Wideband dual-polarized current loop antenna element

A wideband dual-polarized current loop antenna element is provided having a ground tower and an antenna circuit integrated, such as within a multi-layer circuit board configuration. The antenna circuit includes feed conductors and element conductors, each of which are capacitively coupled to a top ground plane of the ground tower. The feed conductors are coupled to receive signals from coaxial feed lines coupled to the respective antenna element and element conductors are coupled to receive signals from adjacent antenna elements, such as in an antenna array configuration. The antenna element can further include one or more frequency selective surface (FSS) layers disposed proximate to the top ground plane of the ground tower and the antenna circuit. The ground tower, antenna circuit and one or more FSS layers can be formed to provide a low-profile antenna element having wide broadband performance.

BACKGROUND

As is known in the art, in array antennas, performance is often limited by the size and bandwidth limitations of the antenna elements which make up the array. Further, packaging volume constraints often require low profile antenna structures. Improving bandwidth while maintaining a low profile, which meets volume constraints, enables array system performance to meet bandwidth, scan, and volume packaging requirements of next generation communication systems, such as software defined or cognitive radio.

Attempts have been made to fabricate low profile antenna elements and array antennas. Such array antennas include an array of tightly coupled dipole elements which approximates the performance of an ideal current sheet, as well as so-called “bunny ear” antennas, and tightly coupled patch arrays. While these antenna element designs are all low profile, they either fail to operate over a desired bandwidth or require complex feed structures to support either dual linear or circular polarizations (e.g. requiring external components difficult to fit within the antenna element of an array antenna). Other antenna elements, such as Vivaldi notch antenna elements, can provide a relatively wide bandwidth, but are not low profile.

SUMMARY

In accordance with the concepts, systems, methods and techniques described herein a wideband current loop antenna element is provided having a ground tower and an antenna circuit integrated within a multi-layer circuit board design. The antenna circuit includes one or more feed conductors and one or more element conductors, each of which are capacitively coupled to a top ground plane of the ground tower. The feed conductors are disposed so as to couple signals to and/or from one or more coaxial feed lines which serve as input/output signal paths to the current loop antenna element. In embodiments, the wide band current loop antenna element may be provided having a pair of coaxial feed lines so as to provide the wideband current loop antenna element as a dual polarized wideband current loop antenna element.

When a plurality of such antenna elements are disposed to provide an array, the element conductors are coupled to receive signals from adjacent antenna elements, such as in an antenna array configuration.

The antenna element can further include one or more frequency selective surface (FSS) layers disposed proximate to the top ground plane of the ground tower and the antenna circuit (i.e., horizontal antenna circuit, whereby the antenna circuit is horizontal with respect to the ground tower). In an embodiment, the ground tower, antenna circuit and one or more FSS layers can be formed to provide a low-profile antenna element having broadband performance characteristics.

The ground tower (or ground structure) includes first and second ground planes (e.g., top and bottom ground planes) spaced apart and coupled together through one or more ground vias. Thus, in the antenna elements described herein each of the ground vias can be coupled to the same ground planes, as compared to typical antenna element designs having multiple or separate vertical grounding paths. The ground tower can be a vertical ground structure as it extends from the first ground plane to the second ground plane along a vertical distance within a unit cell forming the antenna element. As the ground tower can be coupled at the top and bottom of the vertical via structure within the antenna element (or within a unit cell of the antenna element), a shorter radio frequency (RF) ground path length, as compared to ground structures used in other low profile antenna elements, can be provided.

In an embodiment, the shorter RF ground path length can improve the high frequency performance of the antenna element and inhibit propagation of surface waves. High frequency may refer to a frequency in the range of about 2 GHz to about 50 GHZ (e.g., from the S-band range to the Q-band range). In some embodiments, high frequency may refer to frequencies above the Q-band frequency range. It should be appreciated that the antenna elements as described herein can be scaled to a variety of different frequencies with such frequencies selected based upon the needs of a particular application in which the antenna or antenna element is being used as well as upon capabilities of manufacturing technologies (e.g., printed wiring board (PWB) processing technology).

The feed conductors and the element conductors can be formed at substantially the same level (or same layer) within the antenna element such that they are spaced substantially the same distance from the second ground plane of the ground tower. In some embodiments, the feed conductors and the element conductors are separated by the second ground plane by one or more dielectric region. For example, in one embodiment, the feed conductors and the element conductors can be formed on or otherwise coupled to a first surface of a dielectric region and the second ground plane can be formed on or otherwise coupled to a second, different surface of the dielectric region. Each of the feed conductors and the element conductors can be capacitively coupled to the second ground plane. Thus, in some embodiment, there is no direct connection between the feed conductors and element conductors and the ground tower to provide improvement in low frequency isolation and cross-polarization performance.

