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In this study, a three‐dimensional bandpass frequency selective surface (FSS) with a new fabrication technology is proposed and designed based on slotlines. The proposed FSS consists of silver paste circuits printed on aramid paper, and is vertically and horizontally arranged to form a periodic array in honeycomb structure. To better understand the design principle of the proposed FSS, the equivalent circuit model (ECM), single‐polarized structure, and dual‐polarized structure are presented and analyzed, respectively. The proposed FSS exhibits a passband at 4.1 GHz with a fractional bandwidth of 71.5% at x‐polarization and 66.2% at y‐polarization with reflectivity less than −10 dB. Moreover, the reflection and transmission coefficients have relative stable properties up to 30° for the oblique incidence. Then, the proposed structure is fabricated and measured to verify the design strategies. The measured and simulated results have reasonable agreement under a large variation of incident angles. [ABSTRACT FROM AUTHOR]

How to monitor the freshness of packaged food, the safety of sealed medicine, or the other substances in sealed space wirelessly and environment‐friendly has become an urgent problem in recent years. After summarizing the theory of the LC sensor, a design of a paper‐based resonator (30 mm × 30 mm × 0.15 mm) consisting of a finger capacitor is proposed in this paper. The sensor is embedded inside the package by adhering it to the package's inner wall. Its response is remotely detected through a readout coil. This paper establishes a circuit simulation model and an electromagnetic simulation model to verify the feasibility of the design. Compared with the real object and the theoretical simulation model, the difference between the results only within 1 MHz, which verifies the correctness of the theory. Additionally, the measured results indicate that the resonant frequency of the resonator shifted from 102.441 MHz to 88.195 MHz, after dropping water on the sensor. Besides, the simple fabrication technology and inexpensive sensor material ensure a low cost, thus making this technology economically viable. [ABSTRACT FROM AUTHOR]

In this article, the authors conduct a study of bending effects of a paper‐based printed antenna in order to predict the behavior of an antenna placed inside a package with restricted dimensions. The study begins with a model of an electrical dipole consisting of two misaligned parts to evaluate qualitatively the effect of the angle between two parts and the proportion of their lengths on the radiation properties of the dipole. In order to validate the theoretical prediction, a wide‐band "mushroom‐shaped with two arms" monopole antenna structure printed on 0.104 mm thick paper is proposed. This antenna covers a very wide frequency range from 1.8 GHz to over 10 GHz, including two WLAN bands. Its radiation patterns are nearly omni‐directional at 2.45 and 5.5 GHz. The study of substrate bending effects shows that the matching properties of the antenna are maintained, but the antenna radiation patterns are rotated by an angle with respect to the case without bending. The results of our study can be used to predict the performance of an antenna when it is deformed in a telecommunication set‐top box with restricted dimensions. [ABSTRACT FROM AUTHOR]

A compact 2-element antenna for MIMO applications with performance across the WLAN frequency bands is designed and fabricated on paper with a FUJI Film Dimatix 2800 material printer and conductive ink. This antenna is ∼1.1 cm × 3.5 cm and utilizes co-planar feeding techniques and ground design to allow for resonance in the 2.4 and 5 GHz frequency bands with a minimum 800-MHz bandwidth. The design is established using commercially available products for minimal processing. Factors such as ink handling, printing conditions, and paper selection are discussed qualitatively as they relate to antenna fabrication and performance. Successful simulation and fabrication is reported with low correlation, high isolation, and low reflection. [ABSTRACT FROM AUTHOR]

This letter presents a new technique to fabricate aperture type cylindrical frequency selective surface (FSS) with circular, tripole, and plus shaped element. The cylindrical FSSs exhibit band pass property from 5 to 9 GHz, 11.75 to 14.75 GHz, and 7 to 14 GHz, respectively. A novel method with aluminium foil paper is suggested for fabrication. Cylindrical FSS is fabricated with this technique in laboratory with commercially available aluminium foil paper and is measured practically. In this technique, with the help of laser cutting machine 0.01 mm precision label can be achieved. Both simulated and measured results are in good agreement. The aluminium foil paper made FSS proved to be very light weight, flexible and low cost. [ABSTRACT FROM AUTHOR]

