A tunable third‐order bandpass filter (BPF) with constant fractional bandwidth (CFBW) is presented. Only two quarter‐wavelength resonators have been used in comb‐line fashion to design the third‐order BPF. The physical dimensions of the resonators have been decided to satisfy the filter specifications by synthesizing the coupling matrix. Using modal voltage waveform analysis, locations of the varactors

This study is dedicated to the comprehensive design of a compact circularly polarized microstrip antenna and the integration of essential properties of stable phase center, broad bandwidth, and wide beamwidth into that antenna. Such a compact antenna in electronically low size was firstly achieved by technically using paired fragment‐type crossed dipoles and applying multi‐objective evolutionary algorithm

The authors present the complete characterization of two cost‐efficient photonically integrated slotted lasers that offer regrowth free manufacturing. Furthermore, the application of these devices, as multi‐carrier transmitters is also investigated. In particular, the authors employ gain switching, an optical frequency comb (OFC) generation technique based on the direct modulation. The first device

The laser ultrasonic technique (LUT) enables the analysis of complex signals and the extraction of the features of defects. The time‐domain features can be used to quantify various defects, but are negatively affected by the coupling efficiency, measurement noise, and surface roughness during LUT. This paper describes defect analysis methods based on the power spectral density and wavelet packet energy

In this article, a novel lens antenna with wide beamwidth using three‐dimensional printing is proposed. The proposed antenna is comprised of a concave lens by using three‐dimensional printing, a lantern shaped patch with a parasitic ring, and eight loaded monopoles around the center. The antenna operating frequency is 5.8 GHz, and the prototype is implemented. The measured half power beamwidth are

Different from previous phase gradient metasurfaces, in this letter we show that the spoof plasmon polariton conversion is dominated by the high‐order surface wave modes rather than the pre‐defined linear phase distribution. The latter becomes invalid due to the coupling between different metallic unit cells of the metasurface. To demonstrate this point, a metasurface, which includes six different

Ti:sapphire laser has an important position in ultrashort pulse generation and wavelength tuning. The use of expensive frequency‐doubled diode‐pumped solid‐state laser as the pump source limits the promotion of its application to a certain extent. With the maturity of high‐power blue‐green laser diodes (LDs), low‐cost LD directly pumped Ti:sapphire laser becomes possible. After more than 10 years of

A closed‐form solution for the continuous inverse class E (class E−1) design space is presented for the first time1. Analogous to the class‐E power amplifier (PA) modes, the zero current and its derivative conditions needed for the class E−1 switching action can also be shown to be satisfied with any second harmonic susceptance. The complementary relationship between the continuous PA modes for class

This article presents a rectifier array for wide ranges of input power and frequency. The rectifier array was configured using two sub‐rectifiers and a 3‐dB branch‐line coupler to recycle the reflected input power through impedance mismatch, thereby extending the input power range. The two‐section branch‐line coupler is merged with matching networks to improve the power conversion efficiency (PCE)

In this article, a compact triple‐mode balanced passband filter with intrinsic common‐mode (CM) suppression is designed by using a single isosceles right triangle perturbed half‐mode substrate integrated waveguide (HMSIW) cavity. The perturbation metallic vias are introduced to tune the first three resonant modes of HMSIW cavity to form a passband. Furthermore, the planar differential microstrip‐pin

This article presents the design of a broadband high‐efficiency power amplifier (PA) with a compact coupling structure. In theory, the output matching network impedance expression based on the compact coupling structure is derived. According to the load impedance range of the class EFJ PA, the coupling structure is deduced to meet the impedance range of the class EFJ PA. This structure can realize

In this study, the bandpass filter characteristics in standing wave resonator formed in a two‐dimensional (2D) photonic crystal (PC) is integrated with microelectromechanical systems (MEMS) actuator to tune degenerate mode split. A single and sequentially connected indirect coupling structure consisting of waveguide as well as cavity is placed to the 2D PC. It has been shown that the modes of the bands

