Agilent Technologies E4406A, User Manual

Page: 91 / 230

Chapter 4 91
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 signals 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 transmitter tester 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.
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 Spectrum
(Frequency Domain) the active measurement.
To change any of the measurement parameters from the factory default
values, refer to the “Changing the Measurement Setup” section for this
measurement.
Results
A display with both a spectrum window and an I/Q Waveform window
will appear when you activate a spectrum measurement. Use the
Next
Window
key to select a window, and the
Zoom
key to enlarge a window.