US1599453A - Antenna structure - Google Patents

Description

Sept. 14 lss. q f 1,599,453

Y H. A. AFFEL ANTENNA STRUCTURE Impedance zyue IN V EN TOR.

Wj TTORNE Y Patented Sept. v14, 1926.

UNITED srATss 4HERMAN Virais' PATENT O F'Fics. 11

A. ARIEL, OF BROOKLYN, NEW YORK, AssIGNoR'TO AMERICAN TELE-PHONE y AND TELRCRAPH COMPANY, A CORPORATION or NEW YORK', f

ANTENNA STRUCTURE. 'y

yApplicant@ iea'yrune 24,1922. seria1No`.57o,54o.

.This invention relates, to antenna struc-- tures, and particularly to means for adapting a .long antenna for the efficient voperation with a plurality Aof .different wave lengths. l

For some time past it vhas beenlnown that long horizontal antennae areparticularly well adaptedA for the'reception of signals, since they ,possess a high degree of diin' zu.)

rectivity. On the other hand, a particular long antenna structure 1s adapted to receive only the long wave lengths efficiently, which i consequently precludes its use forysatisfac-v tory shorter wave length reception. i. y

It is the objectv of thisinvention-to ypro-y vide means for renderinga long antenna structure capable of functioning efficiently with waves of -ae vplurality "of different lengths.

This invention will be better understood from the followingdescription whenfread in connectiongwith the attached drawing, of which Figure -l shows the invention einbodied in an antenna of the dumb-bell type; Fig. 2 shows schematic equivalent circuitsof the arrangement shown in Fig. l, Fig. showsthe invention,embodied in an anten-V na of the inverted ltype; Fig. l v,snows schematic equivalent circuits of the arrangei ment in Fig. 3; and Figs. 5 and 6 are groups of curves which serve to 'describe `the manner in which the invention functions.'

In Fig. l, l represents an antenna of the long horizontal type, 4the distant yends'of which may if desired be terminated through resistances R04 and RO', which, as described in my copendingapplication, vSerial No. 585,- 435, filed August:l ,31, 1922, simulate the characteristic impedance ofthe antenna, Counected latthe lmidpointyof the antenna by means ofthe inductive coupling 2 is ak plurality of receiving circuitswhich are rendered selective to particular,frequencies or bands ofr frequencies by means of the filters F10 F11 and F12.y The antenna v l has .connected therewith` at predetermined points throughout. its` .length the` ltersF,L and F1, Fl and F2. .Although four yfilters are Ashown v connected withk the antenna, the invention is 'not limitedjto the v particular ,number'showin since anynurnber of lters may be connected, depending upon the number of wave lengths which vthe antenna is designed to receive.

As has been briefly referred toy heretofore,

every antenna circuit should havek a partie'- ular optimum length for the particular wave length or range of wave lengths intended to be receivedin order to attain efficient ,operation yof vthe system.. My invention. consists ininserting in the antenna structuregat predetermined locations ya .plurality of lowjpass .filters arranged as shown in Fig. 1 in groups of two each, which-.serve to termif nate the antenna structure vfor 'particular yfrequencies at the pointsA whereinthey are inserted and render the intervening section of antenna' adapted vfor the reception of a `particular frequency. 'lhus,v forexample, vthe filters F1 and. F1l would have-.the atltennation-frequency characteristic represented lby the curve d, inv Fig.y vThisjis the characteristic` for a lowTpass filtenhaving a cut-off. point at the frequency f1. It will .be seen, therefore, that by inserting ya group of two of these filters inthe antennay v1 .ata predetermined point, depending uponthe length of a wave having a frequency futhemore, since the filtersF1 andFl are ofthe low-pass type, they will transmit `readily frequencies below their cut-off frequencies.