Abstract: A wide band flexible substrate based metamaterial is presented. The metamaterial is fabricated on photo paper using conductive nanoparticle ink targeting flexibility applications. The metamaterial structure shows a wide double negative region of 1.848 GHz (8.298–10.146 GHz). The transmission coefficient of the proposed metamaterial has been measured and verified with simulated one. The perceptible novelties of the proposed work are its simplicity, cost effectiveness, and flexibility with covering wide X‐band microwave spectra. [ABSTRACT FROM AUTHOR]

ABSTRACT Two key components, among several, in the design of a conformal antenna are the planar conductors and the flexible substrates. In this paper, a new approach of using graphene-based conductors instead of copper conductors in the design of a conformal antenna is presented. To determine the conductivity properties of the graphene-based conductor, the copper conductors in a well-known micro-strip transmission line (TL) and micro-strip antenna were replaced with the graphene-based conductors and were analytically evaluated, simulated in a full-wave simulation software and experimentally tested. Overall, it was shown that these graphene-based conductors have a conductivity that is high enough to design a useful micro-strip TL and micro-strip antenna. In particular, a conductivity of σ = 1.94 × [ABSTRACT FROM AUTHOR]

ABSTRACT A significant cost in the widespread deployment of UHF radio frequency identification (RFID) systems has been the passive RFID tags. To address some of this expense, this paper presents an antenna design for UHF RFID tags that can be printed on inexpensive paper substrates and operate in the near field of the UHF reader. This antenna design is based on meander line miniaturization techniques and open complementary split ring resonator (OCSRR) elements to reduce the amount of conducting material required to manufacture the antenna by 30%. For demonstration purposes, a prototype near-field UHF RFID tag was manufactured on a paper substrate and the read-range was measured at 920 MHz. It was shown that useful read-ranges could be achieved while reducing the overall cost and size of the antenna on the RFID tag. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1052-1056, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT A pattern-switchable origami antenna is designed with paper using inkjet-printing technology. The proposed antenna can be switched between loop and dipole antenna modes by folding and unfolding the paper, respectively. Eutectic gallium-indium liquid metal is introduced in order to avoid cracks in the conductive ink when the paper is folded. The performance of the proposed antenna is demonstrated through simulation and measurement results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:668-672, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents the design, manufacturing, and measurements of antennas on paper, realized using ink-jet printing of conductive inks based on nano-silver particles (nSPs). The extraction of the substrate characteristics such as the dielectric constant and dielectric loss is performed using a printed ring resonator technique. The characterization of the nSPs conductive inks assesses different parameters as sintering time and temperature. Two antennas are realized corresponding to the most common needs for wireless sensor networks in Trains Environment. The first one is a patch antenna characterized by a broadside radiation pattern and suited for operation on metallic structures. The second one is a quasi-yagi antenna, with an end fire radiation pattern and higher directivity, without requiring a metallic ground plane. Both antennas present a good matching ( S11 < −20 dB and S11 < −30 dB, respectively) and acceptable efficiency (55% and 45%, respectively) for the paper substrate used at the center frequency of 2.4 GHz, corresponding to the first channel of the IEEE 802.15.4 band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:754-759, 2016 [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]

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]

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]

Significant research and development in the areas of microwave photonics in Brazil are presented in this paper. These include direct microwave modulation of semiconductor laser diodes, optical control of MESFETs and HEMTs as well as high speed fiber optic components. Future directions for research in this area are discussed. [ABSTRACT FROM AUTHOR]

We systematically analyze the mode-coupling effects of stress-induced long-period gratings (LPGs) using photonic crystal fiber (PCF). Two Mach–Zehnder interferometers based on this grating are demonstrated. These devices offer the unique advantages of being tunable and reconfigurable. Their good interfering efficiency makes them promising for wavelength-selective filters in WDM communication systems. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1379–1383, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21647 [ABSTRACT FROM AUTHOR]

