Closed-form Green's function (CFGF) representations for cylindrically stratified media, which can be used as the kernel of an electric field integral equation, are developed. The developed CFGF representations can safely be used in a method of moments solution procedure, as they are valid for almost all possible source and field points that lie on the same radial distance from the axis of the cylinder (such as the air-dielectric and dielectric-dielectric interfaces) including the axial line (= and =), which has not been available before. In the course of obtaining these expressions, the conventional spectral domain Green's function representations are rewritten in a different form so that i) we can attack the axial line problem and ii) the method can handle electrically large cylinders. Available acceleration techniques that exist in the literature are implemented to perform the summation over the cylindrical eigenmodes efficiently. Lastly, the resulting expressions are transformed to the spatial domain using the discrete complex image method with the help of the generalized pencil of function method, where a modified two-level approach is used. Numerical results are presented in the form of mutual coupling between two current modes to assess the accuracy of the final spatial domain CFGF representations. Index Terms-Closed-form Green's functions, discrete complex image method (DCIM), generalized pencil of function (GPOF) method, method of moments (MoM).

We propose and demonstrate a wireless, passive, metamaterial-based sensor that allows for remotely monitoring submicron displacements over millimeter ranges. The sensor comprises a probe made of multiple nested split ring resonators (NSRRs) in a double-comb architecture coupled to an external antenna in its near-field. In operation, the sensor detects displacement of a structure onto which the NSRR probe is attached by telemetrically tracking the shift in its local frequency peaks. Owing to the NSRR's near-field excitation response, which is highly sensitive to the displaced comb-teeth over a wide separation, the wireless sensing system exhibits a relatively high resolution (<1 μm) and a large dynamic range (over 7 mm), along with high levels of linearity (R2 > 0.99 over 5 mm) and sensitivity (>12.7 MHz/mm in the 1–3 mm range). The sensor is also shown to be working in the linear region in a scenario where it is attached to a standard structural reinforcing bar. Because of its wireless and passive nature, together with its low cost, the proposed system enabled by the metamaterial probes holds a great promise for applications in remote structural health monitoring.

Cataloged from PDF version of article.An efficient and accurate hybrid method, based on\ud the combination of the method of moments (MoM) with a special\ud Green’s function in the space domain is presented to analyze antennas\ud and array elements conformal to electrically large material\ud coated circular cylinders. The efficiency and accuracy of the\ud method depend strongly on the computation of the Green’s function,\ud which is the kernel of the integral equation that is solved via\ud MoM for the unknown equivalent currents representing only the\ud antenna elements. Three types of space-domain Green’s function\ud representations are used, each accurate and computationally efficient\ud in a given region of space. Consequently, a computationally\ud optimized analysis tool for conformal microstrip antennas is obtained.\ud Input impedance of various microstrip antennas and mutual\ud coupling between two identical antennas are calculated and\ud compared with published results to assess the accuracy of this hybrid\ud method

Cataloged from PDF version of article.An efficient method to evaluate the surface fields\ud excited on an electrically large dielectric-coated circular cylinder\ud is presented. The efficiency of the method results from the circumferentially\ud propagating representation of the Green’s function as\ud well as its efficient numerical evaluation along a steepest descent\ud path. The circumferentially propagating series representation of\ud the appropriate Green’s function is obtained from its radially\ud propagating counterpart via Watson’s transformation and then\ud the path of integration is deformed to the steepest descent path\ud on which the integrand decays most rapidly. Numerical results\ud are presented that indicate that the representations obtained here\ud are very efficient and valid even for arbitrary small separations\ud of the source and field points. This work is especially useful in the\ud moment-method analysis of conformal microstrip antennas where\ud the mutual coupling effects are important