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A Dual-band Half Mode Substrate Integrated Waveguide (HMSIW) filter at 4.88 and 6.42 GHz are shown. Defective Microstrip Structure converts the HMSIW’s high-pass response to bandpass. Circular Complementary Split Ring Resonator splits the wide passband to give the filter dual characteristics. The out-of-band properties are improved by using a DS-OCSRR-shaped Defected Ground Structure (DGS). PCB technology is used to build and test the filter using an RT Duroid 5880 substrate with 1.6 mm thickness. The measured and simulated values match. Good skirt selectivity, insertion loss of 1.5/1.42 dB, fractional bandwidths of 9.42% and 6.7%, and return loss profile of 21 dB in both passbands characterize the dual-band filter. The filter is small, measuring 0.86λg × 0.37λg at 4.88 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a proposed design features a single-fed broadband circularly polarized antenna based on a rotating metasurface. The antenna is positioned between a rotating 4 × 4 periodic patch and the ground plane. The antenna comprises a driving patch and a parasitic patch. It utilizes two modes of the driving patch, which exhibit different polarizations along the two directions. When the metasurface is placed on it, the truncation angle of the metasurface cells causes the excitation of the two modes with left-rotating circular polarization (CP) and right-rotating CP, respectively. To weaken the right-handed CP relative to the left-handed CP, effectively enhancing the latter, another angle is truncated on the metasurface cell, and the metasurface is rotated by an angle. The final antenna was fabricated and tested with an overall size of 32 × 32 × 3 mm³. Measurements indicate that the |S11| < −10 dB bandwidth ranges from 4.72 to 7.67 GHz (47.9%), and the 3 dB axial ratio (AR) bandwidth ranges from 4.97 to 6.48 GHz (26.3%). Additionally, it achieves a peak gain of 7.75 dBi. [ABSTRACT FROM AUTHOR]

This paper presents a tunable center frequency and small size cavity bandpass filter design method. In this method, a capacitor-loaded open terminal coaxial resonator is employed to reduce the size of cavity filters. The resonator is designed and fabricated separately into two parts to achieve the flexible operating frequency purpose. The first part is called the base of the resonator which is simply a pillar and directly fabricated integrally with the cavity housing. The second part called the hat of the resonator is the main part causing the load capacitance in cavity filters. By using different heights of the base part or/and different shapes and sizes of the hat, the operating frequency of cavity filters can be changed flexibly. This method not only reduces the difficulty and cost of cavity filter processing but also makes cavity filters reconfigurable. To demonstrate the effectiveness of the method, a cavity filter sample with a center frequency of 3.45 GHz and a bandwidth of 80 MHz was designed, fabricated, and measured. The measured results show that the insertion loss was smaller than 1.33 dB in the whole bandwidth, one zero-point at 3.350 GHz reaching -68 dB, the rejection at 3.550 GHz was -41 dB, unloaded Q was 5,898, and the dimension of the filter was 128 mm×86 mm×23 mm. [ABSTRACT FROM AUTHOR]

This paper describes a 2-stage tactic for achieving an odd-order variable-bandwidth (OO-VBW) filter with absolutely guaranteed stability. The design methodology aims to minimize the p-norm amplitude-response error while maintaining the OO-VBW-filter's stability. In order to tune OO-VBW filter's amplitude response, we utilize a kind of functions of the bandwidth (BW)-tuning parameter to express the filter's coefficients. Because those functions have changeable function values, the designed OO-VBW-filter's amplitude response possesses variability. Another important concern in this paper is the stability issue. When the filter coefficient values expressed as function values are changed, the OO-VBW filter that has feedback structures may become unstable. This necessitates that the OO-VBW-filter's stability must always be preserved during real-time tuning. In order to stabilize such an OO-VBW filter that has feedback structures, a coefficient-conversion (CC) algorithm is adopted, and it is incorporated into the 2-stage methodology for obtaining the OO-VBW filter. To illustrate both the stability and high approximation accuracy, the design of an OO-VBW bandpass filter is simulated. The simulation details verify that both stability and high accuracy can be successfully achieved. [ABSTRACT FROM AUTHOR]

Polarization‐division multiplexing is crucial for increasing channel capacity and spectral efficiency in communications. A key component is the polarization multiplexer, which combines or separates signals with orthogonal polarizations. Existing planar multiplexers lack an ultrawide band for terahertz communications. While microwave‐inspired orthomode transducers (OMTs) provide broadband operation, they suffer from high ohmic loss and bulkiness at terahertz frequencies. Optical integrated polarization beam splitters (PBSs) offer low loss and good integrability but have narrow bandwidths. This work presents a substrateless all‐silicon polarization multiplexer based on tapered directional couplers and air‐silicon effective mediums, integrated monolithically on a compact footprint. The device demonstrates a 37.8% fractional bandwidth, an average insertion loss of ≈$\approx$1 dB, and a polarization extinction ratio above 20 dB over 225–330 GHz. This superior performance is enabled by the anisotropy of the effective medium claddings, affecting the two orthogonal guided modes differently. The multiplexer enables simultaneous two‐channel terahertz fiber communications with polarization diversity.   It supports aggregated data rates up to 155 and 190 Gbit s−1${\rm s}^{-1}$ with bit error rates below hard‐ and soft‐decision forward‐error‐correction limits, respectively. This advancement holds promise for 6G terahertz integrated systems with enhanced channel capacities. [ABSTRACT FROM AUTHOR]

In this paper, a metamaterial inspired meandered line loaded antenna with dual-band characteristics for wireless applications is presented. Initially, the antenna is loaded with a single meandered line structure and operates over a single band with a center frequency of 5.64 GHz and circularly polarized (CP) radiation. Further, it is loaded with two more similar meandered line structures inducing an extra band with a center frequency of 3.4 GHz and hence operating as a dual band antenna with an impedance bandwidth of 11.4% and 33.7%, respectively, exhibiting CP radiation in its second band. Moreover, the antenna is backed with a metasurface (MS) at the ground side with a separation of 18.4 mm to enhance the gain and radiation of the antenna. The antenna exhibits good radiation characteristics with peak gains of 7.66 dBi and 8.7 dBi in the first and second bands, respectively. The antenna is fabricated, and promising experimental results have been observed. [ABSTRACT FROM AUTHOR]

