Electromagnetic Interference (EMI) test is an important part for the manufacture of power electronic equipment, which helps us not only analyze the noise characteristics of the Equipment Under Test (EUT) but also design EMI filters. The previous separation method for the Common Mode (CM) and Differential Mode (DM) noise was time consuming or costly. In this paper, a novel measurement system for CM and DM conducted EMI is described showing a good performance. The system consists of two parts, part 1: getting CM noise or DM noise through a current probe; part 2: obtaining another mode noise from a software-based method. A 150w switch mode power supply is measured to verify the proposed measurement system. The noise spectra of CM and DM signal is shown, and the results obtained by software program are compared with those obtained from a current probe measurement showing a good concordance in terms of peak value.

A compact reconfigurable four-feeding microstrip antenna with polarization diversity is presented in this paper. With four triangle-shaped elements as the radiation patch, the proposed antenna can achieve good impedance match for linear polarization (LP), left hand circular polarization (LHCP) and right hand circular polarization (RHCP). A four-way power divider made by three Wilkinson power dividers and interconnected with PIN diodes is designed to feed the four elements. By controlling the states of the diodes, the antenna can produce LP, LHCP and RHCP. By using T-shaped slots on the patch and back to back geometry, a compact size of 0.6λ₀× 0.6λ₀×0.02λ₀ is achieved. The impedance bandwidth of LP is about 80 MHz (3.3%), while the usable bandwidths (overlap of impedance bandwidth and AR bandwidth) of LHCP and RHCP are about 370 MHz (15%) and 250 MHz (10%). The average gain for LP is -2.1 dBi, and that for CP is -3.3 dBi. This reconfigurable patch antenna with switchable polarization has good performance and simple structure, which can be used for 2.4 GHz wireless communication systems.

Maintaining mutual coupling suppressing structure as simple as possible is becoming attractive in the electromagnetic and antenna community. A novel parasitic patch structure that can reduce mutual coupling between cavity-backed slot antenna elements is proposed and studied. The structure consists of only a simple rectangular patch inserted between the antenna elements and it is therefore low cost and straightforward to fabricate. The proposed structure can not only suppress the surface-mode propagation and reduce mutual coupling between slot antennas, but also improve radiation patterns. The features include small occupied area and very simple structure.

An L/C dual-band dual-polarized (DBDP) shared aperture microstrip array is proposed in the paper. In the array, the sandwiched stacked patch is employed for the L-band element to exploit the bandwidth for given element thickness. Several key issues regarding the proposed structure are discussed, including: 1) benefit of proposed L band sandwiched stacked patch; 2) C-band feeding method; 3) radiation performance in both bands. A prototype array of L/C DBDP sandwiched stacked patch is designed and fabricated to verify the feasibility of the proposed structure, where the measured data are presented in the paper.

A distinctive connection method in cascaded RF/MW active device system achieving both stability and low gain loss is presented. Unlike traditional methods (isolator and attenuator), the proposed solution introduces an appropriate length of transmission line to change the input impedance at the out-band instable frequency point and uses a narrow-band termination to absorb the instable power without deteriorating in-band signal. Moreover, the reason that instability often occurs in the cascaded system is analysed with S-parameters， and it turns out to be a kind of out-band instability. And then the solution is verified by an adjustable circuit example whose insertion loss is below 0.3 dB.

A novel frequency reconfigurable 4G Multiple-Input Multiple-Output (MIMO) handset antenna is presented and verified with experimental results. Frequency tuning is used to minimize the antenna volume and to compensate for the losses related to user-originated impedance detuning. Both antenna elements are independently frequency reconfigurable and can cover most of the LTE-A bands. The study compares the losses of CMOS- and MEMS-based digitally tunable capacitors (DTC). In addition, two prototypes with total antenna volumes of 1170 and 3900 mm³ have been studied. The results show that the larger antenna structure operates with an efficiency better than 49% across the frequencies of 698-960 MHz and better than 56% across the frequencies of 1430-2690 MHz, when a MEMS-based DTC is used. In addition, a new method is introduced to estimate the suitability of the antenna geometry for frequency tunable antennas.

A capacitor-loaded coupled loop structure is investigated for wireless power transfer at 6.78 MHz for a target transmission distance of 1 m. It is shown that the optimal configuration for this structure occurs when the coupled loops are coplanar. Therefore, by converting thick wires into wide strips, a planarized configuration can be achieved. Simulation results are verified in measurement, which shows a 60% overall power transfer efficiency at 1 m. The contribution of different loss mechanisms is examined. Next, power transfer efficiency in the presence of dielectric materials is investigated in simulation and measurement. Additionally, tuning capabilities that arise from the implementation of variable capacitors are shown. Finally, design space exploration is performed to examine design tradeoffs.

