This paper presents an analytical method for designing a high-efficiency frequency selective surface FSS-sandwiched dual-band circularly polarized reflectarray antenna. Results are obtained using the Computer Simulation Technology Microwave Studio (CST MWS). The antenna is designed to operate within the receiving (19.6-21.2 GHz) and transmitting (29.4-31 GHz) bands while sharing the same unit and aperture. A double-layer FSS is loaded between the upper and lower antennas to suppress mutual coupling. An analytic approximation method using conformal mapping to determine the effective permittivity (ε_{r, eff}) is observed. The transmission and reflection coefficients of the proposed FSS are synthesized using the transmission line approach. The comprehensive analyzed results obtained are compared with results obtained from the simulations performed in the CST MWS. To validate the performance of the proposed FSS-backed element configuration, a 20/30-GHz dual-band circularly polarized reflectarray with a 90-mm aperture is designed. The simulated gains are 23.3 dBi at 20 GHz and 27.7 dBi at 30 GHz with aperture efficiencies exceeding 45.25% and 57.85% in the receiving and transmitting bands, respectively.

A fifth-order bandpass filter with high selectivity and wide-stopband by using quarter- and half-wavelength uniform impedance resonators (UIRs) is presented in this letter. The use of a terminated coupled line provides controllable transmission zeros that can suppress the parasitic passbands. A pair of transmission zeros is generated on both sides of the passband by introducing cross-coupling. As a result, high selectivity and wide stopband can be achieved simultaneously. The method of controlling transmission zeros using a coupled line and an open/short-circuited stub is analyzed, and the method of improving passband selectivity using cross-coupling is given in detais. The concept is experimentally tested in a microstrip bandpass filter with center frequency 1 GHz. The measured attenuation is better than 24 dB up to 18 GHz.

A classification algorithm is applied to UHF radio frequency identification (RFID) system to estimate the indoor position of a passive tag utilizing a received signal strength indicator (RSSI). Passive tag signals are collected by conventional UHF RFID reader antenna located at two different positions. K-NN and curve fitting are used for distance estimation and examined at different frequencies within the range 902-928 MHz to find suitable frequencies which can minimize the average error. In the proposed method, the measured RSSI values are compared with the fingerprint database in different frequencies to find the nearest neighbor. The best accuracy achieved at frequency range 926-928 MHz is 18.3 cm. The monitoring system is composed of a reader and tags under test, which makes the proposed system robust, easy to set up, and with low cost. The limitation of the proposed method is also discussed.

A two port, integrated reconfigurable versatile antenna is proposed here. The proposed antenna can reconfigure its frequency, bandwidth, polarization state and radiation pattern and hence is versatile in its characteristics. The antenna is integrated in such a way that the space of one antenna can be used to print two antenna structures to increase the antenna versatility into a small package. PIN diodes are placed in a position so that the electrical switching of the PIN diodes makes every part of the antenna multipurpose. The prototype has been fabricated to authenticate the simulated results. The simulated and measured results are in good agreement. The antenna can be used for Cognitive Radio application.

This paper proposes a new compact quad-channel diplexer (2.45/4.2 GHz and 3.5/5.2 GHz) using defected stepped impedance resonators (DSIRs). The proposed quad-channel diplexer is composed of one common input feeding line, sixteen folded DSIRs, and two output feeding lines. Every four DSIRs are designed to determine passband characteristics of one individual channel, and two passbands are filtered out eventually at each output port. The distributed coupling technique featured by small loading effect is introduced to eliminate the necessity of extra impedance matching networks, which consequently results in a reduced circuit size. A diplexer prototype operated at 2.45/4.2 GHz and 3.5/5.2 GHz bands with measured 3-dB fractional bandwidths of 12.5%, 7.2%, 6.4%, and 5.0% has been implemented, showing a high isolation of larger than 33 dB between the two output ports. Experimental results coincide well with the theoretical predictions and simulation results.

A hybrid Minkowskized fractal-like antenna structure for wireless application is presented in this paper. The Minkowskized radiating structure and feed line have been designed at the top layer of FR-4 substrate (tan(δ) = 0.02, ε_r = 4.3, h = 1.6). A modified ground plane with a parasitic patch is etched at bottom side of the dielectric substrate. The fabricated antenna exhibits the resonance at frequencies 0.83, 1.05, 1.6, 2.12, 3.25, 3.75 and 5.2 GHz. It covers six bands of frequencies band-1 (0.825-0.835 GHz), band-2 (0.913-1.22 GHz), band-3 (1.33-1.79 GHz) band-4 (2.04-2.18 GHz) band-5 (2.9-3.91 GHz) and band-6 (4.9-5.64 GHz) for |S₁₁| ≤ -10 dB which are suitable for several wireless communication bands (i.e. GSM 900 MHz, 1800 MHz, Wi-MAX, Wi-Fi 802.11y and WLAN 802.11b/g/a). The surface current distribution and radiation pattern have been studied at resonating frequencies.