In this paper, a wideband low profile dual-polarization antenna is proposed based on the in-phase reflection characteristic of artificial magnetic conductor (AMC). The AMC cells are designed as two concentric square metallic rings connected by a ‘*’ shaped metallic strip. Its in-phase reflection bandwidth is 2.12 GHz–3.31 GHz, and input-match bandwidth is 1.56 GHz–2.43 GHz. The relative bandwidth is 43.83% and 43.61%, respectively. In addition, the AMC cells are loaded on the reflector of the proposed dual polarized dipole antenna. The measured results show that the −10 dB reflection coefficient (|S11|) bandwidth of the antenna is 1.55 GHz to 2.4 GHz (43%), and the height is only 0.136λ0. Furthermore, the gain and front-to- back ratio of the antenna are increased by about 0.8 and 4 dB respectively due to the action of AMC. [ABSTRACT FROM AUTHOR]

Absorption bandwidth is one of the key performance metrics for electromagnetic wave (EMW) absorbers. Traditional oxide absorbers, despite their merits such as abundance, long‐term stability, and low cost, have long been plagued by their inferior absorption bandwidth (typically less than 4 GHz). Herein, a novel concept is proposed: the introduction of cation vacancies and heterostructures into oxides can remarkably broaden their absorption bandwidth. A broadening value of 7.75 GHz is observed through this route, surpassing the broadening achieved by other existing engineering methods, by ≈100%. Crucially, this study discovers that a negative shift in the d‐band center, a previously overlooked factor, is responsible for this broadening phenomenon. By inducing cation vacancies and heterostructures, a negative shift in the d‐band center gives rise to an increase in carrier concentration and promotion of charge separation, resulting in higher conductive and polarization losses, ultimately leading to a broader absorption bandwidth. The applicability of this concept is validated in another distinctly different system, where the absorption bandwidth also experiences a remarkable increase (from 0 to 6.86 GHz). This study offers significant implications for designing wide bandwidth EMW absorbers and expands their applications in various scenarios such as wearable electronics and artificial intelligent devices. [ABSTRACT FROM AUTHOR]

Thin‐film lithium niobate (TFLN)‐based electro‐optic modulators have extensive applications in broadband optical communications due to their broad bandwidth, high extinction ratio, and low optical loss. However, compared with their silicon and indium‐phosphide (InP)‐based counterparts, TFLN exhibits lower modulation efficiency. Simultaneously achieving low driving voltage and a wide modulating bandwidth poses a significant challenge. To address this limitation, this paper proposes a transparent conductive oxide film into the device, resulting in an ultra‐high modulation efficiency of 1.02 V cm. The fabricated composite electrode not only attains high modulation efficiency but also sustains a high electro‐optic bandwidth, as evidenced by the 3 dB roll‐off at 108 GHz and the transmission of PAM‐4 signals at 224 Gbit s−1. The fabricated device offers novel solutions for low‐cost, high‐performance modulators, thereby facilitating the downsizing of TFLN‐based multichannel optical transmitter chips. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach is introduced for the development of a power-efficient voltage differencing buffered amplifier (VDBA) by incorporating an adaptive biasing circuit. The proposed design is specifically tailored to exhibit low power consumption. The VDBA proposed in this study includes a conventional transconductance unit (TU) with an adaptive biasing and a positive feedback circuit. Incorporating adaptive bias cells and cross-coupled positive feedback circuit, the VDBA structure allows for boosted tunable gain based on the input differential voltage. The proposed VDBA shows improved transconductance gain, transient characteristics, linearity for a wide range of inputs, and reduced standby power dissipation. A mathematical formulation has been presented to define the characteristics of the proposed VDBA. To validate the proposed VDBA structure, SPICE simulations were conducted using 180 nm CMOS technology. The input linear range of the proposed VDBA is ± 250 mV. The 3 dB bandwidth of the proposed structure is 200 MHz. The THD has been found low. The Monte Carlo simulations have also been carried out and found the proposed structure is less sensitive to the different parameter variations. The slew rate of the proposed VDBA is found 26.2 V/µS. As an application example, a voltage mode universal MISO biquad filter is also proposed using the proposed structure VDBA. [ABSTRACT FROM AUTHOR]

Multi‐functional metasurfaces have shown great promise in tackling complex electromagnetic issues. Reconfigurable frequency‐selective Rasorbers (FSRs) have recently received growing attraction, but existing designs are constrained in their switchable modes, typically limited to FSR/Absorber or FSR/frequency‐selective surface (FSS). To address this limitation, a new metasurface that integrates four different functioning modes, including FSR, FSS, Absorber, and Reflector is proposed, which can be dynamically switched as demanded. The design is based on the theoretical network model analysis, and its intriguing performances are verified through simulations and experiments both in frequency and time domains. The results show that the FSR and Absorber modes exhibit wide low‐scattering bandwidths with narrow transmission windows that can be turned on or off. These two modes also eliminate the sputtering effect, making it suitable for stealth applications. In contrast, the Reflector mode is efficient in blocking microwaves across a broad spectrum, and a transmission window can be opened in the FSS mode. It is believed this multi‐functional metasurface can serve as a radome to protect against various challenges such as detection, interference, and high‐power invasion. [ABSTRACT FROM AUTHOR]

The increasing heterogeneity of traffic in the Internet of Things (IoT) service demands presents a challenge for computing nodes to meet the computing resources and link bandwidth required. To address this, IoT requests have been virtualized and organized in service function chaining (SFC), which requires a host among hybrid cloud‐fog computing nodes. To find a suitable host for each service function (SF) request, a typical migration algorithm has been used. However, this approach delayed the response due to propagation delays in searching for a valid nearby node. Mission‐critical service demands may not even be served at all. This article addresses this issue by proposing two novel approaches: nearest candidate node selection (NCNS) and fastest candidate node selection (FCNS). These approaches employ software‐defined network (SDN) controllers and the Markovian arrival process, Markovian service process, and single host (M/M/1) queuing model to monitor the maximum possible latency required to meet the SF service demand by each computing node and finally assigning into one with least latency. With the use of these methods, heuristic monitoring of computing resources is made possible, allowing the selection of the most suitable host computing nodes based on proximity or minimal round‐trip time. Moreover, priority‐based fastest candidate node selection (PB‐FCNS), an adaptation of FCNS, accounts for concurrent service requests using the general arrival process, general service process, and single host node (G/G/1) queuing model. Compared to traditional migration algorithms, NCNS and FCNS provide significant improvements in reducing round‐trip time by 5% and decreasing the probability of unsuccessful service function chains by 55%. Despite the cost of installation, employing these methods in conjunction with SDN controllers can reduce latency, maximize service success rates, and guarantee the delivery of heterogeneous service functions. [ABSTRACT FROM AUTHOR]

