China Electronics Technology Instruments AV3672 Series, User Manual

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6 Measurement Optimization
6.2 Improvement of Reflection Accuracy of Low-loss 2-port Device
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Menu path: [Analysis] > [Time Domain] > [Time Domain Transformation...] .
Click the [Transform] check box in the [Transform] dialog box to activate the transformation mode. Click the
required transformation mode: low-pass impulse, low-pass step and band pass. Click [Frequency: low pass] to
select the low pass mode. Click the drop-down list in the gate type box to select the gate type: band pass and trap.
Set the gate threshold by setting the start value, stop value, center value or span . Click [Transform] in the trace
menu.
6.2 Improvement of Reflection Accuracy of Low-loss 2-port Device
In order to realize accurate reflection measurement in one-port calibration, connect the unmeasured port. This
method is particularly suitable for low-loss two-way devices, such as the filter passband and cable. The direction,
source matching and frequency response error can be corrected by means of one-port calibration. The load
matching error cannot be calibrated. Therefore, the load matching error must be minimized.
Connect the unmeasured port in the following methods:
➢
Connect the unmeasured port of the DUT to one high-performance terminal load (the calibration kit is also
allowed). The measurement accuracy of this method is close to that of 2-port calibration.
➢
Connect the unmeasured port of the DUT directly to the analyzer. Insert one 10dB precision attenuator
between the device output and analyzer. The effective load matching of the analyzer can be improved by once
based on the measured value of the attenuator, i.e. 20dB.
Prompt
Matched load
No consideration should be given to load matching in measurement of the device of high reverse isolation, such as
the amplifier.
Fig. 6.1 shows the instability of measurement of the DUT with or without 10dB precision attenuator at the end.
Fig. 6.1 Comparison of Instability
Refer to the filter reflection.
Refer to the instability of measurement without 10dB precision attenuator.
Refer to the instability of measurement with 10dB precision attenuator.
Fig. 6.2 shows the accurate reflection measurement of the 2-port device. The following calculation shows the
improvement of loading matching with one high-quality 10dB attenuator.