The number of stages(S) in direct form FIR filter is given as: S=integer (K*Fs / Δf)
Where Fs = Sampling Frequency, Δf = Filter transition band, K= 3 (assume)
If x(n) is signal with frequency range 0-2.4 MHz and sampled at Fs = 400 MHz and it is filtered by:
Assumptions:
- Pass-band Frequency LPF(1): 1.8 MHz, Stop-band Frequency LPF(1): 4 MHz
- Pass-band Frequency LPF(2): 1.8 MHz, Stop-band Frequency LPF(2): 2 MHz
- Both filters are having flat pass-bands and stop-bands
- Pass-band attenuation of both filters = 0 dB and stop band attenuation of both filters is infinity.
Calculate total no. of stages SLPF1 +SLPF2
1
120
2
545
3
555
4
665