Angular tracker for conical scanning radar - discriminates target on main beam or side lobes and locates quadrant to compute error signal

摘要

In the radar angular tracker, the error signal is computed in azimuth and elevation, utilising the received signal, modulated according to the target position in the cone, and the scanning reference signals. With target in main beam the modulation is at the scanning frequency, while in the side lobes it is at double that. The ratio of signal levels at the two frequencies, when above a predetermined threshold, gives the condition of side lobe tracking. In this case, a measure of the asymmetry of modulation locates the target in one of four quadrants around the cone axis. A system triggered by the scanning reference signals discriminates the received signals into four channels, corresponding to the four quadrants, and comprises the error signal in azimuth and elevation. This information is utilised to steer the antenna towards a minimum error signal.