power levels of mixer output

[gwthmnr]

Hi,
I want to know what will be the theoritical LO output power at the output of mixer.
For IF we have IF power=RF power - Conversion gain, so like that any formula for LO output powerr at mixer output.

thank you in advance.....

 

[vfone]

There is no formula for LO power at the mixer output.

This depends mainly by LO-to-IF isolation of the mixer, which depends by the type of the mixer (Single-Device, Single-Balanced, Double-Balanced, etc.) and by the technology used to build the mixer (BJT, FET, CMOS, etc).

 

[jiripolivka]

As mixers are devices mostly utilizing non-linear elements like diodes or transistors, by injecting LO power "pumping", harmonics are generated. Some are mixed with the RF signal or IF signal and harmonic combinations are generated.
By using filters, we select what we want to get from a mixer.
For down converters, a RF band-pass filter defined the input frequency band, and IF band-pass filter defines the IF output band.
In upconverters, we use RF BPF again as well as IF BPF.
The "isolation" between LO and RF port and LO and IF port is achieved by the balanced mixer circuit. Such isolation depends on LO input level and is often low. Then filter design and frequency plan is used to achieve an acceptable isolation.