Leonardo Flores Hernández, José Ricardo Cárdenas Valdez, Jose Alejandro Galaviz Aguilar


In this work, a linearization scheme for QPSK and 64-QAM type digital modulation developed in an RF transceiver is presented. The modeling stage is based on a polynomial memory model with flexible memory depth and non-linearity order. In addition, an indirect learning approach (ILA) scheme is adapted for spectral correction. In this case, a sweep is performed to characterize the commercial RF power amplifier of the AD9316. Experimental results are presented to validate the QPSK with a carrier frequency of 2.4 GHz with a bandwidth of 18 MHz, and for a 64-QAM multiplexed by LTE with a bandwidth of 2.7 MHz. The improvement of the spectral growth of 8 dB for a QPSK signal of 18 MHz and it is demonstrated that it worsens by 2 dB due to the non-linear behavior of the amplifier for an LTE signal with a bandwidth of 2.7 MHz. The developed system is applicable for base stations of femtocells, picocells, and microcells. It represents the starting point of a digital predistortion (DPD) system for medium and high-power RF-PA.
Keywords: 64-QAM, LTE, QPSK, RF-PAs, transceiver.

En este trabajo se presenta un esquema de linealización para modulación digital tipo QPSK y 64-QAM desarrollado en un transceptor de RF. La etapa de modelado se basa en un modelo polinomial de memoria con profundidad de memoria flexible y orden de no linealidad, además se adapta un esquema de enfoque de aprendizaje indirecto (ILA) para la corrección espectral. En este caso, se realiza un barrido para caracterizar el amplificador de potencia de RF comercial del AD9316. Se presentan resultados experimentales para validar el QPSK con una frecuencia portadora de 2.4 GHz con un ancho de banda de 18 MHz, y para un 64-QAM multiplexado por LTE con un ancho de banda de 2.7 MHz. Se logra la mejora del recrecimiento espectral de 8 dB para una señal QPSK de 18 MHz y se demuestra como empeora en 2 dB debido al comportamiento no lineal del amplificador para una señal LTE con un ancho de banda de 2.7 MHz. El sistema desarrollado es aplicable para estaciones base de femtocélulas, picocélulas y microcélulas y representa el punto de partida de un sistema de predistorsión digital (DPD) para RF-PA de potencia media y alta.
Palabras Clave: 64-QAM, LTE, QPSK, RF-PAs, transceptor.

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