Search

In this paper, a dual‐polarized multibeam antenna in X‐band is designed and physically fabricated using a parabolic reflector. The antenna consists of a feed array and a metal reflector. A dual‐polarized microstrip antenna array combining two design approaches, T‐coupled feed and defective ground structure, is adopted as the feed array to improve polarization isolation. In addition, the electromagnetic bandgap structure is loaded between the antenna units to reduce the mutual coupling and improve the isolation between the units. A nine element of the highly‐isolated dual‐polarized microstrip antenna array is designed to be placed on the focal plane of the parabolic reflector as the feed, and the beam deflection is realized by using the lateral defocus effect of the parabolic plane, which can finally realize nine single beams covering a 30° scanning range in both horizontal and vertical polarization modes. Based on the scanning state of multiple point beams, this paper uses the Fourier series for beam assignment to form a flat‐top beam with a wide scanning angle. The application of the antenna with two operating modes of wide beam and multibeam to navigational satellite systems can greatly improve the accuracy and efficiency of navigation. [ABSTRACT FROM AUTHOR]

This paper presents a novel wideband circularly polarized antenna that is fed by substrate‐integrated waveguide. Based on the design of placing a pair of chamfered semicircular patches above a slot, a π ${\rm{\pi }}$‐shaped radiator is introduced between the semicircular patches. Multiple resonance points are generated by the combination of the entire radiating structure and a dumbbell‐shaped slot, resulting in improved impedance bandwidth and axial ratio (AR) bandwidth. The proposed element exhibits a wide impedance bandwidth of 50.5% (24.5–41.1 GHz) and an AR bandwidth of 44.2% (25.1–39.3 GHz) with a 44.2% overlapped bandwidth. Then, a 4 × 4 antenna array adopting the sequential rotation technique is constructed. The measured results demonstrate that a 40.6% overlapped bandwidth and a peak gain of 19.1 dBic are achieved. The proposed antenna array shows excellent performance, making it a good candidate for applications in millimeter‐wave wireless communication systems. [ABSTRACT FROM AUTHOR]

An arrayable dual‐polarized antenna is proposed in this paper, which exhibits a low profile and broad bandwidth. A metasurface and a square ring are introduced to realize the broadband operation of the low‐profile dual‐polarized antenna. The total size of the broadband antenna is 0.39λL×0.39λL×0.105λL $0.39{\lambda }_{{\rm{L}}}\times 0.39{\lambda }_{{\rm{L}}}\times 0.105{\lambda }_{{\rm{L}}}$ (where λL ${\lambda }_{{\rm{L}}}$ is the wavelength at the lowest frequency of the operation band [1.31 GHz] in free space), suitable for use as an element of an antenna array. Four elements of the proposed antenna are arrayed to develop an array to demonstrate its application for the base station. The measured impedance bandwidth (return loss >10 dB) of the array is about 70% (1.31–2.74 GHz). Stable radiation patterns are obtained with an average gain of 14 dBi. [ABSTRACT FROM AUTHOR]

Recently, vector beams with special intensity and phase distribution have received much attention due to their unique properties. In this paper, we construct the double‐petal linear edge dislocation (DPLED) beams based on Gaussian vortex beams. The distribution of intensity, polarization, and spin angular momentum (SAM) of the DPLED beams is analyzed in tightly focused based on the Richards‐Wolf vector diffraction theory. The significant difference is occurred in light field, polarization SAM, and polarization distributions before and after focusing of DPLED beams. It's of certain importance for expanding the application of vector beams in optical control, optical imaging, and other fields. [ABSTRACT FROM AUTHOR]

This paper presents the design and prototype development of a compact frequency‐selective surface (FSS) for shielding WLAN signals. The FSS unit‐cell geometry is evolved by modifying the arms of the conventional crossed dipole element. The footprint of the unit cell is only 6 mm × 6 mm × 1.6 mm. The proposed FSS offers stop band characteristics at 5 GHz for both transverse electric (TE) and transverse magnetic (TM) modes. In addition, the FSS offers angular stability up to 60°. A prototype of the proposed FSS is fabricated and measured to validate its simulations. Measured bandwidth of the stop band is 410 MHz, referenced at −20 dB for both TE and TM modes. Equivalent circuit model of the FSS is derived and the results are compared with the simulations. [ABSTRACT FROM AUTHOR]

This paper proposes a programmable solar‐powered radio frequency (RF) transmitter. It employs a novel five‐layer structure that effectively integrates solar cells, active circuits, and broadband antenna. This design can directly emit RF signals without the need for additional power supply, enabling efficient energy conversion and transmission. In addition, a U‐shaped coupling line model is introduced to evaluate the performance of the active circuit. We fabricated a sample and measured it. The results of the measurements indicate that the proposed RF transmitter can achieve self‐powering and programmable output at any frequency within the range of 2.08–4.1 GHz, with an output power of no less than 14 dBm. Moreover, the solar cells are placed on both sides of the circuits and antenna for energy harvesting, achieving 100% sunlight insolation with a 75.5% coverage ratio. This design can be used for self‐powered green wireless system applications. [ABSTRACT FROM AUTHOR]

