Omnidirectional detectors of microwaves

Two isotropic antenna systems for detection of electromagnetic waves have been developed, and graphs of sensitivity versus angle of rotation of antennas about three mutually perpendicular axes have been recorded. The two types of antenna systems had approximately constant sensitivity for incident waves with arbitrary linear polarization. These antenna systems consist of 12 crystal-diode detectors on the surface of a sphere and six crystal-diode detectors on six edges of a tetrahedron. The spherical antenna system is the more omnidirectional of the two when the antenna system is approximately one-third wavelength in diameter or resonant. When the dimensions were reduced to less than one-tenth wavelength, the pyramidal antenna system was most omnidirectional. The immediate concern was to design detectors for the safety of workers near high-power microwave sources and probes for detection of excessive leakage from microwave ovens in the home.