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Re: [Discuss-gnuradio] FIR filter in fsk_tx.py
From: |
Sachi |
Subject: |
Re: [Discuss-gnuradio] FIR filter in fsk_tx.py |
Date: |
Sun, 26 Jun 2005 23:01:35 -0700 (PDT) |
Let me make my question more clear.
If I understand the code correctly, after
"bytes_to_syms", the signal should be a float sequence
of +1 or -1. I am very confused about what the signal
will look like after "interp". I think it's no longer
+-1 sequence any more. So does it have any special
function here?
Here are several problems invloved.
For the FIR interpolation filter, why we choose
1.2*data_rate/2 as the cutoff frequency and
0.4*data_rate/2 as the transition band?
Second, why k = 2 * math.pi * max_deviation / self.fs?
Hope anyone of you could help me get out of the
confusion.
Thanks for your time
Sachi
--- Sachi <address@hidden> wrote:
> Hi, Eric
>
> I've got a question on the interpolation FIR filter
> in
> the fsk_tx.py. Here is the filter uesd:
>
> interp_taps = gr.firdes.low_pass (self.sw_interp,
>
> # gain
>
> self.fs, # sampling rate
>
> data_rate / 2 * 1.2, # cutoff
>
> data_rate/2 * 0.4, # trans width
>
> gr.firdes.WIN_HANN)
>
> I am a little confused. Why do you use sw_interp as
> the gain? And how do you select the cutoff freq. and
> transition bandwidth?
>
> Thanks in advance
>
> Sachi
>
>
>
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