| 摘要 |
PURPOSE:To enable to discriminate stereo broadcast and various broadcastings even under the weak electric field, by changing the content of PLL with an output of a discriminating means discriminating the presence of an input signal. CONSTITUTION:An output of a rectifying circuit 13 enters a frequency shift circuit 18, and an output of the circuit 18 is given to a loop gain switching circuit 17 and a voltage controlled oscillator 9 respectively. Further, the output of the circuit 17 is given to either or both of a phase comparator 7 and a loop filter 8. The output of an amplifier 14 with amplitude limit enters a stereo broadcast latchup circuit 19 and various broadcast latchup circuit 20 to pick up a discrimination signal for stereo or various broadcastings from both the outputs. Thus, since the constant of PLL is changed with the output of the discriminating means, the stereo and various broadcasting are discriminated even under the weak electric field. |
