| 摘要 |
PURPOSE:To suppress the deviation of an actual reception frequency with respect to the desired reception frequency by adding a correction voltage to a control voltage applied to a dual tuning circuit of a reception circuit, and setting the level of the correction voltage to a level optimizing the level of an intermediate frequency signal. CONSTITUTION:At first a maximum point of an intermediate frequency signal level, that is, a reception signal fd (point A) is obtained and frequencies (points B, C) having a level lower than the point A by a prescribed level (e.g., 3dB) are obtained, and a midpoint D (D=(B+C)/2) between the points B and C is calculated and the point D is used as an optimum correction data. Moreover, the frequency (f) of the X axis is expressed in f=1/2pi(LC<1/2>), and since the capacitance C is subject to change by the control voltage V, the frequency varies with the control voltage V. The tuning frequency of the reception circuit is controlled optimizingly by supplying the correction voltage obtained in such a way.
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