Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-01-07
2001-07-31
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S7810CA, C343S840000, C343S915000, C343SDIG002
Reexamination Certificate
active
06268835
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to satellite antenna systems. In particular, the present invention relates to a deployable phased array of reflector antennas that provides scanning capability using reflector antennas as elements.
Spaceborne communication applications often rely on deployable reflector antennas to achieve high gain. The deployable reflector antenna uses one or more feeds located at or near the reflector focal point, for example, to receive energy focused by the reflector at the focal point. An alternative type of antenna, the direct radiating phased array antenna, is built using a large number of direct radiating elements spaced closely together on a lattice, and is often impractical for space applications.
In many communication applications, an antenna with a large effective aperture size is desired. The aperture size refers to the physical size of the antenna, and, as the aperture size increases, the sensitivity or “gain” of the antenna increases, with a concomitant reduction in beamwidth. A large aperture size thus produces a narrow beam that allows an antenna to receive or transmit energy from or to a very precise point. For example, a large aperture antenna is more effective at collecting, focusing, finding and pinpointing the energy emitted by a distant star.
In addition to having a large aperture, many antennas preferably have agile scan capability, which is the ability to rapidly (i.e., electronically, instead of mechanically) scan a transmit or receive beam over a wide angular range. In a phased array antenna, a set of amplitude and phase control electronics drive each radiating element. The control electronics are typically quite flexible and allow a phased array antenna to achieve an enormous angular range. For example, a phased array antenna may have an angular range of ±30 to ±45 degrees. Unfortunately, as the aperture size of a phased array antenna increases, the amount of radiating elements and associated control electronics drastically increases, with a concomitant increase in power consumption, thermal dissipation and weight. The complexity of the structural design and the deployment also increase drastically. In other words, large aperture phased array antennas are impractical from economic and engineering standpoints.
A deployable mesh reflector antenna, on the other hand, readily achieves very large aperture sizes with very low weight and stow volume. As a reflector antenna increases in size, however, its angular steering range becomes more limited due to optical aberrations which degrade antenna sensitivity (or “gain”). Although longer focal lengths or multiple feeds may be used in a reflector to increase the angular scanning range, the fact remains that the angular scan range of a reflector decreases as the reflector size increases. Furthermore, as the aperture size increases and the beam width narrows (which in most instances is a desirable condition that creates a high power beam), an increasingly smaller feed handles an increasing amount of power. However, the amount of power that practical feeds and electronics can handle is limited by breakdown, multi-paction or heating.
Therefore, in the past, practical reflector antennas have been limited to approximately 10 to 20 beamwidths of scan, and signal power levels are constrained. A phased array antenna, on the other hand, has the ability to scan several hundred beamwidths. Further, the phased array distributes energy over numerous antenna elements and has the capability for handling much higher levels of power. As noted above, however, it is usually impractical to construct a large aperture phased array antenna.
Spaceborne antennas, of course, reach orbit in a launch vehicle. Launch vehicles are extremely expensive, and any reduction in size and weight generally results in a reduced cost to launch. Thus, although large aperture antennas are desirable, the aperture size has, in the past, been limited by the launch cost, size of the launch vehicle, and the extent to which the antenna can be folded or packed together into the launch vehicle. Thus, there is a further need for a cost effective, light weight, compact large aperture antenna that is economical to launch.
A need has long existed in the industry for a new antenna that overcomes the problems noted above and previously experienced.
BRIEF SUMMARY OF THE INVENTION
Another aspect of the present antenna is that it shares characteristics of both phased array antennas and reflector antennas.
A feature of the present antenna is that it shares a phased array of reflectors antenna that provides scanning capability using reflector antennas as elements.
Another feature of the present antenna is a phased array of reflectors antenna with a controllable reflector element pattern that is selected via switching, based on grating lobes or signal attenuation from the array fed reflectors.
Yet another aspect of the present antenna is a deployable phased reflector array antenna with signal phase and amplitude steering electronics.
Another feature of the present antenna is a structure that shares interface boundaries with adjacent reflector antennas, and that uses a shaping surface to help form a reflector surface.
The present phased array of reflectors antenna includes reflector antennas formed using individual reflectors and feed arrays. Each feed array is disposed above a corresponding individual reflector, for example at the reflector focal point. The individual reflector antennas are preferably disposed adjacent to one another (e.g., on a hexagonal lattice) to form a phased array antenna from the individual reflector antennas.
The individual reflectors and feeds that make up the feed arrays, for example, may be arranged approximately on a regular reflector lattice, with pseudo random offset to compensate for grating lobes as discussed below. Phase and amplitude control devices (electronic, photonic or digital) are coupled to each reflector antenna to provide steering for the signal energy coupled between (i.e., received from or transmitted through) the reflectors and the feed arrays. Switching electronics are coupled to the feed arrays and selectively activate and deactivate beam forming clusters of feeds in the feed arrays. The switching electronics, as explained in more detail below, thereby help avoid the effects of grating lobes in the total antenna pattern formed by the phased reflector array antenna.
The present phased array of reflectors generates an antenna pattern that is the product of an array pattern and an array fed reflector element pattern. The array pattern is generated assuming ideal point sources at each reflector location in the reflector array lattice, while the array fed reflector element patterns are generated by selectively illuminating each reflector with the array feed located above the reflector.
One embodiment of the present method for generating a steerable antenna pattern couples signal energy through a beamforming section or network to form steered signal energy. Next, the method couples the steered signal energy between an array of reflector antennas. As noted above, the reflector antennas are preferably disposed adjacent to one another to form a phased array antenna in which the individual reflector antennas are considered radiating (or receiving) elements.
The method selectively activates feed clusters within each array located above each reflector. As an example, identical feed clusters would be selected in each of the 91 array fed reflectors shown in FIG.
1
. The signal from each of these clusters would then be routed to a common beamformer to be appropriately delayed and combined.
Signal energy propagates to the array of reflector antennas and to the first and second feed clusters to transmit signal energy. Conversely, the method couples signal energy from the array of reflector antennas and from the first and second feed clusters to receive signal energy. The method also selectively deactivates the first feed cluster and activates a third feed cluster, and selectively dea
Barlevy Alon S.
Chan Ronald Y.
Gilger L. Dwight
Hamada Shinobu J.
Toland Brent T.
Keller Robert W.
Nguyen Hoang
TRW Inc.
Wong Don
LandOfFree
Deployable phased array of reflectors and method of operation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Deployable phased array of reflectors and method of operation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Deployable phased array of reflectors and method of operation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2529560