MESFET Bias at high frequencies.

I am using NE1235 as a mixer.First I want to ask why for such high frequency devices the output curves of drain current vs drain to source voltage are not specified.Then how can I select my values for drain current and gate and drain voltages?Getting a good gain is more important for me then Noise Figure.
I wonder how they specified the S-Parameters.S parameters are usually specified in Common Source configuration with gate as Port 1 and drain as Port 2.So in this case should one gate be shorted?

The first and the most important parameter of ANY RF mixer is the Linearity, second is the Noise Figure, and third is the Gain.

S-parameters are measured with respect to source terminals (normally 2) ,connected to ground.

Gate terminal wrt source terminal is port 1 or input port
Drain terminal writ source terminal is port 2 or output port,