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Measure signal power / noise power (at least in 2.4MHz mode).

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Switch signalLevel back to a power measurement, don't put SNR in there.
But make it a 0.0 - 1.0 double so we're not scaling everywhere.

Adjust for the amplitude offset when calculating power.

Adapt everything else to the new scheme.
This commit is contained in:
Oliver Jowett 2015-01-22 01:01:39 +00:00
parent 5beecb9f4f
commit 19082d92ea
9 changed files with 118 additions and 28 deletions
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10
mode_ac.c
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@ -144,7 +144,6 @@ int detectModeA(uint16_t *m, struct modesMessage *mm)
int F1_sig, F1_noise;
int F2_sig, F2_noise;
int fSig, fNoise, fLevel, fLoLo;
int snr;
// m[0] contains the energy from 0 -> 499 nS
// m[1] contains the energy from 500 -> 999 nS
@ -307,14 +306,7 @@ int detectModeA(uint16_t *m, struct modesMessage *mm)
if ((ModeABits < 3) || (ModeABits & 0xFFFF8808) || (ModeAErrs) )
{return (ModeABits = 0);}
// snr = 5 * 20log10(fSig / (fSig+fNoise)) (in units of 0.2dB)
// = 100log10(fSig) - 100log10(fSig+fNoise)
while (fSig > 65535 || (fSig + fNoise) > 65535) {
fSig >>= 1;
fNoise >>= 1;
}
snr = Modes.log10lut[fSig] - Modes.log10lut[fSig + fNoise];
mm->signalLevel = ((snr < 255) ? (uint8_t)snr : 255);
mm->signalLevel = 1.0 * TRUE_AMPLITUDE(fSig + fNoise) * TRUE_AMPLITUDE(fSig + fNoise) / MAX_POWER;
return ModeABits;
}