A novel design concept of dual-band 180° hybrid ring coupler is presented in this paper. Coupler is a key element in front-end building blocks of wireless transceiver systems such as industrial systems and consumer electronic devices. The proposed design is realized by combining multiple arbitrary length transmission lines operating at two frequencies with one dual-band 180° phase shifter. The even-odd mode method is applied to derive the design equations for proposed dual-band 3 dB 180° directional coupler. Based on the analysis, it is found that the realizable frequency ratio of the proposed coupler is very flexible (i.e. the ratio between the two operating frequencies). Moreover, the 180° phase shifter features arbitrary characteristic impedance (i.e. its characteristic impedance can be arbitrarily chosen), which further ensures the easy implementation of proposed structures. To prove the design concept, full-wave electromagnetic simulations are performed to design a dual-band ring hybrid coupler working at 0.9 and 1.98 GHz. An experimental prototype is fabricated on Rogers RT/Duroid 5880 board. The measurement results match well with the theoretical and numerical ones.

In this paper, a miniaturized planar rat-race coupler is proposed to achieve arbitrary power division ratio and harmonic suppression performance simultaneously. It consists of six enhanced T-shaped line sections. The T-shaped lines can be equivalent to arbitrary electrical length lines rather than the conventional λ/4 lines. The explicit design formulas are derived and the characteristic impedances variations with the freedom variable are discussed. Simulated and experimental results show the harmonic suppression to be over -35 dB, while maintaining the conventional performance at the fundamental frequency. The circuit area of the prototype is only 30.8% of the conventional coupler.

Multitarget tracking (MTT) in surveillance system is extremely challenging, due to uncertain data association, maneuverable target motion, dense clutter disturbance, and real-time processing requirements. A good many methods have been proposed to cope with these challenges. However, no up-to-date survey is available in the literature that can help to select suitable tracking algorithm for practical problem. This paper provides a comprehensive review of the state-of-the-art motion-based MTT techniques, classifies existing methods into two groups, i.e., the detect-before-track (DBT) scheme and the track-before-detect (TBD) scheme. The DBT scheme is employed to achieve robust and tractable tracking performance when the signal-noise-ratio (SNR) is strong. The TBD scheme is used in the scenarios of low SNR, and it aims to cumulate target energy by multiple sensor frames. Furthermore, depending on the data association mechanism, the DBT methods can be classified into two categories, data association based approaches and finite set statistics (FISST) based approaches. And the TBD methods can be classified into non-Bayesian approaches and Bayesian approaches depending on the basis theory used for tracking. For each category, this paper provides the detailed descriptions of the representative algorithms, and examines their pros and cons. Finally, new trends for future research directions are offered.

We propose a framework based on the use of a flat-base Luneburg lens antenna with a waveguide array for Direction-of-Arrival (DOA) estimation, and also present a hybrid approach which combines waveguide mode extraction and signal processing techniques for enhancing the angular resolution of the lens antenna. The hybrid method involves sampling the electric field at specified positions when the lens is operating in the receive mode, and extracting the weights of the possible propagating modes in each waveguide. Following this, we correlate these weights with the known ones that have been derived by either simulated or measured signals from single targets located at different look angles, to make an initial estimate of the angular regions of possible DOAs. We then apply an algorithm based on the Singular Value Decomposition (SVD) of the simulated or measured database to estimate the angles of incidence. Numerical results show that the proposed framework, used in conjunction with the hybrid approach, can achieve an enhanced resolution over the conventional limit base on the 3 dB beamwidth of the lens antenna. Furthermore, it is capable of locating targets with different scattering cross-sections and achieving an angular resolution as small as 2˚, for a Luneburg lens antenna with an aperture size of 6.35λ and a Signal-to-Noise Ratio (SNR) of 30 dB.

This paper evaluates and compares the reflection loss, absorption loss and electromagnetic shielding effectiveness of a diverse range of shield. A design methodology is presented to yield these three quantities and propose a new relation of equivalent impedance for multilayer conductive sheets with considering the equivalence between single and the laminated structure. Analysis is carried out for the study of three shields: i) Polyaniline/polyurethane (PANI/PU), ii) Aluminum-Polyaniline/polyurethane-Aluminum (Al-(PANI/PU)-Al), iii) Nickel-Polyaniline/polyurethane-Aluminum (Ni-(PANI/PU)-Al) in the case of oblique incidence for electrical and magnetic polarization.

In this paper, an array aperture extension algorithm is developed for two-dimensional (2-D) direction-of-arrival (DOA) estimation with L-shaped array. We enlarge the dimension of the covariance matrix by using the rotational invariance in conjunction with the property that the signal covariance matrix is real diagonal matrix. Estimation of DOAs is performed by processing this larger dimensional matrix. The simulation results indicate that our method can improve the DOA estimation accuracy.

