We numerically demonstrate that the transmission through a deep subwavelength (λ₀/20) aperture in a metal plate could be greatly enhanced owing to the resonance effects of a high permittivity (κ) dielectric cube tightly coupled to the aperture. The transmission enhancement originates from the confinement and re-radiation of the electromagnetic energy impinging onto the high κ cube which operates in the 1st Mie resonance mode, and behaves as an ultra-small magnetic dipole antenna. The complex permittivity of the cube governs the operating frequency and the enhancement in terms of bandwidth and transmissivity maximum. Additionally, based on the isotropic response of the high κ cube with dimensions comparable to the aperture size, the almost independence of the enhancement properties on the illumination polarization and incidence angle was assessed.

Frequency-dependent admittance (J-) inverter is incorporated in synthesis of microstrip trisection filters to achieve a quasi-elliptic function response. In the admittance matrix of the lowpass prototype, certain coupling is modeled by a constant J-inverter multiplied by the complex frequency variable s. Direct synthesis of three lowpass prototypes is presented. Based on the standard lowpass to bandpass transformation, coupled microstrip resonators with both electric and magnetic coupling are devised to implement the J-inverter with desired frequency-dependent characteristics. Tapped-line input/output is used and several transmission zeros can be created in the upper and lower rejection bands. In experiments, a third-order filter with four zeros, a fourth-order circuit with three zeros, and a fourth-order filter with five zeros are designed and fabricated. Measured results are compared with the simulation responses to validate the theory.

Highly dense two-dimensional periodic arrays of nano-scaled silicon pillars present interesting photonic band gaps and the capacity to act as photonic crystals which can mould, manipulate and guide light. We demonstrate finite element modelling of silicon pillars based photonic crystals and their effective use in applications like waveguides, optical power dividers, multiplexers and switches. The optical wave propagation through these structures was thoroughly simulated and analysed, confirming their high efficiency. The band gaps studied through the plane wave expansion method are also presented. Later the fabrication of highly periodic two-dimensional arrays of silicon pillars through the process of etching is also explained. The arrays with pillar radius of 50 nm and lattice constant of 400 nm were successfully utilised as photonic crystal waveguides and their measured results are reported. Moreover, the silicon nanopillars sputtered with noble metals can also display artificial optical properties and act as metamaterials due to the mutual plasmonic coupling effects. We report the theoretical results for the silicon nanopillars based metamaterial high-pass filter.

We propose two metamaterials with sub-wavelength double-slots --- single-side double-slot metamaterial and double-side double-slot metamaterial. The dependence of the electromagnetic resonances and local intensity enhancements on the structural parameters is studied by the finite-difference time-domain technique and the finite element method. Results show that the central-arm of a double-slot structure strongly influences frequency and local intensities at both high- and low-frequency resonances. Very strong field localization can be achieved at the high-frequency resonance and its particular distribution can be well controlled by the width of the central-arm. A double-side double-slot structure can be utilized to separately enhance the high-frequency resonance, while suppressing the low-frequency resonance. The simulation results are discussed in terms of plasmon resonances.

This paper proposes two novel broadband microstrip antennas using coplanar feed-line. By feeding the patch with a suitable shape of the coplanar line in the slot of the patch, the broadband character is achieved. Compared with the antenna fed by a U-shaped feed-line, the antenna with L-shaped feed-line not only has wider bandwidth but also achieves the circular polarization character. The measured bandwidths of 25% and 34% are achieved, and both of the antennas have good radiation characteristics in the work band.

Light concentrating structures with three-dimensional photonic crystals (3D PhCs) for solar cell applications are investigated via simulation. The 3D opal PhCs are suggested as an intermediate layer in the concentrator system for solar cells. It is found that the light absorption is significantly enhanced due to the adding of diffractive effects of PhCs to the concentrator. Three types of PhCs are considered in four scenarios to verify the absorption enhancement by such a light concentrating structure. Our calculations show that the face-centered cubic PhC can create an absorbing efficiency superior to the others under a specified lattice orientation pointing to the sun, which results in an enhancement factor of 1.56 in absorption for the 500--1100 nm spectral range.

