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lockin: add rounding bias

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This commit is contained in:
Robert Jördens 2021-02-12 11:05:50 +01:00
parent 32b7058b47
commit 67f052c0c9
1 changed files with 5 additions and 2 deletions
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7
dsp/src/lockin.rs
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@ -16,6 +16,7 @@ impl Lockin {
} }
/// Update the lockin with a sample taken at a given phase. /// Update the lockin with a sample taken at a given phase.
/// The lowpass has a gain of `1 << k`.
pub fn update(&mut self, sample: i16, phase: i32, k: u8) -> Complex<i32> { pub fn update(&mut self, sample: i16, phase: i32, k: u8) -> Complex<i32> {
// Get the LO signal for demodulation. // Get the LO signal for demodulation.
let lo = Complex::from_angle(phase); let lo = Complex::from_angle(phase);
@ -23,8 +24,10 @@ impl Lockin {
// Mix with the LO signal, filter with the IIR lowpass, // Mix with the LO signal, filter with the IIR lowpass,
// return IQ (in-phase and quadrature) data. // return IQ (in-phase and quadrature) data.
Complex( Complex(
self.state[0].update((sample as i32 * (lo.0 >> 16)) >> 16, k), self.state[0]
self.state[1].update((sample as i32 * (lo.1 >> 16)) >> 16, k), .update((sample as i32 * (lo.0 >> 16) + (1 << 15)) >> 16, k),
self.state[1]
.update((sample as i32 * (lo.1 >> 16) + (1 << 15)) >> 16, k),
) )
} }
} }