- #1

btb4198

- 557

- 9

all the pages I have seen use mat lab in their example.

So I have been reading up on FIR filters and I have learned they can be in the Time domain or the frequency domain. in the Time domain you take the input signal of discrete samples x[n] and its impulse response b and you use convolving to get the output y[n]. this will Zero out any unwanted frequencies. so you can do a band pass or a low pass or a high pass filter.

N

y[n] = Ʃ bi x[N-i]

i = 0

Now I do not really know how to solve the impulse response h[n].

now Wiki says, " h[n] can be calculated if we set x[n] = δ[n] in the above relation, where δ[n] is the Kronecker delta impulse. The impulse response for an FIR filter then becomes the set of coefficients bn, as follows :

N

h[n] = Ʃ bi δ[n-i] = bn

i = 0

for n =0 to N

"

so I am not sure where h[n] come in at in that 1 formula ... I think h[n] is an array of bns.. i guess

or a set of bn .

like h[n] = { b1, b2, b3, b4,bi, ..}

that might be wrong...

"To design a filter means to select the coefficients such that the system has specific characteristics." wiki

"In signal processing, a window function (also known as an apodization function or tapering function[1]) is a mathematical function that is zero-valued outside of some chosen interval." wiki

but from this I still do not know how to get the right coefficients bn.

I know that

ω = 2π F/fs

Δω = 2π TW/Fs

Tw = transition width with "is a range of frequencies, that allows a transition between a passband and a stopband of a signal processing filter. The transition band is defined by a passband and a stopband cutoff frequency or corner frequency." wiki

stopband ripple = -20log10 δ

after this I get really lost...

I do get how convolve works,

http://www.eas.uccs.edu/wickert/ece2610/lecture_notes/ece2610_chap5.pdf

page 12 has a good example...

you would use convolving on h[n] and x[n] right?

but I am not sure how to get h[n]

so can someone workout an example by hand to help feel in the blanks

thanks

also if I have said something wrong in his post please tell me

thanks