The feed conductors may include first and second feed conductors coupled to receive RF signals from first and second coaxial feed lines respectively though first and second signal vias to provide dual polarization. For example, the second coaxial feed line can be configured to couple RF signals orthogonal to RF signals coupled to the first feed conductor by the first coaxial feed line such that the antenna element is responsive to RF signals having dual linear polarizations. The signal vias can be formed through one or more dielectric regions to couple the coaxial feed lines to the feed conductors. In an embodiment, the signal vias can be formed substantially parallel to the ground vias within the antenna element.

The element conductors may include first and second element conductors coupled to receive RF signals from adjacent antenna elements. For example, in an array antenna design, a portion (e.g., feed portion) of each of the element conductors can extend into adjacent antenna elements in the array. Thus, the first and second element conductors can be coupled through their respective feed portions to coaxial feed lines different antenna elements within the array.

The one or more FSS layers can be disposed proximate to the second ground plane, feed conductors and element conductors. In some embodiments, the one or more FSS layers may include wide angle impedance matching (WAIM) layers. The one or more FSS layers may include a plurality of selective regions (e.g., patch, slots, apertures). The selective regions can be configured to reflect or transmit signals from the antenna element at a frequency of interest or a band of frequencies of interest. In some embodiments, each of the selective regions may have the same geometric shape, such as but not limited to, a rectangular shape, a square shape, a circular shape. In embodiments having multiple FSS layers, the FSS layers can be disposed such that they are cascaded with respect to each other and separated by one or more dielectric regions.

Thus, a low profile, dual polarized, low cost antenna element that achieves wideband frequency and wide scan volume performance is provided. For example, the height (or depth, profile) of antenna elements described here having a combination of the ground tower, antenna circuit and FSS layers is relatively low compared with the profile of prior art antenna elements and array antennas having similar operating characteristics. In an embodiment, a height (or depth, profile) of a particular antenna element can be selected based at least in part on a desired bandwidth. For example, in applications requiring less bandwidth, the height of the antenna element can be reduced. For application requiring greater bandwidth, the height of the antenna element can be increased.

In a first aspect a radio frequency (RF) antenna element includes a ground tower having a first ground plane spaced from a second ground plane, the first and second ground planes coupled together through one or more ground vias, a first coaxial feed line coupled to provide signals to a first feed conductor, a second coaxial feed line coupled to provide signals to a second feed conductor, and first and second element conductors responsive to signals provided thereto. In an embodiment, the first and second feed conductors and first and second element conductors are capacitively coupled to the same second ground plane, producing a single ground structure within the unit cell.

With this particular arrangement, an antenna element capable of operating over a wide range of frequencies and a wide scan volume while maintaining a low profile is provided.

The antenna element may further include one or more frequency selective surface layers disposed proximate to the second ground plane, first and second feed conductors and first and second element conductors. Each of the one or more frequency selective surface layers can include a plurality of selective regions. In some embodiments, each of the selective regions have the same geometric shape.

The first and second feed conductors can be spaced a predetermined distance from the second ground plane in a vertical direction and/or a horizontal direction. In some embodiments, the first and second feed conductors and first and second element conductors are separated from the second ground plane by a dielectric region. The first and second feed conductors can have the same geometric shape and the first and second element conductors can have the same geometric shape.

The first and second element conductors can be coupled to receive signals from coaxial feed lines in adjacent antenna elements. In some embodiments, the first and second element conductors are spaced a predetermined distance from each other.

The second coaxial feed line can couples RF signals to the second feed conductor which are orthogonal to RF signals coupled to the first feed conductor by the first coaxial feed line such that the antenna element is responsive to RF signals having dual linear polarizations.

In another aspect, a multi-layered circuit board includes an element layer having first and second feed conductors and first and second element conductors and a first ground layer spaced from a second ground layer. The first and second ground layers coupled together through one or more ground vias and the second ground layer can be spaced from the element layer by a first dielectric region. The multi-layered circuit board may further include a second dielectric region disposed between the first and second ground layers, with the one or more ground vias are formed through the second dielectric region, and first and second coaxial feed lines coupled to provide signal to the first and second feed conductors receptively. The first and second coaxial feed lines are coupled to the first and second feed conductors through first and second signal vias formed through the first and second dielectric regions.

The second dielectric region may include a plurality of dielectric regions, and each of the dielectric regions can be coupled together by one or more adhesive layers. In some embodiments, each of the plurality of dielectric regions may include a conductive layer.

One or more frequency selective surface layers can be disposed proximate to the second ground plane, first and second feed conductors and the first and second element conductors. In some embodiments, one or more substrate layers, one or more dielectric regions and/or one or more adhesive layers disposed between the one or more frequency selective surface layers. The one or more frequency selective surface layers can include a plurality of selective regions. In some embodiments, the selective regions can have the same geometric shape.

The first and second signal vias can be disposed parallel to the one or more ground vias. The first and second feed conductors can be spaced a predetermined distance from the second ground plane in a vertical direction and a horizontal direction. The first and second element conductors can be coupled to receive signals from coaxial feed lines in adjacent antenna elements.

