X-Git-Url: https://adrianiainlam.tk/git/?p=4yp.git;a=blobdiff_plain;f=rxFilter.m;h=e8e572af85f43b60f586be8dc2694fbe9525fdcb;hp=eb25a32d2ca52449e03f19e43ae864cde0de8454;hb=5fae00773184080617ac022c07495d365975e0e1;hpb=427465905320390cebf3d247b8beace19387c70f

diff --git a/rxFilter.m b/rxFilter.m
index eb25a32..e8e572a 100644
--- a/rxFilter.m
+++ b/rxFilter.m
@@ -8,13 +8,23 @@ function r = rxFilter(y, rolloff, span, sps)
   %% Output:
   %%  - r: filtered signal (energy not normalized),
   %%       normalize and then sample.
-  filter = comm.RaisedCosineReceiveFilter...
+  rxfilter = comm.RaisedCosineReceiveFilter...
                  ('Shape', 'Square root', ...
                   'RolloffFactor', rolloff, ...
                   'FilterSpanInSymbols', span, ...
                   'InputSamplesPerSymbol', sps, ...
-                  'DecimationFactor', 1);
+                  'DecimationFactor', 4, ...
+                  'DecimationOffset', mod(span+1, 4));
 
-  r = filter([y; zeros(span * sps, 1)]);
-  r = r(span * sps / 2 + 1 : end); % truncate filter transients
+  coef = coeffs(rxfilter);
+  filter_fft = fft(coef.Numerator, length(y));
+  y_fft = fft(y);
+
+  rs = ifft(y_fft .* filter_fft.');
+
+  %% re-order signal due to circular conv
+  l = (length(coef.Numerator) - 1) / 2;
+  rr = [rs(l:end); rs(1:l-1)];
+
+  r = downsample(rr, 4, 3);
 end