Patch antenna

Communications: radio wave antennas – Antennas – Microstrip

Reexamination Certificate

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Reexamination Certificate

active

06285326

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna of the microstrip type for transmitting and receiving waves of wave-length &lgr; belonging to the frequency band ranging from 100 Mhz to 6 Ghz and presenting in particular excellent transmission and reception characteristics in the 3.5 Ghz bands, the C band and S band.
2. Description of Related Art
Microstrip antennas are well known. They are most often constituted by a first metallic plate forming a ground plane and by one or more other metallic plates disposed opposite the ground plane and which constitute radiator patches. These two metallic plate/patch systems are most often fixed on the opposite faces of a block of dielectric material, thus ensuring in addition the mechanical connection between the ground plane and the radiator patch or patches.
However, such a system may become expensive, in particular due to the cost of the high-quality dielectric material when the radiator patch or patches present a relatively large surface area.
To overcome this drawback, it has been proposed to use as dielectric the air located between the ground plane and the radiator patch. In the case of a single radiator patch, this solution is already very delicate to implement insofar as it is difficult to hold the radiator patch in a precise position with respect to the ground plane and to ensure a mechanical connection between these two plates which can withstand outside stresses. This problem is rendered even more complex in the case of the radiating part of the antenna having to comprise a plurality of metallic patches since the latter must be maintained strictly in the same plane.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a microstrip antenna using the air as dielectric material, while avoiding the drawbacks mentioned above, particularly concerning the mechanical structure of the antenna.
To that end, according to invention, the microstrip antenna for transmitting or receiving waves of wave-length &lgr; is characterized in that it comprises:
a first insulating plate and a first metallization effected on one face of said plate covering a part of said first plate to form a ground plane,
a second insulating plate and at least a second metallization effected on one face of said second plate and presenting dimensions smaller than those of the first metallization, said second plate comprising a peripheral zone surrounding said second metallization over a width substantially equal to &lgr;/10, corresponding to a region where the amplitude of the electromagnetic field created by the periphery of said second metallization is maximum, said second plate being provided with recesses in at least a part of said peripheral zone, solid portions separating said recesses in order to ensure a mechanical connection between that portion of said second plate bearing the second metallization and the rest of said second plate;
at least one antenna feedline connected to said first and second metallizations, and
spacer means fast with the two plates in order to maintain the two plates in a predetermined relative position so that the two metallizations face each other and the second metallization is opposite the first.
It will be understood that, thanks to the fact that the ground plane and the radiator patch or patches are disposed on insulating supports presenting a good mechanical strength and, moreover, the conducting plates are directly opposite one another, a microstrip antenna is obtained which may comprise one or more radiator patches which use the air as dielectric and which presents a suitable mechanical structure since the mechanical connection is easy via the insulating plates which serve as supports.
In addition, as will be explained in greater detail hereinbelow, the presence of the recesses in the plate surrounding at least a part of the metallizations forming the radiator patch or patches makes it possible effectively to use the air as dielectric in the maximum electronic field zone produced by the periphery of the radiating metallization or metallizations. In this way, optimal functioning of the antenna is obtained.
According to a preferred form of embodiment of the invention, the second insulating plate of the antenna is provided with a plurality of second metallizations of substantially rectangular form and the metallizations are electrically connected by connection portions.
In this embodiment which, thanks to the presence of the different radiating metallizations, makes it possible to suitably adapt the gain of the antenna, recesses are also provided in the peripheral zone disposed on either side of the means for electrical connection between the different radiating metallizations.


REFERENCES:
patent: 4623893 (1986-11-01), Sabban
patent: 4633262 (1986-12-01), Traut
patent: 4697189 (1987-09-01), Ness
patent: 5444453 (1995-08-01), Lalezari
Lee, Chon, et al., “Impedance Matching of a Dual-Frequency Microstrip Antenna with an Air Gap”, IEEE Transactions on Antennas and Propagation, 41(1993) May, No. 5, New York.
Gauthier, Gildas P., et al., “Microstrip Antennas on Synthesized Low Dielectric-Constant Substrates”, IEEE Transactions on Antennas and Propagation, vol. 45, No. 5 Aug. 1997.
Vaughan, Mark J., et al., “Improvement of Microstrip Patch Antenna Radiation Patterns”, 8082 IEEE Transactions on Antennas and Propagation 42(1994) Jun., No. 6, New York US.

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