A filter with good impedance matching for both in-band and a wide range of out-of-band is reported in this paper. Thus, the proposed filter offers low reflection for a wide range of frequencies, and it can be called as quasi-reflectionless filter. Also, the proposed filter improves the passband flatness significantly. The quasi-reflectionless filter consists of n-pole conventional U-shaped bandpass filters with absorptive stubs (ABSs) placed at the input and output ports. Each part in the whole filter is individually investigated. The U-shaped resonator is studied first, and then the ABSs are analyzed mathematically and simulated to optimize the attenuation rejection. Several parameters that have an influence on the overall performance are investigated. Different n-pole filters are simulated to simply enhance the out-of-band rejection without affecting the passband response. The filter response is furthermore improved by introducing two transmission zeros using the cross-coupling between the two ABSs. To validate the proposed idea, the 3-pole U-shaped quasi-reflectionless BPF is fabricated on an FR4 substrate at the operating frequency of 3.5 GHz. The filter has measured responses very close to the simulated ones.

The defective array elements which are unavoidable due to the long full-time antenna system operation directly affect its radiation pattern, sidelobe level (SLL), directivity, and the system performance. Therefore, reducing these undesirable effects is a main interest in designing such arrays in practice. In this paper, a partially compensating method based on the genetic optimization algorithm (GA) is proposed to mainly reduce those undesirable effects of the defected elements. Unlike the existing fully compensating methods where all of their active elements were optimized to compensate for the effects of the defected elements, the proposed method optimizes the excitation weights of some optimally selected active-elements. Thus, the whole array elements do not need to be redesigned again as in the case of the fully compensating methods. This greatly simplifies the design implementation of these arrays. Moreover, a very large defective percentage ranging from 5% up to 50% has been considered to demonstrate the effectiveness of the proposed method. Furthermore, the drawback effects of the randomly failing elements at the array center have been highlighted, and some suggestions have been provided.

A compact and broadband stub-loaded dual-mode dipole antenna is proposed. In this paper, the first- and third-order modes are combined to achieve broadband frequency response. To do so, the third-order mode is compressed close to the first-order mode by loading two pairs of identical stubs at an optimal distance from the dipole-centre. Stubs are symmetrically loaded to both the arms of the dipole. Stub parameters such as length, width, and location play a critical role in decreasing the third-order mode frequency. Therefore, a parametric analysis is also carried out to see the effects of variation in the stub parameters. The proposed antenna is fabricated, and measurements are performed to verify the simulation results. A good agreement between the simulated and measured results is obtained.

A novel high performance four-port multiple input multiple output antenna is suggested for 5G application functioning at 3.4 GHz band. The antenna design measures an inclusive volume of 32 mm x 32 mm x 0.8 mm³. The broad frequency bandwidth, excellent gain, decreased interelement gap, and effective isolation within the MIMO components of the proposed system are clearly novel. Each antenna in the four-element MIMO system has been situated orthogonally to the others while maintaining a small size and good result. The antenna has exceptional average total efficiency in the 5G Sub-6 GHz spectrum and is in good agreement with the measured results. It also offers a high realized gain compared to prior MIMO antennas. The antenna has a high impedance matching whose isolation is about -28 dB, computed envelope correlation coefficient smaller than 0.10, channel capacity loss average value less than 0.2\,bits per second per hertz, and the diversity gain about 10 dB. The typical peak realized antenna gain of the offered MIMO antenna is also delivered with a high radiation efficiency at the frequency of 3.4 GHz. The reflection coefficient, mutual coupling, radiation pattern, current distribution, and gain of antennas are all measured and explained. The design has a compact high volume and adequate bandwidth with good accomplished gain making the antenna very strong for 5G application.

A reconfigurable filter integrated single-pole double-throw (SPDT) switch (FIS) based on capacitor loaded ring resonators is presented in this paper. The design incorporates two PIN diodes between two symmetric square ring resonators. The ring resonators can be switched between allstop and bandpass responses, by adjusting the state of the PIN diodes, allowing the corresponding signal path to be in OFF-state with high isolation or ON-state with bandpass filter response. For demonstration, filtering switch is fabricated and measured for 2.4 GHz applications. The measurement results feature an ON-state low insertion loss of -2.1 dB and port-to-port isolation of -50 dB at the band of interest, and good consistency is achieved between simulated and measured results.

