![Rohde & Schwarz 1311.6010.22 User Manual Download Page 210](http://html.mh-extra.com/html/rohde-and-schwarz/1311-6010-22/1311-6010-22_user-manual_1477768210.webp)
Concepts and Features
R&S
®
ZNB/ZNBT
210
User Manual 1173.9163.02 ─ 53
blue arrow
= direct signal
red and green arrows = reflected signal
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.
Optional Extensions and Accessories