Concepts and Features
R&S
®
ZNC
87
User Manual 1173.9557.02 ─ 13
In general, a power calibration involves two stages:
1.
Source power calibration:
An external power meter is connected to the calibration
plane. The analyzer uses the power meter readings to calibrate its reference receiver.
Subsequently, it modifies its source power so that the calibrated reference receiver
reading corresponds to the desired source power value (flatness calibration).
2.
Measurement receiver calibration:
The analyzer uses the calibrated source signal
to adjust the power reading at the receive port.
3.5.6.1
Source Power Calibration
A source power calibration ensures an accurate power of the generated wave at an arbi-
trary calibration plane in the measurement path. Typically the calibration plane corre-
sponds to the input of the DUT.
In a frequency sweep, the power at the calibration plane is maintained at a constant "Cal
Power" value. The source power calibration eliminates frequency response errors in the
signal path between the source and the calibration plane. It is possible to introduce an
arbitrary attenuation or gain into the signal path so that the cal power is not restricted to
the power range of the source. A typical application for a power calibration in a frequency
sweep is the measurement of the gain of an amplifier across a frequency range but at a
fixed input power.
In a power sweep, the power calibration ensures that the power at the calibration plane
is either constant or a linear function of the stimulus power. A typical application for a
power calibration in a power sweep is the measurement of the gain of an amplifier across
a power range but at a fixed frequency. The correction data acquired in a frequency or
power sweep is re-used if a "Time" or "CW Mode" sweep is activated.
Calibration procedure
The source power calibration requires an external power meter, to be connected via GPIB
bus, USB or LAN interface. Use the USB-to-IEC/IEEE Adapter (option R&S ZVAB-B44 )
to control devices equipped with a GPIB interface. The power sensor can be connected
directly at the calibration plane or to any other point in the test setup where the signal
power is known to be proportional to the power at the calibration plane.
The source power calibration involves several steps:
1.
Reference receiver calibration:
The analyzer performs a first calibration sweep at
the source power that is likely to produce the target power ("Cal Power") at the cali-
bration plane. A known attenuation or gain at the source port and in the signal path
between the source port and the calibration plane can be taken into account:
Calibration