In active phased arrays, T/R module performance drifts due to active components' aging and thermal effect. Hence periodic online field calibration is required during the deployment of a radar system. This paper presents an innovative design of a precise and consistent calibration network consisting of a buried leaky coaxial cable (LCX) and a calibration switch network (CSN) for fast periodic field calibration of an active phased array. In the antenna plate, leaky coaxial cables are buried within the wall of the cavity-backed antenna to realize calibration lines. A 1:30 way Wilkinson power divider/combiner is realized as a calibration switching network for simultaneous excitation of multiple calibration lines to characterize multiple radiating elements in the active array. An S-Band (3.3 GHz ± 200 MHz) experimental active array with 64T/R modules is configured and tested in the near-field test range (NFTR) to demonstrate the performance of the proposed calibration network. Simultaneous excitation of multiple radiating elements significantly reduces array calibration time and provides more flexibility to other multifunction radar functions. The availability of multiple receivers and non-overlapping RF beam forming networks in the radar system limits the improvement factor in array calibration time mentioned in this paper.

A Metamaterial Terahertz perfect absorber is proposed in this letter. The structure comprises Vanadium oxide (VO2) resonator hexagonal rings placed on top of a silicon dioxide (SiO2) substrate in a concentric pattern on a metal ground layer, with 1 THz and 6 THz operating frequency. Numerical studies are done by an electromagnetic solver. The results show almost perfect absorption, with 112% average absorption at different incident polarization angles, in the range of 1.64 to 6.1 THz. The optimization is carried out on physical dimensions for maximum absorption results. The proposed design can be used as a highly efficient absorber in applications like solar energy harvesting, cloaking, sensing, imaging technology, and EMC projects.

In this work, a permittivity tuning method using a reconfigurable substrate block is presented. The ratio of two substrate blocks with different permittivities is proved to construct a new permittivity level. This method is validated on a microstrip line, where the theory and simulation show a good agreement with a maximal permittivity calculation difference of less than 5%. In the implementation, only two pieces of substrate blocks with high and low permittivity levels respectively are needed, and it can be utilized for future flexible microwave tuning design.

A normal-vector-field-based block diagonal-preconditioner for the spatial spectral integral method is proposed for an electromagnetic scattering problem with multi-layered medium. This preconditioner has a block-diagonal matrix structure for both 2D TM polarization and 3D cases. Spectral analysis shows that the preconditioned system has a more clustered eigenvalue distribution, compared to the unpreconditioned system. For the cases with high contrast or negative permittivity, numerical experiments illustrate that the preconditioned system requires fewer iterations than the unpreconditioned system. The total computation time is reduced accordingly while the accuracy based on the normal-vector field formulation of the solution is preserved.

Dielectric logging is a valuable tool for locating and developing tight reservoirs, low contrast reservoirs, shale oil and gas reservoirs, and other unconventional oil and gas reservoirs. The processing of multi-frequency and multi-spacing dielectric logging measurements is based on a stable and efficient response computation algorithm. An equivalent computation model for the push-against-hole array dielectric logging tool is established in this paper, and an improved forward method based on the semi-analytical algorithm for dielectric logging response is devised. Thus the calculation speed of each measurement point's dielectric logging response is increased by more than 8 times. Dielectric logging response charts are also constructed, showing amplitude attenuation and phase shift as functions of formation resistivity and relative permittivity at various operating frequencies. The effects of mud cake, invasion, and anisotropy on the response signal are then simulated and evaluated. The findings reveal that: (1) as the high-frequency response changes significantly when the mud cake is thick, to correct the mud cake's influence, the mud cake parameters can be extracted using the high-frequency detection mode. (2) Invasion has a complicated effect on the high-frequency response, and higher resistivity or relative permittivity in the invasion zone can readily lead to an oscillatory nonlinear shift in the response as a function of invasion depth. This means that for high-resistivity and high-permittivity formations, the high-frequency response has a larger sensitivity and a deeper depth of investigation. (3) When the anisotropy coefficient is small, the high-frequency response is preferable for extracting anisotropy; however, as anisotropy increases, the low-frequency response becomes more sensitive to anisotropy than the high-frequency response.

This paper proposes a network system architecture that integrates the operation of two communications technologies of the smart grid, i.e., fiber optics and broadband over power lines, across the same overhead transmission and distribution power grid. This integration brings benefits for the power utilities, telecommunications providers and customers alike. The proposed system architecture is expandable by allowing more communications technologies of the smart grid, such as DSL, fiber, WPAN, WiFi, WiMAX, GSM (4G, 5G) and satellite, to connect. Issues concerning wireless sensor networks, tower-sharing and terabit-class backbone networks are discussed.

In this paper, an analytical model is presented to investigate the resonant characteristics of a graphene rectangular microstrip patch antenna. To take into account the graphene film patch in the full-wave spectral domain technique, surface complex impedance is considered. This impedance is determined by using Kubo formula. A set of roof top sub-domain basis functions are employed to model the current density distribution on the graphene rectangular microstrip patch. The simulation results demonstrate that the designed structure can provide excellent tunable properties in Terahertz frequency region by varying different chemical potentials and relaxation times of graphene film. Variations of dimension of rectangular patch on the resonant frequency and bandwidth of a graphene rectangular microstrip antenna are presented. Finally, numerical results for the dielectric substrates effects on the operating frequencies are also presented. The analysis is validated by comparing the results with a specific example in the literature.

