Search

Microwave diplexers are often designed iteratively via manual channel-by-channel or resonator-by-resonator local optimization procedures due to high dimensionality in design variables and the complexity of structures. A one-off automated diplexer optimization method is yet to be developed. To achieve this, other than improved optimizers, an effective objective function (OF) is critical to allow optimizers to find the desired designs. This letter realizes an automated diplexer design by proposing key performance indicator (KPI)-based objectives. The KPIs are extracted from S-parameter responses. An all-resonator diplexer with 22 variables and a Tee-junction diplexer with 23 variables are designed using the proposed method via one-off optimization, showing 100% and 80% success rates, respectively.

This article presents an efficient yet simple design approach to highly miniaturized cavity-backed self-diplexing antenna (SDA) with high-isolation. The structure employs a shielded quarter-mode substrate integrated waveguide (QMSIW). Two U-shaped slots are engraved on the top conducting plane, which realize two frequency bands and significant size reduction. The slots are excited by two independent $50\Omega $ orthogonal feed-lines to achieve high isolation while enabling radiation at 3.5 GHz and 5.4 GHz. The proposed design approach allows us to design the two frequency bands independently from each other. The SDA structure is verified using an equivalent circuit model, full-wave electromagnetic (EM) analysis, and experimental validation of the antenna prototype. Excellent consistency between simulated and measured responses has been demonstrated. According to the measurement, the SDA has peak gains of 5.26/5.60 dBi at 3.5/5.4 GHz, and the return loss better than 21.6 dB. The isolation between ports is greater than 40 dB, whereas excellent front-to-back-ratio and co-to-cross polarization are obtained for the proposed SDA. Furthermore, the total size of the SDA is only $0.129~\lambda ^{2}$ , with $\lambda $ being the guided wavelength at 3.5 GHz.

A pattern reconfigurable dual-port multiple-input multiple-output (MIMO) antenna system utilizing Characteristic mode theory is proposed at 2.45GHz. By using the selective incentives of four characteristic modes, six pairs of balanced inductive exciter (BIEs) and the antenna are integrated to realize the selective incentives of the four patterns. In the feeder network, by changing the state of the PIN diode, the two ports realize selective incentive to obtain four working states. The test results show that the pattern reconfiguration technique is reliable and can be used in other types of structures.

An efficient space-mapping-based tuning software system is implemented with a user-friendly GUI in Matlab for the automated filter tuning process. The proposed software system is integrated into a tuning system for achieving fast and reliable filter tuning. In this paper, a postfabrication bandpass filter is given to validate the tuning performance of the SMT software system.

This paper presents a novel method using characteristic modes theory (TCM) to design the neutralization line (NL) for a dual-band multiple-input multiple-output (MIMO) antenna to achieve decoupling. A properly designed arc metal NL introduces new characteristic currents which in the opposite direction to the original characteristic currents thus achieving the effect of decoupling greater than 30 dB at resonance point. Simulated results show that the impedance bandwidths of the antenna are 0.42 GHz (2.27–2.69 GHz) and 0.83 GHz (5.01–5.84 GHz) when $S_{11}\leq-10\ \text{dB}$ , and the relative bandwidths reach 16.1% and 19.3%, respectively, which is suitable in WLAN wireless communication system.

This paper proposes a feature-based surrogate-assisted Harris hawks optimization (FBSAHHO) algorithm for microwave filters. The method is constructed in three steps. Firstly, the vector fitting technology is used to extract the features (parameters of a transfer function) of the electromagnetic (EM) responses. Secondly, artificial neural networks are trained to establish the relationship between design parameters and the extracted features. Thirdly, a surrogate is generated using the filter frequency responses recovered by substituting obtained features into the transfer function. Lastly, Harris hawks optimization algorithm is adopted to find optimal solutions using the surrogate,. A fourth-order coaxial cavity filter is used to verify the proposed method. Combining Harris hawks optimization with surrogate-assisted modeling algorithm demonstrates faster and better convergence than other surrogate-assisted and direct optimization algorithms for filter design.

The paper discusses low-cost design closure of antenna structures. Our approach exploits trust-region (TR) gradient search with antenna response gradients updated by a sparse application of finite differentiation, limited to the principal components of the Jacobian matrix. Numerical results demonstrate superiority of the method over benchmark procedures: sixty percent savings are achieved compared to the reference algorithm without compromising the design quality.

