Page 334 - Electrical Engineering Dictionary

case the problem may be attacked by linear-
quadratic game theoretic approach resulting
H in a set of Riccati equations. H ∞ (H infin-
ity) methods may be used in robust stabiliza-
tion, robust performance design, disturbance
attenuation, optimal tracking, model follow-
ing, optimal sensitivity design, etc.
H See horizontal.
H infinity design See H ∞ design.
H ∞ design a group of robust controller
design methods based on the methodology H modes the wave solutions with zero
of the Hardy space H ∞ consisting of all electric field component in the direction of
complex-valued functions of complex vari- propagation. Also known as transverse elec-
able that are analytic and bounded in the tric (TE) modes.
open right half-plane. The least bound that
H parameters characterizes a microwave
may be imposed on this function is its H ∞
norm. Since the open right half-plane may network with an arbitrary number of ports by
relating the total voltages and currents at the
be replaced by the imaginary axis jω, H ∞
methods provide a direct generalization of ports.
the classical frequency domain approach to
control system design. H-D curve See Hurter–Driffield curve.
A standard problem is to design a con-
H-mode See transverse electric wave.
troller that ensures the internal stability of the
closed-loop system and minimizes the H ∞
H-plane in measuring an antenna’s radi-
norm of the transfer function between the in-
ation pattern, the plane that is perpendicular
puts (reference signals, disturbances) and er-
to the current in the element and therefore
rors. Since this transfer function is equal to
contains the magnetic field intensity vector
the sensitivity function, such design results
field. This plane is perpendicular to the elec-
in optimal sensitivity. The standard problem
tric field (E) plane cut.
is then transformed into an equivalent model-
matching problem with a fixed, possibly un-
H-plane sectoral horn a horn antenna
stabletransferfunctionderivedfromtheplant
where the aperture is formed by flaring the
and a “free parameter” stable compensator
walls in the direction of the H-plane. The
to be chosen. The compensator is found by
electric field (E) plane dimension is left un-
minimization of the supremum over all fre-
changed from that of the waveguide feed.
quencies of the modeling error. Finally, an
optimal (or suboptimal) controller is synthe-
H-tree a popular clock distribution tree
sized based on the found optimal (or subop-
topologically that resembles the H shape. It
timal) solution to the model-matching prob-
introduces the least amount of clock skew
lem. To meet specific dynamic objectives the
compared to other distribution topologies.
transfer functions are modified by pre- and
postfiltersintheformoffrequencydependent
Haar transform unitary transform map-
weighting functions. Although the primary
ping N samples g(n) to N coefficients G(k)
problem is formulated in frequency domain,
in a way that corresponds to repeated two-
it may be solved both by input–output and
point averaging and two-point differencing.
state space techniques. In the former case the
The 2 × 2 Haar transform is
algorithms are based on spectral and inner–

outer factorizations and approximation the- 1 1 1
H 2 = √
orems for complex functions. In the latter 1 −1
2
c
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