Patent Grant
12057646
Microstrip antennas (MSAs), introduced in 1953, and developed in the 1970s, exhibit many advantages including low profile, small volume, and easy as well as low cost printed circuit board (PCB) fabrication. Numerous designs have been introduced for various applications. Among these designs, MSAs that provide dual-band, multi-band, or wide-band operation have been studied, especially with the rapid development of mobile communication systems. Different approaches have been used to achieve these characteristics, such as slots, multiple elements, and parasitic elements. However, existing designs that provide isolation between feeds have high levels of complexity.
Embodiments of the subject invention provide novel and advantageous multi-band antennas (e.g., microstrip patch antennas), as well as methods of fabricating the same and methods of using the same. A decoupling technique can be used to design and fabricate multi-mode, multi-band, electrically compact, microstrip patch antennas (e.g., rectangular microstrip patch antennas). Strategically etched slots can be provided between the tightly coupled microstrip patch antennas, and the appropriate mode excitation of the corresponding patch antennas can be used. The antennas have high isolation between the frequency bands of operation. Multi-band operation can be achieved by exciting a different mode on each contiguous portion of the patch antenna. The antennas can be multi-mode, multi-band patch antennas that are electrically compact, low-profile, and simple to design and fabricate as compared to related approaches that use complex, large, and/or absorptive decoupling structures.
In an embodiment, a multi-band antenna can comprise: a substrate; a first patch antenna disposed on an upper surface of the substrate; a second patch antenna disposed on the upper surface of the substrate and physically separated from the first patch antenna by a gap; a first connector for connecting to an external power source or a load; a second connector for connecting to the external power source or the load; a first conductive line disposed on the upper surface of the substrate, the first conductive line being in direct physical contact with the first patch antenna and the first connector, and the first conductive line electrically connecting the first patch antenna and the first connector; and a second conductive line disposed on the upper surface of the substrate, the second conductive line being in direct physical contact with the second patch antenna and the second connector, and the second conductive line electrically connecting the second patch antenna and the second connector. The first patch antenna, the second patch antenna, the first conductive line, the second conductive line, the first connector, and/or the second conductor can be made of the same material (e.g., a conductive metal such as copper, gold, aluminum, silver, platinum, palladium, or a combination thereof). A cross-section of the first patch antenna (taken in a first plane parallel to the upper surface of the substrate) can have a rectangular shape and/or a cross-section of the second patch antenna (taken in the first plane) can have a rectangular shape. The first patch antenna can comprise four sides including a first side facing the second patch antenna and being closest to the second patch antenna out of the four sides of the first patch antenna; the second patch antenna can comprise four sides including a second side facing the first patch antenna and being closest to the first patch antenna out of the four sides of the second patch antenna; and a length of the first side of the first patch antenna can be equal to a length of the second side of the second patch antenna. The gap can be a smallest distance between the first patch antenna and the second patch antenna, measured in a first direction parallel to the upper surface of the substrate. A length of the first patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the gap, and a length of the second patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the gap. The length of the first patch antenna, measured in the first direction, can be larger (e.g., at least 1.1, 1.15, 1.2, 1.25, 1.3, 1.333, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.75, 1.8, 1.9, 2 or more times larger) than the length of the second patch antenna, measured in the first direction. The substrate can comprise a first edge, a second edge adjacent to the first edge, a third edge opposite from the first edge and adjacent to the second edge, and a fourth edge adjacent to the third edge and the first edge and opposite from the second edge; the first connector can be disposed at the first edge of the substrate; the second connector can be disposed at the second edge of the substrate; the first conductive line can extend from the first patch antenna towards the first edge of the substrate; and the second conductive line can extend from the second patch antenna towards the second edge of the substrate. The first conductive line can extend such that it is parallel (or substantially parallel) to the second edge of the substrate and the fourth edge of the substrate, and the second conductive line can extend such that it is parallel (or substantially parallel) to the first edge of the substrate and the third edge of the substrate. The multi-band antenna can operate in a first band of operation when the first connector is connected to the external power source and the second connector is connected to the load, and the multi-band antenna can operate in a second band of operation when the first connector is connected to the load and the second connector is connected to the external power source. The multi-band antenna can comprise one or more unit cells capable of operating (and/or configured to operate) independently of each other, and each unit cell can comprise exactly two patch antennas, exactly three patch antennas, exactly four patch antennas, no more than three patch antennas, or no more than four patch antennas.
