Importance

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Abstract

A tuning circuit has a simple circuit construction and is capable of setting Q thereof to a high desired value. The tuning circuit is formed by a resonance circuit consisting of an inductor and a capacitor and a negative resistance circuit connected in series to the resonance circuit including a negative impedance converter and a variable resistor. A counter counts clock signals from a clock signal generating circuit and a count value is converted to an analog signal by a D/A converter. The negative resistance circuit is controlled by the analog signal so that an effective resistance of the tuning circuit is made negative to oscillate and to vary a negative resistance value in a positive direction. When the effective resistance value becomes zero, oscillation stops and thereafter when a value of Q becomes a predetermined value, the clock signals are stopped and the latch circuit holds a final count value.

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First Claim