Is there a way to model AD831? Should I download ADIsimRF or ADIsimPLL?
AD831 is an older part so it does not have a device model in ADIsimRF. However, you could use the datasheet data to create a custom model for the device. Instructions on how to do this are contained in the main Help menu.
I'm not sure what frequency range you are operating at but for a new design, there are many newer better devices available. Take a look at ADL5801 for example.
After your first answer i managed to look them up. My biggest concern is about transmitting (i hope it is a correct for it) low frequency. Here is what i want to do: in the first stage i'd like to mix 130 MHz and 1 kHz signal, then in the latter part i want to demodulate this signal.