Joint Linearization for Radio-over-Fiber Links Equipped with High Power Amplifiers

In this study, we experimentally investigated the adjacent channel leakage ratio (ACLR) performance degradation for the output signal of the RF HPA equipped with the adaptive linearization caused by RoF links placed in both direct and feedback paths of the transmitting system. We show that ACLR exceeding -57 dBc @ 5 MHz offset, which completely satisfy the requirement defined in the 3GPP technical specification, can be achieved for a 20 W class Doherty power amplifier linearized through 1 km fiber with commercial RoF links. With the experimental results, we show that the achieved ACLR strongly depends on the RoF link noise figure; meanwhile most of the nonlinear distortions caused by RoF can be successively suppressed with the proposed joint linearization approach.