This paper proposes a broadband optical transparent antenna using a transparent conductor film on a transparent polyethylene terephthalate (PET) substrate. The planar wide‐slot antenna coupling fed by microstrip has a wide impedance bandwidth, so it is selected to design the transparent antenna. The upper surface of the PET substrate is a microstrip line with a fork‐shaped tuning branch, and the lower surface is a wide slot. They were made of transparent conductor film. Finally, a new capacitive coupling method is used to feed the transparent antenna. The transparent conductor film used in the antenna is metal mesh, which was developed by 3M company. The metal mesh with an open area greater than 80% to achieve high transmittance. The measured results show that the impedance bandwidth is 177% (0.30–5.0 GHz), and the gain of the antenna varies from 5.06 to 7.8 dBi over the entire frequency band. Therefore, it can be well applied to the current indoor mobile communication system. [ABSTRACT FROM AUTHOR]

This paper presents a small‐sized, planar antenna fabrication for ultra‐wideband (UWB) and vehicle‐to‐everything (V2X) applications. The design is inspired by a hexagonal ring, providing an UWB bandwidth of 16.61 GHz (from 3.33 to 19.94 GHz) and a fractional bandwidth of 142.75%. A suitably placed inverted‐U slot in the feed line helps in achieving the WLAN notch band (from 5.04 to 6.01 GHz). The overall design footprint is 0.17 × 0.23 λ02 in size, provides stable radiation characteristics, and a gain of 4 dBi in the pass‐band with stable time‐domain performance. The proposed antenna also covers both 3.5 GHz (LTE‐42 Band) and 5.9 GHz (DSRC Band), therefore being suitable for modern UWB frontends and V2X communication. [ABSTRACT FROM AUTHOR]

This paper equates chaff clouds to dipole clusters and studies the electromagnetic scattering problem of dipole clusters based on the linear method of moment (LMM) that solve the electric field Integral equation with the pulse basis function. Firstly, the radar cross section (RCS) of three dipole elements is calculated. The dipole element is divided into 11 segment line units using pulse basis functions. The actual chaff clouds are modeled as two nearest dipole cluster models, which are cubic dipole cluster with uniform distribution formed and spherical dipole cluster with Gaussian distribution formed. The total RCS and total E‐Field magnitude of two dipole cluster models were calculated. Finally, two physical models are constructed based on the simulation models and an experiment is designed. The electromagnetic scattering characteristics of the two models are measured, which verifies the accuracy of the simulation results and the operability of the experiment. [ABSTRACT FROM AUTHOR]

In this paper, a novel source second harmonic manipulation architecture achieving second harmonic control at device input is proposed to solve the issue of reduced operating efficiency of power amplifiers (PAs) caused by the input nonlinearity in continuous Class‐GF mode. The key to the proposed architecture lies in the use of a compact multibranch network to match the source second harmonics of the three design frequency points to the short‐circuit state, which can expand bandwidth while avoiding unexpected efficiency degradation. Considering the necessity of theoretical verification, a broadband continuous Class‐GF PA is designed, implemented, and assembled employing a commercially available 10‐W gallium nitride device. The measured results show that a fractional bandwidth of 100% across 1.1–3.3 GHz with a drain efficiency of 62.4%–72.5%, an output power of 40.1–42.2 dBm, and a gain of 10.1–12.2 dBm are achieved under saturated output power. [ABSTRACT FROM AUTHOR]

This paper proposes a high aperture efficiency (AE) small size tensor holographic impedance metasurface (THIMS), which has the ability to create circular polarized (CP) high purity orbital angular momentum (OAM) multi‐beams with flexibly independent control of the individual beam direction, polarization and OAM mode. The tensor unit cell is a cross‐slotted circular patch. We design a THIMS at 14.6 GHz for dual CP OAM beams: Beam‐I (LHCP, l = 1, θ1 = 30°, φ1 = 0°), Beam‐II (RHCP, l = −1, θ2 = 30°, φ2 = 180°). The developed tensor dual CP THIMS has the following advantages: high purity in xoy plane at z = 9.73 λ (λ wavelength, measured purity 88.4% for Beam‐I, and 93.5% for Beam‐II), high AE 25.1%, and small size 5.986 λ × 5.986 λ × 0.0618 λ. The calculated, simulated and measured results agree well. The generated dual CP OAM beams have potential applications for high‐capacity wireless communication, radar high resolution imaging, and rotation velocity measurement. [ABSTRACT FROM AUTHOR]

The present study focuses on the manifestation of the Doppler effect in low‐Earth orbit (LEO) satellite constellations with laser inter‐satellite links (LISLs). In this letter, the LEO satellite constellation parameters that influence the variation of the Doppler effect in LISLs are presented. The LEO satellite constellation configurations that perform LISLs with less possible Doppler effect could be designed based on the tendency of the Doppler wavelength shift (DWS) as a function of the LEO satellite constellation's parameters. The paper presents the main LEO satellite constellation parameters that involve the variation of the Doppler effect, such as the altitude of the satellites, the orbital plane number within the constellation, and the inclination angle of the orbital plane. In addition to the operating laser wavelength that is employed as a data carrier. These parameters could be helpful to control the Doppler effect in LISL before building an LEO constellation. [ABSTRACT FROM AUTHOR]

This paper presents a Ku‐band divide‐by‐2 direct injection‐locked frequency divider (ILFD) with a wide locking range (LR) and high input sensitivity. The proposed ILFD incorporates an auto‐adjusted injection bias that uses a power detector (PD) to convert the power of the injected signal to a DC voltage. The bias voltage of the injection transistor is then auto‐adjusted in response to the output of the PD. The proposed ILFD employs a 2‐bit switched capacitor array to further enhance the entire LR. Implemented in a 65‐nm CMOS process, the experimental results show that the proposed ILFD achieves an LR of 62.3% (10.5–20 GHz) and 51.2% (11.2–18.9 GHz) at 0 and −10 dBm injection power, respectively. The proposed ILFD consumes 3.6 mW from a 0.6 V supply, and the core area is 0.067 mm2. [ABSTRACT FROM AUTHOR]

