| 摘要 |
PURPOSE:To omit the lead filter and thus realize the low cost by making pass through the low pass filter the output obtained through the multiplication of the signal based on the pilot signal and the AM detection output of the pilot signal by means of the PLL. CONSTITUTION:The pilot signal extracted from band pass filter 6 is applied to the PLL circuit consisting of phase detection circuit 12, low pass filter 13 and voltage control type oscillation circuit 14 each and via divider circuit 11. And the oscillation output of the PLL circuit is divided through divider circuits 16 and 17 to deliver the frequency signals of 920Hz and 980Hz each. On the other hand, the pilot signal is applied to AM detection circuit 9, and this detection output (922.5Hz or 982.5Hz) is supplied to multiplier circuits 18 and 19 along with the output of circuits 16 and 17 to perform the frequency conversion. Then the detection output is made to pass through low pass filters 20 and 21 which makes the differential beat signal pass, thus obtaining the program identification signal. |
