> > Dear all, > I have a question regarding the usage of single_pole_iir_ff filter in the > fftsink_nongl.py which is used to construct the spectrum analyzer in > gnuradio-3.1.3. what is the usage of this iir filter since the alfa value is > equal to 1 which give the value of input the same as the value of the output > (refering to the single pole iir filter explanation in > https://radioware.nd.edu/documentation/a-dictionary-of-the-gnu-radio-blocks > -- please fixme if i am wrong). in the previous post, firas told that this > filter is used for the averaging purposes > (http://old.nabble.com/question-regarding-usrp_fft.py-td24440532.html#a24466469) > but what is the value that it average? > > ----- > Mohd Adib Sarijari > Universiti Teknologi Malaysia > www.fke.utm.my > www.utm.my > It averages the values in each of the bins.
If your FFT is 1024 wide, then you essentially have 1024 single-pole IIR filters, each computing the low-pass filtered version of the individual bins. This is called (at by me) spectral averaging. There will always be a certain amount of "noise" in spectral estimates, and for weak signals, averaging can bring out spectral features that would otherwise be hidden by the randomness of the noise floor. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