This paper proposes a dispersion‐reconfigurable reflection‐type phaser based on the stepped‐impedance microstrip line structure. By configuring "ON" and "OFF" states of switches, the proposed phaser exhibits positive‐slope, negative‐slope, and zero‐slope linearly dispersive group delay responses. For proof‐of‐concept demonstration, we use line connection/disconnection to mimic the ON/OFF states of real switches. Three prototypes are hence fabricated to represent the three different states. The experimental results agree well with the expected responses, which finally validate the proposed concept. [ABSTRACT FROM AUTHOR]

In this paper, we come up with a unique technique to generate the ideal pattern diversity with the help of 24 Vivaldi antennas. With the help of a mathematical concept called golden angle, the 24 antenna elements are arranged in such a way that the radiation patterns will never overlap and the mutual coupling will be very low. It is also verified from the simulations and the measured results that the envelope correlation coefficient is less than 0.01 in the 3–4.2 GHz which is a sub‐6 GHz band for 5G. This same concept can be extended to a greater number of antennas also. [ABSTRACT FROM AUTHOR]

In this paper, a single‐fed broadband circularly polarized (CP) filtering patch antenna based on metasurface is proposed. It consists of a corner‐truncated square patch, a nonuniform metasurface, and a U‐shaped strip. By placing the metasurface above the driven patch antenna, a radiation null is realized at the upper band, and an additional axial ratio (AR) minimum is simultaneously generated to enhance the CP bandwidth. Besides, two more radiation nulls are achieved at each side of the band edges by introducing a U‐shaped strip underneath the patch and embedding a shorting pin into the patch, which further improves the frequency selectivity and suppresses the radiation level. Measured results show that the designed antenna has a wide impedance bandwidth of 19.7% (4.8–5.85 GHz), a CP bandwidth of 19.9% (4.75–5.8 GHz), and an in‐band average gain of 7 dBic with suppression level of more than 18 dB at out of band. [ABSTRACT FROM AUTHOR]

This paper presents the design of multiband frequency reconfigurable patch antenna with switchable radiation pattern and polarization states. The antenna design is based on a circular patch radiator with a pair of metallic strips placed on diametrically opposite sides of it. Circular polarization (CP) from the antenna is excited by etching a pair of slots with a coaxial feed. When the diodes are OFF, the antenna resonates at 4.2, 6.6 GHz, (C band) and 8.07 GHz (X band) and the main beam is located at 0⁰ with CP at X band. The resonance at 4.2 and 8.5 GHz are observed when one of the diode is ON. The main beam at X band is being shifted from −30⁰ to 0⁰ and +30⁰ in the elevation plane during the change in operating modes. Peak gain of the antenna is 6 dBi in all the operating modes. [ABSTRACT FROM AUTHOR]

This paper presents a miniaturized broadband microstrip patch antenna with a simple geometry. The radiation patch of this antenna comprises two rectangular patches with slightly different sizes, one side of each patch is grounded by metal via‐holes. Two rectangular patches are connected by a microstrip line and fed by a single port. Two rectangular patches produce two closely resonant frequencies achieving broadband performance. This antenna operates on the resonant method of short‐circuiting on one side. Metal via‐holes act as a short‐circuit wall allowing each patch to operate in TM0.5,0 mode. The size of a 1/4 wavelength resonant patch is only half of a conventional microstrip antenna, the overall size of this antenna is almost as same as a conventional rectangular microstrip antenna, making it compact in size. The wideband is achieved by combining two radiating patches, resulting in stable radiation and flat gain. Measurement results show that the antenna has an impedance bandwidth of 4.35− $-$5.10 GHz (15.8%) using a common dielectric substrate without air layer thickness additionally. The maximum measured realized gain is 4.61 dB. This antenna has advantages of wide bandwidth, low profile, flat gain and ease of manufacturing. [ABSTRACT FROM AUTHOR]

A waveguide‐fed reflector antenna with high gain and multi‐beam capability is introduced and demonstrated at 220 GHz. Terahertz waves have a very small wavelength, which poses great challenges to the fabrication of terahertz antenna arrays and the connection with the T/R components. In this paper, a horn array with an element spacing less than one wavelength for terahertz frequency is presented and demonstrated, and its excitations are fan‐out using curved waveguides. The horn array is used as a feeding source of an offset parabolic reflector to achieve high‐gain and multi‐beam performance. The reflector antenna achieves four beam positions with θ = −0.7°, −0.2°, 0.2°, and 0.7°, and each beam obtains the gain of about 45 dBi. The experimental reflector antenna is fabricated and tested. Good experimental results further confirm the feasibility of the antenna and the potential application in Terahertz systems. [ABSTRACT FROM AUTHOR]

