64 and 8.13 dBic for the lower and upper bands, respectively. Moreover, the measured channel isolation is more than 15.8 dB. The results obtained from the experiments show good agreement with the simulation, and hence, it can be concluded that the proposed DRA is a promising solution that can be used for various wireless communication applications. [ABSTRACT FROM AUTHOR]

In response to the increasing deployment of unmanned aerial vehicles (UAVs) across various sectors, the demand for efficient microwave power transmission (MPT) systems for UAVs has become paramount. This study introduces series-fed circularly polarized (CP) and passively beam-tilted patch array antennas designed to enhance MPT in UAV applications, with the intention of addressing the needs related to extending flight times and improving operational efficiency. The radiating element of the proposed antennas employs the conventional model of the patch with truncated corners for CP operation, with transmission line lengths optimized for beam tilt to ensure precise energy transfer. Additionally, an open stub is integrated into the broadside series-fed antenna to improve impedance matching, which is crucial for maintaining signal integrity. The proposed design achieves right-hand circular polarization (RHCP) with an axial ratio (AR) below 3 dB across the operating band, indicative of its effectiveness in diverse UAV operational contexts. Prototypes of each proposed antenna were fabricated and measured according to the beam tilting angle. The measured RHCP realized gains of the proposed antennas are 14.59, 13.09, 13.07, and 10.71 dBic at the tilted angles of 0°, 15°, 30°, and 45°, respectively, at 5.84 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the development of a four-port dual-band dual-polarized antenna for transmitting/receiving (Tx/Rx) applications in Ku-band satellite communications. The antenna consists of two antenna elements sharing a common radiating aperture, a low-band element formed by an L-probe proximity-fed square-ring radiator for operation at the Rx band of 10.7–12.75 GHz, and a high-band element realized by a stacked-patch radiator for operation at the Tx band of 13.75–14.5 GHz. Within a compact multilayer structure, the antenna achieves wide dual-band operation, with each band having the ability to simultaneously operate with dual polarization. An antenna prototype is fabricated and tested to verify its performance. The experimental results show that the proposed antenna achieves an impedance bandwidth of 9.28–12.96 GHz (13.21–15.32 GHz), an isolation value between two orthogonal polarizations of 12 dB (12.4 dB), and a peak gain of 6.63 dBi (5.42 diBi) at the low band (high band). Tx/Rx isolation of more than 14 dB is achieved in both the Rx band and Tx band. [ABSTRACT FROM AUTHOR]

Polymers for implantable devices are desirable for biomedical engineering applications. This study introduces a water-resistant, self-healing fluoroelastomer (SHFE) as an encapsulation material for antennas. The SHFE exhibits a tissue-like modulus (approximately 0.4 MPa), stretchability (at least 450%, even after self-healing in an underwater environment), self-healability, and water resistance (WVTR result: 17.8610 g m−2 day−1). Further, the SHFE is self-healing in underwater environments via dipole–dipole interactions, such that devices can be protected from the penetration of biofluids and withstand external damage. With the combination of the SHFE and antennas designed to operate inside the body, we fabricated implantable, wireless antennas that can transmit information from inside the body to a reader coil that is outside. For antennas designed considering the dielectric constant, the uniformity of the encapsulation layer is crucial. A uniform and homogeneous interface is formed by simply overlapping two films. This study demonstrated the possibility of wireless communication in vivo through experiments on rodents for 4 weeks, maintaining the maximum communication distance (15 mm) without chemical or physical deformation in the SHFE layer. This study illustrates the applicability of fluoroelastomers in vivo and is expected to contribute to realizing the stable operation of high-performance implantable devices. [ABSTRACT FROM AUTHOR]

A compact three-dimensional (3-D) metal-printed ridged waveguide slot array antenna with wideband, dual linear polarization and low cross-polarization is presented for X-band applications. The proposed design achieves a compact structure due to the method of using a ridged waveguide (RWG). A vertically linear polarized (VP) array is realized through eight longitudinal shunt slots etched on the non-ridged broad wall of the RWG, while a horizontally linear polarized (HP) array is realized through eight V-shaped slots cut on the ridged broad wall of the RWG. To extend the operating bandwidth, each 1 × 8-element linear array is separated into two 1 × 4-element sub-arrays through a central feeding technique. The two sub-arrays of the VP array are excited with equal amplitude and are 180° out-of-phase through a T-junction power divider, which connects the coaxial feed and the radiated waveguide, while the two HP subarrays are directly excited by a coaxial feed with equal amplitude and remain in phase. The feed structure uses coaxial probes directly attached to the RWG to provide good mechanical stability and low voltage around the feed. An optimized 2 × 8-element dual-polarized array is fabricated using 3-D metal-printing technology for experimental verification. The measured −10 dB impedance bandwidth of the VP array is 1.2 GHz (12.2%) and, of the HP array, is 1.1 GHz (11.2%) with maximum gains of 14.6 and 15.5 dBi, respectively. There is good polarization purity over the entire operating bandwidth with a cross-polarization level better than −40 dB in the main beam direction. The isolation between two orthogonal polarized arrays is greater than 40 dB over the whole band. [ABSTRACT FROM AUTHOR]

