Contour reconstruction and accurate identification of dielectric objects placed on a conducting surface are the aims of the millimeter-wave Synthetic Aperture Radar (SAR) imaging processing system presented in this paper. The method uses multiple frequencies, multiple receivers and one transmitter in a portal-based configuration in order to generate the SAR image. Then, the information in the image is used to estimate the contour of the body under test together with the permittivity of the dielectric region. The results presented in this paper are based on synthetic scattered electromagnetic field data generated using an accurate Finite-Difference Frequency-Domain (FDFD)-based model and inversion based on a fast SAR inversion algorithm. Representative examples showing the good behavior of the method in terms of detection accuracy are provided.

This paper introduces a flexible antenna, printed on a low-cost Polyethylene Terephtalate (PET) substrate for UHF applications. The RF characteristics of the PET substrate are examined using a microstrip resonator to characterize the substrate's relative permittivity and the loss tangent at UHF band. The PET substrate is used to print an antenna designed to work in the 868 ISM-Band. The printing process described is carried out using a semi-industrial roll-to-roll (R2R) machine with mass production capability. The fabricated dipole antenna was mounted on cylindrical objects made from several materials such as paper and glass, and its RF characteristics were measured and discussed.

In this paper, reflectarrays mounted on or embedded in cylindrical and spherical surfaces are designed, analyzed, and simulated at 11.5 GHz for satellite applications. A unit cell consists of a square dielectric resonator antenna (DRA) mounted on or embedded in metallic conformal ground plane is investigated. The radiation characteristics of the designed reflectarrays are investigated and compared with that of planar reflectarray. A 13 x 13 planar reflectarray antenna on the x-y plane was designed. By varying the length of the DRA element between 2 mm and 6.2 mm a full range from 0° to 360° phase shift can be obtained. The size of each element is equivalent to a compensation phase shift. A maximum directivity of 24.3 dB was achieved while the side lobes were below -12.94 dB in E-plane and -15.79 dB in the H-plane for planar reflectarray. A Full-wave analysis using the finite integration technique (FIT) is applied. The results are validated by comparing with that calculated by transmission line method (TLM).

Temperature and thermal stress responses of an improved TTSV structure under the impact of hotspots are numerically analyzed in this paper. A Fin structure is added to the circular TTSV to strengthen the effect of thermo-mechanical mitigation. The nonlinear finite element method (N-FEM) is presented to obtain the coupled thermal and mechanical fields. Running time of the N-FEM algorithm is compared with that of commercial software to indicate its efficiency. The model of state-of-the-art 3D Dynamic Random Access Memory (DRAM) is adopted in our simulation. Besides the single-layer TTSV and TTSV array, the extended case of multi-layer TTSVs is also investigated. To take into consideration the nonlinear effects, the temperature dependent results for the issues of hotspot alignment and liner materials selection are provided, both of which are compared with the corresponding temperature independent results. This paper is aimed to provide some practical guidance to the design of TTSV for effective thermo-mechanical management.

In this paper, an efficient method is proposed to reduce the peak transient grounding resistance (P-TGR) of a grounding system. By surrounding the lifting line with a material volume, the P-TGR of the grounding system is greatly reduced. The effect of the surrounding volume conductivity and relative permittivity on the P-TGR is also tested. Second, the rectangular surrounding material volume is shielded with a metallic pipe to reduce the P-TGR further. Third, the shielding metallic pipe is connected to the grounding electrode with thin wire, and the effect of the number of the wires on the P-TGR is also analyzed. It is demonstrated that the P-TGR of the grounding system has been reduced significantly.

A novel band-pass filter (BPF) with lower and upper stopband zeros is proposed. The filter mainly consists of two antisymmetric modified anti-parallel coupled-lines and double pairs of transmission lines. Compared with the traditional anti-parallel coupled-line, the new filter has a better performance at both pass band and stop band. On the basis of even-odd mode method and network theory, the filter has been analyzed in detail. In addition, a simple method to create transmission zeros is investigated, which is beneficial for controlling the stopband zeros. The proposed filter is implemented on RT/Duroid 4350 substrate. Measured results show low insertion loss of less than 1.6 dB in the pass band and good suppressing of more than 22 dB in the lower stop band. Measured results show a good agreement with simulated results.

