Power amplifiers used in modern wireless systems need to efficiently transmit signals, without distortion, that have complex envelopes with variable phase and amplitude. The design of these power amplifiers require that transistors are characterized under complex excitations into variable load impedances, so that determination of perfect matching conditions for optimum performance is achieved. This paper presents a new active load pull system design, based on the envelope load-pull concept, which can provide for the required load-pull capability under high modulation rate multi-tone excitations. This performance is realized by incorporating analogue controlled delay elements into the envelope feedback loop to compensate for the inherent group delay encountered in the feedback loop. Measurements on a ldquoThrurdquo using this active load-pull system have demonstrated that it can provide constant, drive independent control of load impedances for multi-tone characterization of transistors and power amplifiers used in wireless communication systems such as GSM-EDGE.
[1]
R.B. Stancliff,et al.
Harmonic Load-Pull
,
1979,
1979 IEEE MTT-S International Microwave Symposium Digest.
[2]
M. Spirito,et al.
Base-band impedance control and calibration for on-wafer linearity measurements
,
2004,
ARFTG 63rd Conference, Spring 2004.
[3]
J. Benedikt,et al.
Application of a novel active envelope load pull architecture in large signal device characterization
,
2005,
2005 European Microwave Conference.
[4]
J. Benedikt,et al.
Active Envelope Load-Pull for Wideband Multi-tone Stimulus Incorporating Delay Compensation
,
2008,
2008 38th European Microwave Conference.
[5]
Umberto Pisani,et al.
Active load technique for load-pull characterisation at microwave frequencies
,
1982
.
[6]
Y. Takayama.
A New Load-Pull Characterization Method for Microwave Power Transistors
,
1976
.