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#1




Working of Digital filters...
I was just thinking how Digital filters work in case of analog we just connected
RC to the signal input to amplifiers, etc but in case of Digital filter....what happen?? Thanks 
#2




In an FIR (Finite Impulse Response) filter the present output is a function of the current and previous inputs. If the input goes away then the output goes away. That is the 'F' in FIR.
In an IIR (Infinite Impulse Response) filter the present output is a function of the current and previous inputs AND the previous outputs. If the input goes away the out does not have to go away. That is the first 'I' in IIR. Finite and Infinite Impusle Response refers to the output over time, NOT the amplitude of the response.
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#3




For a digital filter you first convert the analog signal to digital format by sampling the signal at greater than the Nyquist samplerate for the highest analog frequency using an A/D converter. A digital processor then takes these samples and performs a mathematical function of the values to generate the desired filter response for each sample. If desired the samples from the filter can be then converted back to analog with a D/A converter.
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#4




In case of analog low pass filter with connect R and C by using cut of frq. F=1/(2*PI*R*C)....and analyzing by Bode plot.
But this how really work in digital filters?? The input isin form of 010101010 if i want low freq. output of digital signal then what to do?? 
#5




Quote:
For more info look at one of these Google references.
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#6




It works the same way except there is no R and no C. What you do have control of is the sample rate and the coefficients of the impulse response. If you know the coefficients of the impulse response you can compute the output via convolution.
http://www.dspguide.com/ I think Prof. Smith's book is still a free download by chapters in PDF format
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#7




Guys can you just give an block example for better understanding of digital filters..??

#8




Quote:
Here is another one http://en.wikipedia.org/wiki/Finite_impulse_response Boxcar filters have a lowpass characteristic similar to the multipole RC filter. When you do some reading it will lead to more specific questions.
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We never have time to do it right, But we always have time to do it over. Last edited by Papabravo; 10222011 at 09:00 PM. 
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#9




I think i am know getting how digital filters work as first we convert analog to Digital then uC/uP do calculation like FFT,etc then output is converted analog.......
But if we talk about convolution theorem it say multiply in freq. domain, vice versa...but what the use and how does it happen in CPU itself?? 
#10




A digital filter is implemented in a CPU by a succession of multiply and accumulate (add) operations. In some processors there is even an instruction that does exactly that operation called "Multiply and Accumulate". A processor can also keep track of previous inputs and previous outputs which may also be used in the filter calculations. Was that what you were looking for?
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