Rohde & Schwarz ZVAX24, Руководство по обслуживанию

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Instrument Construction and Function Description R&S ZVAX24
1312.7979.82 3.2 E-1
Description of the Block Diagram
The R&S ZVAX24 consists of a base unit with cabinet, power supply, interface printed circuit board and
fan. It is driven by the R&S ZVA24 via a USB interface. When the R&S ZVAX24 is connected, there is
only one unassigned USB interface remaining on the R&S ZVA24 rear panel; therefore, the
R&S ZVAX24 has a USB hub with two outputs on the front panel and two on the rear panel.
In order not to have to rely on the slow USB interface when switching over the harmonics filters during
the sweep, the filter banks can also be switched via the universal I/O port, a parallel interface that is
compatible with Agilent's ENA. However, this interface must also remain usable for other purposes and
is therefore available on the rear panel of the R&S ZVAX24 as well. While the 16 out bits of the
universal I/O port are being used internally to control the filter bank, they remain available on the rear-
panel interface. For this reason, their status originally set by the user must be restored by the
R&S ZVAX24. In addition, the interface printed circuit board contains two high-speed differential inputs
for driving the pulse modulators. Status LEDs on the front panel indicate the switching status of the
options described below. The only RF components already included in the base unit are the SMA
female connectors on the front and rear panels and the two connecting cables on the rear panel
(an external power amplifier can be looped in instead of the connecting cables).
The base unit can be fitted with the following options, which can be selected independently of one
another:
•
R&S ZVAX24-B210: Monitor output, port 2
To be able to monitor the spectrum of the DUT output signal during an S-parameter, conversion-
loss, intermodulation or noise measurement, the test signal of port 2 is coupled out via an optional
coupler and made available at a female connector on the front panel of the R&S ZVAX24.
A spectrum analyzer, for example, can be connected to this connector.
•
R&S ZVAX24-B211: Combiner, ports 1 and 3
The generator signals from ports 1 and 3, which come from different synthesizers and can therefore
be set to two different frequencies, are combined into a two-tone signal via a broadband combiner
that is looped into the signal paths by means of a transfer switch. This signal is output at port 1,
while port 3 is terminated with 50
E to ensure a good load match.
•
R&S ZVAX24-B251, -B253: Harmonics filter for generator, ports 1 and 3
To achieve the values of 51 dBc with the R&S ZVA – which features harmonic suppression of 20
dBc at 1 GHz, 10 dBm – an optional 1 GHz to 22 GHz filter bank can be looped into each of the
generator paths of ports 1 and 3. At port 3, the filter is required for differential measurements and for
measurements on mixers (spectral purity of RF and LO signals). To avoid the maximum generator
power at the test port being permanently reduced by the transmission loss of the filter bank, the filter
bank is looped into the generator signal path by means of a transfer switch.
•
R&S ZVAX24-B252: Harmonics filter for receiver, port 2
To prevent a harmonic measurement from being corrupted by a harmonics generated in the receiver
itself, the fundamental can be suppressed by a filter bank looped into the signal path of the receiver
of port 2. To avoid the dynamic range being permanently reduced by the transmission loss of the
filter bank, the filter bank is activated by means of a transfer switch.
•
R&S ZVAX24-B271, -B273: Pulse modulator, ports 1 and 3
For unbalanced DUTs that have to be operated only in forward-pulsed mode (e.g. power amplifiers),
a pulse modulator for the generator signal at port 1 is sufficient. A second pulse modulator for the
generator signal at port 3 is needed for balanced DUTs and for DUTs that also have to be pulsed in
the reverse direction (e.g. T/R modules for phased array pulse radar). To avoid the maximum
generator power at the test port being reduced by the transmission loss of the activated modulator
also in normal mode, the modulator is looped into the generator signal path by means of a transfer
switch only in pulsed mode. As a pulse generator, either the R&S ZVA24's FCON gate array can be
used, which is connected via the cascade interface, or an external generator whose signal is fed in
at one of the EXT PULSE GENERATOR IN connectors on the rear panel of the R&S ZVAX24.