Concepts and Features
R&S
®
ZNA
193
User Manual 1178.6462.02 ─ 12
TD S
VSWR
Calculation
The ANSI time-domain method relies on a complex transmission measurement (S
21
)
using a vector network analyzer (VNA).
A time-domain transformation of the frequency domain data shows the impulse
response between the two antennas. Since the direct antenna-to-antenna response is
related to the shortest distance, the earliest impulse is the direct antenna response.
Reflections from the test site are from farther distance away, thus come at later time. It
is therefore possible to separate the direct antenna response S
21, direct
from reflections
S
21, reflected
by using time gating and to calculate
TD
S
VSWR
= (1+r) / (1-r)
,
where r = S
21,reflected
/ S
21,direct
.
Measurement Procedure for ANSI C63.25
See the Rohde & Schwarz Application Card "Fast validation of EMC Test Sites above 1
GHz with Time-domain S
VSWR
", published on the Rohde
&
Schwarz internet site.
5.7.2.7
Extended Time Domain Analysis
Option R&S
ZNA-K20
Option K20 extends the basic Time Domain representation capabilities of option K2 by
signal integrity testing functionality in the time domain.
Simulated Eye Diagram
With the impulse response calculated from the measured S parameters using the
inverse Fourier transform, it is possible to predict the system response to arbitrary time
domain signals by calculating the convolution of the input signal with the impulse
response.
With option R&S
ZNA-K20, the R&S
ZNA firmware implements a "virtual" signal gener-
ator that is able to generate multilevel PAM signals (NRZ, PAM-4, PAM-8, PAM-16),
including a simulated low pass behavior. The simulated eye diagram using the DUT's
measured S parameters gives an extensive overview regarding the signal integrity of
the system.
Further building blocks for pre-emphasis, jitter, noise and equalization allow you to syn-
thesize effects of transmitter and receiver parts in the transmission system.
Optional Extensions and Accessories