In another aspect, an array antenna includes a plurality of antenna elements. Each of the antenna elements includes a ground tower having a first ground plane spaced from a second ground plane, the first and second ground planes coupled together through one or more ground vias, a first coaxial feed line coupled to provide signals to a first feed conductor, a second coaxial feed line coupled to provide signals to a second feed conductor, and first and second element conductors spaced from each other; the first and second element conductors responsive to signals provided thereto. The first and second feed conductors and first and second element conductors are capacitively coupled to the second ground plane.

Each of the plurality of antenna elements may include one or more frequency selective surface layers disposed proximate to the second ground plane, first and second feed conductors and first and second element conductors. The first and second feed conductors and first and second element conductors can be separated from the second ground plane by a dielectric region in each of the plurality of antenna elements.

DETAILED DESCRIPTION

Referring now toFIG. 1, an antenna element100includes first and second portions130,140with first portion130having a ground tower111, an antenna circuit101(e.g., an element conductors107a,107band feed circuits105) and second portion140having one or more frequency selective surface (FSS) layers116a,116bwith two such layers here being shown. For reasons which will become apparent herein below, such an arrangement results in an antenna element having a relatively low-profile and which is capable of operating over a frequency bandwidth and scan volume which are relatively wide compared with prior art antennas having a similar low profile.

Ground tower111includes a first ground plane110, a second ground plane112and a plurality of ground vias (i.e., electrically conductive vias)114a-114c(here three) coupling first ground plane110to second ground plane112. In some embodiments, first ground plane110is a backplane of antenna element100. In other embodiments, first ground plane110can be a conductive layer formed over a backplane of antenna element100.

It should be appreciated that ground tower111can include any number of ground vias114, based at least in part on properties of the respective antenna element and/or a particular application of the antenna element. For example, in some embodiments, ground tower111may include four ground vias114coupling first ground plane110to second ground plane112.

Ground tower111can be formed as a vertical ground structure such that it extends in a vertical direction from the first ground plane110to the second ground plane112within antenna element100. In an embodiment, ground tower111can be integrated within antenna element100to form one or more layers of a multi-layer circuit board. For example, each of first and second ground planes110,112and feed conductors106a,106bcan be formed at different levels within the multi-layer circuit board configuration, as will be described in greater detail below with respect toFIG. 2.

Feed circuit105includes first and second feed conductors106a,106bcoupled to first and second coaxial feed lines102a,102bthrough first and second signal vias104a,104b, respectively. In an embodiment, first and second feed conductors106a,106band element conductors (e.g., element conductors107a,107bofFIGS. 3-3B) can form a horizontal antenna circuit101within first portion130(horizontal with respect to ground tower111), as will be described in greater detail below.

First and second feed conductors106a,106bcan be disposed and coupled to different coaxial feed lines so as to allow antenna element100to receive orthogonally polarized radio frequency (RF) signals. For example, and as illustrated inFIG. 1, first feed conductor106ais coupled to first coaxial feed line102athrough a first signal via104aand second feed conductor106bis coupled to second coaxial feed line102bthrough a second signal via104b. First and second coaxial feed lines102a,102bmay include coaxial feeds.

First and second feed conductors106a,106bcan be capacitively coupled to the second ground plane112of ground tower111. For example, in some embodiments, first and second feed conductors106a,106bcan be spaced a predetermined distance from second ground plane112in a vertical direction, horizontal direction or both. In some embodiments, each of first and second feed conductors106a,106b, first and second signal vias104a,104b, and first and second feed lines102a,102bare spaced a predetermined distance from ground tower111and thus, there is not direct physical connection between the components of ground tower111(e.g., first and second ground planes110,112, plurality of ground vias114a-114c) and first and second feed conductors106a,106b, first and second signal vias104a,104b, and first and second feed lines102a,102b.

First and second feed conductors106a,106bmay be provided from any electrical conductor (e.g., a metallic material) or any material electrically responsive to RF signals provided thereto. First and second feed conductors106a,106bmay be formed having the same or substantially same geometric shape. In other embodiments, first and second feed conductors106a,106bmay have different geometric shapes. It should be appreciated that first and second feed conductors106a,106bmay be formed in a variety of different shapes, including but not limited to any regular or irregular geometric shape. The shape of first and second feed conductors106a,106bcan be selected based, at least in part, on the dimensions of antenna element100and/or a particular application of antenna element100.

One or more frequency selective surface (FSS) layers116a,116bcan be disposed within antenna element100. For example, and as illustrated inFIG. 1, first and second FSS layers116a,116bare disposed proximate to (e.g., over) first and second feed conductors106a,106band second ground plane112. In some embodiments, FSS layers116a,116bmay include wide amplitude impedance matching (WAIM) layers. FSS layers116a,116bwill be described in greater detail below with respect toFIG. 4.

Antenna element100may be provided having one or more dielectric regions120a-120idisposed between different layers to provide separation between the respective layers (e.g., dielectric spacing). For example, in some embodiments, a predetermined distance between two or more layers may correspond to a thickness of one or more of dielectric regions120a-120i. In one embodiment, first and second feed conductors106a,106bcan be dielectrically spaced from second ground plane112.

