Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Reexamination Certificate
2003-02-25
2004-11-23
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
C342S376000
Reexamination Certificate
active
06822615
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to electronically scanned antennas and, more particularly, to an electronic scanned antenna with a microelectromechanical system (MEMS) radio frequency (RF) phase shifter.
BACKGROUND OF THE INVENTION
Advanced airborne and space based radar systems heretofore have used electronically scanned antennas (ESA) including thousands of radiating elements. For example, large fire control radars that engage multiple targets simultaneously may use ESAs to provide the required power aperture product.
Space based lens architecture is one approach to realizing ESA for airborne and space based radar systems. However, when the space based lens architecture is utilized at higher frequencies, for example, the X-band, and more active components such as phase shifters are packaged within a given area, weight, increased thermal density, and power consumption may deleteriously affect the cost and applicability of such systems.
Heretofore, phase shifter circuits for electronically scanned lens array antennas have included ferrites, PIN diodes and FET switch devices. These phase shifters are heavy, consume a considerable amount of DC power, and are expensive. Also, the implementation of PIN diodes and FET switches into RF phase shifter circuitry is complicated by the need of an additional DC biasing circuit along the RF path. The DC biasing circuit needed by PIN diodes and FET switches limits the phase shifter frequency performance and increases RF losses. Populating the ESA with presently available transmit/receive (TIR) modules is undesirable due to high costs, poor heat dissipation and inefficient power consumption. In sum, the weight, cost and performance of available phase shifter circuits fall short of what is needed for space based radar and communication ESA's, where thousands of these devices are used.
SUMMARY OF THE INVENTION
The present invention provides a microelectromechanical system (MEMS) steerable electronically scanned lens array (ESA) antenna. According to an aspect of the invention, the MEMS ESA antenna includes a wide band feedthrough lens and a continuous transverse stub (CTS) feed array. The wide band feedthrough lens includes first and second arrays of wide band radiating elements and an array of MEMS phase shifter modules disposed between the first and second arrays of radiating elements. The continuous transverse stub (CTS) feed array is disposed adjacent the first array of radiating elements for providing a planar wave front in the near field. The MEMS phase shifter modules steer a beam radiated from the CTS feed array in two dimensions.
According to another aspect of the invention, there is provided a method of frequency scanning radio frequency energy, comprising the steps of inputting radio frequency (RIF) energy into a continuous transverse stub (CTS) feed array, radiating the RF energy through a plurality of CTS radiating elements in the form of a plane wave in the near field, emitting the RF plane wave into an input aperture of a wide band feedthrough lens including a plurality of MEMS phase shifter modules, converting the RF wave plane into discreet RF signals, using the MEMS phase shifter modules to process the RF signals, radiating the RF signals through a radiating aperture of the wide band feedthrough lens, thereby recombining the RF signals and forming an antenna beam, and varying the frequency of the RF signal inputted into the CTS feed array thereby to change the angular position of the antenna beam in the E-plane of the wide band feedthrough lens and to effect frequency scanning by the antenna beam.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
REFERENCES:
patent: 6160519 (2000-12-01), Hemmi
patent: 6421021 (2002-07-01), Rupp et al.
patent: 6677899 (2004-01-01), Lee et al.
Allison Robert C.
Lee Jar J.
Pierce Brian M.
Quan Clifton
Alkov Leonard A.
Raytheon Company
Vick Karl A.
Wimer Michael C.
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