Environmental Engineering Reference
In-Depth Information
Chapter 12
FREQUENCY DOMAIN ANALYSIS OF
PERIODICALLY SWITCHED
NONLINEAR CIRCUITS
The steady-state response of a nonlinear time-invariant circuit to a
sinusoidal input contains both the frequency of the sinusoidal input and
its harmonics. When two sinusoids of different frequencies are applied
to the circuit simultaneously, intermodulation frequency components are
generated. It was shown in Chapter 11 that due to the periodic switch-
ing, the response of periodically switched linear circuits to a single-tone
input at contains frequency components at both the baseband fre-
quency and the sideband frequencies When
the nonlinear characteristics of the devices of these circuits are consid-
ered, these circuits are subject to the effects of both the nonlinearities,
which give rise to harmonic and intermodulation components, and pe-
riodic switching, which generates sideband frequency components. This
substantially increases both the number of the frequency components in
the response of these circuits and the complexity of the analysis of these
circuits.
Distortion can be analyzed in either the time domain or frequency
domain, depending upon the characteristics of the nonlinearities of cir-
cuits. The time domain approach first computes the steady state re-
sponse of the circuits to sinusoidal inputs. The frequency components of
the response of these circuits are then computed by a post fast Fourier
transform analysis. Although this approach is universal, a major draw-
back of the approach is that the time domain response of the circuits
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