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Dec. 3, 1946. P. J. KIBLER 2,412,090v TURNSTILE ANTENNA Filed Feb. 14, 1944 OR RECEIVER TO TRANSMITTER OR RECEIVER INVENTOR PAUL J. K|BLER_ ATTORNEY 2,412,090 Patented Dec. 3, 1946 UNITED STATES PATENT OFFICE 2,412,090 TURNSTILE ANTENNA Paul J. Kibler, Fort Wayne, Ind., assignor to Farnsworth Television and Radio Corporation, a corporation of Delaware Application February 14, 1944, Serial No. 522,323 7 Claims. (01. 250—33) 1 , 2 two oppositely disposed radiator elements and a third terminal of the full Wave concentric line particularly to impedance matching and phasing located three-quarters of a wave length distant means used in connection with antennas of ‘this from one of the extreme terminals and a quarter type. ‘ wave length distant from the other extreme ter According to conventional practice turnstile minal is connected to the apparatus to be used antennas comprising a plurality of radiator ele with the antenna. ments symmetrically disposed with respect to one For a better understanding of the invention, another in the same plane are employed for radi together with other and further objects thereof, ating a rotating radio frequency ?eld having a predetermined pattern. In order to establish such 10 reference is had to the following description, taken in connection with the accompanying draw a ?eld of substantially uniform intensity it is necessary to supply substantially equal currents ing, and its scope will be pointed out in the to the respective radiator elements in a, prede appended claims. termined phase relation to one another. In the In the drawing: I case of a turnstile antenna comprising four radi Fig. 1 is a diagrammatic illustration of a four ator elements, the elements are disposed at 90° element turnstile antenna embodying the pres angles with respect to one another and the ex ent invention; ' ‘ citing currents are supplied thereto in time Fig. 2 is a diagrammatic representation of a quadrature. In order to equalize the exciting concentric transmission .line for use with the an currents it is necessary to match the impedances tenna array of Fig. l; and, of the radiator elements to the transmission Fig. 3 is a schematic illustration of a network . medium by which the currents are impressed of lumped circuit elements also for use with the upon the radiators. It also is necessary to couple antennaarray of Fig. 1. the current feeding transmission medium to the Having reference now particularly to Fig. l of radiator elements in such a manner that the ex the drawing, there is shown a four-element turn citing currents are impressed successively upon stile antenna comprising a north radiator element the respective radiator elements in proper phase. N, an east radiator element E, a south radiator In antennas of this character previously em element S, and a west radiator element W. These This invention relates to turnstile antennas and ployed the impedance matching and phasing _ means have been of such characters that it has not been possible to effect the required adjust ments for each radiator element individually. It, to one another.- The elements are of equal lengths. In the illustrated embodiment of the invention the radiator elements are each approxi therefore, has been necessary to make these ad justments only after complete assembly of the antenna array. mately equal to a quarter wave length which is related to the radio‘frequency at which it is de sired to establish the rotating ?eld. Connected between the inner ends of each of the radiator elements N, E, S and W are adjustable condensers Then, because of the mutual interdependence of the antenna components, the adjustments are relatively dif?cult to make. It is an object of this invention, therefore, to provide a novel impedance matching and phasing means for a turnstile antenna which will facili tate the preliminary adjustment of the imped ance matching and phasing means. In accordance with the invention there is pro vided a turnstile antenna having four equal length radiator elements located in the same radiator elements are all disposed in the same plane and are located at 90° angles with respect 40 ll, I2, I 3V and M, respectively.