In this paper, a low‐profile, high‐gain filtering antenna is proposed and developed for n‐77 (3300–4200 MHz) and n‐78 band (3300−3800 MHz) applications. The suggested filtering antenna is derived from a circular patch antenna. To efficiently reduce the harmonics, in the lower and upper stopbands, a pair of sectoral arcs and rectangular slots is etched out from the driven circular patch. Furthermore, the resultant structure is surrounded by a ring split at three different locations. Simulation studies reveal that this ring with three sectors is coupled with a driven patch and is highly responsible for extending the impedance bandwidth in the passband. This coupling also contributes to an extranull in the upper stopband region. In order to validate the simulated results, a prototype is fabricated, tested, and found that the measured results are consistent with the simulated one. The suggested filtering antenna, with a low profile of 0.0194λ0, demonstrates a wide fractional bandwidth of 10.2% ranging from 3.52 to 3.90 GHz, centred at 3.7 GHz. The maximum peak gain of 7.68 dB is achieved within the passband. Three configurable radiation nulls, first at 3.36 GHz, near the lower band edge; second at 4.04 GHz; and third at 4.24 GHz, near the upper band‐edge frequencies, are generated to achieve fine out‐of‐band suppression levels. [ABSTRACT FROM AUTHOR]

In broadband terahertz waves generated by femtosecond lasers, spatial chirp will be simultaneously produced with the introduction of angular dispersion. The chirp characteristics of the terahertz wave will directly affect the frequency response, bandwidth response, and intensity response of the terahertz sensor. To enhance the capability of terahertz sensors, it is necessary to control and improve the chirped characteristics of broadband terahertz sources. We generate a chirped terahertz wave via optical rectification in a LiNbO3 prism using the technique of pulse front tilt. The effect of the pump-beam spot size on THz generation is systematically studied. The pump's spot size is manipulated using a telescope system. With a pump spot diameter of 1.8 mm, the scanning spectrum of the THz pulse is narrower and is divided into multiple distinct peaks. In contrast, using a pump spot diameter of 3.7 mm leads to increased efficiency in the generation of THz pulses. Also, we investigate the underlying properties governing the generation of chirped terahertz pulses using varying pump pulse spot diameters. [ABSTRACT FROM AUTHOR]

Array waveguide gratings (AWGs) have been widely used in multi-purpose and multi-functional integrated photonic devices for Microwave photonics (MWP) systems. In this paper, we compare the effect of output waveguide configurations on the performance of AWGs. The AWG with an output waveguide converging on the grating circle had larger crosstalk and lower nonuniformity. We also fabricated a 1 × 8 AWG with an output waveguide converging onto the SOI's grating circle, whose central operation wavelength was around 1550 nm. The fabricated AWG has a chip size of 500 μm × 450 μm. Experimental results show that the adjacent channel crosstalk is −12.68 dB. The center channel insertion loss, as well as 3 dB bandwidth, are 4.18 dB and 1.22 nm at 1550 nm, respectively. The nonuniformity is about 0.494 dB, and the free spectral range is 19.4 nm. The proposed AWG is expected to play an important role in future MWP systems given its good nonuniformity and insertion loss level. [ABSTRACT FROM AUTHOR]

This paper explores the potential of an Integrated Sensing and Communication (ISAC) system to enhance search-and-rescue operations. While prior research has explored ISAC capabilities in Unmanned Aerial Vehicles (UAVs), our study focuses on addressing the specific challenges posed by modern communication standards (e.g., power, frequency, and bandwidth limitations) in the context of search-and-rescue missions. The paper details effective methods for processing echoed signals generated by downlink transmissions and evaluates key performance indicators, including Noise Equivalent Sigma Zero (NESZ) and channel capacity. Additionally, we utilize synchronization uplink signals transmitted by User Equipment (UE) to improve target detection and classification of possible victims by fusing SAR imagery with triangulation results from uplink signals. An experimental campaign validates the proposed setup by integrating SAR images of the environment with active localization results, both produced by a UAV equipped with a Software Defined Radio (SDR) payload. Our results demonstrate the system's capability to detect and localize buried targets in avalanche scenarios, with localization errors ranging from centimeters to 10 m depending on environmental conditions. This successful integration highlights the practical applicability of our approach in challenging search-and-rescue missions. [ABSTRACT FROM AUTHOR]

In order to implement the fifth generation (5G) communication system for a large number of users, the governments of many countries nominated the low 5G frequency band between 3.3 and 4.3 GHz. This paper proposes a wideband RFPA by designing the input matching network (MN) and output MN of the device using the simplified real frequency technique (SRFT) and the harmonic tuning network. The load-pull and source-pull is applied at multiple points for 100 MHz intervals over the bandwidth to obtain the optimum impedances at the output and input of the 10W Gallium Nitride (GaN) Cree CGH40010F device. To verify the design, the RFPA is simulated, and the performance is measured between 3.3 and 4.3 GHz. According to experimental findings, the measured drain efficiency (DE) throughout the whole bandwidth ranged from 57.5 to 67.5% at the output power of 40 dBm. Moreover, at the 1 dB compression point between 39.2 and 42.2 dBm output power, the drain efficiency (DE) achieves a high value of 81.2% with an output power of 42.2 dBm at a frequency of 3.3 GHz. The RFPA can obtain a maximum gain of 12.4 dB at 3.5 GHz. The linearity of the RFPA with a two-tone signal is measured and the value is less than -22 dBc all over the band. [ABSTRACT FROM AUTHOR]

In this article, a systematic theory and design approach are presented to achieve bandwidth expansion of the Doherty power amplifier (DPA) by using extended continuous Class‐GF (ECCGF) power amplifiers (PAs) as carrier PAs. The results of the theoretical analysis indicate that compared to conventional DPA, introducing ECCGF PA as carrier PA into the DPA design can establish two larger target impedance spaces with overlapping regions for saturation and output back‐off (OBO) power levels, which can reduce the design complexity of impedance inverter networks (IINs) while achieving DPA bandwidth expansion. Based on this, the proposed design theory is validated in the design and fabrication of a prototype DPA employing the CGH40010F GaN HEMT provided by MACOM. The measured results show that under continuous wave excitation, the designed DPA delivers a saturated output power of 43.1–44.2 dBm in the range of 1.3–2.7 GHz with a relative bandwidth of 70%. The drain efficiencies of 61.2%–73.2% and 42.5%–52.7% are achieved over the entire band at the saturation and 6‐dB OBO power levels, respectively. The measured results also confirmed the theoretical findings. [ABSTRACT FROM AUTHOR]

