getRBW
Resolution bandwidth of spectrum
Description
Examples
Power Spectrum of Multichannel Sinusoidal Signal
Compute the power spectrum of a multichannel sinusoidal signal using the dsp.SpectrumEstimator
System object™. You can get the vector of frequencies at which the spectrum is estimated using the getFrequencyVector
function. To compute the resolution bandwidth of the estimate (RBW), use the getRBW
function.
Generate a three-channel sinusoid sampled at 1 kHz. Specify sinusoidal frequencies of 100, 200, and 300 Hz. The second and third channels have their phases offset from the first by and , respectively.
sineSignal = dsp.SineWave(SamplesPerFrame=1000,SampleRate=1000, ...
Frequency=[100 200 300],PhaseOffset=[0 pi/2 pi/4]);
Estimate and plot the one-sided spectrum of the signal. Use the dsp.SpectrumEstimator
object for the computation and the dsp.ArrayPlot
for the plotting.
estimator = dsp.SpectrumEstimator(FrequencyRange='onesided'); plotter = dsp.ArrayPlot(PlotType='Line',YLimits=[0 0.75], ... YLabel='Power Spectrum (watts)',XLabel='Frequency (Hz)');
Step through to obtain the data streams and display the spectra of the three channels.
y = sineSignal(); pxx = estimator(y); plotter(pxx)
Get the vector of frequencies at which the spectrum is estimated in Hz, using the getFrequencyVector
function.
f = getFrequencyVector(estimator);
Compute the resolution bandwidth (RBW) of the estimate using the getRBW
function.
getRBW(estimator)
ans = 0.0015
The resolution bandwidth of the signal power spectrum is 0.0015 Hz. This frequency is the smallest frequency that can be resolved on the spectrum.
Input Arguments
estimator
— Estimator object
dsp.SpectrumEstimator
| dsp.CrossSpectrumEstimator
| dsp.TransferFunctionEstimator
Estimator object, specified as one of the following:
dsp.SpectrumEstimator
–– Estimates the power spectrum of the input signal.dsp.CrossSpectrumEstimator
–– Estimates the cross-power spectrum of the input signal.dsp.TransferFunctionEstimator
–– Estimates the transfer function of the system.
Fs
— Input sample rate
positive scalar
Input sample rate, specified as a real positive scalar.
Output Arguments
RBW
— Resolution bandwidth
scalar
Resolution bandwidth of the estimate, returned as a scalar.
The resolution bandwidth, RBW
,
is the smallest positive frequency, or frequency interval, that can be resolved. It is
equal to NENBW*SampleRate/L
, where L
is the input
length, and NENBW
is the normalized effective noise bandwidth of the
window.
The data type of RBW
matches the data type of the input.
Data Types: single
| double
Version History
Introduced in R2013b
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