Abstract: An array of antenna elements is arranged along a common, rotating platform so as to form a pair of mechanically scanned interferometers exhibiting spaced, parallel receiving axes for ranging on a distance emitter. As the receiving lobes of the pair of interferometers scan across the emitter, lobe modulated signals are received having a relative time difference t.sub.21 that varies as a sinusoidal function of time due to the platform's rotation and includes a dc error value due to slight but unavoidable nonparallelism of the interferometer beams. The rate of change of t.sub.21 is derived to produce a signal t.sub.21 which drops the dc error component of t.sub.21, and which is applied as an input to a rate dependent range signal processor producing an output signal of range R as a function of the relationship ##EQU1## In this relationship d is the separation of the interferometer centers along the base line, and .phi.

Abstract: In an optical ranging apparatus, especially designed for measuring the range to a source of infrared radiation, a narrow band time-shift servoloop processor is used to resolve the offset (separation distance) of images of the infrared source that are projected onto first and second, juxtaposed photooptical detector arrays. The range (distance) to the infrared source is functionally related to the measured offset of the infrared images. To enable the servoloop processor to measure this offset, the outputs of the first and second detector arrays are automatically scanned by electronic scanning circuitry to develop first and second time-variable signals that represent the relative positions of the infrared images on the respective arrays. These time-variable signals are substantially overlapping, and the slight phase or time separation between these signals is related to the offset of the images on the detector arrays.

Abstract: A servo loop processor suitable for use in a passive radar range determining system is disclosed. Early and late overlapping video pulse trains derived from spaced receiving antennas are fed to separate first and second channels and are sampled and held from pulse period to pulse period to form signals representing the amplitude envelopes of the received pulse trains. The output of the first channel is variably delayed and the delayed signal is compared with the undelayed output of the second channel to create an error signal. The output of the second channel is also differentiated, and the result is sampled and held to create a reference signal that has the proper phase relationship with the error signal so that the error signal can be multiplied by the reference signal to create a correction signal. The resulting correction signal is integrated and fed back to control the time delay applied to the output of the first channel such that a closed servo loop is formed.