Dielectric regions120a-120ican be coupled together using adhesive layers124a-124g, as illustrated inFIG. 2. In some embodiments, conductive layers (e.g., metal layers) may be formed on (e.g., using any additive or subtractive PWB processing techniques) or otherwise coupled to one or more surfaces of the dielectric regions120a-120i. For example, second ground plane112may be provided as conductive layer formed on a surface of a dielectric region, as will be discussed in greater detail with respect toFIG. 2. Dielectric regions120a-120iand adhesive layers124a-124gwill be described in greater detail below with respect toFIG. 2.

In an embodiment, the space between first and second feed conductors106aand106bto second ground plane112can include a dielectric (e.g., one or more of dielectric regions120a-120i). However, in other embodiments, the dielectric material on either side of first and second feed conductors106aand106bcan be removed to improve radiator performance by producing a lower dielectric constant in the cavity surrounding the ground tower structure111of the unit cell of the antenna element100.

First and second ground planes110,112may be provided from any electrical conductive material (e.g., a metallic material).

First and second coaxial feed lines (or more simply “coaxial feeds”)102a,102bmay be provided having an outer conductor and a center conductor separated from the outer conductor by a dielectric (e.g., air or a dielectric material sometimes referred to as a dielectric jacket). In some embodiments, a center conductor of each of first and second coaxial feed lines102a,102bcan be coupled to first and second signals vias104a,104brespectively. For example, a portion of the outer conductor can be removed to expose the center conductor and dielectric and the center conductor can be directly coupled the respective signal via. In an embodiment, the dielectric may prevent the center conductor from contacting any portions of ground tower111. In other embodiments, the outer conductor may stop at a surface of the backplane of antenna element100and thus the dielectric may isolate the center conductor from first ground plane100. In other embodiments, the outer conductor may extend into antenna element100and thus through ground plane110and/or a backplane of antenna element100. In such an embodiment, an interface (e.g., interface103a,103bofFIG. 2) may be used to isolate coaxial feed lines102a,102bfrom first ground plane100. The interface103a,103bwill be described in greater detail below with respect toFIG. 2.

First and second coaxial feed lines102a,102bmay be provided as feeds from different coaxial feed circuits. It should be appreciated that although first and second coaxial feed lines102a,102bare described herein as coaxial feed lines, those of ordinary skill it the art will recognize that coaxial feed lines102a,102bmay be provided as one of a variety of different types of transmission lines including but not limited to any type of strip transmission line (e.g. a flex line, a microstrip line, a stripline, or the like). In still other embodiments, the coaxial feed lines102a,102bmay be provided as conductive via hole (or more simply “a via”), a probe, or an exposed center conductor of a coaxial line. In still other embodiments, the coaxial feed lines102a,102bmay be provided as a coplanar waveguide feed line (either with or without a ground) or from as a slotline feed line. Those of ordinary skill in the art will understand how to select the particular manner in which to implement (fabricate) coaxial feed lines102a,102bfor a particular application. Some factors to consider in selecting the type of feed line to use for a particular application include but are not limited to frequency of operation, fabrication simplicity, cost, reliability, operating environment (e.g. operating and storage temperature ranges, vibration profiles, etc.).

Now referring toFIG. 2, in which like elements ofFIG. 1are provided having like reference numerals, antenna element100includes a first portion (or bottom portion)130and a second portion (or top portion)140. Each of first portion130and second portion140include one or more one or more dielectric layers120a-120idisposed between different components or layers of antenna element100to provide dielectric spacing.

In an embodiment, first portion130and second portion140can be described having a multi-layer circuit board configuration. For example, first portion130includes feed conductors106a,160bdisposed at an element layer (or antenna circuit level), second ground plane112disposed at a second ground layer and first ground plane110disposed at a first ground layer. Further, one or more dielectric regions120a-120ican be disposed between the element layer, second ground layer and/or first ground layer. Second portion140includes multiple FSS layers116a,116bwith a combination of dielectric regions120a-120i, substrate layers122a-122ddisposed between and/or proximate to them.

As illustrated inFIG. 2, first portion130includes multiple dielectric regions with a first dielectric region120adisposed over a first surface110aof a first ground plane110(e.g., metal backplane). First dielectric region120ais coupled to a second dielectric region120bby a first adhesive layer124aand second dielectric region120bis coupled to a third dielectric region120cby a second adhesive layer124b. Third dielectric region120cis coupled to a fourth dielectric region120dby a third adhesive layer124cand fourth dielectric region120dis coupled to a fifth dielectric region120eby a fourth adhesive layer124d.

Second ground plane112may be formed on or otherwise coupled to a surface of fourth adhesive layer124d. For example, and as illustrated inFIG. 2, second ground plane112is coupled to a second surface of fourth dielectric region124d″. Thus, second ground plane112is disposed between the second surface124d″ of fourth adhesive layer124dand a first surface120e′ of fifth dielectric region120e.

First and second feed conductors106a,106bare coupled to or otherwise formed on a second surface of120e″ of fifth dielectric region120e. Thus, in the illustrative embodiment ofFIG. 2, first and second feed conductors106a,106bare spaced from second ground plane112by fifth dielectric region120e.

