# Configuration

`ReceiverConfig` owns RF, acquisition, tracking, front-end, and fixed-point
dataclasses. YAML loading is strict: a misspelled field is an error.

Important validation rules include positive sampling/loop rates, a real IF
strictly below Nyquist, integer sample counts per integration interval,
ordered correlator tap spacing, explicit FFT length when requested, E1B
bit-transition protection beyond 4 ms, and E1C secondary-code handling beyond
4 ms. E1B tracking is conservatively limited to 4 ms until navigation-symbol
synchronization is implemented.

`intermediate_frequency_hz` may be nonzero for either real or analytic input.
The front end always outputs complex baseband and divides the effective sample
rate by the integer decimation factor. Acquisition/tracking must use that output
rate.

Acquisition parallelism fields expose future hardware/software scheduling but
do not change numerical results. `zero_padding_mode: none` provides the exact
N-sample circular correlation. A longer FFT changes the sampled numerical
correlation/edge convention; it is not additional physical delay information.

Default YAML files:

- `e1_default.yaml`: requested 16.368 MHz nominal defaults.
- `acquisition_example.yaml`: faster 4.092 MHz executable search.
- `tracking_example.yaml`: 4.092 MHz tracking defaults.
- `e1_cboc.yaml`: explicit full-band CBOC selection at 32.736 Msps and a
  2.25 MHz analytic low IF.
- `navigation_collection.yaml`: SignalSim IQ-to-I/NAV regression. Its default
  `tracking.architecture` is `e1c_pilot_aided_e1b`; the CLI can select
  `e1b_only` for an A/B replay.

`AcquisitionConfig.modulation` and `TrackingConfig.modulation` independently
select `BOC11` or `CBOC`. Both default to `BOC11`, so existing SignalSim and
low-bandwidth configurations retain their measured behavior. A CBOC vector
must set both fields to `CBOC` for a matched acquisition/tracking replica.

The BOC lock detector parameters are part of `TrackingConfig`. The defaults use
25 noncoherent power epochs, three confirmations, and the configured
`loss_of_lock_epochs` for sustained failure. Carrier and BOC central/outer
shape thresholds have explicit entry and exit values. `lock_signal_loss_power_ratio`
sets the five-tap power loss test. These parameters affect monitoring and
reacquisition only; they do not change discriminator or loop-filter coefficients.
`boc_side_peak_coherence_enter/exit` calibrate the coherent E/L-to-P tap-sign
test needed to distinguish the negative half-chip BOC sidelobe from the main
peak using more than magnitude-only information.