This paper deals with an innovative implementation of a semi-analytical modeling method, called the Distributed Points Source Method (DPSM), in the case of an eddy current problem. The DPSM has already shown great potentialities for the versatile and computationally efficient modeling of complex electrostatic, electromagnetic or ultrasonic problems. In this paper, we report a new implementation of the DPSM, called differential DPSM, which shows interesting prospects for the modeling of complex eddy current problems such as met in the non-destructive imaging of metallic parts. In this paper, the used eddy current imaging device is firstly presented. It is composed of an eddy current (EC) inducer and a magneto optical set-up used to translate the magnetic field distribution appearing at the surface of the imaged part, into a recordable optical image. In this study, the device is implemented for the time-harmonics (900 Hz) imaging of a two-layer aluminum based assembly, featuring surface-breaking and buried defects. Then, the basics of the time-harmonics DPSM modeling are recalled, and the differential approach is presented. It is implemented for the modeling of the interactions of the eddy current imaging device with the considered flawed assembly in the same operating conditions as the experimental implementation. The comparison between experimental and computed data obtained for millimetric surface and buried defects is presented in the form of complex magnetic cartographies and Lissajous plots. The obtained results show good agreement and open the way to the modeling of complex EC problems. Furthermore, the low computational complexity of the differential DPSM modelings makes it promising to consider for the solving of EC inverse problems.

Human body communication (HBC) is a promising wireless technology that uses the human body as part of the communication channel. HBC operates in the near-field of the high frequency (HF) band and in the lower frequencies of the very high frequency (VHF) band, where the electromagnetic field has the tendency to be confined inside the human body. Electromagnetic interference poses a serious reliability issue in HBC; consequently, it has been given increasing attention in regard to adapting techniques to curtail its degrading effect. Nevertheless, there is a gap in knowledge on the mechanism of HBC interference that is prompted when the human body is exposed to electromagnetic fields as well as the effect of the human body as an antenna on HBC. This paper narrows the gap by introducing the mechanisms of HBC interference caused by electromagnetic field exposure of human body. We derived analytic expressions for induced total axial current in the body and associated fields in the vicinity of the body when an imperfectly conducting cylindrical antenna model of the human body is illuminated by a vertically polarized plane wave within the 1-200 MHz frequency range. Also, fields in the vicinity of the human body model from an on-body HBC transmitter are calculated. Furthermore, conducted electromagnetic interference on externally embedded HBC receivers is also addressed. The results show that the maximum HBC gain near 50 MHz is due to whole-body resonance, and the maximum at 80 MHz is due to the resonance of the arm. Similarly, the results also suggest that the magnitude of induced axial current in the body due to electromagnetic field exposure of human body is higher near 50 MHz.

An orthogonal beam-forming network (BFN) is proposed for 4G pattern-diversity applications. Different from the traditional Butler beam-forming networks with 2^N orthogonal beams, the orthogonal BFN, composed of three 180° hybrids and a 90° phase shifter, provides three orthogonal beams. Design procedure of the orthogonal BFN based on the factorization of its transmission matrix is derived. Moreover, in order to implement the proposed orthogonal BFN with low insertion loss, a rat-race has been used to realize unequal power distribution between its two output ports. The measured scattering parameters of the orthogonal BFN are compared with the analytical and the simulated scattering parameters, validating the expected behavior. In addition, by varying the output power ratio of the non-equi-amplitude 180° hybrid, the performance of the orthogonal BFN is improved when the proposed orthogonal BFN is used in an antenna array.

A compact microstrip-fed antenna with dual band-notched characteristics for ultrawideband (UWB) applications is presented. By introducing two open-ended inverted L-shaped slots, two sharp notches are achieved at frequencies of 3.16-3.70 GHz and 5.10-5.95 GHz for VSWR < 2. A rectangular slot in the ground plane can improve the impedance bandwidth of the proposed antenna. The prototype occupies a compact area of 22 × 26 mm². The measurement results indicate that the proposed antenna can reject the interference with coexisting worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems. The proposed antenna shows relatively omnidirectional radiation patterns in the pass band.

This study proposes a differential-fed microstrip antenna, which is characterized with an ultra-wideband of 120% (3-12 GHz), improved radiation patterns, stable gains, and compact size. Two symmetrical trapezoid shaped slots and four triangle-cut corners on the ground are used to improve the impedance matching over the UWB frequency band. To clarify the improved radiation characteristics, the simulated radiation patterns of the proposed antenna are compared with the conventional single-ended feed UWB antennas. The measured results show that, in the entire frequency band, the designed antenna exhibits a stable radiation patterns and the gain variation is less than 2 dB. Furthermore, the polarization purity are increased compared with the conventional ones, especially in the high frequency band.

Soil density is one of the important parameters to be investigated in civil, geological and agricultural works. Unfortunately, the challenging issue is found on the suitable model in determining accurately the soil density. In this article, a new soil density model based on radio-wave surface reflection method is presented. The development of the model is based on result analysis collected from the experiment. Then, comparisons with related theoretical models, Hallikainen and Topp, are performed. The experiment is performed by using a vector network analyzer (VNA) that generates radar signal and recording return loss (S₁₁) from a horn antenna. In the analysis, two new proposed soil density models have shown good agreement for soil density from 1.1 g/cm³ to 1.7 g/cm³ for sand and silty sand samples. This is verified when the model able to predict real samples as the one used in the experiment and result shows a very small relative error within 0.05% and 6.87%. Additionally, spectrograms in real time were produced in this study in order to observe more on the soil density. By using the proposed developed models, soil density estimation can be easily determined with minimal data input such as soil type, return loss and reflection coefficient by using regular radio-wave devices.

