Packaging of PIN Photodiode on Patch Antenna for a Dual-Mode Indoor RF/FSO Receiver

This paper reports the design, packaging and characterization of a miniaturized dual-mode radio-frequency (RF)/free space optical (FSO) indoor wireless receiver module. Two different patch antennas are designed and integrated with bare die photodiodes together with transimpedance amplifier (TIA) circuits on a printed circuit board (PCB). Ansoft HFSS is used to predict the coupling from RF to FSO link. Measurement results verify that optical link degradation is minimized with the specially designed patch structure. FSO link operation at 2 Gb/s in a 10 GHz RF environment is achieved. Through the comparison to previously developed RF/FSO modules, the new receiver boards demonstrate reduced RF-to-optical cross channel coupling, and increased gain and antenna radiation efficiency.