‘ The opposite te'r— minals of each of these condensers are connected to ground. There also is connected betweenlthe inner ends of the radiator elements N and W a concentric transmission line l5, the effective length of which is substantially equalto a quarter wave length. Similarly, there is connected be plane and disposed at 90° angles with respect to tween the inner ends of the opposite pair of radi one another. Associated with each of the radi ator elements E and S a quarter Wave length ator elements is an adjustable reactance device concentric transmission line‘ IS. The inner ends by means of which the radiator elements each may be tuned for parallel resonance at the oper 50 of any two oppositely disposed‘ radiator elements such as W and E constitute terminals A and B to ating frequency. Adjacent tuned radiator ele which there may be connected apparatus for sup ments are connected to the respective ends of two plying exciting currents of opposite phase to- the quarter wave length concentric transmission lines. antenna array. The outer conductors of the The extreme terminals of a full wave concentric transmission line are connected respectively to Gr Ul transmission-lines l5‘ and I6‘ are grounded, pref? 2,412,090 3 4 erably, adjacent the terminals A and B, respec tively. ' impedance of one of the radiator elements. This impedance comprises the load connected to the B terminal of the three-quarter wave length line section IQ of the phasing line H. In Fig. 2 there is illustrated one type of trans mission medium suitable for connection to the Inasmuch as it is characteristic of a three antenna terminals A and B of Fig. l, as indicated quarter wave length concentric transmission line by corresponding characters of reference in the two ?gures. This transmission medium com to invert impedances at the terminals thereof, the impedance looking into the three-quarter prises a concentric transmission line I ‘I of full Wave length section 1-9 from the point D also wave length between the terminals A and B. This concentric line- is divided into a quarter 10 is equal to twice the impedance of one of the wave length section l8 and a three-quarter wave tuned radiator elements. length section I9. At the junction point of . By connecting the phasing line sections l8 and 19 in parallel at the point D the impedance these two line sections there is connected‘a of the complete system looking toward the point concentric transmission line 2| of whatever length is required to couple the phasing trans 15 D from the connecting transmission line 2| is equal to the impedance of one of the tuned mission line I 1 to a circuit C such as a trans radiator elements. Inasmuch as originally this mitter for use in connection with the antenna impedance was adjusted to correspond to the array. The outer conductor of the transmis sion line 2| is grounded and also connected to characteristic impedance of a concentric trans the transmission line I’! as shown. _ 20 mission line, a line of this character such as Considering now the manner in which a turn 2| may be connected at the point D and there stile antenna in accordance with the present in by will be terminated in its characteristic im vention is adjusted to‘ operate in the desired pedance. ‘ Thus, by means of the described impedance manner, reference will be made to Figs. 1 and 2. Inasmuch as each of the radiator elements, such 25 matching arrangement the individual radiator as the north radiator N, has a physical length elements may be excited by currents of equal equal to a quarter wave, the radiator element magnitude. Also, by reason of the quarter wave will exhibit a reactance at the related» fre_ length concentric line coupling between ad quency which is slightly inductive. Consequent jacentv radiator elements such as N and W, and ly, the condenser II is adjusted suitably to pro 30 E and S, the exciting currents for the two radia tors of each pair are in phase quadrature. Fin vide the necessary capacitative reactance so that ally, by means of the quarter wave length section the radiator element is tuned for parallel reso t8 and the three-quarter wave length section nance at the radio frequency related to the I9 of the phasing transmission line I1, exciting length of the radiator element. Thus, the im_ pedance represented by the radiator element N 35 currents are supplied to the points A and B, and the condenser Il may be made purely re respectively, of the two pairs of radiator ele sistive. Also, by suitable adjustment of the ef ments in phase opposition. In this manner the fective length of the radiator element, together four radiator elements of the turnstile antenna with a compensating adjustment of the tuning are excited by currents of equal magnitude in condenser, the effective impedance of the radia 40 phase quadrature. tor may be made equal to the characteristic-im Fig. 3 illustrates an alternative form of a phas ‘ pedance of a concentric transmission line. Similarly to the described adjustment of con denser l l, the condensers I2, l3 and I 4 are ad justed so that the respective associated radiator elements E, S and W have impedances, each equal to the characteristic impedance of a con ing transmission medium for supplying exciting currents of opposite phase to the two pairs of ra diator elements at the points A and B of Fig. 1.v This medium comprises a balancing network formed of condensers 22 and 23 between which there is connected in series an inductor 24. The reactances of the condenser 22 and the inductor 24 are made numerically equal to twice the react ator elements N and W. are coupled by the con centric line l5 and the radiator elements E and 50 ance of