Merge pull request #1219 from dl2kcd/fix-ddc-aliasing

use Blackman-Harris window in ddc to reduce aliasing
gqrx-sdr · Apr 13, 2023 · fe41c7f · fe41c7f
2 parents 803b90e + 675c547
commit fe41c7f
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diff --git a/resources/news.txt b/resources/news.txt
@@ -7,6 +7,7 @@
      FIXED: Remove empty frame from bottom of I/Q tool window.
      FIXED: Sudden scrolling of file list in I/Q tool window.
      FIXED: Reset zoom slider after right click on panadapter / waterfall.
+     FIXED: Aliasing when input rate is higher than 2 Msps.
   IMPROVED: AGC performance.
   IMPROVED: WFM stereo & OIRT performance.
   IMPROVED: Apply amplitude normalization to FFT window functions.

diff --git a/src/dsp/downconverter.cpp b/src/dsp/downconverter.cpp
@@ -93,7 +93,13 @@ void downconverter_cc::update_proto_taps()
     if (d_decim > 1)
     {
         double out_rate = d_samp_rate / d_decim;
-        filt->set_taps(gr::filter::firdes::low_pass(1.0, d_samp_rate, LPF_CUTOFF, out_rate - 2*LPF_CUTOFF));
+        filt->set_taps(gr::filter::firdes::low_pass(1.0, d_samp_rate, LPF_CUTOFF, out_rate - 2*LPF_CUTOFF,
+#if GNURADIO_VERSION < 0x030900
+            gr::filter::firdes::WIN_BLACKMAN_HARRIS
+#else
+            gr::fft::window::WIN_BLACKMAN_HARRIS
+#endif
+        ));
     }
 }