Bluetooth LE Output Power and In-Band Emissions Tests

% Select PHY transmission mode {'LE1M','LE2M'} according to the Bluetooth RF-PHY Test
% Specifications
phyMode = "LE1M";

% Select packet type {'Disabled','ConnectionCTE'} for transmitting the
% packet with or without CTE. The CTE information field position is same
% for LE test packet and data packet. For CTE-based RF-PHY tests, set the
% packet type to 'ConnectionCTE'.
packetType = "Disabled";

% Select frequency of operation for IUT based on the generic access profile
% (GAP) role(s) as shown in the table below.
%  --------------------------------------------------------------------------------
% | Operating |  Peripheral & Central Devices    |  Broadcaster & Observer Devices |
% | Frequency |                                  |                                 |
% | (MHz)     |----------------------------------|---------------------------------|
% |           | Output Power | In-band Emissions | Output Power | In-band Emissions|
% |           |     Test     |        Test       |     Test     |        Test      |    
% |-----------|--------------|-------------------|--------------|------------------|
% | Lowest    |    2402      |       2406        |     2402     |       2402       |
% | Middle    |    2440      |       2440        |     2426     |       2440       |
% | Highest   |    2480      |       2476        |     2480     |       2480       |
%  --------------------------------------------------------------------------------
Fc = 2440e6; % Frequency of operation in Hz
payloadLength = 37; % Payload length in bytes, must be in the range [37,255]
sps = 32; % Number of samples per symbol, minimum of 32 sps as per the test specifications
outputPower = 20; % Output power in dBm, must be in the range [-20,20]
pulseLength = 2;       % Length of the frequency pulse shape in the range [1,4]
modulationIndex =0.5;  % Modulation index of GFSK in the range [0.45,0.55]

numDominantFreq = 6;

testConfig = bluetoothTestWaveformConfig;
testConfig.PayloadType = 0; % Payload type for PRBS9 sequence
testConfig.PayloadLength = payloadLength;
testConfig.SamplesPerSymbol = sps;
testConfig.Mode = phyMode;
testConfig.PacketType = packetType;
testConfig.PulseLength = pulseLength;
testConfig.ModulationIndex = modulationIndex;
% testConfig.PulseLength = 2;
if strcmp(packetType,'ConnectionCTE')
    % Length of CTE in 8 microseconds units
    testConfig.CTELength = 2; % Must be in the range [2, 20]
    % Type of CTE
    testConfig.CTEType = [0;0]; % [0;0] for Angle of Arrival CTE
end
waveform = bluetoothTestWaveform(testConfig);

% Calculate sampling rate in Hz based on PHY transmission mode
Rsym = 1e6;
if strcmp(phyMode,'LE2M')
    Rsym = 2e6;
end
Fs = Rsym*sps;

% Apply frequency upconversion to obtain a passband signal for the
% specified frequency of operation.
maxFreq = 2485e6; % in Hz
interpFactor = ceil(2*maxFreq/Fs); % Interpolation factor for upconversion to
                                   % cover Bluetooth LE RF frequency band (2400e6 to 2485e6)

% Change the stopband frequency in Hz based on the PHY transmission mode
stopbandFreq = 2e6;
if strcmp(phyMode,'LE2M')
    stopbandFreq = 4e6;
end

% Create a digital upconverter System object
upConv = dsp.DigitalUpConverter(...
              'InterpolationFactor', interpFactor,...
              'SampleRate', Fs,...
              'Bandwidth', 2e6,...
              'StopbandAttenuation', 44,...
              'PassbandRipple',0.5,...
              'CenterFrequency',Fc,...
              'StopbandFrequencySource','Property',...
              'StopbandFrequency', stopbandFreq);

% Upconvert the baseband waveform to passband
dBdBmConvFactor = 30;
scalingFactor = 10^((outputPower-dBdBmConvFactor)/20);
upConvWaveform = scalingFactor*upConv(waveform);

rbwOutputPower = 3e6; % Resolution bandwidth, in Hz

[P,F,T] = pspectrum(upConvWaveform,interpFactor*Fs,'spectrogram',...
                               'TimeResolution',1/rbwOutputPower,...
                               'FrequencyLimits',[Fc,maxFreq]);
powerAtFc = P(1,:); % Extract power values at Fc (F(1) = Fc)

% Calculate average power, AVGPOWER over at least 20% to 80% of the
% duration of the burst as specified in Section 4.4.1 of the Bluetooth
% RF-PHY Test Specifications [3].
powerAvgStartIdx = floor(0.2*length(powerAtFc));
powerAvgStopIdx = floor(0.8*length(powerAtFc));
avgPower = round(10*log10(mean(powerAtFc(powerAvgStartIdx:powerAvgStopIdx)))+dBdBmConvFactor);

% Calculate peak power, PEAKPOWER
peakPower = 10*log10(max(powerAtFc))+dBdBmConvFactor;

% Plot power vs time
powerAtFcdBm = 10*log10(powerAtFc) + dBdBmConvFactor;
figure,plot(T,powerAtFcdBm)
grid on;
xlabel('Time (sec)');
ylabel('Power (dBm)');
title('Measured Output Power');

