| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem such that the logarithm function ROM of J and K, a subtraction circuit obtaining the difference of the respective logarithms, an inverse logarithm function ROM and an inverse tangent function ROM are required for obtaining a phase componentθfrom orthogonal demodulation outputs J and K in a digital radio machine and that it is difficult to constitute the ROM by ROM loaded on one DSP since memory capacity comes short. SOLUTION: The outputs J and K of the phase range reduction part 31 of a demodulation part 3 are inputted to the inverse tangent function ROM 32. The inverse tangent function ROM 32 is the inverse tangent operation table of J/K, where J and K are set to be the addresses of an operation. The value of Tan-1J/K is directly outputted from the output.
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