24-12-2012, 12:45 PM
DESIGN OF IIR BUTTERWORTH LPF
AIM
Write a program in C and MATLAB to design IIR BUTTERWORTH low pass filter for the given specifications pass band frequency, stop band frequency, gain at pass band frequency and gain at stop band frequency. Verify the same on TMS 320 C 67113DSP kit, MATLAB.
TOOLS REQUIRED :
2.1 TMS 320C 6713 Kit,
2.2 Full version CCS s/w,
2.3 DSK 6713 s/w,
2.4 MATLAB s/w.
THEORY:
The filters designed by considering all the infinite samples of impulse response are called IIR filters. It is a discrete time system that is designed to pass the spectral contents of the input signal in a specified band of frequencies. There are so many approximation solutions to design digital filters, among them popular approximations
1. BUTTERWORTH approximation
2. CHEBYSHEV approximation
Here. First we have to design analog filters, then by using transformation techniques we can obtain digital filter transfer function. There are two types of transformation techniques.
1. Impulse Invariant Transformation
2. Bilinear Transformation
DESIGN PROCEDURE:
Following steps were required to design a digital CHEBYSHEV LPF
Take the specifications of desired Low Pass Filter
P = Pass band frequency corresponding to the analog filter frequency P
S = Stop band frequency corresponding to the analog filter frequency S
AP = Gain at Pass band frequency P
AS = Gain at Stop band frequency S
Choose either Impulse Invariant or Bilinear Transformation(IIT/BT) and calculate the frequency ratio