It looks like the output power is about +13dBm for an input power of +4dBm. What if I use an input power of about (for eg) -5dBm? Is there a conversion gain plot or something available?
There is no conversion gain plot available. The typical input power is 0 - 6dBm with a maximum drive level of +10dBm. Use of lower drive levels may result in performance degradation so I would encourage you to test several devices over supply and temperature variation to be sure that the performance will be adequate for your application.
The problem is that I can't directly measure the output of this module; I use it as an up-converter and signal source (80GHz) for driving a custom mixer under test.
I would like to drive my mixer with various power levels for e.g. -10bBm to +10dBm.
You'll need to characterize this yourself as it sounds like you're using this to characterize an E-band mixer. We do offer E band VGA's (HMC8120 & HMC8121). Perhaps these will help.
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