Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-02-18
2001-06-26
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S757000
Reexamination Certificate
active
06252558
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to microwave systems, and, more particularly, to a microwave transmit/receive device having a light-based pointing and tracking system.
In one type of microwave device, a microwave signal is generated and propagated from a microwave feed horn along a microwave path. The microwave signal is reflected from a set of microwave mirrors, to a microwave antenna. The microwave antenna may be pointed in a selected direction to propagate the microwave signal in that direction as a microwave output beam. Additionally, the direction of propagation of the microwave output beam may be fine-tuned by tilting one or more of the mirrors of the microwave mirror set to redirect the microwave path prior to its reaching the antenna.
This type of microwave device is often used when there is a requirement for a high microwave power output. An example is the Deep Space Network used to send and receive communications signals to spacecraft that are far away from earth. In such a system, the large, heavy microwave feed horn and transmitter need not be pointed, but instead remain stationary with its output microwave signal directed to the antenna using the microwave mirror set, where it is directed into space. Another example is a portable microwave system which may be aligned and aimed optically.
In this type of microwave system, misalignment of the microwave beam propagated from the antenna results from any misalignment of the microwave mirror set. That is, if one or more of the microwave mirrors are assembled in a misaligned state or becomes misaligned during service, due to temperature fluctuations, mechanical shocks, or other reasons, the microwave output beam does not point exactly in the desired direction. This is particularly a problem for mobile microwave systems that are repeatedly disassembled, moved, and reassembled in another location, both because the components are desirably less massive and stable than in a stationary microwave system, and because there may be insufficient time and capability to adjust and align the system properly each time it is assembled.
There is a need for an approach by which microwave systems using a microwave mirror set may be readily pointed, tracked, and adjusted. The present invention fulfills this need, and further provides related advantages.
SUMMARY OF THE INVENTION
The present invention provides a microwave transmit/receive device with an integrated light pointing and tracking system. The light pointing and tracking system permits pointing of the microwave device to be compensated for errors in mirror alignment, which may arise upon assembly or in service. The result is precise aiming of the microwave output beam.
In accordance with the invention, a microwave antenna and light tracking system comprises a microwave antenna at a first end of a microwave path and at a first end of a light path, a microwave transmit/receive device at a second end of the microwave path, a light transmit/receive device at a second end of the light path, and a beam-guide system disposed in the microwave path and in the light path. The beam-guide system comprises a mirror set comprising at least one guide microwave mirror operable to direct a microwave beam along a first portion of the microwave path. Each microwave mirror has associated therewith (preferably embedded therein) a light mirror positioned to direct a light beam along a first portion of the light path substantially coincident with the first portion of the microwave path. The beam-guide system further includes a dichroic beam splitter disposed in a second portion of the microwave path between the mirror set and the microwave transmit/receive device, so that a second portion of the microwave path is reflected from the microwave beam-splitter mirror. The dichroic beam splitter is also disposed in a second portion of the light path between the mirror set and the light transmit/receive device, so that the second portion of the light path is transmitted through the dichroic beam splitter.
In this approach, the light path is substantially coincident with the microwave path, along the first portion of the light path and microwave path. Any misalignments in the microwave mirror(s) that affect the microwave path also affect the light beam. By compensating for the misalignment in the light beam, the misalignment and pointing error of the microwave beam is also compensated.
In a preferred embodiment, the microwave transmit/receive device is a microwave source such as a microwave horn, and a microwave output beam is propagated out of the antenna. The light transmit/receive device is a light sensor. The light sensor “sees” the same target region toward which the microwave output beam is directed. The microwave output beam may thereby be pointed in the desired direction.
The approach of the invention may be used with a microwave transmitter and/or receiver, and with a light transmitter and/or receiver, in any combination. For example, the microwave transmitter/receiver may include a microwave receiver for receiving signals from a target region viewed by the light sensor, in addition to or instead of the microwave source. The light transmitter/receiver may include a light source such as a laser designator, as well as the light sensor which receives the laser signal back from the target region. The microwave path and the light path are reciprocal, permitting microwave and light signals to travel in either direction.
In one application, the mirror set comprises at least four microwave waveguide mirrors, including a first microwave mirror adjacent to the dichroic beam splitter along the first portion of the microwave path, a second microwave mirror adjacent to the first mirror along the first portion of the microwave path, a third microwave mirror adjacent to the second microwave mirror along the first portion of the microwave path, and a fourth microwave mirror between the third microwave mirror and the antenna along the first portion of the microwave path. The first microwave mirror and the fourth microwave mirror lie along an azimuthal rotation axis, and the second microwave mirror and the third microwave mirror lie off the azimuthal rotation axis. The fourth microwave mirror lies along an elevational rotation axis lying perpendicular to the azimuthal rotation axis. An azimuthal rotation drive rotates the first microwave mirror, the second microwave mirror, the third microwave mirror, and the fourth microwave mirror as a unit about the azimuthal rotation axis. An elevational rotation drive rotates the fourth microwave mirror about the elevational rotation axis, permitting elevational aiming of the microwave output beam.
In another application, a guide mirror drive is operably connected to the at least one guide microwave mirror to change the position of the at least one guide microwave mirror, as by tilting. A controller has as an input a signal from the light sensor and as an output a command signal to the guide mirror drive. Active control of the controlled mirror is used to maintain the microwave beam pointed at a selected target region.
The present invention provides an important advance in the aiming of microwave antenna systems. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.
REFERENCES:
patent: 4260993 (1981-04-01), Aubry et al.
patent: 5041840 (1991-08-01), Cipolla et al.
patent: 5130718 (1992-07-01), Wu et al.
patent: 5214438 (1993-05-01), Brusgard et al.
patent: 5327149 (1994-07-01), Kuffer
patent: 5451969 (1995-09-01), Toth et al.
Brown Kenneth W.
Gallivan James R.
Raytheon Company
Tran Chuc
Wong Don
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