Documentation

# getFrequencyVector

Vector of frequencies at which estimation is done

## Syntax

``freq = getFrequencyVector(estimator)``
``freq = getFrequencyVector(estimator,Fs)``

## Description

example

````freq = getFrequencyVector(estimator)` returns the vector of frequencies at which the estimation is done.```
````freq = getFrequencyVector(estimator,Fs)` returns the frequency vector assuming an input sample rate, `Fs`.```

## Examples

collapse all

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.

```rbw = getRBW(estimator) ```
```rbw = 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

collapse all

Estimator object, specified as one of the following:

Input sample rate, specified as a real positive scalar.

## Output Arguments

collapse all

Spectrum frequencies, returned as a column vector.

The length of the frequency vector is determined by the `FrequencyRange` and the FFT length.

If you set the `FrequencyRange` to `'onesided'` and the FFT length, `NFFT`, is even, the frequency vector is of length `NFFT/2+1`, and covers the interval `[0,SampleRate/2]`.

If you set the `FrequencyRange` to `'onesided'` and `NFFT` is odd, the frequency vector is of length `(NFFT+1)/2` and covers the interval `[0,SampleRate/2]`.

If you set the `FrequencyRange` to `'twosided'`, the frequency vector is of length `NFFT` and covers the interval `[0, SampleRate]`.

If you set the `FrequencyRange` to `'centered'`, the frequency vector is of length `NFFT` and covers the range ```[-SampleRate/2, SampleRate/2]``` and `[-SampleRate/2, SampleRate/2]` for even and odd length `NFFT`, respectively.

Data Types: `single` | `double`