Antenna

Details Antenna Antenna

2000-11-27

2002-09-10

Wong, Don (Department: 2821)

Communications: radio wave antennas

Antennas

Microstrip

C343S702000

Reexamination Certificate

active

06448931

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an antenna formed by integrating a plurality of radiating elements on a board and for transmitting/receiving a plurality of frequencies.
BACKGROUND OF THE INVENTION
Recently, mobile-satellite communications such as between mobile bodies including airplanes, vessels, or cars and satellites have been prevailing. Highly-efficient antennas mounted to the mobile bodies are developed by studying a shape of radiator elements of the antennas to be small in size. This study produces a meander-line antenna or a plate-type inverse F antenna. For instance, Japanese Patent Application Non-examined Publication No. H06-90108 discloses one of the products.
FIG. 15
illustrates a conventional antenna, and
FIG. 16
illustrates that the antenna is mounted to a mobile body.
FIG. 17
shows a relation between return losses and frequencies. In
FIG. 15
, antenna
200
comprises the following elements:
(a) Insulation board
200
;
(b) Radiator element
201
and formed by meander-line of length L and width W disposed on insulation board
200
;
(c) Feed line
202
; and
(d) Feeding point
203
disposed near the center of element
201
.
The frequency characteristic of antenna
200
, as shown in
FIG. 17
, has a single resonance frequency f
0
, and frequency f
0
is determined mainly by element's length L. The frequency relative bandwidth of antenna
200
is about several percent.
FIG. 18
shows another conventional antenna, which includes two independent antenna sections
210
and
220
having different resonance frequencies. Antenna section
210
comprises radiator element
211
, short-circuiting plate
212
, feeding section
213
, and grounding plate
214
. Radiator
211
shapes in a long and narrow rectangular plate, and short-circuiting plate
212
couples electrically radiator element
211
with grounding plate
214
. Feeding section
213
is disposed at a side end of element
211
as shown in FIG.
18
. Antenna section
210
has a resonance frequency f
1
determined by the sum (L
1
+H
1
) of length L
1
of element
211
and the height H
1
of short-circuiting plate
212
. Antenna section
220
is structured in the same way and has resonance frequency f
2
determined by the sum (L
2
+H
2
) of length L
2
of element
221
and the height H
2
of short-circuiting plate
222
. The frequency relative bandwidth of this antenna is also several percent, and if the radiator element is shortened for downsizing the antenna, the relative bandwidth further narrows.
In general, as discussed above, the conventional antenna has a narrow frequency relative bandwidth. Therefore, when a transmitting band and a receiving band are greater than the relative bandwidth, an antenna including two sections, one for transmitting and the other for receiving, is required. For example, in the mobile satellite communication system (ORBCOMM system) assigned by World Administrative Radio Conference 1992, where several dozens of low-earth-orbital satellites perform data communication between the ground and the satellites, frequencies for uplink/downlink (137.0-138.0 MHz/148.0-150.05 MHz) are used. Also, a conventional antenna cannot cover these two frequency-bands, therefore, an antenna including two sections, one for transmitting and the other for receiving is required.
When antennas independently dedicated to transmitting and receiving are used, these antennas should be separately mounted to a mobile body, such as a car or a container. Accordingly, two feeding points and two feed lines are required, and wiring job should be doubled, which makes a mounting job very complicated. The conventional antenna is ca. 0.5 m tall, when this is mounted to a container, it is hard to put the antenna into a clearance between the containers. Further, when the antenna is mounted vertically to a car, the antenna is vulnerable to damaged caused by wind pressure or interference with other members. When the antenna is mounted horizontally to a car, the metal sheet of the car influences the antenna so that an antenna impedance changes, its resonance frequency shifts, or impedance matching between the antenna and its feeding line is disordered, thereby the antenna does not work properly.
SUMMARY OF THE INVENTION
An antenna being capable of transmitting and receiving a plurality of frequencies is provided. This antenna is small, thin, and easy-to-mount. The antenna is also characterized by high production-efficiency.
This antenna comprises a ground plate and a plurality of radiator elements shaping with a rectangular shape, where a first end of the antenna is short-circuited to the grounding plate, the elements which are disposed separately from the ground plate. The longitudinal lengths of the elements are set within the range of &lgr;/8-3&lgr;/8 so that a working frequency of respective elements meet given frequencies. One single antenna thus can transmit and receive frequencies within a desired frequency bandwidth. Further, couplers between a plurality of elements are provided so that only one radiator element can be fed power, and the other elements are fed indirectly. This structure allows a number of feeding points and feed lines to be reduced.


REFERENCES:
patent: 5627550 (1997-05-01), Sanad
patent: 5966097 (1999-10-01), Fukasawa et al.
patent: 5977916 (1999-11-01), Vannatta et al.
patent: 6114996 (2000-09-01), Nghiem
patent: 06-334420 (1994-12-01), None
patent: 08-78943 (1996-03-01), None
patent: 10-93332 (2000-04-01), None

Affiliated with

Also associated with

Rating

Antenna does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Antenna, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2897981