# FFT Channel Power

The FFT Channel Power measurement measures the power of the FFT within the band specified. Multiple bands may be measured simultaneously using multiple measurements. To set up FFT function waveforms, see FFT Operator.

You can specify the frequency band using these controls (when you add or edit the measurement):

- Channel Center — Specifies the center frequency used for the measurement.

- Channel Bandwidth — Specifies the width of the FFT frequency band.

If the FFT units are in dBm, dBmV, or dBuV, the FFT channel power is calculated using the following equation:

Where:

- Pch = the power in the channel (dBm).
- Bs = the specified bandwidth, also known as the channel bandwidth (Hz).
- RBW = the resolution bandwidth (Hz).
- N = the number of data points in the summation.
- Pi = the sample of the power in measurement cell "i" in dBm units.

Because the frequency range typically does not align with the FFT bins, the first and last points are linearly interpolated.

If the FFT units are in Watts, the FFT channel power is calculated using the following equation:

If the FFT units are in Vrms, values are converted to Watts, and the above equation is used to calculate the FFT channel power.

## To measure

1. Click the toolbar's FFT tab.

2. If necessary, click the toolbar's More buttons to locate the FFT Channel Power button.

3. Click the button.

4. In the FFT Channel Power dialog box, select the FFT function waveform on which to make the measurement.

5. Enter the Channel Center and Channel Bandwidth options to specify the frequency band you want to measure.

6. Click Apply.

## SCPI Command

`:MEASure:FFT:FCPower`