The integral equation fast Fourier transform (IE-FFT) is a fast algorithm for 3D electromagnetic scattering and radiation problems based on the interpolation of the Green's function. In this paper, a novel floating interpolation stencil topology is used to improve the IE-FFT algorithm. Compared to the traditional interpolation stencil topology, it can further reduce the storage and CPU time for the IE-FFT algorithm. The reduction is especially significant for volume integral equations. Furthermore, the accuracy of the algorithm is still good though the near-interaction element numbers are reduced. Finally, some numerical results including perfectly electric conductors, dielectric objects, composite conducting and dielectric objects are given to demonstrate the performance of the present method.

Wideband analysis of frequency dispersive geometries is a challenge in inverse scattering problems. Waveguide duct is an important case in aerial targets with dominant returns. Its dispersive behavior affects the range profile analysis due to occurrence of unwanted range extension. A new high frequency analysis using model based parameter estimation (MBPE) approach is presented. A group delay criteria derived from the nonlinear scattering phase response represents the duct length. Wideband sparse measured frequency domain samples of various waveguides are used as inputs to the model. Comparison is made with joint time-frequency analysis (JTFA) and inverse fast Fourier transform (IFFT) results.

In this paper, we propose a computational method for computing RCS of 3D conductor, by using piecewise surface impedance boundary conditions and forward backward iterative scheme. In our previous work, we have reported a numerical method combining Rytov's perturbation method and level set technique to construct a piecewise surface impedance, we showed that by using level set technique, we could model an arbitrarily shaped conductor by a piecewise distribution of low- and high-order SIBCs. The method proposed in this article postulates the use of local "buffer regions" to suppress spurious edge effects introduced by the abrupt termination of each SIBC and ensure stability of RCS computing.

A system has been developed for measuring the complex permittivity of low loss materials at frequencies from 500 MHz to 7 GHz and over a temperature range up to 1500°C using stripline resonator cavity method. Details of the design and fabrication of the cavity were discussed. Particular features related to high-temperature operation were described. An improved resonance method at high temperature for determining complex dielectric properties of low-loss materials was developed. The calculation process was given by a physical model of the stripline resonator cavity at high temperature. The paper brought forward the method of segmentation calculation according to the temperature changes over the cavity, which matched the actual situation of high temperature measurements. We have verified the proposed method from measurements of some typical samples with the available reference data in the literature.

This paper presents the design of Dielectric Resonator Antenna (DRA) operating at 5.8 GHz, using the techniques of Two Segments DRA (TSDRA) and High-Aspect Ratio Structure. The aim of the paper is to reduce the size of the DRA while still maintaining its large impedance bandwidth. The requirements for WLAN applications are carefully taken into considerations in the design of the proposed structure. Comparison has been made between the proposed design and single layer DRA (SLDRA); and it has been found that former has better performances than the later.

In this paper, a novel technique is proposed to solve the electromagnetic scattering by large finite arrays by combining the tangential equivalence principle algorithm (T-EPA) with multilevel fast multipole algorithm (MLFMA). The equivalence principle algorithm (EPA) is a kind of domain decomposition scheme for the electromagnetic scattering and radiation problems based on integral equation (IE). For the array with same elements, only one scattering matrix needs to be constructed and stored. T-EPA has better accuracy than the original EPA. But the calculating for the impedance matrix in T-EPA is still time consuming. MLFMA is proposed to speed up the matrix-vector multiplication in T-EPA. Numerical results are shown to demonstrate the accuracy and efficiency of the proposed technique.

A synthesis procedure is developed in this paper for the design of N-step coplanar waveguide-to-microstrip transitions. An equivalent circuit approach is adopted to model the structure in terms of N cascaded ABCD matrices relative to the N coplanar waveguide sections forming the transition. A constrained optimization problem is formulated as the minimum finding of a proper functional to accurately determine the transition dimensions by imposing an upper bound to the return loss within a prescribed frequency band. An iterative N-step procedure is developed to find the optimization problem solution. Numerical results on millimeter-wave transition configurations are provided to demonstrate the effectiveness of the proposed synthesis method. A back-to-back transition prototype with N=3 sections is then fabricated and characterized in terms of measured S-parameters to experimentally demonstrate a return loss better than 10 dB in the frequency range from 1 GHz up to 40 GHz.