Optical frequency combs with equidistant frequency modes have revolutionized metrology and spectroscopy. The most widespread combs consist of periodic pulse trains generated by mode-locked lasers. However, it has recently been demonstrated that most semiconductor lasers based on Fabry–Pérot cavities, such as quantum well laser diodes, quantum cascade lasers, and quantum dot lasers, can enter an unconventional regime without traditional mode-locking mechanisms. The time-domain profile of these self-locked combs features a frequency-modulated (FM) wave with quasi-continuous-wave intensity and near-linear frequency chirp. The observation of the FM mode of operation in lasers with significantly different dynamics suggested that this mode is a fundamental operating state of semiconductor lasers, stemming from a deeper underlying mechanism. Thanks to recent theoretical and experimental advances, the origin of FM behavior has become clear. In this Perspective, we discuss the current status of FM combs in semiconductor lasers based on Fabry–Pérot cavities, focusing on their physical origin, modeling, characterization, bandwidth enhancement, and potential in future applications. [ABSTRACT FROM AUTHOR]

This paper introduces a hybrid inductor‐current sensor with fast response and high accuracy using online calibration for 25 MHz BUCK DC‐DC converter. The proposed inductor‐current sensor combines the high accuracy of the senseFET sensing method with the lossless and real‐time response characteristics of the RC filter technique. Comparing to exist techniques, the proposed calibration scheme can make filter coefficient converge even in unsteady state, which improve its effectiveness in practical application. Moreover, the proposed inductor‐current sensor utilizes sample‐based senseFET‐based current sensing to offer calibration reference, which avoid the use of high bandwidth amplifier. Digital current balance control is seamlessly integrated into the 25 MHz 2‐phase digital adaptive time‐controlled (AOT) BUCK DC‐DC converter through the utilization of the proposed hybrid inductor‐current sensor. The 2‐phase BUCK DC‐DC converter is implemented in a standard 0.18‐µm CMOS process. After online calibration, proposed hybrid inductor‐current sensor outputs a full‐wave waveform with high accuracy and low propagation delay of only 9 ns in post‐layout simulation. [ABSTRACT FROM AUTHOR]

Two concentric double-loop antennas were analyzed using the moment method to increase the 3 dB axial ratio bandwidth. Each antenna has a driven loop connected to a branched feedline that is vertical to the ground plane. First, a parasitic loop was added outside of the driven one with a spacing of S. It was found that the axial ratio bandwidth has a maximum value of 23% for S = 0.02 wavelengths. Next, we moved a parasitic loop inside of the driven one. It was revealed that the antenna shows an axial ratio bandwidth of 40%, which is three times as wide as that of a single-loop antenna. The analysis results were verified with experimental work. [ABSTRACT FROM AUTHOR]

A low-profile multi-port dual-band antenna with pattern and polarization diversity is presented for 2.45 and 5.8 GHz bands. The antenna consists of a monopolar patch for vertically polarized (VP) omnidirectional radiation and four combining printed-dipole and tapered-slot elements arranged in a circular shape for horizontally polarized (HP) multibeam radiation, and consequently, both pattern and polarization diversities are achieved in the full azimuth plane. The monopolar patch employs four vias and a square-ring slot to excite T M 01 and T M 02 modes at 2.45 and 5.8 GHz, respectively. Each HP element utilizes printed-dipole and tapered-slot modes for the lower and upper bands, respectively. The VP and HP elements are collocated with a common ground plane, which not only allows a low profile but also broadens the lower band of the monopolar mode. The final design with 0.03 λ 2.45 - G H z height yields a measured 10-dB return loss bandwidth of 8.6% and 6.7% at 2.45 and 5.8 GHz, respectively, and an isolation ≥ 20 dB among all the ports. Its pattern and polarization diversities are validated by far-field measurements. [ABSTRACT FROM AUTHOR]

A 360° video offers a more immersive experience, gaining increasing popularity among users. However, enhancing the transmission efficiency of 360° videos under limited bandwidth conditions remains a significant challenge. This paper segments the video into three areas: the attention area, the edge area, and the viewpoint-switching transition area. Based on the segmentation of these three distinct video areas, a novel non-uniform coding transmission method for 360° videos is presented, along with mathematical modeling to define the optimization problem. A heuristic algorithm is subsequently introduced, which adaptively determines the optimal number of tiles and allocates the bitrate for each tile in real time to enhance the user's quality of experience (QoE). Finally, a simulation platform has been developed to validate the efficacy of the proposed algorithm by conducting comparative analyses with existing algorithms. [ABSTRACT FROM AUTHOR]

A miniaturized metamaterial (MTM) bandpass filter (BPF) based on end-fire coaxial coupling is proposed. End-fire coaxial coupling is achieved by using the coaxial cavity to connect with the SubMiniature version A connector. The subwavelength characteristics of the MTM lead to the miniaturization advantages of the filter in transverse dimensions. Moreover, the longitudinal length of the coaxial cavity can be sharply reduced by introducing matched blocks. As a result, the proposed filter has miniaturization merit both in transverse and longitudinal dimensions. The full-wave simulation results further reveal that the MTM BPF exhibits the advantages of low loss, low reflection, and low group delay. Additionally, the fractional bandwidth is approximately 13% when |S11| is less than −15 dB. The MTM BPF might have potential applications to array antennas for easily being expanded to two dimensional arrays. [ABSTRACT FROM AUTHOR]

This paper presents a circularly polarized hybrid cylindrical dielectric resonator antenna (HCDRA) over a modified Minkowski unit-cell-based metasurface for 5G n79 band (4.4–5 GHz) and IEEE 802.11n WLAN (5 GHz) applications. The location of the perturbed probe feed mechanism and the asymmetric nature of the metasurface are the factors that influence the circularly polarized (CP) radiation within the DR element. The magnitude of E-field distribution and parametric study of the antenna to obtain the optimized feed location are the pieces of evidence of CP radiation. The return loss (RL) and axial ratio (AR) bandwidths produced by the proposed antenna are 1.837 GHz and 750 MHz with a peak gain of 7.04 dBic. The gain obtained is more than 5 dBic across the offered bandwidth of the proposed antenna. The proposed antenna is fabricated and tested in an anechoic chamber for measured results, and these results closely match with the simulation results. [ABSTRACT FROM AUTHOR]

We propose a novel miniaturized optical attenuator based on the evanescent-field coupling between two nanofibers. Benefiting from a wavelength-dependent waveguiding property of the coupled structure, a tunable attenuation with maximum extinction ratio of ~ 20 dB is demonstrated with an ultrawide optical bandwidth up to 0.7 μm in experiment. The wavelength-depended waveguiding properties of both one single nanofiber and coupled nanofibers are investigated in both theory and simulation. Using an adiabatic coupling structure, an attenuation range from − 0.16 dB to − 18.46 dB is obtained within a spectrum from 1.2 μm to 1.7 μm experimentally. Moreover, the simulated results indicate that, the attenuation only shows a slight change of ~ 0.1 dB with a lateral misalignment of 0.5 μm between the two nanofibers, indicating a high tolerance of this attenuator to the lateral misalignment. Considering the wide bandwidth as well as the ultracompact structure, this attenuator shows high potential in applications such as all-fiber optical sensing and communicating. [ABSTRACT FROM AUTHOR]

