US2341558A - Marker beacon - Google Patents

Description

Patented Feb. 15, 1944 MARKER BEACON Armig G. Kandoian, New York, N. Y., assignor to Federal Telephone and Radio Corporation, a corporation of Delaware Application March 25, 1942, Serial No. 436,172

'2' Claims.

This invention relates to marker beacons and more particularly to vertical marker beacons intended to produce a vertical pencil-like beam.

It is often desired to produce a relatively concentrated beam of energy, for example, directed upwardly from the earth as a marker beacon. Such systems usually comprise an array of -antenna units in order to secure the desired concentration. One form of array proposed for marker beacons comprises a plurality of dipole antennae arranged at right angles with respect to one another and energized in phase quadrature.

It is an object of my invention to provide the type of array mentioned above in which energy may be supplied thereto in impedance matched relationship with a comparatively simple feeding network.

It is a further object of my invention to provide a marker beacon array which will have the desired sharpness of directivity.

With these and other objects in mind my invention features an antenna array in which dipole units are arranged in arrays at right angles to one another and are energized in phase quadrature by a line connected to both arrays, the line referably being matched in impedance by the array units and connections therewith.

A better understanding of my invention and the objects and features thereof may be had from the particular description thereof made with reference to the accompanying drawings in which:

Fig. 1 shows the simplest form of antenna array and circuit embodying my invention;

Fig. 2 shows a more complex array arrangement;

Fig. 3 shows the circuit connections. of the arrangement of Fig. 2 embodying my invention, and

Fig. i is a diagram illustrating an array arrangement suitable for use with my invention.

Fig, 1 illustrates a preferred form of my invention. In this figure two pairs of dipolesv 10, ii and i2, I3 are supported on posts M a short distance above the earth. Each of the dipoles Hi, i 1, i2 and I3 is made electrically a half Wavelength long and the pairs are preferably spaced apart a half wavelength. At the ends of each pair of dipoles Hi, H and I 2, 13, are provided so-called building out sections l5, l6, which are substantially quarter wavelength transmission line sections short circuited at one end. Intermediate the ends of sections l5, I6, is connected a coupling line H. Line I1 is connected to the antennae sections to supply energy to the dipole pairs and is adjusted so that the impedance looking into the line from the supply source is sub-- stantially equal to the characteristic impedance of the transmission line 29 serving to feed the antenna units.

At right angles to and supported on the same posts I are provided two other pairs of antennae Zii, 2| and 22, 23, provided with short circuited quarter wavelength line sections 25, 26, and interconnected by a transmission line 21 also adjusted to furnish an impedance match for the antenna feeder line. Lines I1 and 21 are interconnected by lines I8, 23, line 28 being made preferably electrical degrees'longer than line 58, so that the antenna pairs Ill, Ii, l2, l3, and 28, 2|, 22, 23 are energized in phase quadrature. Since the impedance at lines H and 21 are each equal to the characteristic impedance of the feeder transmission line 29, it is clear that when the lines are interconnected at the junction of i8 and 28, there will be a mismatch of substantially 2:1 on line 29. This may be readily taken care of by coupling to the line an impedance matching network illustrated at 19. Energy for the beacon may be applied from the high frequency translatcr unit 30.

It is clear that other phase shifting means than the transmission line 28 may be provided to secure the desired phase quadrature energization of antenna units. However, the simplest form of phase shifter comprises a length of line as shown and this is generally preferred since it does not then require additional compensation for reflections that might be caused by other forms of impedance networks,

While Fig. 1 illustrates the simplest form of my invention and the one that is generally preferred, it is sometimes desirable to sharpen the directivity of an array so as to produce a more concentrated beam. This may be particularly useful in certain types of marker beacons where it is desired that the beam indicate as nearly as possible a single point' To secure such beams it is merely necessary to add units equally spaced at halfwavelength distance as in the arrangement of Fig. l, and to energize these units in accordance with the coefiicients of a binomial expansion.

In such case it is merely necessary that even numbered pairs of antennae be provided so that energization at the ends of the dipole units as in Fig. 1, may be accomplished.

