From 8901c8e985d5bc9ea418de07505e1f667623b4a2 Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Tue, 23 Mar 2021 17:38:48 +0100
Subject: [PATCH] Clarified WG valid amplitude clipping range in relation to
c_diag_wg_gain_w.
---
libraries/base/diag/src/vhdl/diag_pkg.vhd | 3 +++
1 file changed, 3 insertions(+)
diff --git a/libraries/base/diag/src/vhdl/diag_pkg.vhd b/libraries/base/diag/src/vhdl/diag_pkg.vhd
index 3fcfd25e7a..7e86c09706 100644
--- a/libraries/base/diag/src/vhdl/diag_pkg.vhd
+++ b/libraries/base/diag/src/vhdl/diag_pkg.vhd
@@ -81,6 +81,9 @@ PACKAGE diag_pkg IS
CONSTANT c_diag_wg_gain_w : NATURAL := 1; -- Normalized range [0 1> maps to fixed point range [0:2**c_diag_wg_ampl_w>
-- . use gain 2**0 = 1 to have fulle scale without clipping
-- . use gain 2**g_calc_gain_w > 1 to cause clipping
+ -- For c_diag_wg_gain_w = 1 there is clipping from [1 2> For normalized values >= 2**c_diag_wg_gain_w = 2
+ -- the behaviour becomes more or less undefined. Due to wrapping it appears that normalized values [2 3>
+ -- result in a sinus again. Therefore use normalized range [0 2**c_diag_wg_gain_w>.
CONSTANT c_diag_wg_ampl_unit : REAL := 2**REAL(c_diag_wg_ampl_w-c_diag_wg_gain_w)*c_diag_wg_ampl_norm; -- ^= Full Scale range [-c_wg_full_scale +c_wg_full_scale] without clipping
CONSTANT c_diag_wg_freq_unit : REAL := 2**REAL(c_diag_wg_freq_w); -- ^= c_clk_freq = Fs (sample frequency), assuming one sinus waveform in the buffer
CONSTANT c_diag_wg_phase_unit : REAL := 2**REAL(c_diag_wg_phase_w)/ 360.0; -- ^= 1 degree
--
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