It should be appreciated that first and second element conductors107a,107b(as illustrated inFIGS. 3-3B) can be coupled to the second surface of120e″ of fifth dielectric region120eand disposed at the same level within antenna element100as first and second feed conductors106a,106b. Thus, in some embodiments, a distance between first and second feed conductors106a,106band first and second element conductors107a,107bmay correspond to a thickness of one or more dielectric regions, here fifth dielectric region120e. First and second feed conductors16a,106band first and second element conductors107a,107bcan form a horizontal antenna circuit101at an element level within antenna element100.

In first portion130, first and second ground planes110,112are coupled together through one or more ground vias114(here one). Although one ground via is illustrated inFIG. 2, it should be appreciated that first and second ground planes110,112can be coupled together through a plurality of ground vias114. Ground via114is formed through dielectric regions120a-120dand adhesive layers124a-124c. Ground via114and first and second ground planes110,112form ground tower111within first portion130.

First coaxial feed line102ais coupled to first feed conductor106athrough a first signal via104a. In an embodiment, first signal via104ais formed through dielectric layers120a-120eand adhesive layers124a-124c. In an embodiment, first coaxial feed line102aand first signal via104ado not physically contact first ground plane210. For example, a hole or interface103amay be formed in first ground plane110to isolate first coaxial feed line102aand first signal via104afrom first ground plane110. In an embodiment, interface103amay be provided as a metal plate having an aperture (or hole) sized to allow or otherwise fit first coaxial feed line102athrough. In other embodiments, interface103acan include additional vertical via structures formed within antenna element100or a variety of different types of connectors, such as but not limited to molded connectors, to first coaxial feed line102ato antenna element100. In some embodiments, first coaxial feed line102acan be machined coupled to antenna element100.

Second coaxial feed line102bis coupled to a second feed conductor106bthrough a second signal via104a. Second signal via104bis formed through dielectric layers120a-120eand adhesive layers124a-124c. In an embodiment, first and second signal vias104a,104bcan be formed such that they are substantially parallel to ground via114. A hole or interface103bcan be formed in first ground plane110to isolate second coaxial feed line102band second signal via104bfrom first ground plane110. Thus, second coaxial feed line102band second signal via104bdo not physically contact first ground plane110. In an embodiment, interface103bmay be provided as a metal plate having an aperture (or hole) sized to allow or otherwise fit second coaxial feed line102bthrough. In other embodiments, interface103bcan include additional vertical via structures formed within antenna element100or a variety of different types of connectors, such as but not limited to molded connectors, to second coaxial feed line102bto antenna element100. In some embodiments, second coaxial feed line102bcan be machined coupled to antenna element100.

Second portion140may include dielectric regions120, adhesive layers124, substrate layers122, FSS layers116or one or more combinations of them. For example, and as illustrated inFIG. 2, a first substrate layer122ais disposed on or otherwise on first and second feed conductors106a,106band portions of fifth dielectric layer120e. In an embodiment, an adhesive layer124may be provided between first substrate layer122aand first and second feed conductors106a,106band portions of fifth dielectric layer120e.

First substrate layer122ais coupled to a sixth dielectric region120fby a fifth adhesive layer124e. A first FSS layer116amay be formed on or otherwise coupled to a second surface120f′ of sixth dielectric region120f. In some embodiments, first FSS layer116amay be formed over a portion of second surface120f′ (e.g., not the entire second surface) of sixth dielectric region120f. First FSS layer116awill be described in greater detail below with respect toFIG. 4.

A second substrate layer122bis coupled to or otherwise formed over first FSS layer116aand/or portions of second surface120f′ sixth dielectric region120f. Second substrate layer122bis coupled to a seventh dielectric region120gby a sixth adhesive layer124f. A second FSS layer116bmay be formed on or otherwise coupled to a second surface120g″ of seventh dielectric region120g. In some embodiments, second FSS layer116bmay be formed over a portion of second surface120g″ (e.g., not the entire second surface) of seventh dielectric region120g. Second FSS layer116bwill be described in greater detail below with respect toFIG. 4.

A third substrate layer122cis coupled to or otherwise formed over second FSS layer116band/or portions of second surface120g″ seventh dielectric region120g. A fourth substrate layer122dis coupled to third substrate layer122cby a seventh adhesive layer124g.

It should be appreciated thatFIG. 2illustrates one example embodiment of antenna element100and that antenna element100and thus each of first portion130and second portion140can formed having one or more dielectric regions120, one or more adhesive layers124and/or one or more substrate layers122. For example, in some embodiments, the number of regions and/or layers can correspond to a desired height (or depth) the respective antenna element. The height can be selected based at least in part on a desired bandwidth for the antenna element. For applications requiring less bandwidth, the height of the antenna element can be reduced and for application requiring greater bandwidth, the height of the antenna element can be increased. Thus, antenna element100can be formed having a low-profile while meeting required bandwidth and scan requirements of a particular application.

