MYSTERIES OF THE EQUILATERAL TRIANGLE - HIKARI Ltd

Applications 81
Application 4 (Biomimetic “Bat’s Ear” Antenna). A biomimetic antenna
in the shape of a bat’s ear may be constructed from an equilateral triangular
conducting plate that is curved and the base electrically connected to a
circular ground plane with a central monopole element [106].
With reference to Figure 3.4, J. A. Flint [106] has shown that, for certain
frequencies, this yields a higher gain and a radiation pattern with lower side
lobes than the equivalent circular ground mounted monopole and that a good
match can be retained at the coaxial input.
(a) (b)
Figure 3.5: (a) Principle of the Equilateral Triangle in Electrocardiography.
(b) Graphical Determination of the Electrical Axis of the Heart. [45]
Application 5 (Principle of the Equilateral Triangle in Electrocardiography).
Einthoven’s Triangle of Electrocardiography (Figure 3.5(a)), with
vertices comprised of electrodes located on the left arm (LA), right arm (RA)
and left leg (LL), is used to determine the electrical axis of the heart [45].
Normally, this electrical axis is oriented in a right shoulder to left leg direction.
Any significant deviation of the electrical axis from this orientation can
indicate ventricular hypertrophy (straining).
The electrical activity of the heart can be described by the movement of an
electrical dipole consisting of a negative and a positive charge separated by a
variable distance. The directed line segment joining these two charges is called
the cardiac vector. Its magnitude and direction can be described by three
vectors along the edges of an equilateral triangle, each vector representing the
potential difference, ei, across electrical leads connecting the electrodes (e1:
lead 1 from RA to LA; e2: lead 2 from RA to LL; e3: lead 3 from LA to LL).