In this paper, a W‐band unequal power divider is proposed on the basis of groove‐to‐ridge gap waveguide, and it is employed to design a low sidelobe level (SLL) slot array antenna with monopulse radiation patterns. The proposed unequal power divider is capable of realizing large power ratio and small phase difference. In light of this property, three different unequal power dividers with various output power ratios and phase balance are proposed for designing a low SLL array antenna. Furthermore, a compare network with planar Magic‐Tee is designed for realizing the monopulse radiation patterns. Then, a 32 × 32 antenna array consisting of five unconnected layers is designed, fabricated, and measured. The measured results indicate that the relative impedance bandwidth of the antenna is about 5.5%. In addition, the realized gain of the sum pattern at 84 GHz is 35.4 dBi, while the null of the difference pattern is less than 38 dB. Furthermore, the SLL of the antenna array is more than −25 dB on both the E‐ and H‐planes within the operating band. [ABSTRACT FROM AUTHOR]

This paper focuses on the problem of testing the null hypothesis that the regression functions of several populations are equal under a general nonparametric homoscedastic regression model. It is well known that linear kernel regression estimators are sensitive to atypical responses. These distorted estimates will influence the test statistic constructed from them so the conclusions obtained when testing equality of several regression functions may also be affected. In recent years, the use of testing procedures based on empirical characteristic functions has shown good practical properties. For that reason, to provide more reliable inferences, we construct a test statistic that combines characteristic functions and residuals obtained from a robust smoother under the null hypothesis. The asymptotic distribution of the test statistic is studied under the null hypothesis and under root $ -n $ −n contiguous alternatives. A Monte Carlo study is performed to compare the finite sample behaviour of the proposed test with the classical one obtained using local averages. The reported numerical experiments show the advantage of the proposed methodology over the one based on Nadaraya–Watson estimators for finite samples. An illustration to a real data set is also provided and enables to investigate the sensitivity of the $ p- $ p−value to the bandwidth selection. [ABSTRACT FROM AUTHOR]

In the paper, a high‐selectivity wideband four‐way filtering power divider with input absorptive feature is presented. It consists of two parallel‐coupled lines (CLs), two three‐coupled lines (TCLs), two open‐ended stepped branches, one absorptive branch, and two isolation resistors. The wideband filtering response is achieved by cascading the TCLs and CLs. While high selectivity is obtained by loading the open‐ended stepped branch, where two extra transmission zeros are generated. In addition, wide absorptive bandwidth with good isolations between adjacent output ports are realized by combining the absorptive branch with the isolation resistors. Equations are derived by using the two‐parity mode analysis, and main parameters are investigated in detail. For validation, a prototype was designed and fabricated. Test results show that the 3‐dB FBW can reach 87% with a 10‐dB input absorptive FBW of 200%. Besides, for the output ports with 10‐dB return loss and 10‐dB isolation, the FBWs are 94% and 91.5%, respectively. It also features high frequency selectivity and low insertion loss. [ABSTRACT FROM AUTHOR]

Electro–optic phase modulators (PMs) are critical components for modern communication, sensing, and microwave photonics. A recycling PM has been demonstrated to effectively reduce the half‐wave voltage (Vπ) while exhibiting resonant behavior for the driven microwave signals [Nature 612, 252 (2022)]. However, the significant optical delay of the loop‐back waveguide reduces the low‐Vπ bandwidth to 1.5 GHz. Herein, a novel folded structure is proposed for recycling PM fabricated on a thin‐film lithium niobate (TFLN) platform. The low‐Vπ bandwidth can be expanded by significantly reducing the optical loop‐back delay. Additionally, efficient velocity matching can be achieved by aligning the time delay between the microwave and optical signals. The proposed folded recycling PM, with a 0.6 × 12 mm2 footprint, is characterized by the lowest Vπ of 2–3 V in each modulation period across 3.5 to 40 GHz and a doubled low‐Vπ bandwidth of 3 GHz. As an application demonstration, such a folded recycling PM is employed for tunable optical frequency combs (OFCs) generation. Flat OFCs consisting of 15, 21, and 13 comb lines are generated with flexible comb spacings of 29.6, 31.3, and 33 GHz, respectively. The proposed novel modulator can find distinct applications in communication, sensing, and microwave photonics. [ABSTRACT FROM AUTHOR]

Background: In this paper, we estimate the long-lasting influence of the former Habsburg Empire's border on the territory of Romania, specifically on the prevalence of corrupt behaviour and practices in health services. Methods: Employing microdata from the 2016 Life in Transition Survey and applying ordered probit regression, we explore the hypothesis that the geographical proximity of respondents' residences to the former imperial border—restricting the analysis within a bandwidth of 50 km, 75 km or even 100 km on either side – significantly influences current individual tendencies towards corrupt behaviour. Results: The results indicate that individuals in Transylvania living in the immediate vicinity of the former border of the Habsburg Empire (no more than 75 km away) show a higher propensity towards corrupt behaviours, similar to those from Moldova and Wallachia who reside in the same bandwidth but to the east of the former historical border. Interestingly, on one hand, after a series of tests with various relevant factors, the contagion effect is observed from right to left, meaning from those in Moldova and Wallachia towards those in Transylvania, and not the other way around as might be expected based on other previous studies. On the other hand, individuals living more than 75 kms west of the former historical border show clear reluctance to engage in informal payments and gift-giving when interacting with the public health system as patients. Conclusion: By rigorously controlling for various variables that comprehensively show different legacies of the communist regime, our results confirm the persistence of these influences across different bandwidths, thereby corroborating the hypothesis of path dependence influenced by the former Habsburg Empire. [ABSTRACT FROM AUTHOR]

With the exponential growth in data density and user ends of wireless networks, fronthaul is tasked with supporting aggregate bandwidths exceeding thousands of gigahertz while accommodating high-order modulation formats. However, it must address the bandwidth and noise limitations imposed by optical links and devices in a cost-efficient manner. Here we demonstrate a high-fidelity fronthaul system enabled by self-homodyne digital-analog radio-over-fiber superchannels, using a broadband electro-optic comb and uncoupled multicore fiber. This self-homodyne superchannel architecture not only offers capacity boosting but also supports carrier-recovery-free reception. Our approach achieves a record-breaking 15,000 GHz aggregated wireless bandwidth, corresponding to a 0.879 Pb/s common public radio interface (CPRI) equivalent data rate. Higher-order formats up to 1,048,576 quadrature-amplitude-modulated (QAM) are showcased at a 100 Tb/s class data rate. Furthermore, we employ a packaged on-chip electro-optic comb as the sole optical source to reduce the cost, supporting a data rate of 100.5 Tb/s with the 1024-QAM format. These demonstrations propel fronthaul into the era of Pb/s-level capacity and exhibit the promising potential of integrated-photonics implementation, pushing the boundaries to new heights in terms of capacity, fidelity, and cost. Here the authors propose a self-homodyne fronthaul architecture, utilizing DA-RoF super channels and multicore fiber, paving the way for the Pb/s era in fronthaul transmission, enabling ultra-highspeed Internet access. The remarkable data speeds reaching 0.879 Pb/s and the 256-QAM format make it possible for 150,000 5G channels to be accessed simultaneously. [ABSTRACT FROM AUTHOR]