A double-layer element consisting of a spider-shaped structure on the top layer and a pair of concave arms with a circular ring on the middle layer is proposed for the wideband reflectarray with low cross-polarization characteristics. The unit cell offers a linear and wider phase range of 800 ∘ . Based on the proposed unit cell, an offset-fed reflectarray with an octagonal aperture comprising 6769 unit cells is constructed at 11.725 GHz. The reflectarray offers 1 dB and 3 dB gain bandwidths of 25.2% and 32.3%, respectively, with an operating frequency range of 10–13.85 GHz. A peak gain of 31.2 dBi with an aperture efficiency of 42% is achieved. The cross-polarization levels are less than the co-polarization by 40 dB over the entire operating band. [ABSTRACT FROM AUTHOR]

This article presents a power management integrated circuit for a wireless power receiver unit. A dual-mode high-efficiency active rectifier design is based on alliance for wireless power (A4WP) and wireless power consortium (WPC) standards. A gate charge recycling technique is proposed in the dual-mode active rectifier so that the current generated by the switching of the high side gate driver can be recycled to the rectifier output voltage in order to enhance efficiency. A step-down dc–dc converter with a proposed bootstrap circuit and dynamic pull-up resistor gate driver circuit is designed. The chip is implemented in a 0.18-μm bipolar-CMOS double-diffused metal-oxide-semiconductor process. The total die area, including the pad, is 2.64 mm × 2.6 mm. The measurement results show that the active rectifier achieves peak power conversion efficiency (PCE) of 94.7% and generates an output voltage of 7.68 V in WPC mode and 9.1 V with 93.4% efficiency in A4WPC mode. The input voltage varies from 10 VP-P–12 VP-P. Similarly, the step-down dc–dc converter obtains a peak PCE of 93.2% at a load current of 500 mA while producing an output voltage of 5 V. The overall system efficiency at A4WP and WPC mode are 86.7% and 88.2%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost, low-sidelobe-level, differential-fed, substrate-integrated waveguide (SIW)-based slot array antenna with zero beam squint. The antenna consists of two identical six-way unequal power dividers (PDs) and a 6 × 16 slot array and is realized on a single-layer substrate. The six-way unequal PD provides tapered amplitude and in-phase excitation for six SIWs, and each of them has 16 radiating slots. The 1 × 16 linear slot array on each SIW is excited using a differential feed to avoid undesired beam squinting across its operating band. A two-way hybrid waveguide (WG)-to-SIW E-plane PD is developed to provide equal amplitude and out-of-phase excitation for two six-way unequal power dividers. Moreover, metallic decoupling walls are implemented between two adjacent linear slot arrays to reduce E-plane external mutual coupling. An antenna prototype is fabricated and experimentally verified. The fabricated antenna shows that the measured −10 dB reflection bandwidth is 7.15% (9.57–10.28 GHz), with the achieved gain ranging from 20.30 to 21.92 dBi. A stable boresight beam is observed over the entire operating band. Furthermore, at the designed frequency of 10 GHz, peak SLLs of −29.1 dB and −29.4 dB are achieved in the E- and H-plane, respectively. [ABSTRACT FROM AUTHOR]

This paper presents an on-chip fully integrated analog front-end (AFE) with a non-coherent digital binary phase-shift keying (DBPSK) demodulator suitable for short-range magnetic field wireless communication applications. The proposed non-coherent DBPSK demodulator is designed based on using comparators to digitize the received differential analog BPSK signal. The DBPSK demodulator does not need any phase-lock loop (PLL) to detect the data and recover the clock. Moreover, the proposed demodulator provides the detected data and the recovered clock simultaneously. Even though previous studies have offered the basic structure of the AFEs, this work tries to amplify and generate the required differential BPSK signal without missing data and clock throughout the AFE, while a low voltage level signal is received at the input of the AFE. A DC-offset cancellation (DCOC), a cascaded variable gain amplifier (VGA), and a single-to-differential (STOD) converter are employed to construct the implemented AFE. The simulation results indicate that the AFE provides a dynamic range of 0 dB to 40 dB power gain with 2 dB resolution. Measurement results show the minimum detectable voltage at the input of AFE is obtained at 20 mV peak-to-peak. The AFE and the proposed DBSPK demodulator are analyzed and fabricated in a 130 nm Bipolar-CMOS-DMOS (BCD) technology to recover the maximum data rate of 32 kbps where the carrier frequency is 128 kHz. The implemented DCOC, cascaded VGA, STOD, and the demodulator occupy 0.15 mm 2 , 0.063 mm 2 , 0.045 mm 2 , and 0.03 mm 2 of area, respectively. The AFE and the demodulator consume 2.9 mA and 0.15 mA of current from an external 5 V power supply, respectively. [ABSTRACT FROM AUTHOR]

A circular sector-shaped dipole antenna with meandered arms based on an artificial magnetic conductor (AMC) is proposed in this study. A compact unit cell of the AMC operating within 19–485 MHz is designed using a ferrite material, which exhibits high-permeability characteristics in the high-frequency (HF), very-high-frequency (VHF), and ultra-high-frequency (UHF) bands. The configuration of the meandered arms is optimally designed using a binary genetic algorithm, so that the antenna combined with the AMC meets the voltage standing wave ratio (VSWR) specification of 3.5:1 or less within the HF, VHF, and UHF bands. The proposed antenna with the AMC is fabricated and measured. The measured VSWR frequency bandwidth (3.5:1 or less) is 25.8:1 (14–361 MHz), and the measured result matches with the simulated result well. Furthermore, to verify the performance of the proposed antenna with the AMC, the measured received power results are compared with a commercial reference antenna operating in HF, VHF, and UHF bands. [ABSTRACT FROM AUTHOR]

