DESIGN AND IMPLEMENTATION OF FIR LOW PASS FILTER - A CASE STUDY ON THE EFFECTS OF INITIAL COEFFICIENT VALUE TO ACHIEVE THE DESIRED FILTER OUTPUT

The usage of filter is inevitable in most of the electronics devices to reject all unwanted high frequencies of electrical signal & pass the desired signal and for this purpose a precision filter is to be used in the input stage of the device. In an R-C Low Pass Filter capacitive reactance varies with the applied frequency of the input signal. When the applied frequency of the input signal increases the capacitive reactance is decreased and high frequency signal is bypassed to the ground through the capacitor. But in the case of FIR Low Pass Filter, the unwanted high frequency signal is suppressed with the help of filter coefficients. The desired output of an FIR Low Pass Filter can be obtained when the sample values of the input signal are instantaneously processed with the corresponding coefficient values. This case study shows that the initial value h(0) of the filter coefficients has a vital role to achieve the desired filter output. Though initial value h(0) is undefined and can be calculated by L. Hospitals' Rule after multiplication with a window function.