Agilent Technologies 8560E User Manual page 115

Agilent technologies 8560 e-series and ec-series spectrum analyzers

Table of Contents

Adjacent Channel Power (ACP) Instrument Setup

Settings of the reference level, input attenuation, and display scale are

not changed by the ACP auto measurement function. They must be set

for optimum dynamic range to optimize accuracy.

Although linear and other logarithmic scales are supported, only the

log 10 dB per division scale has adequate dynamic range for ACP

measurements; thus, it should always be used. The reference level (RL)

should be chosen so that the signal exceeds neither the top nor the

bottom of the ﬁdelity-speciﬁed range of the chosen (10 dB per division)

scale. When the signals in the channel are CW-like, the optimum RL is

that for which the largest signal is at the RL.

When the signals in the channel are noise-like, as is the case for most

digital modulations, the optimum RL depends on the range of the

logarithmic ampliﬁer and other parameters. The difference between the

transmitter power and the optimum reference level is given by:

is the total transmitted power.

RBW is the spectrum analyzer resolution bandwidth.

ChBW is the channel bandwidth.

RL is the reference level power (note that the units must be

power units, for example, mW, and match those of P

logrange is the speciﬁed range of the log ampliﬁer, a positive

number (100 dB for the 8560 Series and EC-Series Spectrum

is the ratio of the adjacent channel power to the

transmitter power, expressed in dB, and is always a negative

The setting of the input attenuator of the spectrum analyzer

determines the tradeoff between the distortion errors and noise errors.

The following equation expresses the optimum choice of input

attenuation for a spectrum analyzer.

Example 9: Adjacent Channel Power Measurement

----------------------- -

0.439 logrange

Making Measurements