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This paper proposes a novel approach to enhance the computational efficiency and precision of the ultra‐wideband characteristic basis function method based on compressive sensing for calculating the wideband radar cross section (RCS) of objects, which involves the development of a new method for filling measurement matrix and constructing sparse basis. While randomly selecting rows from the original impedance matrix as the measurement matrix, the proposed method also avoids the double‐filling of equal elements in the measurement matrix. Furthermore, the Foldy–Lax equation is utilized to construct the merged ultra‐wideband characteristic basis functions (MUCBFs) at the highest frequency, and the sparse transform of the induced currents is performed using MUCBFs as the sparse basis. The numerical simulation results show that this method not only reduces the calculation effort of impedance matrix filling, but also effectively improves the calculation precision of the target wideband RCS. [ABSTRACT FROM AUTHOR]

This paper presents a novel two‐element partially dielectric loaded planar Vivaldi antenna array for ultra‐wideband applications. This array is capable of operating between 380 MHz and 3 GHz and is designed on a 1.6‐mm thick low‐cost FR4 substrate with total size of 25 × 330 × 430 mm3. Innovative approaches to various gain enhancement techniques such as partial dielectric loading, corrugations, and U‐shaped back reflector used for planar Vivaldi antennas, are collectively employed in this design. Various elements of the array are interconnected. The two‐element Vivaldi array is fed by using a power divider. The array is designed by using a full‐wave three‐dimensional EM simulation tool. The designed antenna is manufactured and then measured. The simulation and measurement results are found to be consistent with each other. [ABSTRACT FROM AUTHOR]

An ultrawideband de‐embedding calibration method (DCM) for a dual probe is proposed in this paper. Different from the conventional calibration method (CCM), in which a microstrip calibrator and the dual probe form a three‐port calibration network, the proposed calibration system is a four‐port network. By using two different lengths of grounded coplanar waveguide (GCPW) calibrators, namely line‐kit and through‐kit, the de‐embedded S $S$‐parameter model of the calibration network is obtained. Measured results show that the ripple of the DCM with GCPW reduced by 59% of the CCM with the microstrip calibrator, and the phase delay has been almost compensated. In addition, the proposed method reduces the attenuation by approximately 0.7 dB at 10 GHz and 1.15 dB at 20 GHz. The calibration results indicate that the working frequency of the DCM is up to 22 GHz. [ABSTRACT FROM AUTHOR]

Optical fiber current transformers (FOCTs) are affected by various external factors, resulting in the deterioration or even failure of devices, causing changes in critical state quantities, and reducing the accuracy and reliability of products. To solve this problem, based on the neural network algorithm, this paper starts from the four deterioration characteristics of FOCT SLD junction temperature, SLD output optical power, phase modulator half‐wave voltage, and optical fiber sensing ring temperature, and identifies the deterioration of key optical components of FOCT, which provides a basic model and data support for the online monitoring and early warning to improving the stability and reliability of FOCT in long‐term operation. [ABSTRACT FROM AUTHOR]

This paper presents a dual‐band multiple‐input multiple‐output (MIMO) antenna pair for 5G cell phones. The antenna pair consists of two planar concave antenna elements that are tightly arranged on a vertical substrate. By adding capacitors to form a resonant network, an additional operating mode is excited, resulting in dual‐band performance. The resonant frequency of the additional mode can be adjusted independently by changing the capacitance value. Moreover, a neutralization line is used to improve the isolation of the high band without affecting the low band. The antenna pair occupies a small area of 13.2 × 6.3 mm2 and operates at both 3.5 and 4.85 GHz bands. The isolations are better than 17 dB at the 3.5 GHz band and better than 19 dB at the 4.85 GHz band. The proposed dual‐band antenna pair might be a good choice for 5G terminals. [ABSTRACT FROM AUTHOR]

A single‐feed wideband circularly polarized (CP) substrate‐integrated waveguide (SIW) cavity‐backed antenna and its phased array are presented in this paper. The proposed element consists of SIW cavity, stacked patches, and a 50‐Ω coaxial probe. The coaxial pin is directly connected to the two patch radiators. By chamfering on each rectangular patch, the proposed SIW cavity‐backed patch antenna realizes wideband circular polarization characteristic. The proposed element exhibits a simulated impedance bandwidth of 22.5% (14–17.6 GHz) for |S11| < −10 dB, an axial‐ratio (AR) bandwidth of 12.9% (14.5–16.5 GHz) for AR ≤ 3 dB. Simulation results illustrate that the infinite array can scanning up to ±60° in all planes over the operating frequency, under the criterion of active VSWR ≤ 3 and AR ≤ 3 dB. For verification purpose, an 8 × 8 array prototype was manufactured and measured. To achieve better CP characteristics, the sequential rotation technique is applied to the full array configuration. The measured results show good agreement with simulation results. [ABSTRACT FROM AUTHOR]

A front‐end MMIC working at 37–43.5 GHz for 5G high‐performance channel emulator is presented in this paper. The chip is fabricated in a 0.1‐μm commercial GaAs pHEMT process and integrated with a passive star mixer and a local oscillator (LO) chain, which is composed of a frequency tripler, a bandpass filter, a power amplifier, and an LO filter. The 10.5 GHz intermediate frequency (IF) signal is upconverted with the high frequency LO signal of 48–54 GHz through a passive double‐balanced star mixer, which can output 37–43.5 GHz radiofrequency signal. The high frequency LO can avoid the increase of bit error rate caused by the frequency band of input signal covering IF frequency. The conversion gain of −11.2 to −9.7 dB, the OP1‐dB of −0.26 to 1.7 dBm are achieved and the front‐end chip occupies an area of 2.78 × 0.9 mm2. [ABSTRACT FROM AUTHOR]

