| 摘要 |
The invention provides a conversion arrangement, particularly applicable to radar, for converting digital information representative of the rotational (azimuthal) position of the radar antenna to sine and cosine of azimuth waveforms for use in a display such as a plan position indicator. A frequency oscillator standard is coupled to an n-stage reference counter the square wave output of which is subsequently filtered to provide a reference cosine wave of predetermined frequency. Azimuth change pulses representative of the antenna positional rotation are mixed with the frequency oscillator standard and coupled to a second n-stage or n-bit counter operating in like manner to the reference counter. The content of the second counter is advanced with respect to the reference counter by one count per azimuth change pulse, the second counter in turn serving to generate cosine and sine sampling pulses. These pulses sample the reference cosine wave to provide an output signal which when filtered derives cosine phi and sine phi positional information signals respectively. System reference is obtained by presetting the second n-stage counter to equal the reference counter in dependence upon each received azimuth reference pulse.
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