Clarify FIR part and upsampling of synthesis filterbank.

applications/lofar2/model/pfb_bunton_annotated/polyphase_synthesis_b.m

@@ -27,15 +27,17 @@ end
 
 outData = (1:nof_blocks*Nstep + Ncoefs) * 0;
 for n = 1:nof_blocks
-    % Copy the data at each tap
+    % Copy the FFT data at each FIR tap
     temp2 = (1:Ncoefs) * 0;
     for m = 0:Ntaps-1
         temp2((1:Nfft) + m*Nfft) = temp(n, 1:Nfft);
     end
-    % Filter input using bfir as window
+    % Apply the FIR coefficients by using bfir as window
     temp2 = temp2 .* bfir;
-    % Overlap add to sum the taps, with upsampling rate Nstep
+
+    % Sum the FIR taps by overlap add the weighted input to the output.
+    % Progress with Nstep per block of Nfft to upsample by Nstep, to match
+    % the downsample by Nstep of the analysis filterbank.
     range = (1:Ncoefs) + (n-1)*Nstep;
-    outData(range) = outData(range) + temp2;  % for continuous time output
-    %outData(n,:) = temp2;  % for output in blocks
+    outData(range) = outData(range) + temp2;  % continuous time output
 end