Title :
Performance of a new digital baseband predistorter using calibration memory
Author :
de Mingo, J. ; Valdovinos, A.
Author_Institution :
Dept. de Ingenieria Electron. y Comunicaciones, Zaragoza Univ., Spain
fDate :
7/1/2001 12:00:00 AM
Abstract :
Digital predistortion of a baseband signal is a well-known method of power amplifier (PA) linearization used to reduce adjacent channel interference (ACI) in a nonconstant envelope modulation system. This paper proposes a specific predistorter configuration based on the estimation of the PA characteristics extracting its linear behavior and comparing with a linear model by means of a calibrating signal. The effects of quadrature modulator and demodulator imbalances are included in our analysis. The effects and requirements of the reconstruction filters are stated and a new method for the loop delay estimation is presented. We also focus our attention in some design considerations and simulation results related to the use of a fixed point digital signal processor (DSP). Simulations show that out-of-band skirts lower than -60 dBc can be obtained for a narrow bandwidth system
Keywords :
adjacent channel interference; calibration; delay estimation; demodulators; digital radio; filtering theory; fixed point arithmetic; interference suppression; linearisation techniques; modulators; power amplifiers; radiofrequency amplifiers; signal processing; signal reconstruction; IF filters; adjacent channel interference reduction; baseband signal; calibrating signal; calibration memory; digital baseband predistorter; digital signal processor; fixed DSP; linear model; lookup tables; loop delay estimation; narrow bandwidth system; nonconstant envelope modulation system; out-of-band skirts; performance; power amplifier linearization; quadrature demodulator imbalance; quadrature modulator imbalance; radio communications services; reconstruction filters; simulation results; Baseband; Delay estimation; Demodulation; Digital modulation; Filters; Interchannel interference; Power amplifiers; Power system modeling; Predistortion; Signal design;
Journal_Title :
Vehicular Technology, IEEE Transactions on