Space borne accurate emitter localization has become an important and indispensable part of electronic warfare (EW) systems. In this paper, a system-level approach to design space borne receiver for accurate localization of long range co-channel radars (e.g. a network of similar surveillance radars) is presented. Due to the wide frequency range of modern radar signals, the receiver should have wide instantaneous bandwidth and requires high sampling rate analog-to-digital converters (ADCs). To address this issue, we propose a receiver structure with an appropriate sub-Nyquist sampling scheme and fast sparse recovery algorithm. The proposed sub-Nyquist sampler employs a three dimensional uniform linear array (ULA), followed by a modulated wideband converter (MWC). To accurately estimate the location of the co-channel radars from sub-Nyquist samples, a novel quad-tree variational Bayesian expectation maximization (QVBEM) algorithm is proposed. The QVBEM algorithm minimizes the computational load and grid mismatch error by iteratively narrowing the search area. This is done by smart grid refinement around radars' locations. To evaluate the performance of the proposed receiver, location finding of pulsed radars is studied through numerical simulations in various scenarios. The results show that the proposed QVBEM method has a significantly lower estimation error than conventional deterministic and Bayesian approaches, with a reasonably computational complexity.

A bearingless switched reluctance motor (BSRM) has the same body structure as a switched reluctance motor (SRM), but the winding method is different. The accurate analysis of thermal characteristics is especially important for the service life and safety performance of the two motors. According to the initial design parameters, the initial size calculation equations of SRM and BSRM are given, and the ontology design parameters are obtained according to the same design goal. The two-dimensional finite element model is established, and the stator rotor iron loss is analyzed. The distribution characteristics of iron loss of SRM and BSRM are summarized. Secondly, the three-temperature field model of the motor is built, and the reasonable boundary conditions are set. The temperature distribution law of the two motors is analyzed. It is concluded that the BSRM components have lower loss and lower temperature rise under the same design target.

In this paper, the design of a miniature antenna dedicated to be implanted in a small animal and intended to work in the European UHF RFID (865-868 MHz) band is presented. One of the goals of this work is the miniaturization of the radiating element while preserving its efficiency to allow a reliable communication between an external interrogating reader and the implanted device. The radiating element is a small rectangular loop antenna associated with a dipole allowing impedance matching. The antenna has dimensions of 2.4 mm x 25.4 mm x 0.5 mm and integrates an Impinj Monza 4 chip presenting an impedance of 5.5-j74 Ohms at 868 MHz. The antenna is designed and optimized by using the ANSYS HFSS software. The obtained results show a simulated radiation efficiency of 0.7% and simulated total gain of -17.5 dBi. A prototype is realized, and RSSI measurements have demonstrated the possibility of reliable wireless communications between the implanted antenna and an external reader. In addition, Specific Absorption Rate (SAR) calculation indicates that this implanted antenna meets the required safety regulations.

In this paper, a new type of single loaded broadband double-whip antenna is designed for very high frequency (VHF). The simulation model by moment method is established to analyze the influence of antenna spacing on the performance of a double-whip antenna. The location of antenna loading and the parameters of loading network and broadband matching network are optimized by grasshopper optimization algorithm, and the voltage standing wave ratio (VSWR), gain, pattern and roundness of double-whip antenna are calculated. In fact, a fabricated prototype of the proposed antenna is realized. The measured VSWR is consistent with the simulation results, which is less than 3 at all frequencies, with an average value of 1.89; the maximum directional gain is greater than 2.01 dB, with a maximum of 6.44 dB and average value of 3.79 dB; the minimum roundness of antenna gain is 0.03 dB (at 30 MHz), and the maximum roundness is 1.87 dB (at 300 MHz); the efficiency is all over 51%, with a maximum value of 79% and an average value of 60.71%.

In this paper, a novel semi-circular ultra wide-band antenna inspired by a complementary split ring resonator for enhancement of bandwidth and a frequency selective surface reflector for gain enhancement is proposed for broadband applications. Initially, an ultra wide-band antenna employing a pair of L-shaped resonators and complementary split ring resonators is proposed which provides a wide impedance bandwidth of 130.3% from 3.16 to 15 GHz with -10 dB return loss. Finally, a frequency selective surface reflector is employed below the suggested ultra wide-band antenna to enhance the gain. The dimensions of the coplanar waveguide fed ultra wide-band antenna are 35 × 30 × 1.6 mm³ and those of the ultra wide-band antenna with a frequency selective surface reflector, which consists of 10 × 10 array of elements located at a distance of 17 mm below the proposed antenna, are 53.15 × 53.15 × 1.6 mm³. A parametric analysis of substrate dimensions of ultra wide-band antenna and the distance between ultra wide-band antenna and frequency selective surface reflector is performed. The average peak gain of the proposed antenna increases from 4.9 dB to 10.9 dB, which operates at 3.79 GHz, 4.44 GHz, 7.89 GHz, 9.01 GHZ, and 11.15 GHz proposed for broadband applications. With the help of ANSYS, the signal correlation of the proposed antenna is analysed by time domain analysis using similar antennas in face-to-face and side-to-side scenarios. The simulated results of the proposed model are in correlation with experimental ones of the prototype model.

This work presents the design and simulation of a beam scanning antenna at 300 GHz using Luneburglens for 5th generation communication applications or beyond. The basic antenna consists of a highly directional Yagi-Uda antenna with lens shaped configuration (substrate lens antenna - SLA) and designed using multiple parallel elements such as one reflector and one driven element with 6 directors. The SLA is focused by Luneburg lens, which is modeled using a unique foam material AirexR82 with relative dielectric constant of 1.12, and it is pressed to realize different dielectric constants in order to obey the index law inside the lens. The final nine - element array of SLA integrated with Luneburg lens provides a 50% increase in bandwidth compared with conventional Yagi-Uda antenna along with an increase in the gain of 31.3% compared with single SLA. The designed model can achieve a beam scan coverage up to 146˚ with a maximum gain of 17.1 dBi and an estimated efficiency of 92.9%. The beam scanning antenna provides a wide bandwidth of 83 GHz starting from 289 GHz to 372 GHz. The analysis of the proposed antenna is done in CST suite and is validated using HFSS software.

