1. Field
One or more aspects of embodiments according to the present invention relate to electronically scanned array antennas, and more particularly to an antenna capable of operating with multiple beams, and at multiple frequencies.
2. Description of Related Art
Electronically scanned array (ESA) antennas have multiple applications, including radar applications. In such applications, it may be desirable to transmit or receive more than one beam at a time, at more than one frequency, or with more than one polarization state. For example, it may be desirable for a system to be capable of operating both in the X band (8 GHz to 12 GHz) and in the Ku band (12 GHz to 18 GHz). While this can be accomplished using multiple separate antennas, the size, weight, and power (SWaP) of an assembly with multiple array antennas may be difficult to accommodate, e.g., on an aircraft.
One approach to achieving dual bands, or wideband ESAs, is to design the element spacing for the highest frequency band and let the lower frequency band also use the same element spacing. The problem with this approach is that the element spacing is not optimized for the lower frequency band SWaP. Another approach is to modulate each desired signal independently to achieve multiple independently modulated beams. This is not practical at X band and higher, however.
Thus, there is a need for a low-SWaP antenna system capable of transmitting and receiving more than one beam at a time, at more than one frequency, or with more than one polarization state.
Aspects of embodiments of the present disclosure are directed toward an array antenna including two or more interleaved array antennas, capable of being operated independently at a first frequency, or together, at a second frequency. Each of the array antennas is composed of alternating elements of an antenna array, and the arrays are interleaved. Each of the interleaved arrays may be operated independently, e.g., in either or both of the X band arrays, or the arrays may be driven together, as a single array with more densely spaced elements, e.g., in the Ku band.
According to an embodiment of the present invention there is provided an array antenna, including: a first plurality of antenna elements arranged in a first square pattern having a first grid spacing; a second plurality of antenna elements arranged in a second square pattern having a second grid spacing, the second grid spacing being the same as the first grid spacing, the antenna elements of the second plurality of antenna elements being interleaved with the antenna elements of the first plurality of antenna elements; a third plurality of antenna elements including the first plurality of antenna elements and the second plurality of antenna elements, the third plurality of antenna elements arranged in a third square pattern having a third grid spacing, the third square pattern being oriented at 45 degrees relative to the first square pattern and to the second square pattern, the third grid spacing being less than the first grid spacing by a factor of the square root of 2; a first feed network configured for transmitting and receiving signals through the first plurality of antenna elements; a second feed network configured for transmitting and receiving signals through the second plurality of antenna elements; and a third feed network configured for transmitting and receiving signals through the third plurality of antenna elements.
In one embodiment, each of the third plurality of antenna elements includes a notch radiator.
In one embodiment, each of the third plurality of antenna elements includes a flared notch radiator.
In one embodiment, each of the third plurality of antenna elements includes a stepped notch radiator.
In one embodiment, each of the third plurality of antenna elements includes a stacked patch radiator.
In one embodiment, each of the third plurality of antenna elements includes a dielectric material with a dielectric constant greater than 3.
In one embodiment, the first grid spacing is substantially equal to 0.484 inches.
In one embodiment, the first feed network is configured to operate at a frequency in the X band.
In one embodiment, the second feed network is configured to operate at a frequency in the X band.
In one embodiment, the third feed network is configured to operate at a frequency in the Ku band.
In one embodiment, the third feed network includes the first feed network and the second feed network, and wherein the first feed network, the second feed network, and the third feed network are configured to operate over a range of frequencies extending from a frequency in the X band to a frequency in the Ku band.
In one embodiment, the range of frequencies includes a first frequency and a second frequency, the second frequency being greater than the first frequency by a factor of the square root of 2.
In one embodiment, the first plurality of antenna elements is configured to radiate or receive a first polarization state, and the second plurality of antenna elements is configured to radiate or receive a second polarization state, the second polarization state being substantially different from the first polarization state.
In one embodiment, the first plurality of antenna elements is configured to radiate or receive a first polarization state, and the second plurality of antenna elements is configured to radiate or receive a second polarization state, the second polarization state being substantially orthogonal to the first polarization state.
In one embodiment, the first plurality of antenna elements is configured to radiate or receive a first polarization state, and the second plurality of antenna elements is configured to radiate or receive a second polarization state, the first polarization state being circular polarization with a first chirality, the second polarization state being circular polarization with a second chirality, and the first chirality being different from the second chirality.
In one embodiment, each of the antenna elements of the first plurality of antenna elements, and of the second plurality of antenna elements includes a transmit-receive module.
In one embodiment, each of the antenna elements of the first plurality of antenna elements and of the second plurality of antenna elements includes: a first transmit-receive module; a second transmit-receive module; and a plurality of switches, configured to connect the antenna element either to the first transmit-receive module or to the second transmit-receive module.
