| 摘要 |
PURPOSE:To decrease the necessary number of filters by successively selecting the outputs of band-pass filters which have divided bands of signals, and then detecting the side band of a signal obtained by mixture with the output of a frequency variable oscillator. CONSTITUTION:The output of a detector 5 is amplified by a part 7 and then inputted to a filter band 14 consisting of l units of wind-band-pass filters 13-1- 13-l. The outputs of the filters 13-1-13-l are inputted to an electronic switch 15, which selects and input the output of one filter 13-i among the filters 13-1- 13-l to a mixer 10. It is mixed with the output of a frequency variable oscillator 17 to be converted into a signal having a difference frequency between the both, and the signal is inputted to a filter bank 8 consisting of (m) units of narrow- band-pass filters 9. Then, a simple logical circuit discriminates the frequency of signal light on the basis of the output of each detector 12 and that of a controller 16. |
