Three horizontally-polarized (HP) omnidirectional antennas are proposed and discussed in this paper. The antennas are composed of 3, 4 or 5 printed dipoles with corresponding wideband 3-, 4- or 5-way feeding networks. The feeding networks are simple in structure and easy to be matched with the printed dipoles. All of the proposed antennas operate in the frequency band of 1.7-2.7 GHz, covering the DCS1800, WiFi2700 and 4G-LTE bands with reflection coefficients less than -15 dB. Effects of the number of the printed dipoles on omnidirectional characteristics are discussed. Crossed strips are applied to improve their cross-polarization performance. The proposed antennas are simulated, fabricated and measured. Both simulated and measured cross-polarization levels are lower than -15 dB from θ=60° to θ=120° conical cuts. The antennas demonstrate good omnidirectional patterns in the whole frequency band, which can be widely used for indoor 4G-LTE indoor distributed antenna system (DAS) applications.

For the radiation problem of multi-antenna on electrical-large platform, a multi-region MoM-PO (Multi-MoM-PO) is firstly proposed in this paper. The conventional MoM-PO generally treats all the antennas as a whole MoM region, but in the Multi-MoM-PO, each antenna is classified as one MoM region. On the basis of the mutual interaction between each MoM region and PO region, the self-interactions among MoM regions are considered. Numerical examples demonstrate that the multi-region technique can effectively boost the efficiency of impedance matrix filling compared with the conventional MoM-PO. Finally, the dependence of the filling efficiency against the number of antennas on platform is discussed.

Magnetic induction tomography (MIT) is a non-invasive medical imaging technique with promising applications such as brain imaging and cryosurgery monitoring. Despite its potential, the realisation of medical MIT application is challenging. The computational complexity of both the forward and inverse problems, and specific MIT hardware design are the major limitations for the development of MIT research in medical imaging. The MIT forward modeling and linear system equations for large scale matrices are computationally expensive. This paper presents the implementation of GPU (graphics processing unit) for both forward and inverse problems in MIT research. For a given MIT mesh geometry composed of 167,488 tetrahedral elements, the GPU accelerated Biot-Savart Law for solving the free space magnetic field and magnetic vector potential is proved to be over 200 times faster compared to the time consumption of a CPU (central processing unit). The linear system equation arising from the forward and inverse problem, can also be accelerated using GPU. Both simulations and experimental results are presented based on a new GPU implementation. Laboratory experimental results are shown for a phantom study representing potential cryosurgery monitoring using an MIT system.

The aim of angular super-resolution is to surpass the real-beam resolution. In this paper, a method for forward-looking scanning radar angular super-resolution imaging through a deconvolution method is proposed, which incorporates the prior information of the target's scattering characteristics. We first mathematically formulate the angular super-resolution problem of forward-looking scanning radar as a maximum a posteriori (MAP) estimation task based on the forward model, and convert it to an equivalent unconstrained optimization problem by applying the log-transforms to the posterior probability, which guarantees the solution converges to a global optimum of an associated MAP problem and it is easy to implement. We then implement the unconstrained optimization task in convex optimization framework using an iterative shrinkage method, and the computational complexity of the proposed algorithm is also discussed. Since the anti log-likelihood of the noise distribution and the prior knowledge of the scene are utilized, the proposed method is able to achieve angular super-resolution imaging in forward-looking scanning radar effectively. Numerical simulations and experimental results based on real data are presented to verify that the proposed deconvolution algorithm has better performance in preserving angular super-resolution accuracy and suppressing the noise amplification.

Microwave induced thermo-acoustic tomography (MITAT) is a developing technique for biomedical applications, especially for early breast cancer detection. In this paper, impacts of short microwave pulse on thermo-acoustic (TA) signals are analyzed and verified through some experimental comparisons. In these experiments, short microwave pulses with widths of 10 ns and 500 ns are employed as radiation resources. TA signals generated from a cubic sample are analyzed in both time- and frequency-domain. A trapezoid sample is also performed for experimental comparing. Different from previous literature, the effects of rising edge of radiation microwave pulse have been intensively studied. Experimental results demonstrate that shorter rising edge duration conducts broader bandwidth of TA signal, which give rise to better spatial resolution for tomography imaging.

A novel triple-band filter using triple-mode substrate integrated waveguide (SIW) resonator is presented in this paper. The proposed resonator consists of a square cavity with two additional metallic vias that split the first pair of degenerate modes (TE₂₀₁ and TE₁₀₂) at the diagonal of the cavity. Triple-band response is achieved by TE₁₀₁, TE₂₀₁ and TE₁₀₂. The center frequencies of the first band and the third band can be controlled by appropriately adjusting the location of perturbation vias, while the second band keeps almost unchanged. A two-pole triple-band filter with two transmission zeros utilizing the coupled triple mode cavity resonators is designed and fabricated. The measured results agree very well with the simulated ones.

