Passive Diode Mixer Port Impedances

Hello!

How can I calculate the embedding impedances of a ring diode mixer to get VSWR close to 1 for all the RF, LO, IF ports? If I match the RF port and then trying to match IF port, the RF port becomes mismatched...

If the ring diode mixer use two proper baluns transformers, this will provide a relative wideband 50 ohm input/output impedance (better than -10dB return loss) and do not require any additional matching (up to one decade).
If the mixer use printed baluns, the bandwidth is smaller (up to one octave).
In either cases can use additional matching networks to improve VSWR but you get the problems that you mentioned, mostly due to the limited isolation between ports.

Thanks for reply. Can you suggest a book or paper with design equations for input impedance of a diode ring mixer?

Microwave Mixers by Stephen Maas