Adaptive digital corrector for dual-band data transmission system under quadrature distortions

The digital compensation process for nonlinearly inertial characteristic of the transmit path of dual-band communication system with concurrent data transmission in the presence of unbalance of modulator quadratures has been considered. Analytical relationships enabling us to identify adaptively or change the parameters of dual-band polynomial model of corrector with due regard for the modulator quadrature distortions caused by the LMS, RLS and conjugate gradient algorithms are derived. A model of corrector based on the neural network representing a multilayer perceptron was built for the system. Experimental comparative analysis of the linearization efficiency of link with 25 W power amplifier using correctors with polynomial and neural network architecture is carried out. A comparative analysis of convergence speed, computational complexity and the linearization efficiency of adaptive algorithms (LMS, RLS and conjugate gradient algorithm) based on the polynomial architecture has been performed. The signals using 16QAM modulation with bandwidth of 4 MHz and frequency tune-out of 16 MHz are used as test signals. The results of experimental analysis show the highest computational efficiency without any loss of linearization quality of polynomial compensator that is identified by the conjugate gradient algorithm.