This study designed a wide-beamwidth pixelated dielectric resonator antenna (DRA) combined with a low-pass filter (LPF) to suppress harmonics. The DRA was designed to create a wide-beam pattern with a pixelated structure. The pixelated DRA was optimized by a genetic-learning particle swarm optimization algorithm. To prevent significant higher-mode radiation and harmonics from occurring in the DRA, an LPF was included in its feeding line. The filter had a seventh-order Chebyshev design, and a hybrid step-impedance filter was proposed by modifying the step-impedance filter for use in narrow spaces behind the ground. [ABSTRACT FROM AUTHOR]

A proposed prototype of a 10-bit 1 MS/s single-ended asynchronous Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC) with an on-chip bandgap reference voltage generator is fabricated with 130 nm technology. To optimize the power consumption, static, and dynamic performance, several techniques have been proposed. A dual-path bootstrap switch was proposed to increase the linearity sampling. The Voltage Common Mode (VCM)-based Capacitive Digital-to-Analog Converter (CDAC) switching technique was implemented for the CDAC part to alleviate the switching energy problem of the capacitive DAC. The proposed architecture of the two-stage dynamic latch comparator provides high speed and low power consumption. Moreover, to achieve faster bit conversion with an efficient time sequence, asynchronous SAR logic with an internally generated clock is implemented, which avoids the requirement of a high-frequency external clock, as all conversions are carried out in a single clock cycle. The proposed error amplifier-based bandgap reference voltage generator provides a stable reference voltage to the ADC for practical implementation. The measurement results of the proposed SAR ADC, including an on-chip bandgap reference voltage generator, show an Effective Number of Bits (ENOB) of 9.49 bits and Signal-to-Noise and Distortion Ratio (SNDR) of 58.88 dB with 1.2 V of power supply while operating with a sampling rate of 1 MS/s. [ABSTRACT FROM AUTHOR]

In this study, we investigated the recent deterioration of the radiation pattern performance of conformal arrays, which are applied to fields such as aircraft and vehicles. We analyzed the radiation pattern of conformal arrays in the array factor stage by combining previous studies on various beam-forming techniques for conformal arrays. To efficiently calculate and utilize the radiation pattern of conformal arrays, we derived an array factor based on phase composition for nonplanar arrays of three-dimensional (3D) coordinate systems. As an amplitude tapering method for controlling the sidelobe level of the derived 3D array factor, we propose a Bernstein polynomial generalization method based on Genetic Learning Particle Swarm Optimization. The proposed 3D array factor was verified using a cavity-backed patch antenna operating at the X-band through EM simulation of conformal arrays as a single element. [ABSTRACT FROM AUTHOR]

This paper presents a multi-gain radio frequency (RF) front-end low noise amplifier (LNA) utilizing a multi-core based on the source degeneration topology. The LNA can cover a wide range of input and output frequency matching by using a receiver (RX) switch at the input and a capacitor bank at the output of the LNA. In the proposed architecture here, to avoid the saturation of RX chain, 12 gain steps including positive, 0 dB, and negative power gains are controlled by a mobile industry processor interface (MIPI). The multi-core architecture offers the ability to control the power consumption over different gain steps. In order to avoid the phase discontinuity, the negative gain steps are provided using an active amplification and T-type attenuation path that keeps the phase discontinuity below ±5 degrees between two adjacent power gain steps. Using the multi-core structure, the power consumption is optimized in different power gains. The structure is enhanced with the adaptive variable cores and reactance parameters to maintain different power consumption for different gain steps and remain the output matching in an acceptable operating range. Furthermore, auxiliary linearization circuitries are added to improve the input third intercept point (IIP3) performance of the LNA. The chip is fabricated in 65 nm complementary metal-oxide semiconductor (CMOS) silicon on insulator (SOI) process and the die area is 0.308 mm2. The proposed architecture achieves the IIP3 performance of −10.2 dBm and 8.6 dBm in the highest and lowest power gains, which are 20.5 dB and −11 dB, respectively. It offers the noise figure (NF) performance of 1.15 dB in the highest power gain while it reaches 14 dB when the power gain is −11 dB. The LNA consumes 16.8 mA and 1.33 mA current from a 1 V power supply that is provided by an on-chip low-dropout (LDO) when it operates at the highest and lowest gains, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a quasi-isotropic hybrid dielectric resonator antenna (DRA) and bow-tie patch with harmonics suppression. The suggested antenna consists of a DRA, a bow-tie patch, and a microstrip seventh-order Chebyshev low-pass filter. By loading a bow-tie patch on the designed DRA, a quasi-isotropic pattern is realized. The seventh-order Chebyshev low-pass filter was applied to the feed line, and harmonics were reduced in the section separate to the operating band to remove harmonics generated by the proposed antenna. The simulated S 11 that satisfies below −10 dB is 3.09–3.3 GHz (6.25%), and the measured S11 is 3.10–3.28 GHz (5.64%). The simulated gain difference considering all radiating regions ( 0 ∘ ≤ φ ≤ 360 ∘ and 0 ∘ ≤ θ ≤ 180 ∘ ) is 7.211 dB. Compared with the antenna without a filter, the harmonic gain was reduced by 10.847 and 15.774 dB. The measured gain isolation of the operating band and the second and third harmonics are 10.10 and 18.94 dB, respectively. The proposed antenna is considered to be applicable to applications that require radio wave reception in all directions such as wireless point access points, internet of things and radio frequency identification, and is expected to contribute to reducing the size of the RF system. [ABSTRACT FROM AUTHOR]