The paper proposes a circularly polarized dual band single feed microstrip monopole antenna. The proposed antenna consists of a radiating patch, a shrink ground plane, and a 50 Ω microstrip transmission line feed. The radiating patch is a combination of three modified metallic strips, a modified rectangular strip and a semicircular strip. The ground plane consists of two modified open ended slots. The substrate area of the antenna is only 40 mm × 42 mm × 1.6 mm. The antenna has been designed by HFSS simulation software and after getting simulated results the antenna has been fabricated to verify its results. The antenna provides measured bandwidths (−10 dB impedance bandwidth) of 600 MHz (2.2–2.8 GHz) in the lower band and 2.1 GHz (7.5–9.6 GHz) in the higher band. The measured results show its 3 dB axial ratio bandwidth of 120 MHz (2.2–2.32 GHz) for lower band and 1.4 GHz (7.2–8.6) GHz for the upper band. The high measured peak gain of 8 dBi has been obtained from the proposed antenna. The lower band is useful for WiMAX application and upper band is useful for C band application. The desired radiation patterns (RHCP and LHCP) have been obtained from the proposed antenna. [ABSTRACT FROM AUTHOR]

In this paper, the researchers offer a miniatured design of microstrip lines based on magnetic resonance imaging (MRI) coils that can be utilized to detect tumor tissues and to restore those tissues after radiotherapy. A 61.67% reduction in size was achieved in the MRI array dimensions when compared to the previously reported MRI coils. The reliability of the design specifications was verified. The proposed MRI coils could contribute two resonant modes. Primarily, these MRI coils were suitable for homogenous magnetic field and they enable radio frequency (RF) heating by generating a concentrated electric field |E|. The collective temperature and specific absorption ratio (SAR) have been estimated at Larmor frequency. In this study, it was possible to create a uniform magnetic flux density |B1| field operating at 500 MHz. These proposed coils were excited at 8.06 GHz. When simulating cancer in a biological system, healthy tissues were introduced into a Class A scenario and malignant tissues were introduced into a Class B scenario. According to these two scenarios, tumor tissues were magnetically (|B1|) homogeneous with a 44.1% standard deviation with rapidly raised temperature at 4.77°C. These MRI coils delivered an impact on diagnostic imaging and parallelly restored the cancerous tissues by hyperthermia. [ABSTRACT FROM AUTHOR]

This paper presents a novel scheme to online measure the birefringence of the sensing fiber in all‐fiber optic current transformer (AFOCT) system, which monitors the current on direct current (DC) transmission lines using the Faraday magneto‐optic effect in sensing fibers. In this scheme, by purposefully varying the difference of square‐wave modulated phases via the phase modulator in the AFOCT system, different system transmittances can be obtained. On the basis of the relationship between the system transmittance and linear and circular birefringences, an online measurement scheme of both the linear and circular birefringences of the sensing fibers can be established. In this scheme, the AFOCT system is described by the transmission model based on the Jones matrices, with which the current on DC transmission lines can be measured from the phase shift caused by the Faraday effect. Then, under different square‐wave modulated phases, the system transmittance models are constructed with respect to the linear and circular birefringences of the sensing fiber. For a given sensing fiber with certain linear and circular birefringences, the specific system transmittances are determined and are the curves in space in the respective system transmittance models. Subsequently, these curves in space can be projected onto the coordinate plane composed of the linear and circular birefringence coordinate axes, where the intersection point of the projected plane curves gives the to‐be‐measured values of the linear and circular birefringences of the sensing fiber. The proposed scheme is validated by the preset linear and circular birefringences of the sensing fiber, with different linear birefringences of the polarization‐maintaining fiber. The measurement results show the values consistent with the preset ones. [ABSTRACT FROM AUTHOR]

A variable universe fuzzy proportional‐integral‐differential (PID) algorithm was designed and first application for a laser power stabilization system. To validate the algorithm's effectiveness, it is applied to the simulation model of Simulink and the experimental system based on an acousto‐optic modulator. The results demonstrate that the variable universe fuzzy PID presents higher control precision, better robustness, and can suppress long‐term drift phenomena compared with the traditional feedback control algorithm. The algorithm design method in this paper has significant reference and guidance value for laser power stabilization system. [ABSTRACT FROM AUTHOR]

Ultra‐wideband (UWB) radar imaging is widely used in penetration detection, target location and detection, and vital monitoring because of its high interference immunity and excellent target recognition with high resolution. In this paper, we report the design of a UWB stepper radar imaging system by using a vector network analyzer and a specially designed novel Vivaldi antenna for far‐field imaging applications. An anti‐attenuation backward projection (AA‐BP) algorithm is proposed to alleviate the attenuation impact of electromagnetic wave propagation. The AA‐BP algorithm and the specially designed Vivaldi antenna are jointly applied in our experiments on multiple targets through wall imaging in both free space and multiple‐path propagation environments. The experimental results show that our reported imaging system achieves desirable performances of far‐field imaging. [ABSTRACT FROM AUTHOR]

In this paper, a circularly polarized metasurface antenna for microwave energy harvesting (MEH) is proposed. First, a 4 × 4 metasurface is analyzed and integrated with the microstrip slot based on characteristic mode analysis for broadband, low profile, and high gain metasurface antenna. The measured results show that the impedance bandwidth of the metasurface antenna is 1.82 GHz, the 3 dB axial ratio bandwidth is 0.96 GHz. Subsequently, a wideband rectifier for C‐band is fabricated and measured according complex impedance compression theory. The frequency of efficiency >50% is from 5.1 to 6.3 GHz with 17 dBm input power. Finally, the novel antenna and rectifier are connected as rectenna for MEH, which shows great potential due to the tunability of the polarization mode (right‐handed CP [RHCP]/left‐handed CP [LHCP]) and the flexibility of the structure. [ABSTRACT FROM AUTHOR]

