Giga-tronics 8003, Руководство по эксплуатации

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8003 Precision Scalar Analyzer
2-80 Manual 20791, Rev. C, June 2001
In a single-sensor return loss measurement, the incident power is measured during path calibration and
stored by the analyzer. It is then subtracted from the measured reflected power (subtracting dB’s is
equivalent to ratio’ing Watts). To set up the analyzer to make a single sensor return loss measurement,
first choose a channel to be your return loss channel. Then press the
[DEFINE]
key to bring up the
DEFINE softkey menu on the screen. Press the [ SINGLE SENSOR ] softkey and choose the sensor that
will be measuring the reflected power. Since path calibrations will be used, press
[MEAS]
and toggle
the [ ABS PWR/PTH CAL ] softkey until [ PTH CAL ] is active (light blue color).
To path cal the channel, first connect a short to the bridge or coupler test port. This will cause all of the
sweeper power to be reflected back to be measured by the reflected sensor - accounting for bridge or
coupler path losses. Press
[CAL]
and the [ SHORT/OPEN ] softkey. Then press the [ STORE SHORT X ]
softkey that corresponds to the sensor measuring the reflected power. Once the Short cal is done,
connect an OPEN to the bridge or coupler test port. Press the [
STORE OPEN X ] softkey to complete
the calibration.
Like insertion loss measurements, the single-channel return loss measurement is accurate as long as a
path cal is made and the sweeper power does not change. However, a two-sensor return loss
measurement can give better accuracy by improving the effective source match of the sweeper. See the
two sensor insertion loss in Section 2.9.2 for a more detailed explanation.
Figure 2-34: Return Loss Test Setup Using a Directional Coupler
NOTE:
The most accurate return loss calibration is the short/open calibration. It is possible
to calibrate the bridge or coupler with only a short or only an open - although with degraded
accuracy.
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