Patent Application
20200067183
The present application in general relates to antennas, and more specifically, a broadband dual-polarized microstrip antenna which uses an FR-4 substrate which has low cross-polarization and flat broadside gain.
For broadening the bandwidth of a microstrip antenna to over 50%, an aperture stacked patch approach may be taken. This approach may be effective for a dual polarization, since there is an inherent polarization purity associated.
The front-to-back ratio (FBR) in aperture coupled antennas is generally low. However, to achieve a flat broadside gain, a good FBR ratio for the whole bandwidth of the antenna should be maintained. This can be obtained by using a microstrip patch antenna, or a cross as a reflector in the back of an aperture-coupled stacked patch configuration. To minimize the coupling between the orthogonal polarizations in a dual polarized antenna, and in turn to maintain low cross polarization, a balanced feed can be used, which may involve a feed line branched into two traces to excite the antenna, and a cross-slot to couple both the feed lines for both polarizations to the antenna.
Classically, to achieve considerable bandwidth, its recommended to use a low permittivity, low loss substrate of high thickness. However, these types of substrates are more expensive than off-the-shelf thin FR4 material. Presently, it is difficult to achieve a good return loss and flat gain for a broadband and limited size antenna element using off-the-shelf thin FR4 material as the substrate for the antenna.
Therefore, it would be desirable to provide a system and method that overcomes the above. The system and method would provide a broadband dual-polarized antenna solution based on commercially available low-cost substrate.
In accordance with one embodiment, an antenna assembly is disclosed. The antenna assembly has a first antenna layer. A second antenna layer spaced apart from the first antenna layer. A feed layer is used to excite the first antenna layer and the second antenna layer. The feed layer is spaced apart from the second antenna layer. A reflective layer is spaced apart from the feed layer.
In accordance with one embodiment, an antenna assembly is disclosed. The antenna assembly has a first antenna layer. The first antenna layer has a first substrate. A first antenna element is formed on a bottom surface of the first substrate. A second antenna layer is spaced apart from the first antenna layer. The second antenna layer has a second substrate. A second antenna element is formed on a top surface of the second substrate. A first air spacer is positioned between the first antenna layer and the second antenna layer. The first antenna element and the second antenna element are positioned within the first air spacer. A feed layer is used to excite the first antenna layer and the second antenna layer. The feed layer is spaced apart from the second antenna layer. The feed layer has a third substrate. A first feed line is formed on the third substrate. A fourth substrate is provided. A second feed line is formed on the fourth substrate. A ground plane isolates the first feed line from the second feed line. A reflective layer is spaced apart from the feed layer. The reflective layer has a fifth substrate. A Jerusalem cross type reflector is formed on the fifth substrate. A second air spacer positioned between a second feed line and the a Jerusalem cross type reflector.
The present application is further detailed with respect to the following drawings. These figures are not intended to limit the scope of the present application but rather illustrate certain attributes thereof.
The description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the disclosure and is not intended to represent the only forms in which the present disclosure may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the disclosure in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of this disclosure.
Embodiments of the exemplary method and system may allow an antenna element to be built using a Commercial Off-The-Shelf (COTS) FR4 based substrate. To achieve bandwidth, a stacked patch may be used. An aperture-coupled configuration may be used for broadbanding. The antenna may use a special reflector to achieve a good front to back ratio required to maintain a flat gain.
For a broadband antenna, a thick substrate with low dielectric constant is generally preferred since it may lead to stronger fringing fields, which ultimately increases the radiated power. But the problem with thicker dielectric material with a low dielectric constant is that the substrate cost is generally higher. The thickness of the substrate can be reduced by using an air spacer. This may also help to lower the effective dielectric constant for a high dielectric constant material. But as the difference in dielectric constant increases, there may be more reflection at the interface of the dielectric substrate and the air spacer, which may make it challenging to keep the gain above prescribed levels in the required bandwidth. Although the air spacer height can be increased to reduce the effective dielectric constant, it cannot be increased over a certain limit since the coupling between the feed line and the antenna will become considerably poor.
Referring to
The first substrate 10001 may be a commercial off the shelf FR4 substrate 1000A. FR4 substrate 1000A may be formed of a glass-reinforced epoxy laminate material. The FR4 substrate 1000A may be formed of a composite material composed of woven fiberglass cloth with an epoxy resin binder. In accordance with one embodiment, the FR4 substrate 1000A may be approximately 21 mils in height.