This article presents a novel method of extending the high-efficiency range of Doherty power amplifiers (DPAs) by utilizing multiple output power back-off (OBO) parameters. The OBO extension techniques of the DPAs, such as complex combining load (CCL), virtual stub (VS), and out-phased current combining (OCC) methods, were defined, and a general expression for these OBO extension techniques was derived. Using the general expression, three OBO extension methods were comparatively and comprehensively analyzed. Based on the analysis, the DPA with an extended OBO can be designed by simultaneously employing multiple back-off techniques with a high degree of freedom. To verify the general expression and its analysis, a DPA design for the frequency band of 3.45–3.75 GHz with GaN HEMTs was conducted using multiple OBO extension techniques of VS and OCC methods for a large OBO of 8.5 dB. Using a long-term evolution (LTE) signal with a signal bandwidth of 20 MHz and a peak-to-average power ratio (PAPR) of 8 dB, the drain efficiency (DE) of 38.9%–56.8% was achieved at the average output power levels of 34.4–36.8 dBm while satisfying ACLR of no larger than −45 dBc with digital predistortion (DPD) linearization. Under excitation of a 5G new radio (NR) signal with a signal bandwidth of 100 MHz and a PAPR of 8 dB, the DE of 38.5%–50.2% was achieved at the average output power levels of 34.6–36.8 dBm with an ACLR of under −24.6 dBc without DPD linearization. [ABSTRACT FROM AUTHOR]

This paper presents a register-transistor level (RTL) based convolutional neural network (CNN) for biosensor applications. Biosensor-based diseases detection by DNA identification using biosensors is currently needed. We proposed a synthesizable RTL-based CNN architecture for this purpose. The adopted technique of parallel computation of multiplication and accumulation (MAC) approach optimizes the hardware overhead by significantly reducing the arithmetic calculation and achieves instant results. While multiplier bank sharing throughout the convolutional operation with fully connected operation significantly reduces the implementation area. The CNN model is trained in MATLAB® on MNIST® handwritten dataset. For validation, the image pixel array from MNIST® handwritten dataset is applied on proposed RTL-based CNN architecture for biosensor applications in ModelSim®. The consistency is checked with multiple test samples and 92% accuracy is achieved. The proposed idea is implemented in 28 nm CMOS technology. It occupies 9.986 mm2 of the total area. The power requirement is 2.93 W from 1.8 V supply. The total time taken is 8.6538 ms. [ABSTRACT FROM AUTHOR]

A 3.4–3.7 GHz dielectric rod waveguide probe for near-field measurements is proposed for applications on the 5G sub-6 GHz band. By implementing a dielectric-filled waveguide, the probe achieved a higher resolution and low scattering characteristics through a miniaturized aperture compared to the open-ended waveguide (OEWG) used for conventional near-field probes. An $8\times 8$ pixelated grid structure in the dielectric launcher section of the probe is implemented to further reduce the scattering characteristics of the probe. The proposed probe is fabricated and experimentally verified. A coating of silver is applied to the dielectric during a production process. Measurement shows that the −10 dB reflection coefficient bandwidth meets 3.4–3.7 GHz requirement and that the radiation pattern shows a broadside gain of about 3.8 dBi with no null at the forward hemisphere. The results of a scattering characteristic experiment indicate decreased interferer level of 7.3 dB compared to an OEWG. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method for near-field-based 5G sub 6-GHz array antenna diagnosis using transfer learning. A classification network was implemented for normal/abnormal operation of the array antenna and the failure of a specific port. Furthermore, a regression network that could predict the amplitude and phase of the excitation signal of the array antenna was employed. Additionally, to accelerate the array antenna diagnosis, several near-field lines were sampled and reflected in the regression network. The proposed method was verified by measuring a fabricated 5G sub-6 GHz band 4 × 4 array antenna in various scenarios using a divider and coaxial cables. The tests showed that the trained network accurately diagnosed 29 of 30 measurement results. [ABSTRACT FROM AUTHOR]