% Pass verdict - All measured values shall fulfill the following conditions:
%
% * Peak power <= (Average power + 3 dB)
% * -20dBm <= Average power <= 20dBm
%
fprintf('Measured average power and peak power are %f dBm and %f dBm, respectively.\n',avgPower,peakPower);

if avgPower <= 20 && avgPower >= -20 && (peakPower <= (avgPower+3)) 
    fprintf('Output power test passed.\n');
else
    fprintf('Output power test failed.\n');
end

if strcmp(packetType,'Disabled')
    % The function, <matlab:edit('helperBLEInbandEmissionsParams.m')
    % helperBLEInbandEmissionsParams.m>, is configured to generate dominant
    % test frequency parameters.
    [testFreq,idx1,idx2] = helperBLEInbandEmissionsParams(Fc,numDominantFreq,phyMode);

    % For each test frequency measure the power levels at the following 10
    % frequencies.
    numOffsets = 10;
    freqOffset = -450e3+(0:numOffsets-1)*100e3;
    adjChannelFreqOffsets = (freqOffset+testFreq-Fc).';

    spec = spectrumAnalyzer('SampleRate',Fs*interpFactor,...
        'YLimits', [-120 30], ...
        'Title', 'Power Spectrum',...
        'YLabel', 'Power (dBW)',...
        'SpectrumUnits','dBW',...
        'ShowLegend',true,...
        'FrequencySpan','Start and stop frequencies',...
        'StartFrequency',2400e6,...
        'StopFrequency',maxFreq,...
        'PlotMaxHoldTrace',true,...
        'PlotAsTwoSidedSpectrum',false);
    spec(upConvWaveform);

    rbw = 100e3;                                           % Resolution bandwidth, in Hz
    acprMeas = comm.ACPR('SampleRate',Fs*interpFactor,...
        'MainChannelFrequency',Fc,...
        'MainMeasurementBandwidth',2e6,...
        'AdjacentMeasurementBandwidth',1e5,...
        'PowerUnits','dBW',...
        'MainChannelPowerOutputPort',true,...
        'AdjacentChannelPowerOutputPort',true, ...
        'MaxHold',true, ...
        'SpectralEstimation',"Specify window parameters",...
        'Window','Hann', ...
        'SegmentLength',Fs*interpFactor/rbw);

    adjChnlPwr = zeros(numOffsets,numDominantFreq);
    for nFreq = 1:numDominantFreq
        % Assign the 10 frequency offsets at each test frequency to Adjacent channel offsets
        acprMeas.AdjacentChannelOffset = adjChannelFreqOffsets(:,nFreq)';

        % Compute adjacent channel power in dBW
        [~,mainChnlPwr,adjChnlPwr(:,nFreq)] = acprMeas(upConvWaveform); 
        release(acprMeas)
    end

    % Power levels at 10 frequency offsets at each test frequency are
    % calculated by adding main channel power to ACPR.
    adjChannelPower = adjChnlPwr(:,1:numDominantFreq);

    % Compute the power at each test frequency by adding all the powers
    % measured at 10 frequency offsets.
    adjPowerAtTestFreq = 10*log10(sum(10.^(adjChannelPower(:,1:numDominantFreq)/10))) + dBdBmConvFactor;
   

    % Plot the adjacent channel powers
    tick = 1:numel(adjPowerAtTestFreq);
    ticklabel = testFreq/1e9;
    figure;
    bar(adjPowerAtTestFreq, 'BaseValue', -120, 'FaceColor', 'yellow');
    set(gca, 'XTick', tick, 'XTickLabel', ticklabel, 'YLim', [-120 -20]);
    for i = tick
        text(i, adjPowerAtTestFreq(i), sprintf('%0.2f',adjPowerAtTestFreq(i)), ...
            'HorizontalAlignment', 'Center', 'VerticalAlignment', 'Top');
    end
    title('In-Band Emission Test Measurement');
    xlabel('Frequency (GHz)');
    ylabel('Power (dBm)');

    % Pass verdict- All measured values shall fulfill the following conditions:
    % For LE1M PHY transmission mode
    %
    % * powerAtTestFreq <= -20 dBm for testFreq = Fc ± 2 MHz
    % * powerAtTestFreq <= -30 dBm for testFreq = Fc ± [3+n] MHz; where
    %   n=0,1,2,...
    %
    % For LE2M PHY transmission mode
    %
    % * powerAtTestFreq <= -20 dBm for testFreq = Fc ± 4 MHz AND testFreq = Fc
    % ± 5 MHz
    % * powerAtTestFreq <= -30 dBm for testFreq = Fc ± [6+n] MHz; where
    %   n=0,1,2,...
    %
    for i = 1:numDominantFreq
        fprintf('Measured power at test frequency (Fc%+de6) is %.3f dBm.\n',(Fc-testFreq(i))*1e-6,adjPowerAtTestFreq(i));
    end
    if (all(adjPowerAtTestFreq(idx1) <= -20)||isempty(idx)) && (all(adjPowerAtTestFreq(idx2) <= -30)||isempty(idx2))
        fprintf('In-band emissions test passed.\n');
    else
        fprintf('In-band emissions test failed.\n');
    end
end