In this paper, the required array patterns with controlled nulls are obtained by optimizing only the excitation phases of a small number of elements on both sides of the array. A genetic algorithm is used to appropriately find which elements of the array to be optimized and also to find the required number of the excitation phases. The performance of the proposed phase-only method is compared with some other exciting methods, and it is found to be competitive, fulfill all the desired radiation characteristics, and represent a good solution for interference mitigation. Moreover, the proposed phase-only array is designed and validated under realistic electromagnetic effects using CST full wave modeling. Experimental results are found in a good agreement with the theoretical ones and show realistic array patterns with accurate nulls.

An eight-port antenna system for fifth-generation (5G) multi-input multi-output (MIMO) mobile communication in smartphones is proposed, working in 3.5 GHz frequency band (3400-3600 MHz) and 5 GHz frequency band (4800-5100 MHz). The presented eight-port antenna array consists of four vertical structure antennas placed at four corners and four horizontal structure antennas etched along the two long sides of the circuit board. The height of vertical structure is only 4 mm, which is suitable for ultra-thin smartphones. The design of eight-port antenna array was fabricated and measured. According to the test results, an ideal impedance matching (superior to 10 dB), preeminent isolation (superior to 17 dB) and excellent efficiency (superior to 61%) are obtained over the 3.5 GHz frequency band and 5 GHz frequency band. In order to evaluate MIMO performance, the ergodic channel capacities and envelope correlation coefficients (ECC) are also investigated.

A miniaturized multilayer tunable super wideband (SWB) bandpass filter (BPF) is presented based on a microstrip structure. A pair of transmission line is coupled with the aid of three defected ground structures (DGS) at ground to improve the coupling and provide ultra wide band pass response. One of the transmission line is placed at the top plane of the upper layer, and the other transmission line is at bottom plane of the lower layer with defected microstrip structures (DMS) to improve the return loss. Bandwidth can be tuned by properly selecting the resonator size. Circuit model for the microstrip resonator and mathematical analysis are given and studied. Finally, the proposed vertical connection with slotline structures and a three pole UWB filter is designed, simulated, fabricated, and the results are well vindicated by an exemplary circuit centered at 6.5 GHz with the measured fractional bandwidth (FBW) of 135%. The filter exhibits a constant group delay of 0.3 ns in the pass band and the size of the resonator is 13.67 mm×17.58 mm×3.2 mm.

In this paper, we develop a multi-band circularly polarized planar antenna operating at 28 GHz and 60 GHz for 5G and WiGig applications. The antenna is composed of a square slot antenna fed by a proximity coupled microstrip line and loaded by grounded square loop and three tilted angle strips. Grounded square patch introduces resonance at 60 GHz frequency while the strips introduce resonances at 28 GHz. The square slot is designed as a wide-band antenna which can support these two resonances.

A wideband patch array antenna with dual sense circular polarization (CP) is investigated in this paper. Four rotated hexagonal patches are sequentially distributed on the upper surface of substrate 1 to form a patch array. In order to widen impedance bandwidth, an annular feeding network with four rectangular branches is designed. At the bottom of the antenna, two orthogonally placed microstrip baluns are introduced to obtain the characteristics of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Meanwhile, four coaxial probes, passing through substrate 2 and substrate 3, are used to transmit the feeding signal between microstrip balun and the annual feeding network. The proposed patch array antenna is fabricated for verifying the feature of wideband and dual circular polarizations. The measured results show that the antenna has an impedance bandwidths of 70.2% (1.72-3.58 GHz) with an axial ratio (AR) bandwidth of 61% (1.85-3.48 GHz) and over 6.2 dBi gain at two ports. Moreover, the measured port isolation remains below -15 dB over the entire impedance bandwidth, and the measured radiation patterns with excellent directionality and symmetry at two ports indicate that the proposed antenna can be used for wireless applications.

Circular polarization is manifested by means of truncations on basic circular radiating patch with precisely designed asymmetric feed. The proposed truncated circular microstrip antenna (TCMA) yields impedance bandwidth (IBW) of 7.6 GHz, almost covering the FCC approved ultra wideband (UWB) frequency and 3-dB axial ratio bandwidth (ARBW) of 5.05 GHz spreading over two bands, enabling the antenna to be used for multiple applications in ultra wideband frequency range. A peak gain of 5.73 dBi is documented at 5 GHz which is within the circular polarization (CP) band. This single feed antenna is very simple to design and compact in size.

In this paper, an inkjet printed slotted disc monopole antenna is designed, printed and analyzed at 2.45 GHz ISM band on a polyethylene terephthalate (PET) substrate for early detection of brain stroke. PET is used as a substrate due to its low loss tangent, flexible, and moisture-resistant properties. By the implementation of slotting method, the size of this antenna is reduced to 40×38 mm². The printed antenna exhibits 480 MHz (19.55%) bandwidth ranging from 2.25 GHz to 2.73 GHz frequency. It shows a radiation efficiency of 99% with a realized gain of 2.78 dB at 2.45 GHz frequency. The Monostatic Radar (MR) approach is considered to detect brain stroke by analyzing the variations in reflected signals from the head model with and without stroke. The maximum specific absorption rate (SAR) distribution at 2.45 GHz frequency is calculated. The compact size and flexible properties make this monopole antenna suitable for early detection of brain stroke.

A compact microstrip fed dual polarized Ultra Wide Band (UWB) monopole Multiple Input Multiple Output (MIMO) antenna for access point application in Wireless Body Area Networks (WBAN) is proposed. The antenna is elliptically polarized in the 6 to 10.6 GHz band. The proposed structure possesses high isolation with the introduction of Modified Serpentine Structure (MSS) that behaves as a decoupling unit (DU). To further reduce the coupling and to improve the impedance bandwidth, an Electromagnetic Band Gap (EBG) structure is introduced. The proposed antenna has a wide impedance bandwidth with S₁₁ < -10 dB in the UWB from 3.1-10.6 GHz and has a high isolation S₂₁ < -25 dB. The antenna has a fractional bandwidth of 106%. The radiation pattern of the antenna is omnidirectional. The Envelope Correlation Coefficient (ECC) is equal to zero, and the capacity loss is 0.264 which proves the diversity characteristics of the proposed antenna.