A method to extract the elements of the small-signal equivalent circuit and the noise parameters (NPs) of heterojunction bipolar transistors (HBTs) is presented. The extraction is done by simultaneous fitting of the measured S-parameters, noise figure (for a well-matched impedance), and NPs (estimated using the so-called F50 method). An additional error term, given by the root square sum of the differences between the NPs estimated from the F50 method and the NPs directly computed using the Hawkins model, is considered in order to avoid nonphysical results in the extraction of the intrinsic noise sources. To obtain the initial values of the equivalent-circuit elements, analytical expressions are applied under a number of bias conditions, namely, reverse bias, forward bias, and active bias. Experimental verification of the extraction of the equivalent-circuit elements and NPs of an HBT, up to 8 GHz, are presented, and the NPs are compared to those measured with an independent (tuner-based) method. The behavior of Fmin, extracted using the proposed method, as a function of the HBT collector current, is also presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1372–1379, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21649 [ABSTRACT FROM AUTHOR]

A compact dual-WLAN-band antenna, in the shape of a paper clip, is presented. The antenna can be easily manufactured by bending few times a single copper wire with a length of about 65 mm, and it operates in the 2.4 and 5.2 GHz bands in the WLAN environment. In addition to the simple configuration, the antenna is easily fed by a 50-Ω mini-coaxial cable which allows it to be flexible in a defined location for installation. An experimental prototype of the proposed antenna with the overall dimensions of about 5 mm × 23.5 mm is constructed, tested, and demonstrated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2572–2574, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23760 [ABSTRACT FROM AUTHOR]

Moreover, they are particularly grateful to the authors of all the submitted papers for their efforts and contributions to this Special Issue, and to the reviewers for devoting their valuable time and expertise to review the submitted manuscripts. Authors of the accepted and presented papers during the iWEM 2021 were invited to submit expanded versions of their conference papers in this special issue. This special issue of Microwave and Optical Technology Letters (MOTL) includes nine expanded papers from the 2021 IEEE International Workshop on Electromagnetic: Applications and Student Innovation Competition (IEEE iWEM2021). [Extracted from the article]

This paper presents a 4th-order accurate implicit multistage finite-difference time-domain (IMS-FDTD) method. The analysis of the stability shows that this IMS-FDTD method is unconditionally stable. In addition, its numerical-dispersion relation is derived and the analysis shows that its performance is better than those of conventional unconditionally-stable implicit FDTD methods and is even better than those of some conditionally-stable explicit FDTD methods, such as the Fang(2, 4)-FDTD method. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1383–1385, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21646 [ABSTRACT FROM AUTHOR]

Vertex plates are commonly used to improve the return loss of primary-fed reflector antennas. We propose a new type of vertex plate with a Gaussian thickness profile that gives lower far-out sidelobes of the radiation pattern of the reflector antenna than the standard vertex plate with constant thickness. We derive the dimensions of this vertex plate needed to cancel the field at the focus of the reflector. We apply the design rules to improve the return loss (RL) of a primary-fed reflector with hat feed, and simulate it by using a computer code based on the finite-difference time-domain (FDTD) technique. The results verify the improvements of the radiation pattern obtained by using a Gaussian vertex plate rather than a standard one. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 125–129, 1999. [ABSTRACT FROM AUTHOR]

This article describes a novel fabrication technology for photonic integrated circuits (PICs) that easily produces a smooth and high-quality waveguide coupling between interconnected guided, wave elements. This technique is based on the in-plane quantum energy control selective area metal-organic vapor-phase epitaxy of multiple-quantum-well (MQW) structures. Good local quantum energy control over a very wide range is shown for simultaneously grown MQW crystals, Moreover, the crystal quality, well/barrier hetero-interface, and flatness and uniformity of these selectively grown MQW crystals are bound to be as good as those of normally grown crystals, This technique is applied to an electroabsorption modulator/distributed feedback laser integrated device. Superior device performance, including a tow threshold and high-efficiency lasing properties, as well as high-speed, low-drive-voltage, and low-chirp modulator characteristics are attained due to improved optical coupling. easy fabrication, and sufficient crystal quality of selective grown MQW structures. 2.5 Gbit/s penalty-free dam transmission is demonstrated over an 80-km normal single-mode fiber, which, combined with long-term device reliability, makes this integration technique more attractive for practical fabrication of semiconductor PICs. [ABSTRACT FROM AUTHOR]

High-speed, low-driving-voltage operation of multiple-quantum-well (MQW) external modulators based on the quantum-confinement Stark effect (QCSE) operating at tong wavelengths are reviewed. We discuss the design and characteristics of ultrafast intensity and phase MQW modulators that have been developed by our group and we compare them with those of other material systems end structures based on a defined figure of merit for external modulator. In addition, we discuss a new integrated tight source that enables external modulation of an in-plane DFB laser to reduce wavelength chirping and coupling loss with a laser and a modulator. Finally, we describe new applications for optical soliton pulse generation using the above intensity modulator. [ABSTRACT FROM AUTHOR]

