The measured raindrop size distribution (DSD) and the ITU-R model have been used to elucidate the regional and diurnal variations of rain attenuation in Indonesia, for Ku-band (13.6 GHz), Ka-band (35.6 GHz), and W-band (96 GHz) frequencies. The DSDs were measured by the Parsivel disdrometer at Kototabang (KT; 100.32˚E, 0.20˚S), Padang (PD; 100:21˚E, 0:57˚S), Pontianak (PT; 109:37˚E, 0:00˚S), Manado (MN; 124:92˚E, 1:55˚N) and Biak (BK; 136:10˚E, 1:18˚S). In general, PD, KT and PT have lower rain attenuation than those at MN and BK, for the same rainfall rate, due to lower concentration of small-sized drops at these sites as reported by a previous study. Considerable differences between the attenuation obtained from the DSD and the ITU-R model are observed at all locations, in particular for very heavy rainfall (R > 50 mm/h). For R < 50 mm/h, the specific rain attenuation of measured DSD is in fairly good agreement with that obtained from the ITU-R model. The specific rain attenuation obtained from the DSD shows diurnal variation, in agreement with a previous study at KT. The diurnal variation of rain attenuation is dependent on the frequency and rainfall rate. At KT and PT, the lowest rain attenuation for Ku-band is observed during 06:00-12:00 LT, but during this period the largest attenuation is observed for Ka- and W-bands. These phenomena may be due to the increasing role of small and medium-sized drops by increasing frequency.

An ultrathin absorptive/transmissive radome with dual passbands is presented in this paper. The total thickness of radome is only 5 mm. The dual passbands are located at around 1.05 GHz and 2.2 GHz, respectively. The absorbing band ranges from 6.28 GHz to 15.04 GHz for TE wave incidence and from 6.3 GHz to 15.16 GHz for TM wave incidence. Due to the miniaturized elements, the grating lobes are shifted out of absorbing band to higher frequency. Both numerical and experimental results are also given out.

In this paper, a lowpass filter with -3 dB cutoff frequency of 5.3 GHz using T-shaped and polygon resonators is presented. The applied resonators create a sharp transition band of 0.2 GHz from -3 dB to -40 dB. To obtain an ultra-wide stopband about 54 GHz (10.18f_c) with a suppressing level of -21 dB, two different suppressing cells are employed. The overall circuit size is 59.16 mm², which indicates a small occupied area. To clarify the performance of each resonator and describe the location of the transition zeros, exact equations based on the equivalent LC circuits have been calculated.

A new method of impedance synthesis of antenna array radiation fields based on a single methodological conception is presented. At first, an approximate solution for the current in the thin vibrator with variable impedance was obtained using the partial averaging operation of the integraldifferential equation. The variable impedance of the vibrator was taken into account in the form of an integral coefficient averaged along the vibrator length. The approach turns out to be common for radiators with impedance coatings of different configurations and (or) different distributions of lumped impedances. It is established that the shape of the vibrator radiation pattern (RP) does not depend on the form of the impedance distribution function, and it is determined only by the averaged value of the impedance distribution along the vibrator axis. The solution shows that the impedance coating of a symmetrical thin vibrator excited at the center by the voltage δ-generator affects the shape of the radiation pattern in the wave zone, and the effect is directly proportional to the small natural parameter of the problem. The synthesis problem of the radiator impedances for the spatial scanning of the RP was solved for the linear vibrator array. The analytical solution of the problem was obtained for the equidistant array of symmetric vibrators with equal excitation currents. The possibility of changing the RP shape over a wide range by varying the intrinsic complex impedances of the vibrators is demonstrated for an equidistant linear array consisting of 5 half-wave vibrators located at a distance of one eighth wavelength from each other in the free space.

