Concepts and features
R&S
®
ZND
220
User Manual 1173.9557.02 ─ 61
4.7.20
External switch matrices
4.7.20.1
Overview
From the perspective of the VNA, the purpose of a switch matrix is to extend the num-
ber of test ports. I.e. it converts an N-port network analyzer into an N'-port network
analyzer (N'>N) without modifying the instrument itself. The increased number of test
ports can reduce or even eliminate the manual reconnections of the DUT, resulting in a
higher measurement speed, reliability and repeatability.
The firmware of the R&S
ZND is able to control switch matrices from Rohde & Schwarz
directly. In combination with an R&S
ZN-Z84 it can work as a multi-port network ana-
lyzer with up to 24 ports, seamlessly performing the required matrix switching opera-
tions.
●
Switch matrices require a
bidirectional
R&S
ZND.
●
Matrix cascading is
not
supported.
However, an N-port analyzer is always limited to measuring N signals simultaneously.
I.e. even though the DUT is fully connected to the switch matrix, it may not be possible
to measure all b-waves simultaneously. For example, consider a DUT with 6 unbal-
anced ports, connected to a 2-port analyzer via a 2x6 matrix (e.g. a R&S ZN-Z8x base
unit without extensions). For each stimulus port, 5 sweeps are required to measure the
resulting b-waves, 6·5 = 30 sweeps in total.
Furthermore, each additional sweep requires at least one matrix switching procedure.
This involves command processing and physical switching and hence can take some
time to complete. For mechanical switches (such as R&S ZV-Z81 variant 66), in partic-
ular, switching is quite slow and causes mechanical wear. To optimize the measure-
ment setup w.r.t. speed and resources, the characteristics of the available switch matri-
ces have to be accounted for.
4.7.20.2
Matrix setup and operation
Setting up a switch matrix at the R&S
ZND firmware typically involves the following
steps:
1. establish the physical connection via the appropriate management interface (USB
or LAN).
2. register the matrix (as managed object).
3. define the RF configuration:
a) configure the matrix-VNA-connections according to the existing (or planned)
physical connections between VNA test ports and matrix VNA ports.
b) assign the matrix test ports and the remaining VNA ports (i.e. those that are not
connected to a matrix VNA port) to DUT test ports.
Optional extensions and accessories
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