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101
Press [Span], input the occupied bandwidth span with the numeric keys and press the corresponding
unit. The default value is 3MHz.
j)
Turn off occupied bandwidth measurement:
Press [OBW Off On], select Off to exit the occupied bandwidth measurement, and the interface switches
back to the spectrum measurement interface.
VIII. Adjacent Channel Power Ratio Measurement
This Section illustrates the operation method of the adjacent channel power ratio measurement using
the S5105D/E/F microwave analyzer by taking the measurement of the adjacent channel power ratio
of the CDMA signal and GSM signal as an example.
1
Definition of adjacent channel power ratio
The adjacent channel power ratio (ACPR) is also called the Adjacent Channel Leakage Powet Ratio
(ACLR), which is the ratio of the transmit power of channel to the radiated power of its adjacent channel.
It is usually expressed by the ratio of the power in the specified bandwidth to the total channel power at
different frequency offsets of adjacent channels. The size of adjacent channel power mainly depends on
the extension of the edge band and noise of the transmitter.
The measurement method for adjacent channel power ratio can replace the traditional two-tone
intermodulation distortion measurement method applied to the nonlinear system test, and the adjacent
channel power ratio measurement result can be expressed as two different ways of power ratio or power
density.
The following takes the CDMA adjacent channel power ratio measurement and the GSM adjacent
channel power ratio measurement as an example, and details the operation steps of the adjacent
channel power ratio measurement using the S5105D/E/F microwave analyzer.
2
CDMA Adjacent Channel Power Ratio Measurement
In traditional measurements, for narrowband signals, two-tone intermodulation measurements are
commonly used to evaluate the distortion performance of the transmitter. CDMA is a wideband
modulated signal that not only has very tight spectral components, but also has a very high peak signal
(called a crest factor). These intermodulation products from the spectral components of the signal will
locate around the CDMA spectrum. Since the intermodulation measurement of CDMA signals is very
complicated, and adjacent channel power ratio (ACPR) is closely related to intermodulation products
caused by nonlinear distortion, so adjacent channel power ratio (ACPR) is a better method to measure
the nonlinear distortion of CDMA transmitters.
Steps for measuring the adjacent channel power ratio of the CDMA signal using the adjacent channel
power ratio measurement function of the S5105 Handheld Analyzer is:
a)
Reset the microwave analyzer to its default state:
Press
【
Reset
】
, [Default State] .
b)
Receive a CDMA signal through the antenna, or use a signal generator to generate a CDMA analog
signal and connected to the RF input of the microwave analyzer via cable.
c)
Set the reference level of Analyzer:
Press
【
Amplitude
】
, [Ref Level], -10 [dBm]
Press the [Scale] soft key to set the scale to 10dB/div.
d)
Set the resolution bandwidth and video bandwidth:
Press
【
BW
】
, [RBW Auto Man] , set the resolution bandwidth to 10kHz;
Press [VBW Auto Man] to set the video bandwidth to 30kHz or more.
e)
Switch to adjacent channel power ratio measurement:
Press
【
Measure
】
and [ACPR] to switch to the measurement interface of adjacent channel power ratio.
f)
Set the center frequency of the main channel:
Press [Center Freq] and set the center frequency of the main channel with the figure keys. For CDMA