Indirect far field (IFF) over‐the‐air (OTA) test could be one of the most applicable test methods for 5G mmWave devices. The compact antenna test range (CATR) method has been introduced to the OTA test by 3GPP. Conventional metallic parabolic reflectors without edge treatment can lead to serious edge diffraction which results in high noise and low accuracy. The serrated reflector improves edge diffraction but performs poorly at low frequencies. Reflector antenna with a resistance frequency selection surface (RFSS) frame is proposed for 5G OTA CATR measurement at millimeter frequency, which collimates spherical incident waves into quasi‐plane waves in a relatively short distance, thus forming a quiet zone (QZ) in which large devices under test can be measured in small chamber. In this paper, the reflector with RFSS is investigated through the numerical and experimental methods, it is found that serrated RFSS frame with low edge diffraction could achieve the excellent QZ, which could be helpful in miniaturing CATR chambers for 5G OTA measurement. [ABSTRACT FROM AUTHOR]

The paper reports the fabrication and characterization of a capacitive Microelectro Mechanical Systems pressure sensor based on through glass vias (TGV), which had a large dynamic range by operating in touch mode. The substrate with TGV offers the advantage of elimination of parasitic capacitances owing to the superior insulation property of glass. The fabrication process was introduced. In particular, anodic bonding was applied in high vacuum to realize the hermetic package to obtain large operating range and high sensitivity. The performance of the sensor with a sensitive diaphragm of 700 μm × 1400 μm was characterized in the pressure range from −80 to 180 kPa. The sensitivity was determined as 0.072 pF/kPa over the range of 160 kPa with a good linearity of 97%. [ABSTRACT FROM AUTHOR]

A compact low‐profile planar filtering antenna with an enhanced suppression level is presented in this paper. The presented antenna has a simple structure, consisting of an E‐shaped driving patch, a shorted parasitic patch, and a defected ground structure (DGS). The E‐shaped driving patch serves as an effective radiator and facilitates the filtering response. The shorted parasitic patch is horizontally arranged and coupled with the driving patch through the radiating edge. And a radiation null and an extra in‐band resonance can be generated, which would simultaneously broaden the impedance bandwidth and improve the suppression level. In addition, a DGS on the metalized ground plane is etched to introduce another radiation null, and the out‐of‐band suppression level would be significantly enhanced. The filtering antenna with a center frequency of 3 GHz was constructed and tested to verify its performance. The measured values, which indicate a bandwidth of 10% (2.85–3.15 GHz) and a peak realized gain of 5.2 dBi, are in agreement with the simulated values. The presented filtering antenna features a low profile of 0.016λ0, a compact antenna size of 0.16λ20, as well as an improved suppression level of more than 22 dB. [ABSTRACT FROM AUTHOR]

In this paper, a study on the effects of strategically implemented holes in a miniaturized wideband bandpass filter (BPF) utilizing interdigital folded coupled lines is presented. First, the BPF is designed to produce the passband by introducing a fold in the coupled lines. The passband is centered at 9.3 GHz (X‐band), catering to radar applications. Coupled lines connected to a modified U‐shaped transmission line comprise the filter's design configuration. The novelty of the design resides in incorporating drilled holes along the coupled lines, which generate perturbations and resonant effects, resulting in enhanced impedance variations and improved filter performance. With the aid of electromagnetic analysis and simulation software, the coupled lines, U‐shaped transmission lines, and drilled hole diameters are all optimized. Vector Network Analyzer performs all the measurements and draws the comparisons. An increment of 22.58% is seen in return loss as it increases from −24 to −32 dB, and the insertion loss shows an increase of 16.74%. The proposed filter has been subjected to analytical study, simulation, and implementation, which have confirmed its exceptional return loss, favorable insertion loss, and compact dimensions. The research results make a valuable contribution to the development of miniaturized wideband BPFs, specifically focusing on their use in radar systems. In such systems, the ability to accurately and efficiently filter signals is paramount. The design insights and performance improvements presented in this study have significant implications for broader applications in microwave engineering and communication systems. [ABSTRACT FROM AUTHOR]

The paper aims to utilize a metamaterial (MTM) structure, specifically the slotted plus‐shapes within a square split‐ring resonator, to analyze the characteristics of the reused oil and also used to classify different oil samples. The proposed MTM structure is designed to operate within the X‐band frequency range of 8–12.4 GHz. The MTM structure is simulated using the high‐frequency EM simulation tool, and the MTM properties are extracted using standard equations. The negative permittivity and permeability characteristics of the proposed MTM structure in the X‐band are studied to verify its suitability for X‐band applications. A sample container is designed to hold the oil samples, and the experiments were carried out using an X‐band waveguide setup with Vector Network Analyzer. The results were analyzed and presented in brief to examine reused oil and classify different oils. [ABSTRACT FROM AUTHOR]