Dielectric regions120a-120imay include dielectric material. For example, in some embodiments, dielectric regions120a-120imay be provided from dielectric material of the type manufactured by Rogers Corporation, Rogers, Conn. laminate material (e.g., RO 4350, RO 4360, RO 5880 LZ, RO 6002, etc.).

Substrate layers122a-122dmay include various forms of structural foam materials or structural foam cores, such as but not limited to Rohacell structural foam (e.g., Rohacell 71).

Adhesive layers124a-124gmay include a variety of different forms of adhesive or glue materials used to bond or otherwise couple multiple layers together. For example, in some embodiments, adhesive layers124a-124gmay be provided in the form of prepreg sheets used to bond dielectric regions120a-120itogether, substrate layers122a-122dtogether or a combination of them.

Now referring toFIGS. 3-3B, in which like reference numerals indicate like elements and in which like elements ofFIG. 1are provided having like reference numerals, first portion130of antenna element100is illustrated with second portion140removed. As illustrated inFIGS. 3-3B, first and second element conductors107a,107bare disposed over second surface120e″ of fifth dielectric region120eand thus disposed at the same level as first and second feed conductors106a,106b.

First and second element conductors107a,107band first and second feed conductors106a,106bare spaced from second ground plane112by fifth dielectric region120e. Thus, first and second element conductors107a,107bcan be spaced the same distance from second ground plane112as first and second feed conductors106a,106b. In some embodiments, first and second element conductors107a,107band first and second feed conductors106a,106bcan be spaced from second ground plane112by multiple dielectric regions. First and second element conductors107a,107band first and second feed conductors106a,106bcan be capacitively coupled to second ground plane112.

It should be appreciated thatFIG. 3andFIG. 3A, both illustrate first portion300, just from different angles. For example,FIG. 3Aprovides a rotated view as compared toFIG. 3to better illustrate the multiple ground vias114a-114ccoupling first ground plane110to second ground plane112.

As illustrated inFIGS. 3-3A, first coaxial feed line102ais coupled to first element conductor306athrough a first signal via304aand a second feed line302bis coupled to a second element conductor306bthrough second signal via304b.

First and second ground planes110,112are spaced from each other by multiple dielectric regions120a-120dand adhesive layers124a-124c. First ground plane110may correspond to a backplane of first portion130and second ground plane112can be formed on a second surface124d″ of fourth adhesive layer124d. First, second and third ground vias114a,114b,114care formed through dielectric regions120a-120dand adhesive layers124a-124cto couple first and second ground planes110,112and form ground tower111.

The one or more of dielectric regions120a-120emay include conductive layers121a-121cdisposed over one or more surfaces of the respective dielectric regions120a-120e. Conductive layers121a-121ccan be provided within antenna element100to provide impedance matching functionality, improve loss performance (e.g., return loss, insertion loss) and maintain cross-polarization and port isolation. Conductive layers121a-121ccan be formed on dielectric regions disposed between first and second ground planes110,112.

In some embodiments, first and second ground planes110,112may be provided as conductive layers formed on a surface of a dielectric region (i.e., as discussed above with respect toFIG. 2). For example, first ground plane110can be a conductive layer formed over a backplane of antenna element100. Second ground plane can be a conductive layer formed over dielectric region120eand coupled to adhesive layer124d.

FIG. 3Bis a top view of first portion130ofFIGS. 3 and 3A. As illustrated inFIG. 3B, first and second element conductors107a,107bare orthogonally disposed (i.e., centerlines of each conductor are orthogonal) and are spaced from each other by a gap109. In an embodiment, first and second element conductors107a,107bcan be spaced from each other by gap109to improve electrical isolation and cross-polarization performance over scan of antenna element100, as compared to other antenna elements having similar operating characteristics. Thus, in an embodiment, the dimensions of gap109(i.e., the spacing or distance between first and second element conductors107a,107b) can be selected based at least in part on a particular application of antenna element100and desired performance requirements (e.g., cross-polarization isolation) of antenna element100.

As also illustrated inFIG. 3B, each of first and second feed conductors106a,106band first and second element conductors107a,107bare disposed over second surface120e″ of fifth dielectric region120eand spaced from each other along the second surface120e″ of fifth dielectric layer120e. For example, in one embodiment, first and second feed conductors106a,106band first and second element conductors107a,107bdo not contact each other (i.e., no physical connection). In the example ofFIG. 3B, conductors106a,106bare disposed on adjacent sides (or edges or adjacent sides of a unit cell) of the antenna element100.

Second ground plane112(shown here with dashed lines for clarity) is disposed under (i.e., opposing surface of dielectric substrate120efrom the surface on which conductors106a,106b,107a,107bare disposed) fifth dielectric region120esuch that each of first and second feed conductors106a,106band first and second element conductors107a,107bare spaced apart by a distance corresponding to a thickness of fifth dielectric region120efrom second ground plane112.