A new mathematical approach is proposed to highlight the nonlinear effect in a chiral medium, which is due to the magnetization vector under the influence of a strong electric field. In a chiral media, one can notice the coupling between the electric and magnetic quantities, which appears in the constitutive relations of the medium. According to our proposed approach, we illustrate the existence of the difference between a nonlinear achiral medium and a nonlinear chiral medium, where not only the polarization vector has a nonlinear form but also the magnetization vector. Thus, the nonlinear chiral medium is described by the new constitutive relations D=ε_gE+ε₀μ₀ξ_EHH and B=μH+ε₀μ₀ξ_HE^gE. Therefore, a better fundamental understanding of the interaction between the electromagnetic waves and chiral media can be contemplated.

This letter proposes a novel ultra-wideband (UWB) bandpass filter with compact size and high-selectivity performance. The filter has been studied and implemented through multiple-mode resonator (MMR) using new coupling schemes such as capacitive source-load (S-L) coupling/inductive source-load (S-L) coupling. By properly adjusting the length and width of these stubs, its first four resonant modes can be allocated within the 3.1-10.6 GHz passband, whereas its fifth resonant mode is placed above 16.0 GHz. Two transmission zeros (an inherent transmission zero and an additional transmission zero) can be produced. Moreover, the position of the additional zero can be controlled by adjusting the direct coupling inductance/capacitance. Simulated and measured results are in good agreement indicating that the proposed BPF has a passband (3.0-11.0 GHz)/(2.92-10.6 GHz) and a wide stopband width with 23 dB/25 dB attenuation up to 27.0 GHz. The group delay of the filter is relatively constant and less than 0.65 ns/0.52 ns over the operating pass band.

This paper studies the effect of three important parameters in planar time-domain (TD) near-field (NF) to far-field (FF) transformation. These parameters are the NF spatial sampling, NF measurement distance and scan surface truncation. The effect of these parameters over the TD FF accuracy are difficult to predict for Ultra Wide Band antennas. In this paper we aim to choose the optimum NF measurement parameters guaranteeing accurate calculation of the time-domain far-field. This allows the optimization of the computation time and memory requirements. Computations using analytic array of elementary dipoles radiation pattern are used to study the impact of each parameter in time-domain near-field antenna measurement. The comparison of the far-field results are presented in time and frequency domains. In particular, it is shown that the choice of the measurement distance and the size of the scan surface decide predominantly on the frequency band of accurate FF calculation. The used formalism in this paper for the NF to FF transformation is based on the Green's function.

By virtue of their ability to resonate at a wavelength much larger than the maximum dimension, Split-Ring Resonator (SRR) cells can be densely stacked to create energy harvesting arrays having per-unit-area power efficiency higher than a single SRR cell. While the concept of using metamaterial particles for electromagnetic energy harvesting had been demonstrated in our earlier work, the overall efficiency of an SRR array in comparison to classical antenna arrays is fundamental to the viability of this technology. In this work, we focus on a comparative study based on numerical full-wave simulations where an array of SRRs is compared to an array of microstrip antennas. We show that an SRR array can provide significant enhancement in power efficiency and bandwidth in comparison to the classical microstrip patch antenna. Experimental validation is provided showing SRR arrays can provide significant energy-absorption enhancement.

Crosstalk is one of the bottlenecks for high-speed circuits to increase its rate and density. In order to make tradeoff between complexity and effect of the crosstalk cancellation circuit, a crosstalk cancellation method based on unitary transformation is proposed. In the method, two unitary matrixes are obtained by Singular Value Decomposition (SVD) of coupled transmission lines-channel transmission matrix (CTL-CTM), and then according to the form of the unitary matrixes, the crosstalk canceling circuits are built at both ends of the transmission line, which could transform the CTMes into unit ones and crosstalk would be cancelled out. Circuit simulation results show that at the signaling rate of 5 Gbit/s, jitter performance of eye diagram improves 85% and vertical performance improves 67.5%, which means the method achieves better crosstalk canceling effect with lower circuit cost.

In this paper, the modal theory of antennas is re-visited, believing that it brings invaluable information towards facilitating the design of multi-feed multi-band antennas. First, some subtle changes are proposed to enhance the applicability of thetheory. Next, using some efficient computational techniques, the proposed formulations are shown to predict, to a very high accuracy, the input impedance of any antenna under study. This greatly simplifies the antenna problem and focuses design efforts on finding the appropriate complex resonance frequency to cover a required band. Finding the appropriate feed location is then a matter of extracting the corresponding impedance map for this antenna through simple field manipulations.

