7.2. 1 Windows function method o A causal Fir filter with an impulse response h[n] can be derived from ht[n] by delaying the latter sequence by M samples, that is, by forming h[] =h[n-M o The causal filter h[n has the same magnitude esponse as that of the noncausal filter ht[n] and its phase response has a linear phase shift of oM ridians with respect to that of the noncausal filter7.2.1 Windows function method  A causal FIR filter with an impulse response h[n] can be derived from ht[n] by delaying the latter sequence by M samples, that is, by forming h n h n M   = − t    The causal filter h[n] has the same magnitude response as that of the noncausal filter ht[n] and its phase response has a linear phase shift of ωM ridians with respect to that of the noncausal filter