Contents
What are the different types of FIR filter?
Special types of FIR filters are namely, Boxcar, Hilbert Transformer, Differentiator, Lth-Band and Raised-Cosine.
What is FIR filter order?
The order of a filter is defined as the order of its transfer function, as discussed in Chapter 6. For FIR filters, this is just the order of the transfer-function polynomial. Thus, from Equation (5.8), the order of the general, causal, length FIR filter is (provided ).
What are FIR filters in audio?
Two audio filter types are typically used: IIR and FIR. IIR stands for Infinite Impulse Response and FIR stands for Finite Impulse Response. The IIR filter is common and can be used in the passive/analog domain and in a digital signal processor (DSP).
When to use Type 3 or 4 of FIR filter?
The filters with anti-symmetrical impulse response all have a zero at z = 1 (i.e. frequency 0). So if you need to implement a high-pass filter or derivative-like filter (or even band-pass), then you must go for types 3 and 4. Similarly, if your filter is a low-pass type, then types 1 and 2 apply.
What kind of phase shift does a FIR filter have?
Type III filters (odd number of taps, odd symmetry) always have zeros at z = 1 and z = − 1 (i.e. at f = 0 and f = f s / 2 ), they have a 90 degrees phase shift, and an integer group delay. Type IV filters (even number of taps, odd symmetry) always have a zero at z = 1, a phase shift of 90 degrees, and a non-integer group delay.
What’s the minimum number of zeros for a Type 3 filter?
For type 3 filters, it is mandatory to have a odd number of zero at z = 1 and z = -1. And middle sample value is 0. Because of the presence of the zeros at z = -1 and z= 1 these filters can only be used to design band pass filters. They do not allow low and high frequencies to pass through.
What are the requirements for a type 2 filter?
This satisfies requirements for type 1 filter. Type 2 filters have the even length. Because of even length, they are symmetric around imaginary axis. For such filters, it is mandatory to have an odd number of zero at z = 1 and even or no zeros at z = -1. The zero at z= – 1 also imposes restriction on its design for High Pass filter.