US 3808600 A
An aerial formed of two vertical conductor lengths extending perpendicularly to a ground plane, a conductive disk in which are provided two holes through which the vertical conductor lengths respectively pass, and two horizontal conductor lengths extending from the ends of the vertical conductor lengths above the conductive disk into contact with the conductive disk. The vertical conductor lengths extend to a height of about lambda /12.
Description (OCR text may contain errors)
a v u l- I United States Patent 1191 Bourdier Apr. 30, 1974 RADIOELECTRIC AERIAL  Inventor: Jean Bourdier, Lannion, France r' Borchelt Assistant Examiner-Marvin Nussbaum gn I 06 618 Lannionnaise DElectronique Attorney, Agent, or; Firm-Craig and Antonelli Sle-Citerel, Lannion, France 1  Filed: Dec. 22, 1972  Appl. NO.: 317,760 57 7 ABSTRACT  Foreign Application Priority Data An aerial formed of two vertical conductor lengths ex- Dec. 22, 1971 France 71.46209 tending perpendicularly to a ground Plane, 8 e0hdue- 1 tive disk in which are provided two holes through 52 11.8. CI 343/830, 343/847, 343/848, which the vertieal conductor lengths respectively pass, 3 3 349 343 72 and two horizontal conductor lengths extending from  Int Cl o 9 3 HOlq 42 HOlq 1 4 the ends of the vertical conductor lengths above the  Field f Seal-chm 343 329 330 345 4 47 conductive disk into contact with the conductive disk. 3 3 34 7 5 70 71 713 72 The vertical conductor lengths extend to a height of about )t/12. 1 [5 6] References Cited UNITED STATES PATENTS 3/1947 Wehner .[343/830 X 10 Claims, 9 Drawing Figures PATENTED APR 3 0 1974 SHEET 1 [IF 2 PATENTEDAPRBO m4 3;808;60'0
sum a nr 2 FlG.4c1
RADIOELECTRIC AERIAL The invention comes within the branch of transmitting and receiving aerials for metric or decimetric waves. It concerns an aerial having slight bulk, strongly built, and having self-adapted input impedance. It applies mainly to radio-electric equipment for mobile craft (aircraft, automobiles).
It is essential for aerials for mobile craft to have as little height as possible. For anaircraft, an aerial which is too long increases drag; for an automobile a long ae-. rial must be dismantled before the automobile passes through a modern washing station. I
An aerial of'the whip type having a height comprised between 0.25)\ and 0.5L ()t wavelength), being considered as excessive, various means have been proposed for reducing it:
A helical aerial, which has the disadvantage of being too selective, and for that reason, is difficult to produce on an industrial scale. A single pole aerial having an end charge, which has the disadvantage of having such a low impedance at the feed point that it requires a high-ratio feed transformer which is consequently expensive.
The aerial according to the invention comprises,
above a conductive surface, forming a ground plane,
two vertical lengths which cross a metallic plate forming a counterweight, extend each other at a slight height above the said plate by two horizontal lengths whose upturned ends are welded to the said plate. One of the vertical lengths rests directly on the said conductive surface, the other crossing. it by means of an insulated bushing which may have-a coaxial cable fitted to it. For a height of the vertical lengths in the order of M12, the impedance on the said bushing may easily be brought to 50 ohms with appropriate values of the other geometrical parameters.
It will be shown that for a verticallength equal )t,,/ 12, that is, a very slight height, the impedance at the feed point is in the order of 50 ohms, and therefore js adapted directly, without any transformer, to a coaxial feed line. 1
An aerial according to the invention will be described with reference to the accompanying drawings, among which:
FIGS. la, lb, 1c are various views of an aerial according to the invention. FIG. la is a perspective view, FIG. lb is a front view, FIG. 10 is an end: view;
FIG. 2 is the equivalent wiring diagram;
FIGS. 3a, 3b, 3c are views of another embodiment of the aerial according to the invention;
FIGS. 4a and 4b are views of a radome configuration.
Elements 1 and 2 are two vertical lengths perpendicular to a conductive ground plane 3. The length 1 is welded at 5' to the said ground plane. The length may be connected by a bushing 4, placed below the plane 3, to a coaxial line 4'. A conductive plate 6, for example, a. metallic disk, forming a counterweight held at a certain height above-the ground plane 3- by insulated support means, not shown, is crossed by the length I through a hole 7, and by the length 2 through a hole 8.
Above the disk 6,. the vertical length I iscontinued at P by a horizontal conductor 9'; the vertical length 2 is continued at Q by a horizontal conductor 10 parallel to the conductor 9and having a same length. The horizontal conductor 9- ends in a short vertical conductor 11 whose end 13 is welded to the disk 6. The horizontal conductor 10 is ended by a short vertical conductor 12 whose end 14 is welded to the disk 6, which is thus held above the ground plane 3.
. The conductors 9 and 10 form, with the disk 6, two lines of characteristic impedance Z,,, the impedance at P (or at Q) being Z, (or Z where Zp Z The height of the disk 6 above the plane 3 is designated by h; the length of the horizontal conductor I0 is designated by 1, the height of the horizontal conductor l0'above the disk 6 is designated by u, the diameter of the pass hole 8 has a value of qb.
The lengths have a diameter of d, their spacing has a value of m, the disk has a diameter of D.'The three main parameters are: h, D, u, l. The secondary parameters are d, m, (I).
The optimum values of the parameters are shown herebelow in the left-hand column. For a wavelength of )t 67 cm (frequency f 450 Mc/s) the values marked in the right-hand column are obtained.
FIG. 2 The equivalent diagram comprises, starting from a point B, showing the short-circuit between the horizontal conductors 9 and 10, an induction L of the conductor 9, an induction L of the conductor 10, a capacitor C of the disk 6 and lengths l and 2 in relation to the ground plane.
