Ryan Malloy
86a5b08e9d
Implements the Apollo composite PRN ranging code (5,456,682 chips) from five component sequences (CL, X, A, B, C) combined via majority-vote logic, matching Ken Shirriff's Teensy rangeGenerator.ino bit-for-bit. LFSR taps corrected to produce maximal-length sequences: A: 5-bit, taps [2,0] (x^5+x^2+1, period 31) B: 6-bit, taps [1,0] (x^6+x+1, period 63) C: 7-bit, taps [1,0] (x^7+x+1, period 127) New files: src/apollo/ranging.py -- pure-Python code generator and correlator src/apollo/ranging_source.py -- GR sync_block streaming PRN chips src/apollo/ranging_mod.py -- GR hier_block2 NRZ chip modulator src/apollo/ranging_demod.py -- GR basic_block FFT-based range correlator grc/apollo_ranging_*.block.yml -- GRC block definitions (3 files) examples/ranging_demo.py -- standalone demo with delay simulation
65 lines
1.6 KiB
YAML
65 lines
1.6 KiB
YAML
id: apollo_ranging_demod
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label: Apollo Ranging Demodulator
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category: '[Apollo USB]'
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flags: [python]
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parameters:
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- id: chip_rate
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label: Chip Rate (Hz)
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dtype: int
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default: '993963'
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- id: sample_rate
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label: Sample Rate (Hz)
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dtype: real
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default: '5120000'
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- id: correlation_length
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label: Correlation Length (samples)
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dtype: int
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default: '100000'
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- id: two_way
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label: Two-Way Ranging
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dtype: bool
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default: 'True'
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options: ['True', 'False']
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option_labels: ['Two-way (ground-SC-ground)', 'One-way']
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inputs:
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- label: in
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domain: stream
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dtype: float
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outputs:
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- label: range
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domain: message
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templates:
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imports: from apollo.ranging_demod import ranging_demod
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make: >-
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apollo.ranging_demod.ranging_demod(
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chip_rate=${chip_rate},
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sample_rate=${sample_rate},
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correlation_length=${correlation_length},
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two_way=${two_way})
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documentation: |-
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Apollo Ranging Demodulator
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Correlates received signal against known PRN ranging code to measure
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spacecraft range. Accumulates samples in batches, performs FFT-based
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cross-correlation, and emits range measurement PDUs.
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Message output (range):
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delay_chips: Measured delay in chip periods
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range_m: Computed range in meters
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correlation_peak: Peak correlation value
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peak_to_avg_ratio: Peak-to-average ratio (signal quality)
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timestamp: Measurement timestamp
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Parameters:
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chip_rate: Expected PRN chip rate (default 993,963 Hz)
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sample_rate: Input sample rate (default 5.12 MHz)
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correlation_length: Samples per correlation batch (default 100,000)
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two_way: If True, divide range by 2 for round-trip measurement
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file_format: 1
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