The design and realization of a multi-band and polarization insensitive metamaterial absorber is presented. The structure with thickness 1.1 mm consists of six close rings which distribute in two metallic layers separated by FR4 substrates. Experimental results show that over 93.3% absorption can be achieved in this metamaterial absorber at multiple frequency bands (more than two). Due to the rotational symmetric pattern of the metamaterial, the performance of the absorber is insensitive to the polarization of the incident waves, indicating the superiority of the structure in the application.

In this paper, we analyze the behaviour of a switched mode power supply (SMPS) regarding the radiated magnetic nearfield through an initial understanding of the electrical working of the converter, particularly during switchings. We propose a method based on impedance analysis at each state of the converter in order to predict the resonances of currents and/or voltages in the SMPS at the origin of the magnetic radiated near-field.

A compact helix structure implementation and associated design formula of lumped element second-order bandpass filter circuit for high power frequency-hopping filter are proposed in this paper. The filter schematic provides one, two or three finite transmission zeros (Tzs), and these Tzs locates in the upper stopband to improve the rejection above the center frequency, especially the suppression of second harmonic with two Tzs. The filter schematic is built on a common grounded helix coil of inductive coupled resonator tanks whose suspectance is tunable. Due to the parasitical capacitance of the helix coil, the filter has a feedback capacitor between input and output. Its working mechanism is revealed both mathematically and graphically. The measured results have a good agreement with the 3D full-wave electromagnetic simulation responses. The experimental filter has a insert loss < 1.5 dB , return loss > 15 dB, a 3-dB bandwidth of 5%~8.5% over entire operating range with the power handling capability greater than 49 dBm and the suppression of second harmonic better than 56 dB.

The package design for microwave sub-systems requires adequate knowledge of electromagnetic field distribution inside the package housing. The cavity resonance of the microwave amplifier not only degrades the electrical performance, the feedback through the resonance mode also can cause unwanted oscillation in the frequency band of interest. It may even result in catastrophic failure of the device, wherein the peak oscillating voltage exceeds the device breakdown voltage. Hence, comprehensive analysis of the package effects is one of the prime requirements for stable microwave amplifier design for high-rel applications. This paper describes modeling, analysis of the package and different mitigation techniques to make stable, resonance free microwave amplifier for a C-band spaceborne SAR payload.

This paper presents a novel 10 GHz bio-radar system based on a frequency multiplier and phase-locked loop (PLL) for non-contact measurement of heartbeat and respiration rates. In this paper, a 2.5 GHz voltage controlled oscillator (VCO) with PLL is employed as a frequency synthesizer, and 10 GHz continuous wave (CW) signal is generated by using frequency multiplier from 2.5 GHz signal. This paper also presents the noise characteristics of the proposed system, and the analysis result shows that the same signal-to-noise-ratio (SNR) performance can be achieved with the proposed system based on the frequency multiplier compared with the conventional system with identical carrier frequency. The experimental results shows excellent vital-signal measurement up to 100 cm without any additional digital signal processing (DSP), thus proving the validity of the proposed system.

In spaces with Finslerian geometry, the metric tensor depends on the directional variable, which leads to a dependence on this variable of the electromagnetic tensor and of the 4-potential. In this paper, we investigate some of the consequences of this fact, regarding the basic notions and equations of classical electromagnetic field theory.

In this paper, we will propose a new structure of the socket contactor, which is applied to the lead-frame test board. This structure contains a variable open stub to suffice for matching the impedance between the package and the load board. Its electrical property is considered superior to a conventional spring probe's especially when it is applied to a QFP device. In the following paragraphs, we will present its equivalent model and go into details. Note that the transmission-line model is a substitute for a physical structure at this point. First of all, its RLC model will be constructed after we demonstrate its simulation and test data. Finally, we will use the so-called MonteCarlo Method to analyze the inaccurate length in manufacturing to see how this new structure works.