This disclosure is generally directed to radio frequency (RF) antennas and, more specifically to electromagnetic band gap structures (EBGs) utilized to reduce coupling between adjacent RF antennas.
An electromagnetic band-gap (EBG) structure is utilized to block electromagnetic waves in certain frequency bands. EBG structures are commonly utilized to prevent coupling between adjacent antennas within a particular frequency band. For antennas fabricated on printed circuit boards, a commonly utilized EBG structure is a three-dimensional (3D) mushroom-like structure in which a plate is connected to a ground plane via a metallic via. However, fabrication metallic vias in the numbers required increases the fabrication cost significantly. It would be beneficial to design an EBG structure that provides good performance in blocking electromagnetic waves within a certain frequency, hand but at a low fabrication cost.
According to one aspect, an electromagnetic band-gap (EBG) structure is provided that includes an antenna substrate and at least a first conductive region and second conductive region fabricated on the first planar surface of the antenna substrate. The first conductive regions are located on the first planar surface of the antenna substrate and separated from adjacent first conductive regions by a first distance. The second conductive regions are also located on the first planar surface, wherein the second conductive regions are separated from the first conductive regions by a second distance and wherein the second conductive regions at least partially surround the first conductive regions.
According to another aspect, a planar antenna board is provided that includes an antenna substrate layer, a top conductive layer, and a bottom conductive layer. The antenna substrate layer has a first planar surface and a second planar surface opposite the first planar surface. The top conductive layer is located on the first planar surface and the bottom conductive layer is located on the second planar surface. A first E-band antenna is fabricated in the top conductive layer, wherein the first E-band antenna configured to receive/transmit an E-band frequency radio frequency (RF) signal. A second E-band antenna is fabricated in the top conductive layer, the second E-band antenna configured to receive/transmit an E-band frequency RF signal, wherein the second E-band antenna is offset in the x-y plane from the first E-band antenna. A periodic array of two-dimensional electromagnetic band-gap (EBG) structures are also fabricated in the top conductive layer. The periodic array of 2D EBG structures is located between the first E-band antenna and the second E-band antenna, wherein each EBG structure includes a plurality of slots formed in the top conductive layer, wherein the periodic array of 2D EBG structures blocks surface waves in the E-band frequency range.
According to one aspect, this disclosure is directed to a two-dimensional electromagnetic band gap structure (EBG) utilized to reduce coupling between adjacent antennas elements. In particular, the EBGs are utilized on an antenna board (e.g., printed circuit boards) that includes at least a planar antenna substrate layer, a top conductive layer and a bottom conductive layer. A number of methods of fabricating antennas may be utilized. For example, in some embodiments antennas elements (i.e., radiating elements) are fabricated on the antenna board via selective etching of the top conductive layer. In other embodiments, rather than selectively etch a top conductive layer to leave a desired conductive pattern, the desired conductive pattern is selectively plated. In other embodiments, various other well-known fabrication techniques may be utilized to fabricate antenna structures, including plastic injection molding. The EBG structures are fabricated in the region between the adjacent antennas and include a repeating or periodic pattern of EBG structures. The EBG structures are likewise fabricated via the selective etching of the top conductive layer. The process of etching the top conductive layer to fabricate the EBG structures is the same as the process of etching the top conductive layer to fabricate the antennas, and thus does not present a substantial additional cost to the fabrication process. In particular, the fabrication process does not require modification of the underlying antenna substrate layer, while still providing the desired decoupling between the adjacent antennas.