Diversity in design is an important factor that enables developers to explore techniques aiming to reduce cost, complexity, and manufacturability. The optical window around 2000 nm is attracting rapid research considerations for the next generation optical networks as a continuation of C‐, L‐, and U‐bands. Optical amplifier is considered to be one of the major research directions in this optical window. Holmium‐doped fiber amplifier is an appropriate component to amplify signals in this optical window. But, the major issue is the pump laser for pumping the Holmium‐doped fiber (HDF) is that it is costly and not readily procurable. In a pioneering design, the authors introduced a method to pump the HDF using traditional 1480 nm pump diode by taking the advantage of cascaded lasers which were made of Erbium‐doped fiber (EDF) and Thulium‐doped fiber (TDF). In this paper, we propose an alternate method for pumping the HDF using commercially available 1480 nm pump diode by exploiting cascaded lasers implemented using two pairs of reflective fiber Bragg gratings (FBGs) and pieces of EDF and TDF. The EDF in the first laser is excited with a standard 1480 nm pump diode to create 1610 nm continuous wave (CW) laser which is used to excite the TDF in the second laser to generate 1950 nm CW laser that is used to pump the HDF. Peak gain of 40.5, 36, and 23 dB can be attained corresponding to –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Output powers of 10.5, 21, and 23 dBm are obtained for –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Noise figures (NFs) of 5, 4.2, and 4 dB are observed at signal wavelength of 2066.7 nm for signal powers of −30, −15, and 0 dBm, respectively. Penalty of 4.5 dB has been observed both in peak gain and power at 2055.6 nm signal wavelength for signal power of −15 dBm considering the pair induced quenching. Finally, the proposed alternate pumping scheme is compared with the previous pumping scheme in terms of 3 dB gain bandwidth and NF. It has been observed that 88% increase in 3 dB gain bandwidth and 19% decrease in NF at a signal wavelength of 2044.4 nm for signal power of –30 dBm is noticed in the proposed pumping scheme. [ABSTRACT FROM AUTHOR]

In this paper, mechanic–electric–circuit coupling algorithm based on the finite‐difference time‐domain (FDTD) method is proposed to analyze a one‐order microwave bulk acoustic wave (BAW) filter. FDTD method is used to solve the coupled mechanic–electric–circuit system equations to obtain the voltage and current at port position of the BAW filter in the time domain. Then S parameters of the BAW filter in the frequency domain are calculated using the Fourier transform. In our work, a one‐order BAW filter consists of two film bulk acoustic resonators (FBARs) by means of series and parallel. These two FBARs in the BAW filter are coupled together through an equivalent electrical connection. Similarly, multiphysical mechanic–electric–circuit analysis of the BAW filter is implemented in the commercial software COMSOL, which is realized by the time‐domain finite element method. The accuracy of the proposed method is verified by comparison with simulation results in COMSOL. In addition, the computational time and memory of the proposed method have obvious advantages over those of COMSOL. [ABSTRACT FROM AUTHOR]

The impact of tracking errors over the vibration interference is investigated. A novel expression is presented for the bidirectional laser tracking mechanism which takes in account both periscope communication terminal and beam acquisition process with beaconless technology. In this paper, platform microvibrations are measured and compensated to improve the tracking characteristics of the optical communication terminal. An experiment was conducted to verify the high precision tracking system with the combination of coarse and fine tracking technologies, which represents that the fine tracking error is suppressed to 2.1 μrad. This high precision implementation demonstrates the effectiveness of the tracking control loop, and will contribute to the space laser communication. [ABSTRACT FROM AUTHOR]

This paper presents a novel ultra low jitter phase‐locked loop (PLL) circuit architecture for RF Sampling Transceiver. The programmable frequency divider with duty cycle expansion and the new phase frequency detector and charge pump circuit are used to solve the problem of voltage domain conversion of narrow pulses in the traditional high‐performance charge pump PLL structure. The traditional structure degrades charge pump linearity and noise, thus deteriorating overall jitter performance. Furthermore, voltage‐controlled oscillator uses the dual core structure and the second harmonic suppression technology, combined with the proposed new switching capacitor structure, and achieves −139.3 dBc/Hz phase noise at the 1 MHz frequency offset of the 5.2 GHz carrier under the open loop state. The PLL implemented in a standard Taiwan Semiconductor Manufacturing Company 28 nm process occupies a core area of 0.4 mm2 and generates a frequency ranging from 4 to 5.2 GHz using 50 MHz oscillator input, the power consumption is 40 mW. It achieves 74.8 fs root‐mean‐square jitter integrated from 10 KHz to 30 MHz. When the PLL output is divided by 2, the output phase noise at 1 MHz frequency offset is −125.75 dBc/Hz, and the PLL FoM is −246. [ABSTRACT FROM AUTHOR]

