Linear RF power amplifier design for MIRS M-16-QAM signals: A spectrum analysis approach

Abstract

SINCE quadrature amplitude modulation (QAM) was discovered in the early 1960s, more and more research (e.g. [1,2,3,4,5]) has been done on extracting more bandwidth and power efficiencies with QAM. Coded modulation, which combines modulation and coding, has been accepted as a more efficient transmission scheme in [2]. Multilevel coding (MLC), a coded modulation scheme proposed by ImailHirakawa in 1977, together with multistage decoding (MSD) has been known to be optimum in the sense of channel capacity over the A WGN channel model (see [1, 7, 8]). However, over Rayleigh fading channels Bit-Interleaved Coded Modulation (BICM), which was originally proposed by Zehavi.[4], gains much better performance [9, 10].One of the critical and costly components in digital cellular communication systems is the RF power amplifier.Theoretically, one of the main concerns in an RF power amplifier design is the nonlinear effect of the amplifier.Quantitatively, so far, no explicit relationship or expression currently exists between the out-of-band emission level and the nonlinearity description related to the third-order intercept point (IP3). Further, in experiments and analysis, it was discovered that, in some situations, using IP3 only is not accurate enough to describe the spectrum regrowth, especially when the fifth-order intercept point (IPS) is relatively significant compared to the third-order intermodulation. In this article, we analyze the nonlinear effect of an RF power amplifier in the MIRS M-16-QAM system, give an expression of the estimation of the out-of-band emission levels for an MIRS signal power spectrum in terms of the IP3 and the IPS, as well as the power level of the signal. This result will be useful in the design of RF power amplifier for the MIRS M-16-QAM system and other wireless communication systems.In this paper, we present a hybrid mixed cost-function adaptive initialization algorithm for the time domain equalizer in a discrete multitone (DMT)-based asymmetric digital subscriber loop. Using our approach, a higher convergence rate than that of the commonly used least-mean square algorithm is obtained, whilst attaining bit rates close to the optimum maximum shortening SNR and the upper bound SNR. Moreover, our proposed method outperforms the minimum mean-squared error design for a range of TEQ filter lengths. 0-7803-7402-9/02/$17.00 @2002 IEEE IV -4183