Simulating a Gilbert Cell in Microwave Office

I'm simulating a Gilbert Cell in Microwave Office but I'm not getting the desired output waveforms.

My waveforms look like this

but I'm trying to get them to look like this

I'm sure it has got to do with the way the transistors are biased but I'm not sure what resistor values to adjust. Heres my schematic. I tried attaching the *.emp file but it's not a valid extension.

Any help would be appreciated

Many thanks