TABLE OF CONTENTS Direction finding is a method to determine the direction of a transmitted signal by using two antennas and by measuring the phase difference between the antennas, as shown in Figure 10-1. This process is called interferometry. In addition to using a static interferometer, further analysis is needed to calculate the direction when the interferometer baseline is dynamic. That is, the interferometer is moving and rotating in a three dimensional plane. To provide accurate measurement of the direction in a three-dimensional, coordinate conversion processes need to be applied to the non-stabilized antenna baseline plane.
For a non-stabilized antenna baseline, the elevation, roll, and pitch of the antenna baseline need to be included as part of the interferometer process for accurate azimuth determination using interferometer techniques. Therefore, the azimuth angle calculation involves a three-dimensional solution using coordinate conversions and direction cosines. The coordinates are moved due to the movement of the structure. Therefore, the direction phasor is calculated on the moved coordinates and a coordinate conversion then positions the phasor on the absolute coordinates.
Direction cosines provide a means of defining the direction for a given phasor in a three dimensional plane. They are crucial for defining and calculating the interferometer equations.
A phasor A is represented as
The i, j, k are unit vectors. For example, i = (1, 0, 0), j = (0, 1, 0), and k = (0, 0, 1)...