In this paper, a novel dielectric resonator antenna has been numerically simulated and experimentally demonstrated. The proposed design, comprising an Indium Tin Oxide (ITO) coated glass slide placed on a microstrip transmission line, is intended for WLAN and Wi-Max applications. The antenna shows a maximum bandwidth of 2.15-7.65 GHz and 10.36-11.78 GHz and a gain ranging from 2.21 to 6.44 dB. The novelty of the design lies in the use of ITO coating on glass to enhance as well as regulate the antenna bandwidth. Parametric variations have been investigated to analyse the topology for understanding the effect of the design parameters on gain, bandwidth, and reflection coefficient. A prototype has also been fabricated, where different ITO sheets have been mounted to measure the response. The proposed geometry has been found to be better and competent enough with respect to antenna parameters than existing Ultrawide Band antennas.

This paper describes the synthesis of a bandpass filter to achieve high selectivity and rejection properties using a new class of filter functions called chained-elliptic function filters. Chained-elliptic filters have higher selectivity than Chebyshev function filters and have the property of sensitivity to manufacturing tolerance reduction in chained-function filters. The proposed design has high selectivity and reduced sensitivity, enabling easier and faster filter fabrication. The characteristic polynomials of chained-elliptic function filters are derived through chaining elliptic filtering function and extracted to form a coupling matrix of the bandpass filter. The novel transfer polynomials are given in detail, and a thorough investigation of the filter characteristics is performed. A theoretical comparison with Chebyshev and elliptic filters of the same order is performed to ascertain the demonstrated advantages of this proposed filter class. A high frequency narrow-band fourth-order chained-elliptic function waveguide filter centred at 28 GHz with a fractional bandwidth of 1.61% is fabricated to validate the proposed design concept. A good match among the measured, simulated and ideal filter responses is shown where the overall responses between measurement and simulation have a difference of approximately 2% which is within the acceptable limit. The chained-elliptic function concept will be useful in designing low-cost high-performance microwave filters with various fabrication technologies for millimetre-wave applications.

In this paper, an eight-port antenna array operating in the 2.6 GHz band (2550-2650 MHz) for a multi-input multi-output (MIMO) mobile terminal is presented. The design is composed of four pairs of compact dual-polarized slot antennas that are symmetrically placed at the corners of a mobile-phone mainboard. Each antenna pair consists of miniaturized petal-shaped slot resonators fed by two independent microstrip-feeding lines, thus facilitating radiation pattern and polarization diversity: when acting together, they facilitate multi-channel MIMO operation. The design offers good isolation, dual polarization and full radiation coverage in a smartphone sized package. A low-cost FR-4 dielectric (ε = 4.4, δ = 0.02, and h = 0.8 mm) with a dimension of 75×150 mm² is used as the PCB substrate. The characteristics of the smartphone antenna are examined using both simulations and measurements.

This work reports the application of a microwave sensor in measuring human blood glucose concentration. The main contribution of this work lies on the blood glucose profile which is collected from 69 random patients regardless of their gender, age, and haematology properties, instead of using water as the base or focusing on a single person. Hence the blood glucose profile is more realistic. Blood is extracted from the participants and dropped at the center of the dumbbells section of a microstrip defected ground structure to gather the notch frequency shifting data. On the other hand, the blood samples are measured using Omron Freestyle Glucometer to collect their associated blood glucose readings. Five predicting models have been proposed in this work. Based on the cross-validation, it is found that the blood glucose level can be correlated very well with shifted notch frequency by using a linear model. It introduces least root mean square error (RMSE) of 0.0592 and shows good correlation (R² = 0.9356) between the reading from commercial glucometer and microwave sensor in the range up to 12 mmol/L. The reliability of this microwave sensor is proven once again when the predicted blood glucose data are all falling in Zone A of Clarke Error Grid. The outcome of this work shows the capability of this microwave sensor in measuring the blood glucose level. Since this microwave sensor can be reused under a proper cleaning procedure, it improves the sustainability of conventional blood glucose testing by reducing the disposal of testing strips and cost. It is believed that this sensor will be suitable for extensive blood glucose testing conducted in the laboratory.

This study proposes the idea of a thermotherapy device for the treatment of human knee joint disorders by the thermal effect of microwave radiation. The device is composed of a circular array of dipole antennas operating at 2.45 GHz. A high resolution three dimensional geometric, electric, and thermal model for a human right knee is constructed. Electromagnetic simulations are performed to calculate the specific absorption rate (SAR) distribution within the tissues of the human knee using the finite difference time domain (FDTD) method. The SAR distributions are calculated for four and eight elements circular arrays. The FDTD is applied to calculate the rise in temperature within different tissues of the human knee due to the exposure to different levels of heating microwave power. The effect of the tissue thermoregulatory response on the temperature rise is investigated for each individual tissue type. Moreover, the dependence of the induced steady state rises in tissue temperatures on the absorbed SAR is studied in the case of the SAR at a point in the muscle tissue (local SAR), and the SAR averaged over 1 g (SAR_{1 g}) and over 10 g (SAR_{10 g}). The rise in temperature distribution due to radiation from the circular array of dipoles is calculated at different cross sections.

For microwave computational imaging (MCI), the reduction of measurement matrix's coherences permits better reconstruction performance. Therefore, frequency diverse apertures (FDAs) have become a major option of antennas for MCI due to their frequency-varying radiation patterns. The frequency diversity in the patterns reduces coherences; however, the losses in practical materials and the finite sizes of apertures impose upper limits on frequency diversity. For further coherence reduction, the polarization diversity (PD) of aperture elements is as a new approach introduced in this paper. We present an electromagnetic formulation of scattering aperture elements' PD. In the formulation, the PD brings an additional degree of freedom in the generation of the measurement matrix, given the apertures being illuminated with varying polarizations. This new degree of freedom enables a potential of reducing the coherences. Two complementary electric-field-coupled (cELC) scattering apertures, which differentiate in the polarizations of elements, are fabricated for validation. A set of comparisons yielded by the near-field scanning data of these apertures shows that the PD effectively reduces coherences and improves reconstruction performance.

