Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 343 / 813

R&S
®
ZVA/ZVB/ZVT Channel Menu
1145.1084.12 4.181 E-6
Virtual Transform
The Virtual Transform submenu defines virtual networks to be added to/removed from the measurement
circuit for a DUT with single ended or balanced ports. The submenu is available for analyzer models
with arbitrary numbers of ports.
Embedding a DUT into a matching network
To be integrated in application circuits, high-impedance components like Surface Acoustic Wave (SAW)
filters are often combined with a matching network. To obtain the characteristics of a component with
an added matching network, both must be integrated in the measurement circuit of the network
analyzer. The figure below shows a DUT with a single-ended and a balanced port that is combined with
a real matching circuit and a physical balance-unbalance transformer (balun) in order to be evaluated in
a 2-port measurement.
The idea of virtual embedding is to simulate the matching network and avoid using physical circuitry so
that the analyzer ports can be directly connected to the input and output ports of the DUT. The
matching circuit is taken into account numerically. The analyzer measures the DUT alone but provides
the characteristics of the DUT, including the desired matching circuit. This method provides a number of
advantages:
•
The measurement uncertainty is not impaired by the tolerances of real test fixtures.
•
There is no need to fabricate test fixtures with integrated matching circuits for each type of
DUT.
•
Calibration can be performed at the DUT's ports. If necessary (e.g. for compensating for the
effect of a test fixture) it is possible to shift the calibration plane using length offset parameters.