INTRODUCTION TO VHDL-AMS
the systems of equations is done for a special (fixed) frequency. Figure 6-59
illustrates this approach.
in VHDL-AMS => DOMAIN = FREQUENCY_DOMAIN
Solve a system of differential equations
Solve a system of complex equations
A* x` + B* x = c
x(t) = X cos( t+ )
c(t) = C cos( t+ )
(A*j +B)* X(j ) = C(j )
X(j ) = X*e
Figure 6-59. System with sinusoidal input
What are the consequences of taking into consideration the modeling
requirements? After determination of the operating point the linearization of
the network equations can be done automatically by the simulation engine
(see Table 6-6). That means that in general no special description for
frequency analysis is necessary. The description for frequency analysis can
be derived from the description for time domain analysis. Only AC voltage
and current sources (across and through respectively) that are characterized
by magnitude and phase have to be added to the description for frequency
The AC linear circuit is analyzed over a user-specified range of
frequencies. The frequencies normally start with frequency fstart and step
with a specified number of points per decade to the final frequency fstop
(DEC mode). Alternatively, they step with a specified number of points per
octave to the final frequency fstop (OCT mode) or step with a specified
number of points that are linearly distributed between fstart and fstop.
This AC method was introduced into electrical engineering by Charles
Proteus Steinmetz at the end of the 19th century. For the first time it offered
a widely accepted way to design alternating current electrical equipment
using mathematical methods. The frequency domain representation of a
sinusoid is usually called phasor.
DOMAIN = FREQUENCY_DOMAIN Solve a system of differential equations Solve a system of complex equations A* x` + B* x = c x(t) = X cos( t+ ) c(t) = C cos( t+ ) (A*j +B)* X(j ) = C(j ) X(j ) = X*e j special magnitude phase Ce j Figure 6-59.