US 2124424 A
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Jul 19, 1938. L Mcc. LEEDS 2,124,424
2 ANTENNA SYSTEM Filed Jams, 1956 Fig. l. Fi z.
Source Source Inventor-1 I Laurance M. Leeds,
by 77- His A trney.
Patented July 19, 1938 v ANTENNA SYSTEM Laurance McConnell Leeds, Schenectady, N. Y.,
assignor to General Electric Company, a 001 v poration of New York 1 Application January 3, 1936, Serial "No. 57.343
10 Claims. (01. 250-33)' *My' invention relates to a high frequency antenna system and moreparticularly to a means for feeding a half wave vertical antenna in such a manner as substantially to eliminate standing lel conductors 6 and 1 and a third'conductor 8 which closes the bottom of section 5. An inn-- pedance matching section of this type is particularly well suited for connecting the transmission line to the antenna since it has a very low imevery respect as that described in Fig. 1 with the waves on the transmission line feeding the anpedance at its closed end and a relatively high 5 tenna. impedance at its open end.
It is Well known to the prior art that a half A high frequency source is indicated generally wave vertical antenna has a desirable radiation at 9. field pattern for certain applications such as In order that energy may be transferred from police department use, because of its equal field transmissionline 2 to antenna l with minimum 10 intensity in all horizontal directions. Such an loss, standing waves must be eliminated from the antenna usually requires feeding from one end. transmission line. To achieve this result two Because of its high end impedance, an impedance conditions must be satisfied; first, the transmismatching transmission line section has been insion line at the pointwhere it is connected to the serted between the transmission line and the animpedance matching section must look into an- 15 tenna. Although in the prior art the surge imimpedance which is equal to the surge impedance pedance of the transmission line. has been of the transmission line; In the second place, it
. matched by an impedance matching section, it must also operate into a balanced load. If either has failed to eliminate standing waves on the of the aforesaid conditions remains unsatisfactransmission line. This, of course, is due to the. fied, reflection will occur and standing waves 20 fact that the half wave antenna can not symwill be established on transmission line 2. metrically load the impedance matching section. S nce t s po s b e o Connect a half Wav Since the antenna can only be connected to one end fed antenna to a quarter wave impedance arm of the section, a high impedance load to mat hing s tion Withou pres n in n n lground is placed on one side'of the section but anced load, it has been found that it is necessary 25 not on the other. This unequal loading is reto counteract this unbalancedloading by confiected in the transmission line and standing necting transmission line 2 to impedance match-' waves result. ing section 5 in a non-symmetrical manner. If It is an object of my invention to provide a .outer conductor 4 be connected to a point of means for connecting a transmission line to an minimum potential in impedance matching sec- 30 impedance matching transmission line section in tion ,5, it is clear that there will be some point on such a manner as substantially to eliminate arm I to which inner conductor 3 may be constanding waves on the transmission line. nected such that transmission line 3 will lookinto It is a further object of myinvention to cona balanced load. If the dimensions of the various nect atransmission line to an impedance matchelements in the transmission line, the impedance 35 ing section in such a manner as to balance any matching section,and the antenna, are properly unequal loading placed on the impedance matchchosen so that this point on arm 1 also correing section by an antenna. 7 sponds to the point where conductor 3 must be The novel features which Ibelieve to be charconnected to match the surge impedance of transiO acteristic of my invention are set forth with parmission line 2, standing waves will be substantial- 40 ticularity in the appended claims. My invention 1y eliminated from the transmission line. itself, however, both as to its organization and By way of exampleone antenna system for method of operation together with further obtransmitting a 30.1 megacycle wave which has L jects and advantages thereof, may best be underbeen found to give highly satisfactory results has stood by reference to the following, description aetransmission line whose surge impedance is 54 45 taken in connection with the accompanying drawohms and a quarter wave impedance matching ingin which Figures 1 and 2 represent two em section whose surge impedance is 490 ohms. The bodiments of my invention. antenna pipe was 1 inches in diameter and the Referring to Fig. 1 of the drawing, I have in-' quarter wave conductor arm 1 was of #8 wire 'dicated at I a half wave vertical antenna and at spaced 13 inches from arm 6. When inner con- 50 2 a transmission line having an inner conductor ductor 3 was connected to arm 1 at a point 15 3 and an outer concentric conductor 4. Since inches above conductor 8, standing waves were the end impedance of the half wave vertical ansubstantially eliminated from transmission line 2,
tenna is always relativelyhigh and since the 'Referring to Fig. 2 of the drawing, I have '55 surge impedance of a concentric transmission line shown an open wire transmission line In having 55 is much lower, a quarter wave impedance matchtwo' conductors II and [2 feeding impedance ing transmission line section 5 is inserted bematching section 5 rather than the concentric tween antenna I and transmission line 2. Imtransmission line 3 of Fig. 1. The operation with pedance matching section 5 comprises two paralan open wire transmission line is the same in tionat a point of minimum potential, and the inner conductor .of said transmission, line being many modifications may be made both in the circuit arrangement and: in the instrument-antics" employed, and I therefore contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.