In this paper, a thirty‐second‐mode circular substrate integrated waveguide resonator (TMCSIWR) is firstly investigated, which well retains the fundamental mode and high‐order modes (TM0n0 modes) in circular SIW resonator (CSIWR) for stable transmission. Considering miniaturization, high Q and multi frequency selection of TMCSIWR systematically, each TM0n0 mode in TMCSIWR can be effectively selected

Agarose is a stable hydrophilic material commonly used for relative humidity sensing application. Agarose porous nature causes changes in its refractive index as relative humidity change. Micro bottle resonators are a promising choice for sensing applications due to their good quality factor. In this work, the effect of agarose gel concentration on micro‐bottle ability to detect relative humidity changes

This letter presents a novel impedance transformer that can transform two unequal frequency‐dependent complex loads (FDCLs) to a resistive load at two diverse bands. The proposed transformer contains four sections of transmission lines and one shunt stub. The design parameters of the transformer are obtained from the analytical formulas. The feasibility analysis of the transformer is discussed and

A complete, non‐approximate expression of the internal impedance for an open‐ended circular cylindrical wire being subject to externally incident radiation is derived. A comparison is made with the well‐known formula given by Stratton and later given by Ramo. The modes in which the electromagnetic field oscillates are due to the incoming wave, and the corresponding boundary conditions do not lead to

An antenna cable for enhancing and adjusting radio coverage is proposed. The presented solution is applied to the UHF RFID range of 866 MHz. With this leaky‐wave antenna cable, radio coverage can be efficient and customizable. A 10 × 100 mm resonator patch is attached on an opening on the cable's outer conductor to improve its radiating properties. The effect of its displacement is studied through

3D Gaussian beam generation techniques have been studied by many researchers, while the problem of 2D Gaussian beam generations have not been addressed fully. However, 2D Gaussian beams are still useful in research and applications. This article presents the mechanism, design, simulation, and measurement of a 2D Gaussian beam launcher, which allows the easy control of the width and the location of

A dual‐channel glucose concentration sensor based on coupled cross‐stacked gratings is proposed. When the concentration of glucose solution is varied from 30 to 60 g/100 ml, the maximum values of the bulk sensitivity for peaks at longer and shorter resonance wavelength indicate approximately 615.57 and 262.94 nm/RIU, respectively. Therefore, the sensitivity of channel at longer wavelength is increased

In this paper, a near field focusing transmission metasurface (MS) based on polarization sensitivity is developed at microwave frequency. The MS unit cell has only three metal layers, which is less than the published dual‐polarized transmission structure. And the phase shifting range can cover 320° for x‐ and y‐polarized waves. The biggest bright spot of the focusing MS made of the proposed units is

This article presents a W‐band preamplified power detector (PD) monolithic microwave integrated circuit (MMIC). The chip consists of a pseudomorphic high electron mobility transistor (pHEMT) PD with a six‐stage low noise amplifier (LNA) in a commercial 0.1‐μm GaAs pHEMT technology. In order to reduce the high risk of oscillating in a multistage LNA, a circulator‐based method for LNA interstage stability

This letter presents a lower phase noise voltage‐controlled oscillator (VCO) uses two differential amplifiers in cross‐coupled feedback and is named as a buffer‐reused VCO in the TSMC standard 0.18 μm SiGe BiCMOS processes. The die area is 1.1 × 1.2 mm2. The first amplifier uses HBT stacking on nMOSFET and the second amplifier uses nMOS amplifier. Its power consumption of 2.65 mW with output buffer

In this letter, a novel wideband circularly polarized (CP) crossed dipole antenna with frequency reconfiguration is proposed. By introducing two quasi‐Sierpinski fractal orthogonal dipoles printed on both sides of the substrate, compact, broadband and low cross‐polarization characteristics are achieved. The proposed antenna can be switched flexibly over two frequency bands via controlling the states

This paper shows a technique to enhance the radiation gain and efficiency of metamaterial (MTM) inspired planar antenna using substrate integrated waveguide (SIW) technology for sub‐6 GHz wireless communication systems. The antenna consists of MTM unit‐cells comprising series interdigital‐capacitor and short‐circuited spiral stub. The proposed antenna behaves like a leaky wave antenna. In the transmission