This paper details the work of the LAPLACE Electromagnetism Research Group to develop an original measuring setup dedicated to the detection of an EMDrive like force. Recent peer-reviewed experimental results [1, 2] were obtained using similar setups based on a torsion pendulum combined with an optical sensor. These very accurate measurement setups are appropriate for measuring such an extremely weak force. They also appear costly, which may discourage other research teams from working on this topic. Our main goal is then to provide an alternative configuration, based on a commercial precision balance, in order to build a measuring setup more affordable, handy, and accurate enough to measure an EMDrive like force. Our experimental system is capable of feeding a truncated cone shaped 2.45 GHz resonant cavity with power up to 140 W. To calibrate the EMDrive force and avoid false positive thrusts, an original setup has been proposed and evaluated. It allows us to really consider that the parasitic effects do not alter the hypothetical force measurement by the use of force direction switching during the measurement.

High resolution wide swath (HRWS) imaging and ground moving target indication (GMTI) are similar in terms of system architecture and are based on a multi-channel system in the azimuth direction. However, in order to achieve their respective performance requirements, the HRWS SAR requires a lower pulse repetition frequency (PRF), and the GMTI system requires a relatively higher PRF. In consideration of this contradiction, the parameters of the moving target are introduced into the reconstructed filtering vector constructed by each signal reconstruction algorithm, so that the HRWS imaging of the moving target can be realized. In this paper, considering the characteristics of the Relax algorithm, a motion-adapted signal reconstruction algorithm is proposed, and the iterative process of the new method is described in detail. This method can perform GMTI on moving targets with a lower PRF without changing the PRF of the HRWS SAR system. By the simulation of point target echo, and comparing with the traditional signal reconstruction algorithms, the reliability and effectiveness of the new method are verified.

Today, worldwide more than five billion of wireless devices are directly communicating for voice and data transmission. The amount of data utilization has increased remarkably and here comes 5G technology with more prominent features, offering high data rate, low latency rate, efficient EM spectrum utilization, an immense machine-2-machine communication, etc. The efficient implementation of 5G technologies requires efficient and compact antennas. This work presents a novel multiband rectangular dielectric resonator antenna for future 5G wireless communication system, having stacked radiator with semi-circular slots etched on the left and right sides of an upper radiator. Additionally, a semi-elliptical slots rectangular microstrip patch antenna of the same dimensions for the purpose of comparison is designed. 28 and 38 GHz, which are the proposed 5G bands by most researchers, are the core target of this work. Alumina with a high relative permittivity of 9.8 is used as a radiator in the design of DRA, while common in the design of both proposed antennas, Rogers RT/DUROID 5880 with a relative permittivity of 2.2 having standard thickness is used as substrate material. Both the proposed antennas have an overall same size of 13 x 11.25 mm². The proposed dielectric antenna resonates at 25.4, 34.6, and 38 GHz with a 7.34, 4.04 and 3.30 GHz of wide impedance bandwidth covering the targeted 5G, 28 and 38 GHz bands, having a good return loss of -34.7, -31.8 and -33.5 dB, respectively. Further, the proposed dielectric antenna has a maximum radiation efficiency of 97.63%, with overall radiation efficiency greater than 90%, and maximum gain of 7.6 dBi is also noted. On the other hand, the proposed microstrip antenna resonates at 28 and 38 GHz with a 1.49 and 1.01 GHz of moderate impedance bandwidth, having -23.6 and -27.1 dB of satisfactory return loss. Further, the proposed patch antenna has a maximum radiation efficiency of 90.33% at 28 GHz, with overall radiation efficiency of greater than 84%, and moderate gain of 5.45 dBi is also noted. Both the proposed antennas have a nearly omnidirectional radiation pattern at resonance frequencies, with VSWR less than 2. Comparative study of the two proposed antennas regarding radiation efficiency, return loss, gain, data rate and impedance bandwidth evidently shows that performance of DRA over MPA at millimeter wave is very good. The proposed antennasare simulated in CST Microwave studio v18.

We introduce a six-switch integrated ultra wideband (UWB) - frequency reconfigurable system for cognitive radio applications. With respect to the requirements of the cognitive radio, this proposed design incorporates a UWB section for sensing the frequency spectrum, and the same design is frequency reconfigured using switches to get narrow bands for communicating within the spectrum. The proposed design has a compact size of 40 mm x 40 mm x 1.6 mm and is printed on an FR4 substrate with relative permittivity 4.4. The first configuration of switches allows the antenna to have UWB characteristics from 3.10 to 12 GHz and beyond as per simulations and 3.13 to 12 GHz and beyond as per measurements. Configurations II to V cover the ultrawide band from 3.54 to 12 GHz through five narrow bands. Measured results match well with the simulated one. The comparative analysis of the antenna in terms of frequency reconfigurability is also included in this work which proves that the proposed design is an effective candidate for Cognitive Radio applications.

Symmetrically excited meandered microstrip line RF coil elements are widely utilized in multichannel approaches which have been proposed to be integrated in ultra-high field MRI system (i.e., 7T and higher). These elements have demonstrated strong magnetic field in the deep areas in the object under imaging. Designing a radio frequency (RF) coil array that employs these elements without decoupling networks might cause non-optimized driving performance of coil array which in turn result in non-clear image. In this paper, two different methods of decoupling have been studied: port decoupling and array elements decoupling. For port decoupling, the coil elements have been designed at Larmor frequency (297.3 MHz) whereas for array elements decoupling, the coil elements have been designed at higher frequencies but matched at Larmor frequency. Port decoupling does not always mean element decoupling. Conventional decoupling methods, such as single capacitor or inductor, face challenges to realize the coil element decoupling for meandered microstrip arrays. An optimized reactive (T-shaped) network is needed in order to achieve element decoupling which in turn prevents distortion of the EM field. All simulation results have been obtained using the CST time domain solver (CST AG, Darmstadt, Germany).