This article presents a power-efficient hybrid energy-harvesting system that scavenges energy from solar, vibration, and radio frequency (RF) energy sources and converts into regulated output dc voltage courtesy buck–boost dc–dc converter. The proposed architecture incorporates tetra-paths for maintaining high power conversion efficiency (PCE) over extended input power range (−10 to 30 dBm). A time-domain maximum power point tracking technique is proposed for solar energy harvester. A high-efficiency full wave rectifier is designed for triboelectric rectifier. A 5.8-GHz RF-dc converter with adaptive matching is proposed to increase dynamic range of the input power. The chip is implemented in 0.18-µm bipolar-CMOS-DMOS process. The die area of the chip is 2.8 mm × 5.0 mm, including the pads. The solar and triboelectric energy harvesters achieve a measured peak efficiencies of 75.4% and 92.3%, respectively. The high-power 5.8-GHz RF-dc converter achieves measured PCE of 76% at 30 dBm input power. The low-power dual-band RF-dc converter operating at 900 MHz and 2.4 GHz obtains measured peak efficiencies of 73% and 71.9% at 0 dBm input, respectively. The buck–boost dc–dc converter employed in the proposed hybrid energy harvesting system achieves a measured peak PCE of 94.5%. [ABSTRACT FROM AUTHOR]

In this article, we present an integrated triple-mode wireless power transmitter unit (TWPTU) circuit supporting all three alliance for wireless power (A4WP), wireless power consortium (WPC), and power matters alliance (PMA) standards, simultaneously, for high-efficiency battery charging application. The triple-mode power amplifier (PA) utilizes the adaptive gate splitting technique and free-wheeling control to achieve high efficiency in triple modes. The programmable supply voltage from two high-efficiency dc–dc converters supplies the PA. The output power of the PA is measured by the proposed high accuracy current sensor and controlled through different communication protocols depending on their operating standards. The WPC/PMA modes are based on the amplitude-shifting-key and frequency-shifting-key modulations for the communication between the transmitter and the receiver, while in the A4WP mode, to control the output power of the PA, the bluetooth-low-energy (BLE) unit adjusts the supply voltage through the provided step-up dc–dc converter. A step-down dc–dc converter with pulse-skipping modulation reduces the power consumption of the TWPTU during charge waiting time. The demodulator for in-band communication of WPC/PMA and interintegrated circuit for BLE communication of A4WP is fully implemented. This chip is fabricated using a 180-nm bipolar-CMOS-DMOS (BCD) process with laterally diffused mosfet options and has a die size of 5 × 3.5 mm. The proposed architecture achieves the output power level of 25.8 W. The measurement results show the maximum system efficiencies of the TWPTU in WPC/PMA and A4WP modes are 88.5% and 84.3%, respectively. [ABSTRACT FROM AUTHOR]

In this article, a high gain and compact 4 × 4 circularly polarized microstrip patch antenna array is reported for the data transmission of the next-generation small satellite. The radiating element of the circularly polarized antenna array is realized by the conventional model of the patch with truncated corners. A compact two-stage sequential rotational phase feeding is adopted that broadens the operating bandwidth of the 4 × 4 array. A small stub is embedded in the sequential rotational feed, which results in better performance in terms of the S-parameters and sequential phases at the output ports than sequential rotational feed without open stub. A prototype of the array is fabricated and measured. Fulfilling the application requirements of the next-generation small satellites, the array has the left-handed circularly polarized gain of more than 12 dBic with the axial ratio level below 1.5 dB in the ±10 ∘ angular space with respect to the broadside direction for the whole bandwidth from 8.05 GHz to 8.25 GHz. Moreover, the left-handed circularly polarized gain varies from 15 to 15.5 dBic in the desired band. The radiation patterns are measured; both the co- and X-pol are validated. [ABSTRACT FROM AUTHOR]

In this communication, a tapered slot antenna array with a perforated wide-angle impedance matching (WAIM) layer is studied for active beam steering. To achieve the wide-angle beam scanning characteristic, a tapered slot antenna is used in the array antenna design. For active impedance matching in a wide beam-steering angle, a thin dielectric type of WAIM is introduced, and an optimal WAIM characteristic is realized by changing the effective dielectric constant by adding an air hole to the WAIM. To verify the characteristics of the designed antenna, a $16\times 16$ array is fabricated and measured. The fabricated array shows active $S$ -parameter characteristics of less than −9.13 dB during E-plane scanning and −9.31 dB during H-plane scanning when the beam is steered up to 70° on both planes. It was also confirmed that when the beam is steered to 70°, no scan blindness or grating lobes occur within the operating frequency. [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 a high-efficiency fast transient constant on-time (COT) control dc–dc buck converter for the Internet of Things applications. The current reused current sensor is proposed to enhance the loop stability and improve the power conversion efficiency at light load. Input current is sensed and added to the feedback voltage of the dc–dc converter to increase the sensed output ripple voltage. Fast transient dc-offset cancelation technique is introduced to achieve a fast transient recovery time and to cancel the output dc offset. This chip is fabricated with a 0.13-μm CMOS process. A standard supply voltage of 7–15 V is applied to produce the output voltage of 5–5.33 V. The total die area is 2 mm × 1.5 mm. The settling time is 17 μs. The transient recovery time from light to heavy load and from heavy load to light load are 3 μs and 2.7 μs, respectively, with a maximum dc offset of 3.5 mV. The overshoot voltage is 85 mV and the undershoot voltage is 72 mV. The peak efficiency of the proposed design is 95.56% at 0.5 A and efficiency at the light load of 10 mA is 84.60%. [ABSTRACT FROM AUTHOR]