A flexible VHF/UHF Vivaldi antenna is proposed. The antenna is realized on 600 × 600 mm² silicone substrate with a thickness of 1.5 mm. The silicone substrate is used due to its low cost, its robustness and its flexibility. The antenna has a 6-dB impedance bandwidth from 150 MHz to 10 GHz. The measurements have shown that the bending slightly affect the impedance and the radiation patterns of the antenna. This last one is used for military applications to receive and find the source of VHF/UHF micro-wave emissions.

This paper presents a new approach for the realization of RF switches based on the Conductive Bridging Random Access Memory technology (CBRAM). This promising approach allows the realization of RF switches in an extremely simple manner at low cost. For the first time, an RF switch based on a MIM structure is realized with an insulator layer obtained from a commonly used resin deposited by spin coating. The paper reports a RF switch based on CBRAM and demonstrates a device integration onto plastic circuit board (PCB). The realized switch is validated by experimental measurements for a frequency range up to 1.5 GHz with an activation voltage less than 1 V.

Based on a proposed inexact Hodge decomposition, this paper describes a viable scheme using the second order finite elements in the T-Ω method considering multiply-connected regions for the eddy current problems. Several numerical examples have been presented to demonstrate the effectiveness of this scheme.

Ring resonators are very commonly used for the design of frequency selective surfaces (FSSs). But, for some particular design, the spacing between the resonators becomes very small. So it leaves no space to shift the reflection band towards the lower side of the spectrum. It also becomes very difficult to realize large PCBs. In this paper, an improvised design of the ring resonator using stubs is reported. This provides the designer with some flexibility. Two different configurations using this concept have been fabricated. Measured results are compared with the configuration using conventional ring resonators. These results indicate good performance with tune-ability in the response without major change in the design or in the substrate.

In this article, the mixed potential integral equation is discretized using the Rao-Wilton-Glisson basis functions in order to obtain a method of moments matrix equation for a source reconstruction problem. The weighting functions used in the setup of the moments equation are Dirac delta functions. The entries of the moments matrix are computed using a semi-analytical method which is applicable to any method of moments problem with point matching. The analytical calculation is made possible by employing a differentiation property of the scalar Green function and the properties of the mesh elements of the source plane. The semi-analytical method makes it easier to increase the accuracy of the moments matrix elements. The accuracy of the method is shown by comparing the results obtained using the semi-analytical method to those obtained by a fully numerical procedure.

The discontinuous Galerkin's (DG) method is an efficient technique for packaging problems. It divides an original computational region into several subdomains, i.e., splits a large linear system into several smaller and balanced matrices. Once the spatial discretization is solved, an optimal time integration method is necessary. For explicit time stepping schemes, the smallest edge length in the entire discretized domain determines the maximal time step interval allowed by the stability criterion, thus they require a large number of time steps for packaging problems. Implicit time stepping schemes are unconditionally stable, thus domains with small structures can use a large time step interval. However, this approach requires inversion of matrices which are generally not positive definite as in explicit shemes for the first-order Maxwell's equations and thus becomes costly to solve for large problems. This work presents an algorithm that exploits the sequential way in which the subdomains are usually placed for layered structures in packaging problems. Specifically, a reordering of interface and volume unknowns combined with a block LDU (Lower-Diagonal-Upper) decomposition allows improvements in terms of memory cost and time of execution, with respect to previous DGTD implementations.

Performance of a harmonic transponder strongly depends on the properties of the antenna and diode used, which makes finding a good combination of them very important. For a transponder with a fixed antenna geometry, the effect of different diodes is analyzed through electromagnetic simulations and theoretical calculations. The antenna used in the transponder is directly matched to the impedance properties of a particular diode. Effects of both detector and varactor diodes on the return loss characteristics of the antenna and the obtainable transponder response are observed. Criteria for selecting a suitable diode are given. Benefits and drawbacks of using different antenna matching techniques are discussed, and principal design steps are given both for transponders matched directly to the antenna and for transponders with external matching circuits.

This paper presents a wideband circular polarization antenna for Global Navigation Satellite System (GNSS). By exciting four slots etched along each edge of a square ground with equal amplitude and 90° phase difference, good circular polarization performance is achieved. A novel radiation element, composed of back-side slot and front-side monopole, is proposed to realize a wideband radiation. Meanwhile, the feed network composed of Schiffman phase shifters and Wilkinson power dividers maintains this wideband performance. A backed cavity is used to suppress the backward radiation, therefore enhances the frontward gain. Measured results of the fabricated antenna show good agreement with the simulated ones. The main advantages of this antenna include its wide bandwidth, good circular polarization, high front to back ratio, low cost, and easy fabrication, which make it very attractive for GNSS terrestrial applications.