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The purpose of this paper is to clarify the method of using RF impedance changes as an early indicator of degradation of solder joint. It proposes the mode of crack propagation in solder joint and outlines why RF impedance analysis can be capable of detecting small cracks. The study aims to show the potential of RF impedance analysis as a prognostic tool that can provide advanced warning of impending failures of solder joint.

In this paper, the mode of crack propagation in solder joint was studied to show why RF impedance analysis could be capable of detecting small cracks. A real simple impedance‐controlled test vehicle was developed to allow RF impedance and DC resistance measurements to monitor solder joint degradation. The influence of crack length on RF impedance was evaluated by high frequency structure simulator (HFSS) simulation for the first time.

The paper demonstrates that RF resistance can respond to an open state of a solder joint as well as DC resistance. Furthermore, RF impedance can monitor partial degradation of solder joints, while the DC resistance cannot do it. In addition, time‐domain reflection coefficient is found to be more useful than RF impedance in detecting solder joint degradation. The HFSS simulation results show that even very slight physical degradation of solder joints can be detected using RF impedance analysis.

In this paper, HFSS simulation is used for the first time to evaluate the influence of crack length on RF impedance.

The purpose of this paper is to design and develop half-mode substrate-integrated waveguide (HMSIW)- and quarter-mode substrate-integrated waveguide (QMSIW)-based antennas for wireless communication application. The developed antennas offer advantages in terms of compactness, high gain and better isolation between the ports.

Initially, the tri-band substrate-integrated waveguide-based antenna is designed using a slot on the ground plane. Then, the same structure has been bisected into two parts for the development of the HMSIW structure. Again the concept of the slot is used for the realization of a dual-band antenna. QMSIW-based structure is designed with further dividing HMSIW structure into two parts. Simulation has been carried out with the use of a high-frequency structure simulator (HFSS) software, which used a finite element-based solver for the full-wave analysis.

The proposed HMSIW-based dual-band antenna resonates at two different frequencies, namely, 5.81 GHz with 4.5 dBi gain and at 6.19 GHz with 6.8 dBi gain. Isolation between two ports is 20 dB. The overall dimensions of the proposed model are 0.39 λ × 0.39 λ. Similarly, QMSIW-based antenna is resonated at 5.66 GHz of the frequency with the 3 dBi gain. Frequency tuning is also carried out with the change in the slot dimension to use the proposed antenna in various C (4–8 GHz) band applications.

The proposed antennas can use C band wireless frequency application. The proposed structure provides better performance in terms of isolation between the ports, small size, high front-to-back ratio and higher gain. It is fabricated for the proof of concept with the RT Duroid 5880 substrate material having a 2.2 permittivity. Measured results show a similar kind of performance as a simulated one.

Purpose of this study is to design a compact gap coupled anchor shape patch antenna for wireless local area network/high performance radio local area network and worldwide interoperability for microwave access applications.

An anchor shape microstrip antenna is conceived, designed, simulated and measured. The anchor shape antenna is transformed to its rectangular equivalent by conserving the patch area. Modeling and simulation of the antenna is performed by Ansys high frequency structure simulator (HFSS) electromagnetic solver based on the concept of finite element method. The simulated results are experimentally verified by using Agilent E5071C vector network analyzer. Theoretical analysis of an electromagnetically gap coupled anchor shape microstrip patch antenna has been performed by obtaining the lumped element equivalent of the transformed antenna.

The proposed antenna has a compact conducting patch of dimension 0.26λ × 0.12λ mm² (λ is calculated at lower resonating frequency of 3.56 GHz) with impedance bandwidths of 100 and 140 MHz and antenna gains of 1.91 and 3.04 dB at lower resonating frequency of 3.56 GHz and upper resonating frequency of 5.4 GHz, with omni-directional radiation pattern.