This paper discusses how to optimize the weighting of individual subarrays to derive the low sidelobe level (SLL) based on quadratic programming (QP) and how to derive QP parameters to ensure that the objective function is composed of the quadratic function form, with the actual number identical to the standard objective function of QP. Next, in order to analyze the SLL, a 24 × 24 phased array antenna was compared with 96 transmit–receive modules (TRMs) attached only to the subarray stage and a phased array antenna with 576 TRMs attached to all radiating elements without a subarray. Optimized weighting was applied to the array antennas with a subarray, and Taylor weighting was applied to the array antennas without a subarray. The number of TRMs used in the phased array antenna with the optimized weighting was reduced by 83.3% compared to the phased array antenna in which TRMs were attached to all radiating elements. The SLL and the half-power beamwidths (HPBWs) of the two antennas were practically identical in a narrow beam-scanning environment. Finally, an array pattern (AP) in which mutual coupling between the radiating elements was considered was calculated to verify the optimized weighting. Moreover, the optimized weighting was applied to CST Microwave Studio (an EM full-wave simulation) to compare the results from the AP calculation and a simulation. It was confirmed that the two results above are largely indistinguishable. The analysis found that the HPBW is 3.6 ∘ × 3.6 ∘ and the SLL is −26.18 dB from AP calculations in the boresight direction. When each 5 ∘ beam was scanned at the azimuth and elevation, the corresponding HPBW values were 3.7 ∘ × 3.7 ∘ and 3.7 ∘ × 3.7 ∘ and the SLLs were −22.70 dB and −24.44 dB according to the AP calculations. [ABSTRACT FROM AUTHOR]

A millimeter-wave (mm-wave) broadband circularly polarized (CP) magneto-electric (ME) dipole array antenna is proposed. The antenna element consists of a ME dipole, a direct T-shaped probe, and a pair of shorted parasitic elements. The shorted parasitic elements are employed to ensure a considerable expansion of the 3 dB axial ratio (AR) bandwidth to lower frequencies. As a result, the ME dipole antenna element achieves a wide overlapped AR/impedance bandwidth of 56.89% (22.45–40.3 GHz). Based on the proposed CP antenna element, a 2 × 2 CP array antenna that incorporates an improved X-shaped power divider network is developed. A prototype of the 2 × 2 CP array antenna is fabricated and experimentally verified. The measured results indicate that a −10 dB impedance bandwidth of 50.39% (23.9–40 GHz) and a 3 dB AR bandwidth of 50% (24–40 GHz) are achieved, forming a broad overlapped AR/impedance bandwidth of 24–40 GHz, which covers most of the current mm-wave 5G bands. Moreover, a peak gain of 14.88 dBic is also observed. Thus, the demonstrated antenna with broadband CP operation and good radiation performance can be an excellent candidate for 5G mm-wave applications. [ABSTRACT FROM AUTHOR]

In this article, a 15-W quadruple-mode reconfigurable wireless power-receiving unit with high efficiency for Inductive coupling and magnetic resonance-based standards, such as wireless power consortium (WPC), power matters alliance (PMA), alliance for wireless power (A4WP), and magnetic secure transmission (MST) applications is proposed. Quadruple-mode gate controller(QMGC) is proposed in quadruple-mode synchronous rectifier to manage sizes of core and drivers which results in maximum power conversion efficiency (PCE) for each mode based on conduction and switching losses. In QMGC, switchable zero voltage and current sensing block is proposed for WPC/PMA to maximize PCE regardless of load current variations. For A4WP mode, a digitally controlled delay adjustment block is adapted to minimize power consumption while compensating for delay which results in reverse leakage current and power loss. Finally, for MST mode, low power TX (LPTX) block is implemented to minimize current consumption so that burden on battery can be minimized. A high-resolution current sensor is proposed in low-drop out regulator to sense current for overcurrent limit and overcurrent protection. The measured PCE of proposed system at 15 W are 95.3% and 92.3% for WPC/PMA and A4WP mode, respectively. For MST, power consumption is reduced to 35% courtesy LPTX block. [ABSTRACT FROM AUTHOR]

This article presents a Doherty power amplifier (DPA) based on asymmetric cells with a complex combining load (CCL). In this study, a new and intuitive design technique using the Smith chart is proposed for developing the load network of the CCL-DPA. The peaking amplifier consists of a larger cell size compared to that of the carrier amplifier in order to achieve higher power gain and peak output power in comparison with the conventional CCL-DPAs based on symmetric cells. For verification purposes, the proposed asymmetric CCL-DPA was designed and implemented using 6- and 10-W GaN-HEMTs for the carrier and peaking amplifiers, respectively. For the 1.68-GHz continuous-wave signal, the asymmetric CCL-DPA exhibited a power-added efficiency (PAE) of 68.0% and a drain efficiency (DE) of 73.9% at a peak output power of 43.5 dBm. When an output power back-off of 9.5 dB was used, a PAE of 52.0% and a DE of 54.7% were achieved. Using the long-term evolution signal with a peak-to-average power ratio of 9.6 dB and a signal bandwidth of 10 MHz, a PAE of 53.6%, a DE of 56.4%, and a power gain of 13.5 dB were obtained at a power level of 34.0 dBm. Using a digital predistortion technique, an adjacent channel leakage power ratio of −48 dBc was achieved at the same power level. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the radar cross section (RCS) of an integrated mast and present the optimized mast shape for RCS reduction. The RCS is simulated using commercial electromagnetic (EM) software based on the shooting and bouncing rays (SBR) method and the diffraction fields at the edges are also considered. Threat frequencies, threat regions and cardinal points are first defined considering the operational environments of a naval vessel. We calculate and analyze the RCS of the integrated mast in terms of the threat frequencies, the shapes of the integrated mast and the direction and polarization of the incident waves. The shape of the integrated mast is optimized based on the shaping technique. The optimized mast has low RCS properties in the primary threat sectors except for the exceptional angle regions. [ABSTRACT FROM AUTHOR]