In one embodiment, the plurality of switches includes a p-type/intrinsic/n-type diode (PIN diode) switch.
In one embodiment, the array includes: a first plurality of switches configured to selectively connect the first plurality of antenna elements either to the first feed network or to the third feed network; and a second plurality of switches configured to selectively connect the second plurality of antenna elements either to the second feed network or to the third feed network.
In one embodiment, the first plurality of switches includes a p-type/intrinsic/n-type diode (PIN diode) switch; and the second plurality of switches includes a p-type/intrinsic/n-type diode (PIN diode) switch.
Features, aspects, and embodiments are described in conjunction with the attached drawings, in which:
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of interleaved electronically scanned arrays provided in accordance with the present invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the features of the present invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.
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In one embodiment the antenna elements 210 included in the X1 pattern and the antenna elements 310 included in the X2 pattern are sufficiently small to fit into an interleaved pattern. This may be accomplished by constructing the antenna elements 105 with a suitable dielectric, having a sufficiently high dielectric constant to allow for effective operation of a device with small dimensions. Such a dielectric may be a ceramic material or another material loaded with a ceramic material. In one embodiment a dielectric material with a dielectric constant of 3.4 or greater, such as DUROIDâ„¢ 6006 or DUROIDâ„¢ 6010, available from Rogers Corporation of Rogers, Conn., with dielectric constants of 6.45 and 10.7 respectively, may be used. The antenna elements 210, 310 may be fabricated on printed wiring boards (PWBs), e.g., using stripline structures. In one embodiment, the antenna elements have effective operation in both bands of interest.
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In other embodiments, the switch matrix 815 may contain, or may be replaced by a circuit containing, additional power dividers or power combiners allowing the common connections 515, 615, 715 to be connected simultaneously to the antenna elements 105. Each antenna element 105 may include a configuration of conductors and dielectric components for coupling conducted waves to electromagnetic radiation propagating in free space. Each antenna element 105 may be passive or it may be active, including for example a transmit-receive module (T/R module) with a power amplifier for transmitting and a low-noise amplifier for receiving.
In the embodiment of
A feed network designed to operate over a broad range of frequencies or at two widely separated frequencies (e.g., using Wilkinson power dividers with intermediate path lengths) may have reduced performance compared to a feed network designed for a single frequency. In one embodiment of the present invention, three independent feed networks are provided, each designed for a narrow operating frequency range, e.g., X band or Ku band, and switches are used to connect, at any given time, the feed networks to respective subsets, 210, 310, or 410, of the set of antenna elements 105, so that the array antenna operates, with high performance, at one frequency at a time. In another embodiment, a monolithic microwave integrated circuit (MMIC) at each antenna element 105 may be used to control the gain and phase (e.g., using a shifter chain) of the transmitted and received signals. A MMIC capable of operating at two operating frequencies may be used, or the MMIC may contain switches for routing the transmit and receive signals through one of two paths, e.g., two shifter chains, each of which may be optimized for one frequency. In this embodiment the antenna may operate at only one frequency at a time, and the switching may be used to reconfigure the antenna for the frequency in use at any time. In another embodiment the system may contain two MMICs at each antenna element, one for each operating frequency, and switches to route the signal to one MMIC or the other, again controlled so as to reconfigure the antenna for the frequency in use at any time.
The switches may be p-type/intrinsic/n-type diodes (PIN diodes). Each of the feed networks 510, 610, 710 may be a corporate feed as illustrated in
Embodiments of the present invention have applications in various systems employing array antennas, including radar. In a radar system, for example, it may be advantageous to operate two independent X-band antennas to provide two independently steerable radar beams, for simultaneously tracking two different objects, and a Ku-band antenna may be operated simultaneously to provide better radar resolution in a third beam. The X-band antennas may be operated at the same frequency, or at different frequencies within the X band. The X-band beams may not achieve the resolution of a Ku-band beam, but they may achieve greater range. In other embodiments it may be advantageous to configure the antenna elements 210 included in the X1 pattern to operate in a first polarization state and the antenna elements 310 included in the X2 pattern to operate in a second polarization state, so that, e.g., a radar target which alters the polarization state of electromagnetic waves upon reflection may be illuminated by a beam transmitted by the antenna elements 210 and may produce radar returns efficiently received by the antenna elements 310. The first and second polarization states may differ substantially, e.g., they may be orthogonal, such as two orthogonal linear polarizations, or two circular polarizations of different chirality, one being right circularly polarized and the other being left circularly polarized.
Although limited embodiments of interleaved electronically scanned arrays have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that interleaved electronically scanned arrays employed according to principles of this invention may be embodied other than as specifically described herein. The invention is also defined in the following claims, and equivalents thereof.
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Number | Date | Country | |
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