Active wide band mixer without a buffer

Hi, I am designing active wide band mixer. problem is buffer degraded performance
possimulation without buffer is quit good result but when adding buffer doesn't gives that result, which was without buffer

is there some way to measure without using buffer?

can some one help?

thank you in advance

If you want a qualified answer, please indicate important information.
'Active" mixers can have buffer amplifiers in LO input, then they can operate with a low LO input. Other "active" mixers have buffers in RF output, in IF output, etc.
If you simulate such mixer, then how the buffer can be degraded? If you measure a real mixer, then replace the buffer.
Notice all specifications, and meet them.

I simulate mixer without buffer NF is 3.6dB@1~50MHz and when I add buffer NF is 4.5dB.
possimulation without buffer shows expected result but when i add buffer noise increases 9dB@1~8MHz
and 5dB NF @ 10~50MHz.

I am still missing relevant information. Is your buffer in the LO line, or elsewhere? What is mixer structure?
I prefer trying real devices, modeling is a toy for lazy guys. And more, they even do not know how it works...

My MIXER is Active Mixer and buffer is on IF line not LO...
input is RF and LO, output is IF
input RF signal 0.7~3GHz
output IF signal 1~50MHz

that maybe caused by the noise figure of your buffer. Try to use low noise buffer, such as LNA.