In this article, a new wideband bowtie shaped slot antenna is realized on a flexible polyethylene terephthalate (PET). The slotted bowtie design is implemented with an asymmetric bow-tie flare angle and a larger feeding neck with a metal strip inside the bowtie slot to achieve a wider bandwidth and a higher gain. The designed free space antenna is fabricated using inkjet printing and tested. The fabricated antenna operates over 2.1-4.35 GHz frequency range (69.77% fractional bandwidth) which covers WLAN, WiMax, and most of the 3G and 4G frequency bands. Further, the antenna exhibits an omnidirectional radiation pattern with a peak gain of 6.3 dBi at 4.35 GHz. The bending test of the fabricated device reveals adequate flexibility without significant antenna performance degradation. Moreover, the antenna tunability for any mounting structure application is also investigated by simulating another version of the parent antenna (free space antenna) for drywall mounting applications. The tuned antenna covers a similar frequency band as a free space antenna maintaining the desired radiation performances. The compact size, higher bandwidth, omnidirectional pattern with a higher peak gain and flexible properties make the antenna design suitable for mounting structure for Internet of Things (IoT) applications.

It is well known that high refractive index contrast is essential to the formation of an omnidirectional Photonic Band Gap (PBG). It is generally cited also that the width of the omnidirectional PBG of a dielectric mirror is determined by the refractive-index contrast. But in this work, we show that this condition is not really general criteria. Dielectric mirror with higher refractive index contrast does not necessarily mean that it has the largest omnidirectional photonic band gap. So, we investigate the necessary conditions on the high and low refractive indices of the quarter wave layers to have the largest omnidirectional bandwidth in the visible range. We present a profound study of the omnidirectional band center wavelength and the bandwidth behaviors versus the layers refraction indices. It is shown therefore that one can modulate omnidirectional photonic band gap center by modulating the optical phase of the mirror.

The present paper investigates the propagation and dispersion of elastic surface waves in an asymmetric inhomogeneous isotropic three-layered plate in the presence of magnetic field and rotational effects. The skin layers are exposed to an external magnetic field force while the core layer is assumed to be in a rotational frame of reference, which are perfectly bounded together with free-ends conditions. The resultant displacements and shear stresses in the respective layers are derived analytically together with the general dispersion relation. Further, the general dispersion relation is analyzed for some physical cases of interest. Finally, the effects of the magnetic field, rotation and electric field on the propagation and dispersion of the present model are presented graphically.

This paper presents a dual-band microstrip antenna for Global System for Mobile Communications (GSM) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The split ring resonators structure driven antenna operates at 900 MHz and 3.3 GHz, respectively. Return losses achieved at the two resonance frequencies are 22.26 dB and 18.97 dB, respectively. The proposed antenna is developed on a cost-effective FR-4 substrate with relative permittivity 4.4, tangent loss 0.002, and partial ground plane. The bandwidths of the proposed antenna are 3.01% and 4.26%, respectively. The design and fabrication procedure along with both simulated and measured results are presented and discussed in this paper. Designed antenna delivers good performance and solution for both applications.

In this paper, a low-profile fractal antenna and its array for DSRC-band applications have been proposed. The proposed single element is a newly designed fractal antenna which is right-handed circularly polarized (RHCP) and derived from the Koch-snowflake 1st-iteration. Moreover, a diagonal slot defect in the ground plane has been implemented for resonating the structure at the desired frequency and, to get a low cross-polarization over the operating frequency. The compact feed-network of the array is designed using s Wilkinson power-divider. A single element and a 4 × 1 antenna array are designed, prototyped and verified. The antenna array is designed by a single-layer microstrip structure with a compact size of 151.70 × 43.50 mm². According to the experimental results, the single element and the antenna array have S₁₁ of -15.27 dB and -13.95 dB, and RHCP gain of 6.14 dBic and 11.98 dBic, respectively. Moreover, the computed radiation efficiencies of single element and array are 78.17% and 71.50%, respectively, while CP bandwidths of single element and array are 49.00 MHz and 58.00 MHz, respectively. The performance of the proposed RHCP antenna is suitable for the DSRC-band application.

In this paper, a new miniaturized switchable band microstrip patch antenna array using PIN-diode is presented for WLAN/WiMax applications. In the first stage DGS has been employed to miniaturize a dual band microstrip patch antenna array simultaneously resonating at 2.2 GHz and 3.8 GHz. Further in second stage RF PIN-diodes has been used to achieve the frequency reconfigurability to serve for different communication systems. The designs are verified through both simulation and measurement of fabricated prototype. The measured results were in good agreement with simulated results.

