China Electronics Technology Instruments AV3672 Series, User Manual

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8 Basis of Network Measurement
8.3 Amplifier Parameter Specifications
248
Phase Format
Fig. 8.9 Phase Format of Analyzer
8.2.4 Type of Phase Measurement
1) Complex impedance: the complex impedance data such as the resistance, reactance, amplitude and phase can be
determined by S
11
and S
22
measurement and observed in the Smith chart and polar coordinate format. See details in
“
8.4 Complex Impedance
”.
2) AM-PM transformation: the unexpected phase deviation may be caused by system amplitude changes in the
AM-PM transformation measurement, defined as the output phase change of each 1dB increase of the power input
into the amplifier, in degree/dB. Measurement is done at the 1dB gain compression point. See details in “
8.7 AM-
PM Transformation
”.
3) Linear phase deviation: refer to the phase distortion produced in measurement of the DUT. Ideally, the phase
shift of the DUT is linear to the frequency. The deviation produced relative to the theoretical phase deviation is
referred to as the linear phase deviation (also known as the phase linearity). See details in “
8.9 Linear Phase
Deviation
”.
4) Group delay: it is another way to measure the phase distortion of the device. The transition time of the signal of
specific frequency through the device is measured, and the group delay is calculated according to the derivative of
the measured phase response. See details in “
8.5 Group Delay
”.
8.2.5 Linear Phase Deviation and Group Delay
The linear phase deviation and group delay are phase information of the measurement device but for different
purposes.
1) Advantages of linear phase deviation measurement:
a) The noise is lower than that of group delay measurement.
b) The characteristics of the device transmitting phase-modulated signals can be better represented. In this case, it is
more appropriate to use the phase as the unit instead of the second.
2) Advantages of group delay measurement:
a) Compared with the linear phase deviation measurement, phase distortion can be explained more easily.
b) The characteristics of the DUT can be represented accurately. The phase ripple slope is calculated by the
analyzer in group delay measurement and depends on the ripple quantity within the unit frequency. Phase responses
with the same phase ripple peak-peak value are compared. Large phase slope response may result in large group
delay changes and signal distortion.
8.3 Amplifier Parameter Specifications
This section introduces the measurement parameters of the amplifier.
8.3.1 Gain