Communications: radio wave antennas – Antennas – Within conductive apertured wall
Reexamination Certificate
1999-11-09
2001-11-13
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Within conductive apertured wall
C343S786000, C343S895000
Reexamination Certificate
active
06317097
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to antenna systems. More specifically, the present invention relates to a cavity-driven antenna system having a passive antenna element.
The purpose of an antenna system is to radiate efficiently the power supplied to it in the form of an electromagnetic wave. Some of the simplest known antenna systems include a single antenna element which is driven with a current to transmit an electromagnetic wave at the wavelength of the applied current. Known antenna elements include, for example, a dipole, a quarter-wave monopole, a helix, a spiral and a loop.
Antenna systems may also be required to concentrate the radiated power (i.e., the propagated electromagnetic wave) in a given direction and to minimize the radiated power in other directions. To achieve such directionality often requires a complicated antenna system that incorporates a number of individual antenna elements (e.g., an array configuration) and/or the addition of a reflector or cavity. For example, an antenna system comprising a helix antenna element within a relatively long, extended cavity has better directionality than a helix antenna alone because the cavity can suppress the side-lobes (i.e., off-axis radiated power normally present in an antenna pattern) normally present with a helix antenna alone.
FIG. 1
illustrates a cross-section view of a known antenna system having a helix antenna element within an extended cavity. The antenna system
10
has an antenna element
11
disposed within a cavity
12
. The antenna element
11
is driven by a current from a power source
13
. The cavity has an extended length to provide additional directivity; the length of the cavity is extended in the sense that it is typically longer than several wavelengths of the antenna system. The extended length of the cavity suppresses the propagation of side-lobes in the antenna pattern.
Although known antenna systems can provide some level of directionality, such systems suffer several shortcomings. For example, the use of an extended cavity adds to the weight, size and cost associated with the antenna system. Antenna systems that use multiple antenna elements, for example, in an array configuration again add to the cost and complexity associated with the antenna system.
SUMMARY OF THE INVENTION
The antenna system of the present invention overcomes the shortcomings of the known antenna systems by providing improved directivity. An electromagnetic wave can be transmitted from and received by an antenna system having a cavity member, a passive antenna element and at least one driver element. The cavity member has a back portion and a wall portion which define a substantially cylindrical interior portion. The passive antenna element has a first end disposed within the interior portion of the cavity member. The driver element is coupled to the interior portion of the cavity member rather than being directly connected to the passive antenna element.
In one embodiment, a driver element is driven with a current by a power source to produce an electromagnetic field, where the driver element is coupled to an interior portion of a cavity member. The electromagnetic field can be coupled into an antenna element having a first end disposed within the interior portion of the cavity to transmit an electromagnetic wave.
REFERENCES:
patent: 2495399 (1950-01-01), Wheeler
patent: 3417403 (1968-12-01), Fenwick
patent: 3680138 (1972-07-01), Wheeler
patent: 4442438 (1984-04-01), Siwiak et al.
patent: 4494117 (1985-01-01), Coleman
patent: 5041842 (1991-08-01), Blaese
patent: 5233364 (1993-08-01), Lefeuvre et al.
patent: 5694140 (1997-12-01), Waterman et al.
patent: 5708448 (1998-01-01), Wallace
Kenyon & Kenyon
Smith Technology Development LLC
Wimer Michael C.
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