This study presents a quad-band bandpass filter with high selectivity, compact size, and highly independent bands using a folded C-shape resonator, short stub-SIR resonator, and two folded L-shape resonators. The suggested structure consists of two separate filters. The upper filter is made up of a short stub-SIR resonator loaded on a C-shape resonator resonating at 2.59 GHz and 3.5 GHz, respectively. The lower filter is made up of two folded L-shape resonators resonating at 4.89 GHz and 6.15 GHz, respectively. The frequencies at which the filter resonates are designed and arranged with high independence. The proposed filter achieves insertion loss of -2.7 dB, -0.7 dB, 2.3 dB, and -0.4 dB, and return loss of -13.32 dB, -11.03 dB, -9.17 dB, and -17.89 dB, respectively. In addition, eight transmission zeros appeared. The proposed design has a compact size of 0.19λ_g×0.15λ_g and is built on an RO4350B substrate with a dielectric constant of 3.66, loss tangent of 0.0037, and thickness of 0.508 mm. Finally, the suggested filter is intended to be used in 5G mobile communications and international mobile telecommunications services.

For the tracking problem of moving targets by small-scale platforms, this paper firstly proposed a ship target tracking model with joint electromagnetic signals based on point charge theory and point magnetic charge theory. Then, the target tracking was simulated and verified with the progressive update extended Kalman filter algorithm as the filtering unit and the small-scale platform as the sensor-carrying platform. Finally, the laboratory model validation was carried out, and the simulated source experiment and ship model experiment were conducted respectively. The simulation results show that the tracking method with the joint electromagnetic signal can achieve the tracking error less than 5 m in the range of 6 times the ship length. The results of the model experiments further verify the simulation results. When the signal-to-noise ratio is only 5, it can also achieve at least 2 times the ship's length of tracking, which can effectively solve the problem of poor tracking caused by the small size of the sensor carrying platform and the small number of sensors.

In this work, a dual-band compact MIMO antenna for sub-6 GHz 5G applications has been designed, simulated and implemented. Firstly, a single patch antenna was designed and simulated, and its dimensions were adjusted to exhibit a dual band performance at 3.6 GHz and 5.9 GHz. A two-element MIMO structure was then designed with a defected ground structure, and the S-parameters were recorded. The results showed that the designed MIMO antenna exhibited multiband performance at the sub-6G frequency band with almost omnidirectional radiation pattern and acceptable gain. The achieved results are promising, making the proposed antenna a good candidate for 5G applications. The proposed antennas were fabricated, and their basic parameters such as return loss and radiation pattern were tested experimentally and compared with simulation results. An acceptable agreement was achieved between measurement and simulation results.

The wireless power transfer (WPT) system for implantable medical devices has the problem that the output voltage is difficult to adjust stably in real time without using additional composite compensation topology and dual-side communication. A primary side control method of WPT system based on a phase shifted full bridge inverter and continuous control set model predictive control (MPC) is proposed. First, the series-series (SS) structure parameters and fundamental harmonic analysis (FHA) are used to derive the estimated value of the output voltage and establish the output voltage prediction model of the system. Then, to obtain the best response of the system, the optimization problem in the controller is transformed into the problem of solving the minimum value of the cost function, and the optimal control variable is obtained limited below the gradient descent method. Simulated and experimental results show that the control system works at a frequency of 200 kHz to realize real-time voltage adjustment, and the steady-state error is within 2%. Compared with the traditional method, the method reduces the adjustment time by 5-10 ms, and voltage overshoot is reduced by 5.3-6.7% when interference factors are dealt with such as load interference and mutual inductance. The proposed method improves the performance of SS compensated WPT systems to be more suitable for the applications that require compact and light weight receiver. It provides an effective method to realize the real-time regulation of the system output voltage.

This study aims to develop and evaluate the multibeam one-third Radial Line Slot Array (RLSA) antennas. The various techniques used include: a) slot implementation on the background surface for the design of multibeam, b) cutting the full circle of RLSAs for the simplification of the antenna size, and c) slot deletion for the formation of bandwidth. Approximately 40 multibeam one-third RLSA models were designed and simulated, with the best being fabricated and measured to verify the simulation. The results showed that the antenna had symmetrical beams regarding the gain, direction, and beamwidth at 9 dBi, 20 and 160°, as well as 38°, respectively. The antenna also had a low reflection of -22 dB at the centre frequency of 5.8 GHz, with a broad bandwidth of approximately 1.2 GHz, which was highly sufficient for Wi-Fi application. The gain of 9 dBi was 3 dB lower than that of a simulated single-beam antenna, which was suitable for the theory of splitting. Based on these findings, the agreement between measurement and simulation verified the design of the antenna.