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a multi-layer dielectric material using a Ku-band rectangular waveguide WR62. The S_ij-parameters at the reference planes in the rectangular waveguide loaded by a multi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the two dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated S_ij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer and one tri-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from multi-layer measurements and mono-layer measurements is presented.

In order to research the temperature distribution of a hybrid excitation double stator bearingless switched reluctance motor (HEDSBSRM), the finite element method (FEM) is used to conduct thermal modeling and analysis. First, 2D FEM is used to calculate the losses of the motor, including the core losses and copper losses of the windings. Then, in the thermal analysis module of ANSYS Workbench software, losses are used for calculation and analysis as the thermal load. Furthermore, in order to enhance the accuracy of modeling, this paper also considers the equivalent thermal conductivity of each part of the motor, and the equivalent insulation of the windings and surface convection heat transfer coefficient are also considered. Finally, the simulation results of motor temperature field distribution are analyzed and studied in detail. The thermal characteristic is also of guiding significance to the optimal design of the motor.

This paper documents a novel design of dual-band dielectric resonator antenna exhibiting circular polarization at a high-frequency band of (7.85 GHz-7.93 GHz) in addition to linearly polarized lower frequency band of (5.12 GHz-5.49 GHz) using new materials, sapphire and TMM13i for antenna design. Sapphire and TMM13i being resistant to physical change, the novel design is suitable for weather radar application as circular polarization reduces signal attenuation in adverse climatic conditions. A four-layered structure with sapphire and TMM13i stacked alternatively with aperture coupled feed is presented. Additionally, the corners of the patch have been truncated, and a slot has been etched in order to obtain the dual-band resonance and circular polarization respectively. The design is simulated using Ansys HFSS and fabricated for measurements. The VSWR (Voltage standing wave ratio) is measured to be less than two for both the bands. The simulated and measured gains of the antenna are 5.2 dB and 4.9 dB, respectively.

In the study, an ultra-wideband array antenna for multifunction phased array radars (MPAR) is proposed. Due to the low-profile and ultra-wideband characteristics, the planar dipole elements are utilized to form an array antenna. Their performances are enhanced by using an optimized microstrip-sector feeding structure. The array antenna is a combination of subarrays, each of which corresponds to 4 × 4 transmit/receive channels. Four subarrays are fabricated in a standard printed circuit board (PCB) process to investigate the planar dipole array antenna theoretically and experimentally. Both simulated and measured results show that the proposed array antenna achieves 87.0% impedance bandwidth (VSWR < 2.0 in the normal direction) from 1.3 GHz to 3.3 GHz, according to the specific requirements of an MPAR project. The active VSWR is less than 2.0 and 3.0 while the scan angle is -30˚~30˚ and -45˚~45˚, respectively. It means that this array antenna has wide-scan capability. In general, the balanced optimization between the electrical and mechanical performances makes the proposed array antenna attractive for MPARs and other compact systems.

In this paper a novel branch-line printed inverted-F antenna (IFA) loaded with a rectangular complementary split-ring resonator (CSRR) is proposed, designed and experimentally studied. The proposed antenna shows four operating frequencies and can be used for various cellular and wireless applications (900 MHz/3.5 GHz/4.2 GHz/5.5 GHz). The antenna is compact in size having dimensions 0.059λ₀ × 0.053λ₀ × 0.002λ₀ at the lowest resonance frequency. Each of the bands is independently tunable and shows circular polarisation (CP) in the WLAN band with linear polarization (LP) in the other three bands. The axial ratio (AR) bandwidth is 1.82% in WLAN band. The simulated and fabricated results are reported in terms of S-parameters and radiation pattern. The prototype of the antenna has been fabricated and measured using VNA and simulation done in ANSYS HFSS.

We propose a rewritable optical frequency filter based on a volume Bragg grating recorded by holography on an SBN:75 photorefractive crystal. The theoretical results show the possibility of implementing a narrow-band filter whose reflectance is total for the characteristic wavelength of the third harmonic of the infrared for both TE and TM polarizations by optimizing the size of the interference fringes and the angle of incidence of the beam to be filtered, which must be close to 80 degrees.

This study proposes a low-profile dual-band MIMO patch antenna array with improved isolation for 4G-LTE and 5G wireless communications. The proposed antenna design contains two closely-spaced coaxial-fed patch antennas with U-shaped slots to generate dual-band operation at 2.6/3.6 GHz 4G/5G bands. The mutual coupling between MIMO elements can be reduced simultaneously at both operation bands by employing a pair of C-shaped parasitic structures with different sizes between the radiating patches. The results show that the isolation between the antenna ports has been enhanced by about 13 dB and 10 dB at the operation frequencies with the presence of the proposed parasitic structures. The simulation and measurements of the proposed antenna design have been provided to verify the performance of the design.

