Importance

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Abstract

The apparatus generates a train of pulse signals in real time which are fed to a Plan Position Indicator radar display video bright-up circuit. A line is formed on the display at a bearing .theta..sub.R , the direction of a VHF/DF fix, and passes through a point having the coordinates R.sub.o, .angle..theta..sub.o .degree., the position of the VHF/DF receiver, with respect to the center of the plan position indicator rotating radial scan. The radial scan operates at a radar trigger pulse repetition frequency F and rotates at a frequency f to subtend an angle .DELTA..theta.=360.degree..times.f/F per scan. The apparatus includes an up-counter for storing a count of R.sub.o sin (.theta..sub.R -.theta..sub.o), and a down-counter coupled to the up-counter and enabled at the pulse repetition frequency F to receive the count from the up-counter. The down-counter is adapted to provide an output pulse signal to the video bright-up circuit when its count reaches 0. A binary rate arithmetic multiplier has a first input which receives clock pulses at a frequency f.sub. c >>F and a second input which receives a digital binary signal that is a function of the radar pointing angle .theta. of the radial scan. The multiplier thereby provides a series of timed output pulses to the down-counter such that the down-counter counts down to 0 and triggers the video bright up circuit.

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First Claim