We theoretically calculate the optical gain of In1-xGaxAs/InGaAsP strained quantum wells on (001) InP substrates based on strain-dependent conduction-band and valence-band structures. Using the calculated gain, we estimate threshold current density of the strained quantum-well lasers. We show that both biaxial compressive and tensile strains can lower the threshold current density by ½-1/3, and clarify the mechanism for the reduction. [ABSTRACT FROM AUTHOR]

The GaAs MESFET is a light-sensitive device. For normal microwave applications this is considered an undesirable property, and device manufacturers attempt to minimize it. In the last decade researchers discovered ways of utilizing this effect. In this article we present briefly the optical detection properties of the MESFET and describe some typical applications. [ABSTRACT FROM AUTHOR]

We discuss high-speed waveguide modulators for optical fiber communications that employ semiconductor quantum wells, with emphasis on electrorefractive devices. The prime advantages of quantum-well material in this application are provided by enhanced electrooptic effects that allow ultracompact devices with low drive voltage requirements. The small size is particularly important for low-cost monolithic integration with other components for guided-wave photonic integrated circuits. In our devices, compactness is also key for obtaining high electrical modulation bandwidth. [ABSTRACT FROM AUTHOR]

Methods of millimeter-wave signal generation are presented using frequency multiplication by optical comb generation, direct generation using optical oscillators, and mixing between CW optical sources. [ABSTRACT FROM AUTHOR]

This paper presents a 132–140 GHz power amplifier (PA) array in 0.13‐µm SiGe BiCMOS technology. The four dielectric‐loaded end‐fire antennas are integrated with the PA array on chip. With the absence of the lossy power combining networks at the output, the presented PA array achieves a measured maximal effective isotropic radiated power of 29.7 dBm. The array size is only 6.14 × 2.49 mm2 and consumes 5.16 W from a single 4 V DC supply. [ABSTRACT FROM AUTHOR]

Two miniaturized wire antennas using a 3D space-filling Hilbert-curve (HC) fractal geometry were constructed on a Kodak photo paper using inkjet printing. The proposed antennas each had the 3D dimensions of an 8 cm3 box and operate at very high-frequency band frequencies of 238 and 147 MHz. We wrapped 4- and 2-mm-thick planar wires around a 3D box made of photo paper using second- and third-order HC space-filling fractal designs. The electrical volumes of the proposed second-order HC and third-order HC fractal antennas were 0.004 λ0 × 0.004 λ0 × 0.004 λ0 and 0.002 λ0 × 0.002 λ0 × 0.002 λ0, respectively. The operation of the proposed antennas was verified using simulation and measurement results. [ABSTRACT FROM AUTHOR]

In the weapon test range, the space projectile explosion position parameter at the terminal trajectory is an important index to evaluate the damage performance of the projectile fuze. Due to the random distribution of the falling dispersion of the projectile, it is difficult to test the projectile explosion position in the long‐range terminal trajectory falling area. To solve this problem, this paper proposes a method for measuring the projectile explosion position based on ultra‐wide imaging with a multi‐lens array. A curved multi‐lens array optical imaging system is designed and the parameter calculation method of the optical system is presented. The relationship between the space projectile explosion position and the center of the sub‐eye lens and the relationship between the center of the sub‐eye lens and the imaging point of the image sensor is established according to the imaging principle of the optical system. The object image relations of any seven adjacent sub‐eye lenses of the curved multi‐lens array optical imaging system are combined and the calculation model of the space projectile explosion position is deduced. The experimental results verify that the designed curved multi‐lens array optical imaging system and the calculation model of the projectile explosion position proposed in this paper are reasonable. [ABSTRACT FROM AUTHOR]

