Session: Session 2

10:20 AM Friday, May 28, 2010

Room: Pacific A
     
Session: Session 2
Nonlinear Measurements
Chair:
Dominique Schreurs, KU Leuven
Abstract:
This session focuses on the measurements of nonlinear and large-signal behaviour in RF power amplifiers used in wireless communications systems. The issues of memory effects, broadband measurements, high-power measurements and load-pull characterization are described.
 
 
Session 2-1
A Simplified Extension of X-parameters to Describe Memory Effects for Wideband Modulated Signals
10:20 AM-10:40 AM
J. Verspecht1, D. E. Root2, J. Horn2, 1Jan Verspecht B.V.B.A., Opwijk, Belgium, 2Agilent Technologies, Santa Rosa, United States
(22)
An original way is presented to model memory effects of microwave amplifiers in the case of wideband modulated signals. The approach is based on X-parameters and can be used to model hard nonlinear behavior. The model can be derived from pulsed envelope X-parameter measurements on an NVNA. The result is a quasi-static nonlinear X-parameter which depends on the probability density function of the input envelope amplitudes. The model predicts RF response to conventional wide-bandwidth communication signals that excite long-term memory effects in power amplifiers. The model is implemented in the ADS circuit envelope simulator.
 
 
Session 2-2
Multi-Harmonic Broadband Measurements using an Large Signal Network Analyzer
10:40 AM-11:00 AM
Y. Ko1, P. Roblin2, S. Myoung3, J. Strahler4, F. D. Groote5, J. P. Teyssier6, 1The Ohio State University, Columbus, United States, 2The Ohio State University, Columbus, United States, 3Samsung Corporation, Suwon, Republic of Korea, 4Andrew Corporation, Westervile, United States, 5Verspecht-Teyssier-DeGroote s.a.s., Brive-la-Gaillarde, France, 6XLIM Limoges University, Brive, France
(40)
A new testbed was developed with an LSNA to perform multi-harmonic broadband measurements for periodically modulated signals whose bandwidth exceeds the IF bandwidth of the LSNA. This testbed is intended for characterizing PAs using multitone signals approximating the CCDF and PAPR of digitally modulated signals. Using this testbed, the nonlinear response of a 80W Doherty GaN power amplifier (PA) at 2.16GHz was characterized for a 13 tones 15MHz multitone excitation with PAPR of 6dB. The inband signal distortion and spectral regrowth was then recorded over an 80MHz bandwidth (63 tones) at both the fundamental and second harmonic. This bandwidth maps the response of the PA in 3rd and 5th order intermodulation bands at the fundamental frequency. These vector measurements provide valuable information for PA optimization and the development and verification of multi-harmonic behavioral models for modulated signals.
 
 
Session 2-3
A VNA based broadband loadpull for non-parametric 2-port Best Linear Approximation Modelling
11:00 AM-11:20 AM
Y. Rolain, J. Schoukens, R. Pintelon, L. Delocht, G. Vandersteen, Vrije Universiteit Brussel (VUB), Brussel, Belgium
(18)
In this paper the Best Linear Approximation (BLA) of a full 2-port nonlinear dynamic system is extracted under broadband load-pull conditions. Starting from a series of VNA Measurements and broadband multisine excitations at both ports, the frequency response function, the covariance matrix of the output noise, and the covariance matrix of the output nonlinear distortions are estimated as a function of the frequency. Using well designed periodic excitations signals, these results are obtained with limited user interaction, making the method accessible for practioning engineers.
 
 
Session 2-4
An Intelligence Driven Active Loadpull System
11:20 AM-11:40 AM
R. S. Saini, S. P. Woodington, J. Lees, J. Benedikt, P. J. Tasker, Cardiff University, Cardiff, United Kingdom
(28)
This paper describes how the application of the PHD model can add intelligence to an open loop active loadpull system. This intelligence driven approach by providing for an improved prediction of the operating conditions required to emulate a specified load speeds up the load emulation convergence process by minimizing the number of iterations to predict the injected signal, therefore making more efficient use of a measurement system. The results were validated by carrying out loadpull measurements on the fundamental tone of a 10x75um GaAs HEMT, operating at 3 GHz.
 
 
Session 2-5
Investigation of X-Parameters Measurements on a 100 W Doherty Power Amplifier
11:40 AM-12:00 AM
J. Wood, G. Collins, Freescale Semiconductor, Inc., Tempe, United States
(42)
In this article we describe a high-power reflectometer set-up specifically designed for large-signal nVNA measurements for the extraction of X-parameters. The heart of the measurement set-up is a Agilent N5242A PNA-X in nVNA mode. We have measured a Doherty amplifier constructed from a 2-stage, dual-path RF power amplifier IC. This power amplifier can deliver in excess of 100 W in Doherty mode, and these measurements represent the highest power X-parameter extraction reported to date.
 
 
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