R&S ZVB - Page 312

R&S
®
ZVA / R&S
®
ZVB / R&S
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ZVT GUI Reference
Channel Menu
Operating Manual 1145.1084.12 – 30 297
constant input power of +35 dBm is maintained across the entire sweep range. The actual output power of
the analyzer is +5 dBm but the Port Power Result value shows the correct power value of +35 dBm at the
DUT.
The Cal Power Offset is also closely related to source power calibration:
 If you don't tell the analyzer about the external amplifier and simply set the channel base power to
+35 dBm, leaving Cal Power Offset, Attenuator and Port Power Offset at their defaults, a
subsequent source power calibration will yield correction values around -30 dB, which has two
potential hazards:
1. At the start of the first source power calibration sweep the output power of the analyzer
will roughly be 35 dBm, which may damage the amplifier.
2. If after a successful (non-destructive) source power calibration the power calibration is
turned off, the output power of the analyzer increases by 30 dB, which may destroy the
DUTs.
 With Cal Power Offset set to 30 dB and a Port Power Offset of +5 dB, on the other hand, the
correction values will be around 0 dB, eliminating the potential hazards described above.
Because of this, the Cal Power Offset value is stored together with the calibration data in the calibration
pool. If a calibration is recalled at a later stage, the Cal Power Offset is set to its persisted value. To keep
the Port Power Result constant, the Port Power Offset is adjusted accordingly.
Relation between channel power and port power levels
The channel base power P
b
is defined by the following sweep settings:
 For a power sweep, the channel base power is equal to the stimulus range.
 For a frequency or CW sweep, the channel base power is a fixed Power value.
The actual output power at the ports (source power P
s
) is related to the channel power P
b
as follows:
Ps = Pb + c + <Slope> * f , if the Pb radio button is selected
Ps = Pb + <Slope> * f , if the 0 dBm radio button is selected
In the formulas above, f denotes the (current) source port frequency, c is the offset value entered in the
Port <nr> Source Power dialog minus the Attenuator setting. The Slope parameter is set in the Source
section of the Port Configuration table.
A source port power that is used as a reference power must be a function of the channel base power
P
b
. The analyzer prevents inconsistent settings: E.g. if the source power at port 1 is selected as a
reference power (Stimulus dialog, Power – Enter & Display: Port 1 Source), the 0 dBm radio button in the
Port 1 Power dialog becomes unavailable.
Use the Stimulus dialog to change all port power levels based on an arbitrary reference power.
Use the ...Port Power Limits in the System Configuration – Power tab if you want to limit the source power
at a physical port permanently.
The analyzer generates a warning if the power settings for one of the ports exceed the hardware limits. At
the same time, bit no. 14 in the ...INTegrity:HARDware status register is set. Reduce or increase the
power result until the warning disappears.
Remote
control:
SOURce<Ch>:POWer[:LEVel][:IMMediate]:OFFSet <numeric_value>, ONLY
| CPAD
SOURce<Ch>:POWer<Pt>:GENerator<Gen>:OFFSet <numeric_value>, ONLY |
CPAD