This article proposed a novel compact coplanar waveguide (CPW) fed flexible wideband antenna. The antenna is composed of hexagonal radiation patch, rectangular slots and trapezoid ground. The antenna works in 5.2–41 GHz (154.98% fractional bandwidth) range with a return loss of −10 dB. Based on thin liquid crystal polymer (LCP), the antenna has an overall size of 23.6 mm × 15.4 mm × 0.1 mm. The presented

This article presents a ring‐shaped antenna array for multistatic microwave breast imaging. The antenna element uses a compact double‐ridged waveguide probe operating from 3 to 6 GHz, and its radiation performance is experimentally verified in a lossy immersion liquid with a pass loss of −0.67 dB/mm. Eight antenna elements are integrated into a 150 mm diameter ring structure that sufficiently surrounds

In low earth orbiting satellite communication systems, antennas are key elements for radio frequency transmitters and receivers. There are different types of antennas used on satellite communication systems. One of them is the antenna used in payload data transfer communication subsystem. Payload data transmitters for space segment should utilize the radio frequency power efficiently due to the limited

In this article, a simple coaxial‐feed filtering patch antenna based on stub‐loaded resonator is investigated and analyzed. Owning to the addition of a pair of parasitic stubs, the original rectangular patch antenna acquires a new resonance point and an out‐side radiation null beyond the upper band edge. Then, by establishing a transverse path (introducing connected stubs), the radiating and filtering

In this article, a three‐port circularly polarized (CP) multiple‐input multiple‐output (MIMO) antenna for wireless local area network (WLAN) application with pattern and polarization diversity is proposed. The proposed MIMO antenna system comprises of a broadside CP antenna element with a T‐shaped slot and two endfire CP antenna elements. Good impedance bandwidth of 16.9% and 5.5% are achieved by the

This article presents the design of a highly integrated twelve port ultra‐wideband (UWB) antenna array for multiple‐input multiple‐output (MIMO) communications. The proposed array consists of a unit cell element constructed using a circular arc structure excited by a simple microstrip line feed terminated by an arc‐like stub. The proposed unit cell antenna covers 3–9 GHz covering most of the third

In this article, we present a novel half mode substrate integrated waveguide (HMSIW)‐based bandpass filter fed antipodal tapered slot antenna. We employ a novel feed consisting of three horizontal slots with two gaps arranged periodically on the top metal layer of HMSIW to obtain |S11|<‐10 dB and |S21|≃0 dB over the passband from 21.6 to 40 GHz. We incorporate sinusoidal corrugations at the antenna

A low‐profile broadband patch array antenna with a wide scanning range is presented at X‐band. The antenna element consists of the stacked patches, the sheet resistances and the metallic posts with a total thickness of 3.27 mm. The stacked patches are excited by a stripline‐fed aperture with four edge patches surrounding the bottom patch. The sheet resistances and the metallic posts provide a solution

In this article, the authors have proposed a right‐handed circularly‐polarized array antenna with gap waveguide (GWG) distribution network at 35 GHz. By using GWG technology, the strict electrical contact of different layers is not required so that the expensive vacuum welding or the diffusion bonding technology can be avoided. The entire geometry consists of the top radiation layer and two distribution

To identify different modes of orbital angular momentum (OAM) vortex beams after demultiplexing, deep learning technology is introduced, and a convolutional neural network (CNN) model is designed to detect OAM beams. The light intensity distribution maps of the Laguerre Gaussian beam with the topological charge from 1 to 20 through experiments are collected, the random phase screens are generated by

In this article, a low‐profile and high‐gain multi‐beam antenna is proposed. The antenna consists of a cylindrical Luneburg lens based planar beamforming network, a folded double‐layer guided‐wave structure, and a leaky wave antenna (LWA) array. All the three parts are manufactured by 3D printing technology. The lens is realized by an n‐shaped gradual thickness unit to realize the refractive index

We report a novel approach for realizing tunable/reconfigurable terahertz (THz) mesh filters on the basis of micromachined mesa‐array structures. In this approach, different filter patterns are generated virtually using photogenerated free carriers in a semiconducting mesa‐array structure to achieve superior tunability and reconfigurability. Micromachined mesa‐array structures enable the formation

