System Overview
R&S
®
ZVA
93
Quick Start Guide 1145.1090.62 ─ 10
assess the phase information, the IF signal at the mixer output is converted back to the
original RF frequency using a second MEAS mixer. A third REF mixer ensures that the
reference wave is converted back to the RF frequency.
3.5.5 True Differential Mode (R&S ZVA-K6)
Differential transmission lines and circuits are widely used, because their characteristics
give them a lower susceptibility to electromagnetic interference. Linear balanced devices
can be tested with sufficient accuracy using the virtual differential mode, where the vector
network analyzer generates unbalanced stimulus signals and uses a mathematical trans-
formation to convert unbalanced wave quantities into balanced S-parameters. A different
behavior is expected for nonlinear balanced devices, where the transmission character-
istics of the DUT may depend on how closely the stimulus signal matches real operating
conditions.
In "True Differential Mode", the vector network analyzer generates true differential and
common mode stimuli at arbitrary reference planes in the test setup and determines
mixed-mode S-parameters, wave quantities and ratios. The true differential mode also
provides two additional sweep types, the amplitude imbalance and phase imbalance
sweeps.
As an alternative to true differential mode, the Defined Coherence Mode provides several
source signals with defined phase and amplitude relation.
3.5.6 Measurements on Pulsed Signals (R&S ZVA-K7)
Measurements on pulsed RF signals are required in many areas of RF and microwave
technology. Pulsed signals are used in mobile phone applications and radar systems,
and amplifiers are typically designed for pulsed rather than continuous wave (CW) con-
ditions.
The analyzer performs pulsed measurements in analogy to a time sweep (i.e. at constant
receiver frequency), but with a much higher sampling rate of 12.5/ns. The raw I/Q ampli-
tudes are written into a ring buffer and processed at the end of each sweep. The buffer
size allows for a maximum recording time (sweep time) of 3 ms. Due to the high sampling
rate and the large IF bandwidths available, it is possible to obtain profiles for pulse widths
from approx. 200 ns to the maximum recording time. Of course it is also possible to
measure a sequence of pulses up to the maximum recording time.
3.5.7 Converter Control (R&S ZVA-K8)
Measurements at frequencies beyond the analyzer's operating range (mm-wave meas-
urements) are achieved by combining a frequency-converting measurement with an
external test set (frequency converter). The frequency converters use frequency multi-
pliers to transform the RF source signal from one of the network analyzer ports into a
high-frequency stimulus signal. A dual directional coupler separates the reference and
measurement channels from the waveguide test port. A second signal (Local Oscillator,
LO) is used for down-conversion of the reference and measurement channels. The LO
Optional R&S ZVA Extensions
