X-Git-Url: https://adrianiainlam.tk/git/?a=blobdiff_plain;f=txFilter.m;h=10c387d627fca406299162b9bcc7189a5bfe37f9;hb=d9a5ae9d4e5369f11357d1f5825acc379fbe7e52;hp=49164d37f0c1ae811f8b29fd92c2d4a025da80a8;hpb=1eeb62fbc496ed5c170d199143ad53e28122d29c;p=4yp.git

diff --git a/txFilter.m b/txFilter.m
index 49164d3..10c387d 100644
--- a/txFilter.m
+++ b/txFilter.m
@@ -8,10 +8,17 @@ function x = txFilter(modData, rolloff, span, sps)
   %% Output:
   %%  - x: pulse-shaped waveform
 
-  filter = comm.RaisedCosineTransmitFilter...
+  txfilter = comm.RaisedCosineTransmitFilter...
                ('Shape', 'Square root', ...
                 'RolloffFactor', rolloff, ...
                 'FilterSpanInSymbols', span, ...
-                'OutputSamplesPerSymbol', sps);
-  x = filter([modData; zeros(span, 1)]);
+                'OutputSamplesPerSymbol', sps, ...
+                'Gain', sqrt(sps)); % so that output has energy 1
+
+  coef = coeffs(txfilter);
+  filter_fft = fft(coef.Numerator, length(modData) * sps);
+  modData_fft = fft(upsample(modData, sps));
+  x = ifft(modData_fft .* filter_fft.');
+  l = (length(coef.Numerator) - 1) / 2;
+  x = [x(l:end); x(1:l-1)];
 end