Ryan Malloy
cd3a8cc6be
- sco_mod: 9-channel FM subcarrier oscillator modulator (inverse of sco_demod), with round-trip tests proving voltage recovery across all channels - fm_voice_subcarrier_mod: add audio_input parameter to accept external float streams (e.g., Apollo mission voice recordings) instead of internal test tone - loopback_demo.py: streaming TX->RX round-trip with CLI for noise/voice/frames - agc_loopback_demo.py: full Virtual AGC integration via TCP bridge
116 lines
3.8 KiB
Python
116 lines
3.8 KiB
Python
"""
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Apollo FM Voice Subcarrier Modulator -- 1.25 MHz FM with internal tone or external audio.
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Transmit-side counterpart to voice_subcarrier_demod. FM-modulates audio onto a
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1.25 MHz subcarrier and outputs the real-valued subcarrier signal.
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Two modes of operation:
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- Internal test tone (default): generates a sine wave for testing.
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- External audio input: accepts a float stream (e.g., Apollo mission voice
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recordings) and modulates it onto the subcarrier.
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On the real spacecraft, voice audio (300-3000 Hz) drives an FM VCO at 113 kHz,
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which is mixed with the 512 kHz master clock and doubled to produce the
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1.25 MHz FM subcarrier with +/-29 kHz deviation.
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Reference: IMPLEMENTATION_SPEC.md section 4.2
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"""
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import math
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from gnuradio import analog, blocks, gr
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from apollo.constants import (
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SAMPLE_RATE_BASEBAND,
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VOICE_FM_DEVIATION_HZ,
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VOICE_SUBCARRIER_HZ,
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)
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class fm_voice_subcarrier_mod(gr.hier_block2):
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"""FM-modulated voice subcarrier (1.25 MHz) with internal test tone or external audio.
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Outputs:
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float -- real-valued FM subcarrier at subcarrier_freq
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Inputs (when audio_input=True):
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float -- external audio signal (e.g., mission voice recordings)
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When audio_input=False (default), an internal sine test tone is used.
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When audio_input=True, the block accepts an external float stream -- for
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example, actual Apollo mission crew voice recordings.
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"""
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def __init__(
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self,
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sample_rate: float = SAMPLE_RATE_BASEBAND,
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subcarrier_freq: float = VOICE_SUBCARRIER_HZ,
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fm_deviation: float = VOICE_FM_DEVIATION_HZ,
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tone_freq: float = 1000.0,
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audio_input: bool = False,
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):
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# Choose input signature based on mode
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in_sig = gr.io_signature(1, 1, gr.sizeof_float) if audio_input else gr.io_signature(0, 0, 0)
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gr.hier_block2.__init__(
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self,
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"apollo_fm_voice_subcarrier_mod",
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in_sig,
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gr.io_signature(1, 1, gr.sizeof_float),
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)
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self._sample_rate = sample_rate
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self._tone_freq = tone_freq
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self._subcarrier_freq = subcarrier_freq
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self._fm_deviation = fm_deviation
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self._audio_input = audio_input
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# FM modulator: sensitivity = 2*pi*deviation/sample_rate rad/sample
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# With unit-amplitude sine input this gives +/-fm_deviation Hz.
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fm_sensitivity = 2.0 * math.pi * fm_deviation / sample_rate
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self.fm_mod = analog.frequency_modulator_fc(fm_sensitivity)
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# LO at subcarrier frequency for upconversion
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self.lo = analog.sig_source_c(
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sample_rate, analog.GR_COS_WAVE, subcarrier_freq, 1.0, 0,
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)
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# Mixer: FM baseband x LO -> subcarrier
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self.mixer = blocks.multiply_cc(1)
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# Extract real part for float output
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self.to_real = blocks.complex_to_real(1)
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if audio_input:
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# External audio input -> FM mod
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self.connect(self, self.fm_mod, (self.mixer, 0))
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else:
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# Internal test tone -> FM mod
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self.tone = analog.sig_source_f(
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sample_rate, analog.GR_SIN_WAVE, tone_freq, 1.0, 0,
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)
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self.connect(self.tone, self.fm_mod, (self.mixer, 0))
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self.connect(self.lo, (self.mixer, 1))
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self.connect(self.mixer, self.to_real, self)
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@property
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def tone_freq(self) -> float:
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"""Test tone frequency in Hz."""
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return self._tone_freq
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@property
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def subcarrier_freq(self) -> float:
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"""Subcarrier center frequency in Hz."""
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return self._subcarrier_freq
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@property
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def fm_deviation(self) -> float:
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"""FM deviation in Hz."""
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return self._fm_deviation
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@property
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def audio_input(self) -> bool:
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"""Whether the block accepts external audio input."""
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return self._audio_input
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