Rf Power Measurement; Low Frequency Method; High Frequency Method; Figure 4-1 Low Frequency Power Measurement - Keysight V3500A User Manual

RF power measurement

Low frequency method

High frequency method

V3500A User's Guide
At low frequencies, power delivered from an AC source to a
load can be measured with an AC voltmeter connected
across the load terminals (see
provides a high enough input resistance that at low
frequencies, the effective value of load resistance is not
changed.
Signal
source

Figure 4-1 Low frequency power measurement

At high frequencies, the low frequency measurement
technique produces inaccurate readings. To produce reliable
results, a different method is required.
Inaccurate readings could be caused by parasitic capacitance
in low frequency method. Parasitic capacitance causes the
impedance of the shunt voltmeter to decrease, thereby
behaving unpredictably with frequency.
The high frequency method replaces the AC Voltmeter (as
Low frequency
described in the
meter (the RF power meter has an internal, known load
RF Measurement Basics
Figure 4- 1). The voltmeter
R AC
Voltmeter
method) with an RF power
4
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