Scientific validation: SciPy LFM chirp radar

Claim

ChirpRadarEmitter generates deterministic, single-emitter complex-baseband LFM pulses suitable for the chirp-radar Golden Path template. At seed 1337, the path emits 24 records and validates sample count, declared bandwidth, pulse gating, sweep direction, instantaneous-frequency slope, metadata, and provenance.

This is a waveform claim. It is not a target-return, scattering, range-Doppler, multi-pulse, coherent-processing, or empirical radar-system claim.

Contract evidence

Criterion

Evidence

IQ layout

Every record is a (2, N) float32 tensor, with N = round(sample_rate * duration_s).

LFM law

The phase derivative follows -B/2 + (B/tau)t for up-chirp and its negative-slope counterpart for down-chirp.

Direction

Up/down records have the expected opposing instantaneous-frequency slopes.

Gate

Samples from round(sample_rate * pulse_duration_s) onward are exactly zero.

Bandwidth

Config validation rejects non-finite values and Nyquist-violating bandwidth; measured content remains within the declared waveform contract.

Metadata/provenance

Class, units, seed derivation, parameter values, and content/provenance identifiers are stored with each record.

Determinism

A repeat run in the same qualified environment reproduces the stated waveform contract.

The executable tests live under tests/validation/emitters/chirp_radar/; the golden-path harness additionally writes local HDF5, runs rfgen inspect, and reads all records through the published snapshot.

Limitations

  • The waveform has a rectangular pulse envelope; no application-specific tapering is claimed.

  • It has no target, antenna, propagation, receiver, range, Doppler, or scattering model.

  • It produces one pulse, not a pulse train or coherent processing interval.

  • f_offset_hz is recorded metadata for a later mixing stage; it does not alter the generated baseband IQ.

These limitations do not contradict the stated waveform claim and therefore do not create new implementation requirements.

References

  • M. A. Richards, Fundamentals of Radar Signal Processing, 2nd ed., ch. 4: LFM phase, chirp rate, and pulse compression.

  • SciPy scipy.signal.chirp: waveform synthesis primitive used by the emitter.