In this paper, the investigation about a metal-insulator-metal (MIM) compound plasmonic waveguide is reported, which possesses the transmission property of plasmon induced transparency (PIT) and exhibits the potential application of refractive index sensing. The waveguide structure consists of an MIM-type bus waveguide, a horizontally placed asymmetric H-type resonator (AHR), and a circular ring resonator (CRR). The AHR is directly coupled with the bus waveguide, whilethe CRR is directly coupled to the AHR, but is indirectly coupled to the bus waveguide. Due to the destructive interference between two different transmission paths, PIT effect can be observed in the transmission spectrum. The finite element method (FEM) is used to study the PIT effect in detail. The results show that the transmission characteristics can be flexibly adjusted by changing the geometric parameters of the structure, and the proposed waveguide structure has potential application prospects in the area of temperature and refractive index sensing with higher sensitivity, better figure of merit, and in the area of slow light photonic devices.

A new structure design of a multi-band suspended stepped slot microstrip patch antenna with copper ground plane for future mobile communications is proposed and presented. A parametric study for the effect on the proposed antenna is done on a par with the integration of a polycrystalline silicon solar cell. The compact low profile proposed antenna is developed using Printed Circuit Board (PCB) technology on a substrate, FR4 with physical size of 50×50 mm². Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for Wi-Max and future mobile communications. The measured result reveals that the presented stepped slot patch antenna with copper ground plane offers impedance bandwidth of 3.94% (covering 5.46 GHz-5.68 GHz band), 3.06% (covering 7.08 GHz-7.3 GHz band), and 9.26% (covering 8.34 GHz-9.15 GHz band). The same radiating patch with solar ground plane offers impedance bandwidth of 4.58% (covering 5.12 GHz-5.36 GHz band) and 3.06% (covering 7.32 GHz-8.02 GHz band) for future mobile communications. Good VSWR and radiation pattern characteristics are obtained in the frequency band of interest.

In this work we describe a model for the computation of the scalar and vector potentials associated with known electric and magnetic fields, as well as for the inverse problem. The formulation is general, but the applications motivating our study are related to the requirements for advanced modeling of charged particle dynamics in plasma-driven electromagnetic environments. The dependence of the electromagnetic field and its potentials in space and time is assumed to be separable, where the spatial part is connected to established solutions of the static problem, and the temporal part is derived from a phenomenological description based on time-series of measurements. We benchmark our model in the simple problem of a finite current-carrying conductor, for which an analytical solution is feasible, and then present numerical results from simulations of a magnetospheric disturbance in geospace.

There is a large body of literature for electrically-small loop receiving antennas including more recent work in demagnetization effects for magnetic materials which are used for reducing antenna size. Optimal design of loop antennas requires understanding the electromagnetic principles and is limited by the accuracy of predicting the electromagnetic parameters (resistance, inductance, capacitance, effective permeability, sensitivity). We present the design principles for electrically-small loop receiving antennas including recommended formulas, a novel approach to optimal design, and an application example for use in the VLF/LF band (1-100 kHz) for two different ferrite-core loop antennas including the optimum coil parameters. Using a ferrite magnetic core greatly complicates analysis and prediction of resistance, inductance, and sensitivity as a function of frequency due to the dependence on core material properties, core geometry, and wire coil geometry upon the core (capacitance is typically negligibly affected). Experimental results for the two ferrite-core loop antennas and an air-core loop antenna validate the optimal design approach with good overall agreement to theoretical prediction of resistance, inductance, and sensitivity. Discussion and comparison between air-core and ferrite-core designs demonstrate the trade-off between outer diameter, length, and mass vs. sensitivity.

In this paper, a dual notch Ultra Wideband (UWB) monopole antenna with compact dimensions of 37.8×27.1×1.6 mm³ is presented. Octagon patch with defected ground structure is used to attain the wide frequency range of 3.17 GHz-11.61 GHz with ultra-wide impedance bandwidth of 8.33 GHz. The band notch characteristics in WiMAX (3.2 GHz-3.67 GHz) and WLAN (4.32 GHz-5.81 GHz) bands are achieved using inverted pi-slot in the radiating element and a pair of double split ring resonators (DSRRs) on either sides of the feed respectively. Reconfigurability in the bands is obtained by using BAR64-02 pin diodes switching at the appropriate placement in the antenna structure. The proposed antenna exhibits efficiency of 88% in operating and 20% in non-operating frequencies. The proposed antenna is designed, simulated and optimized using HFSS 19 electromagnetic tool. The measured results are tested using combinational analyzer in chamber with antenna measurement setup for validation and found in good matching with simulation.

In this paper, a compact Giuseppe Peano, Cantor Set and Sierpinski Carpet fractals based hybrid fractal Antenna (GCSA) is designed and developed for Industrial, Scientific and Medical (ISM) band applications. The proposed GCSA is a hybrid fractal design which is created by fusing Giuseppe Peano, Cantor set and Sierpinski carpet fractals together. The optimization of the microstrip line feed position is performed by using a Firefly Algorithm (FA). The substrate material employed for proposed GCSA is a low-priced, easily available FR4 epoxy of thickness 1.6 mm. By varying the geometrical dimensions of the radiating patch, a data set of 58 GCSAs is randomly generated for the realization of Artificial Neural Network (ANN) and FA approaches. The designed structure is fabricated and then measured results are evaluated. The proposed GCSA is capable of resonating at 2.4450 GHz with S(1,1) < -10 dB. The measured bandwidth of the operating ISM band is 101 MHz. The quantitative performance of three different ANN types reveals that Feed Forward Back Propagation ANN (FFBPN) shows minimum error in comparison to other two ANN types. The simulated, experimental and optimized results show a good match that specifies the preciseness of the measurement.