In Fig. 2 is illustrated, by way of example, a binomial array of units wherein four antennae are provided in each direction. Thus, there are shown two pairs of antennae 3H, 32, crosswise aligned with six other pairs, 33, 3t; 35, 36; and 31, 38. As in the case of Fig. Leach of the units of the pairs is made one-half a wavelength long and the spacing between the parallel antenna pairs is made also equal substantially to a halfwavelength. At right angles to these antennae are arranged eight other pairs of units 4 I, 42; 43, 44; 45, 46; 41, 48. The wiring of these units is not shown in Fig. 2 since this is quite complex, but is illustrated particularly in Fig. 3.

In this figure the two sets of antennae 3|--38 and 4l-48 are shown separately. Pairs 3f, 32, 31 and 38 are fed with energy so as to have one unit of current in the antenna, while pairs 33, 34, 35 and 36 have three times the current of the outer pairs. Similarly, pairs 4 I, 42, 41 and 48, have only one-third of the energization'of'pairs 43, 44, 45'

and 46. This, then, gives the-normal distribution for a four-unit binomial array for each of the systems, that is, a 1, 3, 3, 1 distribution. Antenna pairs 3!, 3'! are interconnected by a bridging conductor 5i, while pairs 32, 38 are connected by bridging conductor 52. Pairs 3,- 35 are connected together by bridging conductor 53, while pairs in, 35 are interconnected by bridging conductor 54. It will be noted that conductors 5f, 52 are connected at a point on the short circuited transmission line sections of the associated antenna pairs so as to deliver to these units a much smaller amount of current than is delivered by lines 53 and 54. Coupling conductors 5!, 52 are interconnected by a further conductor. 55. Also, conductors 53, 54 are interconnected by a common interconnecting conductor line 55. Preferably, lines 55 and 55 are adjusted so as to in themselves together with the antenna loads constitute substantially an impedance match to the feeding transmission line. However, in event this cannot easily be arranged, impedance matching means may be applied to the lines to produce this result. Interconnecting conductors 55, 55 are then connected together through transmission lines, so that all of the antenna units 33 to 38, inclusive, are energized in phase coincidence. If transmission lines 55 and 56 are each matched to the impedance of the transmission line, an added network 5'! may be required at a point beyond the juncture for matching the impedance of the combination to the transmission line.

Antenna pairs 4! to 48, inclusive, are interconnected by a set of interconnecting transmission lines 6|, 62, 63, 64 and 66, similar to the corresponding lines 5| to 56, inclusive, and may be matched by an impedance matching section 6'! similar to section 51. The two sets of antenna pairs 3! to 38, and 4| to 48, are then connected over separate transmission lines 58 and 68 to the common feed line 10 connected to high frequency transmitter H. Line 68, for example, is preferably made a quarter of a wavelength longer than line 58 so that the antenna pairs 3! to 38, and 4! to 48 are energized in phase quadrature. The impedance matching section 69 may be provided in line H! to correct for the 2-1 standing wave present on line 10 because of the connection together of two impedance, matched. lines 58 and 68.

In Figs. 1 and 2 have been shown two forms of arrays suitable to perform the function in accordance with my invention. It is clear that any binomial expansion array may be provided as desired, depending upon the sharpness that the beam is to assume. However, both Figs. 1 and 2 illustrate systems in which the arrays are made of an even number of spaced antennae. It is clear that the same features of my invention may be readily applied to arrays having odd numbers of antenna therein.

In Fig. 4 is illustrated a three-element array to show the form that the units will be arranged in such a case. In this figure dipole pairs BI, 82, 83 and 84, 85, 86 are arranged as shown, with the ratio of energization being 1-2-1 across the array. At right angles to these are added other pairs of dipoles 9|, 92; 93 and 94, 95, 35, also energized in the ratio of 1-2-1, that is in accordance with the coefficients of a binomial expansion. Each of these pairs 8l-86 and 9l-96 actually constitute two half-wave dipole units similar to those shown at Ill and II of Fig. 1. Also, these units are then interconnected by transmission lines in a manner similar to that shown in Figs. 1 and 3. The actual connections of the circuit are not shown, since it is considered that the two examples already given adequately illustrate how interconnection can be made. In this case it is clear that antenna pairs 8!, 83, t4 and 86 would be interconnected similar to the interconnection of 3|, 31; 32, 38 of Fig. 3, and then units 82, would be interconnected-in a manner similar to the interconnection of tie-line 53 and 54, and the whole then connected to a transmission line for co-phasial energization. In a similar manner the connection between the antenna units 9|96 would be made. I Any number of antenna may be arranged in a binomial expansion series in a manner outlined herein, withoutdeparting from the spirit of my invention. Furthermore, it is clear that in the array as illustrated in Fig. 2, if desired, only units 3!, 33, 35 and 3?, and right angularly-arranged units 4!, 43; 45 and 4'! might be used, if desired, instead of the array of 16 units as shown. In such a case it would be better to shift the arrangement so as to produce a symmetrical pattern, but this is not essential to the operation.

