Mixer impedance matching

[Hetfield]

hello everyone
im trying to matching my mixer to the 50 ohm and for matching i adding resistors to the cell but when i do this linearity is decreasing substantially why this is like that and how to i avoid this situation
thanks

 

[KlausST]

Hi,

I left my crystal ball in my office, so I can't see what circuit you are talking about.

Klaus

 

[BigBoss]

Adding resistor is not a known Matching Technique.You have drawn your Gilbert Cell in your other topic and using a Buffer to drive lower impedances is a very common way.

 

[RCinFLA]

You are going to have to give more info. What part? Hookup schematic?

Some Gilbert cell mixers have common base input stage which have relatively low input impedance. If the way you hooked up loading resistor also changed device biasing it could explain loss of dynamic range.

 

[dick_freebird]

If you want to match 50 ohms well, at moderate or high
power, you need your active devices to be pretty large.
Gilbert cells I believe are better for small signal, while
FET-quad mixers can be sized (W) to deliver volts into
50 ohms. Bonus, their operation is mostly "on" and "off"
so there is not so much power dissipation in the mixer
unlike a linear circuit.