To obtain the volume fraction of a gas-liquid two-phase flow, a contactless electromagnetic coupling resonance based volume fraction detection (CECR-VFD) technique is proposed. By mathematical calculation and numerical simulation, it is found that the CECR-VFD method is a better alternative than the conventional electromagnetic induction based method. The distance between the excitation coil and receiving coil is firstly determined. Then the effect of the pipe length is investigated. Additionally, the relationship between the output voltage across the receiving coil and the volume fraction is studied for stratified flow and annular flow. Experiments have been carried out for validation, and the results indicate that the output voltage can be used to predict the volume fraction of a two-phase flow.

In this communication, a hybrid shaped wide slot antenna with hybrid parasitic element has been investigated which is fabricated on an FR-4 substrate (tanδ =0.02, ε_r=4.3). The mutual coupling (between the slot and tuning stub), tuning of resonating modes and bandwidth of the antenna are adjusted by changing the dimension of parasitic element and tuning stub. The measured fractional bandwidth of the proposed antenna is 146.82% for S₁₁<-10 dB which covers the frequency span from 0.92 to 6 GHz. This antenna exhibits resonances at 1.094, 1.56, 2.073, 2.67 and 4.02 GHz. Surface current distribution has been investigated, and series of equation are deduced for resonating frequencies. Radiation characteristic exhibits an eight-shaped pattern at fundamental mode frequency whereas at frequencies 2.85 and 3.91 GHz a distorted pattern has been observed. For understanding the behavior of the antenna, structural parameters are varied in specific ranges.

An SRR based compact wideband metamaterial inspired antenna for WiMAX (2.5-2.7)/WLAN (2.4-2.48)/Bluetooth (2.4-2.48)/LTE (2.3-2.4) applications has been fabricated and investigated in this paper. The proposed antenna structure has been designed with the concept of epsilon negative transmission line. It comprises a patch on the top of the substrate and SRR and ground connected through strip on the bottom of the substrate. The proposed antenna offers overall electrical dimensions of 0.29λ₀×0.19λ₀×0.015λ₀ where λ₀ represents the free space wavelength at the frequency of 2.88 GHz. Additionally, the designed antenna also provides simulated and measured -10 dB fractional bandwidths of 40.13% and 40.55% around the center frequencies of 2.89 and 2.88 GHz, respectively. The average simulated and measured total gains of the proposed antenna throughout the working band are 1.92 dB and 1.75 dB. Further the average simulated radiation efficiency throughout the entire -10 dB bandwidth of the deigned antenna is 96.2%.

Decreasing eddy current is very important for the realization of stability control of HoMB system. In order to improve the dynamic performance precision of HoMB in the design stage, the dynamics and stiffness analysis of a homopolar magnetic bearing (HoMB) has been studied in this paper. Because the polarities of the magnetic poles were not changed during the rotation of rotor, the effect of eddy-currents was often ignored in the previous researches. However, when the frequencies of vibration caused by external disturbance and control currents are very high, eddy-current effects have significant influence on the performance of HoMB. In order to predict the HoMB performance, guide the HoMB design and control of the HoMB system in high frequency, a dynamics model was built on the equivalent circuit method. Parameters of dynamic Modeling are frequency-dependent. The effect of eddy-currents on the current stiffness was studied. The analysis results show that the eddy current effect on HoMB can be reduced by increasing the air gap, decreasing the laminations thickness and decreasing the laminations conductivity.

A novel single probe-fed, single-layer, and single-patch triple-band microstrip antenna is presented. By incorporating two identical U-slots in the patch whose length is λ_d instead of 1/2λ_d in a conventional patch, three operating bands are achieved. Dual-beam radiation pattern is obtained at the upper band, and a single broadside beam radiation pattern is obtained at each of the lower and middle bands. The antenna's structure is simple. Only by using a single probe-fed point, the impedance matches well at all the three resonant frequencies. The measured and simulated results are in good agreement. The measured lower, middle, and upper bands are centered at 2.442 GHz, 3.505 GHz, and 5.787 GHz, respectively. The measured gains are 6.2 dBi at 2.442 GHz and 5.5 dBi at 3.505 GHz, respectively. At 5.787 GHz, the measured gains for the dual radiation beams are 8.4 dBi directed at 26° and 8.2 dBi directed at -38°, respectively. The proposed antenna can be a candidate for WLAN 2.4 GHz, WLAN 5.8 GHz, and 3.5 GHz of 5G (the fifth-generation mobile communication) operation.

