Fast FIR Filter: Removing Linear Phase & Minimizing Distortion

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In summary, the conversation discusses the removal of linear phase introduced by windowing in an FIR filter and minimizing distortion in case of non-linear phase. The person asking for help is advised to provide more information and their own efforts in order to receive assistance. Later, they mention that they have found the solution, which involves advancing the signal before sending it through the filter to cancel out the delay and return the signal to time zero.
  • #1
jeezus
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hi.
in an FIR filter how do you remove the linear phase introduced by windowing?
also if the phase is non linear how can the distortion be minimized?
could someone please reply asap i badly need help with this. thanx
 
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  • #2
Welcome to the PF. This sounds like homework, so I moved it from the general EE forum to the appropriate homework forum.

You need to show us a little more of your own work and thoughts in order for us to help you. For example, what effect does the length of the filter have on the distortions you are asking about? Why does length affect the distortions? What method are you using to calculate the FIR coefficients, and why use that method over others?
 
  • #3
it's alright . i found the answer. apparently you just need to advance the signal before sending it through the filter. that way the delay of the filter cancels out with the advance and your signal ends up back at time zero.
 

FAQ: Fast FIR Filter: Removing Linear Phase & Minimizing Distortion

What is a Fast FIR filter?

A Fast FIR (Finite Impulse Response) filter is a digital signal processing technique used to remove unwanted noise or interference from a signal. It works by convolving the input signal with a finite impulse response, which is a series of coefficients that determine the filter's frequency response.

How does a Fast FIR filter remove linear phase?

A Fast FIR filter can remove linear phase by using symmetric impulse responses. This means that the filter coefficients are mirrored around the center, resulting in a linear phase response. Linear phase is desirable because it ensures that all frequencies in the input signal are delayed by the same amount, preserving the shape of the signal.

What is distortion and how does a Fast FIR filter minimize it?

Distortion is any unwanted change or alteration to a signal. In the context of a Fast FIR filter, it refers to any changes to the signal's amplitude or phase caused by the filtering process. A Fast FIR filter minimizes distortion by using a linear phase response and by carefully selecting the filter coefficients to ensure that the desired frequencies are not attenuated or distorted.

What are the benefits of using a Fast FIR filter?

Fast FIR filters have several benefits, including fast processing times, efficient use of memory, and the ability to achieve high filter orders (i.e. more precise filtering). They can also be designed to have a linear phase response, which is important for preserving the shape of the input signal. Additionally, Fast FIR filters are versatile and can be used for a variety of signal processing applications.

How are filter coefficients determined in a Fast FIR filter?

There are various methods for determining filter coefficients in a Fast FIR filter. One common approach is to use a windowing function, such as the Hamming or Kaiser window, to shape the filter's frequency response and then apply an inverse discrete Fourier transform (IDFT) to obtain the filter coefficients. Other methods include optimization techniques and filter design algorithms, such as the Parks-McClellan algorithm.

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