In literature, one does not encounter anchor shape antenna using the concept of gap coupling and parasitic patches. The design has been optimized for wireless local area network/worldwide interoperability for microwave access applications with a relatively low patch area (291.12 mm²) as compared to other reported antennas for wireless local area network/worldwide interoperability for microwave access applications. Transformed antenna and the actual experimental antenna behavior varies, but the resonant frequencies of the transformed antenna as observed by theoretical analysis and simulated results (by high frequency structure simulator) are reasonably close, and the percentage difference between the resonant frequencies (both at lower and upper bands) is within the permissible limit of 1-2.5 per cent. Results confirm the theoretical proposition of transformation of shapes in antenna design, which allows a designer to adapt the design shape according to the application.

The purpose of this paper is to build a neural network (NN) inverse model for the multi-band unequal-power Wilkinson power divider (WPD). Because closed-form expressions of the inverse input–output relationship do not exist, the NN becomes an appropriate choice, because it can be trained to learn from the data in inverse modeling. The design parameters of WPD are the characteristic impedances, lengths of the transmission line sections and the isolation resistors. The design equations used to train the NN inverse model are based on the even–odd mode analysis.

An inverse model of a multi-band unequal WPD using NNs is presented. In inverse modeling of a microwave component, the inputs to the model are the required electrical parameters such as reflection coefficients, and the outputs of the model are the geometrical or the physical parameters.

For verification purposes, a quad-band WPD and a penta-band WPD are designed. The results of the full-wave simulations verify the validity of the design procedure. The resulting NN model outperforms traditional time-consuming optimization procedures in terms of computation time with acceptable accuracy. The designed WPDs using NN are implemented by microstrip lines and verified by using full-wave analysis based on high-frequency structure simulator (HFSS). The results of the microstrip WPDs have good agreements with the corresponding results obtained by using ideal transmission line sections.

The associated time-consuming procedure and computational burden in realizing WPD through optimization are major disadvantages; needless to mention the substantial increase in optimization time because of the multi-band design. NNs are one of the best candidates in addressing the abovementioned challenges, owing to their ability to process the interrelation between electrical and geometrical/physical characteristics of the WPD in a superfast manner.

The purpose of this paper is to present the results of a particle swarm optimization (PSO) method applied in the design of a square-loop frequency selective surface (FSS) via the equivalent circuit model (ECM), considering the dielectric effective permittivity as a variable in the optimization problem.

In the optimization process considered, besides the FSS square loop geometric parameters, the thickness and relative permittivity of dielectric material used as support are included as variables in the search space, using for this a model of dielectric effective permittivity introduced by the authors in a previous work.

Square loops were designed and the obtained results were compared with designs reported in literature for applications in wireless local area network and long-term evolution 4G systems. The low computational cost is remarkable as well as the acceptable accuracy obtained with the proposed approach. The PSO method results were implemented with the ECM and compared with those obtained via Ansys – high frequency structure simulator commercial software simulations.

The lack of a model of dielectric effective permittivity for the ECM causes a restricted search space in the stochastic FSS design process limited to only geometric parameters, as it is reported in the available literature. The proposed approach simplifies and makes more flexible the design process, and allows guiding the FSS design to unit cell surface and/or dielectric thickness of small dimensions.

This paper aims to present the design, fabrication and analysis of a wideband, enhanced gain 1 × 2 patch antenna array with a simple profile structure to meet the desired antenna traits, such as wide bandwidth, high gain and directional patterns expected for the upcoming fifth-generation (5G) wireless applications in the millimeter wave band. To enhance these parameters (bandwidth and gain), a new antenna geometry by using a T-junction power divider is presented.

The theory behind this paper is connected with advancements in the 5G communications related to antennas. The methodology used in this work is to design a high gain array antenna and to identify the best possible power divider to deliver the power in an optimized way. The design methodology adopts several steps like the selection of proper substrate material as per the design specification, size of the antenna as per the frequency of operation and application-specific environment condition. The simulation has been performed on the designed antenna in the electromagnetic simulation tool (high-frequency structure simulator [HFSS]), and optimization has been done with parametric analysis, and then the final array antenna model is proposed. The proposed array contains 2-patch elements excited by one port adapted to 50 Ω through a T-junction power divider. The 1 × 2 array configuration with the suggested geometry helps to improve the overall gain of the antenna, and the implementation of the T-junction power divider provides enhanced bandwidth. The proposed array designed using a 1.6 mm thick flame retardant substrate occupies a compact area of 14 × 12.14 mm².

