Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2001-03-06
2001-11-27
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06323810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to antennas for use with radio transceivers. More particularly, the invention provides a small multiband patch antenna with very high efficiency and high isolation for use in cellular telephones and other personal electronic devices.
2. Background
Cellular telephones and other wireless electronic devices are widely used. Such devices have steadily grown smaller with advances in miniaturization of electronic components. This has created a challenge for the design of antennas in such devices. At the same time, it is desirable for the antenna to have a broad working bandwidth.
Various methods are known in the art to broaden the operating bandwidth of an antenna. Most of these employ parasitic elements that are excited by a driven element. In most cases, the elements are capacitively coupled. In the case of patch elements, the methods often rely on optimization of the coupling between the patches. The modes excited inside the different elements are basically the same.
Different methods exist in order to reduce the dimensions of a patch antenna. One such method is described in
Size Reduction of Patch Antenna by Means of Inductive Slits
, Reed, S., Desclos, L., Terret, C., Toutain, S., APS/URSI 20000 Utah. This method places a set of slits in the patch that represents an inductive loading. The authors report that a reduction of 50% in the dimensions of the patch antenna was achieved with this approach. Generally speaking, however, as the patch gets smaller, the efficiency decreases and the working bandwidth gets smaller.
SUMMARY OF THE INVENTION
The present invention comprises a small, printed antenna with high efficiency, good isolation and a broad working bandwidth. These characteristics are achieved with a patch antenna by placing a shunt to ground connected to the feeding point of the patch. This shunt comprises a line running along one edge of the patch. The patch dimensions can be adjusted, and in particular reduced, by changing the L and C characteristics of the patch. This is accomplished with arrays of slots defining corresponding arrays of fingers along the edges of the patch. Impedance matching is achieved by altering the dimensions of the slots.
By adding a strip line shunt at the feed point of the antenna, an efficient driving element for exciting the antenna is defined. This strip line at the frequency of use constitutes an inductance. While it helps with broadband matching, it also creates a capacitive coupling with the first neighbor finger. From this strong coupling, it is possible to excite different modes. In fact, the shunt helps to unbalance the antenna, which should not be considered as a patch under a classical mode. The antenna can be considered as a set of fingers that will combine in either an array form or single couple of fingers.
The bandwidth of the antenna is increased by adding as many couples of fingers as frequencies needed to form the total bandwidth by the addition of the subside bands.
REFERENCES:
patent: 4749996 (1988-06-01), Tresselt
patent: 5410323 (1995-04-01), Kuroda
patent: 6181281 (2001-01-01), Desclos et al.
patent: 6211825 (2001-04-01), Deng
Desclos Laurent
Poilasne Gregory
Blakely , Sokoloff, Taylor & Zafman LLP
Ethertronics Inc.
Ho Tan
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