group. Parameters such as device character-
istics, quiescent bias point, RF load line, sig-
nificant harmonic and/or mixing frequencies,
and amplitude and waveform of the applied
signal(s) should be included with the class
definition, thus defining the major contribu-
tors to the physical actions taking place in
one of these amplifiers.
harmonic analysis
the branch of math-
ematics dealing with the decomposition of
signal functions as a linear combination of
basis functions which represent “waves” of
various frequencies. When the basis func-
tions are sines and cosines each with a fre-
quency that is an integer multiple of the
signal’s frequency, we have trigonometric
harmonic analysis, in other words classical
Fourier analysis, which provides the ampli-
tudes and phases of the constituent sinusoids.
( See
Fourier transform
. ) With other basis
functions, for example wavelets, we have
non-trigonometric harmonic analysis ( See
wavelet
,
wavelet transform
). Abstract har-
monic analysis studies the generalization of
Fourier analysis to abstract spaces.
harmonic balance technique
one of sev-
eral techniques for analyzing nonlinear cir-
cuits. The nonlinear circuit is divided into
two portions of linear and nonlinear ele-
ments, and a portion of linear elements is cal-
culated in a frequency domain and a portion
of nonlinear elements is calculated in a time
domain, respectively. The calculated volt-
ages or currents at connecting nodes of these
portions are balanced by using Fourier trans-
forming or inverse Fourier transforming.
harmonic component
a Fourier compo-
nent of order greater than one of a periodic
waveform.
harmonic content
the internally gener-
ated, harmonically related spectral output
from a device or circuit. Harmonic energy
is that energy that is at exact multiples of
the fundamental frequency, generated by the
nonlinearities within the device or circuit act-
ing on the fundamental frequency.
harmonic converter
found in a mi-
crowave receiver, this component uses the
technique of harmonic mixing to convert the
RF signal to a lower IF frequency for fur-
ther processing. Harmonic converters can be
used as part of a vector network analyzer.
harmonic distortion
caused by the non-
linear transfer characteristics of a device or
circuit. When a sinusoidal signal of a single
frequency (the fundamental frequency) is ap-
plied at the input of a nonlinear circuit, the
output contains frequency components that
are integer multiples of the fundamental fre-
quency (harmonics). The resulting distortion
is called harmonic distortion.
harmonic frequency
integral multiples
of fundamental frequency. For example, for
a 60-Hz supply, the harmonic frequencies are
120, 180, 240, 300,
. . ..
harmonic generation
in nonlinear op-
tics, the process in which a laser beam in-
teracts with a material system to produce
new frequency components at integer multi-
ples of the frequency of the incident beam.
Under carefully controlled circumstances,
the lower-order harmonics (e.g., second and
third) can be generated with high (
> 50%) ef-
ficiency. Under different circumstances, har-
monics as high as the 30th can be generated.
harmonic load-pull measurement
a
measurement method where transfer char-
acteristics of a device at the fundamental
frequency can be measured by electrically
changing the load impedance at harmonic
frequencies.
harmonic orthogonal set
the set of func-
tions
e
jωt
.
It is called harmonic because
each basis function is a harmonic of a cer-
tain frequency and because the inner product
between any two functions is zero:
R
+∞
−∞
e
jω
1
t
e
jω
2
t
dt = 0, ω
1
6= ω
2
c
2000 by CRC Press LLC