the condenser 23. The values of these re actances will determine the effective impedance of S are coupled by the concentric line !6, these the network as seen from C. By suitably choosing concentric lines are terminated at each end in the values of these reactances, the network im their characteristic impedances. In such a case pedance may be matched properly to a transmis then the radiators N and W are effectively con nected in parallel by the quarter wave length Cr an sion medium connected thereto. The condenser 22 is connected to the terminal line l5. Similarly, the radiators E and S are A of the antenna array of Fig. 1 and the junction e?ectively connected in parallel by the quarter point between the inductor 24 and the condenser wave length line Hi. In such a case the im 23 is connected to the terminal B of the antenna pedance of the pair of radiators N and W at the point A and also the impedance of the pair 60 array. The condenser 23 is connected to ground, as shown, and the junction point between the con of radiators E and S at the point‘B is equal denser 22 and the inductor 24 is connected to the to one-half of the impedance of one of the tuned apparatus with which the antenna array is to op radiator elements. The impedance of the pair erate. > of radiators N and W at the point A comprises A network in accordance with that illustrated in the load for the quarter wave length section l8 Fig. 3 is similar to one described by S. Frankel, in of the phasing transmission line l1. Since it is the Proceedings of the I. R. E, of September, 1941. characteristic of the quarter wave length line Such a network functions to impress currents de to invert impedances, the impedance looking into rived from the utilization circuit C upon the ter the quarter wave length section l8 of the phas minal points A and B in phase opposition and bal ing line I‘! from the point D, therefore, is equal anced with respect to ground. The antenna array to twice the impedance of one of the radiator as shown in Fig. 1 then functions in a manner elements. similar to that described to produce a rotating In like manner, the impedance at the point radio frequency ?eld of a substantially circular B looking into the parallel arrangement of the pattern. ~ . radiator elements E and S is one-half of the centric transmission line. Thus, when the radi 2,412,090 5 6 In the foregoing description reference has been phase coupling means for said antenna connect made to feeding or supplying currents to an an tenna array in accordance with this invention. This is the case where the antenna is to be used ed to two oppositely disposed radiator elements. , in conjunction with radiant energy transmitting apparatus.‘ It is obvious, however, to those skilled 3. A turnstile antenna comprising, four equal length radiator elements located in the same UL plane and disposed at 90° angles. with respect to one another, a pair of quarter wave length eon centric transmission lines connected respectively between adjacent radiator elements, a tuning condenser connected to each of said radiator ele ments to match the impedance of each element to the characteristic impedance of one of said cordingly, it is contemplated that the structures transmission lines, and an opposed-phase cou de?ned in the appended claims are suitable for use pling medium for said antenna including a pair either with transmitting or receiving apparatus. of transmission lines of different lengths connect Therefore, the ‘term “utilization circuit” used in this speci?cation and in certain of the claims is 15 ed respectively to two oppositely disposed radiator elements. intended to de?ne a circuit associated with either 4. A turnstile antenna comprising, four equal transmitting or receiving apparatus. length radiator elements located in the same It also will be obvious to those skilled in the plane and disposed at 90° angles with respect to art that the invention is not limited to use with radiator elements substantially of quarter wave 20 one another, a pair of quarter Wave length con centric transmission lines connected respectively lengths. It is contemplated that the invention between adjacent radiator elements, a variable may be embodied in antennas having radiator ele" tuning condenser connected to each of said ra ments of substantially any desired lengths, pro diator elements to match the impedance of each vided that in any one antenna array all radiators element to the characteristic impedance of one are of the same length. In the case where the of said transmission lines, and a coupling medium radiator lengths are such that the radiator re for said antenna, including a pair of concentric actances at the operating frequency are capacita transmission lines di?ering in length by a half tive rather than inductive, as in the case de~ wave length connected respectively to two oppo scribed, the matching reactances required for sitely disposed radiator elements. tuning will of necessity have to be inductive. 