In this paper, two G-band sub-harmonic mixers based on planar antiparallel Schottky diodes are presented. The proposed type-I mixer is designed using the conversional THz Schottky diode mixer circuit architecture. In order to broaden the bandwidth further, a novel type-II sub-harmonic mixer based on new circuit topology is proposed. In type-II mixer, an antiparallel Schottky diodes chip is directly connected with metal ground using silver epoxy. The simulated results show that single-sideband (SSB) conversion loss of type-II mixer is less than 10 dB in the frequency range of 160-194.8 GHz. For validation, the type-I mixer is fabricated and tested. Measurement results show that single-sideband conversion loss of type-I mixer is basically less than 10.7 dB in the frequency range of 166-190 GHz.

Sensing is a key basis for building an intelligent environment. Using channel state information (CSI) from the IEEE 802.11 physical layer in the wireless local access networks, the CSIbased device-free sensing technique has become very promising to the current sensing solutions because of its non-invasion of privacy, non-contact, easy deployment, and low cost. In recent years, the integrated communication and sensing (ICAS) technology has become one of the popular research topics in both wireless communications and computer areas. Given the fruitful advancements of ICAS, it is essential to review these advancements to synthesize and give previous research experiences and references to aid the development of relevant research fields and real-world applications. Motivated by this, this paper aims to provide a comprehensive survey of CSI-based sensing techniques. This study categorizes the surveyed works into model-based methods, data-based methods, and model-data hybrid-driven methods. Some important physical models and machine learning algorithms are also introduced. The sensing functions are classified into detection, estimation, and recognition according to specific application scenarios. Furthermore, future directions and challenges are discussed.

In this paper, a flexible compact Jeans gap filled metamaterial inspired antenna is proposed to operate at 2.4 GHz in the Industrial Scientific and Medical (ISM) band. This designed antenna is flexible having size of about 27×23 mm² with substrate of thickness 0.3 mm. The proposed antenna comprises two complementary split ring resonators at ground plane and one circular ring and complementary rectangular split ring resonator. The top patch consists of two rectangular split ring resonators etched inside the rectangular patch. The use of SRR and CSRR on top and bottom of patch has helped to reduce the size of antenna along with maintaining performance of antenna. Further enhancements are done to make it jeans gap filled antenna with jeans filled between main patch and superstrate. The superstrate top patch consists of a square EBG structure. The simulation results have shown an increase in return loss due to the use of square EBG structure on superstrate. The simulated directivity obtained on antenna is 2.0775 dB. The measured and simulated results are in a good agreement. The motivation of this work is to design a compact metamaterial based antenna for wireless body area network with gap coupled jeans material to nullify effects of human body. Effects of air gap coupled and jeans gap coupled are analyzed in terms of performance. While the final antenna (Antenna-4) is designed, several iterations are tried to optimize and maintain good performance. Step 1 (Antenna-1) consists of two complementary split ring resonators along with a circular ring placed in ground plane with thickness of polyamide substrate as 0.3 mm. Step 2 (Antenna-2) consists of two split ring resonators along with a circular ring placed in ground plane. An air gap coupled superstrate is designed having gap between main patch and superstrate as 1 mm. Step 3 (Antenna-3) has the same configuration as Antenna-2, and the only difference is the air gap between main patch and superstrate which is replaced by jeans material. Step 4 (Antenna-4) is the final designed antenna with miniaturized size of 27×23 mm² as compared with previous antenna configurations. This research work has identified the challenges involved for designing an antenna in a wireless body area network. Practical aspect of design needs to consider: a) Bending effect on performance as movement and physiological changes might affect the performance. b) Performance degrades when antenna comes in contact with human body. Bending Effect: This work has also analyzed effect of bending on return loss. For final designed antenna (Antenna-4) maximum bending up to bend 30˚ is possible. Further bending would break the substrate. After maximum bending, the measured return loss is about -16.7071 dB at 2.28 GHz. Body area network: The designed final antenna (Antenna-4) is tested on different parts of human body such as human-arm and leg. No major difference is seen on return loss when it is tested on different parts of body. The designed final antenna (Antenna-4) is tested on direct contact with human-arm as well as with different cloths (cotton jeans, cotton, curtain cloth, floor cloth, polyester and Turkish cloth) having different permittivities with the distance between cloth and antenna as 0 cm and 1 cm. Wearable antennas should be carefully constructed to avoid causing harm to the human body when being worn. The Low Specific Absorption Rate is one of the criteria that should be considered while developing a wearable antenna. The maximum allowable SAR limit is 1.6 W/kg. The specific absorption rate for Antenna-4 is 0.2 W/kg when input power is 1 watt and is 0.036 W/kg when input power is 100 milli watt. The results obtained show that the proposed antenna is both safe and acceptable for use in compliance with the World Health Organization's ICNIRP requirements.