R&S ZVB - Page 133

R&S
®
ZVA / R&S
®
ZVB / R&S
®
ZVT GUI Reference
Trace Menu
Operating Manual 1145.1084.12 – 30 118
Intermod Distortion Quantities (for R&S ZVA and R&S ZVT)
The Intermod Distortion Quantities submenu provides the results of the intermodulation distortion
measurement, enabled with option R&S ZVA-K4. The results are available as soon as the measurement
has been properly configured using the intermodulation wizard (Channel – Mode – Intermod Distortion
Meas – Define Intermod Distortion Meas).
Intermodulation distortion quantities
A nonlinear DUT that is supplied with a two-tone signal with the lower/upper frequencies f
L
and f
U
causes
emissions at frequencies which correspond to sums and differences of the upper and lower tone
frequencies and their integer multiples:
f
U
– f
L
, f
U
+ f
L
, 2*f
U
– f
L
, 2*f
U
+ f
L
, f
U
+ 2*f
L
, 2*f
L
– f
U
...
The order of these intermodulation products is defined by the number of f
L
and f
U
terms. The analyzer
measures the intermodulation products of k
th
order IMk (where k = 3, 5, 7, 9) at the lower tone frequency
minus (k – 1)/2 times the tone distance and at the upper tone frequency plus (k – 1)/2 times the tone
distance. Intermodulation products can be measured at the DUT input (wave a
1
) or at the DUT output
(wave b
2
).
The intermodulation suppression IMk
rel
is the ratio between the power of an intermodulation product to the
power of the lower or upper tone, whichever is smaller.
For each intermodulation product, an intercept point IPk is defined as follows:
IPk = P
L
+ IMk
rel
/ (k – 1)
In this formula, P
L
denotes the lower tone power in dBm, measured either at the DUT input or at the DUT
output; the intermodulation suppression IMk
rel
is always measured at the DUT output.
The intermodulation suppression generally decreases with increasing stimulus power. The intercept point
is equal to the lower tone power for which the intermodulation suppression would reach 0 dB. The
intercept point is a mathematical concept. For most DUTs, it is beyond the nominal power operating
range.
Automatic filter settings
Intermodulation measurements require frequency-selective filter settings. When an intermodulation result
is selected, the analyzer checks whether the IF bandwidth of the active channel is below 1/10 of the Tone
Difference (see Define Intermodulation Distortion). If not, the IF bandwidth is reduced and a high
sensitivity filter is selected. The analyzer displays a tooltip.