We numerically demonstrate that an electromagnetically induced transparency (EIT) effect can be achieved in an all-dielectric metamaterial, whose micro unit consists of two cylindrical through-hole cubes (CTCs). Two CTCs produce electric and magnetic Mie resonances in the vicinity of 6.2 GHz, respectively. Specially, the appropriate control on the interaction between two Mie resonances can lead to destructive interference of scattering fields, and thus the EIT effect with low loss and high transmission can be achieved. The influences of key parameters of all-dielectric metamaterial on its EIT effects are also investigated. In addition, the slow wave property of proposed structure is verified by computing the group delay, and the superiority of CTC is discussed. Such an all-dielectric metamaterial may have potential applications in areas such as low loss slow wave devices and high sensitivity sensors.

With technical advancement and development, the amount of electronic equipment is increasing, while the functions of products are enhanced, and the routing density of Printed Circuit Boards (PCBs) becomes larger. In the electronic industry, medical instruments are used to diagnose, treat, mitigate or prevent human diseases, and maintain and promote health. Industrial PCs for medical use and their accessories should be immune to interference from external electromagnetic noise, and should not become interference sources of electromagnetic noise radiation, so they have become issues of interest with respect to ensuring safety of medical equipments in medical operation environments in recent years. This research relates to parametric design using the Taguchi Method in the early stage of product development for medical-grade touch panel computers. In considering the use of Radiated Emission (RE) in Electromagnetic Compatibility (EMC) as a response value, the experiment covers control factors such as PCB and mechanism design related parameters. In addition, peripheral devices used in conjunction with a product are considered as noise factors when the product is in use, while interaction between the control factors is studied. The Taguchi Method is used to select an appropriate inner/outer orthogonal array, and a response diagram and a variance method are used for analysis to provide an optimal set of design parameters, in which the number of routing layers of a riser card is 6; the EMI filter on the isolated card is 600 Ω; the shunt capacity for the clock on main board is 33p; and the isolated card is grounded. Moreover, it is found that an interaction exists between the number of routing layers of the riser card and the EMI filter of the isolated card. From the result of the experiment, with such a set of parameters, the SN (Signal to Noise Ratio) lies in the confidence interval, indicating good reproducibility of the experiment. Such a parametric design effectively improves the electromagnetic interference (EMI) characteristics of a product to meet design specifications required by customers, accelerate the R&D process of electronic products, and pass EMI test regulations required by various countries in order to improve industrial competitiveness.

Two mu-zero resonance (MZR) resonators are etched in the patch of a microstrip antenna. The two MZR resonators generate two new resonances. As the MZR resonances are lower than the microstrip antenna resonance and the resonances merge with each other, size reduction and bandwidth enhancement were obtained. A prototype was designed and measured. The measured impedance bandwidth increased from 640 MHz (5.31-5.95 GHz, 11.33%) of the referenced microstrip antenna (RMA) to 940 MHz (4.99-5.93 GHz, 17.22%) of the proposed MZR loaded microstrip antenna (MZR-MA). Moreover, the patch size is decreased from 0.354λ_l × 0.283λ_l of the RMA to 0.332 λl × 0.266λ_l of the MZR-MA, and unidirectional radiation patterns are obtained for the microstrip patch and MZR resonances. A microstrip line based model was built to analyze the MZR resonators.

This paper presents an ease of dual-mode diplexer with high signal isolation based on amplitude and phase cancellation technique. The dual-mode structure enables a compact and easy asymmetrical frequency response which also requires considerable attenuation between the proximity in frequency of the transmitter and that of the receiver. Two back-to back dual-mode three-port diplexers and a 180˚ phase shifter are easily employed to construct the proposed device, which are combined to form a four-port dual-mode diplexer. A 180˚ phase shift in one branch can be achieved by delayed transmission line. The simulated and measured four-port dual-mode diplexers are designed at the operational frequency of Tx/Rx at 1.95 GHz and 2.14 GHz, respectively. The measured results of Tx/Rx dual-mode diplexer devices are presented of 48.5 dB Tx/Rx isolation. This four-port dual-mode diplexer achieves the isolation (S₃₂) more than 21.5 dB compared with a conventional three-port dual-mode diplexer.