An overall Low-Temperature Co-fired Ceramics (LTCC) package solution for X-band T/R module has been presented in this paper. This tile type package contributes to a dramatic reduction in size and weight of the T/R module. Moreover, an obvious merit of ceramic housing is better consistency of Coefficient of Thermal Expansion (CTE), compared with the traditional combination of ceramic board and metal housing. The schematic diagram and 3-D structure of the T/R module have been presented and a novel vertical interconnection based on Ball Grid Array (BGA) has been proposed to connect vias in the lid and those in the stage of the main LTCC pan. The LTCC T/R module has been fabricated and measured. It is compact in size (20×20× 2.6 mm³) and has a weight of 3.5 g. The measured transmit output power is 33±1 dBm in the frequency range from 8.8 GHz to 10.4 GHz, and the measured receive gain and Noise Figure are 29-30.5 dB and 2.6-2.8 dB, respectively.

A wideband dual-polarized antenna with high isolation is presented. Four printed quadrant planar folded dipole placed above a U-shaped reflector are adopted as the main radiation elements. Curved slots cut on the planar folded dipole are used to reduce the size of the antenna. Parameter is studied, and the values are adjusted in order to obtain wideband and compact properties. Measured results show that the antenna achieves a VSWR < 2.0 from 1.64-2.33 GHz. The isolation between the two polarizations is better than 29.5 dB. The radius of the quadrant planar folded dipole is only 34 mm (about 0.18 wavelength at 1.64 GHz).

The improved configurations with dual-mode double-square-loop resonators (DMDSLR) for tri-band application are proposed in this paper. Two sets of loops including double-square-loop and G-shaped loop are involved in the resonators. The resonant frequency equations related to DMDSLR geometries are introduced for simply designing tri-band bandpass filter (BPF). Resonant frequencies and transmission zeroes can be controlled by tuning the perimeter ratio of the square rings and the couples. To obtain lower insertion loss, higher out-of-band rejection level, wider bandwidth of tri-band, and compact applications, the miniaturized DMDSLR structure is designed. The effective design procedure is provided. The proposed filter is successfully simulated and measured. It can be applied to WLAN (2.45, 5.20 and 5.80 GHz) and WiMAX (3.50 GHz) systems.

Inverse synthetic aperture radar (ISAR) imaging is one of the most well-known techniques of radar target recognition. One of the most important issues in ISAR imaging is the improvement of the image smeared by a target with complicated motion. In this paper, we propose the discrete Gabor representation (DGR) in an oversampling scheme as an effective means of obtaining a well-focused ISAR image with a short calculation time. In contrast to other linear time-frequency transforms, the DGR obtains Gabor coefficients using the analysis window frames derived from the clearly defined synthesis window. The oversampling scheme of the DGR leads to accurate calculations of the Gabor coefficients, which denote signal time-frequency amplitude. Since each Gabor coefficient is compartmentally assigned to the associated unit cell of the time-frequency grid, the DGR can show an excellent time-frequency concentration and can effectively discriminate the Doppler components of prominent point-scatterers. The simulation results demonstrate that the DGR not only has enhanced focusing performance but also retains computational efficiency. The DGR in the oversampling scheme is expected to facilitate high-quality ISAR imaging in radar target recognition.

We consider MUltiple SIgnal Classification (MUSIC)-type imaging of perfectly conducting cracks arising in inverse scattering problems. We first explore the structure of a MUSIC-type imaging function by finding a relationship between it and the Bessel function of order zero of the first kind. Then, we design multi-frequency based MUSIC-type imaging in order to improve the traditional one, and establish a relationship with the Bessel function of integer order of the first kind. Some numerical experiments are presented to support the results of our investigation.

We propose a loop switching technique to improve the efficiency of wireless power transfer (WPT) systems using magnetic resonance coupling. The proposed system employs several loops with different sizes, one of which is connected to the system with various distances between the transmitter and the receiver. It enables the coupling coefficient to be adjusted with the distance, which allows high efficiency over a wide range of distances. The proposed system is analyzed using an equivalent circuit model, and electromagnetic (EM) simulation is performed to predict the performance. It is shown from the experimental results at 13.56 MHz that the proposed loop switching technique can maintain high efficiency over a wide range. The efficiency is measured to be 50% at 100 cm, which corresponds to a 46% increase compared to a conventional WPT system without the loop switching technique.

