Communications: radio wave antennas – Antennas – With radio cabinet
Patent
1998-04-15
1999-07-27
Wong, Don
Communications: radio wave antennas
Antennas
With radio cabinet
343876, 343906, H01Q 124
Patent
active
059298146
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to antenna assemblies and particularly but not exclusively to antenna assemblies for use with radio communication devices.
BACKGROUND OF THE INVENTION
In portable communications devices, antennas of various types are used to facilitate the propagation of radio frequency (RF) signals. The choice of antenna used for a particular device is typically dependent upon the size of the device, the environment in which it is to be used, and the communications application.
For example, in certain circumstances it may be inconvenient to use (or fully extend) a whip antenna. In the absence of any other antenna the performance of the device would then be seriously impaired.
A problem with this arrangement is that as it is impractical and inefficient to mount more than one antenna on each device, a compromise is often required between these various considerations, resulting in a less than optimum arrangement.
U.S. Pat. No. 5,255,001 discloses and antenna which may be folded between two positions. However, when in the folded position the antenna is of the same basic type although the plane of polarisation changes from vertical to horizontal.
This invention seeks to provide an antenna assembly which mitigates the above mentioned disadvantages.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided an antenna assembly comprising: an antenna arm having an active portion and a switching portion and having first and second operative positions; a ground plane, an inductive loop element connected to the ground plane, and an r.f connector connected to the active portion in both the first and second operating positions of the antenna arm, wherein, in the first operating position, the arm is generally parallel to the ground plane and the switching portion is physically connected to the inductive loop element such that the antenna acts as a transmission line antenna, and in the second operating position, the arm is extended away from the ground plane and the switching portion is physically disconnected from the inductive loop element, such that the antenna acts as a whip antenna.
Thus, an antenna in accordance with the invention is transformed from one type of antenna to another type. Preferably, when acting as a transmission line antenna the antenna maintains a vertical component and a horizontal component to produce a circular polarisation. This is particularly advantageous where the antenna is incorporated into portable equipment since it enables communication to take place for a wider range of orientations of the equipment than would otherwise be possible if say a horizontal or vertical polarisation were maintained.
Preferably the antenna arm is rotatably coupled to the ground plane, such that the arm is arranged to rotate between the first and the second radiating positions.
In the second active position, preferably the arm is generally perpendicular to the ground plane.
Preferably the antenna assembly is incorporated in a communications device having a display screen, wherein the antenna arm is arranged such that in the second active position, the arm subtends an angle between 110.degree. and 160.degree. with respect to the plane of the display screen.
The arm preferably subtends an angle of substantially 135.degree. with respect to the plane of the display screen.
In this way a device is afforded two antenna configurations without the need for two antennae.
According to a second aspect of the present invention there is provided a communications device comprising: an antenna assembly; a body; and, a display screen having a principal plane mounted on the body, wherein the antenna is rotatably mounted on the body around an axis which is at an angle of between 20.degree. and 70.degree. from the principal plane of the display screen, for movement between a first position generally parallel to the principal plane of the display screen and a second position at which the antenna subtends an angle of between 110.degree. and 160.degree. with r
REFERENCES:
patent: 5218370 (1993-06-01), Blaese
patent: 5255001 (1993-10-01), Tamura et al.
patent: 5649306 (1997-07-01), Vannatta et al.
"Transmission-Line Missile Antennas," King, R., Harrison, Jr., C.W., and Denton, Jr., D.H. IRE Transactions of Antennas and Propagation, Jan. 1960.
"Three-Dimensional Performance of an LMS Adaptive Array with Inverted-F Elements," Chao, R.Y., Fujimoto, K., and Hirasawa, K., IEEE 40 (1991) Aug., No. 3, New York, NY.
Goren Oz
Grossman Ovadia
Margalit Eli
Doutre Barbara R.
Motorola Inc.
Nguyen Kimnhung
Wong Don
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