| 摘要 |
PURPOSE:To accurately measure a frequency converting circuit regardless of the valiance of the electric characteristics of a device to be measured by connecting the output terminal of a converting circuit to one input terminal of a computing element and impressing a reference voltage to the other reference input terminal. CONSTITUTION:Even if the variance of the input impedance of the LC tuning circuit terminal of a circuit 2 to be measured is generated each device the operation/wherein a specific reference local oscillation frequency is set previously to an input terminal of the computing element 44 with a DC voltage, etc., to detect the difference between the local oscillation frequency of each device and the reference value of the computing element and instruct it to a control voltage instructing circuit 47 and the instruction contents are sent to a control voltage generating circuit 43 and fed back to an LC turning circuit 3 is repeated until the specific local oscillation frequency is obtained. Consequently, the input impedance variance among devices at the specific local oscillation frequency is absorbed to obtain a stable, high-accuracy tuning frequency, i.e. local oscillation frequency, thereby easily measuring frequency conversion characteristics.
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