In this paper, a polarization‐independent optical transparent absorber with a notch band has been designed, fabricated, and experimented. The proposed structure is composed of three layers made of indium tin oxide (ITO) films with different surface resistances separated by polydimethylsiloxane substrates, which can realize ultra‐wideband absorption. The absorber presents two discrete absorption bands in the frequency range of 3.65–28.82 and 37.72–43.69 GHz, and reflective behavior from 31 to 36.57 GHz. Compared with existing notched band absorbers, this proposed structure has obvious advantages such as structure stability, polarization insensitivity, simple structure, and ultra‐wide absorption bandwidth up to 155%. The prototype was fabricated and a reasonable agreement was obtained between the simulated and measured results. [ABSTRACT FROM AUTHOR]

This paper presents two waveguide quadrature hybrids in the WR‐3 band, which are designed to be fabricated by computer numerical control milling process with relaxed branch width requirements. An E‐plane four‐branch directional coupler gives an amplitude imbalance less than 0.8 dB and a phase difference between 88° and 94° from 240 to 324 GHz. Another design is an H‐plane bandpass coupler composed of cavity resonators, showing a bandwidth of 2% near 300 GHz. [ABSTRACT FROM AUTHOR]

In this paper, the radiative near‐field method has been employed to transfer power through a triangular patch microstrip array that had not been used for this application previously. Additionally, the FR4 substrate is utilized to further reduce the system cost. The system comprises two identical array antennas functioning as both transmitter and receiver. Each array consists of four triangular patches with a side length of 38.5 mm and operates at a frequency of 2.4 GHz. The distance between the two arrays is 50 mm, placing the system in the radiative near‐field category of wireless power transfer. This two‐array system enables the evaluation of power transfer efficiency. The system's performance is improved compared to that of a single triangular patch, and it is also studied in terms of changes in distance. As expected, reducing the distance enhances the system's performance. Subsequently, the structure is fabricated, and the measurements validate the simulation results. The simulation and measurement results exhibit good agreement. [ABSTRACT FROM AUTHOR]

A novel compact microstrip second‐order lossy bandpass filter (BPF) based on an improved simplified composite right‐/left‐handed zeroth‐order resonator (ISZOR) is presented in this paper. The microstrip ISZOR (MISZOR) features miniature topology and ample adjustable physical parameters accompanied by its easily controllable zeroth‐order base mode and first harmonic. Its layout can be quickly generated by applying the implicit space mapping technique. By virtue of the lossy coupling matrix synthesis method, the finite unloaded quality factor of the MISZOR can be taken into account in advance to foretell the insertion loss level. A new definition of the external quality factor as well as its full‐wave extraction method is introduced, enabling the targetted second‐order lossy BPF to be directly implemented as in the classical lossless design, despite the existence of the parallel resistor loaded nonresonant node at each terminal. A succinct inductive coupled microstrip corner is conceived to achieve the relatively strong terminal coupling strength. The exemplified lossy BPF centers at 3.1 GHz with a fractional bandwidth of 5%, which is automatically optimized with the Nelder–Mead simplex algorithm. A prototype measurement is carried out, and good agreement is achieved with simulation, testifying the proposed design concept. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic analysis of a moving infinitely long line source illuminating an infinitely long metallic wire at rest. The study uses the full‐wave numerical finite difference time domain (FDTD) method, which is based on the spatial and temporal discretization of Maxwell's equations. Movement is computed within the FDTD technique by varying the position of the line source at each time loop. An analogy is proposed between the wavelength spectrum of the simulated electromagnetic field and the Compton scattering experiment. A good agreement is obtained between theoretical analysis, numerical results, and Compton experimental data. [ABSTRACT FROM AUTHOR]

This paper describes the design of a broadband, unidirectional coupler designed using complementary metal oxide semiconductor technology. The proposed coupler achieves high isolation by using a differential mode suppressor, employing a differential splitter, followed by a common mode combiner. An intermediary network is used to match all stages to the ports. The coupler, fabricated using United Microelectronics Corporation 180 nm RF/MM technology, achieves better than 15 dB isolation from 0.2 to 1.5 GHz. For this band, it achieves a near flat coupling of 5 dB. The net coupler area is 0.443×0.232 $0.443\times 0.232$ mm2. Such broadband unidirectional couplers can be used in network analyzer testsets. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC) is a polymer widely used in the world whereas safety problems owing to PVC aging are often reported. Thermal‐oxidative aging is known the main cause of its performance deterioration and lifetime decreasing. The existing PVC aging detection methods are complicated, making it difficult to achieve rapid on‐site diagnosis. The purpose of this paper is to evaluate the degree of PVC aging by means of terahertz technology. Samples were subject to thermal‐oxidative aging, and the corresponding dielectric spectra were measured by a terahertz time‐domain spectrometer. It turns out that the aging dependent dielectric spectra conforms to the physicochemical theory. Moreover, numerical correlation between the change in permittivity and the degree of aging, underlying a new solution for the aging forecast aimed at plastics. [ABSTRACT FROM AUTHOR]

