Concepts and features
R&S
®
ZNA
264
User Manual 1178.6462.02 ─ 20
●
T
rec
and
T
source
are the source and receiver noise temperature, respectively, deter-
mined during calibration
●
G
D
is the measured gain of the DUT
●
T
0
= 290
K is the reference temperature
Frequency-converting DUTs
Due to the existence of image (receive) bands, the noise figure of a frequency-convert-
ing DUT is calculated slightly different than the noise figure of a non-frequency-con-
verting DUT. The noise factor
F
D
of a frequency translating DUT is calculated using the
following formula:
where
●
N
DUT,meas
is the noise power measured with the DUT connected to the VNA
●
T
rec
is the receiver noise temperature, determined during calibration
●
T
source,RF
and
T
source,IM
are the noise temperatures at DUT input, at the RF and the
image frequency, respectively
●
G
D,RF
and
G
D,IM
represent the gain of the DUT, measured at the RF and the image
frequency, respectively
●
T
0
= 290
K is the reference temperature
Due to the small error introduced by the image band, image band correction is by
default deactivated. However, under
it can be activated. With active
image band correction, additional measurements are required to determine the gain
G
D,IM
and the source noise temperature
T
source,IM
.
Sideband correction
Typically, VNA receivers do not have any preselection filters within their signal paths.
However, due to their architecture, they exhibit additional receiving windows at higher-
order harmonics of the local oscillator frequency. Frequencies in these higher-order
sidebands are down-converted to the same IF frequency as the intended RF fre-
quency. Without additional measurements, these sideband contributions cannot be
separated from the contribution of the intended RF frequency band.
For typical network analyzer measurements with an active driving signal (S-parame-
ters, intermodulation, compression, ...), unsuppressed higher-order sidebands are not
an issue. Also for noise figure measurements on narrowband devices with less than an
octave bandwidth and an out-of-band suppression of more than 30 dB, they do not
impose significant measurement errors. But for noise figure measurements on a broad-
band DUT with several octaves of bandwidth (e.g. a distributed amplifier), they cer-
tainly cannot be ignored.
Noise figure option R&S
ZNA-K30 uses a patented algorithm to remove the error intro-
duced by the higher-order sidebands, and to calculate the true NF of a DUT. Based on
Optional extensions and accessories