It is clear that while I have disclosed preferred embodiments of my invention, many variations thereof will occur to those skilled in the art without departing from the spirit of my invention. The essential feature of my invention is the provision of dipole units arranged in pairs so that the entire system may be simply connected together for feeding.

What I claim is:

1. A marker beacon comprising a plurality of antennae arranged in a first array, a second plurality of antennae arranged in a second array similar to said first array but at right angles thereto, a transmission line, means for energizing said antennae of each array in accordance with the coefiicient of a binomial expansion, and said arrays in phase quadrature, comprising first means connecting the antennae of said first array together to produce an impedance equal to the characteristic impedance of said transmission line, second means connecting the antennae of said second array together to produce an impedance equal to the characteristic impedance of said transmission line and a ninety degree phase shift with respect to said first array, said transmission line being connected to both said first and second means, and means in said transmission line near said connection point for matching the impedance of said two means to said transmission line.

2. A marker beacon comprising a plurality of dipole antennae arranged in a first array, a second plurality of dipole antennae arranged in a second array similar to said first array but at right angles thereto, a transmission line, means for energizing said dipole antennae at each array in accordance with the coeflicient of a binomial expansion, and said array in phase quadrature,

comprising first means connecting the ends of said dipole antennae ofsaid first array together to produce an impedance equal to the characteristic impedance of said transmission line, second means connecting the ends of said dipole antennae of said second array together to produce an impedance equal to the characteristic impedance of said transmission line and a ninety degree phase shift with respect to said first array, said transmission line being connected to both said first and second means, and means in said transmission line near said connection point for matching the impedance of said two means to said transmission line.

3. A marker beacon system comprising a high frequency transmission line, a first two dimensional antenna array comprising at least two rows of dipole antennae spaced apart a distance substantially equal to a half wavelength, each row comprising at least one pair of half wave dipole antennae arranged end to end, first means interconnecting the adjacent ends of each said pair and all the pairs of said first array, said first means as connected being adjusted to present the characteristic impedance of said line, a second two dimensional antenna array comprising at least two rows of dipole antennae arranged at substantially right angles to said first array and spaced from one another a distance substantially equal to a half wavelength, each row comprising at least one pair of half wave dipole antennae arranged end to end, second means interconnecting the adjacent ends of said pairs in said second array and all the pairs of said second array, said second means as connected being adjusted to present the characteristic impedance of said line, means for connecting said first and second arrays to said line to energize said arrays in phase quadrature, and means in said line for matching the impedance of said combined array to said transmission line.

4.. A marker beacon according to claim -3, wherein more than two rows are provided and energy is supplied to the dipoles of the rows at a level diminishing from the center outwardly in accordance with the coefiicients of the binomial expansion.

connected at their adjacent ends by a first short circuited quarter wavelength line section, a second pair of dipoles parallel to said first pair and spaced substantially a half wavelength from said first pair, said second pair of dipoles being arranged end to end and interconnected at their adjacent ends by a second quarter wavelength transmission line section, a first connection means for interconnecting said first and second transmission line sections, a third pair of dipoles substantially at right anglesto said first and second pairs and arranged end to end and interconnected at their adjacent ends by a third short circuited quarter wavelength transmission line section, a fourth pair of dipoles parallel to said third pair and spaced substantially a half wavelength from said third pair, said fourth pair of dipoles being arranged end to end and interconnected at their adjacent ends by a fourth short circuited quarter wavelength transmission line section, a second connection means interconnecting said third and fourth transmission line section, a transmission line, and means differing in electrical length by a quarter of a wavelength for connecting said first and second connection means to said transmission line to assure phase quadrature relationship of energization for said first and second pairs of dipoles with respect to said third and fourth pairs.

7. A marker beacon according to claim 6, wherein said first and second connection means and associated dipoles are each equal in impedance substantially to the characteristic impedance of said transmission line, further comprising means in said transmission line for correcting the mismatch of impedance caused by the connection of said transmission line to said first and second connection means.

ARMIG G. KAN'DOIAN.

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