Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
1999-12-23
2001-10-23
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S746000, C343S876000
Reexamination Certificate
active
06307519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to antennas, and, in particular, to a multiband antenna array using radio frequency (RF) micro-electro-mechanical (MEM) switches.
2. Description of Related Art
Communications satellites are in widespread use. The communications satellites are used to deliver television and communications signals around the earth for public, private, and military uses.
The primary design constraints for communications satellites are antenna beam coverage and radiated Radio Frequency (RF) power. These two design constraints are typically thought of to be paramount in the satellite design because they determine which customers on the earth will be able to receive satellite communications service. Further, the satellite weight becomes a factor, because launch vehicles are limited as to how much weight can be placed into orbit.
Many satellites operate over fixed coverage regions and employ polarization techniques, e.g., horizontal and vertical polarized signals, to increase the number of signals that the satellite can transmit and receive. These polarization techniques use overlapping reflectors where the reflector surfaces are independently shaped to produce substantially congruent coverage regions for the polarized signals. This approach is limited because the coverage regions are fixed and cannot be changed on-orbit, and the cross-polarization isolation for wider coverage regions is limited to the point that many satellite signal transmission requirements cannot increase their coverage regions.
Many satellite systems would be more efficient if they contained antennas with high directivity of the antenna beam and had the ability to have the coverage region be electronically configured on-orbit to different desired beam patterns and/or frequency bands. These objectives are typically met using a phased array antenna system. However, phased array antennas carry with them the problems of being restricted to a single frequency band, as well as being limited by large efficiency losses.
If multiple frequency bands are to be used by the satellite for communications, the typical approach is to use two antennas with two reflectors, one antenna and one reflector for the first frequency band and a separate antenna and reflector for the second frequency band. This approach adds significant weight and size to the satellite, which limits the launch vehicle choices, and, typically, limits the size of the reflector that can be used for the frequency bands of interest. As such, smaller service areas result from the reduced size of the antenna system.
There is therefore a need in the art for a phased array antenna system that can use multiple frequency bands. There is also a need in the art for a phased array antenna system that has low efficiency losses. There is also a need in the art for an antenna system that can use multiple frequency bands and still cover a large service area.
SUMMARY OF THE INVENTION
The present invention discloses a method and system for transmitting multiple frequency bands from a single slot antenna. The system comprises a slot antenna and a micro-electro-mechanical (MEM) switch, coupled to the slot antenna. The MEM switch is opened and closed, thereby changing the resonant frequency of the slot antenna. The slot antenna transmits a first frequency when the MEM switch is open and a second frequency when the MEM switch is closed.
The method for transmitting a first frequency and a second frequency from a slot antenna comprises the steps of transmitting the first frequency from the slot antenna, closing a micro-electro-mechanical (MEM) switch coupled across the slot antenna, therein changing the resonant frequency of the slot antenna, and transmitting the second frequency from the slot antenna after the MEM switch is closed.
A signal comprising a first and second frequency in accordance with the present invention is transmitted by an array of antennas, wherein the array of antennas comprises at least one slot, the slot being reconfigurable through a RF MEM switch coupled to the slots by performing the steps of transmitting the first frequency from the slot antenna, closing a micro-electro-mechanical (MEM) switch coupled across the slot antenna, therein changing the resonant frequency of the slot antenna, and transmitting the second frequency from the slot antenna after the MEM switch is closed.
A system in accordance with the present invention provides a phased array antenna system that can use multiple frequency bands. A system in accordance with the present invention also provides a phased array antenna system that has low efficiency losses. Further, a system in accordance with the present invention provides an antenna system that can use multiple frequency bands and still cover a large service area.
REFERENCES:
patent: 3813674 (1974-05-01), Sidford
patent: 3852994 (1974-12-01), Pereda
patent: 4410890 (1983-10-01), Davis et al.
patent: 5541614 (1996-07-01), Lam et al.
patent: 5754143 (1998-05-01), Warnagirls
patent: 6069587 (2000-05-01), Lynch et al.
Lam Juan F.
Lee Jar J.
Livingston Stan W.
Loo Robert Y.
Chen Shih-Chao
Duraiswamy Vijayalakshmi D.
Hughes Electronics Corporation
Sales Michael W.
Wong Don
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