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Fixing inverse SINC TX filter for P25

nxdn
Andy CA6JAU 2018-02-10 14:44:30 -03:00
parent b42ddbbf42
commit 8a1ac05df2
2 changed files with 6 additions and 8 deletions
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12
P25TX.cpp
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@ -30,12 +30,10 @@ static q15_t RC_0_2_FILTER[] = {-897, -1636, -1840, -1278, 0, 1613, 2936, 3310,
-3011, 0, 2315, 3310, 2936, 1613, 0, -1278, -1840, -1636, -897, 0}; // numTaps = 40, L = 5
const uint16_t RC_0_2_FILTER_PHASE_LEN = 8U; // phaseLength = numTaps/L
// Generated in MATLAB using the following commands, and then normalised for unity gain
// shape2 = 'Inverse-sinc Lowpass';
// d2 = fdesign.interpolator(1, shape2);
// h2 = design(d2, 'SystemObject', true);
static q15_t LOWPASS_FILTER[] = {1294, -2251, 4312, -8402, 20999, 20999, -8402, 4312, -2251, 1294};
const uint16_t LOWPASS_FILTER_LEN = 10U;
static q15_t LOWPASS_FILTER[] = {124, -188, -682, 1262, 556, -621, -1912, -911, 2058, 3855, 1234, -4592, -7692, -2799,
8556, 18133, 18133, 8556, -2799, -7692, -4592, 1234, 3855, 2058, -911, -1912, -621,
556, 1262, -682, -188, 124};
const uint16_t LOWPASS_FILTER_LEN = 32U;
const q15_t P25_LEVELA = 1260;
const q15_t P25_LEVELB = 420;
@ -56,7 +54,7 @@ m_poPtr(0U),
m_txDelay(240U) // 200ms
{
::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
::memset(m_lpState, 0x00U, 70U * sizeof(q15_t));
::memset(m_lpState, 0x00U, 60U * sizeof(q15_t));
m_modFilter.L = P25_RADIO_SYMBOL_LENGTH;
m_modFilter.phaseLength = RC_0_2_FILTER_PHASE_LEN;

2
P25TX.h
View File

@ -40,7 +40,7 @@ private:
arm_fir_interpolate_instance_q15 m_modFilter;
arm_fir_instance_q15 m_lpFilter;
q15_t m_modState[16U]; // blockSize + phaseLength - 1, 4 + 9 - 1 plus some spare
q15_t m_lpState[70U]; // NoTaps + BlockSize - 1, 44 + 20 - 1 plus some spare
q15_t m_lpState[60U]; // NoTaps + BlockSize - 1, 32 + 20 - 1 plus some spare
uint8_t m_poBuffer[1200U];
uint16_t m_poLen;
uint16_t m_poPtr;