Phase shifters are the key components of phased array systems which provide a low-profile solution for Ka-band satellite communications. In the transmitting mode, it is crucial for the phased array antenna system to meet the standard radiation masks, and any imperfections of phase shifters can yield into radiation mask violation. In this paper, we present the analytical approach to model the non-linear phase-frequency characteristics of Resonance-Based phase shifters, which constitute one of the most widely used class of phase shifters for Ka-band satellite communications. Furthermore, it has been investigated how the phase-frequency response non-linearity affects the phased array radiation patterns, gain, and the beam pointing direction. The simulation results show that, depending on the phase shifter phase-frequency response profile, the radiation mask satisfaction is an important factor in determining the system bandwidth.

This article presents the Wave Concept Iterative Procedure, an efficient method for characterization of substrate integrated Non-Radiative Dielectric passive circuits based on wave concept formulation and its iterative solution. WCIP simulations are compared to measurements and Finite Element Method simulations. A good agreement is achieved with computation time saving.

Three-dimensional Finite-Difference in Time-Domain method is applied to simulate Low Frequency antennas in the presence of natural environments. All antennas are made up of wires set down on a square shaped ground plane and their dimensions depend on the wavelength of the source. Both monopole and inverted L antennas are considered in this paper. The antenna systems are computed in the presence of two examples of natural elements: a large forest and then on the top of a hill. The main aim of this paper is to show the effects of these environments on the properties of the antennas and on the efficiency of the ground wave excitation. The outcome of these investigations shows a power ratio enhancement of several decibels when the two kinds of antenna described in this paper are located on the top of a hill. On the other hand, the effects of a large forest depend on the geometry of the antenna. It doesn't affect the radiation of a quarter-wave monopole antenna, on the contrary losses disrupt radiation when an inverted L antenna is built in the middle of a large forest.

A new dual-band dual-sense circularly polarized (CP) slot antenna is designed in this paper. The proposed antenna is composed of a rectangle patch and a modified ground plane. By opening a U-shaped open-slot and loading a vertical stub to the ground plane, a dual-sense CP performance is achieved for two frequency bands. A bevel is cut on the patch to improve the impedance matching. The antenna is fabricated on a low-cost FR4 substrate and fed by a coplanar waveguide (CPW) structure. The antenna has been investigated numerically, and a prototype was experimentally measured. Experimental results show that the measured 10-dB return loss impedance bandwidths are 18.3% (2.72-3.27 GHz) for the lower band and 23.7% (4.65-5.90 GHz) for the upper band, and the measured 3-dB axial ratio (AR) bandwidths for the lower and upper bands can be up to 28.4% (2.48-3.30 GHz) and 26.3% (4.63-6.03 GHz), respectively.

In this paper, a wideband differential phase shifter has been analyzed and designed using Genetic Algorithm (GA). The differential phase shifter consists of two fixed main lines of length λ/2, and parallel open and short stubs of length λ/8, which are shunted at the edge points of the main lines, respectively. With the application of GA, an impedance match and minimum phase deviation for the desired phase shift over a wide frequency band are obtained. In order to verify the optimum results, simulation experiments are made and a 45° phase shifter is fabricated and measured. The phase shifter exhibits an impedance bandwidth (|S₁₁|<-10 dB) and a consistent 45° (±2°) phase difference bandwidth around 66%.

We report the experimental measurements of weak light signal at 1550 nm wavelength with a high-quality factor microwave coplanar waveguide (CPW) resonators. The quality factor of this niobium λ/4 CPW resonator is measured as Q = 7.4×10⁵ at ultra-low temperature (20 mK). With this device, we developed a technique to implement the proper fiber-resonator coupling, and realized the desirable weak light detection at telecommunication wavelength with 35 pW resolution by probing the shift of resonance frequency (f₀). We found that the resonator shift increases with the increasing light power (from 11.7 pW to 9.77 nW), similar to the effects of increasing the system temperature (from 20 mK to 800 mK). The observed blue shifts of f₀ (with the increasing of either the temperature and the applied light powers) are thoroughly deviated from the usual Mattis-Bardeen theory prediction, and could be explained by the effects relating to the two-level system existed on surface of the CPW device.

A simple method for designing a triple-mode bandpass filter is presented in this paper. Triple-mode is achieved by using half-mode substrate integrated waveguide (HMSIW) cavity.Three perturbation metal vias were introduced for shifting resonant modes.The resonant frequencies of these modes can be adjusted by the location and the diameter of perturbation vias properly. In order to improve the out-of-band rejection, the CPW-to-SIW transition was added. A triple-mode HMSIW filter with the center frequency of 13 GHz was designed and fabricated. The measured fractional bandwidth is 35% with a transmission zero located at 20.4 GHz. Good agreement is observed between simulation and measurement.