Simulating a FIR filter

Question

Rafael Ludtke 2019-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/467810-simulating-a-fir-filter

评论： Rafael Ludtke 2019-6-19

Hi,

I've found a lot of examples of how to use the fir1 function to calculate the FIR filter coeficients, but I need to define a input vector of samples, the coeficients and need as return the output vector.

I was able to use the filter function to simulate one sample, but I believe I should combine that with a conv function.

This is the diagram I need to simulate:

Where: x[n] is my input vector.

b[ tap_num ] is the coeficient vector.

y[n] is the output vector.

The "triangle" would be a multiplier between the input and b[ tap_num ];

As example, in a 5 tap filter, using an input like x = [ 0 0 0 1 1 1 1 1 ], and b = [ 1 1 1 1 1 ], the expected would be y = [ 1 2 3 4 5 4 3 2 ]

Whats the simpliest way to define the two input vectors ( x[n] and b[tap_num] ), and get an output vector?

Thank you!

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Answer 1

David Wilson 2019-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/467810-simulating-a-fir-filter#answer_379870

编辑：David Wilson 2019-6-19

Use the filter command. In this case your denominator, (A), coefficients are just 1.

x = [ 0 0 0 1 1 1 1 1 ]' % input  
b = [ 1 1 1 1 1 ];  
y = filter(b,1,x)

You will note that the solution above handles the initial conditions slightly differently than your proposed solution. However if this is important to you (hint: it shouldn't be unless this is a homework problem), then you need to use filtic to get them set to what you want.