The dense establishment of the Wi‐Fi devices creates an opportunity to map the surrounding environment using Wi‐Fi signals as sounding waveforms. Recently, the Channel State Information (CSI) measurement analysis from Wi‐Fi networks has been widely used for detecting and possibly tracking the presence of obstacles between a transmitter and a receiver. According to the IEEE 802.11bf Task Group, Wi‐Fi sensing will utilize a band between 5.925 and 7.125 GHz, making the CSI measurement finer‐grained with the additional large bandwidth. In this paper, a wideband compact antenna is designed targeting the 5.9–7.1 GHz band based on the slot‐loading technique. Later, a wideband multiple‐input multiple‐output (MIMO) antenna is designed using defected ground structures, protruded ground, and electromagnetic band gap structures for isolation improvement, and the measured isolation shows 30–45 dB between the elements in the operating frequency range. The envelope correlation coefficient is less than 0.001 with the diversity gain being nearly 10. The fabricated single antenna has a compactness of 0.3λ0 ${\lambda }_{0}$ in both dimensions (14 mm × $\times $ 14 mm), measured bandwidth of 1.55 GHz (5.95–7.5 GHz) with a peak gain of 2.2 dBi at 6.8 GHz, and 90% efficiency in the operating frequency range whereas the wideband MIMO antenna has a size of 14 mm × $\times $ 37 mm with 0.5λ0 ${\lambda }_{0}$ spacing between the elements. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient optical fiber communication scheme for an optical metro access network (OMAN) based on an optical multicarrier (OMC) generator. The central office (CO)'s foundation is a novel, cost‐effective OMC‐generating technique. The OMC is designed from a pulsed laser source and three cascaded electro‐optic modulators (EOMs) driven by an amplified RF source of 20 GHz signal that has generated more than 60 frequencies with excellent tone‐to‐noise ratio (TNR) ~ 40 dB and amplitude excursions from zero to 3 dB. The conventional CO is replaced with a cost‐effective OMC‐based source with an effective switching mechanism, which is necessary and equally important to be handled reliably. The downstream data of 20 Gbps per carrier is transmitted using a duo‐binary coding scheme. Six remote nodes (RNs) supported by the suggested OMC source, at each RN 10 optical network units (ONUs), can be deployed having distance laps of 5 km between the RNs, the distance between the RNs and the ONUs is kept at 2 km, the ONUs were tested w.r.t the bit error rate (BER) and the power penalties for the proposed transmissions. The BER for different fiber lengths from 5 to 25 km at various RNs and ONUs ranges were calculated and demonstrated from 1e−3 to 1e−13, showing the feasibility of the proposed OMAN. [ABSTRACT FROM AUTHOR]

In this paper, a compact internally matched architecture of continuous class‐B/J Doherty power amplifier is studied. The influence of symmetric generalized combiner and postmatching network with harmonic control on the bandwidth and efficiency of Doherty power amplifier (DPA) is analyzed in detail. Based on the parameters obtained from theoretical analysis, a design method of internally matched continuous mode DPA (CM‐DPA) is proposed, and a broadband DPA with a size of 22.8 mm × $\times $ 24.5 mm was developed for experimental verification. The test structure shows that the maximum output power at saturation can reach 46.2 dBm. The efficiency of 6 dB back‐off is 58%–63.4%, with good consistency. In the reliability experiment, transistor and matching circuit of the CM‐DPA have a temperature below 100°C at saturation. The output power and efficiency tested at different temperatures (25∘ $2{5}^{\circ }$C, −55∘ $-5{5}^{\circ }$C, and 85∘ $8{5}^{\circ }$C) show that the DPA has high reliability. [ABSTRACT FROM AUTHOR]

This paper presents a broadband, high linearity 7‐bit digital step attenuator (DSA) using a low‐cost bonding wire package. Capacitive compensation technique is proposed to offset the deterioration of attenuation accuracy and operating bandwidth caused by the parasitic parameters of the bonding wire and switching transistors. And the negative voltage bias technique (NVBT) is proposed to improve the linearity of the DSA. Based on the capacitive compensation technique and the NVBT, a 7‐bit DSA is implemented using a 0.13 µm Silicon‐On‐Insulator (SOI) process with a low‐cost bonding wire package. The DSA achieves broadband operation with an insertion loss (IL) of 2.7 dB at 7 GHz and root mean square (RMS) amplitude error less than 0.5 dB at DC‐7 GHz. The input P1 dB of all states is better than 31.7 dBm. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel dual‐band quasi‐Yagi antenna for on‐body communications. The proposed antenna is designed on 0.05 mm thin microwave laminate and is designed to cover the 2.45 and 3.5 GHz spectrum to meet the needs of on‐body Internet of Things networks. Microstrip to slot‐line transition is used for the excitation of the feeder element. The conventional feeder of the quai‐Yagi is replaced with F‐shaped radiators to obtain a dual‐band response. In addition, a pair of directors are used to enhance the antenna gain. The proposed quasi‐Yagi antenna is optimized using the spider monkey algorithm. The chosen algorithm is used to synthesize the dimensions of the dual‐band radiator and is preferred to obtain quick convergence, unlike the traditional optimization algorithms. The optimized planar quasi antenna offers 5% bandwidth in both operating bands with a measured gain of 5.7 and 5.8 dBi, respectively. The optimization time is also considerably reduced in comparison with traditional optimization algorithms. The simulated and optimized antenna is fabricated and tested. [ABSTRACT FROM AUTHOR]

The antennas that share radiators with solar cells are applicable to collect energy and integrate radio frequency functions. In this paper, a solar cell integrated multiband antenna is proposed on the basis of Vivaldi antenna structure. Unlike prior research, it has the capacity to reconfigure working frequencies and radiation performance of the antenna through optical control of the solar cell. The purpose of reconfiguration is achieved by means of two switching diodes placed between the differential Vivaldi radiator and conducted via biasing from the solar cell. The integrated solar cell functions both as part of the radiator and as the biasing source for switching diodes. According to the simulation and measurement results, the antenna performs consistently at around 5 GHz, while the radiation performance can be reconfigured at 1.16 and 3 GHz under illumination. In this way, the proposed antenna can fulfill various functions such as green energy collection, wireless communication, and light detection, which makes it applicable in the Internet of Things for low‐power wireless sensor terminal. [ABSTRACT FROM AUTHOR]

