Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1998-11-27
2001-03-20
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06204814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a planar emitter with an emitter plane equipped with planar resonators and a network plane equipped with a coupling network whereby the planar resonators are coupled with one another in-phase and galvanically via the coupling network.
2. Description of Related Art
Reflector antennas or planar antennas or planar emitters are used for communications services, particularly multi-point, multi-channel communications services, that require reception or emission of directed electromagnetic emission fields of linear polarization in the microwave spectrum. The emitter characteristics of the reflector antennas are based on the production of an appropriate amplitude and phase relationship of the electromagnetic emission field components on the reflector surface by means of suitable exciters. The reflectors used in this case are either in the form of closed surfaces of defined curvature and envelope or are laid out using gridlike arrangements of discrete conductive linear elements of defined length and spacing. Conventional planar solutions are based on the arrangement of galvanically and parallel fed planar resonators of defined group size and spacing of each one.
A planar array-antenna in strip-conductor technology is described in ES 0 200 819. The mechanical construction consists of a first substrate plate as the carrier for antenna elements and a second substrate plate as carrier for the coupler and signal processing. Both substrate plates are connected to each other via a thick metal plate whereby the thickness of the metal plate corresponds to the half of the operational wave length. The electrical connection between the antenna elements on the front of the antenna and the couplers on the back of the antenna produce coaxial conductors that are insulated and are passed through the passages in the metal plate.
A planar antenna is described in ES 0 383 292 in which the antenna elements are glued to the earthing surface of a double-layered circuit board on which the coupling network and the additional electronics are situated. The antenna element consists of a planar resonator plate which is mounted on a dielectric substrate layer. The substrate layer of the antenna element is made of “glass epoxy” which, however, because of its dielectric characteristics has a negative influence on both efficiency and bandwidth.
A planar antenna is described in WO 95/09455 which is similarly constructed in a sandwich-like manner and in which, for production reasons, the layers carrying the antenna consist of two layers of the same material, since the antenna elements are capacitative coupled.
A disadvantage found in the conventional planar antennas is that they all provide for the most part high system quality only in a small spectral range and consequently are suitable only with limitations for use for multi-point multi-channel communications services, since only relatively few frequency bands using a single antenna are transmissible because of the small bandwidth. Due to their construction some of the antennas described are very heavy or are made of very expensive materials in order to reduce their weight.
SUMMARY OF THE INVENTION
It is therefore the purpose of the invention to provide a planar emitter equipped with planar resonators that is simple, small in construction and consists of few, easily manufactured components while at the same time having high frequency dependent system quality with in the widest possible spectral range, in such a manner that it is suitable for a multi-channel point-to-point-transmission, especially in the frequency range between 2.500 GHz to 2.686 GHz.
This problem is, as described in the invention, solved by a planar emitter as described herein.
The planar emitter as described in the invention requires only a common earthing surface for the emitter and the network planes whereby the total height of the emitter as compared to conventional planar emitters is clearly reduced and the manufacturing material costs are also reduced. Also, without affecting the characteristic wave impedance of the coupling network, the band width of the emission field transmitted and received by the emitter can be varied by the appropriate selection of the thickness of the first dielectric layer, whereby and at the same time high system quality over the entire spectral range is achieved. In a planar emitter it is necessary that the first layer is made of a material with the smallest possible dielectric constant (r→1). The two-layered construction of the first layer makes it possible to manufacture the thin layer carrying the resonator surfaces out of a heat-resistant material; for example, polyethylene terephtalate upon which the resonator surfaces can be permanently placed. The thicker layer or the first layer can be produced using an economical foam material. In order that the planar emitter is flexible or pliable the thickness of the thick layer is greater than the thickness of the thin layer. The thick layer consequently forms the actual foundation material of the planar emitter and determines by its r and the attenuation [lit. “loss”] angle tan essentially the characteristics of the emitter layer. The material of the thick layer is optimally the inexpensive material polystyrol which in its foam form is flexible and particularly has a specific weight volume of 20 kg/m
3
. The thin layer is optimally formed using a polyethylene terephtalate film which is glued to the thick layer. The advantage of this polyethylene terephtalate film is that it engages copper in a strong and lasting bond whereby the resonator surfaces have a firm hold.
Each planar resonator is thus in electrically conductive connection, via an electrically conductive coupling pin, with the coupling network, whereby the electrically conductive coupling pin is installed in a drilled passage that is perpendicular to the emitter and network plane.
By the disproportionately large thickness of the first dielectric layer the coupling pins are relatively long, whereby the pins themselves have an electrically transforming effect. The inductive reaction components represented by the pin can therefore not be overlooked and must be compensated for. This can be done by means of a sheath that covers the pin at least sectionally and is made of a material, particularly Teflon, that has a higher dielectric number than that of the materials forming the dielectric layers serving at the basic material for the emitter and network planes. By means of the adjustment of the wall thickness, the height and the ∈
r
of the sheath the capacitance per unit length of the pin-sheath-combination can be adjusted whereby the inductive reaction component of the pin is compensated.
On the other hand, the compensation of the inductive reaction component of the pin can be beneficially achieved by taking advantage of the transforming effect of the length and width proportions of the micro-strip circuits used. Such transformations using micro-strip circuits are quite adequate as shown in the respective literature. In this case, if necessary, the sheath can be dispensed with.
It is furthermore necessary that the electrically conductive thin layer in the areas where the electrically conductive pins pass through the layer, have circular fenestrated recesses, such that the pins are not in electrical connection with the electrically conductive layer. These circular fenestrated recesses form orifices, where the coupling coefficient is adjustable by using the diameter of the recesses. The coupling coefficient thereby determines the portion of signal intensity that is conducted from the emitter plane to the network plane. The optimal diameter of the apertures is obtained by simulation or experimental tests.
In order to make the planer emitter flexible or elastic there is the possibility that the first dielectric layer is constructed of two dielectric materials that each on its own part forms a layer. In this case, the thickness of the first layer is greater than the thickness
Le Hoang-anh
Woodbridge Richard C.
Woodbridge & Associates P.C.
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