| 摘要 |
PURPOSE:To simplify the circuit constitution, the design, and the adjustment to lower the cost, by using the quadrature frequency discriminating circuit to constitute an AM station detecting circuit for electronic tuning tuner. CONSTITUTION:The output of the limiter amplifier is inputted to one input terminal of phase comparator 4, and the output of the limiter amplifier has the phase shifted and is inputted to the other input terminal by the action of phase shifter 2 and tank circuit 3. Actual circuits such as phase shifter 2 and tank circuit 3 are the coil and the LC parallel resonance circuit, respectively; and since the frequency- phase characteristic of circuit 3 is shifted to the negative side or the positive side in accordance with the level of the frequency on the basis of the reference of 0 deg. in center frequency f0, the signal, which is shifted toward 0 deg. or 180 deg. in accordance with the level of the frequency on the basis of the reference of 90 deg. in center frequency f0, against the signal inputted to one input terminal is inputted to the other input terminal, and consequently, it has the phase detected. |
