Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1994-09-16
1996-07-02
Hajec, Donald T.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
343795, 343805, 343872, H01Q 916
Patent
active
055327079
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a directional antenna, in particular a dipole antenna, as generically defined by the preamble to claim 1.
Dipole antennas are often used as directional antennas to which there is a symmetrical power supply. In principle, this involves a symmetrical linear antenna that is horizontal or vertical, depending on the polarization of the electromagnetic waves, to which power is supplied in the middle. With dipoles offset by 90.degree. from one another, in the final analysis, even a circularly polarized electromagnetic wave can be generated.
The directional antenna, comprising one or more dipole antennas, typically includes one or more radiators, which substantially comprise the two dipole halves and the so-called symmetrizer loop, above which the dipole, typically comprising the two rod halves, is oriented offset, with a preliminary offset toward the reflector wall carrying it, but is oriented essentially parallel to it but also angularly thereto.
A directional antenna according to the prior art, formed from a dipole antenna, or dipole field for short, will be described with reference to FIGS. 10a-10c.
The directional antenna shown in FIGS. 10a-10c includes a dipole field 1, with two dipoles 3, for example, which are disposed in front of and spaced apart from a conducting flat or shaped reflector 5. In the example shown, the array accordingly includes two radiators 2, which are oriented parallel to one another and spaced apart by the distance a and are disposed in front of the reflector wall by a preliminary offset b.
The two dipoles 3 shown in FIGS. 10a-10c are held on the reflector 5 and secured by means of a so-called symmetrizer or balancer 7, which typically comprises two retention rods 7' that extend vertically to the reflector wall 5 and carry the dipoles 3.
The entire array is typically accommodated in protected fashion in a so-called radome 9, or in other words a so-called protective housing.
The radiation diagram in the E and H planes of a dipole field is determined essentially by the shaping and mechanical dimensions of the reflector and by the number and disposition of the dipoles.
In order to attain various directional characteristics, for instance in the known dipole antenna shown in FIGS. 10a-10c, both the reflector width c, in other words the width of the reflector wall 5, and the spacings a for the lateral offset transverse to the parallel-aligned dipoles 3 and the spacing b for the dipoles from the reflector 5 can all be varied.
For present-day mobile radio networks, directional antennas with vertical polarization are used, which have a horizontal directional characteristic of approximately 60.degree. to 120.degree. at the 3 dB point. These values can be achieved with one or two radiators in the array shown. However, the array comprising the dipoles 3, the symmetrizer loop 7 and including the connecting point 11 of the symmetrizer loop with the reflector 5, i.e. what is known as the base 11, and the preliminary offset must be optimized for each desired lobe width.
This means that when an antenna family is embodied in accordance with the desired lobe width, different radiators and various positionings on the reflector are required.
The described dipole antennas known from the prior art each include a plurality of individual parts, which must then be joined mechanically to one another. This is done by conventional joining methods, such as screwing, welding and soldering. The individual components for the dipole rods, the symmetrizer loop and the connecting points 11 for securing to the reflector may be tubular, generally flat, or shaped in some other way, depending on requirements. The individual parts are produced with the usual production tolerances. This is equally true for the structural unit in the assembled state,
Attention must be paid to the fact that the tolerances dictated by production conditions also affect the electrical properties (such as VSWR) of the individual radiator, and in a multi-radiator array they affect the impedance of the entire antenna.
For mass
REFERENCES:
patent: 2430353 (1947-11-01), Masters
patent: 5166697 (1992-11-01), Viladevall et al.
patent: 5229782 (1993-07-01), Hemmie et al.
Gottl Max
Klinger Georg
Hajec Donald T.
Ho Tan
Kathrein-Werke KG
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