DRAFT Recommended Practice for Measurements and ...

1/29/98 99 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
Appendixes
These appendixes are not part of IEEE Std C95.3-1991, IEEE Recommended Practice for
Measurements and Computations with Respect to Human Exposure to Radiofrequency
Electromagnetic Fields, 3 kHz to 300 GHz, but are included for information only.)
Appendix A
Additional Calibration Techniques for
External Field Measuring Instruments
A1. General.
It is sometimes advantageous to use open parallel plates or transmission lines having a
characteristic impedance other than 50 Ω, instead of a TEM cell. The major limitations of
TEM cells and parallel plate lines are the inverse proportionality between the size and
upper frequency limit. For proper operation, the spacing between the cell conductors,
i.e., the width of the septum, and the length of the uniform line (nontapered section),
should all be less than λ/2. Another limitation is that a relatively large amount of power is
required to produce desirable field intensities, for the usual case, where the characteristic
impedance Z 0 and load resistance are 50 Ω. Some alternative methods are mentioned
below.
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subject to change.