Photonic Generation of High Fidelity RF Sources for Mobile Communications

A novel technique for generating RF sources for mobile communications based on dual Mach–Zehnder modulators and high-power charge-compensated modified unitraveling carrier (CC-MUTC) photodiodes is presented. A system model is developed and used to establish and mitigate nonlinearities attributed to its constituent components, i.e., waveform generators, amplifiers, modulators, and photodiodes. In particular, digital predistortion is used to improve source linearity. Extensive experiments are conducted to characterize the proposed system, using a commercial 5 MHz local thermal equilibrium signal. Optimal results are achieved with a CC-MUTC photodiode to attain an RF power greater than 12.5 dBm and an adjacent channel leakage ratio lower than −63.5 dBc.