MULTI-FEED REFLECTOR ANTENNA

Abstract: An antenna (100) includes a reflector (101) having a first axis (102), a second axis (103), a focal zone (104) that is about parallel to the first axis (102), and a focal point (105) located within the focal zone (104). A transmit feed (108) is located at focal point, and at least one receive feed is located within the focal zone (104). The transmit feed (108) is part of a bidirectional feed that includes an integral receive feed. The bidirectional feed transmits and receives an RF signal carrying digital information signals to and from a first satellite, such as an FSS satellite, and each respective receive feed (109) receives a signal from satellite, such as a DBS satellite.

Description: MULTI-FEED REFLECTOR ANTENNA This application is related to Provisional Application No. 60/195,247, filed April 7, 2000 entitled Multi-Feed Reflector Antenna. BACKGROUND OF THE INVENTION The present invention relates to the field of satellite communications. More particularly, the present invention relates to a multi-feed antenna suitable for satellite communications. Geostationary direct broadcast systems (DBS) are geostationary satellite systems that are direct competitors to terrestrially-based cable television systems. Such DBS systems have the advantage of allowing a terrestrially-based receiver to receive a plurality of television channels from virtually any location on Earth, while a cable television subscriber must be connected to a cable television system to receive television signals. Terrestrial-based cable television systems have the advantage over DBS systems of allowing a subscriber to have a high-bandwidth Internet connection through the cable television system, while such a coimection is unavailable through a DBS system. Currently, digital links to the Internet are available through the fixed satellite system (FSS), another system of geostationary satellites. U.S. Patent No. 5,859,620 to Skinner et al. relates to a multiband feedhorn satellite receiving antenna that receives signals from more than 30 satellites that are longitudinally spaced in geosynchronous orbits above the equator of the Earth. According to Skinner et al., a satellite receiving antenna includes a torodial reflector having a circular cross-section in a horizontal (longitudinal or azimuthal) plane and a parabolic cross-section in an elevational plane. The size of the Skinner et al. reflector requires a plurality of braces for support and is far too large for use in a residential environment. U.S. 5,805,116 to Morley discloses to an ultra-small aperture antenna for a satellite communications terminal having a dish reflector and separate transmit and receive feedhorns. According to Morley, a receive feedhorn is spatially offset from a transmit feedhorn. Both feedhorns are disposed within a focal point zone such that the receive feedhorn is positioned at an ideal focal point of the dish reflector. The transmit feedhorn is positioned to have an aperture offset from the ideal focal point, but is still within the focal point zone of the dish reflector. The receive feedhorn is disposed at the ideal focal point for maximizing gain of received signals. A disadvantage with the Morley antenna is that the transmitter requires a relatively greater power output for compensating for the mispointing of the transmitted signal. Consequently, what is needed is a small single antenna that is suitable for residential use, can simultaneously communicate with a geostationary FSS satellite and with a plurality of geostationary DBS satellites, and minimizes the amount of transmitter output power for transmitting to the FSS satellite. SUMMARY OF THE INVENTION The present invention provides a small single antenna that is suitable for residential use, can simultaneously communicate with a geostationary FSS satellite and with a plurality of geostationary DBS satellites, and minimizes the amount of transmitter output power for transmitting to the FSS satellite. The advantages of the present invention are provided by an antenna that includes a reflector having a first axis, a second axis, a focal zone that is about parallel to the first axis, and a focal point located within the focal zone. According to the invention, a transmit feed is located at or about at the focal point, and at least one receive feed is located at about the focal zone. Preferably, the reflector is an elliptically-shaped offset-type parabolic reflector, and the transmit feed is part of a bidirectional feed that includes an integral receive feed. The bidirectional feed transmits and receives an RF signal carrying digital information signals to and from a first satellite, such as an FSS satellite, and each respective receive feed receives a signal from satellite, such as a DBS satellite. In a preferred embodiment, the present invention provides an antenna that includes an elliptically-shaped offset-type parabolic reflector having a first axis, a second axis, a focal direction, a focal zone that is about parallel to the first axis, and a focal point located within the focal zone. Accordingly, a transmit feed is located at within the focal zone, and at least one receive feed located at about the focal zone. A support arm extends from the bottom of the reflector in the focal direction of the reflector and supports the transmit feed at the focal point and each receive feed within the focal zone. BRIEF DESCRIPTION OF THE DRAWING The present invention is illustrated by way of example and not limitation in the accompanying figures in which like reference numerals indicate similar elements and in which: Figure 1A shows a front view of a first configuration of an antenna according to the present invention; Figure IB shows a front view of an alternative configuration of an antenna according to the present invention; Figure 2 shows a combination side/cross-sectional view of the first configuration of an antenna according to the present invention; Figure 3 shows a combination top/cross-sectional view of the first configuration of an antenna according to the present invention; Figure 4 shows a side perspective view of a preferred embodiment of an antenna according to the present invention; Figure 5 shows a front perspective view of a preferred embodiment of an antenna according to the present invention; Figure 6 shows a rear