This paper presents a 30–36 GHz limiter low‐noise amplifier (limiter‐LNA) MMIC for high power and high mobility millimeter‐wave radar systems. The PIN‐diode limiter network and the LNA are codesigned to realize high input‐power handling capability, good small‐signal performance, and small chip area. A two‐state matching capacitor is presented to improve both the input‐power handling capability at the high input‐power level and the input return loss at the small‐signal level. The proposed circuit is fabricated with a combined PIN/0.15‐µm‐GaAs‐pHEMT process. The limiter‐LNA is capable of handling 39 dBm continuous wave (CW) input‐power without failure with only two limiter stages. The measured noise figure is 1.8–2.5 dB, the small‐signal gain is 18.5 ± 0.5 dB, the output power at 1 dB compression point is larger than 11 dBm, and the dc power consumption is 72 mW. The chip area, including testing pads, is only 2.1 mm × 1.0 mm. This limiter‐LNA MMIC is believed to have the highest input‐power handling capability and smallest chip area among limiter‐LNA MMICs at this frequency range reported up to date. [ABSTRACT FROM AUTHOR]

This article presents the realization of a bandpass filter on a flexible biopolymer substrate with a suitable fabrication process. We used copper adhesive tape and laser structuring to fabricate the filter based on a quasi‐lumped microstrip structure. The filter characteristics are a central frequency of 2.45 GHz, a bandwidth of 20%, and insertion loss of 1.2 dB. It is demonstrated that the filter's performance remains almost constant under different bending, folding, and rolling conditions. The results show that the proposed bio‐sourced polymer is a good candidate for flexible green electronics and wearable applications. [ABSTRACT FROM AUTHOR]

This paper proposes a wide bandpass filter (BPF) with high out‐of‐band suppression and wide stop‐band characteristics. An interdigital coupled line structure loaded by a rectangular resonator ring is employed to generate three transmission poles in the pass‐band and an additional transmission zero (TZ) in the stop‐band, thereby achieving a wider pass‐band while enhancing stop‐band suppression. Compared to traditional coupled‐line structures, the structure mentioned in this paper offers significant advantages in designing filters with wide stop‐bands and high out‐of‐band suppression. Furthermore, open‐circuit T‐stub, and a pair of open‐circuit stub are used to generate multiple parasitic TZs at high frequencies, which is adopted to further expand the stop‐band range. Measurement results shows that the insertion loss of the BPF is of −2.86 dB within the range of 7.05–12.20 GHz. The stop‐band ranges from 13 to 48 GHz with an out‐of‐band suppression of −27 dB, especially when the out‐of‐band suppression is −40 dB, the stop‐band frequency range is 16.40–31.35 GHz. [ABSTRACT FROM AUTHOR]

This paper points out that the commonly used normalized frequency for noncircular dielectric waveguides, which is based on the semiminor axis, causes the cross‐sectional area to vary with the cross‐sectional shape. Consequently, the shape effects described with the conventional normalized frequency are not due to the shape alone but the combined effects of the shape and area. Our numerical results show that the area effect is greater than the shape effect. An improved definition of normalized frequency based on an equivalent radius is proposed in this paper. Conversion formulas to convert from the conventional normalized frequency to the proposed normalized frequency are provided for elliptical and rectangular waveguides. Our numerical results show that the shape effects described by the proposed normalized frequency are free from the area effect. Consequently, the proposed normalized frequency is more accurate than the conventional normalized frequency in describing the shape effect of noncircular dielectric waveguides. [ABSTRACT FROM AUTHOR]

Waterborne bacteria cause many dangerous diseases as well as several health‐related issues hence detection of them is a global challenge today. A plus‐shaped graphene sensor to detect waterborne bacteria is presented in this paper. The detection mechanism is based upon the refractive index difference between waterborne bacteria sample and pure water which causes a change in resonance peak in the transmittance graph. The use of graphene material increases the sensitivity and also gives the tuning behavior by changing its potential. The effect of various parameters such as sensitivity (S), Q factor, figure of merit (FOM), and detection limit are discussed in the paper. The maximum values Q factor and FOM are 13.46 and 4.03 RIU−1 respectively. The minimum detection limit is 0.277 RIU. The proposed sensor exhibits the highest sensitivity of 255 GHz/RIU at the optimum condition which is comparably higher than previously published papers on biosensors. The proposed design with its highest sensitivity and good detection parameters can be helpful in detecting waterborne bacteria. [ABSTRACT FROM AUTHOR]