A second antenna 1002 may be formed on a top surface of a second substrate 10002. In accordance with one embodiment, the second antenna 1002 may be a parasitic patch-type antenna. The second substrate 10002 may be a commercial off the shelf FR4 substrate 1000A. In accordance with one embodiment, the FR4 substrate 1000A may be approximately 21 mils in height.
The first antenna 1001 may be slightly smaller in size than the second antenna 1002. By having the first antenna 1001 slightly smaller in size than the second antenna 1002, one may be able to achieve two slightly different fundamental frequencies in them, as principle of broad banding using stacked-patches dictate.
The antenna 1001 on the bottom surface of the first substrate 10001, may be separated from the second antenna 1002 formed on the top surface of the second substrate 10002 by an air-spacer 2000. The first antenna 1001 and the second antenna 1002 may both be located within the air-spacer 2000. As may be seen in
The antenna assembly may have a feed layer 1003. The second antenna 1002 formed on a top surface of a second substrate 10002 may be separated from the feed layer 1003 of the antenna assembly by an air spacer 2001. The feed layer 1003 of the antenna assembly may have feedlines 10041 and 10042. The feed line 10041 may be formed on a top surface of a third substrate 10003. The feed line 10042 may be formed on a top surface of a fourth substrate 10004. The feed line 10041 may be formed on a top surface of a third substrate 10003 may be positioned within the air spacer 2001. The feedlines 10041 and 10042 may be used as X polarized) (Φ=0°) and Y polarized) (Φ=90°) balanced feed lines respectively. The feedlines 10041 and 10042 may be isolated by a solid ground plane 1005 with a cross-slot 1005A in a 4-layer board, which is comprised of the third substrate 10003 and fourth substrate 10004 coupled together.
In accordance with one embodiment, the feed line 10041 may be a single feed line 10041_A that branch off into two feed lines 10041_A_1 and 10041_A_2 that symmetrically distanced from the single feed line 10041_A. Similarly, the feed line 10042 may be a single feed line 10042 that branch off into two feed lines 10042_A_1 and 10042_A_1 that symmetrically distanced from the single feed line 10042_A. For example, the feed lines 10041 and 10042 may both be a 50 Ohm feed line that branches into two lines of 100 Ohms and are symmetrically distanced from the central 50 Ohm line.
In accordance with one embodiment, the third substrate 10003 and fourth substrate 10004 may be coupled together with an adhesive 3000. The cross-slot 1005 may give symmetry in the coupling of two feedlines 10041 and 10042 for each polarization, and makes the feed lines 10041 and 10042 balanced. In the above example, the cross-slot 1005 may give symmetry in the coupling of two 100 Ohms feedline branches of the feed lines 10041 and 10042. The two 100 Ohms feedline branches of the feed lines 10041 and 10042. May be symmetrically placed in different layers of the ground plane with the cross-slot 1005.
In accordance with one embodiment, the third substrate 10003 and the fourth substrate 10004 may both be a commercial off the shelf FR4 substrate 1000A. The FR4 substrate 1000A may be approximately 21 mils in height. In this embodiment, the third substrate 10003 and the fourth substrate 10004 may be coupled together with 2.8 mils thick adhesive 3000.
The antenna assembly may have a reflector layer 1006. The reflector layer 1006 may have a reflector 1007 formed on a top surface of a fifth substrate 10005. The fifth substrate 10005 may be a commercial off the shelf FR4 substrate 1000A. In accordance with one embodiment, the FR4 substrate 1000A may be approximately 21 mils in height. The reflector layer 1006 may be separated from the feed line 10042 by air spacer 2002. The reflector 1007 and the feed line 10042 may be positioned within the air spacer 2002.
In accordance with one embodiment, the reflector 1007 may be a Jerusalem cross-shaped reflector 1007A as may be seen in
A return loss plot for the X-polarized feed line 10041 may be seen in
The return loss plot for Y-polarized feed line 10042, may be illustrated in
The isolation between the two orthogonal feedlines 10041 and 10042 may be seen in
The foregoing description is illustrative of particular embodiments of the application, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the application.
| Number | Date | Country | |
|---|---|---|---|
| 62765329 | Aug 2018 | US |
