| 摘要 |
A non-recursive discrete filter for simultaneously realizing for example two band-pass filter characteristics starting from a given lowpass transfer characteristic, wherein one bandpass filter has an in-phase transfer characteristic and the other filter the quadrature transfer characteristic of this in-phase filter. The central frequency of these filters is fo and the output sampling frequency is fs = 8fo. This discrete filter comprises multiplying means in which input signal samples x(n) are modified by an associated filter coefficient a(i) for generating modified input signal samples z(n,i) = a(i)x(n-i). The coefficients a(i) are the same for both transfer characteristics and are given by: a(i) = h1(i) ¦ cos ( pi i/4) ¦ for cos( pi i/4) NOTEQUAL 0 a(i) = h 1(i) ¦ sin ( pi i/4) ¦ for cos( pi i/4) = 0 WHEREIN H1(I) REPRESENTS THE DISCRETE IMPULSE RESPONSE OF THE LOWPASS FILTER. |