A novel local enhanced sampling strategy is proposed for microwave component optimization in this paper. A greedy-like method is employed to increase the samples near potential optimal solutions to facilitate optimization-oriented modeling. The Ackley test function and a microwave filter are used to verify the ability of the local enhanced sampling strategy in surrogate-based optimization. It is shown that our proposed sampling method promotes the ANN model to obtain better optimization results. We also investigate the effect of numbers of layers and nodes of the ANN model on the modeling accuracy.

In this communication, a novel design approach to design of highly compact quad-band branch-line balun (BLB) is presented along with the implementation and experimental validation of the structure. A quad-band transmission-line is obtained by adding one coupled-line between two-series transmission-lines used to replace the traditional 90° microstrip-lines of a single-band BLB. The even/odd-mode technique is employed to derive the closed-form formulas and facilitate the analysis of the quad-band properties. The proposed concept is verified through fabrication and measurements of a quad-band BLB operating at 1.0, 2.7, 4.1 and 5.8 GHz. The manufactured quad-band BLB provides a reflection coefficient better than −20dB with a magnitude imbalance smaller than 0.45dB. Furthermore, the fabricated prototype (0.051λ g 2) exhibits a size reduction of 59.2% and 84.9% when compared to a single-band balun (0.125λ g 2), and the recent quad-band BLB (0.336λ g 2) reported in the literature, respectively.

A novel approach to design a quad-band impedance transformer (QBIT) is presented. The primary purpose of this transformer is to match an extremely high load impedance to a source impedance of 50Ω at four distinct frequency bands with suppression of the spurious passband. The proposed QBIT is constructed using a π-shaped topology and two series microstrip-lines. The ABCD matrix method is employed to derive closed-form design formulas. The latter are employed to obtain the circuit parameters that allow for matching extremely high load impedances. For validation, two prototypes of QBIT realized to match 500Ω and 1500Ω loads are fabricated and measured. The simulated and measured transformer characteristics are in good agreement.

Efficient modeling method accelerates computer-aided antenna design. In this paper, a novel Gaussian process regression (GPR) modeling based on landmark isometric feature mapping (LISOMAP) for antennas is proposed to improve the accuracy of modeling. In the GPR-LISOMAP method, LISOMAP, a dimension reduction method, is used to reduce the dimension of data for eliminating useless information. GPR is utilized as the modeling method to establish the relationship between antenna design space (multiple inputs) and response space (multiple outputs). The proposed modeling method is demonstrated by a circularly polarized antenna. Numerical results show that the GPR-LISOMAP method improves the accuracy of antenna modeling.

In this article a simple compact (0.28 λ g 2) substrate integrated waveguide (SIW) based self-diplexing antenna is proposed. The self-diplexing antenna consists of an SIW cavity, two off-centered stepped patches and two feeding ports. The whole design is developed in a simple three step process. In first step two patches of different lengths are created on the top side and fed separately by two 50Ω feedlines to operate at two different frequencies. In second step, to maintain acceptable isolation the ports are equally off-centered in opposite directions. In the last step, to further improve the isolation the patches are modified to stepped shape. The proposed antenna operates at 5.23 GHz (for WiFi) and at 5.8 GHz (for ISM band) independently/simultaneously with peak gain of 5.22 dBi and 5.1 dBi respectively. At both the resonant frequencies the antenna possesses > 18 dB front-to-back-ratio. Importantly, the design allows each resonant frequencies to be tuned separately using single design parameter. A prototype of the prosed self-diplexing antenna is fabricated and characterized. Good agreement is obtained between the simulated and measured results. As per its performance and compactness the proposed antenna is a suitable candidate for indoor WiFi and ISM band applications.

Antenna and Wave Propagation course is regarded as an important course for senior undergraduates or postgraduates majoring in electrical engineering, especially communication engineering. This article presents an implementation of project-based learning in antenna and wave propagation course. A project-based learning component is developed to supplement traditional classroom learning. It motivates the students to apply the textbook theory to real-world engineering problems, allows meaningful collaborations between the students, and boosts students’ self-learning capability. Demonstrated by project results and student feedbacks, incorporating project-based learning into traditional classroom learning benefits both student learning outcomes and student personal development.

