| 摘要 |
PROBLEM TO BE SOLVED: To provide an AFT circuit which does not depend upon the primary factors of dispersion of offset, temperature properties, etc. SOLUTION: A multiplication circuit 12 multiplies a first output signal (fVCO) generated by a conventional automatic phase control(APC) loop circuit by a second output signal (fIF+fref) generated by a phase locked loop(PLL) circuit constituted on a specified reference signal (fref). A phase difference detecting circuit 14 and an edge detecting circuit 15a or 15b receives the input of the result of its multiplication, performs edge detection (for example, the signal of pulse density equivalent to the frequency difference between image middle frequency fIF and the above first output signal fVCO), and generates AFT voltage based on the result of this edge detection.
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