Linearizability of TWTAs using predistortion techniques

Predistortion linearization is a very effective technique for improving the linearity and efficiency of traveling wave tube (TWT) amplifiers. In this paper, we will study the effectiveness of predistortion techniques for TWT linearization using single-tone, two-tone, and quadrature-amplitude-modulation signals. The results from a series of predistortion linearization experiments for five TWTs covering L-, C-, Ku-, and Ka-bands and including both helix- and coupled-cavity TWTs will be presented. We will demonstrate the additional improvement of fifth-order predistortion linearization over the more commonly used third-order predistortion linearization. To circumvent the complexity and limited availability of a pure fifth-order linearizer, a technique for realizing nonlinear functions of order greater than or equal to five using cascaded third-order nonlinear functions is described. The technique can be used to efficiently generate higher order nonlinearities for predistortion linearization applications. We will demonstrate experimentally that the use of two cascaded third-order functions is comparable to a pure fifth-order implementation in performance.

[1]  B. Levush,et al.  Calibration of a gigahertz-bandwidth vector signal generation and analysis system , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

[2]  John G. Proakis,et al.  Digital Communications , 1983 .

[3]  H. J. Wolkstein,et al.  Predistortion Linearize Using GaAs Dual-Gate MESFET for TWTA and SSPA Used in Satellite Transponders , 1985 .

[4]  Thomas M. Antonsen,et al.  Nonlinear, time-domain analysis of coupled-cavity traveling wave tubes , 2002, Third IEEE International Vacuum Electronics Conference (IEEE Cat. No.02EX524).

[5]  A. S. Gilmour.  Principles of Traveling Wave Tubes , 1994 .

[6]  Allen Katz,et al.  Characteristics and modeling of passive MESFETs for non-linear control applications , 1994, 1994 IEEE MTT-S International Microwave Symposium Digest (Cat. No.94CH3389-4).

[7]  Baruch Levush,et al.  Traveling-wave tube amplifier performance evaluation and design optimization for applications in digital communications with multilevel modulations , 2003 .

[8]  Steve C. Cripps,et al.  Advanced Techniques in RF Power Amplifier Design , 2002 .

[9]  P. B. Kenington.  Methods linearize RF transmitlers and power amps , 1998 .

[10]  Y. Mitsui,et al.  A novel series diode linearizer for mobile radio power amplifiers , 1996, 1996 IEEE MTT-S International Microwave Symposium Digest.

[11]  H. Seidel,et al.  Error-controlled high power linear amplifiers at VHF , 1968 .

[12]  D. R. Whaley,et al.  Design of a linear C-band helix TWT for digital communications experiments using the CHRISTINE suite of large-signal codes , 2002 .

[13]  W. Bosch,et al.  Measurement and simulation of memory effects in predistortion linearizers , 1989 .

[14]  Bumman Kim,et al.  New predistortion linearizer using low-frequency even-order intermodulation components , 2002 .

[15]  Baruch Levush,et al.  Traveling-wave tube devices with nonlinear dielectric elements , 1998 .

[16]  Larry J. Greenstein,et al.  Performance Analysis of Digital Radio Links with Nonlinear Transmit Amplifiers , 1987, IEEE J. Sel. Areas Commun..

[17]  T. M. Antonsen,et al.  CHRISTINE: A Multifrequency Parametric Simulation Code for Traveling Wave Tube Amplifiers. , 1997 .

[18]  Allen Katz,et al.  Passive FET MMIC linearizers for C, X and Ku-band satellite-applications , 1993, IEEE 1993 Microwave and Millimeter-Wave Monolithic Circuits Symposium Digest of Papers.

[19]  Youngoo Yang,et al.  Analog predistortion linearizer for high-power RF amplifiers , 2000, IMS 2000.

[20]  B. Levush,et al.  Application and validation of the helix TWT design code suite , 2002, Third IEEE International Vacuum Electronics Conference (IEEE Cat. No.02EX524).

[21]  David K. Abe,et al.  A comparison of L-band helix TWT experiments with CHRISTINE, a 1-D multifrequency helix TWT code , 2000 .

[22]  A. Katz.  Linearization: reducing distortion in power amplifiers , 2001 .

[23]  Dan M. Goebel,et al.  Development of linear traveling wave tubes for telecommunications applications , 2001 .

[24]  K. Sam Shanmugan,et al.  Simulation of Communication Systems , 1992 .