RFSim99 is a free linear S-parameter based circuit simulator offering schematic capture, simulation, 1 port and 2 port S-parameter display and file support, tolerance analysis, stability circles, and much more. Requires Windows 95, 98, NT or 2000. File size 2045K
Download: RFsim99-Win7/ Win8
Download the file, un-zipped with Winrar ( Download Winrar) , use the software directly.