In another embodiment, a multi-band antenna can comprise: a substrate; a first patch antenna disposed on an upper surface of the substrate; a second patch antenna disposed on the upper surface of the substrate and physically separated from the first patch antenna by a first gap; a third patch antenna disposed on the upper surface of the substrate and physically separated from the second patch antenna by a second gap; a fourth patch antenna disposed on the upper surface of the substrate and physically separated from the third patch antenna by a third gap and physically separated from the first patch antenna by a fourth gap; a first connector for connecting to an external power source or a load; a second connector for connecting to the external power source or the load; a third connector for connecting to the external power source or the load; a fourth connector for connecting to the external power source or the load; a first conductive line disposed on the upper surface of the substrate, the first conductive line being in direct physical contact with the first patch antenna and the first connector, and the first conductive line electrically connecting the first patch antenna and the first connector; a second conductive line disposed on the upper surface of the substrate, the second conductive line being in direct physical contact with the second patch antenna and the second connector, and the second conductive line electrically connecting the second patch antenna and the second connector; a third conductive line disposed on the upper surface of the substrate, the third conductive line being in direct physical contact with the third patch antenna and the third connector, and the third conductive line electrically connecting the third patch antenna and the third connector; and a fourth conductive line disposed on the upper surface of the substrate, the fourth conductive line being in direct physical contact with the fourth patch antenna and the fourth connector, and the fourth conductive line electrically connecting the fourth patch antenna and the fourth connector. The first patch antenna, the second patch antenna, the third patch antenna, the fourth patch antenna, the first conductive line, the second conductive line, the third conductive line, the fourth conductive line, the first connector, the second connector, the third connector, and/or the fourth connector can be made of the same material (e.g., a conductive metal such as copper, gold, aluminum, silver, platinum, palladium, or a combination thereof). A cross-section of the first patch antenna (taken in a first plane parallel to the upper surface of the substrate) can have a rectangular shape, a cross-section of the second patch antenna (taken in the first plane) can have a rectangular shape, a cross-section of the third patch antenna (taken in the first plane) can have a rectangular shape, and/or a cross-section of the fourth patch antenna (taken in the first plane) can have a rectangular shape. The first patch antenna can comprise four sides including a first side facing the second patch antenna and being closest to the second patch antenna out of the four sides of the first patch antenna, and a second side facing the fourth patch antenna and being closest to the fourth patch antenna out of the four sides of the first patch antenna; the second patch antenna can comprise four sides including a third side facing the first patch antenna and being closest to the first patch antenna out of the four sides of the second patch antenna, and a fourth side facing the third patch antenna and being closest to the third patch antenna out of the four sides of the second patch antenna; the third patch antenna can comprise four sides including a fifth side facing the second patch antenna and being closest to the second patch antenna out of the four sides of the third patch antenna, and a sixth side facing the fourth patch antenna and being closest to the fourth patch antenna out of the four sides of the third patch antenna; and the fourth patch antenna can comprise four sides including a seventh side facing the third patch antenna and being closest to the third patch antenna out of the four sides of the fourth patch antenna, and an eight side facing the first patch antenna and being closest to the first patch antenna out of the four sides of the fourth patch antenna. A length of the first side of the first patch antenna can be equal to a length of the third side of the second patch antenna, a length of the fourth side of the second patch antenna can be equal to a length of the fifth side of the third patch antenna, a length of the sixth side of the third patch antenna can be equal to a length of the seventh side of the fourth patch antenna, and/or a length of the eighth side of the fourth patch antenna can be equal to a length of the second side of the first patch antenna. The first gap can be a smallest distance between the first patch antenna and the second patch antenna, measured in a first direction parallel to the upper surface of the substrate; the second gap can be a smallest distance between the second patch antenna and the third patch antenna, measured in a second direction parallel to the upper surface of the substrate; the third gap can be a smallest distance between the third patch antenna and the fourth patch antenna, measured in the first direction; and the fourth gap can be a smallest distance between the fourth patch antenna and the first patch antenna, measured in the second direction. A length of the first patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the first gap; a length of the second patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the first gap; a length of the second patch antenna, measured in the second direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the second gap; a length of the third patch antenna, measured in the second direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the second gap; a length of the third patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the third gap; a length of the fourth patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the third gap; a length of the fourth patch antenna, measured in the second direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the