Referring now to
In some embodiments, antenna board 100 may be utilized as part of a radar sensing system, in which transmission antenna 104 propagates an RF signal and receiving antenna 102 receives a reflection of the RF signal that is utilized to detect, range, and/or track objects. In other embodiments, antenna board 100 may be utilized in a multiple-input multiple output (MIMO) communication system that utilizing a plurality of transmission antennas and a plurality of receiving antennas to provide wireless communication between two points. For example, in the MIMO embodiments, rather than a transmission antenna 104 and a receiving antenna 102 located on the antenna board, but antennas 102, 104 may be receiving antennas and/or both may be transmission antennas (or both may be transceivers, capable of both transmitting and receiving RF signals). In some embodiments, the at least one receiving antenna 102 and the at least one transmission antenna 104 operate in the E-band, which extends from approximately 60 gigahertz (GHz) to 90 GHz. In particular, in some embodiments the at least one receiving antenna 102 and the at least one transmission antenna 104 operate in a frequency range of between approximately 72 GHz and 82 GHz, and in some embodiments operate in a frequency range of between 76 GHz and 78 GHz. EBG region 105 is designed to create a stopband within the operating frequency of the at least one receiving antenna 102 and the at least one transmission antenna 104 to decrease coupling between the respective antennas. In some embodiments, the stopband operates over the E-band range (e.g., 60 Ghz-90 GHz). In other embodiments, the EBG region 105 may be selected to provide a stopband in the frequency of range of between 72 GHz and 82 GHz, and in some embodiments operate in a frequency range of between 76 GHz and 78 GHz. Decreasing the mutual coupling between the respective antennas increases the performance of the respective antennas. For example, in embodiments utilizing the antennas for radar sensing, decreased coupling between the respective transmission antenna 104 and receiving antenna 102 reduces the noise floor associated with each antenna, thereby increasing the signal-to-noise (SNR) ratio of the radar sensing system and increasing the detection range of the radar sensing system.
In some embodiments, the plurality of EBG structures located in the EBG region 105 are fabricated by selectively etching (removing) conductive material from the top conductive layer 120. One benefit of the antenna board 100 shown in
The geometry of the EBG structures is selected to prevent the propagation of surface waves along the top conductive layer 120 between the at least one receiving antenna 102 and the at least one transmission antenna 104. For example, as discussed in more detail with respect to
Referring to
In the embodiment shown in
In the embodiment shown in
In some embodiments, a second plurality of conductive regions 204a-204d are located at least partially surrounding the first plurality of conductive regions 202a-202d. In some embodiments, the second plurality of conductive regions 204a-204d are L-shaped. For example, conductive region 204d includes a vertical portion 208 (i.e., extending in the y-direction) and a horizontal portion 210 (i.e., extending in the x-direction). The vertical portion 208 is separated from the conductive region 202d by a distance L7 and the horizontal portion 210 is separated from the conductive region 202d by a distance L8. In some embodiments, the distances L7 and L8 are equal to one another. In addition, in some embodiments each of the second plurality of conductive regions 204a-204d are separated from adjacent conductive regions 204a-204d in the y-direction by a distance L3 and in the x-direction by a distance L4. In some embodiments the distances L3 and L4 are equal to one another. In addition, in some embodiments the distance L9 between first conductive regions 202c and 202d is equal to the distance L4 between second conductive regions 204c and 204d; and the distance L6 between first conductive regions 202b and 202d is equal to the distance L3 between second conductive regions 204b and 204d. In some embodiments, distances L3, L4, L6, L7, L8 and L9 are approximately equal
The dimensions of the EBG structure 200 is selected based, at least in part, on the desired stopband. For example, in some embodiments the width of the etched slots, expressed in distances L3, L4, L6, L7, L8 and L9 shown in
In the embodiment shown in
In the embodiment shown in
Referring to
With respect to
In some embodiments, the width of the first and second horizontal slot 304a, 304b is defined by distance L12, and the width of the vertical slot 306 is defined by distance L13. In some embodiments, the distance L12 and L13 are approximately equal. The distance between the first and second horizontal slots 304a, 304b is defined by distance L14. In some embodiments, the distance L14 is greater than the width L12 and L13 of the slots. In some embodiments, the length of the EBG structure 300 is defined by distance L15 and the height of the EBG structure 300 is defined by distance L16. In some embodiments, the distance L15 is greater than the distance L16, such that the EBG structure 300 is rectangular in shape. In some embodiments, the distance L15 is approximately equal to the distance L16, such that the EBG structure 300 is approximately square in shape. In some embodiments, the distance L15 is equal to between 0.9 and 1.1 mm and the distance L16 is equal to between 0.6 and 0.8 mm. In some embodiments, the width of the slots L12 and L13 is between 0.1 and 0.2 mm, and the distance L14 between the first and second horizontal slots 304a, 304b is equal to between 0.3 to 0.4 mm.
In the embodiment shown in
Referring to
In the embodiment shown in
In some embodiments, the plurality of EBG regions 406a, 406b, 406c, and 406d reduces surface ripples between the adjacent antenna sticks 404a, 404b, and 404c, which improves the uniformity of the beam vectors generated by the MIMO antenna. This reduces the dissimilarity in the antenna radiation pattern and improves the angle-finding accuracy of the MIMO antenna board 400.
