2010 IEEE MTT-S International Microwave Symposium Technical Program

Session: TH1C	Large Signal Measurements
Chair:	Nuno Borges Carvalho, Universidade de Aveiro
Co-Chair:	Kate A. Remley, NIST
Abstract:	This session treats recent advances in load pull and active device measurements.

TH1C-1	A novel methodology for fast harmonic-load control with a passive tuner and an active loop
8:00 AM-8:20 AM	S. Bonino, V. Teppati, A. Ferrero, Politecnico di Torino, Torino, Italy
(1224)	In this paper we introduce a novel technique to overcome the drawbacks of passive tuners and active loops when characterizing very high power transistors and amplifiers. The methodology combines a passive tuner and an active loop, the former used to tune the fundamental output impedance of a device under test, the latter exploited to change its harmonic termination. Since the passive tuner changes also the harmonic load in an unpredictable way, we present for the first time a method to quickly find the correct settings for the active loop to achieve the desired harmonic load. This methodology, is easy to implement, relatively quick, and does not imply long system pre-calibration time when changing the characterization frequency.

TH1C-2	A Low-Cost and Accurate Technique for the Prediction of Load-Pull Contours
8:20 AM-8:40 AM	V. Vadalà, A. Raffo, S. Di Falco, G. Vannini, University of Ferrara, Ferrara, Italy
(1307)	Load-pull measurement systems are the most common and powerful instruments used for the design of power amplifiers.They allow to directly obtain output power,efficiency and gain contours which give a clear idea of the electron device optimum termination for the selected operation.Nevertheless,such measurement systems are also very expensive,especially if high frequencies and high power levels are addressed.In this paper,a new technique for drawing load-pull contours is presented which jointly exploits both large-signal low-frequency I/V device measurements and a nonlinear capacitance-based model,the latter one being obtained on the bases of bias- and frequency-dependent small-signal S-parameters.The proposed approach achieves the same level of accuracy of high-frequency measurement systems,using general purpose instrumentation available in microwave laboratories.Different experimental examples,based on power GaN FETs,are provided to demonstrate the validity of the described technique.

TH1C-3	Active Simultaneous Harmonic Source and Load Pull Assisted by Local Polyharmonic Distortion Models
8:40 AM-9:00 AM	R. E. Leoni III, S. A. Harris, D. G. Ries Jr., Raytheon Company, Andover, United States
(1587)	The efficiency of a power amplifier is a strong function of the core transistor technology and the circuitry that is wrapped around it. There are many theoretical approaches to obtaining full DC-to-RF conversion from an ideal transistor, however real-world technologies do not perform equally well with each. The parasitic reactances and non-ideal DC characteristics of a transistor technology result in matching and bias requirements that can deviate significantly from those of ideal theory. In this paper we describe the use of an active simultaneous source and load pull system that quickly ascertains the conditions required to achieve a transistor technology's peak efficiency performance. The speed with which the system is able to achieve these results is facilitated by local polyharmonic distortion models that provide a quick and reliable method for finding the path of steepest ascent.

TH1C-4	A Method to Select Correct Stimuli Levels for S-functions Behavioral Model Extraction
9:00 AM-9:20 AM	M. Myslinski¹, F. Verbeyst², M. Vanden Bossche², D. Schreurs¹, ¹K.U.Leuven, Leuven, Belgium, ²NMDG n.v., Bornem, Belgium
(1273)	S-functions and other frequency-domain behavioral models based on describing functions rely on the linearization of the response of a nonlinear RF or microwave component around a set of large-signal operating points. To assure the validity of the linearization principle, and thus the validity of the model, one has to select appropriate stimuli levels during the experiments which are performed to extract the model parameters. In this work we propose a formal procedure to identify the correct small-signal power levels using a system identification approach, i.e. taking the uncertainty of the measured data into account. The method is based on the analysis of the cost function of an errors-in-variables (EIV) estimator obtained for simple models.

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