fourth gap; and/or a length of the first patch antenna, measured in the first direction, can be larger (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times larger) than the fourth gap. The length of the first patch antenna, measured in the first direction, can be larger (e.g., at least 1.1, 1.15, 1.2, 1.25, 1.3, 1.333, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.75, 1.8, 1.9, 2 or more times larger) than the length of the second patch antenna, measured in the first direction; the length of the fourth patch antenna, measured in the first direction, can be larger (e.g., at least 1.1, 1.15, 1.2, 1.25, 1.3, 1.333, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.75, 1.8, 1.9, 2 or more times larger) than the length of the third patch antenna, measured in the first direction; the length of the first patch antenna, measured in the first direction, can be the same (or about the same) as the length of the fourth patch antenna, measured in the first direction; the length of the second patch antenna, measured in the first direction, can be the same (or about the same) as the length of the third patch antenna, measured in the first direction; the length of the first patch antenna, measured in the second direction, can be the same (or about the same) as the length of the second patch antenna, measured in the second direction; the length of the third patch antenna, measured in the second direction, can be the same (or about the same) as the length of the fourth patch antenna, measured in the second direction; the length of the first patch antenna, measured in the second direction, can be larger (e.g., at least 1.1, 1.15, 1.2, 1.25, 1.3, 1.333, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.75, 1.8, 1.9, 2 or more times larger) than the length of the fourth patch antenna, measured in the second direction; and/or the length of the second patch antenna, measured in the second direction, can be larger (e.g., at least 1.1, 1.15, 1.2, 1.25, 1.3, 1.333, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.75, 1.8, 1.9, 2 or more times larger) than the length of the third patch antenna, measured in the second direction. The substrate can comprise a first edge, a second edge adjacent to the first edge, a third edge opposite from the first edge and adjacent to the second edge, and a fourth edge adjacent to the third edge and the first edge and opposite from the second edge; the first connector, the second connector, the third connector, and the fourth connector can be disposed at the first edge, the second edge, the third edge, and the fourth edge, respectively, of the substrate; the first conductive line can extend from the first patch antenna towards the first edge of the substrate; the second conductive line can extend from the second patch antenna towards the second edge of the substrate; the third conductive line can extend from the third patch antenna towards the third edge of the substrate; and the fourth conductive line can extend from the fourth patch antenna towards the fourth edge of the substrate. The first conductive line can extend such that it is parallel (or substantially parallel) to the second edge of the substrate and the fourth edge of the substrate; the second conductive line can extend such that it is parallel (or substantially parallel) to the first edge of the substrate and the third edge of the substrate; the third conductive line can extend such that it is parallel (or substantially parallel) to the second edge of the substrate and the fourth edge of the substrate; and the fourth conductive line can extend such that it is parallel (or substantially parallel) to the first edge of the substrate and the third edge of the substrate. The multi-band antenna can operate in a first band of operation when the second connector is connected to the load and the first connector is connected to the external power source; the multi-band antenna can operate in a second band of operation when the first connector is connected to the load and the second connector is connected to the external power source; the multi-band antenna can operate in a third band of operation when the second connector is connected to the load and the third connector is connected to the external power source; and the multi-band antenna can operate in a fourth band of operation when the third connector is connected to the load and the fourth connector is connected to the external power source. The multi-band antenna can comprise one or more unit cells capable of operating (and/or configured to operate) independently of each other, and each unit cell can comprise exactly four patch antennas.
In another embodiment, a method of fabricating a multi-band antenna can comprise: disposing a patch antenna material on a substrate; and etching a gap in the patch antenna material to give a first patch antenna and a second patch antenna with the gap physically separating the first patch antenna from the second patch antenna. The method can further comprise forming a first conductive line, a second conductive line, a first connector, and/or a second connector having the features disclosed herein. The multi-band antenna can have any of the features disclosed herein.
In another embodiment, a method of fabricating a multi-band antenna can comprise: disposing a patch antenna material on a substrate; etching a first gap, a second gap, a third gap, and a fourth gap in the patch antenna material to give a first patch antenna, a second patch antenna, a third patch antenna, and a fourth patch antenna, with the first gap physically separating the first patch antenna from the second patch antenna, the second gap physically separating the second patch antenna from the third patch antenna, the third gap physically separating the third patch antenna from the fourth patch antenna, and the fourth gap physically separating the fourth patch antenna from the first patch antenna. The method can further comprise forming a first conductive line, a second conductive line, a third conductive line, a fourth conductive line, a first connector, a second connector, a third connector, and/or a fourth connector having the features disclosed herein. The multi-band antenna can have any of the features disclosed herein.
