Active Filters with Voltage-Variable Passband for Application to Range-Gated MTI Systems.
Larry George Mitchell · Defense Technical Information Center (DTIC) · 1968
Range-gated moving target indicator (MTI) systems have some intrinsic advantages over delay-line canceler MTI systems. A further improvement in performance would result if the doppler cut-off frequency was adjustable by the radar operator. Because of the large number of filters involved in one system this would require a voltage-variable filter element. A theory of variable filter response developed by Thiele was used as the basis for design using integrated-circuit operational amplifiers as the active elements. Three different types of active filter circuits are discussed. Implementation of voltage-variable filters and experimental frequency-response curves using field-effect transistors, Raysistors, and discrete switched resistors are described and illustrated. (Author)