TABLE OF CONTENTS A probe designated for wideband EMF measurements in the near-field, should fulfill the following requirements:
The size of the probe's antenna should be considerably smaller in comparison to the minimal wavelength of the frequency range being measured, and they should not exceed (at first approximation) the minimal distance probe-source, at which the measurement is to be performed
The transmittance of the probe should be as high and flat as possible within the measuring frequency band while the magnitude of the transmittance outside of the band should not exceed that within the band
and sometimes:
The lower corner frequency should be as low as possible.
The first two first requirements contradict one another which creates the necessity of finding a compromise solution. For instance, an increase in antenna size results in a sensitivity increase; however, the size increases result in an increase of errors caused by the mutual interaction of the antenna and the field source. As a result, there is a decrease in the permissible upper corner frequency of the antenna-equipped probe and the distance probe-source where the measurement may be performed. If its desired accuracy has to be unchanged, the upper corner frequency must be enlarged.
Both the necessity of comparing probes of different parameters and then optimizing them requires the introduction of a common measure which takes into account the above mentioned three postulates. We call this measure the quality factor (q) of the probe and we define it in the form:
As...