In this paper, a low-profile HF (high-frequency) meandered dipole antenna with a ferrite-loaded artificial magnetic conductor (AMC) is proposed. To operate in the HF band while retaining a compact size, ferrite with high permeability is applied to the unit cell of the AMC. The operating frequency bandwidth of the designed unit cell of the AMC is 1.89:1 (19–36 MHz). Thereafter, a meandered dipole antenna is designed by implementing a binary genetic algorithm and is combined with the AMC. The overall size of the designed antenna is 0.06 × 0.06 × 0.002 λ 3 at the lowest operating frequency. The proposed dipole antenna with a ferrite-loaded AMC is fabricated and measured. The measured VSWR bandwidth (<3) covers 20–30 MHz on the HF band. To confirm the performance of the antenna, a reference monopole antenna which operates on the HF band was selected, and the measured receiving power is compared with the result of the proposed antenna with the AMC. [ABSTRACT FROM AUTHOR]

This letter presents an optimized broadband load network for the Doherty power amplifier (DPA) based on bandwidth balancing between low- and peak-power levels. The optimized broadband load network is composed of a quasi-lumped $\lambda $ /4 impedance transformer (ITF), a modified multiple resonance circuit (MMRC), and a broadband postmatching network (PMN). The quasi-lumped ITF at the carrier amplifier has an optimized characteristic impedance for bandwidth balancing between low- and peak-power levels. The MMRC provides the quasi-lumped ITF with an appropriate susceptance for optimized bandwidth. It also matches the impedance for the peaking amplifier. To validate this design concept, the broadband DPA was implemented using 30-W gallium–nitride high electron mobility transistor (GaN-HEMT) for both carrier and peaking amplifiers. For the down-link long-term evolution (LTE) signal with a channel bandwidth of 10 MHz and a peak-to-average power ratio (PAPR) of 6.5 dB at the frequency range of 1.15–2.45 GHz, DE ranging from 38.4% to 52.2%, and the adjacent channel leakage power ratio (ACLR) ranging from −23.9 to −35.0 dBc at an average output power of from 39.7 to 41.7 dBm were achieved. [ABSTRACT FROM AUTHOR]

In this paper, a Spidron fractal dipole antenna with a ferrite-loaded artificial magnetic conductor (AMC) is presented. By applying ferrite composed of nickel–zinc with a high permeability value, a compact AMC that operates in the broadband frequency range within the high-frequency/very-high-frequency/ultra-high-frequency (HF/VHF/UHF) bands was designed. A Spidron fractal-shaped dipole antenna with a quasi-self-complementary structure was designed and combined with a miniaturized ferrite-loaded AMC. This allowed the designed AMC-integrated dipole antenna to operate in a wide frequency band, covering the HF/VHF/UHF bands, with low-profile characteristics. A prototype of the proposed Spidron fractal dipole antenna with the AMC was manufactured and measured and found to meet low VSWR (voltage standing wave radios) specifications of <3.5 within the 20–500 MHz bandwidth range. The simulated and measured results are in good agreement. The size of the Spidron fractal dipole antenna with the AMC is 0.03 × 0.026 × 0.001 λ 3 relative to the wavelength of the lowest operating frequency. The received power of the Spidron fractal dipole antenna with the AMC was also measured when it was applied to relatively small applications, such as a manpack in this case. [ABSTRACT FROM AUTHOR]

Nanodiamond (ND)‐based nanoparticles with hyaluronic acid (HA) and chlorin e6 (Ce6) were fabricated for potential photodynamic and photothermal tumor therapy. The ND nanoparticles conjugated with HA and Ce6 (Ce6‐ND@HA) had a suitable size range about 130 nm and high zeta‐potential about −35 mV. The conjugation was confirmed by UV‐vis spectroscopy and the conjugation efficiency of Ce6 in these ND nanoparticles was quantified by fluorescence emission spectrum. HeLa and NIH/3T3 cell lines were used as model cells in order to evaluate the performance of ND, ND nanoparticles with HA (ND@HA), and Ce6‐ND@HA. The ND@HA and Ce6‐ND@HA nanoparticles had a selective uptake for HeLa cells due to the presence of HA. In addition, Ce6‐ND@HA nanoparticles had a high cell ablation effect for HeLa cells due to the temperature increase caused by ND and singlet oxygen generation caused by Ce6. These results suggest that Ce6‐ND@HA particles might have potential for targeted anti‐tumor treatment. [ABSTRACT FROM AUTHOR]