A slotted microstrip patch antenna for fifth‐generation (5G) mobile applications is presented in this paper. The proposed antenna addresses the intrinsic narrow bandwidth of patch antennas by introducing rectangular slots in the form of a disjointed H‐slot to broaden the bandwidth. The patch design and the slots introduce two extra resonances to broaden the bandwidth of the antenna. An impedance bandwidth of 26.6% from 24.95 to 32.6 GHz was achieved. A measured peak gain of 9.44 dBi was also achieved with a minimum half‐power beamwidth of 36° over the entire bandwidth. The proposed slotted patch antenna is implemented on a 44.6 mm × 26.3 mm × 0.8 mm RT5880 Printed Circuit Board. [ABSTRACT FROM AUTHOR]

In this paper, a compact diode‐pumped continuous wave (CW) and passively Q‐switched mode‐locked (QML) Tm:YAG lasers operation on the 3F4–3H6 transition is realized by using tantalum aluminum carbide (Ta4AlC3) phase ceramic (MAX) material as a saturable absorber (SA). The first stable QML operation of the mid‐infrared Tm:YAG laser at 2012.38 nm is demonstrated with a Ta4AlC3‐SA. A stable QML Tm:YAG laser was achieved when the absorption pumping power reached 14 W. Under QML mode, Tm:YAG laser generated a maximum average output power of 560 mW at 2012.38 nm with an optical‐to‐optical conversion efficiency of 4%, corresponding to a shortest pulse duration of 541 ps and a high repetition rate of 168 MHz. The experiment shows that Ta4AlC3‐SA is an attractive candidate for diode‐pumped CW and QML mid‐infrared all‐solid‐state lasers emitting around 2.0 μm. [ABSTRACT FROM AUTHOR]

In this paper, a modified rhombic‐shaped wide‐flare two‐arm antenna is proposed for super‐wideband applications of the next generations of mobile technologies. To enhance antenna input impedance and to improve its performance, the copper arms are lithographed on a dielectric substrate with multilayers and fed through a wideband balun that is designed to feed the balanced two‐arm antenna through the conventional (unbalanced) coaxial line. The proposed antenna is fabricated for experimental validation of the simulation results. It is shown through electromagnetic simulation as well as experimental measurements that the proposed antenna is operational in the range of frequencies (2.3‐23 GHz $2.3 \mbox{-} 23\unicode{x0200A}\mathrm{GHz}$). Parametric study is performed to obtain the optimum design of the proposed antenna. The distributions of the surface current on the antenna arms at different frequencies are presented and discussed for more understanding of the antenna operation over the entire frequency band. It is shown that the antenna has a radiation efficiency of greater than 96%, percentage bandwidth of 164%, ratio bandwidth of 10, bandwidth‐to‐dimension ratio of 1360, and maximum gain that exceeds 5 dBi $5\unicode{x0200A}\text{dBi}$. [ABSTRACT FROM AUTHOR]

This paper reports a MEMS tuning fork gyroscope which can effectively reduce the acceleration output in both drive and sense directions. The structure adjusts the order of mechanical vibration modes through the design of internal and external lever coupling mechanism, moves the spurious in‐phase mode frequency above the antiphase operating frequency, and provides a large frequency separation between the two modes. It provides true mechanical rejection of external shocks and accelerations. Two comparative tuning fork gyroscopes (TFG) structures are designed, which have traditional coupling in the drive direction and sense direction respectively. Through modal simulation, the internal lever‐coupling brings the antiphase drive mode before the in‐phase drive mode and the external lever‐coupling brings the antiphase sense mode before the in‐phase sense mode. The harmonic response simulation of three stiffness unbalanced TFGs verifies that the mode ordering of two directions can effectively suppress the acceleration output. The results show that the new TFG structure can suppress the acceleration output by more than 80%, and the finite element simulation results are consistent with the theoretical calculation. [ABSTRACT FROM AUTHOR]

Since the software‐defined radio digital beamforming (DBF) system is the newest tendency in fifth‐generation (5G) development and based on its flexibility applied to antenna arrays, this research paper presents a smart antenna array architecture operating in C‐band (3.48 GHz). In developing DBF for 5G access points with beamforming capacities, it is first necessary to perform an accurate approach that identifies the position of the desired user and affects the beamforming processing. In this article, a feasible approach is represented to evaluate and test three angle‐of‐arrival algorithms. To ensure the robustness of the system, the system structure with its four main components, the transmit subsystem, the synchronization subsystem, the receive subsystem, and data processing are described in detail. This article presents a reasonably inexpensive prototype DBF in conjunction with a Universal Software Radio Peripheral B210 board. Experimental measurements and results confirm the suggested methodology. [ABSTRACT FROM AUTHOR]

With satellite laser communication, advantages can be achieved in high communication rate, precise beam pointing, high confidentiality, and light‐small terminal. Satellite–ground (SG) laser links also play a crucial role as trunk links. However, the SG link is influenced by atmospheric turbulence and platform vibration, these two factors will cause unstable link tracking. This paper focuses on the viewpoint of beam energy transmission, using the low‐frequency harmonic phase compensating method to establish the random phase screen. On the basis of this model, the laser beam energy distribution and the spot mass positioning error are analyzed considering turbulence taking vibration which is not considered in previous studies. The simulation results show that the spot mass center (SMC) is impressionable in strong turbulence under platform vibration, but in a weak turbulent environment, SMC is insensitive to vibration when turbulence and vibration are at the same noise level. [ABSTRACT FROM AUTHOR]

