Hans Bergsma

Shielding effectiveness measurements using a reverberation chamber

Shielding effectiveness measurements have been performed using a reverberation chamber. The reverberation chamber methodology as well as the measurement setup is described and some results are given. Samples include glass reinforced plastic panels, aluminum panels with many holes, wire mesh, among others. The reverberation chamber setup gives very repeatable measurement results

Performance optimization aspects of common mode chokes

Optimization aspects of common mode chokes are presented. These are based on a behavioural model for common mode chokes and its sensitivity study. Results are used to show the influence of the designable parameters on the final performance of the choke placed in a circuit.

Comparison of evaluated and measured performances of common mode chokes

Comparisons of evaluated and actual performances of common mode chokes are presented. The evaluated performances are based on a new behavioural model for common mode chokes and the identification of its uncertainties to evaluate the upper and lower limits of the final attenuation. Results are compared with the final performances of the choke placed in a circuit. The behavioral model is essential in simulation of EMI effects.

Estimation of the probability distributions for cable coupling using unscented transforms

This work presents the use of unscented transforms (UT) for the description of statistical uncertainty in electromagnetic coupling between cables. UT greatly reduce the computational burden for the statistical analysis of nonlinear problems compared with more traditional approaches such as the Monte Carlo technique. Coupling between cables has a nonlinear parameter dependence and has a high variability due to the variability in the cable braid manufacture and the highly variable nature of cable layout. Therefore, cable coupling can only be defined within statistical limits. First, it is shown that by analyzing the resonances the important features of maximum coupling and the point of maximum coupling can be characterized. It is then demonstrated how UT can be used to efficiently identify the parameters which contribute significantly to the uncertainty in cable coupling and then to provide a measure of the probability distribution for the multivariate problem.

Protection Against Common Mode Currents on Cables Exposed to HIRF or NEMP

Above deck, cables on naval ships are exposed to high-intensity radiated fields and nuclear electromagnetic pulse (NEMP) that may cause conducted interference and generate electromagnetic fields that exceed the immunity levels of commercially available equipment above and below deck. Exposed cables, such as open power plugs or lighting cables, are modeled and characterized both as a monopole antenna perpendicular to the deck and as a transmission line, representing a cable close to the deck. The placement of an illuminated cable close to the deck is a good protection measure for long cables at low frequencies, which includes NEMP protection. The coupled pulse from a high-intensity NEMP illumination is not expected to cause damage on electric installations. It is shown that for exposed cable length of maximum 25 cm and not placed in the line of sight of transmitters above 400 MHz, no additional protection measures are needed.

Risk based EMC for complex systems

The rule-based approach, i.e. following electromagnetic interference standards, is the basic methodology assumed to result in electromagnetic compatible systems operating properly in their intended environment. For complex systems we need a smarter approach, based on assessing and controlling the electromagnetic risks. This risk-based approach is described, and applied to naval ships.

Using an in-line uninterruptable power supply as TEMPEST ‘filter’ for naval vessels

A major objective of TEMPEST engineering is to separate equipment carrying classified (=RED) data from equipment carrying unclassified (=BLACK) data, to prevent unintentional radio or electrical signals, containing classified data, emission. RED/BLACK separation in the power supply system is in general achieved by adding TEMPEST filters, but on board naval vessels the power system is insulated and the use of filter capacitances is limited. Solid-state uninterruptable power supplies (UPS) create isolation, because of the AC/DC and DC/AC conversion and associated internal filtering. Measurements have been performed on an operational UPS to determine the a-symmetrical, symmetrical and non-symmetrical isolation. The results obtained from the UPS tested show very good isolation which, combined with the already installed power line filters inside equipment, will be more than adequate to achieve the required isolation for RED/BLACK separation.