Rectangular windowing function Digital Signal Processing--FIR Digital Filter Design .Its spectrum W(w) w(n)= 0≤n≤N-1 >The period is w=2T. 0 otherwise >The height of the main lobe is N-1 m,(e)= 1-w N and its bottom width is 4T/N. 1=0 1-1 >The height of the first side lobe N is about 2N/3TTat w=3TT/N. W(o)= ∑ea sin(No/2 e-j(N-1)o/2 n=0 sin(@/2) >The attenuation of side lobe is approximately 13dB. H(o)= in(No/2) >The zero-cross points are sim(o/2） ωk=2kTN,k=士1，±2，， ↑H(o) ±(N-1). .Frequency leakage:because of sharp transition of window edges. .Frequency resolution:because of the 2T/N3dB-width of the main lobe. 上浒究通大粤Digital Signal Processing—— FIR Digital Filter Design Rectangular windowing function •Its spectrum W(ω) The period is ω=2π. The height of the main lobe is N and its bottom width is 4π/N. The height of the first side lobe is about 2N/3πat ω=3π/N. The attenuation of side lobe is approximately 13dB. The zero-cross points are ωk=2kπ/N, k=±1, ±2,…, ±(N-1). •Frequency leakage: because of sharp transition of window edges. •Frequency resolution: because of the 2π/N3dB-width of the main lobe