PCB Design Guidelines (HSSI, EMIF, MIPI, True Differential, PDN) User Guide: Agilex™ 5 FPGAs and SoCs
4.7.5.1. ADM/F Connectors
Use AcceleRate HD High-Density (ADM/F) series connectors to connect the SoM and carrier board. The ADM/F connectors supports signal data rates over 20 Gbps. Obtain a 3D model from the connector vendor and conduct a 3D simulation to optimize the breakout area according to your specific PCB stack-up. Aim to reduce the return loss to lower than -15 dB at the Nyquist frequency (achieving lower than -20 dB is preferable) and keep the impedance variation of the cut-out area as minimal as possible (ideally within ±5 Ω).
The following figure displays a 90 Ω Layer 3 ADM connector breakout structure utilized on the SoM solely for simulation reference. For optimal performance, consider adopting a similar cut-out shape and adjust the size of the cut-out in your simulation structure based on your PCB stack-up.