| 摘要 |
PURPOSE:To make unnecessary the filter in PLL, to speed up the response time of PLL and to make broad the drawing-in range, by giving an input signal to a filter to pick up desired signal only and supplying the output of the filter to PLL. CONSTITUTION:The input signal from the input terminal 1 and the signal from the local oscillator 3 are fed to a converter 2 to output the 1st IF signal to the output of the converter 2, and the filter 4 picks up the desired frequency only, and the output is divided into two. One signal picked up is fed to the filter 2 where the frequency band of maximum range in variation of the desired signal passes through, and the output picked up at this filter 12 is fed to the converter 13 of PLL17 consisting of the converter 13, voltage controlled oscillator VCO16 and phase detector 14. Further, the response speed can be increased without providing a filter in PLL17, the width of drawing is widened, the output of VCO16 is fed to a converter 5 and the 2nd IF signal is output with the output of the filter 4. |