In this research, the potential of L-band SAR data is evaluated for tropical peatland forest biomass estimation using polarimetric features and field data. For this, ALOS-2 full polarimetric data are acquired over central Kalimantan, Indonesia. Total 54 sampled plots (20 m x 20 m) were established in the study site; diameter at breast height (DBH) and tree species of every tree were collected in each plot. Locally developed allometric equations were used to convert field data to biomass and plot level biomass, and the upscaling factor was applied to upscale plot level biomass to standard tones per hectare scale. Backscattering coefficient (σ_o) was computed for HH, HV, VH and VV polarization. Similarly, eigen decomposition was performed to extract: entropy (E), alpha (α), and anisotropy (A); also diversity indices were computed. Yamaguchi decomposition was performed to extract scattering behavior of forest in central Kalimantan. All polarimetric parameters were upscaled to one-hectare scale. Field data were divided into training plots (70 percent → 42 plots) and validation plots (30 percent → 12 plots). Nonlinear regression analysis was performed between polarimetric parameters and training plots. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV, and volumetric scattering component were found significantly correlated (ranging R² from 0.67 to 0.49) with the field data. The corresponding nonlinear model was inverted, and biomass maps were computed for the individual model. The resultant biomass maps were validated using validation set of referenced measurements. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV and volumetric scattering exhibited a significant correlation between field biomass and predicted biomass computed using developed model. R² for validation ranges from 0.95 to 0.81 with RMSE ranging from 13.59 Mgha^-1 to 25.63 Mgha^-1. The estimated biomass in study site ranges from 49.31 Mgha^-1 to 290.60 Mgha^-1.

Wide bandwidth and high gain designs of sectoral microstrip antennas gap-coupled with parasitic arc shape patches are proposed. In 1800 MHz frequency band, optimum response with bandwidth of more than 50% and peak gain of 10 dBi is obtained for 30° sectoral angle employing two gap-coupled arc shape patches. Further gap-coupled variations of slot cut single arc shape patch with 60° sectoral patch is presented. This design yields bandwidth of above 930 MHz (~53%) with peak gain of more than 10 dBi. The comparison for the proposed gap-coupled sectoral variations with reported antennas is presented. Proposed gap-coupled sectoral configurations are single layer and thus simple in design and yet offers bandwidth and gain of larger than 50% and 10 dBi, respectively.

In the development of hand gesture based Human to Machine Interface, the Doppler response feature extraction method plays an important role in translating hand gesture of certain information. The Doppler response feature extraction method from hand gesture sign was proposed and designed by combining time and frequency domain analysis. The extraction of the Doppler response features at the time domain is developed by using cross correlation, and the time domain feature is represented by using peak value of cross correlation result and its time shift. The Doppler response feature of frequency domain is extracted by employing a discriminator filter determined by the frequency spectrum observation of Doppler response. The proposed method was employed as a pre-processing for Continuous Wave (CW) radar output signals, which is able to relieve the pattern classification of Doppler response associated with each hand gesture. The simulation and laboratory experiment using HB 100 Doppler radar were performed to investigate the proposed method. The results show that the combination of all three features was capable of differentiating every type of hand gestures movement.

With reference to the mask-constrained power synthesis of shaped beams through fixed-geometry antenna arrays, we elaborate a recently proposed approach and introduce an innovative effective technique. In particular, the proposed formulation, which can take into account mutual coupling and mounting platform effects, relieson a nested optimization where the external global optimization acts on the field's phase shifts over a minimal number of `control points' located into the target region whereas the internal optimization acts instead on excitations. As the internal optimization of the ripple is shown to result in a Convex Programming problem and the external optimization deals with a reduced number of unknowns, a full control of the shaped beam's ripple and sidelobe level is achieved even in the case of arrays having a large size and aimed at generating large-footprint patterns. Examples involving comparisons with benchmark approaches as well as full-wave simulated realistic antennas are provided.

In this paper, a three-port pattern diversity antenna with a Fabry-Perot cavity (FPC) using a partially reflective surface (PRS) for 5.2 GHz Wireless Local Area Network (WLAN) access points is proposed. The topology of three coaxial-fed circular patch antennas provides an initial beam tilt of 15˚. The PRS aperture, at a height of approximately λ/2, is then shaped in such a way for the antenna to radiate at 0˚, +25˚, -25˚, which results in total coverage of 90˚. The antenna system has an impedance bandwidth of 2% ranging from 5.16 GHz-5.25 GHz (90 MHz bandwidth), covering the IEEE 802.11a band, for a gain of 10 dBi throughout the band and across the ports. The shaped PRS structure provides a gain enhancement of 4.5 dB. The mutual coupling between any two ports in the three-port antenna system is less than 17 dB for a port-to-port distance of 0.67λ.

An improved wideband cavity-backed antenna and a planar phased array with wideband wide-angle impedance matching (WAIM) are provided in this paper. A step-shaped cavity is applied in the antenna, so the relative bandwidth of VSWR < 2 can be improved to more than 52% without increasing the cavity profile. Furthermore, a planar phased array constructed by the cavity-backed antenna can work with a wide-angle scanning range of ±60° at both E- and H-planes. Due to the wide-angle scanning range, the impedance matching for the phased array will be unstable in the required wideband. Consequently, the matching layer with metamaterials has been loaded on the phased array. The VSWR is controlled within 2 in E-plane and 3.5 in H-plane during the scanning range of ±60° in wide bandwidth.

We present design and computational simulation of multiband, polarization-independent, and thin frequency-selective structures for microwave frequencies, and their fabrication via a very low-cost inkjet-printing procedure. The structures are constructed by periodically arranging unit cells that consist of U-shaped resonators, while polarization-independency is achieved by applying rotational arrangements. Various configurations are obtained by considering double and single U-shaped resonators, as well as rotational and complementary relationships between the corresponding unit cells on the top and bottom surfaces. We observe that complementary arrangements provide resonances with better quality, particularly by allowing the smaller resonators to operate as desired. Measurements on the fabricated samples demonstrate the feasibility of both effective and very low-cost inkjet-printed frequency-selective structures with multiband and polarization-independent characteristics.