Ll is the induction of the length l and R1 is its radiation resistance and loss resistance; L2 is the induction of the length 2 and R2 is its radiation resistance and loss resistance. A is the feed point.
The result obtained is Justification The detailed calculation of the impedance at the point A, Z,,, which will not be reproduced in detail, to lighten the description, shows that by cancelling the reactive term in the expression of Z,,, two resonant frequencies 0,, (0 are found, the squares of these having for their expression:
In the condition R QFC (1 LCM) there is a third resonant frequency, which is, in fact, the true tuning frequency of the aerial m given by (m 3/(2LC).
At the tuning frequency (0 the calculation shows that the impedance 2,, at the base of the aerial has a value: Z, 5R.
For lengths l and 2 equal to M12, the resistor R is equal to 10 ohms; therefore, the result obtained is 2,, 50 ohms, a value which is a great advantage, which enables a direct connection on a coaxial feed line having a characteristic Z equal to 50 ohms.
Experience shows that, in these conditions, by shortcircuiting two points situated at the same distance on the conductors 9 and 10, the impedance Z A is not moditied: this confirms that the currents in the lengths I and Zo I50 Q 138 log (4u/d) The theoretical isotropic gain is in the order of 5 dB. The relative pass band for a proportion of stationary waves less than 2 is about 7 percent.
FIGS. 3a, 3b, 3c These figures show a version of the aerial according to the invention affording a great advantage, in which-the upper part, the disk 6 and the conductors 9 and 10 are replaced by metallic deposits on the two faces of an insulating substrate, for example epoxy glass. FIG. 3a is a front view; FIG. 3c is a plan view of the upper surface of the disk, whose lower face 23 is copper plated all over; FIG. 3b is a detailed drawing on a larger scale.
The insulating disk is designated by 21, the upper conductors, by 19 and 20 respectively, the shortcircuits between the conductors 19, 20 and the lower face of the disk by 22, 22'. Contact is ensured between the lengths l (2) and the conductors 19 (20) by a connection 24.
FIGS. 4a, 4b The aerial assembly according to the invention may be housed in a radome which is shown in FIG. 4a.
The radome comprises a hood made of insulating material 30 having an approximately generally hemispherical shape, whose bottom is formed by a metallic disk having an upturned edge 32 which is embedded in the lower edge 31 of the hood 30.
At the upper part, a disk made of epoxy glass, such as 21, bearing conductors l9 and 20 (FIG.'3b) is fixed by centering pins 33, 34. Two lengths l and 2, one of which is connected by galvanic continuity at 5 to the base of a coaxial bushing fixed to the metallic plate 32, the other to an insulated conductor in the center of the coaxial bushing 35, rise from the base 32 towards the disk 21.
The assembly is fixed, for example on the sheet metal roof of a vehicle 36, forming a ground plane, by means of parts 37, 38, for example nuts and bolts.
FIG. 4b is a plan view of the disk 21 with its attached parts. The traces of the fixing pins 33, 34 are noticeable thereon.
The radiating lengths may be inclined in relation to the vertical in order to bring the center of gravity of the assembly towards the axis, as is visible in FIGS. 4a, 4b.
It must be understood that the radome could also be provided with an aerial having a copper disk according to FIG. la.
The practical height, including the radome is less than k/IO.
The aerial is completely protected against static charges, since it is galvanically connected to the ground.
The pass band of the aerial is increased by increasing the radius of the conductive surface.
That conductive surface does not necessarily have a circular shape. For installing on aircraft, it is, to great advantage, given a streamlined shape, as is the radome, to reduce drag.
What is claimed is:
1. A radioelectric aerial for metric and decimetric waves to be installed above a conductive ground plane, comprising first and second conductors of equal length extending substantially vertically in parallel above said ground plane, said first conductor being connected at one end to said ground plane and said second conductor being insulated therefrom, a plane disk supported above said ground plane at a distance approximately equal to the length of said first and second conductors whose ends extend through apertures in said disk, third and fourth conductors extending perpendicularly from said first and second conductors, respectively, at the side of said disk opposite said ground plane, the free ends of said third and fourth conductors being bent vertically into contact with said disk.
2. A radioelectric aerial as defined in claim 1 wherein said plane disk is made of metal.
3. A radioelectric aerial as defined in claim 2 wherein said third and fourth conductors are spaced from the surface of said disk by distance corresponding to the wave-lengths to be received and transmitted.
4. A radioelectric aerial as defined in claim 3 wherein said first and third conductors are formed by a single continuous conductor which is bent subsequent to passing through said disk and said second and fourth conductors are formed by a single conductor which is bent subsequent to passing through said disk.
5. A radioelectric aerial as defined in claim 2 wherein the impedance from the end of said second conductor adjacent said ground plane is approximately 50 ohms while the length of said first and second conductors is approximately M12.
6. A radioelectric aerial as defined in claim 5 wherein a coaxial pin extends through said ground plane and is connected to the end of said second conductor to provide a feed input and output connection for the aerial.
7. A radioelectric aerial as defined in claim 1 wherein said plane disk is made of insulating material having a conductive coating disposed over substantially the entire surface thereof facing said ground plane and to which the bent ends of said third and fourth conductors are connected through said disk.
8. A radioelectric aerial as defined in claim 7 wherein said third and fourth conductors are plated on said disk.
9. A radioelectric aerial as defined in claim 1 wherein said .disk is supported by the upper part of a radome supported on said ground plane.
10. A radioelectric aerial as defined in claim 9 wherein said first and second conductors are slightly inclined to the vertical inside said radome.