| 摘要 |
<p>A five stage background filter circuit (10) which is capable of responding to background radiation changes at speeds which are from one to two orders of magnitude faster than conventional prior filter. The invention utilizes a cross can multiplexing technique in combination with filter circuitry depicted in schematic over view in (Fig. 1). Circuit (10) includes a differential amplifier (12), a sample and hold device (14), a responsivity corrector (16), a recursive filter (18), and a background subtractor (20). Output signals (11) from a focal plane array of detectors (Fig. 3) are passed through impedance matching input resistors (12a, b) to an amplifier. A sample and hold circuit (14a) cyclically selects and stores a signal received from first stage (12). The detector outputs are then normalized by responsivity corrector stage (16) which employs a digital-to-analog converter (16a) and random access memory (16c). A threshold band comparison and time-out logic circuit (21) within background subtractor stage (20) controls the operation of recursive filter stage (18) in order to suppress signals due to sensed radiation bursts and to eliminate the unwanted, dynamically varying background radiation portion of the signal present at node (17b). A processed output signal present at node (20i) is then passed to a target detection processor.</p> |
