From a Novel

A methodology for extracting high-frequency IC interconnect transmission parameters directly from S-parameter measurements has been demonstrated using on-chip test structures. The methodology consists of: (1) building on-chip interconnect structures for microwave test, (2) characterizing and subtracting measurement system parasitics, (3) extracting the transmission line impedance and propagation constant (attenuation constant and phase constant) from the calibrated data, and (4) extracting the Telegrapher's Equation transmission parameters (R, L, C, and G). Additional on-chip calibration permits subtraction of pad parasitic effects. This methodology is demonstrated over a 45-MHz to 20-GHz frequency range using an example 1-cm-long, 4- mu m-wide IC interconnect built in an advanced BiCMOS technology. Variations in interconnect impedance and capacitance indicate two signal propagation modes. Significant substrate-based loss is measured at microwave frequencies. >

S-parameter-based IC interconnect transmission line characterization

Four classes of models of the lightning return stroke are reviewed. These four classes are: (1) the gas dynamic models; (2) the electromagnetic models; (3) the distributed-circuit models; and (4) the "engineering" models. Validation of the reviewed models is discussed. For the gas dynamic models, validation is based on observations of the optical power and spectral output from natural lightning. The electromagnetic, distributed-circuit, and "engineering" models are most conveniently validated using measured electric and magnetic fields from natural and triggered lightning. Based on the entirety of the validation results and on mathematical simplicity, we rank the "engineering" models in the following descending order: MTLL, DU, MTLE, BG, and TL. When only the initial peak values of the channel-base current and remote electric or magnetic field are concerned, the TL model is preferred. Additionally discussed are several issues in lightning return-stroke modeling that either have been ignored to keep the modeling straightforward or have not been recognized, such as the treatment of the upper, in-cloud portion of the lightning channel, the boundary conditions at the ground, including the presence of a vertically extended strike object, the return-stroke speed at early times, the initial bi-directional extension of the return stroke channel, and the relation between leader and return stroke models. Various aspects of the calculation of lightning electric and magnetic fields in which return stroke models are used to specify the source are considered, including equations for fields and channel-base current, as well as a discussion of channel tortuosity and branches.

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Review and evaluation of lightning return stroke models including some aspects of their application

Integral Equation Methods for Electromagnetic and Elastic Waves is an outgrowth of several years of work. There have been no recent books on integral equation methods. There are books written on integral equations, but either they have been around for a while, or they were written by mathematicians. Much of the knowledge in integral equation methods still resides in journal papers. With this book, important relevant knowledge for integral equations are consolidated in one place and researchers need only read the pertinent chapters in this book to gain important knowledge needed for integral equation research. Also, learning the fundamentals of linear elastic wave theory does not require a quantum leap for electromagnetic practitioners. Integral equation methods have been around for several decades, and their introduction to electromagnetics has been due to the seminal works of Richmond and Harrington in the 1960s. There was a surge in the interest in this topic in the 1980s (notably the work of Wilton and his coworkers) due to increased computing power. The interest in this area was on the wane when it was demonstrated that differential equation methods, with their sparse matrices, can solve many problems more efficiently than integral equation methods. Recently, due to the advent of fast algorithms, there has been a revival in integral equation methods in electromagnetics. Much of our work in recent years has been in fast algorithms for integral equations, which prompted our interest in integral equation methods. While previously, only tens of thousands of unknowns could be solved by integral equation methods, now, tens of millions of unknowns can be solved with fast algorithms. This has prompted new enthusiasm in integral equation methods.

Integral Equation Methods for Electromagnetic and Elastic Waves

In this paper, a new technique for preconditioning electric field integral equations (EFIEs) by leveraging Calderon identities is presented. In contrast to all previous Calderon preconditioners, the proposed preconditioner is purely multiplicative in nature, applicable to open and closed structures, straightforward to implement, and easily interfaced with existing method of moments (MoM) code. Numerical results demonstrate that the MoM EFIE system obtained using the proposed preconditioning converges rapidly, independently of the discretization density.

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A Multiplicative Calderon Preconditioner for the Electric Field Integral Equation

This paper illustrates the application into the MoM technique of a clever formulation to evaluate the array green's function (AGF) of large finite planar phased array. The procedure is based on the AG F representation in terms of a double spectral integral, whose integration paths are properly deformed to have an exponential attenuation of the integrand. The diffraction integral is evaluated numerically for point close to the array edges while an asymptotic treatment is proposed far from the edges. This latter comprises higher order contributions. Thanks to this convergence properties, the final algorithm is numerically accurate, stable and more efficient with respect to the individual element summation for large arrays. This AGF is then inserted into the MoM scheme, where the reactions are calculated between two basic cells ("cell on cell"). Each cell includes the radiating element, which is still meshed by using RWG basis function. This procedure allows a reduction of complexity either infilling the MoM matrix or in solving the system.

Use of advanced truncated-array Green’s function in MoM analysis of large finite arrays

Sistema per la disinfezione di terreno agricolo

Beam-scanning antennas are employed in a wide range of applications, such as in satellite communications and 5G networks. Current commercial solutions rely mostly on electronically reconfigurable phased arrays, which require complex feeding networks and are affected by high losses, high costs, and are often power-hungry. In this paper, a novel beam scanning architecture employing a pair of planar metasurfaces, for use in thin reconfigurable antennas, is presented and experimentally demonstrated. The structure consisted of a radiative passive (non-reconfigurable) modulated metasurface, and a second metasurface that controls beam pointing, operating as a variable-impedance ground plane. Unlike other existing approaches, surface impedance variation was obtained by on-plane varactor diodes, no vias and a single voltage bias. This paper presents a design procedure based on an approximate theoretical model and simulation verification; a prototype of the designed antenna was fabricated for operation in X band, and a good agreement between measured results and simulations was observed. In the presented simple embodiment of the concept, the angular scanning range was limited to 10°; this limitation is discussed in view of future applications.

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Experimental Demonstration of Beam Scanning of Dual-Metasurface Antenna

The paper proposes an innovative deployable measurement system for large antennas. By taking advantage of new approaches and technologies to move the probe within a large volume space, the presented system will be really flexible and able to perform conventional Near Field (NF) measurements (i.e., spherical, planar, cylindrical) and non standard scanning surfaces. The proposed approach will exploit a free moving probe system coupled to a laser-tracker and a software solution able to perform Near Field to Far Field transformation that includes also the probe-compensation and phase recovery in a direct way. Preliminary results are provided to show the potentials of the system, through a Near Field data set acquisition, which is then transformed to the Far Field to compare the final antenna performance.

Flexible and Deployable Antenna Measurement System

Automated antenna optimization remains a promising technique in computer aided design and a number of works in this area have been published in the past years. Song and Murch, “An efficient approach for optimizing frequency reconfigurable pixel antennas using genetic algorithms,” IEEE Trans. Antennas Propag., vol. 62, no. 2, pp. 609–620, is a new contribution to this field which unfortunately understates previous works in its introduction. We discuss how their paper relates to these earlier works.

Giuseppe Vecchi

Papers

Use of advanced truncated-array Green’s function in MoM analysis of large finite arrays

Sistema per la disinfezione di terreno agricolo

Experimental Demonstration of Beam Scanning of Dual-Metasurface Antenna

Flexible and Deployable Antenna Measurement System

Comments on “An Efficient Approach for Optimizing Frequency Reconfigurable Pixel Antennas Using Genetic Algorithms”