Image discriminator which automatically enhances the ability of a system

Abstract

An image discriminator which automatically enhances the ability of a system to discriminate between sources that can not be removed by fixed spectral cancellation. The invention (10) includes a mechanism (12, 14, 16, and 18) for separating input energy into first and second frequency bands and providing first and second signals corresponding thereto. The ratio of the amplitudes of the first and second signals are varied by variable gain amplifiers (20 and 22) and subtracted from each other by a subtractor 24 to provide a control signal. The control signal is used in a tracker circuit 24 to control the gain of the first and second signals. Third and fourth signals are extracted by dual on-track signal rejection (28 and 30) from the first and second signals which represent energy from non-tracked objects. Circuitry (34 and 36) is provided for varying the ratio of the amplitudes of the third signal and the fourth signal in at least two trials. The amplitude ratio varied third signal is subtracted from the amplitude ratio varied fourth signal for each respective trial by subtractors (38 and 40) to provide fifth and sixth signals respectively. The fifth and sixth signals are analyzed and used by level detection circuitry (42, 44, 46, 48, and 50) to adjust the ratio of the gain of the first and second signals in response thereto thereby enabling cancellation of unwanted signals in the subtractor 24.