Post-Detection in the Navy Space Surveillance System

The Naval Space Surveillance System is a multistatic cw radar system using the principle of the radio interferometer. Satellites are located in space by measuring the direction cosines of the reflected radio energy and triangulating from two or more receiving sites. Since the direction cosines are determined by electronically measuring the electrical phase difference between pairs of antennas, it is important to maintain phase coherency between all phase carrying channels as well as minimizing all differential phase shifts throughout the post-detection circuits. Characteristics of post-detection filters and phase measuring circuits are discussed in the light of the undesirable incidental phase changes in the system and those caused by phase-rate (the latter being a function of the satellite's relative speed with respect to the surveillance fence). Sensitivity and system error is examined as the phase signals are traced through wide and narrow band post-detection filters. Some work on the affect of "phase jump" on the system is also considered as simple circuits are stimulated by a sudden change in phase.