Adiabatic quantum algorithm always requires that the system is kept in its ground state during the time evolution, but the interaction between the system and its environment often destroys the adiabaticity. In this paper we show that the reservoir engineering, i.e. the squeezing of the environment, can be used to enhance the adiabaticity of the system in the presence of environment noise. We use the non-Markovian quantum state diffusion (QSD) method to solve the system dynamics. Taking the Max-Cut problem as an example, the effects of squeezing strength and squeezing direction on the adiabatic fidelity are investigated. The results show that appropriate squeezing can enhance the fidelity, and this enhancement remains effective as system sizes vary. Moreover, the optimal squeezing direction changes with different temperature and spectrum bandwidth. Our work demonstrate that reservoir engineering is an effective approach to control the dynamics of the system, which can be used to boost the adiabaticity of the quantum algorithm in open systems. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multi-band textile monopole antenna for patient tracking applications. The designed antenna has compact footprints (0.13λ02) and works in the narrow band-internet of things (NB-IoT) 1.8 GHz, radio frequency identification (RFID), and industrial, scientific, and medical (ISM) 2.45 GHz and 5.8 GHz bands. The impedance bandwidths and gain of the antenna at 1.8 GHz, 2.45 GHz, and 5.8 GHz are 310 MHz, 960 MHz, and 1140 MHz; 3.7 dBi, 5.3 dBi, and 9.6 dBi, respectively. Also, the antenna's behavior is checked on different body parts of the human body in various bending scenarios. As per the evaluated link budget, the designed antenna can easily communicate up to 100 m of distance. The specific absorption rate values of the designed antenna are also within acceptable limits as per the (FCC/ICNIRP) standards at the reported frequency bands. Unlike traditional rigid antennas, the proposed textile antenna is non-intrusive, enhancing user safety and comfort. The denim material makes it comfortable for extended wear, reducing the risk of skin irritation. It can also withstand regular wear and tear, including stretching and bending. The presented denim-based antenna can be seamlessly integrated into clothing and accessories, making it less obtrusive and more aesthetically pleasing. [ABSTRACT FROM AUTHOR]

Advancements in assisted driving technologies are expected to enable future passengers to use a wide range of multimedia applications in electric vehicles (EVs). To address the bandwidth demands for high-resolution and immersive videos during peak traffic, this study introduces a bandwidth-management algorithm to support differentiated streaming services in heterogeneous vehicle-to-everything (V2X) networks. By leveraging cellular 6G base stations, along with Cell-Free (CF) Massive Multi-Input Multi-Output (mMIMO) Wi-Fi 7 access points, the algorithm aims to provide a high-coverage, high-speed, and low-interference V2X network environment. Additionally, Li-Fi technology is employed to supply extra bandwidth to vehicles with limited connectivity via V2V communication. Importantly, the study addresses the urgency and prioritization of different applications to ensure the smooth execution of emergency applications and introduces a pre-downloading mechanism specifically for non-real-time applications. Through simulations, the algorithm's effectiveness in meeting EV users' bandwidth needs for various multimedia streaming applications is demonstrated. During peak-bandwidth-demand periods, users experienced an average increase in bandwidth of 47%. Furthermore, bandwidth utilization across the V2X landscape is significantly improved. [ABSTRACT FROM AUTHOR]

This study proposes a pattern–diversity antenna with different radiation patterns at two different frequency bands (f1 and f2; f1: broadside radiation pattern, f2: conical radiation pattern). The proposed structure consists of a central circular antenna and two annular ring antennas, with each of the antennas having individual ports. Two of the ports (port 1 and port 3) exhibit orthogonal broadside radiation patterns at low bands, and the other two ports (port 1 and port 2) exhibit orthogonal conical radiation patterns at high bands. Thus, they have polarization diversity characteristics. To improve isolation between the ports, the inner part of the annular ring antennas is shorted by an array, and the outermost port is positioned orthogonal to the other ports. Using this configuration, the isolation values between the ports are −26.7 and −30.1 dB at the two frequency bands, respectively. Using the fabricated prototype, experimental results show that the proposed antenna achieves −10 dB bandwidths of 240 MHz (5.71–5.95 GHz) and 210 MHz (7.69–7.9 GHz) at f1 and f2, respectively. [ABSTRACT FROM AUTHOR]

A lightning current measurement method using a Rogowski coil based on an integral circuit with low-frequency attenuation feedback was proposed to address the issue of low-frequency distortion in the measurement of lightning currents on transmission lines using Rogowski coils. Firstly, the causes of low-frequency distortion in lightning current measurements using Rogowski coils were analyzed from the perspective of frequency domains. On this basis, an integration correction optimization circuit with a low-frequency attenuation feedback network was designed to correct the low-frequency distortion. The optimized integration circuit can also reduce the impact of low-frequency noise and the DC bias of the operational amplifier (op-amp) on the integration circuit due to the high low-frequency gain. Additionally, a high-pass filtering and voltage-divided sampling circuit has been added to ensure the normal operation of the integrator and improve the measurement range of the measurement system. Then, according to the relationship between the amplitude–frequency characteristics of the measurement system and the parameters of each component, the appropriate types of components and op-amp were selected to expand the measurement bandwidth. Finally, a simulation verification was conducted, and the simulation results show that this measurement method can effectively expand the lower measurement frequency limit to 20 Hz, correct the low-frequency distortion caused by Rogowski coils measuring lightning currents on transmission lines, and accurately restore the measured lightning current waveform. [ABSTRACT FROM AUTHOR]

Flextensional transducers have been widely used as low-frequency projectors, and these characteristics can be used to develop hydrophones with wider receiver bandwidth and higher sensitivity than conventional products in low-frequency ranges. In this work, we designed flextensional hydrophones of all classes, and compared their acoustic receiver performance to select the most suitable class for a low-frequency broadband hydrophone. For this purpose, basic models of the hydrophones were constructed for all classes and the effects of various structural parameters on the acoustic receiver characteristics of the hydrophones were analyzed. Based on the results, the structure of the flextensional hydrophone of each class was designed to have the maximum receiver bandwidth by an optimization technique while maintaining the receiver voltage sensitivity over a certain level. A comparison of the designed performance led to the selection of the class IV flextensional hydrophone as the most promising one with the widest receiver fractional bandwidth and highest sensitivity. [ABSTRACT FROM AUTHOR]

