Design and implementation of near-field measurement probes

Abstract

The problems of electronics product because of electromagnetic incompatibility are in-creasing constantly. To end this incompatibility the European Union (EU) has decided to empower the Directive 2004/108/EC so devices could operate close to each other properly.

The product manufacturers are required to make standardized tests to verify that the product is compliant with the Directive 2004/108/EC. Many times the designer uses a lot of time to design product functions and uses project time for verification of these functions. However, the final product should be tested in according the most recent electromagnetic standards and one of these many tests is the radio disturbance test as a function of frequency and for this disturbance the standard states limit values.

This thesis is intended to bring out some phenomena by using calculations to show that how these limit values are easily broken if the product contains some design faults for example in the printed circuit board. The main focus is to design a near-field measure-ment probes which are electric field probes, magnetic field probes and a high-frequency current probe.

The standardized test is done in the far field, and sometimes for the designer it is very difficult to spot the origin of interference. According the measurement results of this thesis the designed and implemented near-field probes can be used efficiently to locate the origin of interference. The magnetic field probe and electric field probe can be used to spot interference source from the printed circuit board (PCB) and high-frequency cur-rent probe can be used to search product external cable which carries common-mode current. According the calculations of this thesis the common-mode current is most problematic radiator from electronic product cabling.