The prototype of the array antenna is fabricated and measured to validate the design concept. A good agreement has been reached between the measured and simulated antenna parameters. The measured results confirm its wideband and high gain characteristics, covering 24.77–28.80 GHz for S₁₁= –10 dB with a peak gain of about 15.16 dB at 27.65 GHz.

The proposed antenna covers the bandwidth requirements of the 26 GHz n258 band (24.25–27.50 GHz) to be deployed in the UK and Europe. The suggested antenna structure also covers the federal communications commission (FCC)-regulated 28 GHz n261 band (27.5–28.35 GHz) to be deployed in America and Canada. The low profile, compact size, simple structure, wide bandwidth, high gain and desired directional radiation patterns confirm the applicability of the suggested array antenna for the upcoming 5 G wireless systems.

This paper aims to present, design and implement a novel half-mode substrate integrated waveguide (HMSIW)-based narrow bandpass filter, which offers advantages like low insertion loss, compact size and high selectivity. Proposed filter will be used in the K-band automotive radar application.

The filtering response in the proposed design is achieved by inserting inductive posts in the HMSIW cavity. Ansoft high frequency structure Simulator (HFSS) is used for the simulation of the proposed structure, which is a three-dimensional full-wave solver using the finite element method (FEM). The proposed filter is fabricated on the dielectric material RT duroid 5,880 with the dielectric constant ɛ_r = 2.2, dissipation factor t and = 4 × 10^–4 and height h = 0.508 mm.

Frequency tuning is also carried out by changing the lateral distance between two inductive posts. Moreover, a comparison of the proposed structure with the previously published work is presented. Proposed method provides the unique advantages such as low insertion loss, high selectivity and compact in size.

Indigenous method has been used for the development of the filter. Proposed filter will be used in transmitter subsystem of the K-band radar system operating at the center frequency of 11.2 GHz. Measurement results are well-matched with the simulated one. Obtained measured result shows return loss of 20.39 dB and insertion loss of 1.59 dB with 3 dB fractional bandwidth (FBW) of 2.58% at the center frequency of 11.2 GHz.

Three‐dimensional photonic bandgap (PBG) structures using alumina (Al₂O₃) as the high permittivity material were modeled and then the structures were fabricated by Fused Deposition of Multi‐materials (FDMM) technology. A finite element method and a real‐time electromagnetic wave propagation software were used to simulate and design the layered PBG structures for applications in the microwave frequency range. The modeling predicted a 3‐D photonic bandgap in the 16.5–23.5 GHz range. FDMM provides a computer‐controlled process to generate 3‐D structures, allowing high fabrication flexibility and efficiency. Electromagnetic measurements displayed the presence of a bandgap between 17.1–23.3 GHz, showing a good agreement with the predicted values. These PBG structures are potential candidates for applications in advanced communication systems.

The purpose of this paper is to develop a novel totally passive, wireless temperature sensor tag based on ultra high-frequency (UHF) radio frequency identification (RFID) technology. The temperature-sensing functionality is enabled by using distilled water embedded in the tag antenna substrate. The novel sensor tag is designed to provide wireless temperature readings comparable to a commercial thermocouple thermometer even in environments with high levels of interference, such as reflections. The structure of the novel sensor tag is aimed to increase its usability by minimizing user-created errors and to simplify the measurement procedure.

The sensor tag is based on a dual port sensing concept in which two ports are used to obtain sensor readings. By utilizing two ports instead of one, the effects of environmental interference, tag-reader antenna orientation and distance can be effectively minimized. Two alternative methods of acquiring the sensor reading from the operating characteristics of the two ports are presented and discussed.

Temperature measurements in practical scenarios show that by utilizing the dual port sensing concept, the developed tag produces temperature readings wirelessly which are comparable to readings from a commercial thermocouple thermometer.