For direct suspension force control (DSFC) strategy of Bearingless Brushless DC Motor (BBLDCM), combined with super-twisting algorithm, a second-order sliding mode (SOSM) controller is designed by direct suspension force. The control precision, robustness, and jitter suppression of the suspension subsystem are improved. The direct suspension force control based on the second-order sliding mode (SOSM-DSFC) controller solves the influence of external disturbance on the self-stabilizing suspension, effectively suppresses the rotor jitter problem, and improves the robustness of the rotor suspension.

Aparticular challenge encountered in designing massive MIMO systems is how to handle the enormous computational demands and complexity which necessitates developing a new highly efficient and accurate approach. Considering the large antenna array employed in the Base-Station (BS), in this work, we present a new paradigm to significantly reduce the simulation runtime and improve the computational efficiency of the combined rigorous simulations of the antenna array, 3-D channel model, and radiation patterns of the User Equipment (UE). We present an approach for evaluating a closed-loop massive MIMO channel capacity using 3-D beamforming to take advantage of spatial resources. The approach subdivides an M×N array at the BS into columns, rows, rectangular, or square subarrays, each consisting of a sub-group of antenna elements. The coupling is rigorously taken into account within each subarray; however, it is ignored among the subarrays. Results are demonstrated for a dual-polarized microstrip array with 128 ports. We consider simulation runtimes with respect to two different propagation environments and two different Signal-to-Noise-Ratios (SNRs). It is shown that the maximum difference in the closed-loop capacity evaluated using rigorous electromagnetic simulations and our proposed approach is 2.4% using the 2×(8×4) approach for both the 3-D Channel Model in the 3rd Generation Partnership Project (3GPP/3D) and the 3-D model in the independent and identically distributed (i.i.d/3D) model with a 46% reductional in computational resources compared with the full-wave antenna array modeling approach.

Fibre Bragg Gratings (FBGs) offer several advantages including their immunity to electromagnetic fields making them excellent in situ sensors for feature extraction in electrical machines condition monitoring. However, the pre-requisite of bonding FBGs circumferentially on either the machine cast frame or stator windings can introduce undesired sensing characteristics. This is because the FBG relies on adhesives as the transfer medium for any sensed parameter between the machine and sensor. Whilst FBG sensors rely mainly on wavelength shift, an intolerably low signal-to-noise ratio will result in difficulty in measuring such shifts. As a complementary signature, differential optical power can be combined with wavelength shift to broaden the feature extraction capability of FBG sensors. This makes power level (dBm) an important sensing parameter for FBG sensors. The effect of varying number of bonding points on transmitted optical power is investigated using unstripped and stripped bare fibres as well as an actual FBG sensor. Increasing the number of bonding points beyond an optimum number has been observed to significantly attenuate the optical signal power level and quality for a given dynamic range. Hence, as the number of bonding points is increased, the level of attenuation should be closely monitored to ensure that the optimum number is not exceeded if excellent and accurate FBG sensing characteristics are to be realised.

Due to suppressing the interference from WLAN (2.4-2.484 GHz), WiMAX (3.3-3.7 GHz), INST (4.5-4.8 GHz), X-band (7.25-7.75 GHz) and ITU band (8.01-8.5 GHz) signals in ultra-wideband (UWB) communication systems, a novel UWB antenna with five notch bands is proposed. Based on the methodologies of loading parasitic stubs and etching slots, the antenna is designed with five band rejection elements: a curved stub, a split square ring-shaped slot and a pair of vertical slots introduced in the patch, two C shaped stubs symmetrically set near the feed line, and a pair of L-shaped slots etched on the ground plane. The test results show that the antenna operating from 1.95 to 10.73 GHz is capable of rejecting the frequency bands around 2.4 GHz, 3.5 GHz, 4.6 GHz, 7.5 GHz, and 8.4 GHz. Meanwhile, in passbands the antenna has approximate omnidirectional radiation patterns and a peak gain higher than 1.7 dBi. The proposed antenna with dimensions of 31 × 35 × 1.5 mm³ is simple in structure and meets the requirements of UWB systems applications.

In this paper, a hexagonal-shaped multiple-input multiple-output (MIMO) patch antenna is presented. It covers the S band (2-4 GHz), WLAN (2400-2480 MHz & 5150-5350/5725-5875 MHz), UWB (3.1-10.6 GHz), and X band (8-12 GHz) applications. The proposed structure is simulated and fabricated on an FR4 substrate with overall dimensions of 0.186λ₀ x 0.373λ₀ and separation of two patches with a distance of 0.053λ₀ (where λ₀ is the wavelength at 2 GHz). The single UWB patch antenna is derived from the triangular-shaped edge cuttings in the bottom of the rectangular patch antenna with partial & defected ground. The proposed MIMO structure produces simulated results from 2 GHz to 13.3 GHz and measured results from 2.1 GHz to 12.9 GHz, with good agreement. The proposed structure resonates at 3.4 GHz, 5.8 GHz, 10.2 GHz and 11.8 GHz. Isolation improved to below -20 dB by placing an E-shaped tree structure and parasitic element. The radiation efficiency and peak gain values are 78-94% and 1.4-6.6 dB, respectively. Diversity performance of the proposed structure is verified with low envelope correlation coefficient (ECC < 0.04), high diversity gain (DG > 9.985), and acceptable total active reflection coefficient (TARC < -10 dB) values.

In this paper, a novel wide axial ratio bandwidth (ARBW), high gain, and low profile left-hand circularly polarized [4×4] elliptical microstrip array suitable for Ku-band satellite TV reception applications is introduced. A careful study has been done to get the optimum design to be suited for these application requirements. A circularly polarized microstrip patch with two stubs opposite to each other to produce two orthogonal modes is presented. The proposed element has 1.49 GHz 10-dB return loss bandwidth (RLBW), 0.44 GHz 3-dB Axial-ratio band (ARBW), and 6.9 dBi gain. A novel substrate integrated waveguide (SIW) feeding structure is investigated. Using the advantage of the output ports phase response of the SIW feeding network, two structures have been investigated. First, a [2×2] circular array has been designed, and although it has reached a good RLBW, this structure dose not achieve the required ARBW for the above-mentioned application. Further, a compact [2×2] sequential feeding network is designed to widen the ARBW. The measurement shows a very good result with about 12 dBi gain, 14.8% RLBW, and 12% ARBW. Finally, a [4×4] duple sequential feeding array is designed to increase the gain of the antenna to about 19 dBi, with 13% RLBW and 20.7% ARBW. In addition to that, the final antenna profile is 0.0184λ.

