Spectrum Emission Considerations for

Linear transmitters based on combined analog locked loop universal modulator (CALLUM) architectures are attractive, as they promise both high efficiency and high linearity. To date, it has not been possible to analyze a CALLUM trans- mitter as a linear feedback network due to the nonlinear nature of the control equations governing it. The main purpose of this paper has been the derivation of a linearized model for the control equa- tions, which enables the use of linear network theory in the study of CALLUM. In particular, it can be used to analyze the stability and maximize the bandwidth of the system. Simulation examples are presented on how three different CALLUM architectures behave for enhanced data rates for global system for mobile communications evolution and wide-band code-division multiple-access signals. In addition, we have consid- ered the effects of loop time delay, which is the ultimate limiting factor for all feedback-based linear transmitter architectures, par- ticularly for large bandwidths. Finally, it is shown how frequency compensation of the feedback loop improves insensitivity to the loop time delay.

[1]  S.C. Gupta,et al.  Phase-locked loops , 1975, Proceedings of the IEEE.

[2]  Lars Sundström,et al.  A complex polynomial predistorter chip in CMOS for baseband or IF linearization of RF power amplifiers , 1999, ISCAS'99. Proceedings of the 1999 IEEE International Symposium on Circuits and Systems VLSI (Cat. No.99CH36349).

[3]  F. Raab,et al.  Power amplifiers and transmitters for RF and microwave , 2002 .

[4]  Fernando Casadevall,et al.  Performance analysis of QAM modulations applied to the LINC transmitter , 1993 .

[5]  David R. Cox,et al.  Linear Amplification with Nonlinear Components , 1974, IEEE Trans. Commun..

[6]  A. Bateman,et al.  Linear modulators based on RF synthesis: realization and analysis , 1995 .

[7]  Pietro Andreani,et al.  Bandwidth considerations for a CALLUM transmitter architecture , 2002, 2002 IEEE International Symposium on Circuits and Systems. Proceedings (Cat. No.02CH37353).

[8]  J. P. McGeehan,et al.  A high-efficiency RF transmitter using VCO-derived synthesis: CALLUM , 1999 .

[9]  J. D. Marvill,et al.  The design of highly linear broadband power amplifiers , 1991 .

[10]  E. H. Nordholt.  Design of High-Performance Negative-Feedback Amplifiers , 1980 .

[11]  A. Bateman,et al.  Adjacent channel power and error-vector magnitude performance of reduced complexity CALLUM systems , 1999 .

[12]  M. Johansson,et al.  Transmitter linearization using Cartesian feedback for linear TDMA modulation , 1991, [1991 Proceedings] 41st IEEE Vehicular Technology Conference.

[13]  M. Faulkner,et al.  Stability analysis of Cartesian feedback linearisation for amplifiers with weak nonlinearities , 1996 .