In this study, a novel freeform surface lens coupler is designed to realize the coupling functions in the hollow‐core photonic crystal fiber (HCPCF) resonator optical gyroscope. One surface of the lens is an ellipsoid. Coupling of the two HCPCF loop's ports can be directly accomplished via reflection on the ellipsoid surface. The other surface of the lens is the Biconic Zernike surface. Transmitting through the above two surfaces, the coupling between the intracavity and extracavity is completed. In this paper, simulations were performed based on two types of HCPCFs, a hollow‐core photonic bandgap fiber of HC19‐1550 and a state‐of‐the‐art nested antiresonant nodeless fiber. The volume of the lens coupler is calculated to be approximately 4 × 2 × 4 mm3. The simulation results show that the intracavity coupling loss can be as low as 0.011 dB, and the coupling loss between the intracavity and extracavity can be as low as 0.4 dB. Compared with the traditional fusion scheme between hollow‐core fiber and polarization‐maintaining fiber, the freeform surface lens coupler in this paper can achieve lower coupling loss and higher resonance fineness. Compared with other spatial coupling schemes, it has lower coupling loss and fewer coupling components. [ABSTRACT FROM AUTHOR]

In order to understand the PA's indexes, degradations with respect to the temperature changes before suppressing such degradations or compensating those temperature effects of the PAs. The degradations of the gallium nitride (GaN) PA indexes under different temperature conditions with a fixed relative humidity of 85% are investigated experimentally. The S21, power‐added efficiency (PAE) and output power of the PA degrade with the increase of the temperature. The main reasons for these degradations are discussed and analyzed in this paper. The results presented in the paper can help designers to understand the temperature effects on degradations of GaN PA indexes comprehensively so that the designers could consider the effects in the design cycle of the temperature compensation circuits in advance. [ABSTRACT FROM AUTHOR]

In this paper, digital parallelization and fractional delay‐based novel methods are proposed for the realization of high bandwidth, high‐resolution Ku‐band radar target simulator with 2.5 GHz intermediate frequency. High bandwidth waveform from radar is sampled by high‐speed Analog to Digital Converter, and samples are parallelized in Field Programmable Gate Array (FPGA) to work at the nominal clock frequency. In Digital RF Memory‐based target simulator, for finer range resolution, the FPGA clock frequency needs to be increased, which leads to increased system design complexity. The finer range resolution is accomplished without altering the system clock frequency using variable fractional delay filters and the digital parallelization methodology is proposed in this paper. The maximum target range that can be simulated is 20 km. As a result, memory requirements, computational complexity, and power dissipation are reduced. Finally, simulation and implementation results are presented. [ABSTRACT FROM AUTHOR]

In this paper, work on a Ganesha‐shaped semi‐transparent patch antenna is presented for its use in vehicular application. The design of the antenna is opted from a commercially available Ganesha sticker that is mostly placed on the vehicle's window panes as a symbol of an auspicious deity. The geometry of the sticker without any variation in its dimension is made to work as an antenna. The antenna is fabricated using adhesive copper tape on a glass slab backed by an AgHT‐8 transparent conducting sheet which acts as the ground plane. Microstrip inset feeding technique is used to excite the patch and its return loss performance and free space radiation pattern measurements are carried out. Measured results show promising performances that can be used in future vehicular applications and are in good comparison with that of the simulated results. [ABSTRACT FROM AUTHOR]

A novel array antenna diagnosis method based on a deep residual shrinkage network (DRSN) is introduced in the case of linear arrangements. The failure of array elements often leads to significant changes in the far‐field pattern of an array antenna. Therefore, the failure diagnosis of array antennas can be carried out according to the far‐field pattern data. In this paper, the proposed method based on DRSN can automatically learn useful features from the sampled far‐field patterns of the linear array and find the mapping relationship between different far‐field patterns and failure scenarios, to find the locations and number of faulty array elements. Experimental results show that the proposed method based on DRSN has higher diagnostic accuracy in the noise environment at low signal‐to‐noise ratios by comparing with the traditional machine learning algorithm—support vector machine. [ABSTRACT FROM AUTHOR]

