Patent Grant
8604983
As wireless device functionality and complexity increase, and as the size of such devices decreases, the area available to incorporate features and components is reduced. Therefore, optimal use of the available footprint provides a compact, densely functioned device. The use of Composite Right/Left Hand (CRLH) structures allows the antenna structure to be positioned on available substrate space. As the CRLH configuration may be done after design of other components, the designer may prioritize placement of functional components and utilize remaining space for CRLH structures. To this end, a variety of techniques and configurations may be used to design such CRLH based designs.
A metamaterial structure, also referred to as MTM structure, MTM-based structure, MTM-inspired structure, or MTM-type structure, may be a combination or mixture of a Left Hand (LH) MTM structure and a Right Hand (RH) structure; these combinations are referred to as Composite Right and Left Hand (CRLH) metamaterials. A CRLH metamaterial behaves like an LH metamaterial under certain conditions, such as for operation at low frequencies; the same CRLH metamaterial may behave like an RH material under other conditions, such as operation at high frequencies.
Implementations and properties of various CRLH MTMs are described in, for example, Caloz and Itoh, “Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications,” John Wiley & Sons (2006). CRLH MTMs and their applications in antennas are described by Tatsuo Itoh in “Invited paper: Prospects for Metamaterials,” Electronics Letters, Vol. 40, No. 16 (August, 2004).
CRLH MTMs may be structured and engineered to exhibit electromagnetic properties tailored to specific applications. Additionally, CRLH MTMs may be used in applications where other materials may be impractical, infeasible, or unavailable to satisfy the requirements of the application. In addition, CRLH MTMs may be used to develop new applications and to construct new devices that may not be possible with RH materials and configurations.
As used in this application, MTM and CRLH MTM structures and components are based on a technology called “Metamaterial” which applies the concept of Right-handed and Left-handed (LH) structures.
As used herein, the term “Metamaterial,” “MTM,” “CRLH,” and “CRLH MTM” refer to technology and technical means, methods, devices, inventions and engineering works which allow compact devices composed of conductive and dielectric parts and are used to receive and transmit electromagnetic waves and behave as unique structures which are much smaller than the free space wavelength of the propagating electromagnetic waves. Using MTM technology, antennas and RF components may be made very compactly in comparison to competing methods and may be very closely spaced to each other or to other nearby components while at the same time minimizing undesirable interference and electromagnetic coupling. Such antennas and RF components further exhibit useful and unique electromagnetic behavior that results from one or more of the following structures to design, integrate, and optimize antennas and RF components inside wireless communications devices.
Composite Right Left Handed (CRLH) structures exhibit simultaneous negative permittivity (∈) and permeability (μ) within certain frequency bands and simultaneous positive ∈ and μ within other frequency bands.
Transmission-Line (TL) based CRLH structures enable TL propagation and exhibit simultaneous negative permittivity (∈) and permeability (μ) within certain operating frequency bands and simultaneous positive ∈ and μ within other operating frequency bands
TL-based Left-Handed (TL-LH) structures enable TL propagation and exhibit simultaneous negative ∈ and μ within certain frequency bands and simultaneous positive ∈ and μ within extremely high-frequency non operating bands.
Combination of the above may be designed and built incorporating conventional RF design structures. Antennas, RF components and other devices may be referred to as “MTM antennas,” “MTM components,” and so forth, when they are designed to behave as an MTM structure. MTM components may be easily fabricated using conventional conductive and insulating materials and standard manufacturing technologies including but not limited to: printing, etching, and subtracting conductive layers on substrates such as FR4, ceramics, LTCC, MMICC, flexible films, plastic or even paper.
The propagation of electromagnetic waves in most materials obeys the right-hand rule for the (E,H,β) vector fields, which denotes the electrical field E, the magnetic field H, and the wave vector β (or propagation constant). In these materials, the phase velocity direction is the same as the direction of the signal energy propagation (group velocity) and the refractive index is a positive number. Such materials are referred to as Right/Handed (RH) materials. Most natural materials are RH materials, but artificial materials may also be RH materials.
A metamaterial (MTM) is an artificial structure which behaves differently from a natural RH material alone. Unlike RH materials, a metamaterial may exhibit a negative refractive index, wherein the phase velocity direction is opposite to the direction of the signal energy propagation where the relative directions of the (E,H,β) vector fields follow a left-hand rule. When a metamaterial is designed to have a structural average unit cell size ρ which is much smaller than the wavelength of the electromagnetic energy guided by the metamaterial, the metamaterial behaves like a homogeneous medium to the guided electromagnetic energy. Metamaterials that support only a negative index of refraction with permittivity ∈ and permeability μ being simultaneously negative are pure Left Handed (LH) metamaterials.
A metamaterial structure may be a combination or mixture of an LH metamaterial and an RH material; these combinations are referred to as Composite Right and Left Hand (CRLH) metamaterials. A CRLH metamaterial behaves like an LH metamaterial under certain conditions, such as for operation at low frequencies; the same CRLH metamaterial may behave like an RH material under other conditions, such as operation at high frequencies.
