A Simple Method for the Measurement of the Phase and Power of 3rd-Order Inter-Modulation Components of the Output of Multi-Stage Power Amplifiers

Toshifumi NAKATANI
Koichi OGAWA

IEICE TRANSACTIONS on Electronics   Vol.E87-C    No.5    pp.749-761
Publication Date: 2004/05/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Advances in Characterization and Measurement Technologies for Microwave and Millimeter-Wave Materials, Devices and Circuits)
Category: Active Devices and Circuits
3rd-order inter-modulation distortion,  phase of IM3 signal,  dissipation power,  vector signal analyzer,  multi-stage cascaded power amplifier,  Volterra series,  asymmetry of IM3 sidebands,  

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A simple method has been proposed for the measurement of the output power and phase characteristics of the 3rd-order inter-modulation distortion (IM3) components appearing in multistage power amplifiers. By adopting a unique definition of the phase for the IM3 components that is independent of the delay time caused by transmission lines and other instrument devices, it is possible to measure the phase, merely by using a vector signal analyzer. It is demonstrated that an accurate estimation of the IM3 characteristics of two-stage cascaded power amplifiers for cellular radio handheld terminals can be made by using the IM3 characteristics of the 1st and 2nd-stage amplifiers as measured by the proposed method. The results indicate that it is possible to reduce the dissipation power by 18% at 28 dBm RF output power with respect to conventional measurement methods. Further studies show that the error in the resultant vector of the estimated IM3 is less than 1 dB, when the asymmetry characteristics of the IM3 sidebands in the 2nd-stage amplifier are less than 7.3%.