Compact patch antenna employing transmission lines with...

Details Compact patch antenna employing transmission lines with... Compact patch antenna employing transmission lines with...

2001-06-13

2002-12-24

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Microstrip

C343S770000, C343S909000, C333S202000

Reexamination Certificate

active

06498587

ABSTRACT:

BACKGROUND INFORMATION
1. Field of the Invention
The present invention relates to the field of wireless communications, and more particularly to patch antennas.
2. Description of Related Art
Wireless devices have become an integral life style among mobile professionals and consumers worldwide. Users of wireless devices demand a more compact, yet powerful cellular phones, mobile devices, and personal digital assistants (PDAs). One approach to reduce the overall size of a wireless device is to reduce the dimension of a patch antenna.
FIG. 1
illustrates a conventional patch antenna
10
having a first slot
11
and a second slot
13
interconnected with each other by a full transmission line
12
. The first slot
11
and the second slot
13
operate as the two primary radiators in the mechanism of the patch antenna
10
. The full transmission line
12
, typically implemented as a half wavelength, is placed between the first slot
11
and the second slot
13
, ensuring that the first slot
11
and the second slot
13
will be fed by a &lgr;
g
/2 decay in order to extract the maximum efficiency from the patch antenna structure
10
.
An equivalent circuit
20
representing the patch antenna
10
is shown in FIG.
2
. The equivalent circuit
20
is constructed with capacitors
21
and
22
, resistors
23
and
24
, and inductors
25
and
26
. The capacitors
21
and
22
denote the fringing capacitance, the resistors
23
and
24
denoting the radiative resistance, and the elements
25
and
26
denoting a decay representing a transmission line.
A typical delay of &lgr;
g
/2 is often necessary to attain maximum efficiency. A way to reduce the dimension of a patch is to make decay in less space by a fictive &lgr;
g
/2. One conventional approach to increase the amount of delay in a given space of a transmission line is by loading the transmission line either capacitively or inductively, as described, for example, in S. Reed, L. Desclos, C. Terret, S. Toutain, “Patch Antenna Size Reduction by Inductive Loading”, in Microwave Optical Technology Letters April 2001.
Accordingly, it is desirable to have structures and methods of an antenna that is compact in size while attaining maximum efficiency.
SUMMARY OF THE INVENTION
The invention discloses a full transmission line replaced by a set of transmission lines connected between two slots or radiative elements. Components can be inserted in the space between the transmission lines. In an alternative embodiment, the transmission fines are cranked or bended for a more compact dimension of transmission lines. The cranked or bended transmission lines can also be loaded by inductive elements. In another embodiment, a patch antenna is constructed with n sets of transmission lines between the two slots, where each set of transmission line produces a different electrical length in accordance with a particular frequency. In a further embodiment, a set of intermediate filters is added within the transmission lines for differentiating the frequencies. The function of a filter is to pass through a predetermined frequency but rejecting other frequencies, which potentially can destroy the radiation effect.
Advantageously, the present invention reduces the overall dimension of a patch antenna, thereby decreases the overall size of a wireless device. Other structures and methods are disclosed in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.


REFERENCES:
patent: 4475107 (1984-10-01), Makimoto et al.
patent: 4918457 (1990-04-01), Gibson
patent: 5006858 (1991-04-01), Shirosaka
patent: 5045862 (1991-09-01), Alden et al.
patent: 5923295 (1999-07-01), Nakano et al.
patent: 6037525 (2000-03-01), Bateman
The New World of Communications Design Software, Ansoft Corporation—Ansoft Designer Article—Microwave Journal http://www.ansoft.com
ews/articles/Microwave_Journal—art03_01.cfm 5 pages.

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