First and second element conductors107a,107bmay be provided from any electrical conductor (e.g., a metallic material, such as but not limited to copper) or any material electrically responsive to RF signals provided thereto. First and second element conductors107a,107bmay be formed having the same or substantially same geometric shape (e.g., knife-edge shape, rectangular shape, circular shape, etc.). In other embodiments, first and second element conductors107a,107bmay have different geometric shapes. It should be appreciated that first and second element conductors107a,107bmay be formed in a variety of different shapes, including but not limited to any regular or irregular geometric shape. The shape of first and second element conductors107a,107bcan be selected based, at least in part, on the dimensions of antenna element100and/or a particular application of antenna element100and a desired response to RF signals.

It should be appreciated that first and second element conductors107a,107bare not coupled to first or second coaxial feed lines102a,102bdisposed within first portion130. For example, and as illustrated inFIG. 3B, first and second element conductors107a,107bcan be coupled to coaxial feed lines and signal vias in adjacent antenna elements100′,100″ (e.g., adjacent to first portion130of antenna element100in an array configuration) and thus fed signals from the respective adjacent antenna elements100′,100″.

First and second element conductors107a,107bmay correspond to a different portion of feed conductors disposed in adjacent antenna elements100′,100″ and be coupled to feed conductors (feed points) in the adjacent antenna elements100′,100″. For example, and as illustrated inFIG. 3B, second element conductor107bcan be coupled to a feed conductor107b′ that is part of adjacent antenna element100′ and coupled to receive signals from coaxial feed lines in adjacent antenna element100′. First element conductor107acan be coupled to a feed conductor107a″ that is part of adjacent antenna element100″ and coupled to receive signals from coaxial feed lines in adjacent antenna element100″. In some embodiments, first element conductor107aand feed conductor107a″ can be a single conductor having portions disposed in two adjacent antenna elements, here antenna elements100,100″, and second element conductor107band feed conductor107b′ can be a single conductor having portions disposed in two adjacent antenna elements, here antenna elements100,100′. The array configuration will be described in greater detail below with respect toFIGS. 5-5A.

In some embodiments having a single antenna element100, one or more partial antenna element structures having a ground tower (e.g., ground tower111ofFIG. 1) and a feed circuit (e.g., feed circuit105ofFIG. 1) may be formed along one or more edges of the respective antenna element100. For example, in such embodiments, adjacent antenna elements100′,100″ may be formed as partial antenna element structures having a ground tower and feed circuit to provide feeds to first and second feed conductors107a,107b. In embodiments having a single antenna element100, the single antenna element100may be formed without first and second feed conductors106a,106bformed along first and second edges113a,113bof the respective antenna element100.

Now referring toFIG. 4, in which like elements ofFIG. 1are provided having like reference numerals, second portion140of antenna element100includes multiple dielectric regions120f-120g, substrate layers122a-122d, adhesive layers124e-124gand FSS layers116a-116b.

First and second FSS layers116a,116bare coupled to or otherwise formed on second surfaces120f′,120g″ of sixth and seventh dielectric regions120f,120grespectively. Each of first and second FSS layers116a,116binclude a plurality of selective regions117. Selective regions117may be provided as or include patches, slots, or apertures. Selective regions117can be configured to reflect or transmit signals from antenna element100at a frequency of interest or a band of frequencies of interest. In an embodiment, the frequency of interest or a band of frequencies of interest can be selected based at least in part on a particular application of antenna element100.

Selective regions117can be formed (e.g., using any additive or subtractive techniques, such as sputtering or patterning) on a surface of the respective dielectric region as a single layer and then bonded to a respective substrate layer (e.g., substrate layers122a-122d) disposed proximate to the surface of the respective dielectric region.

In some embodiments, each of selective regions117may have the same geometric shape, such as but not limited to, a rectangular shape, a square shape, a circular shape. In other embodiments, one or more selective regions117may have different geometric shapes.

It should be appreciated that althoughFIG. 4illustrates two FSS layers116a,116b, antenna element100can be formed having any number of FSS layers116. For example, in some embodiments, antenna element100may include a single FSS layer116. In other embodiments, antenna element100may include more than two FSS layers166. The number of FSS layers116included within a respective antenna element can be selected based at least in part on a particular application of the antenna element and/or design requirement of the antenna element (e.g., cost, height, complexity, etc.). In embodiments having multiple FSS layers116, the FSS layers116can be disposed such that they are cascaded with respect to each other and separated by one or more dielectric regions.

In some embodiments, dielectric regions120f-120gdisposed in second portion140may not include conductive layers (e.g., conductive layers121a-121cof first portion130). In other embodiments, dielectric regions120f-120gmay include conductive layers disposed over one or more surfaces of respective dielectric regions120f-120g.

Now referring toFIG. 5, an array antenna (hereinafter array)200includes a plurality of antenna elements201a-201p. Each of antenna elements201a-201pmay be the same as or substantially similar to antenna element100ofFIGS. 1-4.

