Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2001-03-28
2004-07-27
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000
Reexamination Certificate
active
06768460
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a diversity wireless device used for wireless communications, and more particularly to a diversity wireless device suitable for use in a wireless terminal unit for a wireless local area network (LAN), such as a wireless PC card.
BACKGROUND OF THE INVENTION
The antenna diversity used for wireless communications and the like is an effective means of eliminating influence of fading from received signals.
Generally, “fading” is a phenomenon in which variation of medium on a radio wave propagation path or the movement of mobile communication equipment through areas with different field intensities changes the strength of received signals rapidly. In addition, “diversity” means ensuring highly-reliable communications by preparing a plurality of antennas and synthesizing or switching two or more signals received at a reception side in a suitable manner when fading deteriorates the receiving condition.
General methods of providing diversity used for wireless communications and the like are as follows. That is, signals are separately received by two or more receiving systems that have a low degree of correlation therebetween and the received signals are synthesized or automatically switched before or after demodulation and then used. Typical examples of such methods include space diversity and polarization diversity.
The space diversity utilizes the fact that the variations caused by the fading at points separated from each other in the vicinity of a receiving point are independent of each other. Generally, two or more antennas are arranged so as to be spatially separated from each other and receive signals separately. Then, the signals are used after being synthesized or switched. The polarization diversity is a method of separately receiving signals using polarized wave receiving antennas that are arranged 90° different from each other. Either method can provide the greater diversity gain when the antennas have the lower degree of correlation therebetween.
FIG. 15
shows a structure of a conventional diversity wireless device (for example, disclosed in Japanese Patent Application Non-Examined Publication No. H07-131229).
In
FIG. 15
, substrate
3910
has antennas
3930
and
3940
mounted thereon. Formed on substrate
3910
is ground plane
3920
. Antenna
3930
has feed terminal
3931
and ground terminal
3932
that also serves to support the antenna. Similarly, antenna
3940
has feed terminal
3941
and ground terminal
3942
that also serves to support the antenna. In addition, mounted on substrate
3910
is radio frequency (RF) circuit
3950
. RF circuit
3950
performs such operations as switching transmission/reception antennas, feeding power into the antennas, and processing received signals. The ground of RF circuit
3950
connects to ground plane
3920
. In this structure, antennas
3930
and
3940
are so-called inverted F-type antennas, in which ground plane
3920
also affects the antenna characteristics.
In recent years, there has been a strong request for downsizing of wireless devices. The downsizing have necessitated the smaller space assigned to antennas. Therefore, only insufficient space can be provided between antennas. This makes a higher degree of correlation between the antennas connected to a common ground, thus resulting in reduction in the diversity gains.
In addition, in recent years, with the progress of networking in offices and at home, a plurality of personal computers (hereinafter referred to as PC) is connected via Internet or other networks and LANs are built. On the other hand, networking using wireless devices has been drawing attention because it does not have the problems of troublesome rewiring at a layout change and difficulty in new wiring. Especially, because the Institute of Electrical and Electronics Engineers (IEEE) standardized a transmission speed of 11 Mbps equivalent to that attained with wire devices, the introduction of wireless LANs has been promoted at a cheaper price than ever. An adapter for a wireless LAN is available as a wireless PC card, in which the space its wireless part can occupy is limited. Therefore, the wireless part including its antenna part is structured to have its own features.
Known conventional wireless PC cards include the invention disclosed in Japanese Patent Publication No. 3004533 and the utility model disclosed in Japanese Utility Model Publication No. 3041690, both of which are built with inverted F-type antennas.
FIG. 14A
is a perspective view illustrating an appearance of a wireless PC card as a conventional portable wireless terminal unit.
FIG. 14B
is a perspective view illustrating the antenna arrangement part of the PC card.
FIG. 14C
is a cross-sectional view of the card including its enclosure taken on line
14
C—
14
C of FIG.
14
B.
As shown in
FIGS. 14A and 14C
, the wireless PC card has extended part
3620
covered with frame
3590
, top sheet metal cover
3600
, and bottom sheet metal cover
3610
. This extended part
3620
includes a plurality of antenna elements therein. In other words, as shown in
FIG. 14B
, extended part
3620
has conductor section
3510
serving as a first antenna element, conductor section
3520
serving as a second antenna element and ground plane
3580
on circuit board
3570
. Conductor section
3510
has feed terminal
3530
and ground terminal
3540
bending at and protruding from the edges of the conductor section. With its terminal
3540
grounded to ground plane
3580
on substrate
3570
, the conductor section serves as an inverted F-type antenna. Similarly, conductor section
3520
has feed terminal
3550
and ground terminal
3560
bending at and protruding from the edges of the conductor section. With its terminal
3560
grounded to ground plane
3580
, the conductor section serves as an inverted F-type antenna.
Two antenna elements are used for the following reasons: antenna element
3510
and antenna element
3520
provide diversity; and one with better characteristics is selected from these antenna elements by switching them using a switch (not shown) when the variations in intensity of received waves are caused by such influences as fading.
In general, the size of the extended part of a wireless PC card used as a wireless LAN card is determined by the standard of PC cards—54 mm in width, 40 mm in length and 10.5 mm in height. Characterized in that they have high performance and can be downsized, the inverted F-type antennas are often used for a wireless PC card.
Now, the characteristics of the inverted F-type antennas are the better at the greater distance between substrate
3570
and conductor sections
3510
and
3520
(the distance shown at “h” in FIG.
14
C). Therefore, it is important to make the distance “h” longer. However, when the distance “h” is determined to the limit of its standard, extended part
3620
is too large as shown in
FIG. 14A
, thus imposing some limitations on the design of its shape.
SUMMARY OF THE INVENTION
The present invention addresses the above-mentioned problem and aims to provide a diversity wireless device and a wireless terminal unit that can be downsized without reduction in their diversity gains.
A diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of antennas. The device has antennas that are grounded (grounded antennas) and antennas that are not grounded (ungrounded antennas).
Another diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of ungrounded antennas. The device is structured so that a ground is provided in the vicinity of at least one of the ungrounded antennas and the ungrounded antenna is coupled to the ground via high-frequency waves.
Still another diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of antennas. The device is structured so that it h
Hoashi Masakazu
Koga Naoki
Le Hoang-anh
RatnerPrestia
LandOfFree
Diversity wireless device and wireless terminal unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diversity wireless device and wireless terminal unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diversity wireless device and wireless terminal unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3232334