Finite Impulse Response (FIR) Filter

In digital signal processing, an FIR is a filter whose impulse response is of finite period, as a result of it settles to zero in finite time. This is often in distinction to IIR filters, which can have internal feedback and will still respond indefinitely. The impulse response of an Nth order discrete time FIR filter takes precisely N+1 samples before it then settles to zero. FIR filters are?most popular kind of filters executed in software and these filters can be continuous time, analog or digital and discrete time. Special types of FIR filters are namely, Boxcar, Hilbert Transformer, Differentiator, Lth-Band and Raised-Cosine.

FIR Filter:

The term FIR abbreviation is “Finite Impulse Response” and it is one of two main types of digital filters used in DSP applications.?Filters are signal conditioners?and function of each filter is, it allows an AC components and blocks DC components. The best example of the filter is a phone line, which acts as a filter. Because, it limits frequencies to a rage significantly smaller than the range of human beings can hear frequencies.

There are various kinds of filters, namely LPF, HPF, BPF, BSF. A LPF allows only low frequency signals through tom its o/p, so this filter is used to eliminate high frequencies. A LPF is convenient for controlling the highest range of frequencies in an audio signal. An HPF is quite opposite to LPF. Because, it rejects only frequency components below some threshold. The best example of the HPF is, cutting out the 60Hz audible AC power, which can be selected up as noise associated almost any signal in the USA.

The alternative of IR filter is a DSP filter which can also be IIR. IIR filters uses feedback, so when you i/p an impulse the o/p theoretically rings forever. The terms used for describing IR filters are Tap, impulse response, MAC (multiply accumulate), delay line, transition band and circular buffer.

Design Methods of FIR Filter

The design methods of FIR filter based on approximation of ideal filter. The ensuing filter approaches the perfect characteristic because the order of the filter will increase, so creating the filter and its implementation additional complicated.

The design process starts with necessities and specifications the FIR filter. The method used in the design process of the filter depends upon the implementation and specifications. There are many advantages and disadvantages of the design methods. Thus, it is very significant to elect the right method for FIR filter design. Due to efficiency and simplicity of the FIR filter, most commonly window method is used. The other method sampling frequency method is also very simple to use, but there is a small attenuation in the stopband.