Should I choose which type of mixer?

[healthy]

I need to design mixers for GPS receiver, the requests are as below:
The first stage:
gain:18dB, NF:9dB, 1dB point:-16dBm, RF-LO and LO-IF isolation:45dB, RF-IF:75dB

The second stage:
gain:27dB, NF:5dB, RF-LO and LO-IF isolation:45dB, RF-IF:75dB

The third stage:
gain:75dB, NF:3dB, RF-LO and LO-IF isolation:45dB, RF-IF:75dB

Should I choose which type of mixer?Gilbert mixer?The three mixers don`t need to be the same.

Thank you for your answers!

 

[psmon]

Mixer noise figure 3 or 5 dB??? Even 9 dB is hard...

 

[hermit2003]

the first specification is reasonable, and u should choose the gilbert cell for the isolation required.

 

[springf2000]

i think y can add a IF SAW filter and y can choose a mixer from the minicircuit