As illustrated inFIG. 5, each of antenna elements201a-201pincludes a first portion230having a ground tower and horizontal antenna circuit components and a second portion240having one or more FSS layers. For example, first portion230includes first and second coaxial feed lines202a,202bcoupled to first and second feed conductors206a,206bthrough first and second signal vias204a,204b. The ground tower of first portion230includes a first ground plane210(here a backplane of array200) coupled to a second ground plane212by one or more ground vias214.

First portion230further includes one or more dielectric regions220and one or more adhesive layers224. In some embodiments, dielectric regions220and/or adhesive layers224can be disposed within first portion230as described above with respect to first portion130ofFIG. 2. However, it should be appreciated that first portion230can be formed having various configurations of dielectric regions220and/or adhesive layers224and varying numbers of dielectric regions220and/or adhesive layers224. In some embodiments, the configuration of and/or the number of dielectric regions220and/or adhesive layers224can be selected based at least in part on a particular application of array200and/or the properties of array200(e.g., mechanical and electrical characteristics including but not limited to height, depth, bandwidth).

First and second signal vias204a,204bcan be formed through dielectric regions220and adhesive layers224to couple first and second coaxial feed lines202a,202bto first and second feed conductors206a,206b, respectively. Ground vias214can be formed through dielectric regions220and adhesive layers224to couple first and second ground planes210,212together.

Second portion240includes first and second FSS layers216a,216bdisposed between a combination of substrate layers222, dielectric regions220, and adhesive layers224. In some embodiments, substrate layers222, dielectric regions220, and/or adhesive layers224can be disposed within second portion240as described above with respect to second portion140ofFIG. 2. However, it should be appreciated that second portion240can be formed having various configuration of FSS layers216, substrate layers222, dielectric regions220, and/or adhesive layers224and varying numbers of FSS layers216, substrate layers222, dielectric regions220, and/or adhesive layers224. In some embodiments, the configuration of and/or the number of FSS layers216, substrate layers222, dielectric regions220, and/or adhesive layers224can be selected based at least in part on a particular application of array200and/or the properties of array200(e.g., height, depth, bandwidth).

In the illustrative embodiment ofFIG. 5, first FSS layer216ais formed on (e.g., patterned on) or otherwise coupled to a second surface of a dielectric region220and second FSS layer216bis formed on (e.g., patterned on) or otherwise coupled to a second surface of a different dielectric region220. First and second FSS layers216a,216binclude one or more selective regions217. In some embodiments, the selective regions217of first and second FSS layers216a,216bcan have the same geometric shape. In other embodiments, the selective regions217of first FSS layer216acan have different geometric shapes than the selective regions217of second FSS layer216b.

In some embodiments, dielectric regions220and/or adhesive layers224formed in array200may extend through the first portions230of each of the antenna elements201a-201pwithin array200such that they share the respective dielectric regions220and/or adhesive layers224. In other embodiments, each of antenna elements201a-201pwithin array200may have separate dielectric regions220and/or adhesive layers224.

In some embodiments, dielectric regions220, substrate layers222and/or adhesive layers224formed in array200may extend through the second portions240of each of the antenna elements201a-201pwithin array200. In other embodiments, the second portions240of each of antenna elements201a-201pwithin array200may have separate dielectric regions220, substrate layers222and/or adhesive layers224.

Now referring toFIG. 5A, first portion230is shown with second portion240removed to expose a top surface of first portion230. As illustrated inFIG. 5A, each first portion230of each of antenna elements201a-201pincludes first and second element conductors207a,207b. First and second element conductors207a,207bmay be the same as or substantially similar to first and second element conductors107a,107bdescribed above with respect toFIGS. 3-3B.

First and second element conductors207a,207bare coupled to feed conductors (or feed points)206a′,206b′ disposed in adjacent antenna elements201b,201h, respectively. Thus, first and second element conductors207a,207bcan be fed signals from the adjacent antenna elements201b,201hwithin array200. For example, in some embodiments, first and second element conductors207a,207bare part of or extensions of feed conductors206a′,206b′ that extend into antenna element201a.

As illustrated inFIG. 5A, feed conductor206a′ is coupled to a coaxial feed line (not shown) through signal via204a′ within antenna element201b. Thus, signals provided to feed conductor206a′ by a coaxial feed line can be provided to first element conductor207a. Feed conductor206b′ is coupled to a coaxial feed line (not shown) through signal via204b′ within antenna element201h. Thus, signals provided to feed conductor206b′ by a coaxial feed line can be provided to second element conductor207b.

Each pairing of element conductors207a,207bwithin each of antenna elements201a-201pcan be spaced apart from each other a predetermined distance. The predetermined distance can be selected based at least in part on a particular application of array200and/or performance requirements (e.g., isolation requirements, cross-polarization performance over scan) of array200.

In some embodiments, one or more partial antenna element structures having a ground tower (e.g., ground tower111ofFIG. 1) and a feed circuit (e.g., feed circuit105ofFIG. 1) may be formed along one or more edges of array200to provide feeds for feed conductors106a,106bdisposed along the respective edges of array200. In other embodiment, feed conductors106a,106bdisposed along one or more edges of array200may be removed or otherwise not formed.