| 摘要 |
PURPOSE:To set a reception band and selectivity sufficiently, by detecting through a low-pass filter a signal containing a modulated signal obtained by multiplying an intermediate frequency signal by another intermediate frequency signal synchronizing with it. CONSTITUTION:Multiplier 2 multiplies the output of adding circuit 1 by that of phase shifter 6 which makes a 90 deg. phase shift for eliminating a phase shift and then outputs the product to low-pass filter 7. Limiter circuit 3 limits the amplitude of the output of circuit 1 to eliminate its AM component. Prescribed passing-band filter 4 limits the band of the output of circuit 3 according to its characteristics. Phase- locked loop circuit 5 output the signal that synchronizes with the output signal of filter 4. This signal is 90 deg. phase shift with the input signal. The output of circuit 5 is sent to phase shifter to eliminate the shift. |