Embodiments of the subject invention provide novel and advantageous multi-band antennas (e.g., microstrip patch antennas), as well as methods of fabricating the same and methods of using the same. A decoupling technique can be used to design and fabricate multi-mode, multi-band, electrically compact, microstrip patch antennas (e.g., rectangular microstrip patch antennas). Strategically etched slots can be provided between the tightly coupled microstrip patch antennas, and the appropriate mode excitation of the corresponding patch antennas can be used. The antennas have high isolation between the frequency bands of operation. Multi-band operation can be achieved by exciting a different mode on each contiguous portion of the patch antenna. The antennas can be multi-mode, multi-band patch antennas that are electrically compact, low-profile, and simple to design and fabricate as compared to related approaches that use complex, large, and/or absorptive decoupling structures.
The design approach of embodiments of the subject invention uses the coupling properties of slots in order to support the development of simpler and lower cost multi-band antennas. Field equivalence theory and image theory can be used to qualitatively explain the design approach. Extended slots can be used and can cut conventional patches into pieces to achieve high isolation (e.g., on the order of 30 decibels (dB)) between the feeding ports of multi-band and multi-mode microstrip antennas. The effects of the positions and orientations of these slots in both dual- and quad-mode designs are examined. The design approach is simple, and it can be applied to any microstrip antenna design.
An elegant approach is presented for designing multi-band multi-mode rectangular microstrip antennas (MSAs) with high isolation between the bands. The coupling properties of a gap (an extended slot), which is introduced in a rectangular MSA operating in the TM010 and TM100 modes, can be qualitatively explained through field equivalence theory and image theory. Even though the slot appears “transparent” (i.e., strongly couples the two sections of the MSA) to the TM010 mode, it effectively decouples the two sections of the MSA in the TM100 mode. As a proof-of-concept, the design technique can be applied to a conventional patch to achieve dual-band operation with 39 dB of measured isolation between the bands. The design concept can then be extended to achieve a quad-band antenna design with 30 dB of measured isolation between all of its bands. Compared to related art designs, embodiments of the subject invention preserve the low-profile of microstrip antennas and provide a simple way to design and fabricate multi-band and multi-mode antennas. They are therefore very well suited for antennas for next generation communication systems.
The design of embodiments of the subject invention can use the coupling properties of slots in microstrip structures. Its physical behavior can be explained using perturbation theory, field equivalence theory, and image theory. For simplicity but without loss of generality, let us assume the case of a rectangular patch antenna with length Px, width Py, and height h, as shown in
First, the effects of a slot in the design have to be understood, see
The next step is to examine how the slot affects the radiation characteristics of the design based on the assumption that the patch operates at the TM010 and TM100 modes. Using the Field Equivalence Principle, equivalent surface electric Js(bar)=n(hat)×H (bar), and magnetic Ms(bar)=−n(hat)×E(bar) currents can be found at the surface of the cavity. As explained in detail in (which is hereby incorporated by reference herein in its entirety), only the equivalent magnetic currents remain on the side periphery of the cavity as shown in
Let us now introduce a slot in the design that cuts the microstrip antenna in two sections, S1 and S2, as shown in
The same approach can be followed to understand the behavior of the patch when section one, S1, of the patch, operates at the TM010 mode (
In summary, based on the above qualitative analysis, the following can be concluded when an electrically narrow slot is cut into a patch: (a) in the case of the TM100 mode, the two sections of the patch, S1 and S2, are highly isolated and patch S2 contributes negligible radiation; and (b) in the case of TM010 mode, the two sections of the patch, S1 and S2, are strongly coupled and behave as if they are electrically connected. These conclusions can be used to develop a methodology for designing dual-band and quad-band microstrip antennas that exhibit high isolation between their bands.
In an embodiment, a quad-band patch can be used as a multiple-in, multiple-out (MIMO) antenna (see
In some embodiments, a quad-band patch can operate in four bands of operation. Referring to the labeling shown in
In another embodiment, a method of using a multi-band antenna can comprise providing a multi-band antenna (e.g., a dual-band antenna or a quad-band antenna) as disclosed herein and connecting a load and an external power source to the multi-band antenna to operate the multi-band antenna in a mode of operation as desired.