In recent years, various kinds of optimal design approaches are intensively studied for exploring novel and higher performance microwave and optical devices beyond human knowledge. In this article, we first apply a design approach based on Bayesian optimization (BO) to design of dielectric flat lens which is expected to be used in microwave and millimeter wave region because of its excellent features

A novel fast‐adaptive weighted hybrid‐shaped M‐ary quadrature amplitude modulation (HS‐MQAM) format is proposed in this paper. By introducing a fast‐adaptive weighting factor array related to geometric shaping and probabilistic shaping, the non‐linear impairment is mitigated and the bit error rate (BER) and mutual information (MI) performances are further improved. The simulation results show that

A 2 μm passively Q‐switched Tm:YAP solid‐state laser with MoS2 as saturated absorber was demonstrated in this work. MoS2 two‐dimensional materials were prepared by using the method of chemical vapor deposition. The laser achieved high peak power of 21.2 W and high single pulse energy of 19.5 μJ, while maintaining a short pulse width of 916 ns. This is the first time that the peak power of a Tm:TAP

The technology of long‐distance power supply with high‐power laser (HPL) over single‐mode fiber (SMF) is of great significance in specific environment. The nonlinear effect of fiber and photovoltaic conversion (PC) efficiency are the key factors restricting the application of this technology. The wide linewidth laser and cascaded long period fiber grating (CLPFG) band rejection filter are used to suppress

Lidar is an active remote sensing instrument, and it has been widely used in the detection of atmospheric environmental parameters and meteorological parameters. In recent years, climate change has been widely concerned by the public, and the corresponding atmospheric detection technology has also been developed rapidly. Atmospheric Lidar has been developed rapidly in China, and has achieved good research

This article describes a methodology for designing broadband high‐efficiency GaN HEMT power amplifier (PA) which is suitable for base stations and modern wireless communication based on the Class‐EF mode. To achieve both efficiency enhancement and bandwidth extension for the PA, the load‐pull technique is employed to acquire the optimum impedance regions of the second harmonic. Especially, considering

This paper describes a metamaterial‐based miniaturized circularly polarized (CP) antenna with high radiation efficiency and wide beam‐width or coverage for 5G indoor application. A novel meta‐resonator is first proposed, which is investigated by transmission line and equivalent circuit models. By exploring a split‐ring resonator‐like meta‐resonator structure, a high‐Q LC resonator tank is formed. Substantial

This paper presents an aperture matched parabolic pyramid horn antenna (APPHA) having flaring in the E‐ and H‐ plane. The proposed structure is designed and manufactured for S‐band (2.2–3.3 GHz) with a semicircular aperture matched section in both planes. The APPHA gives half power beam width (HPBW) less than 17° and 15° in the E‐ and H‐ planes, respectively due to the parabolic profile and aperture

In this letter, an improved small‐signal equivalent circuit model of InP heterojunction bipolar transistors (HBTs) for millimeter‐wave applications is presented. The proposed small‐signal model takes into account the parasitic effect in the collector part which can effectively improve the accuracy of S parameter. In the frequency range of 2–110 GHz, good agreements between the measured and model‐calculated

A novel miniaturized wideband antenna based on a hybrid L/T‐shaped metasurface structure is proposed, which is fed by an aperture coupling through a microstrip line. To realize the miniaturization of the metasurface antenna, the hybrid L/T‐shaped metasurface structure composed of several L‐shaped metal patches and T‐shaped metal patches is firstly presented. By placing the L‐ and T‐ shaped metal patches

A fast and nondestructive method for predicting density and compressive strength of Lightweight Foamed Concrete (LFC) is proposed. The measurement is carried out using a frequency domain approach to determine the Lightweight Foamed Concrete dielectric constant from a frequency range of 150 kHz to 8 GHz. The relations of the dielectric, density, and compressive strength of lightweight foamed concrete

