| 摘要 |
PURPOSE:To make an excellent separation into right and left channels by controlling a subcarrier generating circuit by adding the multiplication output of a stereophonic composite signal and a signal pi/2 out of phase with the subcarrier signal to the stereophonic composite signal by a stereophonic demodulating circuit. CONSTITUTION:A stereophonic composite signal is inputted from terminal 1 to multiplier 8, which multiplies a subcarrier signal, appearing at the output of half frequency divider 3d, by a pi/2 out-of-phase signal from phase shifter 9; and the output is added to the stereophonic composite signal by adder 7, whose output is supplied to phase detector 3a of phase synchronous loop circuit 3 by way of band- pass filter 2. Its output is passed through low-pass filter 3b to eliminate the supply of a low frequency component, causing a phase shift to voltage control oscillator 3C and from the output of half frequency divider 3d, a stable subcarrier can be obtained without a phase shift. Then, the stereophonic composite signal is switched through circuit 4 by the above-mentioned signal, so that right and left channel signals of good separation can be obtained from terminals 5 and 6. |