In this paper, a behavioral model for the variable gain amplifiers working in the liner region is proposed. An iterative least‐square algorithm for complex curve fitting is proposed to model the variable gain amplifiers as an infinite impulse response filter. The polynomial fittings are used to obtain the coefficient matrix for the gain response and phase response to the frequency at different control voltages. The relationship between gain and control voltage is fitted by a hyperbolic tangent function. The modeling flow is given in this paper. Comparing the frequency response of the behavioral model and circuit model, the simulation results are similar at the operating frequency. Finally, an application is given, which is used to compare the effect of the nonlinear phase system with two different band signals modulated by 4QAM. This application proves that the model can be used in the simulation of large‐scale systems. [ABSTRACT FROM AUTHOR]

This paper introduces a beam‐scanning holographic antenna composed of a substrate‐integrated waveguide (SIW) feeding structure and a rectangular microstrip array. The antenna innovatively combines holographic theory with liquid crystal electrical tunability to realize single‐frequency large‐angle beam scanning function which can effectively solve the problem of beamforming reconfiguration in traditional array antenna systems. In this paper, the variation of dielectric constant of liquid crystal under different bias voltages is quantitatively analyzed. Additionally, the beam forming technology is analyzed under hologram amplitude weighting theory. The relevant theories are verified by manufacturing and testing. The prototype antenna achieves the ultra‐wide beam scanning angle of −63° to 63° at 36 GHz. [ABSTRACT FROM AUTHOR]

The traditional infrared inspection of substations is usually done by employees with handheld infrared equipment, but the traditional inspection efficiency is not high, and some of the inspection locations have harsh environments, high voltage levels, and high‐risk factors. Given the above problems, this paper proposes an improved defect detection algorithm for substations based on YOLO v7 to solve the difficult problem of infrared inspection of substations. First, the lighter SE‐GhostNetV2 feature extraction network is designed to reduce the computation volume; second, the de‐weighted BIFPN structure is designed for the substation infrared image features to improve the ability of information interaction; finally, the new C‐NWD Loss is proposed to realize the detection of smaller substation equipment and reducing missed detections. The experimental results show that the hybrid accuracy of the algorithm designed in this paper is improved from 92.1% to 96.6%, the model parameters are reduced by 40.1%, the computation amount is reduced by 65%, the detection speed is improved by 87 FPS, and the false detection and missed detections is less, which can achieve real‐time infrared inspection of substations and solve the difficulties existing in traditional substation infrared detection. [ABSTRACT FROM AUTHOR]

In this paper, we propose an array antenna that can work in reflection and transmission modes simultaneously or separately. Reflection and transmission at two frequencies are determined by designing and implanting frequency selective surfaces for the antenna. An antenna array prototype including 14 × 14 units and a horn‐fed antenna is designed and measured. The peak gain is 24.6 dBi when the array operates in reflection mode at 12 GHz and 21.3 dBi in transmission mode at 7 GHz. The peak gains are at least 10 dBi higher than the feed source. Moreover, a shift in the beam direction was observed when the feed horn moved along the axis during the measurement. A ±16.4° beam scan can be achieved with a ±60 mm shift in the feeder, as presented in the paper. The proposed transmission/reflection array antenna has potential applications in wireless communication systems. [ABSTRACT FROM AUTHOR]

In this paper, we report the first Q‐switching operation utilizing black phosphorus (BP)/SnSe2 heterojunction as the saturable absorber (SA) in an Er‐doped fiber laser. The BP/SnSe2 heterojunction was prepared by the liquid phase combination method and its properties were observed. Stable Q‐switching operations were achieved based on the BP/SnSe2 SA. The maximum peak power of 71.27 mW and the minimum pulse width of 910 ns were produced, respectively. This paper demonstrates the pulse modulation characteristics of BP/SnSe2 heterojunction SA in the midinfrared region for the first time, laying an important foundation for the application of heterojunction based on BP and two‐dimensional transition metal dichalcogenides. [ABSTRACT FROM AUTHOR]

