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[Commit-gnuradio] r8185 - gnuradio/trunk/gnuradio-core/src/utils
From: |
jcorgan |
Subject: |
[Commit-gnuradio] r8185 - gnuradio/trunk/gnuradio-core/src/utils |
Date: |
Fri, 11 Apr 2008 13:47:55 -0600 (MDT) |
Author: jcorgan
Date: 2008-04-11 13:47:54 -0600 (Fri, 11 Apr 2008)
New Revision: 8185
Added:
gnuradio/trunk/gnuradio-core/src/utils/cic_comp_taps.m
Modified:
gnuradio/trunk/gnuradio-core/src/utils/Makefile.am
Log:
Added CIC compensation filter tap generator. Useful when working without the
half-band filter in the USRP.
Modified: gnuradio/trunk/gnuradio-core/src/utils/Makefile.am
===================================================================
--- gnuradio/trunk/gnuradio-core/src/utils/Makefile.am 2008-04-11 15:50:32 UTC
(rev 8184)
+++ gnuradio/trunk/gnuradio-core/src/utils/Makefile.am 2008-04-11 19:47:54 UTC
(rev 8185)
@@ -22,6 +22,7 @@
include $(top_srcdir)/Makefile.common
EXTRA_DIST = \
+ cic_comp_taps.m \
db_width.m \
filter_tools.m \
plot_freq_response.m \
Added: gnuradio/trunk/gnuradio-core/src/utils/cic_comp_taps.m
===================================================================
--- gnuradio/trunk/gnuradio-core/src/utils/cic_comp_taps.m
(rev 0)
+++ gnuradio/trunk/gnuradio-core/src/utils/cic_comp_taps.m 2008-04-11
19:47:54 UTC (rev 8185)
@@ -0,0 +1,45 @@
+#
+# Copyright 2008 Free Software Foundation, Inc.
+#
+# This file is part of GNU Radio
+#
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING. If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+
+# See Altera Application Note AN455
+#
+# R = decimation factor, 8-256
+# Fc = passband (one-sided) cutoff frequency
+# L = number of taps
+
+function taps = cic_comp_taps(R, Fc, L)
+ M = 1; %% Differential delay
+ N = 4; %% Number of stages
+ B = 18; %% Coeffi. Bit-width
+ Fs = 64e6; %% (High) Sampling freq in Hz
before decimation
+ Fo = R*Fc/Fs; %% Normalized Cutoff freq;
0<Fo<=0.5/M;
+ p = 2e3; %% Granularity
+ s = 0.25/p; %% Step size
+ fp = [0:s:Fo]; %% Pass band frequency samples
+ fs = (Fo+s):s:0.5; %% Stop band frequency samples
+ f = [fp fs]*2; %% Normalized frequency samples;
0<=f<=1
+ Mp = ones(1,length(fp)); %% Pass band response; Mp(1)=1
+ Mp(2:end) = abs( M*R*sin(pi*fp(2:end)/R)./sin(pi*M*fp(2:end))).^N;
+ Mf = [Mp zeros(1,length(fs))];
+ f(end) = 1;
+ h = fir2(L,f,Mf); %% Filter length L+1
+ taps = h/sum(h); %% Floating point coefficients
+endfunction
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