.Consequently they. do not terminate the an-` vantenna is, in effect, terminated at thesaio. points for the said frequency. Furthershows a cut-odffrequencyfz. Accordingly, these filters will serve to terminate ythe anv tenna forxthe frequency f2, and therefore render the section of theantenna betweenl F2 and F2 adapted to..receive that fre?v quency or bandl of frequencies which are `above frf Other groups of'iiltershaving the characteristics represented by'y f vand g in Fig. ,5 could be inserted in the antenna 1 which would serveto` terminate vthe anten/na' at otherpoints and render rvthe intervening antennastructure suitable forthe reception of other/,frequencies than those shown. Furthermore, the antenna between'the terminating resistances RO landfRO ywould,of

course, .be adapted to receive still another andrdifferent frequency from any hereto-fore referred to.

The

ters as .shown in Fig.. l. is to render the andect, therefore, Offinserting the -ltennaA structure highly efficient for the reception of three different frequencies. The complete action attained by thestructure shown in Fig. l may in a sense, be considered lequivalent t0 that whichrwould obtain for three separate antenna structures, each specifically designed to function fora definite wave length range. rllhis is clearly shown in the equivalent circuit 'diagrams of Fig. 2, where the structure a represents the antenna` 1,' which for frequencies f1 or greater is 'effectively terminated by 4the lfilters -F and F1. Siniilarly, the structure represented by b represents the antenna l effectively terminated by the filters lf2 and F2', which is eicie'nt for the reception of frequencies )f2 and greater, and the struc- Yture rep-resentec'l by c of F ig. v2 represents the antenna l as terminated by the resistantes `ith-"and R0.

The arrangement shown in Fig. 3 represents the embodiment of the invention in an inverted L antenna. F2 inserted in theantenna i serve to `terininate this-antenna in the saine manner in which 'they function in connection with'the antenna shown in Fig. yl. The effect of introducing these `filters is to render the anltenna structure of Fig. 3 terminated at the points wherein -they are inserted, which, in effect, makes the antenna suitable for the reception of -three di'erent wave lengths, as clearly Ashown lthe diagrams in Fig. 4

Although i'ny invention is not limited to the ,'use of yany particular type of filter to jeffect 'the discontinuity 'of the fantenna structure itself for particular frequencies, l find that the type of network shown diagrammatically in Figs. l and 3 which includes re'sistance'elements in its malreup is particularly well suited for this purpose, since it 'may be 'designed 'to possess substan tial'ly luniform impedance throughout the lentire range of frequencies, and therefore, -in effect, serves to terminate the antenna at the point wherein it is inserted by an iinpedancejeqiial to the characteristic impedance 'of ithe antenna :for the cut-off frequency of ythe particular filter. rlhis is clearly 'shown in Figs. 5 and G.L Thus in F ig. f6 the curves d', e, f vand g 'represent characteristie impedance-frequency actions of the normaltype ofc-filter, the attenuationfrequency lcharacteristics of which are repren sented by -thefcurves d, e, fand g of Fig. 5,

that is to say, in 'the 'normal'non-dissipative type of filter :the impedance would either increasera'pidly at the cut-olf frequency in Alike manner, -as the attenuation does or wouldy decrease rapidly yto approach lzero, 'depending on the particular type of termination employed.v In filters of the type-represented, for example in Fig. l, the -inipech 'ance fdoes not 'vary as the cut-oil' frequency 'is reached, 'but remains substantially unirlhe. lfilters F1 and form throughout almost any range lof frequency. They use of filters 'of this type, therefore, has the effect of terminating the antenna structure at the point wherein they are inserted by means of an impedance equal to the characteristic impedance of that pari. of the antenna included between the two filters of the group, which, of course, is high-ly desirable, since it avoids creating the effect of an open-ended antenna for the particular frequencyl for which the intervening antenna structure is intended to receive.

For the purpose of making the invention clear and distinct it has been described fas embodied in anantenna having receiving apparatus associated therewith.` The invention, however', is not limited to` a receiving antenna since it is equally well adapted for the purpose of transmitting, 'and accordingly the apparatus shown and described' as receiving apparatus may also be `considered as transmitting apparatus.