We propose a hybrid full duplex passive optical network with fusion of wavelength‐division‐multiplexing and orthogonal frequency‐division multiplexing (WDM‐OFDM) for a radio‐over‐fiber (RoF) system application. The key of the system is a tunable optical frequency comb (OFC) embedded cascading modulators and a parameter mixer. Moreover, 23 frequency components with 0.6 dB flatness generated by the OFC

We propose a simple design of all‐fiber Q‐switched erbium‐doped fiber laser (EDFL). The laser is passively Q‐switched by splicing bismuth‐doped fiber into a ring cavity. The design has been experimentally demonstrated at the emission wavelength of 1560.48 nm. A single‐mode Q‐switched pulse with pulse duration of 1.18 μs and pulse energy of 15.6 nJ was obtained with 980 nm pump power of 178 mW. Stable

In this paper, we demonstrate a new two‐dimensional Dammann grating element to generate equilateral‐triangle hexagonal spot array distribution with equal intensity. This type of grating is constructed by rotating two one‐dimensional Dammann gratings through an angle of 60° to form a triangular hexagonal array illumination. In this work, a 7 × 7 spot array Dammann grating is fabricated by using electron

This article presents a 130 nm SiGe BiCMOS four‐channel satellite communication receiver. Phased‐array system has become the optimal solution for satellite communication due to the electrical steering nature. In order to obtain wider bandwidth, higher precision of phase shift and smaller chip size, an improved quadrature network and a phase compensation technique are proposed in this article. Each

In this invited paper, we present an overview of the multi‐pixel photon counter (MPPC), which is a kind of spatial‐multiplexed photon‐number‐resolving detector. We review the operation principles of MPPC, its characterization via quantum detector tomography, and the applications of this detector in research fields such as quantum information, remote sensing and biological medicine. Finally, we discuss

Unique features of terahertz (THz) wave have made THz spectroscopy a potential and ideal tool for spectroscopy analysis. When a conventional THz spectroscopy system is used to measure a sample with birefringence, sometimes it is highly possible to misinterpret a polarization filter effect as normal spectral absorption, thus leads to a wrong identification and conclusion. Polarimetric terahertz spectroscopy

We propose and numerically validate an all‐optical scheme to generate a train of optical pulses. Modulation of a continuous wave with a periodic binary temporal phase pattern followed by a spectral phase shaping enables us to obtain ultrashort pulse trains. An ideal step phase profile as well as a profile arisen from a bandwidth‐limited device is investigated. Analytical guidelines describing pulse

Dynamic population gratings formed by two‐wave mixing in an erbium‐doped fiber amplifier are reported. One of the counter‐propagating fields is intensity‐modulated to distinguish reflection from the grating from amplified transmission fields. The modulation‐frequency dependence of the reflection is studied under single‐wavelength and two‐wavelength input conditions to separate reflection from transient

Discarded aluminum alloys are a form of recyclable metal materials, and their classification and identification are highly important. In this work, laser‐induced breakdown spectroscopy (LIBS) technique combined with principal component analysis (PCA) and least‐squares support‐vector machine (LSSVM) algorithm were used to classify and identify five types of aluminum alloys. Exploratory analysis of five

An efficient method has been developed to analyze metal species by using laser‐induced breakdown spectroscopy (LIBS). A least squares support vector machine (LSSVM) was applied to quantitative analysis of multimetal samples with different matrix content, as LSSVM can select the input variables and convert the mapping to the feature space to obtain the linear performance. In this work, three kinds of

A sensitive intensity modulation differential optical fiber angular displacement sensor has been developed. The influence of the distance between the end face of the emitting fiber and the reflecting surface, the tilt angle of receiving optical fiber and the surface reflectivity on the performance of the sensor was analyzed. The optimal geometric parameters of the sensor structure were obtained based

We present a temperature‐sensitive, single‐mode–multimode–single‐mode (SMS) fiber structure with an index‐matching gel as a cladding material in a multimode segment. A silica core with the surrounding gel is supported straight by a thin glass tube to produce a bandpass transmission response. The passband wavelength shifts by 96 nm from 1624.5 to 1528.5 nm as the temperature increased from 40 to 200°C