From cc785e32256e22b38ded25907e514c9279c8739b Mon Sep 17 00:00:00 2001 From: Jonathan Naylor Date: Thu, 30 Apr 2020 11:23:19 +0100 Subject: [PATCH] =?UTF-8?q?Revert=20"Change=20emphasis=20time=20constant?= =?UTF-8?q?=20to=20750=C2=B5S"?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- FM.cpp | 4 ++-- Tools/emphasis.txt | 21 +++++++++------------ 2 files changed, 11 insertions(+), 14 deletions(-) diff --git a/FM.cpp b/FM.cpp index 6c1043c..f6da336 100644 --- a/FM.cpp +++ b/FM.cpp @@ -39,8 +39,8 @@ m_hangTimer(), m_filterStage1( 724, 1448, 724, 32768, -37895, 21352),//3rd order Cheby Filter 300 to 2700Hz, 0.2dB passband ripple, sampling rate 24kHz m_filterStage2(32768, 0,-32768, 32768, -50339, 19052), m_filterStage3(32768, -65536, 32768, 32768, -64075, 31460), -m_preemphasis(32768, 1771, 0, 32768, -30997, 0),//750µS 24kHz sampling rate -m_deemphasis (32768, -30997, 0, 32768, 1771, 0),//750µS 24kHz sampling rate +m_preemphasis(32768, 13967, 0, 32768, -18801, 0),//75µS 24kHz sampling rate +m_deemphasis (32768, -18801, 0, 32768, 13967, 0),//75µS 24kHz sampling rate m_blanking(), m_useCOS(true), m_rfAudioBoost(1U), diff --git a/Tools/emphasis.txt b/Tools/emphasis.txt index 0c929ef..39660d1 100644 --- a/Tools/emphasis.txt +++ b/Tools/emphasis.txt @@ -9,24 +9,21 @@ clear all; clc; fs = 24000; -timeConstant = 0.00075; %750µS - - samplingtime = 1/fs; % analog prototype A2 = [1]; -B2 = [timeConstant 1]; +B2 = [0.000075 1]; % Pre -%Ds = tf(B2, A2); +Ds = tf(B2, A2); % De -Ds = tf(A2, B2); +% Ds = tf(A2, B2); Ds = Ds/dcgain(Ds); % MZT -T1 = timeConstant; +T1 = 0.000075; % 75us z1 = -exp(-1.0/(fs*T1)); p1 = 1+z1; @@ -40,12 +37,12 @@ b2 = 0; % swap between a1, b1 to select pre- or de-emphasis -% Pre -%Bmzt = [b0 a1 b2] -%Amzt = [a0 b1 a2] +# Pre +Bmzt = [b0 a1 b2] +Amzt = [a0 b1 a2] % De -Bmzt = [b0 b1 b2] -Amzt = [a0 a1 a2] +% Bmzt = [b0 b1 b2] +% Amzt = [a0 a1 a2] DzMZT = tf(Amzt, Bmzt, samplingtime); DzMZT = DzMZT/dcgain(DzMZT);