Concepts and Features
R&S
®
ZNB/ZNBT
193
User Manual 1173.9163.02 ─ 38
Table 4-16: Additional Test Ports for R&S
ZNBT20
9 to 12
13 to 16
17 to 20
21 to 24
w/o Extended Dynamic Range
R&S
ZNBT20-
B112
R&S
ZNBT20-
B116
R&S
ZNBT20-
B120
R&S
ZNBT20-
B124
The instrument needs to be returned to Rohde
&
Schwarz service for ex post installa-
tion of additional ports.
4.7.2 Time Domain Analysis
Option R&S
ZNB-K2 / R&S
ZNBT-K2
The network analyzer measures and displays complex S-parameters and other quanti-
ties as a function of the frequency. The measurement results can be filtered and math-
ematically transformed in order to obtain the time domain representation, which often
gives a clearer insight into the characteristics of the DUT.
Time domain transforms can be calculated in band pass or low pass mode. For the lat-
ter the analyzer offers the impulse and step response as two alternative transformation
types. A wide selection of windows can be used to optimize the time domain response
and suppress sidelobes due to the finite sweep range. Moreover, it is possible to elimi-
nate unwanted responses by means of a time gate and transform the gated result back
into the frequency domain.
For a detailed discussion of the time domain transformation including many examples
refer to the application note 1EZ44 which is available on the R&S internet at
www.rohde-schwarz.com/appnotes/1EZ44
4.7.2.1
Chirp z-Transformation
The Chirp z-transformation that the analyzer uses to compute the time domain
response is an extension of the (inverse) Fast Fourier Transform (FFT). Compared to
the FFT, the number of sweep points is arbitrary (not necessarily an integer power of
2), but the computation time is increased by approx. a factor of 2. This increased com-
putation time is usually negligible compared to the sweep times of the analyzer.
The following properties of the Chirp z-transformation are relevant for the analyzer set-
tings:
●
The frequency points must be equidistant.
●
The time domain response is repeated after a time interval which is equal to Δt =
1/Δf, where Δf is the spacing between two consecutive sweep points in the fre-
quency domain. For a sweep span of 4 GHz and 201 equidistant sweep points, Δf
= 4 GHz/200 = 2 * 10
7
Hz, so that Δt = 50 ns. Δt is termed measurement range (in
time domain) or unambiguous range.
Additional constraints apply if the selected Chirp z-transformation is a lowpass transfor-
mation.
Optional Extensions and Accessories