How do I design a DC return path for an AC coupled RF signal line?

Designing a DC return path for an AC-coupled RF signal line provides a DC path to ground for the bias current or static charge on an RF trace that is AC-coupled (blocked by DC-blocking capacitors at one or both ends), preventing the trace from floating to an undefined DC voltage that could cause ESD damage, affect the bias of connected active devices, or charge up and impact the signal integrity. When an RF trace is AC-coupled: the DC-blocking capacitors block any DC current from flowing through the trace, and the trace floats at whatever voltage is imposed by leakage currents, charge accumulation, or the connected device's bias. Without a DC return path: the floating node can charge up to unknown voltages (potentially damaging sensitive inputs), the bias conditions of connected transistors may be affected, and ESD events have no bleed-off path. The DC return path is typically implemented with: a high-value resistor to ground (1-10 kohm) connected from the floating RF trace to the DC ground; the resistor provides a DC path while having minimal effect on the RF signal (at RF frequencies: the resistor's impedance is much higher than the 50-ohm trace impedance, presenting a negligible shunt load). For a 10 kohm resistor in parallel with 50 ohms: the load is approximately 50 x 10000 / (50 + 10000) = 49.75 ohms (negligible effect). Alternative implementations include: using the bias tee (if the trace connects to a biased active device: the bias network already provides a DC return through the RFC inductor), using a quarter-wave stub (a short-circuited quarter-wave stub provides a DC path through the short circuit while presenting an RF open circuit at the operating frequency), and connecting to a device with an inherent DC path (if the device's input or output has a DC path to ground internally).