Technical data

12
Obtaining Absolute Power Measurements on Associated Measuring Instruments
Measurements that Requires Real-Time Synchronization (Trigger)
Some data bus cabling, such as USB or GPIB, allows a certain degree of
measurement synchronization (in the millisecond range). However, in many
measurement environments, real-time triggering is a necessity. These will call
for trigger synchronization in the microsecond region. The following sections
provide several suggested applications:
• If more than one U2000 Series is used in a system monitoring application,
all the sensors are to monitor the power signal with complex modulation.
There may be a need to synchronize the data sampling to coincide with the
communications clock. In this application, a common video trigger pulse will
be used to connect to all the real-time trigger inputs of the multiple sensors.
Typical communications formats are the GSM (pulsed) signals.
• The triggering port can also be used to synchronize the measurements with
an external instrument or event, for instance, the calibration of the output
power of a synthesizer that is sweeping in frequency. The triggering port
can be used to accept a trigger signal from the synthesizer to initiate the
measurement with every frequency step.
Many modern test instruments have powerful signal processing and displays of
a variety of important parameters. Spectrum analyzers provide many different
signal characteristics versus frequency, including nominal power levels of
unknown signals. Network analyzers, with their multi-band signal sources are
great for measuring S-parameters of all sorts of passive and active components.
Digital signal analyzers also characterize the digital formats of common
communications signals.
However, none of these instruments, in spite of their on-board computers and
analysis, can obtain an absolute power measurement of the signal under test.
The U2000 Series can be included in those measurement setups and feed
absolute power measurement data directly to the main measurement instrument
on-board processor.
Alternatively, the U2000 Series can be used to assure the output power
specifi cations of the transceiver, without needing an extra power meter. This can
be applied to a signal generator that is used to stimulate a sub-system under
test, for example, a transceiver within the microwave frequency range.