| 摘要 |
PURPOSE:To narrow a required frequency band by using a signal obtained only when a scrambling waveform is inputted with a surface acoustic wave filter having a reed screen-like electrode so as to attain descrambling. CONSTITUTION:The scrambling waveform is inputted to a BPF15 via an input terminal IN and after spurious wave is eliminated, the result is inputted to a modulator 8 via a primary mixer 2, a delay circuit 16, an amplifier 5 and a secondary mixer 6. On the other hand, an output of the BPF15 is inputted from a terminal A to a surface acoustic wave filter 17. The filter 17 has a reed screen-like electrode having a similar pattern form as the scrambled waveform and outputs an impulse signal only when the scrambling waveform is inputted. This signal is inputted to the modulator 8 via an amplifier 10, a detector 11 and a Schmitt trigger circuit 12, and the scrambling waveform is descrambled and outputted from an output terminal OUT. |
