Antenna provided with an assembly of filtering materials

Details Antenna provided with an assembly of filtering materials Antenna provided with an assembly of filtering materials

2001-07-18

2003-04-15

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

With polarization filter or converter

C343S909000, C333S202000

Reexamination Certificate

active

06549172

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a transmitting or receiving antenna which attains high levels of directivity at frequencies in the microwave range.
Antennas are known which comprise at least one probe capable of transforming electrical energy into electromagnetic energy and vice versa.
Nowadays, the antennas conventionally used are, in particular, parabolic reflector antennas, lens antennas and horn antennas.
Parabolic reflector antennas comprise a reflecting plane which is parabolic in shape, at the focus of which is located a probe. This requires the antenna to be of a certain size related to the focal length of the parabolic reflector.
Lens antennas comprise a lens at the focus of which is located a probe. Apart from the considerable size caused by the focal length, an antenna of this kind is also heavy, owing to the weight of the lens, and this weight may be prohibitive for certain applications.
Horn antennas have to be bulky and heavy to achieve high levels of directivity.
SUMMARY OF THE INVENTION
The invention sets out to overcome the disadvantages of conventional antennas by creating an antenna which is less bulky and lighter, while being capable of transmitting or receiving an electromagnetic wave with high levels of directivity.
The invention thus relates to an antenna comprising at least one probe capable of transforming electrical energy into electromagnetic energy and vice versa, characterised in that it further comprises an assembly of elements made of at least two materials differing in their permittivity and/or permeability and/or conductivity, within which said probe is arranged, the arrangement of the elements in said assembly ensuring radiation and spatial and frequency filtering of the electromagnetic waves produced or received by said probe, said filtering allowing in particular one or more operating frequencies of the antenna within a frequency band gap.
This antenna consequently allows a reduction in size and weight by using a simplified feed system and a thin assembly of elements made of materials differing in their permittivity and/or permeability and/or conductivity.
The antenna according to the invention may also have one or more of the following features:
Said assembly of elements has a periodicity with at least one dimension in its structure and at least one defect which generates at least one cavity inside it.
Said assembly of elements comprises a first material of a given permittivity and permeability and conductivity, forming a cavity inside a structure of two other materials which differ in their permittivity and/or permeability and/or conductivity, said structure having a triple periodicity in three distinct spatial directions of the other two materials.
Said assembly of elements comprises a first material of a given permittivity and permeability and conductivity, forming a cavity inside a structure of two other materials which differ in their permittivity and/or permeability and/or conductivity, said structure having a double periodicity in two distinct spatial directions of the other two materials.
Said assembly of elements is made up of flat layers of materials differing in their permittivity and/or permeability and/or conductivity.
Said assembly of elements comprises a first flat layer of material of a given permittivity and permeability and conductivity, inside which is arranged the probe, said first layer being in contact with at least a succession of flat layers of material differing in their permittivity and/or permeability and/or conductivity, arranged An a one-dimensional periodic pattern.
It further comprises a planar reflector of electromagnetic waves supporting said probe and placed in contact with said assembly of elements.
It comprises a metal plate on which is arranged a probe, said metal plate forming a planar reflector in contact with a first flat layer of material of a given permittivity and permeability and conductivity, the thickness e
1
of said first flat layer being given by the equation e
1
=0.5 (&lgr;/{square root over (&egr;
r
&mgr;
r
)}), said first layer itself being in contact with a succession of flat layers of materials differing in their permittivity and/or permeability and/or conductivity, the thickness e of each of said flat layers being given by the equation e
1
=0.25 (&lgr;/{square root over (&egr;
r
&mgr;
r
)}), where lambda is the wavelength corresponding to the operating frequency of the antenna wanted by the user, &egr;
r
and &mgr;
r
being, respectively, the relative permittivity and the relative permeability of the material of the flat layer in question.
The invention will be more easily understood from the description which follows, provided solely by way of example and referring to the accompanying drawings, wherein:


REFERENCES:
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Yang et al., “Photonic Band-Gap Materials for High-Gain Printed Circuit Antennas”, IEEE Transactions on Antennas and Propagation, US, IEEE Inc. New York, vol. 45, No. 1, 1999, pp. 185-187.

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