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The matrix form of the reciprocity relationship for the ABCD matrix of a general distributed microwave circuit featuring multiple ports is revisited. The correct reciprocity relationship is used to identify mistakes previously made in the derivation of key relations in the vector-short-open-calibration (VSOC) deembedding methodology, which is commonly used for removing the effect of port discontinuities in the Method-of-Moments-based electronic design automation (EDA) models of microwave circuits, digital interconnects, and other structures. Numerical results demonstrating the impact of the incorrect reciprocity relation on the accuracy of VSOC deembedding are provided.

This article presents for the first time the advantages of performing soil resistivity measurements with electrode arrangements different than in a straight-line. The obtained results evidence several benefits in common challenging field situations, such as producing longer traverses in a confined area, combining different measurement methodologies in a single traverse, and obtaining more measurement points than for a single array configuration.

A new integral formulation is introduced to compute the electromagnetic (EM) fields scattered by a vertically stratified half-space. The proposed approach is applied to lossless media illuminated by an electromagnetic plane wave. The computed results are compared with those obtained by the physical optics method.

This paper presents an analysis of high-voltage direct current sea electrodes using different numerical techniques. The large volume of sea water that must be included in the analysis is represented using infinite (inclined layer model) and finite models (finite volume and hemispheroidal models). The comparison between the results obtained using these models is based on the potential rise of the electrode, the sea potential rise in the vicinity of the electrode, and the computational burden for utilizing each model. The analysis shows that the results obtained using finite models can predict the performance of the electrode more accurately and realistically.

This paper presents a method of analysis of grounding systems located inside or near a hemi-oblate spheroidal soil heterogeneity. This type of soil is particularly useful for modeling grounding grids close to certain types of finite inhomogeneities, such as lakes or some types of backfill materials. The developed analytical framework is based on a moment method and involves solving Poisson's equation in an oblate spheroidal coordinate system. Computation results obtained using this modeling approach for several electrodes and hemispheroidal geometries are compared with those obtained using other numerical and analytical techniques. In all cases, good agreement has been achieved.

Near-field radiofrequency thermoacoustic (NRT) tomography is a new imaging method that was developed to mitigate limitations of conventional thermoacoustic imaging approaches, related to hard compromises between signal strength and spatial resolution. By utilizing ultrahigh-energy electromagnetic impulses at ∼20 ns duration along with improved energy absorption coupling in the near-field, this method can deliver high-resolution images without compromising signal to noise ratio. NRT is a promising modality, offering cost-effectiveness and ease of implementation and it can be conveniently scaled to image small animals and humans. However, several of the performance metrics of the method are not yet documented. In this paper, we characterize the expected imaging performance via numerical simulations based on a finite-integration time-domain (FITD) technique and experiments using tissue mimicking phantoms and different biological samples. Furthermore, we show for the first time whole-body tomographic imaging results from mice, revealing clear anatomical details along with highly dissipative inclusions introduced for control. The best spatial resolution achieved for those experiments was 150 µm.

We present numerical time-domain modeling and valida- tion framework for impulse-driven near-fleld thermoacoustics imaging. It has been recently demonstrated that this new imaging approach comprises a viable alternative for high performance and low-cost imag- ing using the thermoacoustic phenomenon. Placement of the imaged object in a close vicinity (near fleld) of an antenna elements along with generation of ultrashort (nanosecond) duration high-voltage ex- citation impulses further provide high imaging resolution and ensure that su-cient level of electromagnetic energy reaches the object under investigation. In order to analyze the measured results and also provide a design and optimization framework, this work presents a full-wave computational electromagnetic framework which couples the near-fleld electromagnetic fleld to the acoustic signal generation. The numeri- cal method comprises a flnite integral time domain method (FITD) based on the industry standard CST 2010 software package. The re- sults can be further utilized for normalization and quantiflcation of the generated images.

Existing imaging modalities like microwave- or radiofrequency (RF) induced thermoacoustic tomography systems show the potential for resolving structures deep inside tissue due to the high penetration properties of RF. However, one of the major drawbacks of existing thermoacoustic tomography systems with pulse modulated carrier frequency excitation is the compromise between efficient signal generation and attainable spatial resolution. In order to overcome limitations of conventional thermoacoustic imaging methods, we herein present and experimentally validate our novel approach towards high resolution thermoacoustic tomography. Instead of carrier-frequency amplification, we utilize ultrahigh-energy electromagnetic impulses at nanosecond duration with near-field energy coupling, thus maintaining thermoacoustic signal strength without compromising spatial resolution. Preliminary experiments on highly absorbing objects, consisting of copper wires with characteristic sizes of ~100 μm, reveal the resolution performance which yields 160 μm. Furthermore, benefits like its cost effectiveness, simplicity and compactness with the potential application in small animal imaging as well as human body imaging show that thermoacoustic tomography with impulse excitation is a promising imaging modality which has a broad range of applications.

Electromagnetically Coupled Patch Antenna (EMCP) appeared to be first discussed by Sabban [1]-[2] and since then it has been under careful investigations [3]-[9] because of its broadband operation together with simple structure. For example, Lee et al[3]-[5] experimented the effects of the parasitic patch sizes, dielectric superstartes and the distance between the patches on the behavior of the antenna very carefully. The conventional structure for EMCP is shown in Fig 1. In this paper a new designed structure for L-band operation is investigated using the finite-difference time-domain (FDTD) technique. A fairly accurate model for coaxial probe fed is applied and the simulated input impedance and radiation patterns are compared with the measured results.