This paper presents herein experiments and calculations of electromagnetic induction between jointless track circuits (JTCs) and track-circuit readers (TCRs). The paper uses transmission-line theory to simulate JTC currents ahead of shunt points and electromagnetism to calculate voltages induced in the TCR antenna. Based on these calculations, the JTC-to-TCR range is defined. The paper derives expressions for the amplitude and phase of the voltage induced in the TCR antenna by the JTC current and uses them to quantitatively analyze the train control system. Experiments verify the conclusions reached based on the calculations.

The Debye expansion integrals obtained by application of the Modified Watson Transformation and Debye series expansion to the Mie series for the high frequency plane wave transmitted into a double negative(DNG) cylinder are solved in the geometrically lit regions of the corresponding Debye series terms. The Debye series expansion is made up to the possible maximum term after which double ray field formation is first observed. Using the steepest descent method and the geometrical optics approximation, the role of the lower ray in the double-ray field formation is pointed out. For refractive indices satisfying |n| ≥ 10, it is shown that the maximum Debye series term index up to which simple single-ray tracing can be performed is bigger for a DNG cylinder than that for a DPS cylinder and the difference between the term indices incrases as |n| increases.

In this paper, a miniature ultrawideband (UWB) bandpass filter with dual notch bands and wide upper stopband is presented. The ultrawide passband characteristic is achieved using a microstrip to slot line transition, and a wide upper stop band is realized using an elliptical lowpass filter. The dual band notches at 5.46 GHz and 8.04 GHz are obtained by incorporating defected microstrip structure in the input and output section. A prototype of the proposed UWB bandpass filter is fabricated and measured. The equivalent circuit of the proposed filter is also presented. A good agreement between the measured, EM simulated and circuit simulated responses is obtained.

We present a dualband terahertz metamaterial based on a hybrid 'H'-shaped cell of different sizes. The proposed 'H'-shaped metamaterial (HSM) structure, fabricated on a quartz (SiO₂) substrate, exhibits two intense electrical resonances at ~0.95 THz and ~1.26 THz, respectively. Extracted effective permittivity show negative values in 0.95-1.01 THz and 1.26-1.42 THz bands. Measured results from the terahertz time-domain spectroscopy (THz-TDS) experiments show good agreement with the simulated results.

The wideband and omnidirectional performance of a printed dipole antenna with a novel coupling feed structure is presented. Besides using printed dipole for omnidirectional radiation patterns, the coupling feed structure, which includes the transmission line coupling to a slot line to effectively improve the impedance matching, can be used for bandwidth enhancement. A wideband impedance characteristic of about 45.6% for VSWR ≤2 ranging from 1.54 to 2.45 GHz is obtained. The omnidirectional radiation patterns in the whole operation bands are achieved which the un-roundness in H-plane is less than 1.6dB. It is sufficient for accommodating recent wireless communication services such as DCS1800, PCS1900, UMTS, IMT2000, Wibro, etc. Furthermore, the proposed antenna should be a good candidate as a unit of the omnidirectional array. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

A novel microwave filter tuning method based on vector fitting and aggressive space mapping (VF-ASM) technology is presented in this paper. The filter tuning is performed as a two step procedure. First, the equivalent circuit parameters are extracted through vector fitting method by a series of S-parameter measurements. Second, the optimal screw positions are calculated through ASM techniques. this novel tuning technique has been tested successfully with cross-coupled six-resonator and direct coupled eight-resonator filters.

Ultra-wideband synthetic aperture radar (UWB SAR) is a sufficient approach to detect landmines over large areas from a safe standoff distance. Feature extraction is the key step of landmine detection processing. On one hand, the feature vector should contain more scattering characteristics to discriminate landmines from clutters; on the other hand, the dimension of feature vector should be lower to avoid the "curse of dimensionality". In this paper, a novel feature vector extraction method is proposed. We first obtain the scattering information in the four-dimensional domain, i.e., range, azimuth, frequency and aspect-angle, via the space-wavenumber distribution (SWD). Since the data after SWD are with higher dimension and local nonlinear structures, a typical manifold learning method, Isomap, is used to reduce the dimension. The validity of the proposed method is proved by using the real data collected by an airship-borne UWB SAR system.

Switch mode power amplifiers offer high efficiency approaching 100% for an ideal case. This paper discusses the operation mode of broadband switch mode class-E power amplifier designed previously by the authors for UHF applications (600-1000 MHz). A method to extract the waveforms at the die reference plane from the time domain analysis using 50 Ω environment systems is discussed. It has been observed that the designed class-E power amplifier operation was not maintained ideally over the entire band; however, it was operating close to the class-E operation.