To measure adjacent-channel power
This task shows an additional method of measuring adjacent-channel power.
The method shown on the previous page is preferred when carriers are
represented by a single tone. This second method is used when carriers are
heavily modulated or are defined over a band.
1 Use the band power markers, as shown in “To measure band power” to
perform an rms (video) averaged measurement of the desired band
encompassing the carrier. Save the trace in a register, for example register D1.
2 Create a math function: F1=SQRT(SPEC1*SPEC1/D1*D1). See “To create a
math function.”
3 Move the band power markers to encompass the desired adjacent-channel and
perform an rms averaged measurement.
4 Select the math function as measurement data:
Press [
Measurement Data
], [
math func], [F1]
5 Start a new rms (video) average.
Press [
Meas Restart
],
In rms averaging the power spectrum is in linear units (volts), rather than power
units, with its real part all positive and its imaginary part all zero. Therefore, the
spectra must be squared for use in power calculations.
Band power markers and a math function are used to determine
the ratio between the carrier power and adjacent-channel power.
Adjacent channel
power ratio
Carrier power spectrum is
used in a math function.
A math function
calcluates a ratio
Making Simple Noise Measurements
2-6
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