The transitional term “comprising,” “comprises,” or “comprise” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. By contrast, the transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. The phrases “consisting” or “consists essentially of” indicate that the claim encompasses embodiments containing the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claim. Use of the term “comprising” contemplates other embodiments that “consist” or “consisting essentially of” the recited component(s).
When ranges are used herein, such as for dose ranges, combinations and subcombinations of ranges (e.g., subranges within the disclosed range), specific embodiments therein are intended to be explicitly included. When the term “about” is used herein, in conjunction with a numerical value, it is understood that the value can be in a range of 95% of the value to 105% of the value, i.e. the value can be +/−5% of the stated value. For example, “about 1 kg” means from 0.95 kg to 1.05 kg.
A greater understanding of the embodiments of the subject invention and of their many advantages may be had from the following examples, given by way of illustration. The following examples are illustrative of some of the methods, applications, embodiments, and variants of the present invention. They are, of course, not to be considered as limiting the invention. Numerous changes and modifications can be made with respect to the invention.
The decoupling technique of embodiments of the subject invention was applied to a dual-band conventional MSA (CMSA) as shown in
ANSYS HFSS was used to simulate antenna performance and calculate the surface electric, Jsurf(bar), and equivalent magnetic currents, Meq(bar). The operation of the CMSA is described as follows. As shown by
The decoupling technique is applied to decouple the two modes of operation (i.e., two bands) of this antenna. This is achieved by first extending the original length of the CMSA, Px, from 20 mm to 31.65 mm. Despite this extended length, we will continue to assume that the antenna operates in the TM010 and TM100 modes in the low- and high-bands, respectively. This extended length increases the radiating dimension in low-band operation (TM010 mode), which reduces the input impedance of the patch at its feeding port PL according to Equation (1). Further, it increases the non-radiating dimension in high-band operation (TM100 mode), which based on fr≅c/(2P{circumflex over (x)}√{square root over (εr)}), reduces the resonant frequency of the patch.
All variables of Equation (1) are defined in [30] (which is hereby incorporated by reference herein in its entirety). Based on the conclusions summarized herein, a y-oriented slot introduced into the lengthened MSA appears “transparent” in low-band operation (compare
In order to exemplify the decoupling effect of the introduced slot in high-band operation, the equivalent PMC boundary is represented as a solid ground plane (
In summary, by extending one dimension of a dual-band CMSA and introducing a slot perpendicular to the extended dimension, both its low- and high-band resonant frequencies can be preserved. The simulated performances of the JFMSA and CMSA designs are compared in Table 1 in both the low-band (LB) and high-band (HB) operation in terms of: (a) 10 dB impedance bandwidth (BW); (b) minimum in-band isolation, Imin; (c) boresight gain (Go); (d) boresight cross polarization level (XPo); and (e) total efficiency (eo).
These results show that the JFMSA does not achieve any significant performance improvements over the CMSA. In fact, the JFMSA has a lower gain (by 1.3 dB) than the CMSA when operating in the low-band. This is attributed to the out-of-phase equivalent magnetic current densities on either side of the slot (see the blue dashed currents perpendicular to the slot in
In order to improve the low-band gain and isolation, the feed must be modified so it does not alter the performance of the method for decoupling modes. By centering the low-band port (PL) along the x edge of section S2, the equivalent magnetic currents on either side of the slot desirably become in-phase (see the blue dashed currents perpendicular to the slot in
Table 1 indicates that the SFMSA achieves 6.8 dB and 5.4 dB higher isolation than the CMSA when operating in the low- and high-bands, respectively. The simulated isolations of the CMSA, JFMSA, and SFMSA are plotted versus frequency and compared in
The elegance of the SFMSA design lies in its inherent simplicity. In designing an SFMSA from a CMSA, two additional design parameters must be determined, namely, the extended dimension of the MSA, Le, and the width of the introduced slot, Wg. Consider the SFMSA design with dimensions given in
Because the extended length (Le) does not affect the non-radiating length of the low-band TM010 mode, the low-band resonance is unaffected by the variation of Le, which is presented in
Also, the variation of the SFMSA's minimum in-band isolation versus the slot width, Wg, is presented in
Based on the above results, it is clear that large extended lengths and slot widths do not provide improved isolation. Therefore, the antenna's dimension needs to only slightly increase to achieve a significantly higher isolation between the two modes of operation.
