Apparatus for displaying VHF-direction finder data on a radar PPI

摘要

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 &thgr;.sub.R , the direction of a VHF/DF fix, and passes through a point having the coordinates R.sub.o, ∠&thgr;.sub.o °, 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 &Dgr;&thgr;=360°×f/F per scan. The apparatus includes an up- counter for storing a count of R.sub.o sin (. theta..sub.R -&thgr;.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 &thgr; 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.