perspective view of a preferred embodiment of an antenna according to the present invention; and Figure 7 shows another front perspective view of a preferred embodiment of an antenna according to the present invention. DETAILED DESCRIPTION Figure 1 shows a front view of a first configuration of an antenna 100 according to the present invention. Figure 2 shows a combination side/cross-sectional view of antenna 100. Figure 3 shows a combination top/cross-sectional view of antenna 100. As shown by Figures 1-3, antenna 100 includes a reflector 101 having a horizontal major axis 102 and a vertical minor axis 103. Preferably, reflector 101 is elliptically-shaped parabolic antenna so that a plurality of geostationary satellites are within the field of view of antenna 100. Also, reflector 101 is preferably an offset- type parabolic reflector for minimizing the field of view of reflector 101 that is blocked by feed and feed-support structures. The physical dimensions of reflector 101 are preferably 36.2 inches along major axis 102, and 26 inches along minor axis 103. The projected dimensions of antenna 100 are preferably 36.2 inches along major axis 102 and 24.6 inches along minor axis 103. The physical dimensions are the actual dimensions of the reflector 101, while the projected dimensions are the functional dimensions of the antenna, that is, the dimensions that a satellite "sees". The projected dimensions are a function of the shape and topography of the antenna. Antenna 100 has a focal zone 104 (Figures 2 and 3) that parallel to horizontal major axis 102. When antenna 100 is oriented to communicate with the plurality of geostationary satellites, focal zone 104 is about parallel to the geostationary orbits (GSO) of the satellites, that is, focal zone 104 is about GSO parallel. Antenna 100 also has a focal point 105 that is defined by the shape of reflector 101. A support arm 106 extends from the bottom of reflector 101. A feed-support member 107 extends from the end of support arm 106 substantially parallel to major axis 102. A transmit/receive feed 108 is mounted on feed support member 107 and is positioned at or about at focal point 105. Preferably, transmit/receive feed 108 is an integral bidirectional feed that transmits and receives an RF signal carrying digital information signals, such as used by computers for communicating between computers in a well-known manner. At least one additional receive feed 109 is positioned within focal zone 104. While the Figures 1-3 show two receive feeds 109a and 109b, any number of additional receive feeds can be positioned within focal zone 104. Preferably, each receive feed 109 receives direct broadcast (DBS) television signals. Figure IB shows a front view of an alternative configuration of an antenna 100a according to the present invention. For this configuration, transmit/receive feed 108 can be used as a transmit/receive (Tx/Rx) feed and a receive-only (Rx) feed at the same time. Transmit/receive feed 108a is positioned at or about at focal point 105 together with receive feed 108b. Together transmit/receive feed 108a and receive feed 108b operate as a bidirectional feed that transmits and receives an RF signal carrying digital information signals, such as used by computers for communicating between computers in a well-known manner. In operation, antenna 100 is oriented so that signals transmitted to and received from an FSS satellite are respectively transmitted and received from focal point 105, while signals received from each DBS satellite are respectively received at points within focal zone 104. More specifically, antenna 100 is oriented so that an FSS geostationary satellite 110, such as a Gstar 4 satellite, is focussed at focal point 105. Transmit/receive feed 108 is positioned on feed-support member 107 at or about at focal point 105 so that a signal transmitted to FSS geostationary satellite 110 is about optimized with respect to the pointing direction to the FSS satellite. Signals that are to be transmitted to FSS satellite 110 are generated by a computer system 111, such as a personal computer (PC), and converted in a well-known manner to an RF signal having an appropriate frequency for, transmission to FSS satellite 110. Signals received from FSS satellite 110 are detected in a well-known manner and supplied to computer system 111. Each additional receive feed 109 is positioned within focal zone 104 at a point that is about optimum for receiving a signal from a corresponding geostationary DBS (direct broadcast service) satellite 112 based on the pointing direction of antenna 100. Exemplary DBS satellites include the Echostar I and II system satellites and the EchoStar IV system satellites. Signals received by additional receive feeds 109 are directed to a television 113 through, for example, a dish network multi-satellite switch 114 and a dish network integrated receiver/descrambler (IRD) 115. Figures 4-7 show different views of a preferred embodiment of an antenna 400 according to the present invention. Antenna 400 includes an elliptically-shaped parabolic reflector 401. A support arm 406 extends from the bottom of reflector 401. A feed support member 407 extends from the end of support arm 406 substantially parallel to the major axis of reflector 401. A transmit/receive feed 408 is mounted on feed support member 407 and is positioned at or about at the focal point of reflector 401, as described above in connection with Figures 1-3. Transmit/receive feed 408 is an integral bidirectional feed that transmits and receives an RF signal carrying digital information signals. An additional receive feed 409 is positioned within the focal zone of reflector 401, as also described above. Both feeds 408 and 409 are mounted on support member 407 using an adjustment bracket 410 for optimizing each feed along a vertical direction. In operation, antenna 400 is oriented so that signals transmitted to and received from an FSS satellite are respectively transmitted and received by transmit/receive feed 408, while signals received from a DBS satellite are respectively received by receive feeds 409a and 409b. While the present invention has been described in connection with the illustrated embodiments, it will be appreciated and understood that modifications may be made without departing from the true spirit and scope of the invention.

