Why IR placed before amplifier in Heterodyne receiver?

Hi friends,
I want to design Heterodyne receiver:LNA1+amplifier+Mixer. I know IR always placed between LNA and amplifier,but I do not know advantage to do that,why is it not placed between amplifier and Mixer?
Anyone can tell me?
Thanks

You can place the IR between the Amplifier and mixer.
The advantage we get with IR between LNA and amp is IP3 and P1dB requirement for the Amplifier will be lower. Inn your case you need the amplifier really a power amplifier 1/8th to 1/4 watt range.
That's how the system designer will chose the IR between the LNA and Amplifier