DE2026699A1 - Antenna with circularly polarized radiation - Google Patents

Description

British Company of Bush House, Aldwych, London V. C. 2

Wn-mf May 19, 1970

Antenna with circularly polarized radiation.

The invention relates to a circularly polarized antenna Radiation and with four radiators arranged around a vertical line with mutually identical resonance frequencies, the axes of two Spotlights in one of two vertical, perpendicular to each other Laying levels and with the four radiators from a central feed point are fed from in phase quadrature, so that in each case two opposing radiators are fed in phase, while neighboring Radiators have a phase difference of 90 °.

Such an antenna is known as a turnstile antenna. However, circular polarization is less of an issue with it. »Because - if the antenna is used as a transmitting antenna - the receiver lie approximately in the plane of the four radiators forming the antenna, where the circular polarization cannot be seen by the receiver. However, a turnstile-like antenna has already been proposed, in which the circularly polarized radiation is perpendicular to the plane of the Radiator is used (DBGM 6 91 * f 736). However, this antenna delivers directed radiation, the aim of the invention, however, is to provide an omnidirectional antenna to create with circularly polarized radiation. In this context, an antenna is known that is used as a radiator via? Has dipoles, which are arranged around a common vertical axis and are inclined by a certain angle with respect to this axis (Jasik: Antenna Engineering Hand.Book, McCraw-Hill Book Company, Int., Section 17-12 and Figures 17-19).

009851/1372

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The structure of this antenna is rather complicated, the dimensions of the antenna are relatively large and all four radiators of the antenna must be fed with different phases.

The object of the invention is therefore to provide an improved and structurally very simple antenna to create without the specified shortcomings, which is essentially circular polarization, an approximately circular horizontal diagram, and a good approximation of a fan-shaped vertical diagram.

The solution to the problem is characterized by that in the first claim Invention given, the features of which can be summarized as follows: Contains the antenna according to the invention for circularly polarized radiation four, preferably cylindrical, radiators, all of which are in resonance at the same frequency. Two of the emitters have their axes in one vertical plane, and the other two have their axes in one second vertical plane perpendicular to the first. Included stand the two spotlights perpendicular in the same vertical plane on each other. All radiators are directed away from a centrally arranged feed point and are fed in such a way that two are in phase with each other and the other two are also in phase with each other are in phase, but in phase quadrature with respect to the first "two" Radiators, with two radiators in each case, which are in phase quadrature to each other stand alternately in vertical planes that are perpendicular to each other.

In an advantageous further development of the invention fee, the four radiators are fed by a centrally arranged symmetrizing element, from which they point away from one another in a perpendicular manner and are directed downwards at an angle of ^ 5 ° with respect to the vertical. -.-...-. ■, ■,.,.: -: ■ - <;,. "-— · - ■ -

0 9 8 5! / 1 37-2-

The dimensions of the antenna are not critical. A preferred arrangement includes four cylindrical radiators, each about one sixth of the operating wavelength in length, each Radiator X has a circular cross-section with a diameter of approximately one fifth of the radiator length. Experimental accounts with a Antenna with the following dimensions good results can be achieved, where Λ means the operating wavelength:

Radiator length 0.16 / \, radiator diameter 0.032 λ, length of each coaxial line from the balancing element to each radiator 0.012 "K.

An exemplary embodiment of the invention is explained in more detail with the aid of the figures explained. FIG. 1 shows a plan view and FIG. 2 shows a view of the antenna, while FIG. 3 shows the vertical radiation diagram.

In Figures 1 and 2, the parts for in-phase supply are inside the radiators 2 and * f shown with broken lines. The ground is indicated in FIGS. 2 and 3 by the position symbol G marked.

The antenna shown contains four similar radiators 1, 2, 3 and k, each of which is hollow cylindrical. The radiators 1 and 3 lie in a vertical plane, while the radiators 2 and k lie in another vertical plane which is perpendicular to the former. The axes of the radiators, which lie in the same vertical plane - radiators 1 and 3, or radiators 2 and k - are perpendicular to one another. All four radiators point away from a central feed point which is formed by the upper end of a balun 5.

In addition, the four radiators are directed downwards at an angle of k $ with respect to the vertical from the central feed point.

-A-

0098 5 1/1372

As can be seen from FIG. 1, the radiators 1 and * f are fed jointly, something that also applies to the radiators 2 and 3. The electrical feed arrangement inside the radiators 2 and h causes an electrical phase shift of 90, so that the radiators 1 and 3 are fed in a phase position which is perpendicular to the phase position of the radiators 2 and k .

Since the longitudinal axes of the radiators 1 and 3 form an angle of 90 with each other, within the vertical plane in which they lie, the vertical radiation diagram of the electric field strength in the free tree would have almost no preferred direction. Strictly speaking, it would be essentially elliptical in shape. The same applies to the radiators 2 and FIG. 3 shows the true vertical radiation diagram for the radiators 1 and 3, which are arranged above the ground G. For the radiators 2 and k _t which are tuned to the same frequency, however, the radiators 1 and 3 * are fed in phase quadrature to the radiators 1 and 3, a corresponding radiation diagram results. Because of the phase quadrature, however, the four radiators taken together generate a rotating electric field strength vector, ie a circular polarization.

The dimensions shown in Figure 2 have been chosen to allow a large bandwidth. ( X means the operating wavelength) The antenna is fed by a coaxial cable 7 which leads to the balun 5 so that it is easy to connect the antenna to a 50 - or 75-ohm feeder cable.

The vertical radiation diagram can be adapted to the requirements by changing the height of the antenna above the ground G.

The antenna can, for example, be a shortwave omnidirectional antenna to be used.

009851/1372

Claims (3)

Claims 1) Antenna with circularly polarized radiation and with four radiators arranged around a vertical line with the same resonance frequency as one another, whereby the axes of two radiators lie in one of two vertical planes that are perpendicular to one another and the four radiators are fed in phase quadrature from a central feed point so that two opposite radiators are fed in phase, adjacent radiators have a phase difference of 90, characterized in that two radiators (1,3 or Zyk) located in one of the vertical planes enclose an angle of 90 °. 2) Antenna according to claim 1, characterized in that the four radiators (1 to h ) are fed by a centrally arranged balun (5) and extend from this downward in a direction which is inclined k5 ° with respect to the vertical 3) Antenna according to claim 1 or 2, characterized in that the lengths of the radiators (1 to k) are approximately equal to one sixth of the operating wavelength (λ) and that each radiator (1 to k) is cylindrical and has a diameter of approximately one fifth having its length. 0 0 9 8 5 1/13 7 2 Blank page