| 摘要 |
<p>A tuning mechanism is provided with a tuning circuit (1) constituted by cascade-connecting two phase shifting circuits to each other and a frequency control circuit (2) incorporating a phase difference detecting circuit (3) and a control voltage generating circuit (4). The circuit (3) converts the input and output signals of either of the two phase shifting circuits into rectangular-wave signals, calculates the exclusive OR of the rectangular-wave signals, and outputs the exclusive OR to the circuit (4). The circuit (4) smoothes and amplifies the output of the circuit (3) and adds a prescribed bias voltage to the amplified output to generate a control voltage for determining the tuning frequency of the tuning circuit (1). The control voltage is inputted to the two phase shifting circuits. The circuit (1), keeping the time constants of the phase shifting circuits equal to each other, adjusts the phase shift base on the control signal and equalizes the tuning frequency to the frequency of the input signal of the tuning circuit (1).</p> |
