Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-01-03
2001-12-04
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S846000
Reexamination Certificate
active
06326919
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to patch type antennas, and particularly but not exclusively to antennas suitable for use in portable radiotelephones.
Portable radiotelephones are presently becoming very widespread in numerous countries. One of the objects sought by the designers of such radiotelephones is to make them as small as possible so as to make them even more easy to use. One of the elements that gives rise to difficulties with such miniaturization is the antenna of the radiotelephone. In the vast majority of conventional radiotelephones, the antenna is external and therefore increases the overall size of the device.
Another problem associated with designing radio-telephones lies in the fact that two frequency bands are used at present for portable radiotelephone networks. Firstly there is the so-called “GSM” band which corresponds to frequencies in the range 890 MHz to 960 MHz, and secondly there is the so-called “DCS 1800” frequency band which extends from 1700 MHz to 1880 MHz.
It will therefore be advantageous to have radio-telephones capable of operating in either of those two frequency bands depending on the network being used.
It is relatively easy to provide electronic circuits in a radiotelephone that are capable of processing transmission and reception of signals corresponding to two different frequency bands, and typically those that are mentioned above. In contrast, designing an antenna that is suitable for two frequency bands constitutes a problem that is more difficult.
Patch type antennas have already been proposed for use in radiotelephones. Such an antenna can be placed inside the radiotelephone itself, thereby considerably reducing its overall size. Nevertheless, in that known solution, the patch antenna is suitable for operating in one frequency band only.
There thus exists a real need for an antenna of the patch type which is suitable in particular for portable telephones and which is capable of operating in two distinct frequency bands, and in particular in the above-mentioned frequency bands.
SUMMARY OF THE INVENTION
An object of the present invention is thus to provide an antenna element or a complete antenna of the patch type which is capable of operating in two distinct frequency bands and which is suitable for fitting to a portable device.
According to the invention, this object is achieved by a patch-type internal antenna element for a portable device, which antenna element is characterized in that it comprises:
a body of dielectric material having a bottom face, a top face, and four side faces;
a conductive plate covering said top face;
a conductive strip covering one of the side faces, electrically connected along its top edge to one of the edges of said plate, and provided with electrical connection means extending along a second edge parallel to its top edge and designed to connect said conductive plate to a ground plane that is designed to be placed against the bottom face of said dielectric body, the other three side faces having no metallization;
means passing through said dielectric body between its bottom face and its top face, for electrically connecting the hot point of an antenna conductor to said plate; and
capacitor-forming means for providing capacitance between said plate and said ground plane when said antenna element is mounted on the ground plane, said means being located close to the side face of the dielectric body that is remote from its face covered by said conductive strip, whereby the side face remote from the face provided with said strip forms a radiating slot corresponding to a first frequency band while the other two opposite side faces that are not covered in metallization form radiating slots for a second frequency band.
It will be understood that because of the presence firstly of the radiating slot corresponding to a short circuit and secondly of the other two radiating slot faces, it is possible to use the antenna in two distinct frequency bands as required, corresponding respectively to half-wavelength and to quarter wavelength.
It will also be understood that because of the presence of the capacitance, good tuning is obtained between the antenna conductor or probe and the antenna itself in both of the frequency bands in which the antenna can operate.
The invention also provides an internal patch type antenna for a portable device, which antenna is characterized in that it comprises an antenna element of the above-defined type, a conductive plate constituting the ground plane, and a power supply whose hot point is connected to said plate and whose power supply ground is connected to the conductive plate forming the ground plane of the antenna.
It will thus be understood that it is easy using the antenna element to provide a complete antenna by adding a ground plane.
In a variant embodiment of the antenna, the conductive antenna plate and the conductive strip covering one of the side faces to the dielectric belonging to the antenna element, and also the conductive plate constituting the ground plane, are all constituted by a single folded metal sheet that is fixed to the body of dielectric material.
In a preferred embodiment of this variant, the portion of said metal sheet that forms the ground plane has a first opening surrounded by an electrical connection collar that projects from said sheet and that constitutes an extension of said sheet, and the hot point is constituted by a conductor element passing through the body of dielectric material and having a first end electrically connected to said antenna plate and having a second end projecting from the face of the dielectric material inside said collar.
It will be understood that in this embodiment, the collar and the second end of the conductor element form antenna connection elements that are directly suitable for co-operating with a base provided on the printed circuit of the portable device fitted with the antenna.
In numerous cases, the portable device which is fitted with its internal patch antenna must also be capable of operating with an external antenna, e.g. the antenna of a motor vehicle. Under such circumstances, it is necessary for the internal antenna to be disconnected from the antenna circuit of the portable device and for the external antenna to be connected instead to the antenna circuit of the device.
To solve this problem, in an embodiment that can be combined with the preceding embodiment, the antenna is characterized in that the portion of said metal sheet that forms said antenna plate has a second opening in register with the first opening, in that the first end of said conductor element projects from the top face of said body of dielectric material, in that said body of dielectric material has a recess surrounding said conductor element, and in that said sheet includes an elastically deformable second extension surrounding said second opening with the free end thereof projecting into said recess and being pressed resiliently against said conductor element.
It will be understood that the elastically deformable second extension constitutes an electric switch member. At rest, corresponding to the device operating with the internal antenna, the conductor element is electrically connected to the conductive plate forming the radiating patch of the patch antenna via the switch element. Otherwise, when the external antenna connector is connected, said connector moves away the switch element forming second extension of the conductor element, thereby disconnecting the internal antenna.
The invention also relates to the use of an internal antenna of the patch type for a portable device and of the above-defined type in making a portable radio-telephone, the use being characterized in that the conductive plate forming the ground plane is constituted by the ground plane for the circuits of the radio-telephone.
In addition, said conductive plate is preferably interposed between the printed circuit of the radio-telephone and the antenna element so that said conductive plate forms a reflector plane fo
Diximus Frédéric
Leclerc Daniel
Vincent Roland
Amphenol Socapex
Blank Rome Comisky & McCauley LLP
Chen Shih-Chao
Wong Don
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