Antennas with complex radiation characteristics can enhance the adaptability of radiofrequency systems in complex electromagnetic environments. However, The realization of complex targets is extremely challenging for conventional antenna design methods. It is difficult to find a suitable initial topology of the antenna with complex radiation characteristics. Therefore, in this paper, topology optimization is used to explore the initial structure with complex radiation properties. A two‐dimensional lossy thin layer model based on the transitional boundary condition is constructed, and target field functions for complex radiation are proposed. To verify the effectiveness of the algorithm, a high gain antenna with 10.2 dBi is realized, which has the highest aperture efficiency compared with the literature in similar directions. Then, for more complex targets, the radiation patterns of arbitrary direction null, arbitrary direction beam, and equal‐amplitude dual beam are realized, respectively. The topology optimization algorithm provides a new approach for the design of complex multitarget antennas. [ABSTRACT FROM AUTHOR]

To monitor the concentration of harmful gas methane (CH4) in the tunnel in real time, a high‐sensitivity measurement method for CH4 trace gas based on tunable diode laser absorption spectroscopy (TDLAS) is designed in this paper. An interband cascade laser with the emission wavelength of 3.29 μm was used to target noninterference CH4 lines at 3038.5 cm−1. To diminish the background noise of the sensor system, wavelength modulation spectroscopy combined with a second harmonic measurement technique was used in this work. Finally, 1.83 parts per billion in volume (ppbv) minimum measurement limit (MML) was obtained with a 4 s integration time based on an Allan‐Werle variance analysis, and the MML can be further improvedto ∼0.4 ppbv by increasing the integration time up to 104 s. Indoor and outdoor environmental data of CH4 acquired using the TDLAS sensor system are also reported. [ABSTRACT FROM AUTHOR]

Aiming at the application of Sub‐6 GHz band, this paper presents a high isolation four‐port MIMO slot antenna with CPW feeding mode. About this antenna, two parallel binary antennas are oppositely arranged with connected ground, and isolation branches are adopted to improve isolation. Each element antenna is realized through elliptical shape patch and trident structure feed line. The measured results show that its working frequency band is 1.82–6.5 GHz band, with ports isolation less than −20 dB. In addition, its other performance parameters are good, such as gain of 7.03 dB and ECC parameter below 0.004, and CCL is less than 0.3 bps/Hz. The antenna has high isolation and it can not only work in the mobile communication frequency bands such as n41, n77, n78, and n79, but also work in the frequency band of the IoT, such as WiFi5, V2X, and DSRC. [ABSTRACT FROM AUTHOR]

This paper demonstrates a compact‐size folded slot‐based antenna suitable for internet‐of‐things (IoT) applications. The antenna is composed of a folded structure meandered slot loaded with varactor diode. The novel combination of the slot and varactor diode, reactively loading the slot, lead to highly miniaturized antenna. The presented antenna operates in dual frequency bands: from 730 to 965 MHz and 1250 to 1940 MHz. Continuous frequency sweep over the two bands is achieved by the use of a single varactor diode. Due to antenna compact size, it is highly suitable for 5G IoT applications. The total board dimensions of the proposed design are 27 mm × 27 mm. [ABSTRACT FROM AUTHOR]

A circularly polarized high gain hybrid rectangular patch/horn antenna with chamfered corners is presented in this paper. The measured impedance bandwidth of the proposed design extends from 26.7 to 28.7 GHz. The suggested design antenna exhibits circular polarization propagation over the working band, which is achieved by introducing chamfered corner overlapped patch antennas surrounded by the truncated pyramidal horn. The main purpose of this horn is to enhance the overall gain without any deterioration of other antenna characteristics (more than 4 dB over the operating band when compared to the patch antenna). The maximum measured gain of the hybrid antenna is 10.9 dBi. The radiation patterns of the hybrid antenna show directive broadside radiation with stable performance over the whole frequency band. The suggested antenna is analyzed and designed applying both the numerical simulator (CSTMWS and HFSS). [ABSTRACT FROM AUTHOR]

It is well known that accurate estimation of the loop delay between the input and output feedback signals is the key to behavioral modeling and digital predistortion of power amplifier. Nevertheless, most of the traditional loop‐delay compensation algorithms have the disadvantage of high computational complexity. For the purpose of solving this problem, a loop‐delay estimation algorithm based on sliding window has been proposed in this paper, where the first derivative characteristic of the signal is employed to evaluate the correlation between the input and output feedback signals. The simulation and experiment are carried out with different bandwidth signals in this paper. The results show that the proposed algorithm and the traditional cross‐correlation‐based method could align the input and output feedback signals successfully. But in terms of resource consumption, the proposed algorithm could reduce the multiplier nearly by 100% and the adder by approximately 93.2%. [ABSTRACT FROM AUTHOR]

The letter presents the design, fabrication, and measurement of a configurable radio frequency identification (RFID) tag based on time-domain reflections. The tag circuit contains a microstrip line (ML) that propagates radio frequency (RF) signals, and a group of capacitors that introduce impedance discontinuities to encode binary codes. The configurability of the tag circuit is allowed by connecting the nearby-placed capacitors with the ML. Ink-jet printing technology is employed to implement the layout of the proposed tag on paper substrate. To overcome the limitations of printed metallic tracks, a linearly tapering technique is proposed. With this technique, a four-bit configurable passive chipless RFID tag is realized. Both time-domain reflectometry (TDR) measurements and ultrawideband (UWB) characterizations were conducted for the proposed tag, and the results are in good consistence with the simulation ones from the circuit simulator advanced design system (ADS). Owing to its low cost fabrication and environmentally friendly nature, the proposed tag has great potential to be widely employed in low-end RFID applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2781-2786, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26412 [ABSTRACT FROM AUTHOR]

