power requirement of LO in LNB

hello,
i need to determine the LO power in an LNB. i have the following values:
received power=-117 dBW; poise power -128dBw; Noise figure of LNB=1dB; LNA gain=50dB.

How can i use these info to relate the LO power.

thanks in advance

Reza

No relationship. Mixer LO power is a function of the mixer design. If it is totally pasive mixer, the LO power will be a function of desired signal handling capability.

a side, LNA gain of 50 db is very high. If you are able to keep it stable you will likely have other issue with larger nearby frequency signals overloading mixer.

You are better off getting gain after the mixer where you can reduce the bandwidth, thereby eliminating other unwanted signals before amplifing them.