The utilization of unmanned aerial vehicles (UAV) has become prevalent nowadays. UAVs are autonomous devices, except for self‐charging. Wireless power transfer (WPT) technologies eliminate human intervention in UAV charging and enable independent charging. The factors making WPT systems popular are autonomizing charging, eliminating cable complexity, and avoiding difficulties caused by environmental conditions. WPT of the UAV in the near field is provided by inductive coupling. In this paper, two vertical rectangular coils and horizontal DDD (triple rectangle) coils were placed in the receiver and the transmitter for UAV wireless charging, respectively. The design of the coils was made in ANSYS Maxwell 3D. A wireless charger of the UAV was designed for 100 W output power at 140 kHz frequency. The misalignment tolerance of the proposed design concerning the x‐ and y‐axis was examined. In addition, the magnetic flux density and magnetic field distributions of the WPT system were investigated. The study found that the proposed design can transfer energy wirelessly with 94% efficiency up to 10.3 cm horizontal and 1.7 cm vertical misalignment. [ABSTRACT FROM AUTHOR]

Logic gates are an indispensable part of digital circuits, and therefore such devices with fast operating speeds and simple designs are vital for all kinds of electronic applications. This paper proposes simple Y‐shaped designs of all‐optical AND, OR, and NOT logic gates in two dimensions that are operational in both TE and TM modes. These gates are designed using silicon slab waveguides, which makes them relatively easy to fabricate. The logic gates are designed, analyzed, and optimized at 1.55 µm using the finite difference time domain method. The truth tables of the proposed all‐optical logic gates are realized for every input case. The propagation delay time is determined to be of the order of femtoseconds (10−15 s), which is very fast compared to the response time of the currently reported all‐optical logic gates (10−9 ‐ 10−12 s). [ABSTRACT FROM AUTHOR]

This paper presents a WR‐2.2 band (330–500 GHz) waveguide with E‐plane bends and a waveguide bandpass filter. A micro‐metal additive manufacturing technology employs copper to process these devices. This technology includes several micromachining processes, which can produce integrated, miniaturized, and complex three‐dimensional metal microstructures when meeting the process constraints. To successfully apply this technology to the fabrication of terahertz waveguide devices, many design details are considered. First, the E‐plane bent transition structures in the waveguide overcome size limitations imposed by the manufacturing process, allowing for accurate measurement using standard waveguide interfaces. Second, the rectangular resonators compose the fifth‐order waveguide bandpass filter spanning 20 GHz with a center frequency of 380 GHz. Given that the excess photoresist needs to be removed, some release holes are designed in the proper positions of the filter. Third, to increase the uniformity of the device layout and improve the machining quality in the electroforming process, a lot of rectangular holes are arranged around the device. By adopting a meticulous and novel design method in accordance with the process advantages and limitations, the fabrication accuracy of the device size is greatly increased. The integrated filter with exceptional performance is obtained. The measured average insertion loss within the passband is better than 1.2 dB, and the return loss exceeds 15 dB. Additionally, the filter demonstrates a center frequency offset of approximately 0.5%. Good consistency between simulation and measurement shows the validity of design and fabrication. [ABSTRACT FROM AUTHOR]

Photoacoustic spectroscopy (PAS) is a highly sensitive optical detection technique for trace gases. However, PAS is sensitive to environmental factors such as temperature and pressure during actual measurement. In this paper, we study the interference characteristics of temperature and pressure in PAS gas detection. The influence of pressure and temperature on PAS is theoretically analyzed based on the basic principle of gas photoacoustic spectroscopy. The effect of different pressure and temperature conditions on the resonance frequency and signal amplitude of PAS is studied through COMSOL software simulation and validated through experiments. Results show that changes in temperature and pressure will affect the resonance frequency and signal amplitude of PAS, thereby impacting the system's sensitivity and accuracy. To reduce the impact of temperature on the PAS sensor, a temperature compensation model was derived based on experimental analysis. Real‐time temperature detection is used to compensate for the photoacoustic signal based on temperature changes, which can improve the accuracy and stability of photoacoustic spectroscopy gas detection. For 5% CO2, the photoacoustic signal and experimental temperature data were measured for 3612 s, and after temperature compensation, the detection limit was 0.0192% at an integration time of 365 s, which is 0.0128% higher than before temperature compensation. The system's normalized noise equivalent absorption coefficient is 3.30 × 10−8 cm−1 WHz−1/2. This research improves the accuracy and reliability of photoacoustic spectroscopy gas detection technology and provides useful references for temperature correction in similar gas detection fields. [ABSTRACT FROM AUTHOR]

In this paper, the volumetric shooting and bouncing rays method is proposed to investigate the electromagnetic (EM) scattering of the large‐scale target coated with plasma, which takes into account the EM rays propagating inside the interior of the plasma and fully captures the dominant scattering characteristics. Furthermore, an efficient graphics processing unit‐based implementation procedure with a ray management strategy is proposed to deal with the problem of the exponential increase of EM rays in plasma medium. The numerical results of a multilayer cuboid model and the RAM C‐II vehicle demonstrate the proposed method has a good computational efficiency and achieves a significant accuracy improvement compared to the traditional shooting and bouncing ray, with a root mean square error reduced from 13.29 dB to less than 4.96 dB. It indicates the proposed method has the potential to solve the EM scattering of the large‐scale target coated with plasma. Finally, some simulations of the RAM C‐II are performed at higher radar frequencies to illuminate that the plasma sheath causes complex scattering of the target of interest in terms of the flight speed, flight altitude, and radar frequency. [ABSTRACT FROM AUTHOR]

This paper presents a novel metasurface antenna element and a novel metasurface antenna array, both of which have broadband low radar cross section (RCS) performance. The antenna element is constructed by two kinds of H‐shaped metasurface unit cells. One kind of H‐shaped metasurface unit cells is properly fed to radiate, and the other unit cells are used to cancel the scattering field from the former. Thus, an integration of metasurface and antenna is performed and broadband low RCS is obtained. Furthermore, a H‐shaped metasurface antenna array is also proposed by deliberately introducing metallic vias for isolation. Both the proposed antenna element and the array have almost the same radiation performance with conventional patch antennas. Numerical calculations and experimental measurements are conducted. The results verify the effectiveness of the proposed novel antennas. [ABSTRACT FROM AUTHOR]