This paper presents a novel technique to evaluate OSNR using asynchronous histograms. The technique is based on a comparison between a numerically estimated asynchronous histogram of the signal to be measured and the monitored signal. Experimental validation of proposed technique is presented. Measurement errors below 1 dB are achieved for OSNR values below 32 dB. The proposed technique is also validated for cases where the monitored signal presents significant dispersion-induced distortion, without presenting significant loss of accuracy. The principal limitations of the proposed technique are also investigated. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1369–1372, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21648 [ABSTRACT FROM AUTHOR]

Stimulated by an injected continuous wave, a set of longitudinal modes wins the competition for gain medium continuously. In this paper, the linewidth of the longitudinal mode is broadened by the injected continuous wave. The wavelength of an actively mode-locked fiber laser based on EDFA is stabilized in the experiment. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1385–1388, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21645 [ABSTRACT FROM AUTHOR]

A novel large signal compact modeling for GaN HEMT has been proposed in this paper, and the harmonic mean is used to simulate the I‐V curves, combining the saturation and the linear region. The traditional compact modelings has two typical forms, the empirical modeling and the physical modeling. The empirical modeling is accurate and fast, but lacking the physical meaning. On the contrary, the physical modeling derived from the physical equation, is more complex, with the low speed and the poor convergence. This novel modeling inherently has both advantages, the fast speed, and so forth, and the physical meaning. The saturation region covers the most states of the power amplifiers, and Chih‐Tang Sah equation with clear physical meanings is adopted in this region. In linear region, on the contrary, the current varies more steeply with the voltage, and thus the empirical formula is used. [ABSTRACT FROM AUTHOR]

This paper proposes a broadband metasurface antenna with size‐varying patches. The metasurface radiator is fed by a microstrip line through a coupling slot on the ground. By varying two parameters of the square patches, great mode controllability can be achieved, resulting in wideband and stable gain. Furthermore, the added slotted metal square ring can effectively improve radiation gain. We designed and tested a C‐band wideband antenna consisting of 4 × $\times $ 4 novel radiator units. The measured impedance bandwidth and 2‐dB gain bandwidth are 59% (4.3–7.9 GHz) and 44.1% (4.6–7.2 GHz), respectively. The designed antenna has a low profile of 0.09 λ $\lambda $. [ABSTRACT FROM AUTHOR]

The frequent cable breaks and socket failures experienced by users of mobile devices such as smartphones and tablets have become a problem. In this study, wireless charging of mobile phones is provided with inductive coupling. The wireless power transfer (WPT) system has a diameter of 5 cm, operates at 10 MHz, and has an output power of 5 W. The coil design includes a ferrite core and shielding for reducing electromagnetic scattering. The paper used mathematical calculations and simulation tools, including MATLAB, Simulink, Maxwell 3D, and HFSS, to analyze the WPT design and its effects on human health at various conditions. As a result, the magnetic exposure was kept below the limit value in this WPT design, thus protecting the person and the device. In addition, the WPT design achieved high efficiency with a maximum air gap of 2 cm when aligned, and up to 2 cm misalignment at 0.5 cm air gap. [ABSTRACT FROM AUTHOR]

This paper presents a slow‐wave substrate integrated suspended parallel strip line (SW‐SISPSL) for the first time. The slow‐wave effect is produced by cascading high/low‐impedance SISPSL in the meander line configuration. Different from conventional single‐ended slow‐wave transmission lines, the proposed SW‐SISPSL supports differential signal transmission. The characteristic impedance and slow‐wave factor of the SW‐SISPSL are analyzed using equivalent circuit models. Using the proposed SW‐SISPSL and a SISPSL phase inverter, a very compact rat‐race coupler is implemented. The core circuit area of the slow‐wave rat‐race coupler is 0.083 λg × 0.089 λg, which is only 4.12% of the conventional topology. [ABSTRACT FROM AUTHOR]

An angle sensitive transmission metasurface unit structure is designed in this paper. The metasurface unit presents a good transmission performance for the TE wave incidence, and has a linear phase response with the maximum phase difference up to 180° when the incidence angle changes in the range of −45° and +45°. Moreover, a reconfigurable design of the metasurface unit is realized by loading a varator, and the phase difference is extended to 270° to satisfy the demand of multibit metasurface. Based on the characteristics of angle sensitivity and reconfigurability of the metasurface unit, combined with the control of the varactor and the unit tilt angle, a new 1‐bit digital coding angle sensitive metasurface is proposed. The metasurface has a specification of 20 × 20 and a center frequency of 10 GHz. Both the simulation and measurement show that different transmission is realized for incident waves at different incident angles. It can form different beams, which can be used for multibeam modulation with the same frequency and same polarization. [ABSTRACT FROM AUTHOR]

