US2617028A - Aerial system comprising a concentric transmission line - Google Patents

Description

NOV. 4, 1952 J sTo 2,617,028

AERIAL SYSTEM COMPRISING A CONCENTRIC TRANSMISSION LINE Filed Feb. 15, 1949 l/VVE/VT'OR Jon Stolk AGENT Patented Nov. 4, 1952 AERIAL SYSTEM COMPRISING A CONCEN- TRIC TRANSMISSION LINE Jan Stolk, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application February 15, 1949, Serial No. 76,434

In the Netherlands April 16, 1948 of the interruption, in which event the envelopeof the transmission line is connected to one part of the interrupted radiator and the inner conductor to the other part thereof, a troublesome current flows alon the outside of the envelope as a result of the different capacities of the two parts of the interrupted radiator with respect to the envelope. As a rule, this current acts upon the radiation diagram in an undesirable manner.

It is known to interrupt such superficial currents by a section connected in series with the outer surface of the envelope; However, this section exhibits properties which are dependent on frequency so that the superficial current is completely suppressed for one frequency only. This is an inconvenience more particularly in the case of aerials having broad-band properties and with tunable aerials.

The present invention provides a construction in which the said inconvenience is obviated.

The invention exhibits the characteristic that the inner conductor of the transmission line is connected to that extremity of one part of the interrupted radiator which is adjacent the interior, the inner conductor being led in an insulated manner through the interior of the other part of the interrupted radiator as far as the external extremity thereof and thence led through the interior of a non-interrupted radiator and through an aperture provided midway of the last-mentioned radiator to the exterior, extending from this point through a distance equal to at least a quarter wavelength in a direction at right angles to the longitudinal axis of the radiator, the envelope of the transmission line being connected to the centre of the last-mentioned radiator.

As will appear hereinafter, the aerial system is thus rendered symmetrical with respect to the envelope, the symmetry obtained not being dependent on frequency.

It is noted that an aerial system connected to 5 Claims. (01. 250-33) 2 a concentric transmission line exhibiting frequency-independent symmetry is known per se. However, such an aerialsystem is a frame aerial.

Furthermore it may be mentioned that a dipole, aerial is known in which the coupling with a concentric transmission line is established by means of a coupling section which is somewhat similar to the'aerial system according to the invention. However, in this known system, separate dipole radiators are secured to the coupling system.

The invention will now be explained more fully by reference to the accompanying drawing, showing, by way of example, one form of COIlStlllCe tion of the system according thereto.

The aerial systemshown comprises three tubular radiators I, 2 and 3, each having a length of approximately V in which i represents the wavelength at the centre of the wavelength range thatmay b covered by the aerial. The radiator 3 is interrupted midway at 4. At'the; extremities, the radiators l, 2 and 3 are interconnected by connectionsi and 6, which are like wise tubular. The spacing ofthe 'radiators'is small with respect to A. The radiators here ex? tend in a plane, butthis is not essential. Here use is made of three radiators, but in aerial systems according to the invention it is also possible to utilise two or more than three radiators connected in parallel. A core 1 of a transmission line I, 8 is connected to the upper part of the radiator 3 and, in the manner shown, led in an insulated manner through the lower part of the radiator 3, through the connecting piece 5 and through the lower half of the radiator l.

The last-mentioned radiator exhibits midway at 9 an aperture through which the core 1 is led to the exterior. The envelope 8 of the transmission line I, 8 is connected along the edge of the said aperture to the radiator I, the aerial system thus being geometrically symmetric with respect to the envelope 8. Voltages set up in phase opposition between the adjacent extremities of the interrupted radiator 3 now do not result in currents being produced along the outside of the envelope 8.

It has been found that the symmetry is not disturbed to any appreciable extent if the transmission line 1, 8 is not exactly at right angles to the longitudinal axes of the parallel radiators in so far that part of the transmission line is concerned which is farther than AA remote from the aerial system.

What I claim is:

1. A folded dipole aerial structure adapted to operate within a predetermined wavelength range comprising first and second parallel radiating elements of substantially equal length, the spacing between said elements being less than a quarter of a wavelength of the central wavelength in said range. first and second conductors having a length relatively small with respect to said elements and interconnecting the respective extremities of said first and second elements, said second element being divided at the midpoint thereof to form a first section and a second section, said first section of said second element,

the corresponding portion of said first element.

and said first conductor being hollow, and a concentric line for feeding said radiators, said line having an outer conductor connected to the midpoint or said first element, and an inner conductor extending through said hollow portion of said first element, said hollow first conductor andradiating elements having a length substantially equal to one half the wavelength of the central wavelength in said range, the spacing between saidxelements being. less. a q ar e f, a wavelength of said central wavelength, first and second conductors interconnecting the respective extremities of said elements. Said; second element being divided at the midpoint thereof to term afirst section and a second section, and first sectionof said Second element, the correspondingportion of. said first element and said first conduster being hollow, and a concentric trans ission line ieed ns said elemen s. sa d line 1 an outer conductor connected to the mi p int at said. that e eme t n p s d a r ght angles thereto and having an inner conductor extending through the hollow portion of said first element, the hollow first conductor and the h0llow first section and being connected to the free end of said second section.

4.'A foldeddipole aerial "system adapted to operate within a predetermined wavelength range comprising first and second parallel hollow radiating elements having a length substantially equal to one half the wavelength of the central frequency in said range, a third parallel radiating element of like length interposed between said first and second elements, hollow first and second conductors interconnecting the respective extremities of said first, second and third elements and communicating therewith, the

spacing between said elements being less than a quarter of a wavelength of the central wavelength in said range, said second element being divided at the midpoint thereof to form a first sectio and a second s c ion, and a con en r ansmission line for feedi g said el ment and avin a tubu ar u e onduct r ccnnec ed to and communicat n th said firs el m nt at e m dpoi t t e eof a d an inne conduc or extend n t o g ne half o sa r e ment and throu h aid. firs c ndu or and said, firs ect o o s d se ond l en a d g; connected to the free end of said second section.

5. An arrangement, as set forth in claim 4, her in sa ute conduct r of, said. concentr line d sp sed at right. an e to sai first lement.

J AN TOLK,

' REFERENCES CITED v The following references are of record in the file of this patent:

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