A Compact Avalanche Photodiode Package With Enhanced EMI Immunity

This letter presents a compact avalanche photodiode (APD) package designed to suppress electromagnetic interference (EMI) using a vertically stacked RC filter and orthogonal wire bonding. Conventional TO packages typically exhibit less than 5 dB of rejection at 1 GHz due to significant lens-aperture RF leakage. The proposed package integrates a high-voltage decoupling capacitor directly beneath the APD and a stacked bias filter, forming a differential loop that cancels RF signals leaked through the lens aperture. Implemented in a TO-style housing, the structure reduces parasitic interconnect length and improves mechanical stability. Experimental results demonstrate over 25 dB of rejection for common‑mode RF interference across the 100 MHz to 2 GHz frequency range, with suppression exceeding 30 dB at 1 GHz. In addition, the package achieves a 3-dB improvement in signal-to-noise ratio (SNR) under realistic 1-GHz Wi-Fi interference, making it suitable for 5G optical receivers and other EMI-sensitive optical communication systems. Future work will extend the design to multi-band EMI modeling and long-term reliability validation. This work presents a robust solution for enhancing the sensitivity and reliability of optical receivers in high-EMI environments.