The concept of dual port sensing was shown and two alternative methods on extracting sensor readings from the differences in the port operating characteristics were introduced and discussed. In this paper, the dual port sensing concept is utilized in creating a temperature sensor tag; however, the same concept can be utilized in a variety of passive wireless sensors based on UHF RFID technology. This enables a new approach in designing accurate, easy to use and easily integrable passive sensors. The dual port sensing concept is in its early stages of development; its accuracy could be improved by developing more advanced data post-processing techniques.

The accuracy of a passive dual port UHF RFID-enabled temperature sensor tag is proven to be sufficient in many applications. This indicates that other sensor types utilizing the dual port sensing concept can reach high levels of accuracy as well. Furthermore, the passive RFID-enabled sensors based on the dual port sensing concept are superior in usability versus sensor tags equipped only with a single port. Therefore, dual port sensing concept in passive UHF RFID-enabled sensor tags could make such sensors more attractive commercially and lead to truly widespread ubiquitous sensing and computing.

This paper presents a novel passive, wireless temperature sensor tag for UHF RFID systems. The sensor tag utilizes a new structure which allows tight integration of two ports and two tag antennas. The accuracy of the developed tag is confirmed throughout measurements and it is found comparable to the accuracy of commercial thermometers in practical measurement scenarios. Moreover, the paper presents a dual port sensing concept and two readout methods based on the concept which are aimed to increase the accuracy and usability of all kinds of UHF RFID-enabled sensor tags.

This paper aims to present the simulation, fabrication and testing of a novel ultra-wide band (UWB) band-pass filters (BPFs) with better transmission and rejection characteristics on a low-loss Taconic substrate and analyze using the coupled theory of resonators for UWB range covering L, S, C and X bands for radars, global positioning system (GPS) and satellite communication applications.

The filter is designed with a bent coupled transmission line on the top copper layer. Defected ground structures (DGSs) like complementary split ring resonators (CSRRs), V-shaped resonators, rectangular slots and quad circle slots (positioned inwards and outwards) are etched in the ground layer of the filter. The circular orientation of V-shaped resonators adds compactness when linearly placed. By arranging the quad circle slots outwards and inwards at the corner and core of the ground plane, respectively, two filters (Filters I and II) are designed, fabricated and measured. These two filters feature a quasi-elliptic response with transmission zeros (TZs) on either side of the bandpass response, making it highly selective and reflection poles (RPs), resulting in a low-loss filter response. The transmission line model and coupled line theory are implemented to analyze the proposed filters.

Two filters by placing the quad circle slots outwards (Filter I) and inwards (Filter II) were designed, fabricated and tested. The fabricated model (Filter I) provides transmission with a maximum insertion loss of 2.65 dB from 1.5 GHz to 9.2 GHz. Four TZs and five RPs are observed in the frequency response. The lower and upper stopband band width (BW) of the measured Filter I are 1.2 GHz and 5.5 GHz of upper stopband BW with rejection level greater than 10 dB, respectively. Filter II (inward quad circle slots) operates from 1.4 GHz to 9.05 GHz with 1.65 dB maximum insertion loss inside the passband with four TZs and four RPs, which, in turn, enhances the filter characteristics in terms of selectivity, flatness and stopband. Moreover, 1 GHz BW of lower and upper stopbands are observed. Thus, the fabricated filters (Filters I and II) are therefore evaluated, and the outcomes show good agreement with the electromagnetic simulation response.

The limitation of this work is the back radiation caused by DGS, which can be eradicated by placing the filter in the cavity and retaining its performance.

The proposed UWB BPFs with novel resonators find their role in the UWB range covering L, S, C and X bands for radars, GPS and satellite communication applications.

To the best of the authors’ knowledge, for the first time, the authors develop a compact UWB BPFs (Filters I and II) with BW greater than 7.5 GHz by combining reformed coupled lines and DGS resonators (CSRRs, V-shaped resonators [modified hairpin resonators], rectangular slots and quad circle slots [inwards and outwards]) for radars, GPS and satellite communication applications.