VHDL-AMS subset for HB simulation

This report shows that there is limited subset of VHDL-AMS, which is sufficient to describe pure analog circuits and to propose a simple VHDL-AMS extension to get the advantages of frequency-domain modeling and simulation. That makes possible the usage of the described VHDL-AMS subset as modeling language for the harmonic balance simulator. It allows description of nonlinear dynamic behavior in the time domain, corresponding to nonlinear integro-differential equations. To extend language capabilities, an additional attribute is proposed, which represents the image of a certain quantity in the frequency domain.