This paper demonstrates an analytical study of different nonplanar frequency selective surfaces (FSSs) for X‐band (8–12 GHz) electromagnetic (EM) shielding applications. A well‐known metallic square loop unit cell is used for the analysis, which is arranged in a periodic pattern on a three‐dimensional (3‐D) printer compatible dielectric substrate. The geometry is wrapped on various kinds of curved surfaces (cylindrical, paraboloid, and hemispherical surfaces) and investigated using the finite element boundary integral (FEBI) technique. The structure exhibits a band stop characteristic with a fractional bandwidth of 62.74% (6.68–12.66 GHz, having transmission coefficient below −10 dB), resonating around 9.53 GHz under different angles of incident EM wave. Finally, the 3‐D printing method is used to fabricate the prototypes for performing laboratory measurements. The simulated and measured results follow each other closely, thereby establishing the proposed technique in realizing nonplanar FSSs. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a dual‐band complementary frequency selective surface (CFSS) with narrow stop band and large stop band. The proposed CFSS combines two simple geometries, the square loop with grid and the crossed dipole. The resonant frequencies are 2.53 and 5.38 GHz. The bandwidths of 280 MHz and 1.77 GHz were obtained, at –10 dB level, for the first and second bands, respectively. These frequencies and bands show that the structure can be applied in Wi‐Fi (2.4–2.5 GHz) and C‐band (4–6 GHz) frequencies. The simulated and measured results show that the chosen geometry has angular stability and polarization independence up to 45°. We can observe a good agreement between simulated and measured results. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to measure physically small antennas using a coaxial cone transverse electromagnetic wave (TEM) cell. Due to the ultra‐wideband, large electric field strength, and high dynamic range characteristics, coaxial cone provides a reliable environment to measure parameters such as gain and antenna factor of small antennas. The frequency could cover 200 MHz–40 GHz. To investigate the suitability of the coaxial cone TEM cell to measure antenna, measurements for a wideband small antenna and a horn antenna are carried out. And the validity of this method is verified through comparison of the obtained results, the measurement uncertainty is evaluated. Compared to an anechoic chamber, the space, cost, and time requirements are reduced drastically. Accordingly, this method could be a more effective alternative way to conventional methods such as the three antennas method and the two antennas method using anechoic chambers. [ABSTRACT FROM AUTHOR]

This paper presents a pure water antenna with frequency reconfigurability, which is composed of a water resonator, L‐shaped feeder, and metal ground pad. An L‐shaped feeding structure is designed so that the working frequency can be adjusted by changing the water level of the resonator. The cross‐stack periodic water radiator structure improves the radiation efficiency by 2–4 dB compared with simple rectangular structure. The working frequency of this antenna is around 1 GHz, and will decrease by 17 MHz for every 5 mm increase in water level, which proves the feasibility of this antenna for water level monitoring. It has the potential for application in the field of wireless environmental monitoring for the Internet of Things. [ABSTRACT FROM AUTHOR]

Periodically patterned conductor surfaces can transmit electromagnetic modes similar to surface plasmon polaritons, which are called spoof surface plasmon polaritons (SSPPs). In this paper, noncoplanar dentate complementary structure units are proposed. In this case, the fundamental SSPP is split into two modes, of which the mode in the high‐frequency side exhibits negative group velocity (NGV) near the cutoff frequency. The dispersion characteristics of NGV modes can be controlled by manipulating the symmetry of the complementary structure. It is confirmed that the actual transmission wave in the SSPP waveguide is the superposition result of the two split‐mode wave components. [ABSTRACT FROM AUTHOR]

In this research paper, a polyester‐based bandpass microstrip filer is proposed. Split ring resonator, stepped‐impedance resonator structure, and coupled microstrip lines are used to design the proposed filter circuit in the pass band of 4.35 to 4.60 GHz for NATO frequency band military applications. The filter is fabricated using polyester substrate and self‐adhesive copper tape. The Agilent vector network analyzer is used to test the fabricated polyester wearable filter. There is good agreement between the simulated as well as measured insertion loss and return loss of the proposed wearable filter. [ABSTRACT FROM AUTHOR]

In this paper, a multimode terahertz absorber is implemented using an ultrathin silicon ring with varying multimodal resonance. The rectangular silicon ring is providing three resonances with creating electromagnetic dipoles. The altering of these resonances is explicitly controlled with the help of a circular graphene ring. The graphene ring is used in the centre for tenability and to achieve perfect absorption. An equivalent circuit model is also presented and verified for the proposed structure. The design is intended to measure the glucose percentage in water. In addition, this can be used as a biosensor for the detection of malaria parasite percentage in water. A few important parameters like sensitivity and quality factors are considered to evaluate the performance of the said design. The sensitivity with analyte thickness is found to be 0.445 THz TU−1, 0.4255 THz TU−1, and 0.4305 THz TU−1. The corresponding quality factor is noted for the lower, middle, and upper bands as 235, 653, and 264 respectively. Further, the sensitivity and quality factors were measured just by changing the refractive index. The new estimated values are 0.480 THz RIU−1, 0.403 THz RIU−1, and 0.562 THz RIU−1 and corresponding quality factors are 203, 555, and 261 for lower, middle, and upper bands respectively. The design is also expected to flourish as a polarization‐insensitive absorber. [ABSTRACT FROM AUTHOR]

A multilayer, ultra‐wideband absorber is proposed in this paper, which consists of a hybrid circuit analog absorber and a metal resonant absorber. The circuit analog absorber is located at the upper part of the absorber to absorb low‐frequency electromagnetic waves, and the metal resonant absorber is located at the bottom of the absorber to absorb high‐frequency electromagnetic waves and provide a reflecting plate for the absorber. Through simulation, the absorption rate of the designed absorber can be greater than 90% in the range of 2.33–18.43 GHz, and an equivalent circuit is established for verification. In addition, the absorber has good angular stability and polarization insensitivity. The prototype of the absorber was manufactured and measured, and the test results are basically consistent with the analysis results. [ABSTRACT FROM AUTHOR]