Implementations and properties of various CRLH MTMs are described in, for example, Caloz and Itoh, “Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications,” John Wiley & Sons (2006). CRLH MTMs and their applications in antennas are described by Tatsuo Itoh in “Invited paper: Prospects for Metamaterials,” Electronics Letters, Vol. 40, No. 16 (August, 2004).
CRLH MTMs may be structured and engineered to exhibit electromagnetic properties tailored to specific applications. Additionally, CRLH MTMs may be used in applications where other materials may be impractical, infeasible, or unavailable to satisfy the requirements of the application. In addition, CRLH MTMs may be used to develop new applications and to construct new devices that may not be possible with RH materials and configurations.
As used in this application, MTM and CRLH MTM structures and components are based on a technology called “Metamaterial” which applies the concept of RH and LH structures.
As used herein, the term “Metamaterial,” “MTM,” “CRLH,” and “CRLH MTM” refer to technology and technical means, methods, devices, inventions and engineering works which allow compact devices composed of conductive and dielectric parts and are used to receive and transmit electromagnetic waves and behave as unique structures which are much smaller than the free space wavelength of the propagating electromagnetic waves. Using MTM technology, antennas and RF components may be made very compactly in comparison to competing methods and may be very closely spaced to each other or to other nearby components while at the same time minimizing undesirable interference and electromagnetic coupling. Such antennas and RF components further exhibit useful and unique electromagnetic behavior that results from one or more of the following structures to design, integrate, and optimize antennas and RF components inside wireless communications devices.
CRLH structures exhibit simultaneous negative permittivity (∈) and permeability (μ) within certain frequency bands and simultaneous positive ∈ and μ within other frequency bands.
Transmission-Line (TL) based CRLH structures enable TL propagation and exhibit simultaneous negative permittivity (∈) and permeability (μ) within certain operating frequency bands and simultaneous positive ∈ and μ within other operating frequency bands
TL-based Left-Handed (TL-LH) structures enable TL propagation and exhibit simultaneous negative ∈ and μ within certain frequency bands and simultaneous positive ∈ and μ within extremely high-frequency non operating bands.
Combination of the above may be designed and built incorporating conventional RF design structures. Antennas, RF components and other devices may be referred to as “MTM antennas,” “MTM components,” and so forth, when they are designed to behave as an MTM structure. MTM components may be easily fabricated using conventional conductive and insulating materials and standard manufacturing technologies including but not limited to: printing, etching, and subtracting conductive layers on substrates such as FR4, ceramics, LTCC, MMICC, flexible films, plastic or even paper.
A CRLH MTM design may be used in a variety of applications, including wireless and telecommunication applications. The use of a CRLH MTM design for elements within a wireless application often reduces the physical size of those elements and improves the performance of these elements. In some embodiments, CRLH MTM structures are used for antenna structures and other RF components.
CRLH MTM structures may be used in wireless devices having a variety of features, components and elements. The space available for layout of the various components of the device may be challenging, as the components must be positioned to meet a specification. In some cases, it may be necessary to reroute connection lines or modify the shape of a component for incorporation into a device design. For example, a component may be distributed over a given surface, or otherwise shaped for implementation with other elements
In one example, a wireless device has a microphone positioned at an end of the device to optimize performance during use. The microphone is placed near the expected mouth position of the user. This is often at the bottom of the device. When an antenna or other component is designed for such a device, there is a requirement to avoid the component space designated for the microphone. To avoid the microphone, a CRLH structure may be implemented for an antenna, wherein a first part of the radiator is positioned on a first surface proximate the designated component space. A second part of the radiator is then positioned on an opposite surface of the substrate, and connected to the first part through a conducting via placed through the substrate. A third part of the radiator may then be positioned on the first surface proximate the microphone, and having connection to the second part of the radiator through a second conducting via through the substrate. In this way, the area of the radiator, or antenna structure, is sufficient for the specification, while maintaining the position of the microphone on the device.
Consider the structure of
The antenna 100 includes a plurality of unit cells which each act as a CRLH MTM structure. Each unit cell includes a cell patch 102 and a via 118, wherein the via 118 couples the cell patch 102 to a ground electrode 105. A launch pad 104 is configured proximate one of the cell patches 102, such that signals received on a feed line 106 are provided to the launch pad 104. The signal transmissions cause charge to accumulate on the launch pad 104. From the launch pad 104 electrical charge is induced onto the cell patch 102 due to electromagnetic coupling between the launch pad 104 and the cell patch 102. Similarly, for signals received at the antenna, charge accumulates on the cell patch 102, and the charge is induced onto the launch pad 104.
The substrate 110 may include multiple layers, such as two conductive layers separated by a dielectric layer. In such a configuration, elements of the antenna 100 may be printed or formed on a first layer using a conductive material, while other elements are printed or formed on a second layer. One of the first and second layers may include a ground electrode. The antenna element in the first layer may be electrically coupled to the antenna element in the second layer through connections, such as conductors or vias, extending through the substrate.
The cell patches 102 are the radiators of the antenna 100, which are configured along a first layer or surface of a substrate 110. For clarity the surface on which the cell patches 102 are formed is referred to as the top layer. The second surface is then referred to as the bottom layer.
