From d6d617c72285aa1f562be1e5b405bb38ec3ecf66 Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Wed, 14 Aug 2024 09:54:47 +0200
Subject: [PATCH] Clarify FIR part and upsampling of synthesis filterbank.
---
.../pfb_bunton_annotated/polyphase_synthesis_b.m | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/applications/lofar2/model/pfb_bunton_annotated/polyphase_synthesis_b.m b/applications/lofar2/model/pfb_bunton_annotated/polyphase_synthesis_b.m
index 3e1ae4f366..c13e920b95 100644
--- a/applications/lofar2/model/pfb_bunton_annotated/polyphase_synthesis_b.m
+++ b/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
--
GitLab