We deal with the problem of determining the profile of a perfectly conducting rough surface from single-frequency and multistatic data. The two fundamental polarizations are investigated, in a two-dimension scattering configuration. Emitting and receiving antennas are positioned on a probing line some wavelengths above the profile. It is shown how the boundary integral equation method can be adapted to the case where the antenna footprint is much wider that the rough part of the profile. The Newton-Kantorovich iterative inversion process is then performed on these synthetic data. Its accuracy and robustness to additive noise are studied in the context of random rough surfaces with correlation length smaller than the wavelength and slope root mean square up to 0.9.

We develop a semi-analytical approach to calculate the polarizability tensors of an arbitrary scatterer. The approach is based on numerical integration from induced charges and currents on the scatterer. By taking the advantages of the present approach, we calculate the polarizability tensors of any arbitrary scatterer in a homogeneous isotropic medium. This approach, in comparison to other reported approaches, is simple, easily implemented, and does not require spherical harmonic expansion or complicated far-eld calculations. We examine the validity of the approach using several examples and compare the results with other approaches.

Realizations of celestial objects in the laboratory have been a tantalizing subject for human beings over centuries. In this paper, we review some of the interesting cases of realizations of black holes in the laboratory. We first review the recent progress in observed black holes realized through the isotropic coordinate transformation method, then discuss the realization of optical attractors. Finally, the Rindler space-time, as a one-dimensional black hole, by using the hyperbolic metamaterials, is discussed.

It is known that slabs of wire media - dense arrays of thin conducting wires - can transport electromagnetic energy of evanescent plane waves over the slab thickness. This phenomenon was successfully used in superlenses and endoscopes. However, in the known configurations the effective energy transfer takes place only at the Fabry-Perot (thickness) resonances of the slab, making broadband power transfer impossible. In this paper we experimentally demonstrate that power transfer by a wire medium slab can be very broadband, whereas the Fabry-Perot resonances are damped, provided that the wires of the wire medium slab extend into the power-emitting body. As a testbed system we have used two rectangular waveguides and demonstrated that a properly designed and positioned wire medium slab transfers modes of any polarization from the input to the output waveguides. This study is relevant to emerging applications where broadband transport of reactive-field energy is required, especially in enhancing and controlling radiative heat flows in thermophotovoltaic systems.

An efficient quantum mechanical approach is formulated to model electron-photon interactions in nanoscale devices. Based on nonequilibrium Green's function formalism, electron-photon interactions and open boundaries in the nanoscale systems are taken into account in terms of self-energies. By separating different components in the electron-photon interactions, optical absorption and emission processes in the devices can be analyzed, and the method allows studies of different optoelectronic devices. In conjunction with density-functional tight-binding method, photo-induced current and other optical properties of nanoscale devices can be simulated without relying on empirical parameters. To demonstrate our approach, numerical studies of gallium nitride nanowire solar cells of realistic sizes are presented.

An X-band radiator as an open-ended waveguide with a hybrid dielectric insert is proposed. The insert is in the form of a parallelepiped, which fills the entire cross section of the waveguide and constitutes a Teflon matrix with local inhomogeneities in the form of dielectric cylinders with a different permittivity. The design allows for forming various near-field distributions and, hence, the radiator performance by means of definite combinations of the local inhomogeneities can be modified. A number of configurations in the location of air and quartz cylinders are investigted. The calculated and experimental results are in good agreement. The proposed approach to the near-field formation of the aperture antenna is promising, because the variety of possible configurations in the location of local inhomogeneities with different permittivity provides new opportunities in terms of designing both single radiators and antenna arrays.

For wideband common-mode noise suppression in high-speed differential signals, a low-cost compact filter is proposed and designed by etching two coupled C-slotlines on the ground plane. It is found that the bandwidth of the common-mode stopband over -10 dB is from 2.4 GHz to 6.35 GHz with no degradation of the differential-mode insertion loss and group delay within the wide common-mode stopband. In time domain, the differential signal eye diagram is not deteriorated as well. In addition, an equivalent circuit model is developed and provides a quickly prediction of the common-mode stopband. The results show a good consistency between the simulations and measurements.

This work investigates an adaptive, parallel and scalable integral equation solver for very large-scale electromagnetic modeling and simulation. A complicated surface model is decomposed into a collection of components, all of which are discretized independently and concurrently using a discontinuous Galerkin boundary element method. An additive Schwarz domain decomposition method is proposed next for the efficient and robust solution of linear systems resulting from discontinuous Galerkin discretizations. The work leads to a rapidly-convergent integral equation solver that is scalable for large multi-scale objects. Furthermore, it serves as a basis for parallel and scalable computational algorithms to reduce the time complexity via advanced distributed computing systems. Numerical experiments are performed on large computer clusters to characterize the performance of the proposed method. Finally, the capability and benefits of the resulting algorithms are exploited and illustrated through different types of real-world applications on high performance computing systems.

