Communications: radio wave antennas – Antennas – Plural separate diverse type
Reexamination Certificate
1997-02-24
2001-08-28
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Plural separate diverse type
C343S840000, C343S909000
Reexamination Certificate
active
06281852
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to radio wave communications, antennae, and more specifically to a reflector antenna for satellite signal reception as well as local radio and television reception.
2. Description of Related Art
Typical direct broadcast satellite (DBS) reception systems currently employ parabolic dish antennas that are both bulky and not aesthetically pleasing. Furthermore, these systems are not able to receive radio and TV signals of local origin. In order to improve the aesthetic character of satellite antenna systems, low profile or “flat-dishes” have been developed; however, previous low profile DBS antennas have been deficient in important RF performance parameters such as, for example, gain, low sidelobes, high cross-polarization solation, and also in necessary mechanical features such as structural integrity and light weight. These devices, due to their complexity, have not been able to be produced at the low cost required for broad commercial success.
As an example of the foregoing, attempts continue in the development of a low profile, high gain flat antenna to achieve acceptable satellite TV signals. Various flat antenna designs using printed circuit, Fresnel zone reflectors and phased array antenna technologies have been tried. Printed circuit flat antennas are limited in bandwidth, aperture efficiency, cross polarization isolation and have high manufacturing costs. Flat phased array antenna designs exhibit very low aperture efficiency, typically in the range of approximately 30-37% versus a high of 70% for an off-set parabolic dish antenna. This type of antenna design also exhibits very poor cross-polarization isolation and high production costs. Fresnel zone plate antennas, which are essentially flat, have not been able to adequately meet all the previously mentioned antenna parameters. The most important limitations of these antennas are primarily related to the above-mentioned loss of performance and poor gain.
A flat antenna is disclosed in
C
100
: Tsiger Planar Antenna
a technical description from Tsiger Planar Inc. of Colorado Springs, Colo. This device is 65 inches square by only 2.5 inches in thickness, and weighs 65 pounds. It is a combination Fresnel lens and zone plate of a design not yet disclosed nor having patents issued. Further, of interest in the matter of flat antennae is an article entitled,
The New Age of Earth Station Technology
published in
Via Satellite
, May 1994. No prior art has been found which discloses a combination of multi-stepped reflectors, axis fed, lens corrected splash plate feed with VHF/UHF antenna combined elements for the simultaneous reception of satellite and local station off-air broadcast signal reception of high quality.
The present invention fulfills these needs and provides further related advantages as described in the following summary.
SUMMARY OF THE INVENTION
The invention is a combination satellite and local broadcast receiving antenna. It comprises a satellite wave reflector, a feed assembly, a satellite low noise amplifier, and a local broadcast VHF-UHF antenna and a low noise amplifier.
A principal object of the invention is to provide a low profile, flat and compact antennae especially or an improved conventional parabolic dish satellite antenna suited to DBS reception with improved cross polarization isolation, low sidelobes, high gain efficiency, low cost, high reliability and low susceptibility to RF interference.
A further object of the invention is to provide such a satellite antenna with the additional capability of receiving VHF-UHF broadcasts of terrestrial origin.
These and other objectives are achieved by providing a multi-stepped reflector antenna which provides optimal results in individually focusing the incoming satellite parallel rays to a common focal point, while assuring that all reflections are in phase. The reflector consists of multiple parabolic reflective surfaces, all of which are arranged for radiating in phase using one wavelength stepped transitions. These transitions are the phase corrections required to focus each surface to a common focal point. The phased matched steps between the reflecting surfaces are the basis for improved efficiency in the design. The use of step-chokes or quarter wave chokes incorporated in the shadow areas between successive surfaces, control edge scattering in each successive reflecting surface. They reduce electromagnetic energy scattering at the step discontinuities, thereby improving the overall reflection efficiency. The one half wavelength steps provide immunity to terrestrial interference. Various types of corrections are feasible with this antenna. These include satellite and transponder distortion characteristics, satellite propagation characteristics, frequency compression digital coding characteristics and time delay distortion.
A Cutler feed is used in the invention as a mode converter. It changes the direction of the wave returning it to the reflector so as to control the pattern of the feed. A dielectric insert reduces the size of the aperture of the waveguide by dielectric loading. The reduced waveguide and splash plate size, reduces the size of the dead zone at the center of the main reflector. A dielectric lens provides additional efficiency of collection of the reflector. The waveguide can carry either vertically or horizontally polarized energy, or it can carry both polarizations simultaneously to obtain any sense or orientation of received polarization. The feed has excellent cross-polarization isolation and is optimized for the aperture area which preferably uses a 4-10 decibel selectable edge taper and provides equal E-plane and H-plane illumination. The feed and wave guide assembly interfaces directly with a satellite low noise amplifier (LNA) positioned behind the reflector. It provides for polarization selection and optimization, and also alignment through selection of components and by simply rotating the feed assembly within the stationary reflector. The local VHF-UHF LNA provides active summing of the individual off-the-air antenna elements and increases the systems gain-to-temperature ratio to improve off-the-air reception of local broadcast stations.
The performance of the rectangular relatively flat satellite antenna combined with an antenna for local VHF-UHF broadcast reception was of such a success in increased performance over conventional satellite dishes that further improvements were achieved subsequent to the initial successful development. By placing the legs to the VHF-UHF antenna on the outfacing surface of the satellite reflector better omni directional reception was achieved along with the capability to vary the lengths and number of legs to both increase bandwidth reception and customize for local reception in different geographical locations where different frequencies in radio and television signals might be desired. Further, by carrying the VHF-UHF antenna legs upon, or formed into, the satellite transmission reflective surface located upon a satellite wave reflector body formed of a non conductive radio wave transparent material such as fiberglass, plastic, ceramic, or other such materials which are relatively transparent to the passing of VHF-UHF broadcast signals, greater omni directional characteristics are achieved in the VHF-UHF antenna legs. Concurrently, greater capability to vary the length and number of antenna legs is achieved by the ability to use the microwave reflective surface to also form one or a plurality of VHF-UHF antenna legs for local omni directional reception of television and radio signals. Additionally, these improvements can also be used to manufacture conventional round parabolic dish style satellite antennas which will concurrently receive local VHF-UHF signals with all of the same benefits of variable length and number of antenna legs for reception of the desired radio and television spectrum. Heretofore conventional DBS parabolic satellite dish antennas have been made of metal, metal impregnated fiberglas
Harms Donn K.
Phan Tho
Wong Don
LandOfFree
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