This article proposes a method to solve the decoupling problem between asymmetric antennas based on common mode and differential mode cancellation theory. The coupling between two asymmetric antennas can be analyzed and mitigated by exciting two signals simultaneously. To verify the feasibility of this theory, a pair of asymmetrically coupled planar inverted‐F antennas are proposed in this paper. Simulation and experimental results show that this method provides a good theoretical foundation for decoupling between asymmetric antennas. Compared with traditional decoupling techniques, it can obtain good performance, and the design scheme is simple and easy to implement. [ABSTRACT FROM AUTHOR]

This paper presents an additive manufacturing technique to design and prototype a reflective metasurface antenna for Ka‐band applications. The dielectric cuboidal element with an air‐filled void is designed to act as a unit cell for designing a three‐dimensional (3D)‐printed phase‐graded metasurface reflector. The designed phase‐graded metasurface reflector is a 3‐bit quantized highly reflective surface, designed by rigorous unit cell optimizations. The quantized unit cells are distributed to provide a 45° phase gradient and wideband reflections operating from 24 to 38 GHz. The designed reflector is excited by a wideband 3D‐printed horn antenna placed at the optimized focal point. The simulated and measured results indicate the designed antenna achieves a maximum gain of 23.66 dBi with a gain enhancement of 60%. The designed antenna is found to have a 1 dB stable gain bandwidth of 4 GHz, from 28 to 32 GHz with a maximum gain of 23.66 dBi at 30 GHz. [ABSTRACT FROM AUTHOR]

In this paper, we used the liquid phase stripping method to manufacture MoS2–SnSe2 heterojunction saturable absorber (SA). The scanning electron microscope, the atomic force microscope, and the Raman spectrometer were used to characterize the MoS2–SnSe2 heterojunction SA. The Q‐switched mode‐locked (QSML) Nd:GGG laser with MoS2–SnSe2 heterojunction SA was presented. The maximum output power of the QSML Nd:GGG laser was 236.4 mW with a repetition rate of 83.3 MHz and pulse width of 447 ps. In short, the MoS2–SnSe2 heterojunction nanosheets present excellent saturable absorption characteristics. [ABSTRACT FROM AUTHOR]

To meet the requirements for parameter testing within the projectile test system, a computational model for calculating the echo power of the projectile passing through the detection screen based on the principle of active laser detection target is established in this paper. On the basis of the fundamental formula of echo energy in laser detection, and by combining the energy distribution function of the detection screen, the light scattering cross‐section formula specific to the projectile, and the illuminated area formula when the projectile intersects the detection screen, the formula for calculating the echo power of projectile is derived and analyzed. Furthermore, taking into account the parameters of the laser detection target, a computational model is constructed to calculate the voltage amplitude associated with the echo power of the projectile. Combining the atmospheric transmission optical characteristics, distance variations, and changes in the projectile's reflection attitude in the test environment, we conducted a simulation analysis to assess the accuracy of the established calculation model. Additionally, experimental analysis of the echo power calculation model was performed. In both simulation and experimental analyses, the trends in the impact of atmospheric transmission optical characteristics, distance conditions, and changes in projectile attitude upon the calculation of projectile echo power were consistent. Moreover, the width of the projectile echo waveform obtained in experiments was equal to the calculated projectile duration time. These research findings can serve as a reference basis for the development of theories in laser detection target. [ABSTRACT FROM AUTHOR]

Optically transparent dual‐band frequency‐selective surfaces (FSSs) are promising candidates to address the specific design challenges of the Internet of Things. This paper demonstrates their potential by discussing different configurations of the two single‐layer FSS designs on an innovative optically transparent polyvinyl chloride surface material. First, FSS cells consist of two cross dipoles placed forming angles of ±45∘ $\pm 4{5}^{\circ }$, where each rotated dipole structure parallel to the other. Then, in the second design, each one of the two cells is mirrored to enable polarization control for each band. As a proof‐of‐concept, five prototypes of each design having a unit cell size of 0.43λ0×0.43λ0 $0.43{\lambda }_{0}\times 0.43{\lambda }_{0}$ are fabricated through a combination of cost‐effective printing and shearing. The manufactured prototypes yield more than 93% transparency and robust dual‐band performance. Moreover, more than 20 and 40 dB isolation for lower‐ and upper‐frequency bands are achieved from the fabricated prototypes. High‐transparency, cost‐effectiveness, and robust high performance in terms of suppression make both structures suitable for sub‐6‐GHz fifth generation applications. [ABSTRACT FROM AUTHOR]

As a representative technique in electronics, the Smith Chart provides a fast, less‐computation, and graphical approach to solve the problems related to impedance matching. In this paper, we transplanted the Smith Chart into the design and analysis of a microwave metamaterial absorber (meta‐absorber) to develop an analytical and graphical approach for impedance matching of electromagnetic wave absorption. Before the structural design, four traces on the Smith Chart plane from the load to arrive at the impedance matching point (the center of the Smith Chart) can be graphically found to obtain perfect absorption. Then, we have designed four impedance matching circuit networks made of resistance, inductance, and capacitive elements and transmission lines to fit the four traces. Then, the matching circuits are mapped into the meta‐absorber structure by using three types of proposed layers. The full simulation method based on the finite element method is used to verify the proposed concept. Furthermore, an external dielectric loading strategy has been developed to achieve good angular stability up to 60° for the radar cross section reduction under transverse electric and transverse mangetic polarization incidence. The proposed method may provide a convenient way for various microwave devices, such as antennas. [ABSTRACT FROM AUTHOR]