Efficient and accurate computer simulation of wave phenomena plays an important role in invention, development, cost reduction and optimization of many systems ranging from ultra-high-speed electronics to delicate nanoscale optical devices and systems. Understanding the physics of many modern technological applications such as optical nanomaterials calls for the solution of very complex computer models involving hundreds of millions to billions of unknowns. Integral equation (IE) methods are increasingly becoming the method of choice when comes to numerical modeling of wave phenomena for various reasons specifically since the introduction of FMM and MLFMA acceleration that tremendously reduce the computational costs associate with naive implementation of IE methods. In this work, a new acceleration technique specifically designed for the modeling of large, inhomogeneous, finite array problems it introduced. Specifically we use the new method for modelling and design of some metamaterial structures. At last, the presented method is used to study the some of the undesired random effects that occur in metamaterial array fabrication.

This paper presents a compact 2.45 GHz single feed directional circularly polarized (CP) microstrip antenna for radio frequency identification (RFID) applications. The proposed antenna comprises a dodecagonal microstrip patch embedded with an irregular polygonal slot, fabricated on an FR4 substrate. Two antennas, one with right-handed circular polarization (RHCP) and the other with left-handed circular polarization (LHCP), both resonating at a frequency of 2.45 GHz are presented. The measurement results show a 3 dB axial ratio bandwidth of 5.5%, a 10 dB impedance bandwidth of 5.7% for both the antennas, a peak gain of 4.82 dBi for RHCP antenna and 4.67 dBi for LHCP antenna. In addition, the antennas provide symmetrical patterns with 88˚ half-power beam width. The overall size of the antenna is 50 mm × 50 mm × 1.6 mm and offers an area reduction of 21.17%.

A new design of dual-band L1/L2 GPS antenna is proposed. The antenna generates dual-band circularly polarized radiation by exciting a cross-slot and ring-slot of a concentric circular aperture using a proximity-coupled feed. Parametric studies show that the matching and axial ratio bandwidth of L1 (1.575 GHz) and L2 (1.227 GHz) bands can be independently tuned by alternating the ring radius and slot length. The range of frequency ratio and 3 dB center frequency can be highly adjusted by slot's parameters. The size of the antenna is 73 mm × 73 mm × 6.4 mm including the ground, corresponding to 0.29λ × 0.29λ × 0.026λ at 1.227 GHz.

A new compact microstrip UWB bandpass filter with triple band-notched characteristics is presented in this paper. The initial circuit topology and its corresponding electrical parameters of the basic microstrip UWB BPF are desired by a variation of genetic algorithm (GA) technique. Then, triple-notched bands inside the UWB passband are implemented by coupling a novel triple-mode stepped impedance resonator (TMSIR) to the main transmission line of the basic microstrip UWB BPF. The triple-notched bands can be easily generated and set at any desired frequencies by varying the designed parameters of TMSIR. To illustrate the possibilities of the new approach, a microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 5.2 GHz, 6.8 GHz, and 8.0 GHz is designed and fabricated. Measured results agree well with the predicted counterparts.

By using a composite coupling structure for coplanar waveguide (CPW)/microstrip, a new dual-band bandpass filter (DBBPF) stacking inverted Y-shaped CPW resonators and rectangular ring resonators is proposed. Two resonant frequency bands are simultaneously excited by the CPW feed line, However, it can be convenient to tune individually. Several transmission zeros are realized to improve the selectivity of the filter and achieve wide stopband rejection. Good agreement between simulated and measured results demonstrates the validity of this DBBPF.

A broadband Fabry-Perot cavity antenna (FPCA) operates at Ka band with high gain and dual-polarization is reported. The proposed antenna employed a double-sided complementary-circular partially reflective surface (PRS) to enhance the directivity bandwidth. A square patch coupled by two orthogonal slots and fed by two microstrip lines was applied as the primary feed to achieve dual-polarization operation. To further improve the impedance bandwidth and directivity, a series of metal vias were suggested to surround the primary patch. This FPCA design was verified by the measurements. The experimental results show that the common impedance bandwidth of the two ports for the reflection coefficient (S₁₁) below -10 dB is 2.5 GHz from 34 GHz to 36.5 GHz (7.1%), which covers the common 3 dB gain bandwidth of the two ports. At the center frequency of 35 GHz, the measured peak gains at the two orthogonal ports are 16.1 dBi and 15.1 dBi, respectively. The isolation between the two ports is higher than 30 dB within the bandwidth.