Modeling and Digital Predistortion based on Zernike polynomial functions for LTE-RoF system

A novel modeling technique is proposed to improve the Radio over Fiber (RoF) modeling and the Predistorter identification. This method is based on an orthogonal basis composed by Zernike polynomials, whose features guarantee numerical stability, a problem present in the classical polynomial model based on Volterra series. The measurements have been carried out with a LTE downlink signal with a bandwith of 3 MHz and QPSK modulation. The DFB laser has been biasing with 40, 70 and 100 mA to compare the distortion effects in each case. The measurements confirm that the RoF and PA modeling has an important improvement in terms of the ACEPR. In order to the DPD, the results show that the new technique reach an improvement of 2.57 dB in order to the ACPR, as well as an increase in the channel power.