Referring to
In this way, the disclosed invention provides a 2D EBG structure for reducing coupling between adjacent antennas fabricated on planar antenna boards, such as slot antennas, stick antennas, and microstrip antennas. The 2D EBG structure is fabricated by etching slots in the top conductive layer in a repeating pattern but does not require modification of the underlying antenna substrate layer. As a result, the EBG structure is defined as 2D because it only requires fabrication (e.g., etching) of the top conductive layer of the planar antenna board. Fabrication of the 2D EBG structure can be performed in conjunction with etching utilized to fabricate the antenna slots and/or antenna sticks, and therefore does not add significantly to the overall cost of antenna board, while providing significant decoupling of antennas within E-band operating frequencies.
The following are non-exclusive descriptions of possible embodiments of the present invention.
According to one aspect, an electromagnetic band-gap (EBG) structure includes an antenna substrate layer having a first planar surface and first and second conductive regions fabricated on the first planar surface. The first conductive regions are separated from adjacent first conductive regions by a first distance. The second conductive regions are separated from the first conductive regions by a second distance and at least partially surround the first conductive regions.
The EBG structure of the preceding paragraph can optionally include, additionally and/or alternatively any, one or more of the following features, configurations and/or additional components.
For example, the EBG structure may include a bottom conductive layer located opposite of the first planar surface (adjacent to a second planar surface of the antenna substrate), wherein the first conductive regions and the second conductive regions are separated from the bottom conductive layer by the antenna substrate layer.
The first conductive regions may be separated from one another by slots formed that expose the antenna substrate layer. Likewise, the second conductive regions may be separated from the first conductive regions and from one another by slots formed to expose the antenna substrate layer.
The second conductive regions may have an ‘L’-shaped geometry.
The first conductive region may have a square geometry.
The first distance between the first conductive regions (i.e., a first distance) may be approximately equal to the second distance between the first conductive regions and the second conductive regions.
The second conductive regions may be separated from adjacent second conductive regions by a third distance.
The third distance may be equal to the first distance and the second distance.
The first conductive region may be defined by a first width and the second conductive region may be defined by a second width, wherein the second width may be equal to approximately one-half the first width.
According to another aspect, a planar antenna board includes an antenna substrate layer, a top conductive layer, and a bottom conductive layer. The antenna substrate layer has a first planar surface and a second planar surface opposite the first planar surface. The top conductive layer is located on the first planar surface and the bottom conductive layer is located on the second planar surface. A first E-band antenna is fabricated in the top conductive layer, wherein the first E-band antenna configured to receive/transmit an E-band frequency radio frequency (RF) signal. A second E-band antenna is fabricated in the top conductive layer, the second E-band antenna configured to receive/transmit an E-band frequency RF signal, wherein the second E-band antenna is offset in the x-y plane from the first E-band antenna. A periodic array of two-dimensional electromagnetic band-gap (EBG) structures are also fabricated in the top conductive layer. The periodic array of 2D EBG structures is located between the first E-band antenna and the second E-band antenna, wherein each EBG structure includes a plurality of slots formed in the top conductive layer, wherein the periodic array of 2D EBG structures blocks surface waves in the E-band frequency range.
The planar antenna board of the preceding paragraph can optionally include, additionally and/or alternatively any, one or more of the following features, configurations and/or additional components.
For example, each EBG structure may include a conductive region having an H-shaped slot formed within an interior of the conductive region.
The H-shaped slot may include a first slot, a second slot, and a third slot perpendicular to the first and second slots, wherein the third slot extends between a middle portion of the first and second slots.
Each EBG structure may include a first conductive regions located on the first planar surface of the antenna substrate and separated from adjacent first conductive regions by a first distance and second conductive regions located on the first planar surface, wherein the second conductive regions are separated from the first conductive regions by a second distance and wherein the second conductive regions at least partially surround the first conductive regions
The second conductive regions may have an ‘L’-shaped geometry.
The first conductive regions may have a square geometry.
The first distance may be approximately equal to the second distance.
The second conductive regions may be separated from adjacent second conductive regions by a third distance.
The third distance may be equal to the first distance and the second distance.
