Image Number 10 for United States Patent #4200871.
A continuous-wave frequency-modulation active radiometric target seeking device performs search, acquisition, and tracking functions. A technique is provided for target range discrimination and recognition using a pair of narrow band i.f. filters also improving both signal-to-clutter ratio and signal-to-receiver noise ratio. Target search is accomplished with simultaneous and synchronized range and antenna azimuth scanning with range bins effectively swept across the target by variably modulating the transmitted carrier frequency. Recognition of a substantially point target is achieved by a bipolar pulse discriminator responsive to the i.f. filter pair. Upon target acquisition, tracking is maintained by imposing a high frequency dither upon the modulation frequency in a closed loop control using only a single i.f. filter.