Andrew S. Podgorski

Three Dimensional Time Domain Modelling of Lightning

The Thin-Wire Time Domain (TWTD) Code and the Waterloo Analysis and Design (WATAND) Code were combined into a new three-dimensional (3-D) time domain computer code. Based on the new computer code a 3-D time domain model of lightning was proposed. The lightning model was verified during the 1985 lightning season by measurements conducted at the CN Tower in Toronto. Using the new model, it is possible for the first time to correct the lightning current for the presence of towers and to predict the current distribution along a lightning channel.

Study of picosecond rise time in human-generated ESD

Measurements of human-generated electrostatic discharge (ESD) were conducted during the Canadian winter under low humidity conditions. These measurements indicate the existence of ESD impulses with rise times shorter than 100 ps and peak current amplitude in excess of 50 A. The measuring system consisted of a current sensor with a calibrated bandwidth of 5 GHz and a TEK 7250 digitizer with numerically corrected bandwidth of 10 GHz. A bare hand, a blunt object (screwdriver), a sharp object (scriber), and a car key were used during the test.<<ETX>>

New broadband gigahertz field simulator

A new electromagnetic field simulator for the measurement of radiated susceptibility and emission is presented. The design of the new simulator permits its easy incorporation into existing EMC and EMP facilities and provides for facilities testing capability expansion into the gigahertz region.

Radiated emission measurements conducted in the AST semi-anechoic chamber dual polarization broadband gigahertz field simulator and their verification with the measurements done on the open area test site

This paper addresses an innovative method of measuring radiated emission, using a dual polarization, broadband gigahertz field (BGF) simulator. Verification of emission measurements conducted in the BGF simulator with the measurements done on an open area test site (OATS) is presented.

Evaluation of HardSys: a simple EMI expert system

The concepts used in designing HardSys, a simple expert system capable of reasoning about EMI problems, are described. These are then evaluated by running the expert system on a test case previously analyzed by an EMI consultant. The test case was a subset of the NEMP (nuclear electromagnetic pulse) hardening of a typical military helicopter. The knowledge representation used in HardSys is of a fuzzy nature and it is this fuzziness which the authors evaluate. It is concluded that the present knowledge representation is a very powerful tool for EMI engineers.<<ETX>>

Lightning standards for aircraft protection

The lightning peak current amplitudes and peak current derivatives recorded on short and tall towers and aircraft, obtained through EM field measurements in a high probability of occurrence region are successfully verified by the use of a unified lightning threat concept. The lightning peak current amplitudes and peak current derivatives are then extended to a low probability of occurrence region to determine the anticipated values of both variables. A comparison of the existing standards for protection of an aircraft with the anticipated peak current amplitudes and peak current derivatives is presented along with conclusions concerning the adequacy of existing standards.<<ETX>>

Composite electromagnetic pulse threat

A new electromagnetic pulse threat based on a composite ambient field defined by a combination of lightning, NEMP (nuclear electromagnetic pulse) and microwave threats is discussed. The composite electromagnetic pulse threat has been used to harden a military helicopter. The hardening to a composite threat resulted in the development of simplified hardening verification procedures. It also provided an economical advantage.<<ETX>>

Three Dimensional Modelling Of HV Systems

The Numerical Electromagnetics Code (NEC) is applied to frequency-domain modelling of HV systems. This application results in an improved model in comparison with the lumped-distributed approach. The new model not only takes into account the geometry of each individual piece of apparatus but also includes the effect of coupling between different components of the HV system. The model additionally incorporates the effects of parasitic elements such as the inductance of a resistive divider or ground plane losses. The limitations and capabilities of the user-oriented implementation of the NEC in the analysis of HV systems are presented by modelling a few of the following problems: the electromagnetic interference (EMI) generated by discharging an RV impulse generator, the transfer function of a resistive divider, and the electromagnetic (EM) field distribution of a resistive divider.

New concept of hybrid TEM-Cell and reverberation chamber facility

The paper describes new hybrid Transverse Electromagnetic Cell (TEM-Cell) and Reverberation Chamber (RC) facility. The TEM-Cell, using four wired septums, operates in the frequency range from 50 MHz to 1 GHz and mechanically stirred RC operates from 1 to 18 GHz. The RC uses broadband TEM-mode horn antenna installed on the outside of the chamber. Suppressing higher order modes in the TEM-Cell allows joining respective frequency ranges and results in development of a new hybrid TEM/RC test facility operating from 50 MHz to 18 GHz, with 50 MHz resulting only from availability of test equipment. For broadband testing, use of new TEM-Cell, results in more than three-fold reduction of the RC size, independently if the testing is done in the new TEM-Cell and RC separately or if it is done in a hybrid facility. The reduction of the size of the RC allows 6-fold decrease of input power required to achieve the same average E-field in the chamber.

Precursor of an Ultra-Wideband Radar System

A precursor of an ultra-wideband mono-pulse radar system is presented. The design of the radar system is based on a new TEM-Horn antenna and a picosecond HV generator developed recently by the author. The purpose of the new radar design was to verify the ultra-wideband mono-pulse radar concept and to establish the ultimate design criteria for the ultra-wideband radar system.