US3268896A

US3268896A - Flush mounted distributed-excitation antenna

Info

Publication number: US3268896A
Application number: US163178A
Authority: US
Inventors: Spitz Erich
Original assignee: Csf
Current assignee: Thales SA
Priority date: 1961-01-23
Filing date: 1961-12-29
Publication date: 1966-08-23
Anticipated expiration: 1983-08-23
Also published as: GB983458A; DE1226171B; FR1286732A

Description

m y mnss REFERENCE SEARCH mom g- 1966 E. sPrrz 3,268,896

FLUSH MOUNTED DI STRIBUTED-EXCITATION ANTENNA Filed Dec. 29, 1961 5 Sheets-Sheet 1 FIG.3

E. SPITZ Aug. 23, 1966 FLUSH MOUNTED DISTRIBUTED-EXCITATION ANTENNA Fi led Dec. .29, 1961 5 Sheets-Sheet 2 Aug. 23, 1966 E. SPITZ 3,268,896

' FLUSH MOUNTED DISTRIBUTED-EXCITATION ANTENNA Filed Dec. 29, 1961 5 Sheets-Sheet 5 has 5132 FIG.9 531:5?

United States Patent Oihce 3,268,896 Patented August 23, 1966 The present invention relates to distributed excitation antennas. More particularly, it is an object of the present invention to provide a distributed excitation antenna having an entirely homogeneous external structure.

The improved distributed-excitation antenna of the invention comprises two lines, an exciter line and a radiating line, having at least one conductive element in common, the coupling between the two lines being effected through said common element, and the external structure of the radiating line being perfectly homogeneous.

According to a preferred embodiment of the invention, the exciter line .comprises a metallic plate, and a lead extending in parallel relationship with said plate, this first assembly being equivalent to a two-lead line, the second lead being the mirror image of the first lead relative to said plate. The radiating line comprises, in addition to the metallic plate, a dielectric plate parallel thereto and located on the other side of said lead.

The invention will be best understood from the following description and appended drawings, wherein:

FIG. 1 is a perspective view of a distributed excitation antenna according to the invention;

FIG. 2 is a longitudinal, sectional view of the exciter line used in the antenna according to the invention;

FIG. 3 is a longitudinal, sectional view of the antenna according to the invention;

FIG. 4 illustrates a perspective view oi? a monopulse arrangement, comprising antennae according to the invention;

FIGS. 5 and 6 represent the radiation patterns of the antennae shown in FIG. 4;

FIG. 7 is a longitudinal section of an arrangement comprising the antenna according to the invention and adapted to radiate with a rectilinear or a circular polarization; and

FIGS. 8 and 9 are explanatory diagrams.

The antenna of the invention shown in FIG. 1 comp-rises a metal plate 1, a dielectric plate 2 parallel thereto, and a conductor line 3 in parallel relationship with plates 1 and 2 and located therebetween.

Let Oxyz be a reference trihedral, with 0 being the center of the cross-section of line 3, Oz parallel to line 3, and Oy perpendicular to elements 1-2. The parameters of the aerial shown in FIG. 1 are the following:

l=the thickness of the antenna, including the metal plate 1;

e=the thickness of the dielectric plate 2;

m =the distance between the axis of line 3 and plate 1; and

n=the diameter of line 3.

This assembly may be considered to be equivalent to two coupled lines. The exciter line comprises the metallic plate 1 and conductor 3. This line is equivalent to a twowire line 3-3, wherein 3' is the mirror image of wire 3 with respect to plate 1, as shown in FIG. 2. The lines of force of the electric field are arcs of circles passing through the respective centers of

lines

3 and 3.

The major portion of the electromagnetic energy is concentrated between conductor 3 and plate 1. It is known that the velocity of the energy along this line is the velocity of propagation of the electromagnetic waves in-space.

The radiating line comprises plate 1 and plate 2.

It is the seat of a guided wave in the TE-mode, the magnetic field of which has a component in the direction of propagation.

The propagation constant of this wave has a real portion ,8 substantially equal to the propagation constant of the waves in the air. This constant 5 may be written:

u=21re/ p being a coefiicient depending upon the distance d between plates 1 and 2.

Under the above conditions, the energy flowing through the excitor line is integrally transmitted to the radiating line.

It may be shown that, as a result, the radiating line radiates a field derived from the characteristic function:

f(x, y, z)=A. sin Cae he- (1) this lfunction being valid for y C designates the coupling coefficient of the two lines and depends on m and It, as well as the values L and L which designate the thickness of the layer where the enengy of the surface wave flowing along the dielectric plate 2 is concentrated in the absence of line 3 coupled thereto.

