US1696234A - Antenna - Google Patents

Description

Dec. 25, 1928. 1,696,234

R. A. HEISING ANTENNA Filed on. 18, 1923 lnven' for I lwmondA/fe/smg by-fim 40) Patented Dec. 25, 1928.

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISING, OF MILLBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, OF NEW YORK, N, Y., A CORPORATION 015 NEW YORK.

ANTENNA.

Application filed October 18, 1923. .Serial No. 669,220.

This invention relates to radio transmission by means of vertical antennae or antennae having both a vertical and a horizontal portion.

The invention more particularly relates to means for avoiding difficulties in operating at wave lengths near to or shorter than the free period of the upper part of an antenna.

In such radio systems, where an openantenna is used at a higher frequency than the natural frequency, the upper part of the antenna may act as a loop resonant circuit, tending toincrease the effective resistance 1 and to lower the effective height of the antenna. A consequence of this action is that the loop resonant circuit makes the apparent resistance of the antenna abnormally high. Proper radiation then does not occur.

The explanation of this phenomenon is understood to be as follows, but in stating the probable theory it is not the intention to limit the invention, but rather to state the theory as the probable explanation ofthe operation of the apparatus.

It is believed that certain parts or sections of antennae have capacity between them and that the inductance of theseparts or sections and of the conductor connecting them is of such a value as to cooperate with the capacity to form a tuned circuit which. acts as a tuned loop in series in the antenna. Such an inherent tuned circuit may be termeda parasitic tuned circuit, thereby suggesting that itis undesired and detrimental to the best operation of the system. lVhether thls thcory is correct or not it appears that at frequencies at and above the natural frequency of an antenna some effect of this kind is present which, renders the antenna inefficient as a radiating element and which renders it difficult to transfer energy into the antenna. 1

An object 'of the invention is, therefore, to decrease the effective resistance and to increase the effective height and consequently to increase the radiating efliciency of an antenna at high fre uencies.

To accomplish t 118 result, it is proposed to load the antenna with a plurality of capacities arranged in series and spaced at short intervals, along the vertical portion of the antenna and if necessary along the horizontal portion also.

form of radio transmission system having the elements constituting the invention embodied therein.

Flg. 1 1s a circuit diagram illustrating the invention as applied to an antenna with a.

flat topped portion; Fig. 2 is a modified form thereof, as applied to a vertical anten-' na, the supporting elements for the antenna being omitted; Figs. 3 and 4 are diagrams referred to hereinafter in explaining the theoretical aspects of the invention; and Fig. 5 is a circuit diagram of the invention as applied to an antenna having a fiattopped portion consisting of a plurality of conductors.

Referring toFig. 1 the circuit 1 represents a low frequency circuit or source, of signal waves comprising microphone 2, source of. direct current 8, andprimary of transformer 4. The high frequency circuit 5 includes a source of high frequency carrier waves 6 and primary of transformer 7 By means of transformers l and 7 the low frequency or signaling waves and the high frequency or carrier waves are impressed upon the modulating and amplifying device 8. This device may be any modulation system such as of the well known type, disclosed in the patent to Schelleng, No. 1,437,021, granted November 28, 1922. The entire transmission apparatus 14 typifies any source of waves to be radiated. The modulated waves are impressed, by means of the transformer 9, up-

on the antenna. circuit which comprises a lll an antenna loaded with capacities C, arranged in series and spaced apart at intervals. The modulated waves from the source 14 are impressed upon the antenna by means of the transformer 9.

Fig. 3 is a diagramillustrating the reason why the effective resistance of an antenna of the type of Fig. 1 increases at short wave lengths. The principal aerial-to-grouml ca pacity of the antenna is represented by capacity 15. The parts of the antenna have capacity between them as indicated by the dotted capacities 1S and the inductance of the conductor cooperates with the capacities to form a loop-resonant circuit of one or more degrees of freedom. The parts 14- and 9 correspond to the similarly numbered portion of Fig. 1. The tuned circuit thus formed may be two-branched, having one branch including the left hand capacity 18, the inductance of the left hand horizontal portion, and the inductance of the upper vertical portion. The other branch includes the right hand capacity and the inductance of the right hand horizontal portion and the upper vertical portion. Inasmuch as the vertical lead is usually connected to the horizontal part of an antenna near one end thereof, one of these branches will usually be absent. However this discussion of Fig. 3 indicates that the principles of the invention apply to cases where the parasitic tuned circuit has several degrees of freedom.

Fig. 4 is a circuit diagram for elucidating the action of a vertical antenna such as that of Fig. 2 when the capacities constituting the present invention are not applied thereto. The capacity 17 represents the capacity between the upper part of the vertical lead 10 and a part lower down on the vertical lead 10 but above the coupling transformer 9. The inductance 16 represents the distributed inductance of the vertical portion. The inductance 16 and capacity 17 combine to form a resonant circuit. At and around the free period of this circuit it becomes very difficult to secure proper radiation because the reactance of the antenna changes at certain frequencies to inductive reactance, the resistance increases, and the effective height decreases. The capacity 15 constitutes the principal antenna-ground capacity of the antenna.

hen condensers are included in circuit as in Figs. 1 and .2, the resonant effects described in connection with Figs. 3 and 4 will be absent or will occur only at much higher frequencies so that the upper limit of the working frequency range is much extended.

Fig. 5 shows a complete antenna comprising a vertical portion or lead 10 and horizontal conductors 11 loaded with a plurality of capacities C, arranged in series and spaced at intervals along both the vertical and horizontal portions. The vertical lead is joined to the horizontal portion in the conventional manner. shown here as being connected thereto at an intermediate point of the horizontal portion. The operation of the arrangement of Fig. 5 will he understood from a consideration of the discussion of Figs. 1 and 3.

The condensers C may consist of strain condensers of sutlicient me-hanical strength to withstand the pull of the antenna con ductors or alternatively they may consist of relatively weal: mechanical structures. In the latter case the sections of the antenna between which condensers are to be placed will be separated by suitable insulators around which the condensers are shunted.

Having described the invention in detail, the various features and combinations inherent therein which are believed to be novel and patentable are set forth in the 'appended claims.

What is claimed is:

1. In an open radiating circuit for transmitting at short wave lengths, means for increasing the effective natural frequency of said circuit comprising a plurality of capacities included in series in said circuit and spaced apart from each other, the inductance and capacity of the portions of said circuit between said spaced capacities being too small to form an element which can be self-resonating at any wave length in the neighborhood of the short wave lengths employed.

2. ,In an open transmitting antenna, means forincreasing the upper limit of the frequency range over which the antenna can be worked comprising a plurality of small capacities arranged in series in the open antenna at spaced intervals, said capacities being of such value that the rcactzrnce of each of the sections of said antenna measured in series with an adjacent capacity is capacitative at the desired working frequency.

In witness whereof, I hereunto subscribe my name this 17th day of October, A. 3)., 1923.

RAYMOND A. HEISING.

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