Although this invention has been 'disclosed embodied in a particular forni and arrangementof parts, it isto be understood that it is capable of embodiment i-n other and different forms within'the spirit yand scope of the appended claims.

lli/hat is claimed is:

l. An antenna, comprising ,a conductor of such length as to vvefficiently receive waves of predetermined length, and a Vfilterhaving a fined cut-elf point l'connected 'with thesaid conductor and effectively 'terminating the conductor at the point of connection of the W0 said filter for frequencies `'above the cut-'off point, the said point of connection being so Ychosen that the portion of the said antenna between the said poi-nt of connection of the lte'r and point ofc'onnection of a lterini- T105 nal circuit will have the optimum length foi-.frequencies above the cut-off frequency of the filter.- y

2. An antenna, ycomprisin'gra conductor ofk such `length as to eflicfiently respond t0 1l-l0 waves of a predetermined length, and a 'plurality of filters each connected with the said conductors at different places .between thee'nds thereof, each fiilterhaving ia 'fiXed cut-off point whichffor leach filter, is 'dif- "11'5 ferent from 'that of the others, Lto effectively terminate. the conductor lvateach of a 1'plurality `of .points for frequencies above the "cut-ofia poin'tof the iilter,eac'h point o'f-'connection of the said' filters bein-g so chosen 120 `that the portion of the antenna between the point #of rconnection of afpafrticular fiilter 'anc the -end adjacent to the terminal-circuit will have the optimum length lfor frequenciesy 'above fthe cut-olf 'frequency fo'ff the 125 particular ffilte'rf 3. An antenna, comprising a conductorof 'such lengthas to efficiently respond towaves f filters of that particular group.

nected with the said conductor at different places between the terminating point of the antenna and the ends thereof, each filter having a fixed cut-o point and the filters of each group having the same cut-off point which is different from that of the otherA groups of filters, the filters of each group being symmetrically placed upon opposite sides of the terminating point of the antenna, each point of connection of the said lters being so chosen thatv the portion of the antenna between two filters of the same group will have the optimum length for frequencies above the cut-off frequency of the definite intervals between the terminating point and the distant end of the said antenna, the filters more distant from the said terminating point having av lower cut-off point than those nearer thereto.

6. An antenna comprising a horizontal conductor having the distant ends grounded through resistances simulating the characteristic impedance of the antenna and having a plurality of pairs vof filters inserted therein between the terminating point and the outer ends of said antenna, and sym metrically disposed'on eachside of the said terminating point.

7 In a radio signaling system, the combination with an antenna of a plurality of low-pass filters having different cut-off points and a multi-frequency terminal apparatus, the said filters being connected into the said antenna between the point of connection thereto ofthe said apparatus and the distant end and-'so disposed that those more distant from the said apparatus have lower cutoff points than those nearer thereto. u f

8. In a radio signaling system, the coinbination with an Aantenna having its outer ends grounded through a resistance simulating the characteristic impedancepof the antenna of a plurality of pairs o'fLlow-pass filters, the said pairs having different cutoff points7 and multi-frequency terminal apparatus connected with the said antenna, the

said filters being symmetrically disposed on each side of the point of connection of the said apparatus to said antenna and so arranged that the vmore distant ones have lower cut-ofi' points than those nearer the said apparatus. Y

9. A horizontal 'antenna having a plurality of filters eachhaving a different -frequency cut-ofi point, the said filters being connected'therein between the terminatingl point of said antenna and an outer end thereof, the distance vbetween each of said filters and the terminating point of the antenna beingthe optimum length of the antenna for the frequency at whichthe particular filter cuts off.

10. A horizontal antenna having a plul rality'of pairs of' filters, each pair having a different frequency cut-ofiE point, the filters of each pairbeing vconnected kwith the said antennaat points which are upon opposite sidesof the terminating point of the said antenna and the length of the antenna between eac-h pair of filtersbeing the optimuin length for the frequency at which the y particular pair of filters cuts off.

In testimony whereof, I have signed my name to this specification*` this 23rd day of June 1922.

- HERMAN A.y AFFEL.

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