It may be shown that a complete transfer of energy takes place where both lines have a common length h Parameters L and L substantially define at a level 3 db below the maximum the width of the beam radiated in the planes Oyz and Oxy respectively. It may be shown that the widths are respectively chracterized by angles:

A01=)\/1I'L1 L and L; are of the order of a half wave length. It follows that, on receding from the Ox-axis, the field decreases very rapidly. The :ultra-high frequency field exists therefore only in a narrow area about conductor 3.

Formulae 3 define the widths of the radiation beam "in the planes x02 and yOz. The maximum radiating direction is not rigorously along axis oz if B differs from 18 If 5 is slightly higher than fil as is actually the case, the transfer of energy, prevailing in the exciter line, into the radiating line is not complete. This results in an efficiency decreases, and a portion of the ultra-high frequency energy in the exciter line has to be dissipated in a matched load. As mentioned above:

where then For e=A/40, 0=10 In one case, an aerial according to the invention had a length=10 0 was equal to 10 for a total thickness of the antenna l=0.15.)\.

FIG. 3 shows the method of feeding the antenna.

A coaxial line 6 has an external conductor 7 welded to plate 1 and its internal conductor welded to conductor 3. A transition element 8 between the conductor 5 and the conductor 3 prevents the occurrence of reflection, without making it necessary to use a balun device.

The line terminates in a matched load 9. of the transition element is about 10x.

The antenna according to the invention presents the following advantages:

(a) The external surface, i.e. the dielectric plate 2 has an homogeneous surface. It follows that the antenna may be incorporated into a body moving at a very high speed. In addition, this homogeneity results in its thermal properties being identical all over the surface area. Consequently, when a missile equipped with such an antenna penetrates the atmosphere, or close into the so-called heatbarrier; no specific problem would arise as it would be the case when the external structure had various expansion coefficients. In particular, the plate 2 may be of a refractory material, resisting to high temperatures.

(b) The fact that the electromagnetic field is localized in an area, close to conductor 3, makes it possible to use conductive and dielectric elements having cylindrically shaped surfaces, provided the curvature radius of these surfaces is higher, at least in the vicinity of conductor 3, than the operating wave-length.

FIG. 4 shows a unit built up from four antennae 'ac cording to the invention, mounted on a missile and used in a monopulse radar.

The cylindrical body 10 of the missile stands for the conductive plate 1 and is surrounded by a sleeve of dielectric material. The four leads 31, 32, 33 and 34 are parallel to the generatrices of the cylinder, their respective ends being located at the apices of a square. The direction of propagation Oz is the axis of the cylinder.

A dielectric body, having a dielectric constant close to unity may fill in the space between body 10 and sleeve 20.

The radiation patterns of the antennae built up by body 10, sleeve 20 and leads 31 to 32 are comprised in the plane yOz of FIG. 4; those of the antennae provided by body 10, sleeve 20 and leads 33, 34 are comprised in the plane ZOx.

FIGS. 5 and 6 illustrate, respectively, the radiation patterns of the aerial-s in the planes zOx and zOy. The parameters of the aerials make it possible to select the levels of the crossing of these patterns.

The wires 31 to 34 are connected in a manner known per se in view of delivering sum and difference signals, as well known in the monopulse art.

It is also possible to provide a circularly polarization by means of a system according to the invention, FIG. 7 illustrates such a system in a longitudinal sectional.

In this case,

conductors

31 and 32 are located in the plane of FIG. 7, in a conical portion placed at the head of missile 10. Similarly,

conductors

33 and 34, are located in a meridian plane, perpendicular to that of the figure.

These four aerials, on account of the fact that the summittal angle of the cone is selected to be equal to 0, have a maximum radiating direction along Oz.

Antennas

31, 32, 33 and 34 are fed in phase and the polarization of the energy transmitted by

antennas

31 and 32 is normal to that of the energy transmitted by

antennas

33 and 34.

FIG. 8 shows that the polarization of the resulting field is rectilinear.

If the groups of antennas 31-32 and 33-34 are fed in quadrature, the polarization is circular (FIG. 9).

The antenna according to the invention is particularly adapted to be used with high speed missile. It is of a simple construction and is directly fed by a coaxial cable. Its utilization in the monopulse system results in a highly simplified structure. Moreover, the dielectric of the antenna may serve as a protection for the missile upon its reentry into the atmosphere.

It is to be understood that the invention is not limited The length to the embodiments of the system described and illustrated, which were given solely by way of examples.

What is claimed is:

1. A distributed-excitation antenna for radiating ultrahigh frequency energy, comprising in combination: at least one first excitation line and at least one second radiating line, extending in parallel relationship; said lines having substantially the same propagation constant: said excitation line comprising at least one conductive element and a second element; said radiating line comprising said one conductive element and a further radiating homogeneous dielectric structure, said second element being disposed between said one conductive element and said radiating structure.