This paper presents the design of a wideband blade shaped monopole antenna with a horizontally mounted aluminium tube on top of the blade covering 135-175 MHz frequency band using Electromagnetic Simulation software (CST Microwave StudioTM) along with a matching network whose characteristics have been evaluated by the Optimal Matching Network Identifier (OMNI) algorithm. OMNI algorithm is a search technique used in computing, to find out the optimum solution. The conventional quarter wavelength monopole antenna is a narrow band antenna with bandwidth of the order of 5% to 10% at its centre frequency. In order to increase the bandwidth of the antenna, a proper matching network has been incorporated along with it. Toroidal inductor based matching networks have been designed, and their characteristics are evaluated using Optimal Matching Network Identifier (OMNI) program in MATLAB software. By consolidating MATLAB and CST simulated results, the antenna prototype along with the optimal matching network has been practically implemented, and corresponding results have been verified. The details of simulated and measured results are also included. The proposed antenna finds numerous applications in various wideband communication systems.

A tri-band two-way filtering power divider structure is proposed based on HMSIW. Dual-band filtering power divider is realized by etching semicircular slots on HMSIW. The third passband is achieved by loading open-stub without affecting two other passbands. The return loss is less than -20 dB in each passband with 3 dB fractional bandwidths of 3.75%, 9.3% and 0.61%. The measured results are in agreement with the simulated ones in this paper. The filtering power divider has the advantages of simple structure, easy integration, etc. It has a good application prospect.

In this work, the multi-resonance behavior of a suspended ring antenna structure with a single port has been investigated. Introduction of symmetrical slots at each arm of the ring structure enables quad-band operation. The antenna yields good impedance matching at 3.4 GHz, 4.5 GHz, 5.8 GHz and 7.5 GHz with considerably high gain response up to 6 dBi. Maintaining suitable air height from the ground plane enhances the bandwidth up to 12%. This compact antenna shows bandwidths of 130 MHz, 360 MHz, 850 MHz, and 380 MHz, respectively. Each resonance claims an efficient use in next generation wireless communication within S-band and C-band radio links extensively and also applicable in WSNs/IoTs which requires a multi-functional antenna system. Theoretical analysis of the proposed antenna is investigated with the equivalent lumped circuit. The antenna element is excited using separate feed patch alongside of the ring. The antenna exhibits TM₁₀, TM₀₁, TM₁₁ excitation modes at different resonances. The said antenna is implemented on an FR4 substrate with dielectric constant of 4.4, substrate thickness of h = 1.56 mm and loss tangent of tanδ=0.02. The antenna is designed with physical dimensions of 18×18×7.56 mm³ which claims its compactness.

A simple dual-port sum-difference beam antenna with high isolation is proposed. A T-shaped slot is utilized to achieve both sum-difference beam pattern and high port-isolation. The slot coupling feeding structure simplifies the feeding network and avoids complicated fabrication. The proposed antenna is simulated, fabricated and measured. Experimental validations confirm that the antenna has 10-dB impedance bandwidths of 10.2% (4.82-5.33 GHz) for the sum port and 2.0% (4.95-5.05 GHz) for the difference port, respectively. In addition, high port-isolation better than 50dB is achieved covering a wide band from 4.0 GHz to 5.5 GHz. The proposed antenna exhibits a measured peak gain of 6.3 dBi for the sum beam and a null depth better than -26 dB for the difference beam. Measured results agree well with simulated ones.

Simulations of electromagnetic transients in transmission lines can be carried out using simple circuit model. In the case of applications of simple circuit models based on π circuits, there are problems mainly caused by numeric oscillations. The lumped-parameter π equivalent model can be used with some advantages. The numeric integration method applied to the simulations of electromagnetic transients is the trapezoidal rule. If this numeric method is associated to the π equivalent model, results obtained from the simulations are distorted by Gibbs' oscillations or numeric ones. The introduction of damping resistance parallel to the series RL branch of the π equivalent model can mitigate Gibbs' oscillations in obtained results. Voltage peaks caused by these oscillations can also be decreased. So, in this paper, the combined influences of the introduction of damping resistance, the number of π circuits and the time step are investigated searching for minimizing Gibbs' oscillations and the voltage peaks in electromagnetic transient simulations. For this, transient simulations are exhaustively carried out for determining the highest voltage peaks, ranges of damping resistances and other parameters of the model, which minimize these voltage peaks caused by Gibbs' oscillations.