What I claim as new and desire tosecure by f Letters Patent of .the United States is:
1. The combination comprising an impedance matching transmission line section having a high impedance at oneend and a substantially zero impedance at the other end, said section including two substantially parallel conducting arms, a half wave antenna connected to one arm of said impedance matching section at its high impedance end, and a two conductor transmission line, one of said conductors being connected to said impedance matching section at its minimum impedance point and said second conductor being connected to an intermediate point on the unloaded arm of saidimpedance matching section.
2-. The combination comprising an impedance matching transmission line section having a'high impedance at one end, a substantially zero impedanceat the other end, said section including two substantially parallel conducting arms, a half wave antenna connected to one arm of said impedance matching section at its high impedance end, and a concentric transmission line, the outer conductor of said transmission line being connected to said impedance matching secconnected to an intermediate point on the unloaded arm of said impedance matching section. 3. The combination comprising a half wave antenna, a transmission line, an impedance matching transmission line section including two substantially parallel conducting arms connecting said antenna to said transmission line, said arms being electrically connected together at one end, said antenna being connected to one arm of said impedance matching section at its open end, and said transmission line being connected to said impedance matching section at said electrically connected ends and to an in-. termediate point on the other of said arms,- thereby to balance the unbalanced load placed on said impedance matching section by said antenna and thereby substantially to eliminate standing waves on saidtransmission line.
4. The combination comprising a half wave antenna, a transmission line, and an impedance matching transmission line section including two' substantially parallel conducting arms connecta ing said antenna to said transmission line, said transmission line being connected to said arms of said impedance matching section at different distances respectively along said section, thereby to balance-the loading of said impedance matching section to substantially eliminate standing waves on saidtransmission line. a
5. The combination comprising an impedance matching transmission line section including two substantially parallel conducting arms having one end electrically closed a half wave end fed. antenna connected to one arm of said impedance matching section at its open end, and means for transmitting high frequency signals to said impedancematching section, said means including means for balancing the unequal loading imposed on said impedance matching section by said antenna.
6. In combination, an antenna, a transmission line, and an impedance matching transmission line section, said antenna and transmission line each being connected to said transmission line section in an. unbalanced relation thereto, and means to match the unbalance produced by said antenna by the unbalance produced by said transmission line, to cause said transmission line to' operate into .a balanced load.
'7; In combination, a transmission line having one conductor thereof extending beyond the end of the other conductor to form an antenna, a second conductor shorter than said first conductor connected to said one conductor at the point substantially adjacent the end of the other conductor and having a length substantially equal to a quarter of a'wavelength of the wave on which said vantenna operates, and. means to connect said other conductor to said second conductor at a point thereof selected to produce a minimum of standing waves on said transmission line.
,8; In combination, a transmission line having one conductor thereof extending beyond the end of the other conductor to form an antenna, a second conductor shorter than said first conductor'connected to said one conductor at a point substantiallyadjacent the end of said other con ductoriand extending substantially parallel to tenna operates, and means to connect said end i of said other conductor to said second conductor at a point thereof between the ends thereof.
9. In combination, a transmission line comprising two conductors having a length of a quarter of a wavelength, of the wave on which said transmission line operates, said conductors being connected together at one end'and open at the other, end, an antenna connected to said other end ofone of, said conductors, a high frequency apparatus, and means including said high frequency apparatus to connect said one end to the'other conductor at a point thereof intermediate the ends thereof. V
'10. In combination, a transmission line comprising two ,conductors having a length of a quarter, of 'a wavelength of the Wave on which said transmission line operates, said conductors being connectedtogethe'r at one end and open at the, otherend, an antenna connected to said other end of one of said conductors and high frequency apparatus connected between said two conductors'at different points along the length thereof selected in accordance with the resistance at the end of said antenna adjacent the end of said one conductor to which end said antenna is connected