Modified inverted-F antenna

Details Modified inverted-F antenna Modified inverted-F antenna

1999-11-05

2001-04-24

Le, Hoanganh (Department: 2821)

Communications: radio wave antennas

Antennas

With grounding structure

C343S7000MS, C343S795000

Reexamination Certificate

active

06222496

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to radio frequency antennas and, more particularly, to inverted-F antennas.
BACKGROUND OF THE INVENTION
Inverted-F antennas are commonly used in mobile transmitter/receivers, such as cellular telephones and wireless modems for portable computers.
FIG. 1
illustrates a conventional inverted-F antenna
100
. As shown in
FIG. 1
, the inverted-F antenna
100
has a vertical ground
110
and a straight horizontal element
120
. Conventional inverted-F antennas, such as the inverted-F antenna
100
of
FIG. 1
can be fabricated on a printed circuit board (PCB), or using a wire or plate construction, in a well-known manner. For a detailed discussion of conventional inverted-F antennas, see, for example, Kazuhiro Hirasawa and *
5
AsMisao Haneishi, “Analysis, Design, and Measurement of Small and Low-Profile Antennas,” Artech House, Norwood, Mass (1992); or Kyohei Fujimoto et al., “Small Antennas,” Research Studies Press, United Kingdom (1987), each incorporated by reference herein.
Inverted-F antennas are generally characterized by the distance, S, between the grounding element
110
and feeding element
130
; the overall length, L, of the antenna
100
; and the height, H, of the antenna
100
. Impedance matching for an inverted-F antenna is obtained by adjusting the distance, S, between the grounding and feeding elements. As the size of the devices in which inverted-F antennas are utilized has decreased, the space available for such inverted-F antennas has likewise decreased. For many applications, the distance, S, between the grounding element
110
and feeding element
130
has become so small that the tuner must be extremely sensitive. In particular, the impedance matching is very difficult or too sensitive due to the small distance, S, between the grounding
110
and the feeding elements
130
. In addition, the rectangular shape of conventional inverted-F antennas
100
does not provide sufficient mechanical strength for many applications.
A need therefore exists for an improved inverted-F antenna that exhibits improved impedance matching and mechanical strength. A further need exists for an improved inverted-F antenna that has a reduced overall dimension and an additional degree of freedom for tuning the impedance of the antenna.
SUMMARY OF THE INVENTION
Generally, a modified inverted-F antenna is disclosed that improves on conventional designs by incorporating a sloped grounding element at a fixed end of the horizontal element and a downward bend at a loose end of the horizontal element. According to one aspect of the invention, the sloped grounding element is connected in a triangular configuration with the feeding element and a ground plane of the antenna, to provide additional benefits. First, the triangular shape of the present invention decreases the distance, D, between the grounding plane and the feeding element relative to a conventional rectangular connection. Thus, the present invention exhibits improved impedance matching characteristics. The distance, D, between the grounding plane and the feeding element can be expressed as follows:
D={square root over (H
2
+L +S
2
+L )}.
where H is the height of the antenna and S is the horizontal spacing between the feeding element and where the sloped grounding element connects to the grounding plane.
In addition, the triangular shape provides increased mechanical strength relative to a conventional rectangular connection. According to another feature of the invention, the downward bend at the loose end of the antenna can be adjusted to thereby further adjust the impedance matching of the antenna.
The sloped grounding element and downward bend features of the modified inverted-F antenna also serve to reduce the overall dimension of the antenna. The total length, L
T
, of the disclosed antenna device can be expressed as follows:
L
T
={square root over (H
2
+L +S
2
+L )}+L
1
{square root over (B
h
2
+L +B
V
2
+L )}.
where H is the height of the antenna, S is the horizontal spacing between the feeding element and point where the sloped grounding element connects to the grounding plane, L
1
is the length of a horizontal portion of said horizontal element, B
v
is the vertical distance of said downward bend and B
h
is the horizontal distance of said downward bend.
A more complete understanding of the present invention, as well as further features and advantages of the present invention, will be obtained by reference to the following detailed description and drawings.


REFERENCES:
patent: 5764190 (1998-06-01), Murch et al.
patent: 5912647 (1999-06-01), Tsuru et al.
patent: 5926150 (1999-07-01), McLean et al.
patent: 6034636 (2000-03-01), Saitoh
patent: 6046699 (2000-04-01), Elliott et al.
Hirasawa et al., “Analysis, Design, and Measurement of Small and Low-Profile Antennas,” Artech House, Inc., 1992, Chapter 5, pp. 161-180.

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