In this paper, a wideband antenna is designed systematically based on characteristic mode analysis (CMA). The antenna consists of a rectangle, a semi-annular ring, and a microstrip line. The radiating behavior and resonant frequencies of the radiating element are analyzed by using first four characteristic modes. First two modes only have wideband behavior and are excited by CPW feeding technique. The proposed antenna is printed on a low cost FR4 substrate with a size of 35x50x1.6 mm³ and impedance bandwidth ranging from 1.6 to 3.8 GHz for the applications of GSM, DCS, LTE, and WIMAX. To validate the proposed approach, the wideband antenna is fabricated and tested. A wide impedance bandwidth of 81% with |S₁₁| < -10 dB is achieved for both simulation and measurement results.

There are millions of people in the world exposed to weather-related land deformation hazards. These weather-related mass movement activities are most likely due to climate change, the decrease of permafrost area, the change in precipitation pattern, etc. Landslide is the most common land deformation incidents reported in Malaysia for the past few years. Therefore, Remote Sensing and Surveillance Technologies (CRSST), Multimedia University (MMU), Malaysia has developed the ground-based synthetic aperture radar (GBSAR) as a tool to monitor the high-risk area, which is prone to landslide continuously. Preliminary testing of the GBSAR has been conducted in Cameron Highland, Malaysia to verify the performance of the GBSAR and its capability of detecting landslide. However, the phase stability of the GBSAR is one of the most crucial factors that affect the detection capability of GBSAR, especially when it comes to the sub-mm measurement. This paper reports the phase stability study of the GBSAR and presents an empirical model for interferometric phase statistics.

Development and optimization of printed spiral coils have significant impacts on the efficiency and operating range for magnetic resonant wireless power transfer (WPT) applications. In this paper, the effects of different material losses (substrate and conducting coating) of printed coils are considered and experimentally studied in this paper. For the purposes of comparison and finding the dominated losses, lossy loaded capacitors with equivalent series resistances have also been investigated. A four-coil system with an external capacitor-loaded (ECL) magnetic resonant WPT system is considered, and a self-resonant coil is designed and compared. Results show that the ECL resonant coil has higher efficiency than the self-resonant coil with the same size and distance between the transmitting and receiving coils. Through observing the simulated results and analyzing experimental data, it can be concluded that the dominant cause of the decrease in efficiency of this ECL-WPT system is the strip resistive loss of coil of 57% and the ohmic loss in ECL of 37%. Meanwhile, the substrate loss significantly impacts on the efficiency of the self resonant coil. The overall measured efficiency is about 66% of the ECL coil at a distance of 50 mm when the above loss factors are considered. The measured results are in good agreement with the analysis and simulations.

This paper presents the design and analysis of a dual-band circularly polarized (CP) microstrip patch antenna for WLAN and vehicular communication applications. In this antenna, an L-shaped slot is cut, and a square parasitic patch with diagonally opposite corners cut is loaded in offset beneath to monopole antenna to realize dual band CP response with wideband response. The antenna exhibits dual band CP response at 2.45 GHz (WLAN) and 5.9 GHz (Vehicular) having 20.45% and 15.73% of simulated impedance bandwidth and 6.84% and 14.16% of axial ratio bandwidth for WLAN and Vehicular band respectively. The measured impedance bandwidth (S₁₁ < -10 dB) is 19.43% and 12.73% for WLAN and vehicular band respectively. The antenna design is simple and fabricated using an economical glass epoxy FR4 substrate with size of 45 × 40 mm². The measured results are found in good agreement with simulated results. The proposed antenna is analyzed using transmission line equivalent circuits, and the details are presented and discussed.

Electrical impedance tomography (EIT) is a technique for reconstructing conductivity distribution by injecting currents at the boundary of a subject and measuring the resulting changes in voltage. Sparse reconstruction can effectively reduce the noise and artifacts of reconstructed images and maintain edge information. The effective selection of sparse dictionary is the key to accurate sparse reconstruction. The EIT image can be efficiently reconstructed with adaptive dictionary learning, which is an iterative reconstruction algorithm by alternating the process of image reconstruction and dictionary learning. However, image accuracy and convergence rate depend on the initial dictionary, which was not given full consideration in previous studies. This leads to the low accuracy of image reconstruction model. In this paper, Recursive Least Squares Dictionary Learning Algorithm (RLS-DLA) is used to learn the initial dictionary for dictionary learning of sparse EIT reconstruction. Both simulated and experimental results indicate that the improved dictionary learning method not only improves the quality of reconstruction but also accelerates the convergence.

In this paper, the performance of relay selection in an energy harvesting aided mixed radio frequency (RF)/free space optical (FSO) system with transmit antenna selection (TAS) over atmospheric turbulence and pointing error is presented. The source of multiple antennas employs TAS to send information to the destination via multiple relay nodes. Also, the energy-limited source uses selection combining technique to harvest energy from multiple relay nodes. As a result, all the relay nodes act as a wireless power transmitting node as well as data receiving node. Moreover, it assumes that the RF/FSO links follow Rayleigh/Malaga (M) distributions with non-zero boresight (NB) pointing error on the FSO link. Therefore, the system outage probability closed-form expression is then derived which is utilized to obtain the system throughput. In addition, the results demonstrate the significant effect of atmospheric turbulence and NB pointing error on the system performance with multiple relays, and source transmit antenna offers the system better performance. The accuracy of the derived expressions is thus validated through Monte Carlo simulations.