This paper presents the design and analysis of a wideband circularly polarized resonant cavity antenna (RCA). The antenna structure consists of dual-layer Jerusalem cross type partially reflective surface (PRS) above a two-port wideband circularly polarized patch antenna. The PRS enhances the gain of the feeding patch antenna over wide range of frequencies. The structure provides left hand as well as right hand circular polarizations. Parametric analysis of the structure is also presented. The measured 10 dB return loss bandwidth and 3 dB axial ratio bandwidth of the RCA are 25 % (8.24-10.63 GHz) and 28.8% (8.3 GHz-11.1 GHz), respectively. Isolation more than 10 dB is obtained for the frequency range 9.15-10.61 GHz. Measured results show peak realized gain of 9 dBi in the operating band.

A miniaturized U-Shape patch sensor (15 mm×15 mm) was designed at dual resonating frequencies (f_r) 5.2 GHz and 6.8 GHz). The proposed design printed on FR4 material with a thickness of 1.676 mm and relative permittivity 4.4. To simulate the performances of the proposed design, the CST Microwave Studio (CST MWS) was used. The reflection coefficient of U-Shape patch sensor was measured. Basmati rice was investigated, and bulk density was increased with increase of moisture content, hence varied from 554.3 to 591 kg/m³. It has the longest average rice length (L) 7.2 mm, average width (W) 1.61 mm, and L/W ratio 4.47. The percentage of moisture was varied from 10.12% to 20.35% calculated on a wet weight basis. The lowest mean relative error (MRE) determined between predicted moisture content (PMC) and actual moisture content (AMC) was 0.55% at dual frequencies.

This article presents the design and analysis of a dual-band antenna with circular polarization for ISM and WLAN band applications. The proposed antenna operates at two frequencies ranging from 2.1-3.1 GHz and 4.4-7.7 GHz with resonating frequencies at 2.45 GHz industrial, scientific and medical band (ISM) and 5.8 GHz wireless local area network band (WLAN). The antenna is fed by coplanar waveguide feeding (CPW) with an asymmetric ground structure, and the radiating element consists of 24 spokes in the design. The current antenna providing the impedance bandwidths of 38.4% and 49% at two operating bands. The proposed antenna exhibiting circular polarisation with 3 dB axial ratio bandwidth of 150 MHz at 2.33-2.48 GHz and 1600 MHz at 5.14-6.74 GHz. The designed antenna is fabricated on an RT Duroid 5880 substrate with dimensions of 40 x 28 x 0.4 mm³. The intension behind the design of this antenna is to use it for wearable applications in conformal nature with low specific absorption rate (SAR). The SAR values observed at two operating frequencies are 1.09 W/Kg and 1.47 W/Kg, respectively. The placement and radiation characteristics analysis is done with Ansys Savant tool, and the subsequent measured results provide good correlation with simulation results.

A time reversal method is proposed for imaging and hyperthermia of tumors in breast tissues. Time reversal is based on the reciprocal nature of the electromagnetic scalar wave equation. Time reversed scattered electric fields recorded by the receiver antenna array are back-propagated in an FDTD assisted numerical model to focus back at tumor locations. The potential of this approach for thermal therapy applications is demonstrated by calculating specific absorption rates associated with the time-reversed electromagnetic fields. Simulation results elucidate the feasibility and robustness of the approach. A pulsed time domain measurement system is developed for conducting experiments to detect and measure heat absorbed by single and multiple tumors inside a simple breast phantom.

Hierarchical (H-) matrix based fast direct and iterative algorithms are presented for acceleration of the Method of Moment (MoM) solution of the Surface-Volume-Surface Electric Field Integral Equation (SVS-EFIE) formulated for scattering and radiation problems on homogeneous dielectric objects. As the SVS-EFIE features the product of the integral operator mapping the tangential equivalent electric current on the surface of the scatterer to the volume polarization current and the integral operator mapping the volume polarization current to the tangential component of the scattered electric field, its MoM discretization produces the product of non-square matrices. Formation of the non-square H-matrices for the MoM discretized integral operators is described. The algorithms for arithmetics pertinent to the product of the non-square H-matrices are explained. The memory and CPU time complexity scaling of the required H-matrix operations are analyzed in details and verified numerically. The numerical validation of the proposed algorithm is provided for both the lowloss dielectric objects as well as for the high-loss biological tissues found in the bioelectromagnetics applications. The numerical experiments demonstrate a signicant reduction of memory usage and a considerable speedup for CPU time compared to nave MoM, thus, enabling solution of the large-scale scattering and radiation problems with the SVS-EFIE.