Patent Application
20060049987
This invention relates to reflect antennas and more particularly to reflect array antennas.
As is known in the art, reflect array antennas have been used in many applications. One type of reflect array antenna is a microstrip reflect array. The microstrip reflect antenna is essentially a planar array of microstrip patch antennas or dipoles illuminated by a feed. The individual antenna elements scatter the incident field appropriately so that the reflected field has a planar equi-phase front. The concept of a planar reflect array is not new, however, implementations found in the literature use a single antenna element for both transmit and receive. Pozar, et al., in a paper entitled “Design of a Millimeter Wave Microstrip Reflectarrays” published in IEEE Transactions on Antennas and Propagation, Vol. 45, No. 2, February 1997, for example, presented a microstrip reflect array of unique patch antennas, each sized for appropriate phasing, in which the same antenna element receives and transmits. With the exception that each antenna element is unique, the single substrate structure is comprised of rectangular patches on one side and a ground plane on the other. Bialkowski et al. have implemented a microstrip reflect array at X-band using aperture coupled patch antennas as reported in an article entitled “Design, Development, and Testing of X-Band Amplifying Reflectarrays” and published in IEEE Transactions on Antennas and Propogation, Vol. 50, August 2002. Isolation between transmit and receive have proven difficult with this approach since only one antenna is used with orthogonal slots for both transmit and receive. Further, U.S. Pat. No. 6,384,787 describes a flat reflectarray antenna.
In accordance with the present invention, a reflect antenna element is provided having a receive antenna section and a transmit antenna section. Each section has an air cavity, a ground plane conductor with a slot, and a conductive element in registration with the slot and cavity. A strip conductor and ground plane conductor form a microstrip transmission line for coupling energy received by the receive antenna section to the transmit antenna section. The transmit antenna section and receive antenna section are configured to operate with orthogonal polarizations.
In one embodiment, an amplifier is disposed in circuit with the transmission line.
In accordance with another feature of the invention, an antenna element is provided having a receive antenna section and a transmit antenna section. The receive antenna section includes: (i) a receive patch conductor disposed on a first portion of a first surface of first one of a pair of overlying substrates; (ii) a receive cavity disposed in a first portion of the first one of the substrates, such receive cavity being in registration with the receive patch conductor, a first inner portion of the first one of the pair of substrates being disposed between the receive cavity and the receive patch conductor, such receive cavity having an elongated portion and (iii) a ground plane conductor having a receive slot therein, such receive slot having an entrance for receiving energy the receive cavity. The transmit antenna section includes: (i) a transmit patch conductor disposed on second portion of the first surface of the first one of the pair of substrates, such second portion of the first surface of the first one of the pair of substrates and the second portion of the first one of the substrates being laterally spaced one from the other along the first surface of the first one of the pair of substrates; (ii) a transmit cavity disposed in a second portion of the first one of the substrates, such transmit cavity being in registration with the transmit patch conductor, a second inner portion of the first one of the pair of substrates being disposed between the transmit cavity and the transmit patch conductor, such transmit cavity having an elongated portion and (iii) wherein the ground plane conductor has a transmit slot therein, such transmit slot having an entrance for transmitting energy into the transmit cavity. A strip conductor is provided having portions thereof disposed over the receive slot and the transmit slot and disposed on a surface of a second one of the pair of substrates, such strip conductor, underlying portions of the second one of the pair of substrates, and underlying portions of the ground plane conductor forming a microstrip transmission line for coupling energy received by the receive antenna section to the transmit antenna section. Elongated portion of the receive cavity is disposed along a first direction and the elongated portion of the transmit cavity is disposed along a second direction, the first direction being perpendicular to the second direction.
With such an arrangement, separate transmit and receive aperture coupled patch antenna sections are used for improved isolation and an orthogonal polarization twist. In addition, micromachining or photolithograhic-etching processes of a semiconductor substrate underneath the patch antenna sections adds bandwidth and reduces surface waves. This two-substrate, i.e., two-layer, architecture allows for active array implementation by replacing the lower feed layer with a power amplifiers (PA) which is completely shielded from the incident radiation to the antenna sections by a ground plane conductor.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Referring now to
The receive antenna section 12 includes: a receive patch conductor 18 disposed on a first portion of a first surface 20 of a first one of a pair of overlying substrates 22, 24, here on surface 20 of substrate 22. Here the substrate 22 is high resistively silicon to provide a dielectric substrate. A receive cavity 26 is disposed in substrate 22 and has an elongated portion 27. The receive cavity 26 is in registration with, here aligned directly behind, the receive patch conductor 18. An inner portion 28 of the first substrate 22 is disposed between the receive cavity 16 and the receive patch conductor 18. The receive antenna section 12 includes a ground plane conductor 30 having an elongated receive slot 32 therein. The receive slot 32 has an entrance for receiving energy in the receive cavity 32.
The transmit antenna section 14 includes a transmit patch conductor 34 disposed on second portion of the first surface 20 of the substrate 22. The receive patch conductor 18 and the transmit patch conductor are laterally spaced one from the other along the first surface 20 substrate 22. The transmit antenna section 14 includes a transmit cavity 36 disposed in a second portion of substrate 22 and has an elongated portion 23. The transmit cavity 36 is in registration with, here aligned directly behind, the transmit patch conductor 34. An inner portion 38 of the substrate 22 is disposed between the transmit cavity 36 and the transmit patch conductor 34. The ground plane conductor 30 has a transmit slot 40 therein. The transmit slot 40 has an entrance for transmitting energy into the transmit cavity 36.
A strip conductor 42 has portions thereof disposed over the receive slot 22 and the transmit slot 36 and disposed on a surface 44 of a second one of the pair of substrates 22, 24, here on substrate 24. Here substrate 24 is of the same material as substrate 22. The strip conductor 62, underlying portions 46 of the substrate 24, and underlying portions of the ground plane conductor 30 form the microstrip transmission line 16 for coupling energy received by the receive antenna section 12 to the transmit antenna section 14.
The elongated portion 27 of the receive cavity 26 is disposed along a first direction, shown as a vertical direction ion
Referring now to
Referring now to
The use of a two-substrate structure 10, 10′ described above allows space for transmit/receive (T/R) elements while keeping them sufficiently isolated. Micromachining or partially etching the silicon from behind the patch conductive elements maintains the isolation, and prevents surface waves The antennas 10, 10′ have the following features:
By replacing the microstrip feed line with a power amplifier 50 as in
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