This study proposes a dual-functional terahertz device based on the Dirac semimetal, serving as both a sensing element and a band-pass filter. The device's operating mode can switch between these two functions by utilizing the phase transition property of vanadium dioxide (VO2). When VO2 is in the insulating state, the device functions as a sensing element. The simulation results demonstrate an impressive refractive index sensitivity of 374.40 GHz/RIU (Refractive Index Unit). When VO2 is in the metallic state, the device functions as a band-pass filter, exhibiting a center frequency of 2.01 THz and a 3 dB fractional bandwidth of 0.91 THz. The integration of these dual functionalities within a single terahertz device enhances its utility in both sensing and filtering applications. [ABSTRACT FROM AUTHOR]

Factories play a crucial role in economic and social development. However, fire disasters in factories greatly threaten both human lives and properties. Previous studies about fire detection using deep learning mostly focused on wildfire detection and ignored the fires that happened in factories. In addition, lots of studies focus on fire detection, while smoke, the important derivative of a fire disaster, is not detected by such algorithms. To better help smart factories monitor fire disasters, this paper proposes an improved fire and smoke detection method based on YOLOv8n. To ensure the quality of the algorithm and training process, a self-made dataset including more than 5000 images and their corresponding labels is created. Then, nine advanced algorithms are selected and tested on the dataset. YOLOv8n exhibits the best detection results in terms of accuracy and detection speed. ConNeXtV2 is then inserted into the backbone to enhance inter-channel feature competition. RepBlock and SimConv are selected to replace the original Conv and improve computational ability and memory bandwidth. For the loss function, CIoU is replaced by MPDIoU to ensure an efficient and accurate bounding box. Ablation tests show that our improved algorithm achieves better performance in all four metrics reflecting accuracy: precision, recall, F1, and mAP@50. Compared with the original model, whose four metrics are approximately 90%, the modified algorithm achieves above 95%. mAP@50 in particular reaches 95.6%, exhibiting an improvement of approximately 4.5%. Although complexity improves, the requirements of real-time fire and smoke monitoring are satisfied. [ABSTRACT FROM AUTHOR]

In order to solve the coupled hysteresis and resonance problems in three-degree-of-freedom tip-tilt-piston piezoelectric stage, a coupled hysteresis model and a coupled integral resonance compensation model are designed. The inverse coupled hysteresis feedforward control combined multi-axis coupled resonance control and high-gain integral tracking controller are used to improve the tracking speed and positioning accuracy of the stage. Firstly, a kinematic model of the stage is built to translate the three-degree-of-freedom motion of the end-effector into the outputs of three piezoelectric actuators. Then, a coupled hysteresis model based on the rate-dependent Prandtl–Ishlinskii model is established and parameterized to simultaneously compensate for the hysteresis of a single piezoelectric actuator and the coupled hysteresis between multiple piezoelectric actuators. The effectiveness of the model is verified by open-loop and closed-loop inverse model feedforward control experiments. Afterwards, a coupled integral resonance compensation model is also established and parameterized to suppresses the resonance and expand the system bandwidth. Finally, the proposed controller is used to conduct tracking experiments on a composite signal, and the results show that the accuracy and speed of trajectory tracking are further improved, and the mechanical coupling between axes are significantly reduced. • A coupled hysteresis model and an inverse coupled hysteresis model are established. • A coupled integral resonance compensation model is established. • The coupling parameters of the two models are identified and optimized. • A composite control method including an inverse coupled hysteresis feedforward and a coupled resonance control is used. • The composite trajectory tracking experiment validates the effectiveness of the composite control methods. [ABSTRACT FROM AUTHOR]

Piezoelectric-driven flexure-based multi-DOF motion stages have been widely employed for nano-positioning applications, in which motion-decoupled stages have been extensively investigated in order to facilitate their motion control efforts. Asymmetric motion-decoupled stage designs are simple in configurations and structures, but would cause parasitic shifts of the moving platform. Fully-symmetric motion-decoupled stage designs can minimize parasitic shifts, but would result in complicated configurations and structures. To tackle such difficulties, a new flexure-based motion-decoupled XYZ stage with a quasi-symmetric 3-Prismatic-Prismatic-Prismatic (3-PPP) configuration is proposed in this work. By adding short flexure-based auxiliary supports to the moving platform, a compact quasi-symmetric stage design is achieved, and the parasitic shifts of the moving platform are significantly reduced. To study the kinetostatic performance of the demonstrated embodiment, an analytic stiffness model is formulated and validated by the FEA method. To achieve minimal parasitic shifts, a stiffness matching approach is proposed for the design optimization of structural parameters. A research prototype of the quasi-symmetric stage is fabricated for experimental validation. Experimental results show that the stage achieves workspace of 43.6 μm × 40.3 μm × 63.2 μm, motion resolution of 25 nm, and parasitic shifts of less than 0.94 %, which indicates that the proposed quasi-symmetric design method is effective to reduce the parasitic shifts of the flexure-based nano-positioning stages. • Compact XYZ stage design with a quasi-symmetric structure and two auxiliary supports. • High accuracy and small parasitic shifts realized by stiffness matching approach. • High stiffness, payload capacity and control bandwidth with PCA direct-driving scheme. [ABSTRACT FROM AUTHOR]

3D point clouds stand as one of the prevalent representations for 3D data, offering the advantage of closely aligning with sensing technologies and providing an unbiased representation of a measured physical scene. Progressive compression is required for real‐world applications operating on networked infrastructures with restricted or variable bandwidth. We contribute a novel approach that leverages a recursive binary space partition, where the partitioning planes are not necessarily axis‐aligned and optimized via an entropy criterion. The planes are encoded via a novel adaptive quantization method combined with prediction. The input 3D point cloud is encoded as an interlaced stream of partitioning planes and number of points in the cells of the partition. Compared to previous work, the added value is an improved rate‐distortion performance, especially for very low bitrates. The latter are critical for interactive navigation of large 3D point clouds on heterogeneous networked infrastructures. [ABSTRACT FROM AUTHOR]

