Documentation
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Index ¶
- func PPMToHz(ppm int, centerHz uint32) int64
- type DCBlocker
- type IQBalancer
- type IQImbalanceCorrector
- type IQImbalanceStats
- func (s *IQImbalanceStats) Balancer() IQBalancer
- func (s *IQImbalanceStats) Count() uint64
- func (s *IQImbalanceStats) GainImbalanceDB() float64
- func (s *IQImbalanceStats) ImageRejectionDB() float64
- func (s *IQImbalanceStats) Observe(in []complex64)
- func (s *IQImbalanceStats) PhaseImbalanceDeg() float64
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type DCBlocker ¶
type DCBlocker struct {
// contains filtered or unexported fields
}
DCBlocker subtracts a slowly-tracked DC bias from a complex sample stream. Useful because RTL-SDR dongles park noticeable DC at the tuned center bin.
func NewDCBlocker ¶
type IQBalancer ¶
type IQBalancer struct {
GainQ float32 // amplitude scale for Q
Phase float32 // radians, applied to Q via Q' = Q*cos - I*sin
}
IQBalancer applies a single-coefficient IQ-imbalance correction (gain + phase) measured against a calibration tone. Coefficients are 1.0 and 0.0 by default (passthrough).
func (IQBalancer) Process ¶
func (b IQBalancer) Process(in []complex64)
type IQImbalanceCorrector ¶ added in v0.2.7
type IQImbalanceCorrector struct {
// contains filtered or unexported fields
}
IQImbalanceCorrector blindly estimates and removes the front-end I/Q imbalance from a streaming complex signal. It tracks the second-order moments of the *raw* input with a slow EMA, derives the correcting IQBalancer once a warmup has elapsed, and applies it in-place. Because the moments are always measured from the raw input (never the corrected output) there is no feedback loop, and a static hardware imbalance converges and stays. Off the hot path by default — opt-in (issue #402). Not safe for concurrent use.
func NewIQImbalanceCorrector ¶ added in v0.2.7
func NewIQImbalanceCorrector() *IQImbalanceCorrector
NewIQImbalanceCorrector returns a corrector with a slow moment EMA (~100k samples, ≈40 ms at 2.4 MSPS) and a short warmup before it starts correcting.
func (*IQImbalanceCorrector) Coefficients ¶ added in v0.2.7
func (c *IQImbalanceCorrector) Coefficients() (gainQ, phaseRad float32)
Coefficients returns the corrector's current GainQ and Phase (radians) — for surfacing the converged estimate in diagnostics.
func (*IQImbalanceCorrector) Process ¶ added in v0.2.7
func (c *IQImbalanceCorrector) Process(in []complex64)
Process updates the imbalance estimate from the raw input, then corrects the chunk in-place. During warmup it is a passthrough (GainQ=1, Phase=0).
type IQImbalanceStats ¶ added in v0.2.7
type IQImbalanceStats struct {
// contains filtered or unexported fields
}
IQImbalanceStats accumulates the second-order moments of a complex stream — E[I²], E[Q²], E[I·Q] — and derives the front-end I/Q gain/phase imbalance from them. For a constant-envelope signal (FM / C4FM) the ideal baseband is circularly symmetric (E[I²] = E[Q²], E[I·Q] = 0), so any departure measures the receiver's I/Q imbalance directly. Used both as a replay diagnostic and as the estimator behind IQImbalanceCorrector (issue #402: an uncorrected RTL-SDR imbalance, worst at the on-channel DC the DDC sits on, is the leading explanation for the asymmetric demodulated eye).
func (*IQImbalanceStats) Balancer ¶ added in v0.2.7
func (s *IQImbalanceStats) Balancer() IQBalancer
Balancer returns the IQBalancer coefficients that correct the measured imbalance: GainQ equalizes the I/Q powers and Phase de-correlates I and Q (Q' = GainQ·Q·cosΦ − I·sinΦ ⇒ E[I·Q']=0, E[Q'²]=E[I²]). Identity when insufficient/degenerate data has been seen.
func (*IQImbalanceStats) Count ¶ added in v0.2.7
func (s *IQImbalanceStats) Count() uint64
Count returns the number of samples observed so far.
func (*IQImbalanceStats) GainImbalanceDB ¶ added in v0.2.7
func (s *IQImbalanceStats) GainImbalanceDB() float64
GainImbalanceDB is 10·log10(E[I²]/E[Q²]): the I-vs-Q power imbalance in dB (0 = balanced). Equivalently 20·log10(GainQ).
func (*IQImbalanceStats) ImageRejectionDB ¶ added in v0.2.7
func (s *IQImbalanceStats) ImageRejectionDB() float64
ImageRejectionDB approximates the front-end image-rejection ratio implied by the measured imbalance (higher is better; a clean front-end is ≳ 40 dB). The small-imbalance approximation image/signal ≈ (εgain² + φ²)/4.
func (*IQImbalanceStats) Observe ¶ added in v0.2.7
func (s *IQImbalanceStats) Observe(in []complex64)
Observe folds a chunk of raw IQ into the running moments.
func (*IQImbalanceStats) PhaseImbalanceDeg ¶ added in v0.2.7
func (s *IQImbalanceStats) PhaseImbalanceDeg() float64
PhaseImbalanceDeg is the I/Q quadrature error in degrees, from the normalized I·Q correlation (0 = perfect quadrature).
Source Files
Directories
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| Path | Synopsis |
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Package purego is the pure-Go RTL-SDR driver — the sdr.Device / sdr.Driver implementation that composes the platform USB transport (internal/sdr/rtlsdr/usb), the RTL2832U register layer (internal/sdr/rtlsdr/rtl2832u), and the per-chip tuner drivers (internal/sdr/rtlsdr/tuners).
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Package purego is the pure-Go RTL-SDR driver — the sdr.Device / sdr.Driver implementation that composes the platform USB transport (internal/sdr/rtlsdr/usb), the RTL2832U register layer (internal/sdr/rtlsdr/rtl2832u), and the per-chip tuner drivers (internal/sdr/rtlsdr/tuners). |
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Package rtl2832u is the pure-Go register / I2C-bridge layer that sits between the platform USB transport (internal/sdr/rtlsdr/usb) and the per-tuner drivers.
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Package rtl2832u is the pure-Go register / I2C-bridge layer that sits between the platform USB transport (internal/sdr/rtlsdr/usb) and the per-tuner drivers. |
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Package tuners houses the per-chip tuner drivers that sit between the RTL2832U register layer (internal/sdr/rtlsdr/rtl2832u) and the top-level [sdr.Device].
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Package tuners houses the per-chip tuner drivers that sit between the RTL2832U register layer (internal/sdr/rtlsdr/rtl2832u) and the top-level [sdr.Device]. |
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Package usb is the platform-abstraction layer that the pure-Go RTL-SDR driver speaks to.
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Package usb is the platform-abstraction layer that the pure-Go RTL-SDR driver speaks to. |