TABLE OF CONTENTS The types of antenna commonly used for RF radiated susceptibility testing are treated separately from antennas used in emission measurements as the antenna parameters relating to reception and transmission are different.
Antennas for EMC radiated susceptibility or immunity testing fall into two classes: free wavefield and bounded wavefield, addressed separately in this chapter. Generally, free-field antennas are used for tests on large systems or subsystems, and on units at frequencies above 30 MHz. Bounded-wave devices such as parallel plate lines are generally used for testing small units about 30cm high at frequencies below 300 MHz. There are of course exceptions to these generalities and bounded-wave devices for example can be used to test large vehicle systems at kV/m field strengths in NEMP (nuclear electromagnetic pulse) measurements. Small units or components can be tested in bounded-wave devices (with extended frequency coverage up to 1 GHz) such as Crawford cells or GTEM (gigahertz transverse electromagnetic mode) cells.
Free-field antennas are not as efficient at producing high field strengths (over a large volume) as bounded-wave devices are over a small volume. In many cases of conformance testing, the use of free-field antennas or bounded-wave devices is specified over a given frequency range by the EMC standard which applies to the EUT. For those development tests where the EMC engineer has some discretion in choosing antennas, the more efficient bounded-wave devices will probably be chosen if the size of the EUT and test frequency...
