Question
How do you optimize the ADL5511 layout for best return losses?
Answer
Follow the layout of the evaluation board, i.e. locate the external shunt
resistor as close as possible to the AC-coupling capacitor and locate that cap
as close as possible to the device. The 75 Ohm shunt resistor combines with the
internal input impedance to provide 50 Ohm match across a wide bandwidth. If
your application is narrow band, you could experiment with the size of this
resistor to see if you can improve the return loss at your operating frequency.
You could also experiment with an active match using inductors and
capacitors.