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Measuring TDMA Signals
Power Meter and Sensor Operation
The voltages generated by the diode detectors in the power sensor can be
very small. Gain and signal conditioning are required to allow accurate
measurement. This is achieved using a 220 Hz (440 Hz in fast mode) square
wave output from the power meter to drive a chopper- amplifier in the
power sensor. Digital Signal Processing (DSP) of the generated square wave
is used by the power meter to recover the power sensor output and
accurately calculate the power level.
The chopper- amplifier technique provides noise immunity and allows large
physical distances between power sensor and power meter (Agilent 11730
series cables available up to 61 metres). Additional averaging helps reduce
noise susceptibility.
Achieving Stable Results with TDMA Signals
The averaging settings in the power meter are designed to reduce noise
when measuring continuous wave (CW) signals. Initial measurement of a
pulsed signal may appear unstable with jitter on the less significant
displayed digits. With pulsed signals the averaging period must be increased
to allow measurement over many cycles of the pulsed signal.
To set the averaging proceed as follows:
Note
The example shows the key labels for a single channel power meter. Dual channel meter
are similar, adding only channel identification to the softkey labels.
System
1. Press
,
Input Settings
Inputs
access the filter menu.
2. The filter setting is displayed under the
change this setting first set manual mode by pressing the
Mode Man Auto
softkey to highlight
Length
3. Press
and use the
averaging you require. Confirm your entry by pressing
Making Measurements
Measuring TDMA Signals
,
. Press the
Filter
More
Length
softkey label. To
Man
.
,
,
or
softkey to
to set the
Enter
.
27
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