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Grey Code used in radar (weight bit)


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Hi Joseph

"Gray codes are named after the Frank Gray  who  patented  their
    use for shaft encoders in 1953"

    "A Gray code represents  each  number  in  the  sequence  of  integers
    {0...2^N-1} as a binary string of length N  in  an  order  such  that
    adjacent integers have Gray code representations that differ in  only
    one bit position.  Marching through the  integer  sequence  therefore
    requires flipping just one bit at a time.  Some  call  this  defining
    property of Gray codes the "adjacency property".

The above I've taken from http://cafaq.com/extra/gray.html one of the many web sites which refer to Gray codes.

The most important thing about Gray codes is the fact that each angular(or linear or whatever) transition causes a change in only one bit of output.  To put this in context, imagine an angle encoder system which had 10 fingers making contact with concentric copper pads and was a binary representation of angle and further that it had been calibrated in the laboratory to be perfect at 20 degrees Centigrade.  So, rotating from say an angle of 15 deg (1111) to 16 deg (10000) means 5 fingers (in this example) must transition perfectly at the same time and that there must be an infinitely small gap between tracks.  Imagine what happens at other temperatures? What happens when the gap in a track is not infinitely small?

There are a number of angular encoding systems used in radar, not all based on Gray code - could you give some more detail?


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