This paper considers the localization of an emitter where the transmitted signal is unknown for receivers. To improve the localization accuracy, we propose an efficient method to estimate the emitter position by reconstructing the transmitted signal jointly. Simulation results show that the localization performance of the proposed method is much better than the existing algorithms.

A compact coplanar waveguide (CPW) fed close ring resonator (CRR) loaded four-element metamaterial (MTM) array antenna for wireless application is designed and discussed in this article. The array is designed with corporate feeding network, arranged in a manner to offer 3 dB power at its each element. The proposed 1×4 MTM array antenna offers a fractional bandwidth of 10.18% with respect to the resonance frequency of f_r = 2.26 GHz. At the resonance frequency of 2.26 GHz, the proposed 1×4 MTM array antenna offers a gain of 5.10 dBi in the direction of broadside radiation. Each element of the proposed array antenna consists of CRR, which removes the requirement of via and allows the design of a uniplanar MTM array. The overall electrical size of the single element antenna shows compactness of 0.255λ₀ × 0.155λ₀ × 0.012λ₀, where λ₀ is the free space wavelength at its resonance frequency of f_r = 2.3 GHz. The proposed MTM array antenna is designed, and simulated on ANSYS HFSS 14.0 and simulated results are verified with the fabricated proto-type.

Transformation optics is a convenient method to control paths of electromagnetic waves and radiation characteristics of antennas. In this paper, we try to increase the gain of Balanced Antipodal Vivaldi Antenna (BAVA) over 8-16 GHz frequency band using an optical conformal transformation. The proposed antenna can be implemented by ordinary dielectric materials and graded photonic crystals (GPCs). In this designed BAVA, better side lobe level (SLL) and cross-polarization are achieved compared to a conventional BAVA. Simulation results validate the performance of the design approach.

This paper presents a Ka-band 4-bit BiCMOS digital step attenuator with maximum attenuation of 7.5 dB (16 states). The proposed attenuator design is based on switched T-bridge network including phase correction network and is fabricated in 0.13 μm SiGe BiCMOS technology. Attenuator with phase correction structure shows root mean square (RMS) amplitude errors <0.8 dB at 31 to 33 GHz and the RMS insertion phase varying from 2.8° to 5.8° over 31-33 GHz. The measured insertion loss is 19 dB and total chip size including pad is 1.92×0.4 mm².

In this paper, we propose a novel interconnection technique for a flip-chip quad flat no-lead (FC QFN) package which can decrease the amount of the transmission line (TL) phase shift. The RF die inputs and outputs (I/O) are connected to the package lead fingers by a small size, 1000 μm length, microstrip line having a gap capacitor consisting of staked plates (fingers) where the space in between is filled by a ceramic material of 10.2 dielectric constant value. This technique can reduce the effect of transmission line inductance and makes the novel package interconnection behaving as a composite left right handed (CLRH) TL; hence, one can set the TL phase shift to zero degree at the desired operating frequency band (i.e. S-band) by just tuning geometrical and/or physical interconnection structure parameters.

The accuracy of wave propagation prediction is very important in telecommunication network planning. The parabolic equation model has an advantage in computation efficiency and accuracy for wave propagation prediction. The recursive convolution nonlocal boundary condition has an advantage in improving the computational efficiency. In this paper, the recursive convolution nonlocal boundary conditions are extended to deal with the issue of horizontal diffraction loss in multiple obstacles. The validation is performed with experiments and the results show a good agreement.

