Ben Olsen wrote: > Hello, > > I have a bit of a confusion concerning the decimating Channel filter > in the stock receive_path.py script that I'm using with the GMSK rx > and tx python script: > > The filter coefficients for the chan_filt filter are determined by the > gr.firdes.low_pass() function, which takes, among other arguments, the > midpoint and the width of the transition band. In the gr_firdes.h > file it is specified that the units for these arguments is Hz, but in > the code it says that the midpoint of the trans. band is "1.0". The > script correctly receives data on a much larger band than 1 Hz, so > what am I missing? Is the value somewhere being changed to designate > a different value at the filter's level? In many instances we use a normalized frequency, since these are sampled systems. A normalized frequency of 1.0 is equal to the sampling rate. You can think of the units as cycles per sample. The first nyquist zone would be from 0 to 0.5 if these are real samples, or -0.5 to 0.5 if these are complex samples. You
In some other instances we may use radians per sample, which would be 2PI times the normalized frequency. Matt _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
