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Chapter 4 97
Making Measurements
Making the Spectrum (Frequency Domain) Measurement
Making the Spectrum (Frequency Domain)
Measurement
Purpose
The spectrum measurement provides spectrum analysis capability for
the instrument. The control of the measurement was designed to be
familiar to those who are accustomed to using swept spectrum
analyzers.
This measurement is FFT (Fast Fourier Transform) based. The
FFT-specific parameters are located in the
Advanced menu. Also
available under basic mode spectrum measurements is an
I/Q window, which shows the I and Q signal waveforms in parameters of
voltage versus time. The advantage of having an I/Q view available
while in the spectrum measurement is that it allows you to view
complex components of the same signal without changing settings or
measurements.
Measurement Method
The measurement uses digital signal processing to sample the input
signal and convert it to the frequency domain. With the instrument
tuned to a fixed center frequency, samples are digitized at a high rate,
converted to I and Q components with DSP hardware, and then
converted to the frequency domain with FFT software.
This measurement is available for both the RF input and baseband I/Q
inputs. For details on Baseband I/Q operation see “Using Baseband I/Q
Inputs (Option B7C)” on page 151.
Making the Measurement
NOTE The factory default parameters provide a good starting point.You will
likely want to change some of the settings. Press
Meas Setup, More (1 of
2)
, Restore Meas Defaults at any time to return all parameters for the
current measurement to their default settings.
Press
Measure, Spectrum (Freq Domain) to immediately make a spectrum
measurement.
To change any of the measurement parameters from the factory default
values, refer to the “Changing the Measurement Setup” section for this
measurement.