Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-02-29
2002-01-01
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S839000
Reexamination Certificate
active
06335703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improvements to antennas, and more particularly to advantageous aspects of a patch antenna with a finite ground plane.
2. Description of the Prior Art
In a microstrip patch antenna, the radiator is typically provided by a metallic patch element that has been fabricated, using microstrip techniques, onto a dielectric substrate above a ground plane. Because of their low profile, low cost, and compact size, microstrip patch antennas are suitable for various microwave antenna and antenna array applications. Microstrip patch antennas are used, for example, as the radiating elements of designs based on a microwave integrated circuit (MIC) or monolithic microwave integrated circuit (MMIC) such as those used in aircraft and satellite communications, in missile and rocket antenna systems, as well as personal communication system (PCS) wireless applications. However, one problem associated with microstrip patch antennas is that they typically have a limited beamwidth, compared with, for example, antenna designs employing a dipole element. In addition, current microstrip patch antenna designs do not provide for a compact, cost-efficient mechanism for adjusting the antenna beamwidth.
The prior art can be better understood with reference to
FIG. 1
, which shows a cutaway perspective view of a microstrip patch antenna
10
according to the prior art. As shown in
FIG. 1
, the antenna
10
comprises a square patch element
12
, a ground plane
14
, and a microstrip feed line
16
, lying on parallel planes defined by the top and bottom surfaces of a pair of dielectric substrates
18
and
20
. The patch element
12
is fabricated onto the top surface of the upper substrate
18
, the ground plane
14
is fabricated between the bottom surface of the upper substrate
18
and the top surface of the lower substrate
20
, and the feed line
16
is fabricated onto the bottom surface of the lower substrate
20
. A fixed metal plate reflector
22
is provided at the bottom of the antenna
10
to reflect radiation towards the top of the antenna
10
. Coupling between the feed line
16
and the patch element
12
is provided by a small rectangular aperture
24
in the ground plane
14
that lies across the feed line
16
. Because of this coupling technique, the design shown in
FIG. 1
is known as an “aperture-coupled patch antenna.” Other designs are also used, employing different techniques to couple the feed line to the patch element.
In current aperture-coupled patch antenna designs, the ground plane
14
is significantly larger than the aperture
24
such that, from an electromagnetic perspective, the ground plane
14
functions as an infinite surface relative to the aperture
24
. This helps the isolation between the feed line
16
and the patch element
12
. In addition, the use of an infinite ground plane makes analysis of the antenna much easier because the equivalence theorem can be applied.
An antenna's radiation pattern is important in antenna applications. It includes several parameters to characterize the antenna performance, including gain, 3 dB (half-power) beamwidth, side-lobe level, front-to-back (F/B) ratio, polarization, cross-polarization level, and the line. The 3 dB beamwidth parameter is the main parameter to show the coverage of radiated energy. The beamwidth of a conventional patch antenna is approximately 60° to 70°.
Because of their high level of integration, patch antennas have been used successfully to form large arrays for highly directional applications. However, other applications require a beam width of greater than the currently available 60° to 70°. For example, a typical three-section cellular system needs to cover a 120° geographic area. In a time division multiple access (TDMA) system, the base station requires an antenna with a 3 dB beamwidth of 105° to 110°, and a code division multiple access (CDMA) system requires a 3 dB beamwidth of 90°. Because of the beamwidth limitations of conventional patch elements, a dipole element is typically used instead in these applications.
In addition, it is desirable for the beamwidth of an antenna to be adjustable in certain applications. A dipole element with an angular reflector can be employed to provide beamwidth control by mechanically adjusting the reflector angle. However, this approach requires sophisticated mechanical structures which may not be cost effective, and which may also result in an undesirably large package size to accommodate these structures.
SUMMARY OF THE INVENTION
One aspect of the invention provides a microstrip patch antenna with enhanced beamwidth characteristics. In a first embodiment, the antenna comprises a patch element and a ground plane separated from the patch element by a first dielectric layer. The antenna further includes a signal feed line separated from the ground plane by a second dielectric layer, the signal feed line being shielded from the patch element by the ground plane. The signal feed line is electromagnetically coupled to the patch element through an aperture in the ground plane lying across the signal feed line, the ground plane functioning as a finite surface relative to the aperture. According to a further aspect of the invention, the beamwidth of the antenna is adjusted by adjusting the position of a reflector behind the signal feed line. Thus, the present invention provides an efficient way to achieve adjustable wide-beamwidth that may be used, for example, in wireless systems in a three-sector configuration.
Additional features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings.
REFERENCES:
patent: 6031502 (2000-02-01), Ramanujam et al.
patent: 6052086 (2000-04-01), Kudoh
Chang Li-Chung
Housel James A.
Tsai Ming-Ju
Lucent Technologies - Inc.
Priest & Goldstein PLLC
Wimer Michael C.
LandOfFree
Patch antenna with finite ground plane does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Patch antenna with finite ground plane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Patch antenna with finite ground plane will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2852131