| 摘要 |
PURPOSE:To have an extremely high degree of channel selection, by using a band pass filter having a sharp pass characteristics. CONSTITUTION:Both center frequency of a desired wave and frequency of a local osillator 30 are set at omega1, and therefore the center frequencies of band pass filters 51 and 52 are also set at omega1. At the same time, the ideal characteristics are set for these filters. Here the outputs of the filters 51 and 52 are set as R1T=A1sin(omega1+st) and R2t=A2cos (omega1t+st) respectively. The outputs of differentiating circuit 61 and 62 are shown by equations 1 and 2. Therefore the output of a multiplier circuit 71 is shown by an equation 3, and the output of a multiplier circuit 72 is shown by an equation 4. Therefore the output of a subtractor circuit 73 is shown by an equation 5. Then a transmitting signal (vt) can be demodulated by deleting which is a constant. In such a way, the degree of channel selection can be extremely increased by using such filters having sharp pass characteristics. |
