Bistatic system passively tracks radar targets

The Bistatic Object Location System (BOLS) is presented as an example of bistatic receiving systems which can locate radar emitters without radiating signals themselves. The BOLS concept is designed to passively detect circularly scanning radars and the objects illuminated by those radars. Simple timing equations are employed to compute parameters such as time, angle, and range from detected reflections from the main beam and the sidelobe. Three tests are reported in which the BOLS detects and locates objects by using alternately a horn antenna with standard equipment, a manually steered narrow-beam-width antenna, and a three-channel interferometer direction-finding subsystem. The investigations show that the BOLS' capability for passive location of nonemitting objects is highly accurate and enhances the capabilities of the host platform.