diff options
| author | Tom Rondeau <tom@trondeau.com> | 2013-10-06 15:35:55 -0400 |
|---|---|---|
| committer | Tom Rondeau <tom@trondeau.com> | 2013-10-06 16:32:57 -0400 |
| commit | 8323e2de03c77796fe11f6f47bd4173f6b2a2ca9 (patch) | |
| tree | 9def797152a406e8f3f8f9d09cbf82e39993ae86 | |
| parent | fc2253f8db42dc184dad2db072347c942b0ed9fe (diff) | |
filter: fixing windows functions.
Both Kaiser and Blackman windows were wrong. Fixed according to equations in Oppenheim and Schafer. Thanks to Chris Sylvain (KB3CS) for pointing out issues with the Kaiser window.
Added Barlett (triangular) window.
| -rw-r--r-- | gr-filter/include/gnuradio/filter/firdes.h | 1 | ||||
| -rw-r--r-- | gr-filter/lib/firdes.cc | 36 |
2 files changed, 21 insertions, 16 deletions
diff --git a/gr-filter/include/gnuradio/filter/firdes.h b/gr-filter/include/gnuradio/filter/firdes.h index bd09cd801d..d2ab23d186 100644 --- a/gr-filter/include/gnuradio/filter/firdes.h +++ b/gr-filter/include/gnuradio/filter/firdes.h @@ -48,6 +48,7 @@ namespace gr { WIN_KAISER = 4, //!< Kaiser window; max attenuation a function of beta, google it WIN_BLACKMAN_hARRIS = 5, //!< Blackman-harris window WIN_BLACKMAN_HARRIS = 5, //!< alias to WIN_BLACKMAN_hARRIS for capitalization consistency + WIN_BARTLETT = 6, //!< Barlett (triangular) window }; diff --git a/gr-filter/lib/firdes.cc b/gr-filter/lib/firdes.cc index f56bdc80f5..dd3c124565 100644 --- a/gr-filter/lib/firdes.cc +++ b/gr-filter/lib/firdes.cc @@ -1,6 +1,6 @@ /* -*- c++ -*- */ /* - * Copyright 2002,2007,2008,2012 Free Software Foundation, Inc. + * Copyright 2002,2007,2008,2012,2013 Free Software Foundation, Inc. * * This file is part of GNU Radio * @@ -760,8 +760,8 @@ namespace gr { case WIN_BLACKMAN: for(int n = 0; n < ntaps; n++) - taps[n] = 0.42 - 0.50 * cos((2*M_PI * n) / (M-1)) - - 0.08 * cos((4*M_PI * n) / (M-1)); + taps[n] = 0.42 - 0.50 * cos((2*M_PI * n) / M) + + 0.08 * cos((4*M_PI * n) / M); break; case WIN_BLACKMAN_hARRIS: @@ -771,20 +771,24 @@ namespace gr { break; case WIN_KAISER: - { - double IBeta = 1.0/Izero(beta); - double inm1 = 1.0/((double)(ntaps)); - double temp; - //fprintf(stderr, "IBeta = %g; inm1 = %g\n", IBeta, inm1); + { + double IBeta = 1.0/Izero(beta); + double inm1 = 1.0/((double)(ntaps-1)); + double temp; - for(int i=0; i<ntaps; i++) { - temp = i * inm1; - //fprintf(stderr, "temp = %g\n", temp); - taps[i] = Izero(beta*sqrt(1.0-temp*temp)) * IBeta; - //fprintf(stderr, "taps[%d] = %g\n", i, taps[i]); - } - } - break; + for(int i = 0; i <= ntaps; i++) { + temp = 2*i*inm1 - 1; + taps[i] = Izero(beta*sqrt(1.0-temp*temp)) * IBeta; + } + } + break; + + case WIN_BARTLETT: + for(int n = 0; n <= ntaps/2; n++) + taps[n] = 2*n / (float)M; + for(int n = ntaps/2 + 1; n < ntaps; n++) + taps[n] = 2 - 2*n / (float)M; + break; default: throw std::out_of_range("firdes:window: type out of range"); |