A new method for time‐resolved X‐ray absorption near edge structure (XANES) spectroscopy that enables faster data acquisition and requires smaller sample quantities for high‐quality data, thus allowing the analysis of more samples in a shorter time is introduced. The method uses large bandwidth free electron laser pulses to measure laser‐excited XANES spectra in transmission mode. A beam‐splitting grating configuration allows simultaneous measurements of the spectra of the incoming X‐ray Free Electron Laser (XFEL) pulses and transmission XANES, which is crucial for compensating the pulse‐dependent intensity and spectrum fluctuations due to the self‐amplified spontaneous emission operation. The implementation of this new methodology is applied on a liquid solution of ammonium iron(III) oxalate jet and is compared to previous results, showing great improvements in the speed of acquisition and spectral resolution, and the ability to measure a large 2‐D spectral‐time map quickly. [ABSTRACT FROM AUTHOR]

Spectrally efficient 16 quadrature amplitude modulation‐orthogonal frequency division multiplexing (QAM‐OFDM) system using specifications of commercially available high‐power phosphorous coated LED (PLED) is proposed in this study. To address the challenges of signal attenuation and limited bandwidth, systems integrated with a band pass filter (BPF) after the photodetector and optical preamplifier. The effect of BPF bandwidth and preamplifier gain on the performance of 16 QAM‐OFDM system have been investigated. Results demonstrated that 375 MHz bandwidth evaluated from 1.5 × symbol rate, offered an optimum performance achieving minimum bit‐error‐rate of 3.05 × 10−4. For preamplifier gain of 20 dB, we achieved a maximum distance of 3 m which is limited to 1.5 m for lower gain values. With BPF‐optimized bandwidth and a preamplifier gain of 20 dB, we have achieved a data rate of 5 Gbps for maximum distance up to 2 m while considering the super‐forward‐error‐correction limit of 1.863 × 10−2. With data rate of 6 and 7 Gbps, the distance lower down to 1.8 and 1.5 m, respectively. [ABSTRACT FROM AUTHOR]

A methodology to acquire a wide bandwidth and steep transition of a hybrid ladder filter with the acoustic‐wave‐lumped‐element‐resonators (AWLRs) structure is proposed. Different from previous works, a unit of the new AWLR structure with two lumped elements respectively in series and shunt is proposed. It can change both the series‐resonant frequency and the parallel‐resonant frequency of the acoustic wave (AW) resonator to enhance the bandwidth of the hybrid ladder filter. For the ladder structure, all the AW resonators possess the same resonant frequency and impedance. This ladder structure is also used to keep the steep transition of the hybrid filter. For the validations, two‐stage and four‐stage AWLRs‐based hybrid filters are designed, manufactured, and tested. They include (1) a two‐stage filter with an insertion loss (IL) of 0.9 dB, a fractional bandwidth (FBW) of 1.90kt2 (kt2 is the electromechanical coupling coefficient), a center frequency of 1249.3 MHz, and (2) a four‐stage filter with the IL of 1.3 dB, the FBW of 1.86kt2, the SF30 dB/3 dB (shape factor defined as 30‐dB bandwidth divided by 3‐dB bandwidth) of 2.52, the figure of merit (defined as FBW divided by SF30 dB/3 dB) is 0.74kt2 which is the best result, a center frequency of 1249.4 MHz. [ABSTRACT FROM AUTHOR]

Semianalytical design approach to a triple‐mode resonant, wideband null frequency scanning sectorial monopole antenna is proposed. As is demonstrated, TE3/5,1, TE9/5,1, and TE3,1 mode within a 150°, circumferentially resonant sectorial monopole are simultaneously excited to realize null frequency scanning functionality. The prototype antenna exhibits a wide impedance bandwidth of 75.3%, ranging from 1.40 to 3.09 GHz. Within the frequency band of 1.55–2.70 GHz, the radiation null linearly scans from θ = +90° to +8° with a null frequency scanning sensitivity of 12.9 MHz/°. Moreover, the antenna possesses maximum gain of 2.5 dBi in the backfire, ‐x‐direction, which indicates that it should exhibit quasi‐unidirectional radiation pattern in the azimuth plane. [ABSTRACT FROM AUTHOR]

A metal‐loaded double‐layer unidirectional radiation slot antenna with flat gain is proposed for millimeter‐wave (mm‐wave) operations. Our presented antenna is constituted of a slot antenna with metal vias, an inner floating metal, a metal line, and ground patch. With the help of inner metal excited by the coupling of the slot antenna, an additional resonance point around 26 GHz could be obtained and the antenna gain is enhanced. To verify the design, the antenna has been fabricated with the prepreg technology. The whole fabricated size is only 0.62 × 0.62λ0² with a thickness of 0.057λ0 (λ0 is the free‐space wavelength at 26 GHz). The measured impedance bandwidth is from 25.1 to 26.55 GHz. Moreover, the proposed antenna obtains a wide flat gain (5.78 ± 0.48 dBi) within the bandwidth and stable one‐sided radiation patterns. The above characteristics show that the proposed antenna is a competitive choice for mm‐wave systems. [ABSTRACT FROM AUTHOR]

A Faraday-effect radial interferometer–polarimeter is designed for the National Spherical Torus Experiment-Upgrade (NSTX-U) to measure multiscale magnetic and density fluctuations critical to understanding fusion plasma confinement and stability, including those originating from magnetohydrodynamic instabilities, energetic particle-driven modes, and turbulence. The diagnostic will utilize the three-wave technique with 5 MHz bandwidth to simultaneously measure line-integrated magnetic and density fluctuations up to the ion-cyclotron frequency. Probe beams will be launched radially from the low-field side at the NSTX-U midplane, where the measured Faraday fluctuations mainly correspond to radial magnetic fluctuations that directly link to magnetic transport. A correlation technique will be employed to reduce the measurement noise to below 0.01° enabling detection of small amplitude fluctuations. Two toroidally displaced chords with 7° separation will be installed to measure toroidal mode numbers up to n = 25 for mode identification. Solid-state microwave sources operating at 321 μm (935 GHz) will be used to minimize the impact of the Cotton–Mouton effect. [ABSTRACT FROM AUTHOR]

In view of the high instantaneous bandwidth requirement of modern electronic countermeasures equipment, a 6~18 GHz ultra wideband T/R module with instantaneous bandwidth of 4 GHz is designed in this study. The MCM(Multi Chip Module) and ultrawideband signal transmission technologies are used to realize the requirements of high integration, miniaturization and modularization of T/R components. The structure of T/R compoments, the index budget of transceiver channel, the simulation of broadband signal transmission characteristics and the design of electromagnetic compatibility are described in detail. The test results show that the T/R module has a good performance in the 12 GHz operating bandwidth, the transmit power is greater than 35 dBm, the receive gain is greater than 20 dB, the noise factor is less than 5 dB, and the total delay time is up to 762 ps. [ABSTRACT FROM AUTHOR]