Fast surrogate models may alleviate the difficulties pertinent to high computational cost of electromagnetic (EM)-driven design procedures. Approximation surrogates are by far the most popular but their applicability to antenna modeling is severely limited by the curse of dimensionality. Domain confinement, as in the recently proposed nested kriging approach, offers a viable workaround this issue, in particular, enables the construction of reliable surrogates over wide ranges of antenna operating conditions and geometry parameters. Unfortunately, the original nested kriging method requires the user to set up the domain thickness (the ratio of its lateral to tangential size). The value of this parameter is critical for achieving a proper balance between the model predictive power and the cost of training data acquisition. This paper proposes a procedure for automated a priori determination of the domain thickness and highlights the computational benefits associated with the employment of the presented approach using a dual-band dipole antenna example.

Full-wave electromagnetic (EM) analysis permits reliable but often computationally expensive evaluation of microwave devices. In particular, multiple simulations (e.g., entailed by numerical optimization procedures) may generate CPU costs that are unacceptable or at least significantly slow down the design cycles. This problem may be mitigated by the employment of fast surrogate models. Unfortunately, conventional techniques are not suitable for handling structures described by multiple geometry/material parameters and featuring highly nonlinear frequency characteristics. This paper proposes a novel modeling approach that incorporates variable-fidelity EM simulations into the recently reported nested kriging framework. A combination of model domain confinement due to nested kriging, and low-/high-fidelity EM data blending through co-kriging, enables the construction of reliable surrogates at a fraction of cost required by single-fidelity nested kriging. This is achieved without compromising the predictive power of the model. Our methodology is demonstrated using a miniaturized impedance matching transformer described by fifteen geometry parameters. Setting up the surrogate valid over wide ranges of the operating bandwidth (1.5 GHz to 3.5 GHz for the lower edge, and 4.5 GHz to 6.5 GHz for the upper edge) involves only about three hundred of (equivalent) high-fidelity EM simulations of the transformer circuit.

Electromagnetic (EM)-driven design has become a commonplace of contemporary microwave engineering, primary reasons being reliability and versatility of EM analysis. For certain classes of structures such as miniaturized components, it is a practical necessity as simpler representations (e.g., equivalent networks) are either inadequate or simply not available. On the other hand, simulation-based procedures such as parameter tuning or statistical analysis entail considerable computational expenses. This paper proposes a technique for accelerated design optimization of compact microwave structures. Our methodology involves kriging metamodels constructed using already available designs as well as an iterative correction procedure, feeding the accumulated discrepancies between the target and the actual design objective values back to the metamodel to yield improved predictions. The presented approach is comprehensively validated using a three-section impedance matching transformer and compared to a gradient-based correction scheme. As demonstrated, the designs optimized for wide ranges of the operating bandwidths are obtained at the cost of just a few EM analyzes of the transformer circuit.

An automated EM-based method for efficient spiral inductor design is proposed and implemented using Matlab-driven Sonnet em simulator. In the proposed method, a surrogate model is established as a replacement to the computational expensive EM model utilizing a one-step calibrated circuit model and an iterative response correction process. In the design procedure, only one parameter extraction is performed prior to the iterative response correction in which no further parameter extraction is required. A hexdecagon spiral inductor is designed and optimized automatically following the proposed procedure, the algorithm convergent within 4 iterations to satisfy design specifications. A comparison between the fine model and updated surrogate model is also given as a validation to the reliability of the proposed method.

Noise and color shifts are prone to occur in low-light conditions, which can significantly affect imaging quality. Simply stretching the pixel intensity to improve the illumination level is not able to eliminate noise and color shifts, and it may even lead to artifacts amplification. Various methods have been developed to avoid noise and color shifts in low-light conditions over the past few years. However, most of them may fail to handle different exposure conditions at the same time. In this paper, we propose a novel multi-path convolutional neural network architecture for this task. Luminance and chroma were impacted in two different ways in low-light conditions. By using different well-designed custom networks and loss functions, luminance and chroma can be well restored. Extensive experiments have been performed to demonstrate the superiority of our approach to the state-of-art methods using multiple metrics under different exposure conditions.

This paper presents an efficient method for analyzing the metasurface of varying element sizes or rotate angles. In this method, the characteristic modes (CMs) for metasurface element can be obtained by solving a generalized eigenvalue problem (GEP) based on the mixed potential integral equation (MPIE). Then, by choosing the first several CMs of the isolated reference element with larger mode significance (MS) to construct the entire domain basis functions, the induced current of the metasurface structure can be expanded using the set of entire domain basis functions. By truncating the order of the entire domain basis functions, this method can significantly reduce the number of unknowns and greatly reduce the computational time and memory requirement.

