Ryan Malloy
0ee7ff0ad7
Complete signal processing pipeline from complex baseband to decoded PCM telemetry, verified against the 1965 NAA Study Guide (A-624): Core demod (Phase 1): - PM demodulator with carrier PLL recovery - 1.024 MHz subcarrier extractor (bandpass + downconvert) - BPSK demodulator with Costas loop + symbol sync - Convenience hier_block2 combining subcarrier + BPSK PCM frame processing (Phase 2): - 32-bit frame sync with Hamming distance correlator - SEARCH/VERIFY/LOCKED state machine, complement-on-odd handling - Frame demultiplexer (128-word, A/D voltage scaling) - AGC downlink decoder (15-bit word reassembly from DNTM1/DNTM2) Voice and analog (Phase 3): - 1.25 MHz FM voice subcarrier demod to 8 kHz audio - SCO demodulator for 9 analog sensor channels (14.5-165 kHz) Virtual AGC integration (Phase 4): - TCP bridge client with auto-reconnect and channel filtering - DSKY uplink encoder (VERB/NOUN/DATA command sequences) Top-level receiver (Phase 5): - usb_downlink_receiver hier_block2: one block, complex in, PDUs out - 14 GRC block YAML definitions for GNU Radio Companion - Example scripts for signal analysis and full-chain demo Infrastructure: - constants.py with all timing/frequency/frame parameters - protocol.py for sync word + AGC packet encode/decode - Synthetic USB signal generator for testing - 222 tests passing, ruff lint clean
65 lines
2.0 KiB
Python
65 lines
2.0 KiB
Python
"""
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Apollo BPSK Subcarrier Demodulator — convenience wrapper.
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Hierarchical block combining subcarrier_extract + bpsk_demod into a single
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block for the common case of extracting and demodulating the 1.024 MHz PCM
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subcarrier from the PM demodulator output.
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This resolves the naming used in __init__.py and provides a simple
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"float in, bytes out" interface.
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Reference: IMPLEMENTATION_SPEC.md section 4.2
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"""
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from gnuradio import gr
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from apollo.bpsk_demod import bpsk_demod
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from apollo.constants import PCM_BPF_BW_HZ, PCM_HIGH_BIT_RATE, PCM_SUBCARRIER_HZ
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from apollo.subcarrier_extract import subcarrier_extract
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class bpsk_subcarrier_demod(gr.hier_block2):
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"""Combined subcarrier extraction + BPSK demodulation.
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Inputs:
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float — PM demodulator output (composite subcarrier signal)
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Outputs:
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byte — recovered NRZ bits (0 or 1)
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"""
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def __init__(
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self,
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subcarrier_freq: float = PCM_SUBCARRIER_HZ,
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bandwidth: float = PCM_BPF_BW_HZ,
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bit_rate: float = PCM_HIGH_BIT_RATE,
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sample_rate: float = 5_120_000,
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decimation: int = 1,
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loop_bw: float = 0.045,
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):
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gr.hier_block2.__init__(
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self,
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"apollo_bpsk_subcarrier_demod",
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gr.io_signature(1, 1, gr.sizeof_float),
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gr.io_signature(1, 1, gr.sizeof_char),
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)
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# Subcarrier extraction: bandpass + translate to baseband
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self.extract = subcarrier_extract(
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center_freq=subcarrier_freq,
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bandwidth=bandwidth,
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sample_rate=sample_rate,
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decimation=decimation,
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)
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# BPSK demodulation: carrier recovery + symbol sync + slicer
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output_rate = sample_rate / decimation
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self.demod = bpsk_demod(
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symbol_rate=bit_rate,
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sample_rate=output_rate,
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loop_bw=loop_bw,
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)
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# Connect: float input → extract → demod → byte output
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self.connect(self, self.extract, self.demod, self)
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