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[fix](trx-backend-soapysdr): measure carrier power from mixed-signal DC for signal strength

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Use the DC component of the baseband-mixed IQ (before LPF/decimation) as a narrow-band carrier power estimate. This correlates with the spectrum FFT peak instead of measuring wideband channel power which inflates the reading for WFM.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>
This commit is contained in:
Stan Grams
2026-03-27 15:00:17 +01:00
parent 7ffd1ccd6a
commit 5220e606c1
1 changed files with 15 additions and 7 deletions
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src/trx-server/trx-backend/trx-backend-soapysdr/src/dsp/channel.rs
+15 -7
View File
@@ -673,6 +673,16 @@ impl ChannelDsp {
}
self.mixer_phase = (phase_start + n as f64 * phase_inc).rem_euclid(std::f64::consts::TAU);
// Carrier power: DC component of the mixed signal (narrow-band estimate
// at the tuned frequency). Correlates with the spectrum FFT peak.
{
let inv_n = 1.0 / n as f32;
let dc_i: f32 = mixed_i.iter().sum::<f32>() * inv_n;
let dc_q: f32 = mixed_q.iter().sum::<f32>() * inv_n;
let carrier_power = dc_i * dc_i + dc_q * dc_q;
self.last_signal_db = 10.0 * carrier_power.max(1e-12).log10();
}
self.lpf_iq.filter_block_into(
mixed_i,
mixed_q,
@@ -740,14 +750,12 @@ impl ChannelDsp {
}
}
let (signal_power_mean, signal_power_peak) =
decimated.iter().fold((0.0_f32, 0.0_f32), |(sum, peak), s| {
let p = s.re * s.re + s.im * s.im;
(sum + p, peak.max(p))
});
let signal_power = signal_power_mean / decimated.len() as f32;
let signal_power = decimated
.iter()
.map(|s| s.re * s.re + s.im * s.im)
.sum::<f32>()
/ decimated.len() as f32;
let signal_db = 10.0 * signal_power.max(1e-12).log10();
self.last_signal_db = 10.0 * signal_power_peak.max(1e-12).log10();
const WFM_OUTPUT_GAIN: f32 = 0.50;
let mut audio = if let Some(decoder) = self.wfm_decoder.as_mut() {
let mut out = decoder.process_iq(decimated);