A Sum-and-Difference Interferometer System for HF Radio Direction Finding

Radio interferometers have been used for highaccuracy, high-precision source location of radio stars and radio satellites. These systems are generally optimized for a fixed frequency and have efficient means for resolving any and all ambiguities which are inherent in the particular interferometer system. Application of the radio-interferometer principle to wide-band, high-frequency radio direction finding practice by its very nature poses a severe problem of ambiguity resolution, i.e., unique determination of the bearing and elevation angles of arrival of an incident ray having any frequency within the band. A wide-band, high-frequency radio direction finder incorporating sum-and-difference interferometer techniques is described. A salient and novel feature is an analog computer-type calibrator which permits unique determination of the bearing and elevation angles of arrival from data supplied by three two-element interferometers and a central crossed Adcock array. A theoretical analysis is given along with supporting experimental data.