Compact E-Band (71-86 GHz) bias-tee module for external biasing of millimeter wave photodiodes

This paper focuses on the development and characterization of a novel E-band planar bias-tee (BT) circuit featuring a high-speed millimeter wave photodiode (mm-wave PD) module to be integrated in next generation access and mobile networks (5G). The designed bias-tee circuit together with the integrated mm-wave PD chip, i.e., triple transit region photodiode (TTR-PD) allows the development of high-power Radio-over-Fiber (RoF) E-band (70/80 GHz) photonic transmitters (PTs) to be used in wireless extension and mobile backhaul links. The introduced BT circuit provides the protection to the hybrid integrated RF amplifier from being damaged by the PD bias voltage and prevents the leakage of the RF signal through the DC path. The vector network analyzer (VNA) measurements of the BT circuit show that in the frequency range from 70 to 75 GHz, the return loss (RL) is higher than 11 dB, the RF signal suppression level (IS) in the DC path is higher than 30 dB, while the insertion loss (IL) is lower than 2 dB. For optical RF signal generation, two laser sources are used to generate an optical heterodyne signal. Lower dark current levels and a 3-dB bandwidth in the frequency range from 71 to 86 GHz have been demonstrated at the BT output.