Module: Radio::Filter::Iq

Defined in:
lib/radio/filters/iq.rb

Defined Under Namespace

Modules: Complex

Instance Method Summary collapse

Instance Method Details

#adjust!(data, phase, gain) ⇒ Object 



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# File 'lib/radio/filters/iq.rb', line 106

def adjust! data, phase, gain
  data.collect! do |v|
    Complex(v.real + phase * v.imag, v.imag * gain)
  end
end

#analyze ⇒ Object

Once per call, we will do an FFT to either start a new round of guessing or try again on the current set.



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# File 'lib/radio/filters/iq.rb', line 70

def analyze
  return unless @cur_fft or @next_fft
  if !@cur_fft_count or @cur_fft_count > @tries
    @cur_fft = @next_fft
    @cur_fft_count = 0
    fft = @cur_fft.dup
    adjust! fft, @phase, @gain
    @cur_fft_best = detect_energies FFTW3::fft(fft)
  else
    @cur_fft_count += 1
    phaseIncrement = @iq_rate * rand_direction
    gainIncrement = @iq_rate * rand_direction
    fft = @cur_fft.dup
    adjust! fft, @phase + phaseIncrement, @gain + gainIncrement
    det = detect_energies FFTW3::fft(fft)
    if det > @cur_fft_best
      @cur_fft_best = det
      @gain += gainIncrement
      @phase += phaseIncrement
    end
  end
end

#collect(data) ⇒ Object

This maintains a buffer of recent data that we can grab for analysis



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# File 'lib/radio/filters/iq.rb', line 50

def collect data
  i = 0
  data_size = data.size
  while i < data_size
    remaining = data_size - i
    space = @bins - @fft_pos
    actual = [remaining,space].min
    new_fft_pos = @fft_pos + actual
    @fft[@fft_pos...new_fft_pos] = data[i...i+actual]
    @fft_pos = new_fft_pos
    if @fft_pos == @bins
      @fft_pos = 0
      @next_fft = @fft.dup
    end
    i += actual
  end
end

#detect_energies(spectrum) ⇒ Object 



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# File 'lib/radio/filters/iq.rb', line 112

def detect_energies spectrum
  result = 0.0
  length = @bins.size
  halfLength = length / 2
  start = (0.20 * halfLength).round
  finish = (0.90 * halfLength).round
  spectrum = spectrum.abs
  frag = spectrum[start..finish]
  min = frag.min
  max = frag.max
  threshold = max - (max-min) * 0.5
  (start..finish).each do |i|
    cur = spectrum[length - 1 - i]
    next unless cur > threshold
    diff = cur - spectrum[i]
    next unless diff > 0
    result += diff
  end
  result
end

#rand_direction ⇒ Object

this is the IQ detection idea from the sdr# project



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# File 'lib/radio/filters/iq.rb', line 134

def rand_direction
  rand*2-1
end

#remove_dc_bias!(data) ⇒ Object 



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# File 'lib/radio/filters/iq.rb', line 94

def remove_dc_bias! data
  data.collect! do |v|
    temp = @biasI * (1 - @dc_rate) + v.real * @dc_rate
    @biasI = temp unless temp.nan?
    real = v.real - @biasQ
    temp = @biasQ * (1 - @dc_rate) + v.imag * @dc_rate
    @biasQ = temp unless temp.nan?
    imag = v.imag - @biasQ
    Complex(real,imag)
  end
end

#setup ⇒ Object 



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# File 'lib/radio/filters/iq.rb', line 21

def setup
  @bins = 512
  @tries = 5
  @dc_rate = 0.00001
  @iq_rate = 0.0001
  @biasI = 0.0
  @biasQ = 0.0
  @gain = 1.0
  @phase = 0.0
  @fft = NArray.scomplex @bins
  @fft_pos = 0
end