Abstract: A current limiting circuit is disclosed which comprises means for monitoring an electrical current to be controlled, means for generating a signal having a periodically variable value, and means for adjusting the periodic signal in accordance with the value of the current to be controlled. A comparator produces a signal having a first value when the value of the periodic signal is below the value of a threshold, to change the duty cycle of its output in the direction which causes comparator-responsive means to decrease the monitored current.

Abstract: A Class-D audio amplifier is disclosed which accepts a digitized audio signal input and drives a load such as a loudspeaker without digital-to-analog conversion. The amplifier preferably comprises (1) means for processing a plurality of digital audio input values to create a plurality of deviation values respectively based on the deviation of the input value's relationship from a previous audio input value, (2) means for producing a carrier signal, (3) modulation means for using the deviation values to responsively modulate the carrier signal by varying the frequency of its waveform inversely with the magnitudes of the deviation values, and (4) filter means operative on the modulated carrier to produce an analog voltage capable of driving the load.

Abstract: A method and apparatus for correlating two signals representing a live image and a reference image are disclosed. The reference signal is processed to provide a polarity bit and mask bit for each pixel position in the reference image. The processed video signal is stored in a memory 20 and used in a convolver and summer section 18 in which the polarity bits between the reference and live images are gated by gate 17 and are used in generating a correlation output from summer 23. However, the polarity bits do not affect the correlation output if the logical output from gate 19 is of a given state which occurs if the associated mask bits indicate that the gradient value at the particular pixel position does not exceed certain minimum threshold values.

Abstract: A conventional tracker 14 is used to continually aim a sensor 12 at a flying object so that it is located in substantially the same spatial location in a plurality of image frames taken at different times. Thus, the object remains in about the same spatial position in each image frame while the background clutter generally changes. By processing two or more of the image frames it is possible to calculate a more precise aimpoint for the object than is generally provided by the track point.