NB. Our radio-communications purpose baluns can be
Errante's OPEN DIPOLE
BRANCH SUPPRESSOR BALUN
The open dipole: an antenna...? NOT, two!
The "virtual ground"
practical application importance in the radio-electric transducers and circuits, by
Francesco Errante, for the understanding of the physics of the radio-electric
The "virtual ground node" has, in the physics of the radio-electric
phenomena, the same importance as the "fulchum of the lever" has in
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A VIRTUAL GROUND BALUN FOR THE
SUPPRESSION OF ANY WHICH ONE OF THE TWO BRANCHES OF AN ½ A WAVELENGTH OPEN
by Francesco Errante
Scientific purposes :
a. The balun described hereby enables to
demonstrate that the ½ wavelength open dipole antenna, also known as
"Hertzian Dipole" is not an "elementary antenna" (by
definition an elementary antenna is an aerial where the condition of
resonance and radiation cannot take place without the presence of all its
parts) but it is, instead, an "elementary array" of 2
radiating/captating elements of a physical length equal to ¼ of a wavelength
each, which are electrically arranged in a counterphase, while being fed in
the middle of them; (The same happens with all the other symmetric dipoles, regardless of
their impedance, also known as radiation resistance.)
b. The balun described hereby enables to demonstrate that
once a virtual ground node is available, it is possible to receive and
transmit radio-electric signals through the space by employing a single
radiating/captating element of a physical length equal to ¼ of a wavelength,
without the need for a natural nor an artificial ground plane; (see -->
ERRANTE's ANTENNA )
c. The balun described hereby enables to demonstrate that
each of the two branches of an ½ wavelength open dipole antenna, at its
frequency of resonance, exhibits an absolute impedance value of 35 Ohm,
unbalanced and referred to the virtual ground node; (Likewise, any which one of the two branches of any other symmetric
dipole will yeld a characteristic impedance value equal to ½ of the impedance
of the dipole to which it belongs.)
d. The balun described hereby enables to demonstrate that
each of the two branches of an ½ wavelength open dipole antenna, exhibits a
phase-angle difference of +/- 90 degree with respect to the virtual ground
e.The balun described hereby, by allowing to
suppress anyone of the two branches of the dipole, has led to confute, once
and for all, the "theory of the antenna image " .
In the field of radio-engineering, a multitude of systems are well-known for
matching an ½ wavelength open dipole to an unbalanced transmission line, they
are usually referred to as balun (a compound term meaning
"balanced-unbalanced"). State of the art balun(s) do not allow feeding of the
two branches of an ½ wavelength open dipole independently from each other and
as a result of that, they do not allow to verify whether it possible to
suppress anyone of them without interfering with the condition of resonance
and irradiation of the remaining one. The invention described hereby
allows to feed each of the two branches of an ½ wavelength open dipole
independently, so that they can become electrically independent from each
other allowing, therefore, to suppress anyone of them without repercussions
on the condition of resonance and radiation of the remaining
(similarly, a device for splitting up the ½ a
wavelength folded dipole antenna is described here)
This result has been achieved by means of a
lumped-constants radio-electric circuit, based around a broad-band
radio-frequency electric transformer(1) winded on a binocular type ferrite
core having a primary winding(2) exhibiting an impedance value equal the one
of the transmission line(3) being used and a center-tapped secondary
winding(4) exhibiting an impedance value of 35 + 35 Ohm. The said impedance
values are referred to the virtual ground. ("virtual ground" is
defined as a point in an electrical circuit that appears to be at ground, but
is not actually attached to ground, it is therefore, a node having a 0 degree
phase angle difference with respect to ground and has the same electrical
potential as the Earth")
The virtual ground node has been obtained by providing the transformer's
secondary winding(4) with a center-tap(5), effectively splitting the
secondary winding in two sections. The virtual ground is then made available
to the whole of the network by a short electrical connection(6) to the device
The transformer's working point is optimized by compensation with the
employment of high-voltage RF duty capacitors(8).
The suppression of one of the two branches of the open dipole is made by
manually operating the high insulation resistance switch(9) diverting the
radio-electric signal from the transformer(1) off the branch of the dipole(11
or 12) and into one lead of the non-inductive 35 Ohm dummy-load(10) while the
other lead of the dummy-load is attached to the virtual ground circuit.
The balun described hereby is characterized by
being a NON fluctuating
impedance RF electrical transformer. All of its
terminations impedance values are set by design, hence the impedance
transformation ratio is a function of them and not viceversa, unlike it
happens with any other balun arrangement.
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