We proposed a theoretical study of silicon nitride ring resonator configuration for the application of refractive index sensing. In this paper, a slot waveguide has been used to couple the light into the slab ring structure. We have designed the slab ring and slot waveguides with silicon nitride (Si3N4) on a substrate made of silica (SiO2). Transverse electric (TE) mode has been used for the entire analysis at an operating wavelength of 1550 nm. The presented structure has been geometrically optimized to get the better transmission results. The design shows a resonance wavelength of 1538.74 nm when the cladding refractive index(ntop) $({n}_{{top}})$ is equal to 1, which is placed at the top of the slab ring structure. We have also calculated the effect on the transmission curve for different waveguide parameters. For, ntop=1.35 ${n}_{{top}}=1.35$ the structure achieves a resonance wavelength around 1563.65 nm. The geometrically optimized structure achieved a Q‐factor of 750 and a sensitivity of 70 nm/RIU. In the proposed paper, the shift in the resonance of the transmission spectrum has been utilized to detect the Refractive Index (RI) changes on the surface of the ring. Therefore, the proposed structure can be used effectively in the applications of refractive index sensing. [ABSTRACT FROM AUTHOR]

In this paper, a novel algorithm based on logistic regression digital backpropagation (LR‐DBP) is proposed to mitigate the effect of dispersion and nonlinearity in a long‐distance optical transmission system. The LR‐DBP can evaluate nonlinear effects by estimating the cross‐entropy error and adjusting the structure of DBP. The experiment is setup to demonstrate an 80 Gbit/s 16QAM signal transmitted across 1000 km single‐mode fiber. The results show that LR‐DBP achieves a 1.8 dB launch power improvement over the dispersion compensation algorithm and a 0.6 dB launch power gain with DBP. The proposed algorithm could obtain with 19.2% computational complexity decrease and 19.6% central processing unit (CPU) running time decrease by calculating the average numbers of real multiplications and CPU running times. [ABSTRACT FROM AUTHOR]

Spatially offset Raman spectroscopy (SORS) is an important branch derived from conventional Raman spectroscopy. It has the characteristics to realize the concealed component identification covered by opaque and translucent media nondestructively and rapidly. This technology gradually plays an important role in basic and applied research of numerous areas. This paper focuses on the SORS potential application in food quality and safety inspection, and a SORS detection system has been setup. The ingredients of various concealed food additives have been identified by SORS and the optimum offset distance for detection has been obtained. Meanwhile, the identification effectiveness of the system for low‐concentration additives in real foods has also been evaluated. [ABSTRACT FROM AUTHOR]

In this paper, the ginsengs from five ginseng origins are discriminated by using laser‐ induced breakdown spectrum (LIBS) combined with random forest‐ support vector machine (RF‐ SVM) and random forest‐ multilayer perception (RF‐ MLP) machine learning algorithms. The raw LIBS of ginseng is pretreated by using the wavelet threshold method, denoise the background information and normalazation to improve the signal‐ to‐ background ratio and the experimental reliability. The RF algorithm is used to select 10 characteristic spectral lines as the input vectors of the MLP and the SVM models to identify the ginseng orgin. The experimental results show that the discrimination accuracy rates of RF‐ MLP and RF‐ SVM models are 99.75% and 99.5%, respectively. The disrimination accuracy of ginseng origin used in the RF‐MLP machine algorithm model is slightly higher than that of the RF‐ SVM model, and then calculated the speed of the RF‐ MLP model is faster than the RF‐ SVM model. The results show that LIBS combined with machine algorithms are both promising rapid discrimination methods for ginseng origin. [ABSTRACT FROM AUTHOR]

This paper designs a mesa‐structured monolithic microwave integrated circuit (MMIC) limiter working in C‐band. The quasi‐vertical Si‐based PIN diodes are heterogeneously integrated on the SiC substrate with high thermal conductivity, such that the parasitic parameters are greatly reduced and the power capacity is enhanced. According to the measured results, a maximum insertion loss of 1.1 dB and a minimum return loss of 17.69 dB for both input and output terminals are realized to cover the 5–6 GHz frequency range. The flat leakage of 23 dBm is achieved for a 150 W continuous wave and 370 W pulse input signal level. We believe the proposed MMIC limiter provides an effective tool that can be used in the transmit‐receive modules working in C‐band. [ABSTRACT FROM AUTHOR]

This paper presents three devices of biosensors for glucose concentrations. A resonator based on the defected ground structure (DGS) was designed and the optimizations for the single square and both squares of the DGS via adaptive genetic algorithm were applied to enhance the performance of the sensors including the Q‐factor and the electric field distribution. The fabricated devices of the best optimized one exhibited an enhanced Q‐factor of 442 and a sensitivity of 142.2 MHz/mgml−1, which is more than 2.37 times than the basic structure. [ABSTRACT FROM AUTHOR]