A Baseband Time Domain Measurement
System for Dynamic Characterization of
Power Amplifiers with High Dynamic Range
over Large Bandwidths.
Licentiate Thesis, Signals and Systems,
Uppsala University, Dec. 2004.
Licentiate Seminar Friday, Dec. 17 2004 at 10:15.
in room Översten in the
Gävle Technology Park,
In this thesis, a time domain measurement system for
RF signals is discussed. The need for such a system
is established. Impairments due to non-ideal
measurement instruments in the system are discussed
as well as methods to compensate for them.
An alternative method for two-tone sweep measurements,
including measuring the phase of intermodulation products
in addition to the amplitude, is presented.
The proposed method is substantially faster, several
orders of magnitude, than currently used methods,
while having about equal accuracy.
The system is used for input-output measurements
of two power amplifiers and the obtained data are fitted to
different amplified models including memory.
A memoryless model, a Wiener model, a Hammerstein
model and an extended Hammerstein model
are compared with respect to the total model
error and Adjacent Channel Power Ratio (ACPR).
It is found that the Extended
Hammerstein model, as expected, clearly outperforms
the others. It is also found that if the ACPR is of main
interest, a higher model order should be used than if the
total model error is the property of main interest.
A method to simultaneously find the phase and amplitude
ripple of a signal generator and a signal analyser
is also presented.
The method is verified with measurements.