Class: PWN::SDR::Decoder::GPS::DemodIQ

Inherits:
Object
  • Object
show all
Defined in:
lib/pwn/sdr/decoder/gps.rb

Overview

Streaming L1 C/A acquisition demod for Base.run_iq.

Instance Method Summary collapse

Constructor Details

#initialize(rate:) ⇒ DemodIQ

Returns a new instance of DemodIQ.



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# File 'lib/pwn/sdr/decoder/gps.rb', line 23

def initialize(rate:)
  @rate  = rate.to_f
  @buf   = []
  @seen  = {}
  @codes = {}
end

Instance Method Details

#feed_iq(samples, rate: nil) ⇒ Object 



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# File 'lib/pwn/sdr/decoder/gps.rb', line 30

def feed_iq(samples, rate: nil)
  @rate = rate.to_f if rate
  @buf.concat(samples)
  need = (@rate / 1000.0 * 2).ceil * 2 # 1 ms complex + headroom
  return if @buf.length < need * 2

  ms = PWN::SDR::Decoder::DSP.resample_iq(
    iq: @buf.shift(need * 2), src_rate: @rate, dst_rate: ACQ_RATE
  )[0, 2046 * 2]
  return if ms.nil? || ms.length < 2046 * 2

  hits = acquire(ms)
  hits.each do |h|
    key = "PRN#{h[:prn]}"
    next if @seen[key] && (@seen[key] - h[:cn0_db_hz]).abs < 1.5

    @seen[key] = h[:cn0_db_hz]
    yield h
  end
end