Этот пример показывает, как выполнить тестовые измерения передатчика, характерные для выходной степени и внутриполосных выбросов на переданных формах волны Bluetooth ® Low Energy (BLE) согласно спецификациям тестирования Bluetooth RF-PHY [1], используя библиотеку Communications Toolbox™ для протокола Bluetooth ®.
Спецификации тестирования Bluetooth RF-PHY [1], определенные Bluetooth Special Interest Group (SIG), включают тесты RF-PHY как для передатчика, так и для приемника. Цели этих тестов RF-PHY состоят в том, чтобы гарантировать совместимость между всеми устройствами BLE и проверить, что базовый уровень производительности системы гарантирован для всех продуктов BLE. Каждый тест имеет определенную процедуру тестирования и ожидаемый результат, который должен быть удовлетворен тестируемой реализацией (IUT).
Этот пример выполняет выходы степени и внутриполосных испытаний на выбросы в соответствии со спецификациями тестирования Bluetooth RF-PHY [1]. Измерение мощности разработано, чтобы гарантировать, что уровни степени достаточно высоки, чтобы поддерживать совместимость с другими устройствами Bluetooth и достаточно низки, чтобы минимизировать помехи в полосе ISM. Внутриполосный тест на излучение должен проверить, что уровень нежелательных сигналов в частотной области значений от передатчика не превышает заданных пределов. Идентификаторы контрольного примера, соответствующие тестам, рассматриваемым в этом примере, следующие:
Выходная степень:
RF-PHY/TRM/BV-01-C: Этот тест проверяет максимальную пиковую и среднюю степень, излучаемую IUT, в пределах допустимых значений.
Внутриполосные выбросы:
RF-PHY/TRM/BV-03-C: Этот тест проверяет, что внутриполосные выбросы находятся в пределах, когда передатчик работает с незакодированными данными со скоростью 1 Мс/с.
RF-PHY/TRM/BV-08-C: Этот тест проверяет, что внутриполосные выбросы находятся в пределах, когда передатчик работает с незакодированными данными со скоростью 2 Мс/с.
% Check if the 'Communications Toolbox Library for the Bluetooth Protocol' % support package is installed or not. commSupportPackageCheck('BLUETOOTH');
Можно изменить phyMode, Fc, outputPower и numDominantFreq параметры, основанные на режиме передачи PHY, частоте операции, выходной степени и количестве доминирующих частот, соответственно.
% Select PHY transmission mode {'LE1M','LE2M'} as per Bluetooth RF-PHY Test % Specifications phyMode ="LE1M"; % 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] numDominantFreq =
6; % Select number of dominant frequencies for in-band emissions test, must % be in the range [1,78] and [1,74] for LE1M and LE2M modes, respectively. % The number of dominant frequencies represents the number of test % frequencies near the operating frequency at which the in-band emissions % test is to be performed. The number chosen in this example leads to a % short simulation. For performing complete in-band emissions test, change % the |numDominantFreq| parameter to maximum number of dominant frequencies % as specified in the Section 4.4.2 of the Bluetooth RF-PHY Test % Specifications.
Функция helperBLETestWaveform.m сконфигурирована для генерации тестового сигнала BLE в соответствии со спецификациями Bluetooth [2].
payloadType = 0; % Payload type for PRBS9 sequence waveform = helperBLETestWaveform(payloadType,payloadLength,sps,phyMode); % 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 BLE 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 % Frequency span must be zero so that the power measurement is performed in % the time domain. Span 0 can be replicated by taking power values from the % spectrogram at frequency of operation (Fc). Frequency limits are % considered starting from frequency of operation (Fc) up to maximum % frequency in the frequency band. [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. powerAvgStartIdx = floor(0.2*length(powerAtFc)); powerAvgStopIdx = floor(0.8*length(powerAtFc)); avgPower = 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);
Measured average power and peak power are 19.792337 dBm and 20.363062 dBm, respectively.
if (-20 <= avgPower <= 20) && (peakPower <= (avgPower+3)) fprintf('Output power test passed.\n'); else fprintf('Output power test failed.\n'); end
Output power test passed.
% 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).'; % Create and configure a spectrum analyzer for the waveform sampling rate % and a resolution bandwidth of 100 kHz as specified in Section 4.4.2 of % the Bluetooth RF-PHY Test Specifications. rbw = 100e3; % Resolution bandwidth, in Hz spectrumScope = dsp.SpectrumAnalyzer( ... 'SampleRate', Fs*interpFactor,... 'SpectralAverages', 10, ... 'YLimits', [-120 30], ... 'Title', 'Power Spectrum of In-band Emissions',... 'YLabel', 'Power (dBW)',... 'SpectrumUnits', 'dBW',... 'ShowLegend', true,... 'FrequencySpan', 'Start and stop frequencies',... 'StartFrequency', 2400e6,... 'StopFrequency', maxFreq,... 'RBWSource', 'Property',... 'RBW', rbw,... 'PlotMaxHoldTrace', true,... 'PlotAsTwoSidedSpectrum', false); spectrumScope.ChannelMeasurements.Enable = true; spectrumScope.ChannelMeasurements.Algorithm = 'ACPR'; spectrumScope.ChannelMeasurements.CenterFrequency = Fc; spectrumScope.ChannelMeasurements.Span = 2e6; % Main channel bandwidth spectrumScope.ChannelMeasurements.AdjacentBW = 1e5; % Adjacent channel bandwidth spectrumScope.ChannelMeasurements.NumOffsets = numOffsets; % Compute adjacent channel power ratio (ACPR) for the transmitted waveform acpr = zeros(numOffsets,numDominantFreq); for i = 1:numDominantFreq % Assign the 10 frequency offsets at each test frequency to ACPR Offsets spectrumScope.ChannelMeasurements.ACPROffsets = adjChannelFreqOffsets(:,i); % Estimate the power spectrum of the transmitted waveform using the spectrum analyzer spectrumScope(upConvWaveform); % Compute ACPR data = getMeasurementsData(spectrumScope); % Get the measurements data mainChannelPower = data.ChannelMeasurements.ChannelPower; % Main channel power at Fc acpr(:,i) = data.ChannelMeasurements.ACPRUpper; % Extract the ACPR values end
% Power levels at 10 frequency offsets at each test frequency are % calculated by adding main channel power to ACPR. adjChannelPower = acpr(:,1:numDominantFreq) + mainChannelPower; % 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
Measured power at test frequency (Fc+4e6) is -79.393 dBm. Measured power at test frequency (Fc+3e6) is -72.852 dBm. Measured power at test frequency (Fc+2e6) is -32.670 dBm. Measured power at test frequency (Fc-2e6) is -30.924 dBm. Measured power at test frequency (Fc-3e6) is -72.038 dBm. Measured power at test frequency (Fc-4e6) is -78.351 dBm.
if (all(adjPowerAtTestFreq(idx1) <= -20)||isempty(idx1)) && (all(adjPowerAtTestFreq(idx2) <= -30)||isempty(idx2)) fprintf('In-band emissions test passed.\n'); else fprintf('In-band emissions test failed.\n'); end
In-band emissions test passed.
Этот пример продемонстрировал тестовые измерения передатчика, характерные для выходной степени и внутриполосных выбросов на переданных сигналах BLE, согласно спецификациям тестирования Bluetooth RF-PHY [1].
В этом примере используются следующие вспомогательные функции:
Спецификация тестирования Bluetooth RF-PHY.
Том 6 спецификации ядра Bluetooth версии 5.0 Core System Package [Low Energy Controller Volume].