For validation the SFMSA shown in
It is important to emphasize that improved isolation is typically achieved using enhanced feeding techniques or complex decoupling structures which are usually difficult to design and/or fabricate. Moreover, such structures typically increase the profile of the antenna or degrade its efficiency by absorb-ng power ([21]-[25]). Alternatively, in embodiments of the subject invention, the electromagnetic properties of a single slot are utilized and the current distributions of the desired modes are taken advantage of to provide high isolation and enhance the overall performance of the antenna. A comparison of the measured performance of the SFMSA to that of related art antennas is provided in Table 2. It is clear that the proposed design for decoupling modes achieves the highest isolation with gain, bandwidth, and cross polarization comparable to that of related art antennas.
Two SFMSAs (
The coupling properties of each slot, G1 and G2, are understood following the analysis given herein. When the antenna operates in the TM010 mode (see also
In summary, the resonant frequency of each patch is independently determined by its corresponding non-radiating dimension even in the presence of the other patches. However, the input impedance of each patch at its resonance is influenced only by the adjacent patch, which is separated by a “transparent” PMC plane. The design approach presented here can be used to design a quad-band antenna for any four frequency bands and provide high isolation between the bands. Notably, harmonic frequencies should be avoided in the multi-band designs as they can significantly decrease the isolation between neighboring bands. This guideline does not create a problem as communication systems typically avoid using the first harmonics of their bands.
The quad-band antenna was fabricated using an LPKF S103 milling machine. The fabricated antenna is shown in
The measured performance of this quad-band antenna is tabulated in Table 3. These results show that the quad-band antenna achieves high isolation between all the bands of operation (greater than 30 dB), which is accomplished using our proposed method for decoupling modes. Further, all bands achieve boresight gains greater than 4.7 dB and boresight cross polarization levels greater than 13.8 dB. A comparison between the measured performance parameters of the quad-band antenna and related art antennas is provided in Table 4. It is clear that the proposed decoupling technique provides the highest isolation between all bands of operation. Even though the design proposed in [35] achieved improved boresight cross polarization levels and radiation efficiency, these come at the cost of increased design complexity.
An elegant method was presented for designing multi-band and multi-mode microstrip antennas with high isolation between their bands. Specifically, the method introduces gaps (extended slots) in multi-band patch antennas to highly isolate the bands. The operation mechanism of this design approach was qualitatively explained using field equivalence theory and image theory. The method was verified by presenting two designs, which were simulated, fabricated, and measured (Examples 1 and 2); namely, a dual-band and a quad-band MSA that achieved measured isolation greater than 39 dB and 30 dB, respectively. The proposed method preserves the low profile of microstrip antennas, and provides a simple way to design multi-band and multi-mode antennas, which are suitable for next-generation communication systems.
A quad-band multiple-in, multiple-out (MIMO) microstrip patch antenna was proposed and comprises four rectangular patches operating at their dominant mode with edge-to-edge spacing of 0.0025λo. The four patches operated at 750 megahertz (MHz), 1.35 GHz, 1.42 GHZ, and 2.07 GHz, respectively. It was shown that by appropriately positioning the patches in relation to each other, an isolation greater than 10 dB is achieved. The antenna is low profile, compact, simple to design and fabricate, and it is well suited for MIMO base station applications.
Four MSAs operating at 750 MHZ, 1.35 GHz, 1.43 GHZ, and 2.07 GHz, respectively, were designed. Consider a rectangular patch MSA operating at its first two dominant modes. When a slot is cut parallel to the non-radiating edge, thereby creating a gap in the radiating edge, resonance is unaffected, as shown at a frequency f1 in
The reflection coefficients of all the ports are shown in
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.
All patents, patent applications, provisional applications, and publications referred to or cited herein (including those in the “References” section) are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.
The application claims the benefit of U.S. Provisional Application Ser. No. 63/218,743, filed Jul. 6, 2021, which is hereby incorporated by reference herein in its entirety, including any figures, tables, and drawings.
This invention was made with government support under FA9550-18-1-0191 awarded by Air Force Office of Scientific Research (AFOSR). The government has certain rights in the invention.
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| 11223141 | Liu | Jan 2022 | B2 |
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| Number | Date | Country | |
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| 20240213682 A1 | Jun 2024 | US |
| Number | Date | Country | |
|---|---|---|---|
| 63218743 | Jul 2021 | US |