2. A distributed-excitation antenna for radiating ultrahigh frequency energy comprising a first excitation line, and a second radiating line, extending in parallel relationship, said lines having substantially the same propagation constant: said excitation line comprising a body made of a conductive material, at least one metallic wire extending in parallel relationship to said body in close vicinity therewith, means being provided for exciting ultrahigh frequency energy between said wire and said body; said radiating line comprising sad conductive body, and a further body made of a delectric material, extending in parallel relationship to said body, said two bodies enclosing said wire.

3. A distributed-excitation antenna for radiating ultrahigh frequency energy comprising a first exciting line, and a second radiating line, extending in parallel relationship, said lines having substantially the same propagation constant, said excitation line comprising a body made of a conductive material, at least one metallic wire extending in parallel relationship to said body, and in close vicinity therewith; means being provided for exciting ultra-high frequency energy between said Wire and said body; said radiating line comprising said conductive body, and a further body made of a dielectric material, extending in parallel relationship to said body, said two bodies enclosing said wire; said body and said further body extending in coaxial relationship, and having a curvature radius great with respect to the operating wavelength.

4. A distributed-excitation antenna for radiating ultrahigh freqeuncy energy comprising an excitation line and a radiation line extending parallelly to each other; said excitation line comprising a plate, made of a metallic material and a conductive wire extending parallely to said plate, in the close vicinity therewith; a coaxial line having an inner conductor and means for coupling said inner conductor to said wire, and an outer conductor coupled to said conductive plate; said radiating line comprising said plate and a further plate made of a dielectric material parallel to said conductive plate, said both plates enclosing said wire; the thickness of said further plate being small with respect to the operating wavelength.

5. A distributed-excitation antenna for radiating ultrahigh frequency energy comprising an excitation line and a radiation line extending in parallel relationship to each other; said excitation line comprising a plate, made of a metallic material and a conductive wire extending parallelly to said plate, in the close vicinity therewith; a coaxial line having an inner conductor and means for coupling said inner conductor to said wire, and an outer conductor coupled to said conductive plate; said radiating line comprising said plate and a further plate made of a dielectric material parallel to said conductive plate, said both plates enclosing said wire; the thickness of said further plate being small with respect of the operating wavelength; said coupling means between said inner conductor and said wire, comprising a transition element, both said lines having the same predetermined length.

6. A multiple distributed-excitation antenna according to claim 1, wherein said excitation lines comprise: a first conductive body in form of a truncated cone; four c0nductive wires respectively parallel to four generatrices of said cone, having respective ends at the apices of a square, and extending in the close vicinity and externally to said conductive body; means for exciting in a predetermined phase relationshship, ultra-high frequency energy between said conductive body and said wires; said radiation lines comprising: a second body in form of a truncated cone, made of a dielectric material, enclosing said first body and said wires, extending in coaxial relationship with said conductive body, in a close vicinity therewith.

7. A multiple distribution-excitation antenna as claimed in claim 1, wherein said excitation lines comprise: a first conductive body in form of a rotational cylinder; four conductive wires respectively parallel to four generatrices of said body, having respective ends at the apices of a square, and extending in close vicinity of and externally to said body, means for exciting in a predetermined phase relationship, ultra-high frequency energy, between said 6 body and said wires; said radiation lines comprising: a second body in form of a rotational cylinder, made of a dielectric material, extending in coaxial relationship with said conductive body in a close vicinity therewith, enclosing said first body and said wires.

References Cited by the Examiner HERMAN KARL SAALBACH, Primary Examiner.

E. LIEBERMAN, Assistant Examiner.

Claims

1. A DISTRIBUTED-EXCITATION ANTENNA FOR RADIATING ULTRAHIGH FREQUENCY ENERGY, COMPRISING IN COMBINATION: AT LEAST ONE FIRST EXCITATION LINE AND AT LEAST ONE SECOND RADIATING LINE, EXTENDING IN PARALLEL RELATIONSHIP; SAID LINES HAVING SUBSTANTIALLY THE SAME PROPAGATION CONSTANT; SAID EXCITATION LINE COMPRISING AT LEAST ONE CONDUCTIVE ELEMENT AND A SECOND ELEMENT; SAID RADIATING LINE COMPRISING SAID ONE CONDUCTIVE ELEMENT AND A FURTHER RADIATING HOMOGENEOUS DIELECTRIC STRUCTURE, SAID SECOND ELEMENT BEING DISPOSED BETWEEN SAID ONE CONDUCTIVE ELEMENT AND SAID RADIATING STRUCTURE.