This paper addresses how to develop theory of characteristic modes (TCM) for finite periodic arrays or structures with fully using their periodic property. For ease of reference, the developed method is called periodic characteristic mode analysis (PCMA) method. Its basic idea is that we adopt a small set of specially selected characteristic modes (CMs) of a reference cell (element) of the structure to build up entire-domain basis functions (EDBFs) defined on each cell of the array structure and apply them to represent the characteristic currents (CCs) of the whole structure. Making use of periodicity of the array can greatly reduce the matrix size of the resultant generalized eigenvalue equation and speed up its solution process.

All fiber temperature sensor based on $\mathrm{MoWS}_{2}- \mathrm{rGO}$ coated tapered fiber is demonstrated. The large evanescent field of tapered fiber allows $\mathrm{MoWS}_{2}-\mathrm{rGO}$ coated tapered fiber to absorb the surrounding heat and changes the refractive index of $\mathrm{MoWS}_{2}-\mathrm{rGO}$ coated tapered fiber. The refractive index change is due to thermo-optic effect. When there is a change of surrounding temperature, the refractive index of the coated tapered fiber changes and this subsequently alters the incident light polarization. The sensitivity of the proposed temperature sensor is measured at 0.63°/°C. This is the first demonstration of using $\mathrm{MoWS}_{2}-\mathrm{rGO}$ tapered fiber as temperature sensor.

In this paper, a novel design of compact substrate integrated waveguide (SIW) diplexer with square cavities for C-band applications is presented. This diplexer is working on evanescent-mode propagation and operating below the cut-off frequency of the cavity. First, the filtering response of triangular-slot loaded on one square cavity surface is investigated. This response of the cavity is then applied on two cascaded filters to obtain the diplexer characteristics. To validate the concept, a narrow band filter and diplexer are designed and simulated. The insertion losses at lower and upper passbands centered at 6.16 GHz and 7.72 GHz are obtained as 0.83 dB and 0.77 dB, respectively. The proposed diplexer provides a fractional bandwidth more than 5.1% at each passband with high isolation better than 22 dB. These features show that the proposed diplexer is a suitable candidate for C-band application.

The engineering education and the graduate attributes is increasingly important for university and industry. A teaching exploration regarding course content, teaching mode, teaching team, and diverse evaluation method is presented. A course based on flipped learning combined with project-based learning models are designed to foster students’ ability to study on their own initiative and improve their capability of engineering practice and innovation. The proposed teaching practice is in accord with engineering education accreditation and industrial need.

In this paper, a wideband power divider based on substrate integrated waveguide (SIW) using complementary split-ring resonator (CSRR) and slots is presented. Circular CSRR and two identical slots are engraved in the upper metallic surface of the SIW structure to achieve equal power division over a wideband. A prototype of power divider based on SIW with a 3 dB power division over a wideband is designed, fabricated and tested. Measurement results show that it has return loss greater than 15 dB with insertion loss of 0.89 dB throughout the wideband. The proposed power divider occupies a compact size of 0.950λg× 0.608λg.

Various types of ultrasound transducers have been developed and widely used in biomedical science and industrial testing applications. However, conventional ultrasound transducer is incapable for broad bandwidth ultrasound which provides high spatial resolution imaging. In addition, conventional ultrasound transducers are PZT transducers, which means that these transducers suffer from electromagnetic interference (EMI) in electronically harsh environments. In this study, a Laser induced ultrasonic transducer (LIUT) based on optoacoustic effect is proposed to demonstrate its capability for medical imaging of a gel phantoms. First, the multi-physical field coupling method of electromagnetic-solid-ultrasonic field is deduced, and the ultrasonic field characteristic of LIUT is simulated. And then the LIUT was fabrication by coating the carbon black(CB)-polydimethylsiloxane (PDMS) based polymer composite on the substrate. The characteristics of sound field are verified by experiment and simulation. The amplitude and -6 dB frequency bandwidth of the generated ultrasound were measured to be 2.5MPa and 8MHz, respectively. Finaly, the presented LIUT was applied for magneto-acousto-electrical tomography (MAET) based on ultrasound excitation.

A fabricated microwave component generally requires a post-fabrication tuning process to compensate variations from fabrication process and improve the performance. In this paper, a post-fabrication tuning method based on space mapping and surrogate modeling technique is proposed for tuning fabricated microwave component. The tuning method is presented in detail. Surrogate modeling and parameter extraction process is discussed. Several tuning examples are given to validate the proposed method. By applying the tuning algorithm, we are able to significantly improve the performance to achieve the tuning specifications.

