From e3c0da82c9c207b019dd1e2bb33aa930e7039fae Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Mon, 19 Aug 2024 08:23:45 +0200
Subject: [PATCH] Clarify SNR.
---
.../lofar2/model/pfb_bunton_annotated/reconstruct.m | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/applications/lofar2/model/pfb_bunton_annotated/reconstruct.m b/applications/lofar2/model/pfb_bunton_annotated/reconstruct.m
index c4f1200dcd..2ee768eb6d 100644
--- a/applications/lofar2/model/pfb_bunton_annotated/reconstruct.m
+++ b/applications/lofar2/model/pfb_bunton_annotated/reconstruct.m
@@ -25,7 +25,7 @@ close all
rng('default')
ImpulseResponse = 0; % set to 1 to calculate correction filter
-Correct = 1; % set to 1 to allow correction filter to be applied
+Correct = 0; % set to 1 to allow correction filter to be applied
% cl is the prototype lowpass filter
Ncoefs = length(cl); % = 2304
@@ -112,9 +112,13 @@ diff = outData - inData(1:length(outData));
% . rng('default'); reconstruct, with Correct = 1: SNR = 62.24 dB
% Note:
% . With the impulse data input the SNR = 304.46 dB, so perfect.
-% . For other input data there is still some error, due to the limited stopband
-% attenuation of the prototype LPF (can be seen using DEVS = 0.003 instead of
-% 0.0003 in Gen_filter12).
+% . For other input data there is still some error when Correct = 1, due to
+% the limited stopband attenuation of the prototype LPF (can be seen using
+% DEVS = 0.003 instead of 0.0003 in Gen_filter12).
+% . When Correct = 0 then the error is caused largely by the passband ripple
+% DEVP = 0.02 and W0 = 1 / 15.3 of the prototype LPF, and db(0.02) = -34 dB.
+% With DEVP = 0.005 and W0 = 1 / 15.05 then db(0.005) = -46.0 dB and SNR =
+% 38.8 dB, so increased.
SNR = 10 * log10(sum(abs(inData(10000:70000) .^ 2)) / sum(abs(diff(10000:70000) .^ 2)));
sprintf('SNR = %6.2f [dB]', SNR)
--
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