Agilent Technologies E4406A, User Manual

Page: 115 / 230

Chapter 4 115
Making Measurements
Making the Channel Power Measurement
Making the Channel Power Measurement
Purpose
The Channel Power measurement is a common test used in the wireless
industry to measure the total transmitted power of a radio within a
defined frequency channel. This procedure measures the total power
within the defined channel. This measurement is applied to design,
characterize, evaluate, and verify transmitters and its components or
devices for base stations and mobile stations.
Measurement Method
The Channel Power measurement reports the total power within the
channel bandwidth. The transmitter tester acquires a number of points
representing the input signal in the time domain. It transforms this
information into the frequency domain using FFT and then calculates
the channel power. The effective resolution bandwidth of the frequency
domain trace is proportional to the number of points acquired for FFT.
The fastest FFT process is achieved using a number of acquired points
that is a power of 2 (for example: 64, 128, 512). Since the measurement
is optimized for speed and accuracy, you are permitted to change only
the number of acquired data points in powers of 2, not the actual
resolution bandwidth. However, if absolute sweep time is required,
sweep time can be changed to the user’s specified time at the expense of
reduced speed. At no time will both sweep time and data points be set
to manual because of conflicting parameter settings. This flexibility is
available through the
Advanced
menu of the channel power
measurement.
To improve repeatability, you can increase either the number of
averages or the number of data points with longer time record length.
The channel power graph is shown in the graph window and the
absolute channel power in dBm and the mean power spectral density in
dBm/Hz are shown in the text window.
Making the Measurement
NOTE
The factory default settings 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.
Select the desired center frequency.
Press
Measure
, Channel Power to immediately make Channel Power
the active measurement.