At ECOSat, we do all our own electronics design, RF included. The granddaddy of all RF design suites is Keysight’s Advanced Design System (you’ll find Keysight on our sponsors page). ADS is an extremely powerful tool, but using it can be daunting for a novice.
The first thing you need in an RF design is some fundamental analog devices: transistors and diodes. ADS comes with a library already, but it’s not incredibly comprehensive. Many vendors offer ADS-specific models for their devices, but others may only provide a SPICE model. These SPICE models are normally a device model embedded in a subcircuit that also accounts for parasitic effects. Ensuring these parasitics are imported is crucial for RF design.
It turns out you can translate SPICE models for use in ADS simulations, but the process is a little convoluted. Here’s a quick guide.