Planar double L-shaped antenna of dual frequency

Details Planar double L-shaped antenna of dual frequency Planar double L-shaped antenna of dual frequency

2003-04-01

2004-10-05

Nguyen, Hoang V. (Department: 2821)

Communications: radio wave antennas

Antennas

Microstrip

C343S702000, C343S846000

Reexamination Certificate

active

06801168

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to antennas and more particularly to an improved planar double L-shaped antenna capable of operating at two different frequency ranges.
BACKGROUND OF THE INVENTION
A conventional sleeve (or L-shaped) antenna mounted in a wireless communication device is illustrated in FIG.
1
. As shown, the antenna comprises a coaxial transmission line
10
including an inner conductor (or core)
14
, an outer conductor (or shielded mesh or ground line)
16
, and a cylinder
17
of insulated dielectric material sandwiched between the inner and outer conductors
14
and
16
so that a concentric conductor as known in the electromagnetism is formed by both the inner and outer conductors
14
and
16
. Moreover, an insulated shell
19
is formed around the coaxial transmission line
10
. The coaxial transmission line
10
has one end coupled to a control circuit (not shown) of the wireless communication device so that the coaxial transmission line
10
can be served as a feed line. A ground metal plate
18
is formed on the other end of the coaxial transmission line
10
. The ground metal plate
18
is coupled to the outer conductor
16
so as to electrically ground the outer conductor
16
of the coaxial transmission line
10
. An extension
12
is formed from the inner conductor
14
at the other end of the coaxial transmission line
10
. The extension
12
is shaped like an inverted L shape and extends beyond the ground metal plate
18
. A length of the inverted L-shaped extension (i.e., radiating element)
12
is closely related to a resonant frequency of the antenna which is typically operated at a single frequency.
For making the L-shaped antenna more compact, a technique of manufacturing the antenna on a printed circuit board is adopted by some manufacturers in the art as shown in FIG.
2
. The L-shaped antenna comprises a dielectric substrate
27
, a patch line
24
printed on the top of the dielectric substrate
27
, the patch line
24
having one end formed as a signal feed point
241
, a ground metal plate
28
printed on the bottom of the dielectric substrate
27
opposite to the patch line
24
, and an inverted L-shaped radiating element
242
formed at the other end of the patch line
24
, the inverted L-shaped radiating element
242
being extended in a direction perpendicular to the patch line
24
above and beyond the ground metal plate
28
. A length of the inverted L-shaped radiating element
242
is closely related to a resonant frequency of the antenna which is typically operated at a single frequency.
Further, for the purpose of using a coplanar wave guide as a feed line, another technique of manufacturing the L-shaped antenna on a printed circuit board is adopted by some manufacturers in the art as shown in FIG.
3
. The coplanar wave guide based L-shaped antenna comprises a dielectric substrate
37
, a coplanar wave guide line
34
printed on the top of the dielectric substrate
37
, the coplanar wave guide line
34
having one end formed as a signal feed point
341
, two spaced ground metal plates
38
printed on the top of the dielectric substrate
37
(i.e., the same surface as the coplanar wave guide line
34
) with the coplanar wave guide line
34
located therebetween and spaced apart, and an inverted L-shaped radiating element
342
formed at the other end of the coplanar wave guide line
34
, the inverted L-shaped radiating element
342
being extended in a direction perpendicular to the coplanar wave guide line
34
and beyond the ground metal plates
38
. A length of the inverted L-shaped radiating element
342
is closely related to a resonant frequency of the antenna which is typically operated at a single frequency.
There has been a significant growth in wireless local Area network (WLAN) due to an increasing demand of mobile communication products in recent years in which IEEE 802.11 WLAN protocol is the most important one among a variety of WLAN standards. The IEEE 802.11 WLAN protocol was established in 1997. The IEEE 802.11 WLAN protocol not only provides many novel functions for WLAN based communication but also proposes a solution for communicating between mobile communication products made by different manufacturers. There is no doubt that the use of the IEEE 802.11 WLAN protocol is a milestone in the development of WLAN. The IEEE 802.11 WLAN protocol was further modified for being adapted to serve as a standard of both IEEE/ANSI and ISO/IEC in August 2000. The modifications comprise IEEE 802.11a WLAN protocol and IEEE 802.11b WLAN protocol. In an expanded standard physical layer, the operating frequencies have to be set at 5 GHz and 2.4 GHz. As such, the well-known L-shaped antenna cannot satisfy the requirement of enabling a mobile communication product to use both IEEE 802.11a and IEEE 802.11b WLAN protocols at the same time. Instead, several antennas have to be mounted in the product for complying with the requirement of frequency band. However, such can increase a manufacturing cost, complicate an installation procedure, and consume precious space for mounting the antennas. As a result, the size of the product cannot be reduced, thereby contradicting the compactness trend.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a planar double L-shaped antenna of dual frequency for fulfilling the need of multi-frequency operation which is unobtainable by a conventional antenna only operated at a single frequency.
One object of the present invention is to provide a planar double L-shaped antenna operable at two different frequency ranges comprising a dielectric substrate; a patch line printed on a top of the dielectric substrate, the patch line having one end formed as a signal feed point; a ground metal plate printed on a bottom of the dielectric substrate; and first and second radiating elements wherein the first radiating element is formed at the other end of the patch line and extended in a direction perpendicular to the patch line above and beyond the ground metal plate to shape as an inverted L shape, and the second radiating element is adjacent the first radiating element, extended beyond the ground metal plate to shape as an inverted L shape, and spaced apart from the first radiating element and extended in a direction either opposite to or the same as that of the first radiating element so that the first and the second radiating elements are capable of receiving signals having different frequencies.
Another object of the present invention is to provide a planar double L-shaped antenna operable at two different frequency ranges comprising a dielectric substrate; a coplanar wave guide line printed on a top of the dielectric substrate, the coplanar wave guide line having one end formed as a signal feed point; two spaced ground metal plates printed on the top of the dielectric substrate with the coplanar wave guide line located therebetween and spaced apart; and first and second radiating elements wherein the first radiating element is formed at the other end of the coplanar wave guide line and extended in a direction perpendicular to the coplanar wave guide line and beyond the ground metal plates to shape as an inverted L, and the second radiating element is extended from one of the ground metal plates to shape as an inverted L, spaced apart from the first radiating element and extended in a direction either opposite to or the same as that of the first radiating element so that the first and the second radiating elements are capable of receiving signals having different frequencies.
In one aspect of the present invention a length of each of the first and the second radiating elements is about one-quarter wavelength at each operating frequency of the frequency ranges so that the first and the second radiating elements are capable of receiving signals of dual frequency as stipulated by IEEE 802.11a protocol and IEEE 802.11b protocol respectively.
The above and other objects, features and advantages of the present invention will become apparent from the following deta

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