This paper reports on a simplified and cost-efficient approach for realization of air-filled self-suspended rectangular coaxial transmission lines (TLs) by means of polymer-based additive manufacturing. An X-band TL prototype is devised with a wideband filter design approach. The input and output of the TL are connectorized to interface with external circuits. Architectural highlights involving the impedance matching, the assembly of RF connectors, and the sidewall openings will be discussed. The TL is monolithically prototyped by incorporating stereolithography apparatus and copper electroplating techniques, featuring low cost, easy assembly, and free of any fastening element. The implemented TL demonstrates in 8-12.4 GHz an insertion loss of 0.4-1.1 dB (an attenuation factor of 0.06-0.26 dB/cm after the connector loss is deembedded) and a group delay of 0.23-0.32 ns with a fluctuation of around 50 ps.

Unexpected lightning strikes on telecommunication towers may damage sophisticated communication equipment. Thus, it is necessary to predict transient currents in the telecommunication system (TS). Modeling the TS with the tubular tower is an essential but complex work. This paper presents a modeling procedure for the TS with the tubular tower. An efficient meshing scheme is proposed to model a system composed by conductors with both large and small radii. Both skin and proximity effect as well as propagation effect are considered using a partial element equivalent circuit method. The time-domain solution is finally obtained using the extended equivalent circuit. The procedure is verified through numerical comparison. The transient currents in the TS with a 40-m tubular tower are finally analyzed. The simulation shows that more currents will flow in outer-located conductors than other conductors. Particularly, more currents dissipate through the earth bus far from the lightning strike. It provides principles to design effective lightning protection and select appropriate protective devices for TS.

An efficient characteristic mode solver is proposed for the solution of characteristic modes (CMs) of large-scale finite periodic arrays. Firstly, the CMs of an isolated reference element are obtained using the standard characteristic mode solver. Then, by choosing the first several CMs of the isolated reference element with larger mode significance (MS) to construct the entire domain basis functions, the proposed method can dramatically reduce the matrix dimension of the resultant generalized eigenvalue problem governed by the entire array structure, thereby significantly reduce the computational time and memory requirement.

We experimentally demonstrate mode-locked Erbium doped fiber laser (EDFL) by incorporating graphene filled photonic crystal fiber (PCF) into the laser cavity. The 1.5 cm long PCF filled with graphene solution acts as a saturable absorber (SA) to produce pulse with repetition rate of 11.1 MHz and pulse width of 0.88 ps.

In this work, aggressive space mapping (ASM) combined with finite element method (FEM) is applied to a frequency reconfigurable patch antenna design. This technique provides an efficient approach in reducing the computational time for the determination of the RF, DC bias capacitor and DC bias inductor values. The efficiency of aggressive space mapping in the frequency reconfigurable antenna design is very high.

In this paper, an EM-based design approach for designing multi-band filter is proposed. In this method, N multiband resonant units with M resonating nodes (or an M mode resonator) are cascaded to create an N-pole and M-band filter response. Each unit is sequentially designed using the reflected group delay method and cascade space mapping technique. It also provides an efficient approach to reconfiguring a bandpass filter into a multiband filter by adding resonant node to main line resonators to form multiband resonant units. To validate the proposed method, a dual-band filter and tri-band filter are designed in Sonnet em simulator, fabricated and tested. The proposed method results in reliable performance and very good isolations between passbands.

In this paper, an efficient EM-based design method for designing quad-channel diplexer is presented. An analytical method for dualband filter design is presented. In the proposed method, a dualband coupling matrix is directly obtained by adding diagonal rejection resonances and branch coupling elements to a conventional bandpass coupling matrix to produce arbitrary asymmetric bandwidth and arbitrary placed transmission zeros. It also presents a very efficient approach to reconfiguring a simple bandpass filter into a dual-band filter design by adding number of rejection resonators. The design theory is briefly discussed. A quad-channel diplexer including two dual-band filters connected using a T-connection is designed in Sonnet em simulator to validate the proposed method.

The paper proposes an automatic tuning method for three-stub waveguide tuner. A sequential aggressive space mapping technique is proposed to solve the problem of non-uniqueness. Our examples demonstrate accurate and efficient impedance matching of large load variation.