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An axonometric view of the balun balun for our multibanda antenna system balun for our multibanda antenna system balun for turnstile antennas

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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 phenomena.
The "virtual ground node" has, in the physics of the radio-electric phenomena, the same importance as the "fulchum of the lever" has in mechanics.

Patent n.0001347484 (ITAPA20030019)
Visit the European Patent Office to see all the patents of mine


by Francesco Errante

Scientific purposes :

a. The balun described hereby enables to demonstrate that the 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 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 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 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 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 wavelength open dipole antenna, exhibits a phase-angle difference of +/- 90 degree with respect to the virtual ground node.

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 " .

Circuit description

In the field of radio-engineering, a multitude of systems are well-known for matching an 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 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 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 one.
(similarly, a device for splitting up the 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 conductive chassis(7).
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.

All the concepts, methods, designs and devices presented on this web site
are the original novelty works of FRANCESCO ERRANTE.
Patents & Copyright © 1985- of FRANCESCO ERRANTE.

Material is governed by the Copyright, Designs and Patent Act.
No reproduction, in whole or in part, without written permission.
Copies of these documents made by electronic or mechanical means, including information storage and retrieval systems, may only be employed for personal use.
All rights reserved.

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