This article presents a low-power, all-digital multichannel time-to-digital converter (TDC) for light detection and ranging (LiDAR) sensors. The proposed TDC architecture measures the time interval through a coarse counter, middle, and fine delay line-based interpolation technique (the Nutt method). Automatic calibration by middle and fine all-digital delay-locked loops (ADDLLs) is provided to ensure the stability of the generated time slots. Charge pump, loop filter, and voltage-controlled delay line inside the conventional analog delay-locked loops (DLLs) are replaced by an accumulator (ACC) and digitally controlled delay line (DCDL). This makes the design particularly compact, low power, and suitable for multichannel applications. The presented architecture can generate information for amplitude variation (walk error) compensation. This information is generated by measuring the pulsewidth and position of three successive STOP pulses inside each channel within a single-shot measurement. A low-jitter injection-locked frequency multiplier (ILFM) generates a 625-MHz internal clock signal out of 25-MHz external reference oscillator, which shrinks the number of delay elements to cover one period of the reference clock and improves the precision of the TDC. Operation at higher frequency provides high throughput and short conversion time (less than 3 ns). The three-level TDC offers 13.1- $\mu \text{s}$ maximum input range and 50-ps resolution. The measured DNL and INL of the TDC circuit are 0.47 and 0.71 LSB, respectively. The TDC circuit is implemented in a 180-nm standard CMOS process with a die size of 1.5 mm $\times1.5$ mm. The total power consumption of the multichannel TDC is 87.6 mW. [ABSTRACT FROM AUTHOR]

In this paper, we propose an electrically small antenna consisting of a composite right/left-handed (CRLH) transmission line (TL) and a non-Foster matching circuit. An interdigital capacitor (IDC) and spiral inductor are used to fabricate the very high frequency (VHF) band antenna based on CRLH TL. The size of the proposed antenna is as small as 0.025 × 0.014 × 0.0008 λ at 145.5 MHz using the zeroth-order resonant generated by the CRLH TL. The antenna operation bandwidth is extended by the non-Foster circuit (NFC) consisting of a pair of transistors in a cross-coupled manner. An antenna prototype is fabricated and the input impedance, the received power, and gain of the proposed antenna are measured. The results show that the broadband characteristic is maintained while the form factor is extremely small compared to the wavelength. The average received power enhancement and increased bandwidth of antenna are 17.3 dB and 335.5 MHz (from 249.2–268.2 to 145.5–500 MHz), respectively. The calculated gain of the proposed antenna with the non-Foster is about −45 dBi at 155 MHz. The proposed antenna can be considered as a potential candidate of a low-profile antenna for military ground communications at the VHF band. [ABSTRACT FROM AUTHOR]

In this letter, an electrically small Spidron fractal loop antenna operating in the VHF band is proposed. The ferrite material, which consists of a nickel-zinc combination, is loaded into inside of the loop antenna to increase the gain of the antenna in the low frequency band. To minimize the magnetic loss of the ferrite in the high frequency band, the amount and configuration of the ferrite are optimized using a genetic algorithm. Through this optimization step, the amount of the ferrite is decreased to 37.5% and the gain of the antenna in the high frequency band is improved. The size of the proposed antenna is 0.0242 × 0.0242 × 0.0051 λ L 3 at the lowest operating frequency. The proposed antenna was fabricated to verify the performance, and the simulated and measured results are in good agreement. The measured peak gains varied from −31.6 to −1.9 dBi within the measured frequency band. To examine the performance of the proposed antenna mounted on an unmanned aerial vehicle model (UAV), the antenna on a UAV was also simulated and the results were discussed. The simulated realized peak gains of the antenna on the UAV and on flat ground are similar. [ABSTRACT FROM AUTHOR]

This letter proposes a novel capacitively coupled microstrip comb-line (CCMCA) array antenna for millimeter-wave band applications. The proposed antenna has the advantages of low profile, low cost, and ease of fabrication for the millimeter-wave band. By adjusting the gaps between the radiating strips and feeding line, an antenna with low sidelobe level can easily be designed. To verify the suitability of the proposed antenna for millimeter-wave applications, two arrays (1 × 18 and 4 × 18) were designed and developed at the design frequency of 79 GHz. The measured results show good agreement with the simulated ones in terms of reflection characteristics and radiation patterns. In addition, the CCMCA antenna has stable beam direction even with frequency change, compared to a conventional series-fed microstrip rectangular patch array antenna. [ABSTRACT FROM AUTHOR]

This article presents a 6.78 MHz wireless power transmitter based on a reconfigurable Class-E power amplifier for various and multiple device charging. To maintain high–efficiency for various power receiving devices, an optimized offset transmission line based on lumped components and a susceptance switching circuit are proposed at the load network of the differential Class-E power amplifier. The offset transmission line changes the load impedances of the Class-E power amplifier for the various receivers to the high-power and high–efficiency region. In addition, the susceptance switching circuit further shifts the load impedances of the Class-E power amplifier for some receivers to the high-power and high–efficiency region. To verify the proposed offset line and susceptance switching circuit, a 6.78 MHz wireless power transmitter was implemented and verified for various receivers. For three different receivers, the transmitter maintains optimal transmission efficiencies for received power levels of 39.7, 16.3, and 8.5 W. A peak system efficiency of 81.4% was achieved when the received power is 31.9 W. The system efficiency maintained well around 74.2 and 70.6% for the received power of 16.3 and 8.5 W, respectively. [ABSTRACT FROM AUTHOR]