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4-12
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TRFL (calibrated)
The relative power measurement mode (SET REF) allows you to
make calibrated TRFL measurements without using a power sensor.
An example of this measurement technique is provided in Chapter 5.
HP-/B
The HP 8902A enables you to fully automate your RF Power and
TRFL measurements. Refer to your HP 8902A Operation and
Calibration Manual for set up and programming information.
Time Base
A time base input is provided on the rear panel of the HP 8902A. This
input allows you to connect the HP 8902A to an external 10 MHz
time base reference. The time base
circuitry
within the HP 8902A
automatically switches to the external time base and turns o f f its time
base output when an external time base of sufficient amplitude (0.5 Vpp)
is applied at the input. To verify that an external time base is being
used, key in 15.1 SPCL. The instrument will display a 1 if the external
time base is being used or a 0 if the internal time base is being used.
The fundamental difference between the RF Power and TRFL measurement
is their measurement bandwidth. The measurement bandwidth for the RF
Power measurement is set by the bandwidth of the power sensor being
used. For instance, the measurement bandwidth of the power sensor
used in the HP 11722A Sensor Module is 4 GHz, therefore the RF Power
measurement bandwidth of the HP 8902A is 4 GHz when used with the
HP 11 722A. Select the
RF
Power measurement when you wish to measure
total power of all modulation, sidebands, harmonics, and spurious on the
signal (as you would using an HP 436A or HP 438A type power meter).
The measurement bandwidth of the TRFL measurement is much narrower
than that of the RF Power measurement. When the IF Synchronous detector
is used to make a TRFL measurement, measurement bandwidth is 200 Hz.
When the IF Average detector is selected, measurement bandwidth is
determined by the bandwidth of the IF filter being used (30 kHz or
200 kHz). (The 30 kHz filter is automatically chosen by the instrument
when the IF Average detector is selected; refer to increasing
Selectivity
in this chapter for filter selection information.) The IF Average detector
measures the total power of the signals and noise present within the IF
filter passband. Select the TRFL measurement mode when you want to
make calibrated tuned level measurements of discrete input signals.
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