受信機の周波数オフセット キャリブレーション

% Request user input from command-line for application parameters
userInput = helperFrequencyCalibrationUserInput;

% Calculate system parameters based on the user input
[fcParam,sigSrc] = helperFrequencyCalibrationConfig(userInput);

% Create a DC blocker system object to remove the DC component of the
% received signal and increase accuracy of the frequency offset estimation.
dcBlocker = dsp.DCBlocker('Algorithm', 'Subtract mean');

% Create a coarse frequency offset estimation System Object to calculate
% the offset. The system object performs an FFT on its input signal and
% finds the frequency of maximum power. This quantity is the frequency
% offset.
CFO = comm.CoarseFrequencyCompensator( ...
    'FrequencyResolution',  25, ...
    'SampleRate',           fcParam.FrontEndSampleRate);

% Create a spectrum analyzer scope to visualize the signal spectrum
scope = spectrumAnalyzer(...
    'Name',             'Actual Frequency Offset',...
    'Title',            'Actual Frequency Offset', ...
    'SpectrumType',     'Power',...
    'FrequencySpan',    'Full', ...
    'SampleRate',       fcParam.FrontEndSampleRate, ...
    'YLimits',          [-40,10],...
    'SpectralAverages', 50, ...
    'FrequencySpan',    'Start and stop frequencies', ...
    'StartFrequency',   -200e3, ...
    'StopFrequency',    200e3,...
    'Position',         figposition([50 30 30 40]));

msgLength = 0;
radioTime = 0;
secondCounter = 1;
while radioTime < userInput.Duration
  rxSig = sigSrc();
  rxSig = dcBlocker(rxSig);
  [~, offset] = CFO(rxSig);
  freqCorrection = (-offset / fcParam.ExpectedFrequency) * fcParam.FrontEndSampleRate;

  % Visualize spectrum and print results
  scope(rxSig);
  if radioTime > secondCounter
    fprintf(repmat('\b', 1, msgLength));
    msg = sprintf(['Frequency offset = %f Hz,\n' ...
      'Frequency correction value (Hz) = %f \n' ...
      'Frequency correction value (PPM) = %f \n'], ...
      offset, -offset, freqCorrection);
    fprintf(msg);
    msgLength = numel(msg);
    secondCounter = secondCounter + 1;
  end

  % Update radio time
  radioTime = radioTime + fcParam.FrameDuration;
end

% Release all System objects
release(sigSrc);
release(dcBlocker);
release(CFO);