5Finite Impulse Response (FIR) Filters
Digital FIR filters are discrete linear time-invariant systems in which an output number, representing a sample of the filtered signal, is obtained by weighted summation of a finite set of input numbers, representing samples of the signal to be filtered. The coefficients of the weighted summation constitute the filter’s impulse response and only a finite number of them take nonzero values. This is a “finite memory” filter – that is, it determines its output as a function of input data of limited age. It is frequently called a non-recursive filter because, unlike the infinite impulse response filter, it does not require a feedback loop in its implementation.
The properties of FIR filters will be illustrated by two simple examples.
5.1 FIR Filters
Consider a signal x(t) represented by its samples x(nT), taken at frequency fs = 1/T, and examine the effect on its spectrum of replacing the set x(nT) with the set y(nT) defined by the equation:
This set is also obtained by sampling the signal y(t) such that:
If Y(f) and X(f) denote the Fourier transforms of the signals y(t) and x(t), then:
Such an operation corresponds to the transfer ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access