This paper proposes a new Padé via Arnoldi algorithm with single‐size matrix simplification for electromagnetic (EM) fast frequency sweep. New equations are derived to reduce the double‐size system matrix to single‐size system matrix. We also propose a systematic algorithm to calculate S‐parameters using the simplified single‐size system matrix. Using the proposed algorithm, the EM responses can be obtained with the same accuracy while consuming much less time compared with that using the existing double‐size matrix Padé via Lanczos. The proposed algorithm is demonstrated by two microwave examples. [ABSTRACT FROM AUTHOR]

This paper presents the generation of an orbital angular momentum (OAM) wave using a wire antenna with a skew planar wheel structure at 5.8 GHz. The wire antenna consists of four arms, each of which behaves like a left‐handed circularly polarized antenna. The orientation and rotation of each arm are adjusted to obtain the desired phase shift, resulting in the generation of an OAM wave. The proposed design is fabricated and tested, and the results demonstrate that the OAM beam produced has high mode purity, with a peak gain of 2.8 dBi, divergence angle of ±30° $\pm 30^\circ $, and high azimuthal symmetry. Both simulated and measured results confirm the effectiveness of the proposed wire antenna in generating an OAM wave. The proposed wire antenna has a wide range of potential applications, including communication systems, remote sensing, and radar imaging. In particular, the azimuthal symmetry of the OAM beam makes it particularly suitable for unmanned aerial vehicle applications. [ABSTRACT FROM AUTHOR]

A filtenna (filtering antenna) for the fifth generation (5G) mobile communications in millimeter‐wave (mmWave) band is proposed in this paper. The filtenna is fed by a probe, and two radiation nulls are generated at the upper sideband based on the stacked‐patches structure. Then, two shorting pins loaded on the driven patch are introduced, which then result in the third radiation null. An "X‐character" shape radiation loop is added therefore, the fourth radiation null can be generated. Besides, the fifth radiation null at around 34 GHz is generated by adding four parasitic strips on the top radiation patch. The measured −10 dB impedance bandwidth of the filtenna is from 23.07 to 30.99 GHz. The average gain of the antenna is larger than 5.5 dBi, and the stopband suppression can reach 14 dB with a wide stopband. With the merits of low profile, wide stopband, and stable radiation, the proposed filtenna can be a good candidate for 5G mmWave applications. [ABSTRACT FROM AUTHOR]

A high‐gain high‐selectivity 4 × 4 metasurface (MS) filtenna array is presented in this paper for 5G millimeter‐wave (mmW) applications. The TE20‐mode substrate integrated waveguide (SIW) with two parallel coupling slots is applied as the differential feeding structure, which can produce a wide impedance bandwidth and good radiation performances, simultaneously. Additionally, the TE20‐mode SIW feeding line is well designed to operate as a λ/2 short‐circuited line at the upper edge frequency to gain a radiation null. Meanwhile, a folded U‐shaped slot is etched on each MS unit to generate a radiation null at the lower edge. As a result, a passband which covers our 5G mmW band (24.25–29.5 GHz) of interest can be realized. To validate the design, a 4 × 4 MS filtenna array was manufactured and measured. The simulated and measured results are in good agreement, demonstrating a −10 dB impedance bandwidth of 19.8%, a flat gain variation with a maximum value of 19.82 dBi, symmetrical radiation patterns, low cross‐polarization levels of –30 dB, and high out‐of‐band rejection levels of 25 dB. [ABSTRACT FROM AUTHOR]

This paper extends previous work on electromagnetic (EM) reciprocity theorem analysis from the single‐conductor to the more general multiconductor transmission line (MTL) case. The focus is on the EM coupling problem of an ideal MTL above a perfectly electrically conducting ground when excited by a plane wave. The proposed methodology addresses mutual coupling effects and mismatched loads in the MTL. The expression for the current along the MTL in the test (radiation) state is derived, considering these factors. A novel calculation method for the induced voltage at the load is then introduced, assuming consistent coupling between different lines in both test and receiving states. Numerical examples validate the proposed EM‐reciprocity method, offering an alternative approach for analyzing the field‐to‐line coupling problem in MTL model. [ABSTRACT FROM AUTHOR]

In this paper, an X‐band dual‐band dual‐polarized medium‐gain antenna (MGA) is designed for deep‐space satellite applications. The MGA has isoflux radiation patterns in the 7.145–7.19 and 8.40–8.45 GHz frequency bands. The concentric ring horn qualification model named MGA is developed for TIAN WEN‐2 (TW‐2) mission. MGA is fabricated and the measurements are conducted on it and its installation on the deck of the TW‐2 Radiation Mockup (RM). The performance evaluation of MGA and its corresponding RM measurements indicate an axial ratio lower than 4.0 dB and a gain higher than 5.8 dBic on the operational bandwidth at the coverage limit of 40° for all azimuth angles (φ). The calculated and measured data align exceedingly well, confirming that MGA satisfactorily meets the requirements for the forthcoming TW‐2 deep‐space spacecraft. [ABSTRACT FROM AUTHOR]