TABLE OF CONTENTS This chapter discusses probe properties for RF magnetic field measurements and in particular, the factors limiting measurement accuracy. Our consideration is limited to a probe consisting of a circular loop antenna loaded with a detector of a shaped frequency response. The majority of the presented estimations are fully applicable for Hall-cell probes, magneto-optic probes, magneto-diode probes, and for other designs, especially when considering the averaging of the measured field upon the surface of the measuring antenna (probe).
Parts of our considerations are similar in character to those presented in Chapter 4, and parts are concerned with the magnetic field measurement specificity.
In the analogy used in Chapter 4.1, it is possible to follow the discussion relating to the measuring antenna size limitation resulting from the error of a quasi-point value of the magnetic field measurement. It concerns the electrical sizes of the antenna in particular. The discussion leads to conclusions similar to those presented in chapter 4.1 if we use ?r (where r = radius of a circular loop antenna) instead of h. However, a more rigorous limitation of the loop antenna size results from the so-called "antenna effect," in other words, from simultaneous sensitivity of the loop antenna (especially a non-screened one) to the electric field.
The current in a load of the loop antenna I l may be expressed as:
where K H and K E = sensitivity of an unloaded loop to the magnetic and electric field respectively, and...
