how open stubs improves mixer's convesion loss?

[klp]

Hi, I have designed this mixer:

the open stubes C and D calculated for lenght of quarter lambda for LO and RF frequencies.
I would like to ask, why does the open stubs (C,D) improves the conversion loss?
conversion loss=Pif[output power]-Prf[input power]
I mean the Prf does not changes since it is the RF input power (let assume -15dBm).
so why does the conversion loss improves because of C,D open stubs?
Is Pif increased because of the stubs? if yes, why?
thanks alot.

 

[RCinFLA]

Provides a low impedance at RF and LO frequencies to improved performance.

Any RF or LO signal at IF output degenerates mixer diode operation.

Open stub rotates to a short at quarter wavelength. At lower IF frequency the open stub is just capacitance that is part of the output low pass filter section.

 

[biff44]

i would not try actually USING that circuit at above, say, 2 GHz.

the "stubs", as you call them, keep LO and RF power from leaking out the IF port.