Radio Science

Wider Aperture Sine-Cosine Direction Finders


  • Douglas N. Travers,

  • Terry C. Green


Higher-order sine-cosine azimuth patterns for Adcock direction finding are investigated to determine spacing errors, reradiation errors, and pickup factor. The higher modes achieve wider apertures and reduced wave interference error; they exhibit comparable pickup factors but require an increase in the minimum number of antennas and different sensing methods. The 1.220λ spacing limit is appropriate only to the dipole mode, the corresponding limit for the quadrupole mode being 1.684λ and correspondingly greater for the higher modes. Reduced spacing error for the minimum number of antennas occurs at increasingly wider apertures which also tend to more closely approach the theoretical limits with increasing mode. The higher modes exhibit reduced response in the vicinity of the zenith. The resolution of the additional bearing ambiguities involves the use of one or more lower-order patterns. Predicted sense performance as a function of reradiated field amplitude is computed for a combination of quadrupole and dipole modes.