| 摘要 |
PROBLEM TO BE SOLVED: To perform level correction, while sharply reducing the number of correction data to be stored in a memory. SOLUTION: A memory 21 stores plural pieces of correction data, corresponding to setting frequencies less than the number of plural input frequencies for each setting frequency stepΔf having step width wider than that of an input frequency step. When a selected input frequency Fx is not equal to any one of plural setting frequencies, a CPU 22 reads out at least two pieces of correction data which correspond to at least two setting frequencies close to the selected input frequency Fx for among the memory 21, performs prescribed operation such as interpolation to at least two pieces of read-out correction data and supplies the correction data found by that operation to a D/A converter 23 as the selected correction data. The D/A converter 23 converts the selected correction data into an attenuation amount (correction amount) and applies it to a variable attenuator 10.
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