5. A turnstile antenna comprising, four equal Hence, in place of the condensers H, l2, l3 and length radiator elements located in the same I4, corresponding adjustable inductors will be plane and disposed at 90° angles with respect in the art that such an antenna also is susceptible of use with receiving apparatus, in which case the radio frequency currents collected by the antenna are transferred to the receiving apparatus. Ac required, From the foregoing description of one embodi ment of this invention, it follows that there is provided an antenna system, each radiator ele ment of which is susceptible of individual pread justment of its effective impedance, whereby after complete assembly of the antenna array no fur ther adjustments are required. While there has been described what, at pres ent, is considered the preferred embodiment of the invention, it will be obvious to those skilled to one another, a pair of quarter wave length concentric transmission lines connected respec tively between adjacent radiator elements, a vari able condenser connected to each of said radi ator elements to tune each element for parallel resonance at the operating frequency and to match the impedance of each element to the characteristic impedance of one of said trans mission lines, and a full wave concentric trans mission line having its two extreme terminals connected to two oppositely disposed radiator in the art that various changes and modi?cations elements and having a third terminal three quar may be made therein without departing from the ters of a wave length distant from one of said invention, and therefore, it is aimed in the ap extreme terminals and a quarter wave length pended claims to cover all such changes and modi distant from the other of said extreme terminals, ?cations as fall within the true spirit and scope whereby currents of opposite phase may be apof the invention. 50 plied to said opposed radiator elements from a What is claimed is: source connected to said third terminal. 1. A turnstile antenna comprising, four equal 6. A turnstile antenna comprising, four equal length radiator elements located in the same length radiator elements located in the same plane and disposed at 90° angles with respect to plane and disposed at 90° angles with respect to one another, a pair of quarter wave length trans one another, a pair of quarter wave length trans mission lines connected respectively between ad mission lines connected respectively between ad jacent radiator elements, individual means asso jacent radiator elements, a tuning condenser con ciated with each of said radiator elements to nected to each of said radiator elements to match match the impedance of each element to the the impedance of each element to the character characteristic impedance of one of said trans 60 istic impedance of one of said transmission lines, mission lines separately and independently of the and an opposed-phase coupling medium for said other radiator elements, and means for coupling antenna including a balancing network connect two oppositely disposed radiator elements in ed to two oppositely disposed radiator elements phase opposition to a utilization circuit for said and having an intermediate terminal connected antenna. to a utilization circuit for said antenna. 2. A turnstile antenna comprising, four equal 7. A turnstile antenna comprising, four equal length radiator elements located in the same length radiator elements located in the same plane and disposed at 90° angles with respect to plane and disposed at 90° angles with respect to one another, a pair of quarter wave length con one another, a pair of quarter Wave length con centric transmission lines connected respectively 70 centric transmission lines connected respectively between adjacent radiator elements. a reactance between adjacent radiator elements, a variable element associated with each of said radiator ele condenser connected to each of said radiator ele ments and adjustable to match the impedance of ments to tune each element for parallel resonance each element to the characteristic impedance of and to match the impedance of each element to one of said transmission lines, and opposed 75 the characteristic impedance of one of said trans 2,412,090 7 8 mission lines, and a coupling medium for said 0nd ‘condenser being connected to two oppositely disposed radiator elements, and said second con denser being connected to ground and-the Junc antenna including a network comprising an in ductor connected in series between a ?rst con denser having a reactance numerically equal to that of said inductor and a second condenser having a reactance numerically equal to one-half that of said inductor, said ?rst condenser and the junction point of said inductor and said sec tion point of said inductor and-said ?rst con-v denser being connected to a utilization circuit for 'said antenna. PAUL J. KIBLER.