Claims: THE CLAIMS What is claimed is: 1. An antenna, comprising: a reflector having a first axis, a second axis, a focal zone that is about parallel to the first axis, and a focal point located within the focal zone; a transmit feed located about at the focal point; and at least one receive feed located within the focal zone. 2. The antenna according to claim 1, wherein the reflector is an elliptically-shaped parabolic reflector. 3. The antenna according to claim 1, wherein the reflector is an offset- type parabolic reflector. 4. The antenna according to claim 1, wherein the reflector has a dimension of less than about 36.2 inches along the first axis and a dimension of less than about 26 inches along the second axis. 5. The antenna according to claim 1 , wherein the transmit feed is part of a bidirectional feed. 6. The antenna according to claim 5, wherein the bidirectional feed includes a receive feed that is integral with the transmit feed.. 7. The antenna according to claim 6, wherein the bidirectional feed includes a separate transmit feed and a separate receive feed, the separate receive feed being located immediately adjacent to the separate transmit feed within the focal zone. 8. The antenna according to claim 1 , wherein the bidirectional feed transmits and receives an RF signal carrying digital information signals to and from a first satellite, and wherein each respective receive feed receives a DBS signal from satellite that is different from the first satellite. 9. The antenna according to claim 8, wherein the first satellite is an FSS satellite. 10. The antenna according to claim 9, wherein the first satellite and each DBS satellite are geostationary satellites. 11. An antenna, comprising: an elliptically-shaped parabolic reflector having a first axis, a second axis, a focal direction, a focal zone that is about parallel to the first axis, and a focal point located within the focal zone; a transmit feed located about at the focal point; at least one receive feed located within the focal zone; and a support arm extending in the focal direction of the reflector and supporting the transmit feed at the focal point and each receive feed within the focal zone. 12. The antenna according to claim 11 , wherein the reflector has a top and a bottom, and wherein the support arm extends in the focal direction of the reflector from the bottom of the reflector. 13. The antenna according to claim 12, wherein the reflector is an offset- type parabolic reflector. 14. The antenna according to claim 11, wherein the reflector has a dimension of less than about 36.2 inches along the first axis and a dimension of less than about 26 inches along the second axis. 15. The antenna according to claim 11 , wherein the transmit feed is part of a bidirectional feed. 16. The antenna according to claim 15, wherein the bidirectional feed includes a receive feed that is integral with the transmit feed. 17. The antenna according to claim 16, wherein the bidirectional feed includes a separate transmit feed and a separate receive feed, the separate receive feed being located immediately adjacent to the separate transmit feed within the focal zone. 18. The antenna according to claim 15, wherein the bidirectional feed transmits and receives an RF signal carrying digital information signals to and from a first satellite, and wherein each respective receive feed receives a DBS signal from satellite that is different from the first satellite. 19. The antenna according to claim 18, wherein the first satellite is an FSS satellite. 20. The antenna according to claim 19, wherein the first satellite and each DBS satellite are geostationary satellites.

Inventors: SPIRTUS DANNY, SPIRTUS, DANNY
Applicants: GILAT SATELLITE NETWORKS, SPACENET INC, SPIRTUS DANNY, SPACENET, INC., SPIRTUS, DANNY
Application year: 2001
Main classification: H01Q19
IPC codes: H01Q1, H01Q3, H01Q5, H01Q19, H01Q25