| 摘要 |
PURPOSE:To obtain a digital band-stop filter which can adjust the stop frequency freely, by constituting it of two delaying circuits having the NT delay time, a multiplier and two adders, in case when an integer except zero and a sampling period are denated cs N and T, respectively. CONSTITUTION:The outputs of the delaying circuits 3-1, 3-2 of the delay time NT, and the input signals are added by the adder 4. Also, the output of the circuit 3-1 is multiplied by the constant + or -alpha from the external part by the multiplier 5, and its output and the output of the adder 4 are added or subtracted by the adder 6, and the result is output to the terminal 2. The frequency characteristic of this circuit becomes 2cosNomegaT+ or -alpha(omega: angular frequency), and the stop angular frequency becomes omega=(2k-1)pi/NT(k=1, 2...). When alpha is selected and adjusted near to zero, the stop frequency can be finely adjusted, and when alpha is selected approximate to 2, the band frequency filter having a ripple in the stop band can be realized easily. |