A compact frequency-tuned bandpass filter (BPF) with sharp rejection characteristic is presented. It is composed of a trans-directional (TRD) coupled line and two short-circuited stubs. By changing the capacitor values of the coupled line and the electrical lengths of the short-circuited stubs, a frequency-tuned BPF with sharp rejection is obtained. For verification, a prototype tuned from 1.0 GHz to 1.6 GHz (46.2%) is designed and fabricated. The measured results show that the proposed structure exhibits the return loss of more than 17 dB, the insertion loss of 1.4 dB, and the 3-dB fractional bandwidth (BW) of 43.2-50%. Sharp rejections are also obtained, agreeing well with the simulation results.

This letter proposes a novel balanced triple-mode microstrip bandpass filter based on a double-sided parallel-strip line resonator for the first time. The triple-mode resonator is realized by a stub-loaded structure. Stripline-like structure is employed to excite the triple-mode resonator under differential mode operation. Meanwhile, good common mode suppression can also be achieved. For the demonstration, a balanced triple-mode microstrip filter was designed, fabricated and measured.

This work presents a hybrid analytical-numerical approach to evaluate the integral representations for the time-harmonic electromagnetic (EM) field components produced in the air space by a vertical magnetic dipole (VMD) placed on a plane homogeneous conducting medium. Explicit expressions for the fields are derived by substituting a rational approximation, generated by the vector fitting algorithm, for the non-analytic part of the integrand of the electric vector potential. This permits to rewrite the representation for the electric vector potential as a combination of simple closed-contour integrals around the pole singularities of the rational approximation, which may be directly evaluated. As a result, each field component is given as a sum of cylindrical Hankel functions depending on the radial distance between source and field points, plus an exponential term that is a function of the total distance of the field point from the dipole.

A novel compact (20 × 22 mm²) triple band eliminated monopole antenna for ultra-wideband (UWB) applications is presented. A novel radiating patch with reduced ground plane is utilized for achieving a -10 dB impedance bandwidth of 3.28-13.28 GHz. An upper inverted U-shaped slot is introduced into the radiating patch to notch C-band (3.68-4.19 GHz), and a lower inverted U-structured slot is utilized to eliminate WLAN band (5.18-5.82 GHz) interference. The interference due to down link of X-band (7.27-7.87 GHz) is rejected by via hole connected between patch and rectangular strip printed above the defected ground structure. The proposed antenna has nearly stable radiation patterns, and realized gain over UWB frequency range makes it suitable for recent portable wireless communication applications.

This paper presents a technique based on time domain reflectometry (TDR) to determine the dielectric and magnetic properties of lossless materials fitted inside a transmission line section. The proposed method involves three different line terminations namely open, short, and matched load. The described technique involves placing a sample of material under test (MUT) inside a terminated transmission line and exciting this with a vector network analyser from the other end to measure the reflection coefficient. Results achieved from a transmission line model were compared with numerical simulations obtained using CST Microwave Studio. The comparison shows that the electric and magnetic properties of a material may be determined precisely with this technique. Experimental results are also presented to validate the proposed method. Estimates of measurement errors, resulting from sample length uncertainty, vector network analyser uncertainty, and open-end inaccuracy are discussed.

This paper presents a method for calculating the air-cored coil impedance with the employment of a mathematical model of an ideal filamentary coil. The proposed algorithm enables assigning, in a very quick way, each cylindrical air-cored coil to the corresponding filamentary coil using only two equivalent parameters. The first of them is the radius of the coil, whereas the second one is the distance between the coil and the surface of the tested material. The changes both in the parameters of the system under consideration and in the tested material bring about the same change in the impedance of the air-cored coil and the corresponding filamentary coil. This property brings a lot of advantages, since it allows using simpler final formulas for the filamentary coil and performing the calculations in a much shorter time, while obtaining the same results as in the case of the air-cored coil. At the same time, the creation of the scale of the measuring instrument and its calibration becomes far simpler since it is based on only two equivalent parameters.

A triple-band patch antenna operating at 0.9, 1.8 and 2.4 GHz is presented. The triple-band characteristic is realized by using a radiating patch and two meander lines achieved by embedding slots in its radiating patch. According to the current distribution of the radiating patch, the locations of two meander lines are chosen. The proposed antenna has the advantages of the easy control of each resonant frequency and relatively simple antenna structure. The measured -10 dB impedance bandwidths are 30, 40, and 30 MHz at 0.9, 1.8, and 2.4 GHz, respectively. The simulated and measured radiation patterns and gains are also presented and discussed.