Discrete frequency-versus-radius reticle trackers

This paper presents a general expression for the transmission function of the discrete frequency-versus-radius reticle and compares such a reticle to the more common continuous reticle. A discrete form of the frequency-versus-radius reticle has an integer number of chopping cycles on a single radius. The discrete form limits the resolution of the reticle in the radial direction, but this limit is not severe for small target images. However, since no phase reversal occurs, electronic processing is simplified. Also, a tracker is presented that utilizes two discrete frequency-versus-radius reticles that can track large objects and eliminates target cancellation.