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In wideband interferometer direction finding, the inherent non-linearity owing to radome, antenna, and signal polarization can cause non-uniform phase propagation along the incident of the signal, leading to distortion of phase difference between receivers. This affects the accuracy of direction finding, particularly in two-dimensional direction finding where azimuth and elevation are mutually influential. In this study, we proposed a two-dimensional direction finding method to divide the detection range into several areas based on azimuth and elevation axes, select the area through a two-dimensional rough direction finding operation, and perform direction finding by correlation operation in the selected area. In addition, combination azimuth and combination elevation phase differences that are robust against phase delay distortion were used in two-dimensional rough direction operations. This method overcame nonlinear phase transfer characteristics and minimized the increase in error as the incidence angle increased. Performance tests confirmed that the proposed algorithm achieved high accuracy two-dimensional direction finding in a wideband (H/I/J band) system with a measurement error of 1 degree or less in the detection range, even in the presence of nonlinear characteristics of radome/antenna.

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Geo-pointing is a function that maintains LOS(Line of Sight) to a stationary ground target by controlling azimuth and elevation angles of a EOS(Electro-Optical System) which are calculated from aircraft navigation data and target coordinates. In design and implementation of the geo-pointing, a transmission time delay between GPS/INS and EOS is a major degradation factor of the geo-pointing performance when the aircraft is rapidly maneuvered especially. In this paper, a kalman filter is designed to compensate the transmission time delay of aircraft navigation data. Simulation and test results show that the geo-pointing performance is enhanced by the proposed compensation technique.