The scheme of energy and data wireless transmission with the same carrier based on M-ary Differentially-Encoded Amplitude and Phase Shift Keying (MDAPSK) technology is an effective method to implement energy supply and data communication for implantable medical devices. In this paper, based on a large number of finite-difference time-domain simulation analyses, combined with knowledge of the clinical demand for implantable medical devices, the 13.56-402 MHz band is selected as the biological channel frequency band, and attenuation characteristic analysis and mathematical modeling are carried out. Based on massive amounts of simulation data, the Levenberg-Marquardt and general global optimization methods are adopted to build a homogeneous and heterogeneous biological channel model in the aforementioned frequency band. In order to verify the reliability and versatility of the mathematical model, an adult male rabbit is employed for a living implantation experiment. Using a vector network analyzer, different frequency electromagnetic wave receiving efficiencies in different biological channels are measured. The measured data are highly consistent with the simulation data, which fully verifies the rationality of the proposed biological channel model. This work provides a theoretical basis and model reference for the clinical application of an implantable medical device wireless transmission system.

By introducing the Wilkinson divider and dual L-shaped strips as a feeding network, broadband design of planar circularly polarized (CP) annual-ring antenna for ultra-high frequency (UHF) RFID system is proposed and experimentally studied. The proposed broadband CP antenna can provide the impedance bandwidth (RL≥10 dB) of about 246 MHz (25.0% @ 985 MHz) and the 3 dB axial-ratio (AR) bandwidth of about 180 MHz (19.5% @ 925 MHz) to meet the worldwide UHF RFID band (860~960 MHz). Meanwhile, with unidirectional pattern in the XZ- and YZ-planes, the measured peak gain and radiation efficiency are about 7.7 dBic and 70% across the operating band, respectively.

A technique for converting a wide-band coplanar waveguide fed antenna to UWB by positioning slots in the modified ground plane (MGP) adjacent to the feed is proposed in this paper. The slots can be symmetrically or asymmetrically positioned for optimum performance. One slot pair is initially positioned through parametric analysis in the modified ground plane at an equal distance from the feed end for the maximum achievable impedance bandwidth. The second slot pair is similarly positioned, optimising the antenna for ultra wideband operation. Two CPW fed antenna geometries are experimented using the technique, one unique and the other, a generic circular monopole. Both antennas have MGP and are fabricated on an FR4 substrate. The analysis and simulation have been done in FEM based High Frequency Structure Simulator (HFSS). The performance of the two antennas is measured with a Vector Network Analyzer ‘Agilent PNAE8362B'. The impedance bandwidth and radiation pattern validate the performance of the antennas for ultra wideband applications. The experimentally obtained bandwidth precisely covers UWB, and principal patterns are uniform throughout the band.

One of the faults in medium voltage (MV) overhead power line is a high impedance fault (HIF) owing to low-current discharge to a tree (THIF). This type of fault generates signals in wide frequency bandwidth which may lead to electromagnetic interference (EMI) with neighboring devices and consequently results in degradation in the performance of nearby systems. This problem becomes more critical when MV power lines path is located in a wooded area in which there will be frequent transient conflicts between trees and power lines especially in the windy conditions. Given the importance of this issue, the ability of THIF to generate EMI is first demonstrated in this paper. Thereafter, a hybrid technique based on combination of quantile regression (QR) and empirical mode decomposition (EMD) is proposed to perform a feature extraction from THIF signals. By comparing the QR results of different samples of THIF signal with other similar signals, the validation of proposed method is depicted. In summary, the original contributions of current research include 1) assessing EMI due to THIFs, 2) using EMD in pre-processing of THIFs signals and extracting their main components, 3) recommending QR for the feature definition of THIF.

Nonlinear characteristics of semiconductor devices play a key role in the performances of circuits, but their modelling is still a big challenge in circuit simulations nowadays. This paper explores modelling nonlinear characteristics of circuits containing semiconductor devices by presenting a modified physically based simulation method. A p-i-n diode microstrip circuit is taken as a sample, and its nonlinear characteristics, such as the power limiting, bistability, and forward recovery characteristics, are simulated and analysed. The applied method demonstrates its good capability and accuracy of modelling the nonlinear characteristics in the simulation, and moreover clarifies the underlying physical mechanisms. In contrast, the Advanced Design System (ADS) software, a popular circuit simulation program based on the equivalent circuit model, fails to reveal some of those nonlinear characteristics.