The first E-band antenna may be a transmission antenna and the second E-band antenna may be a receiving antenna utilized in a radar sensing system.
The first E-band antenna and the second E-band antenna may be utilized in a multiple-input multiple-output (MIMO) antenna system.
Number | Name | Date | Kind |
---|---|---|---|
6933812 | Sarabandi et al. | Aug 2005 | B2 |
7307596 | West | Dec 2007 | B1 |
7982673 | Orton et al. | Jul 2011 | B2 |
8004369 | Kwon et al. | Aug 2011 | B2 |
9219313 | Georgescu et al. | Dec 2015 | B2 |
9515387 | Hung et al. | Dec 2016 | B2 |
9711867 | Jecko et al. | Jul 2017 | B2 |
9865932 | Yukimasa | Jan 2018 | B2 |
20120280770 | Abhari | Nov 2012 | A1 |
20130207867 | Georgescu et al. | Aug 2013 | A1 |
20130214984 | Zaghloul et al. | Aug 2013 | A1 |
20130293323 | Nakase | Nov 2013 | A1 |
20160204514 | Miraftab | Jul 2016 | A1 |
20180090851 | Feldman | Mar 2018 | A1 |
20180102593 | Gong | Apr 2018 | A1 |
20190109361 | Ichinose | Apr 2019 | A1 |
20200287293 | Shi | Sep 2020 | A1 |
20200358173 | Jong | Nov 2020 | A1 |
Number | Date | Country |
---|---|---|
102510658 | Jun 2012 | CN |
102683826 | Sep 2012 | CN |
102820501 | Dec 2012 | CN |
103035460 | Apr 2013 | CN |
103687280 | Mar 2014 | CN |
102683826 | Apr 2014 | CN |
103943969 | Jul 2014 | CN |
104137333 | Nov 2014 | CN |
104332677 | Feb 2015 | CN |
104137333 | Mar 2017 | CN |
103687280 | Jul 2017 | CN |
109041413 | Dec 2018 | CN |
2008020249 | Feb 2008 | WO |
2019022651 | Jan 2019 | WO |
Entry |
---|
L. Yang, M. Fan, F. Chen, J. She, and Z. Feng, “A novel compact electromagnetic-bandgap (EBG) structure and its applications for microwave circuits,” IEEE Trans. Microw. Theory Tech., vol. 53, No. 1, pp. 183190, Jan. 2005. |
R. B. Waterhouse and D. Novak, “A Small electromagnetic bandgap structure,” Microwave Symposium Digest, IEEE MTT-S International, pp. 602 605, 2006. |
Felix D. Mbairi and Hjalmar Hesselbom. Microwave bandstop filters using novel arlificial periodic substrate electromagnetic band gap structures. Components and Packaging Technologies, IEEE Transactions on, 32:273282, 2009. |
Mohajer-Iravani, B. and O. M. Ramahi, “Wideband circuit model for planar EBG structures,” IEEE Trans. Adv. Packag., vol. 33, No. 2, 345354, May 2010. |
D. Sievenpiper, L. Zhang, R. F. J. Broas, N. G. Alexopolus, and E.Yablonovitch, “High-impedance electromagnetic surfaces with a forbidden frequency band,” IEEE Trans. Microwave Theory Tech., vol. 47, pp. 20592074, Nov. 1999. |
Kamadin K, Rahim MKA, Hall PS, Samsuri NA, Elias NA. Printed dipole with slot EBG structures with artificial magnetic conductor and band-notched behaviors. IEEE Int. RFM Conf. Seremban, Malaysia, Dec. 2011. |
Extended European Search Report for EP Application No. 21151765.1, dated Jun. 11, 2021, 21 pages. |
Assimonis, et al., “Design and Optimization of Uniplanar EBG Structures for Low Profile Antenna Applications and Mutual Coupling Reduction”, IEEE Transactions On Antennas and Propagation, IEEE Service Center, Piscataway, NJ, US, vol. 60, No. 10, XP011466636, ISSN: 0018-926X, DOI:10.1109/TAP.2012.2210178 Chapters I, II and III.B; figures 1,2, 10, 11; table I, Oct. 1, 2012, pp. 4944-4949. |
Number | Date | Country | |
---|---|---|---|
20210242581 A1 | Aug 2021 | US |