Within the top surface, each cell patch 102 is separated from a next cell patch 102 by a coupling gap 108. Further, a coupling gap 108 spaces a terminal cell patch 102 and a corresponding launch pad 104. The launch pad 104 is coupled to a feed line 106 for providing signals to and receiving signals from the cell patch 102. Each cell patch 102 is coupled to the bottom surface of the substrate 110 by via 118. The bottom surface of the substrate 110 may be a ground plane or may include a truncated ground portion, such as a ground electrode patterned onto the bottom layer.
More specifically, this MTM antenna has a launch pad 404 with an added meander line 452 and a cell patch 408, all of which are on the top layer. The cell patch 408 is extended to an a cell patch extension 444 in the bottom layer by using one or more vias 448 to connect the cell patch 408 on the top and the cell patch extension 444 on the bottom. The launch pad 404 may also be extended to an a launch pad extension 436 in the bottom layer by using one or more vias 440 to connect the launch pad 404 on the top and the launch pad extension 436 on the bottom. The launch pad extension 436 on the bottom layer can also be referred to as an extended launch pad 436, and the cell patch extension 444 on the bottom layer can also be referred to as an extended cell patch 444. The respective vias are referred to as launch pad connecting vias 440 and cell connecting vias 448 in the figures. Such extensions can be made to comply with the space requirements while maintaining a certain performance level.
The antenna is fed by a grounded CPW feed 420 with a characteristic impedance of 50Ω. The feed line 416 connects the CPW feed 420 to the launch pad 404, which has the added meander line 452. The cell patch 408 has a polygonal shape, and capacitively coupled to the launch pad 404 through a coupling gap 428. The cell patch 408 is shorted to the top ground electrode 424 on the top layer through via line 412, wherein the route of via line 412 is optimized for matching. The substrate 432 can be made of a suitable dielectric material, e.g., an FR4 material.
Table 1 provides a summary of the elements of the semi single-layer penta-band MTM antenna structure in this example. Other configurations, layouts and layering may be used to implement CRLH structures.
The lower cell patch extension 842 is formed on the opposite layer or side of the substrate 832 and runs underneath, and approximately parallel to, the component area 850. The design then continues to optimize the space available, by providing via(s) 845 to connect the cell patch lower extension 844 to the cell patch upper extension 847. In this way, the effective length of the cell patch is the sum of the areas of the cell patch 846, the cell patch lower extension 842 and the cell patch upper extension 847. The layout and configuration of the antenna portions to avoid the component area 850 is referred to as a double folded antenna, where folds occur at points 801 and 803. Each time a cell patch continues onto another layer, the cell patch is considered a folded cell patch.
As discussed herein, a CRLH design may be used in a variety of applications, including wireless and telecommunication applications. The use of a CRLH or MTM based design for elements within a wireless application often reduces the physical size of those elements and improves the performance of these elements. In some embodiments, CRLH structures are used for antenna structures and other RF components.
CRLH structures may be used in wireless devices having a variety of features, antenna structures and elements. The space available for layout of the various antenna structures of the device may be challenging, as the components must be positioned to meet certain layout constraints such as device enclosure size and dimensions. In some cases, it may be necessary to reroute connection lines or modify the shape of a component for incorporation into a device design. Rerouting connection lines and adapting the shape of the components do provide some relief and additional space savings necessary to meet these layout constraints. However, as the devices continue to get smaller, rerouting lines and adapting the shape may not be enough to meet smaller design requirements, especially on compact wireless devices that are formed on a single PCB or other substrate. Thus, alternative and novel designs and methods of producing antenna structures that can maximize the use of a limited area may be of increasing interest as the layout constraints continue to shrink.
CRLH structures provide several benefits for constructing a compact antenna while supporting a broad range of frequencies. Some of these structures are described in the U.S. patent application Ser. No. 12/270,410 entitled “Metamaterial Structures with Multilayer Metallization and Via,” filed on Nov. 13, 2008, the disclosure of which is incorporated herein by reference. Separation between certain parts of the CRLH antenna structure over multiple PCBs may be beneficial as to improve space limitations within the compact wireless device. The placement of the CRLH antenna structure over multiple PCBs may be configured in a variety of ways, such as elevating one or more PCBs over a main PCB, forming stacked layers of PCBs. In addition, this elevated design and techniques for implementing such design may be extended to include a combination of multiple CRLH antenna structures distributed over the main PCB substrate and the elevated PCB substrates, supporting multiple frequency bands.
The various CRLH structures may be configured within a single layer of a substrate, within multiple layers of a substrate, on multiple substrates configured proximate each other, by way of multiple elevated components, or a combination thereof. In some embodiments, the CRLH structures are used to build multiple elevated antenna elements.
Referring to
Beginning with the main substrate 1001 as shown in
The area consumed thus far by the conductive elements defining the feed line 1003, the rectangular stub 1008, the first and second cell patches 1005 and 1009, and the first via line 1013 may be insufficient to include additional conductive elements that support the CRLH antenna within the area defined by the main substrate 1001. To accommodate these additional conductive elements, additional elevated substrates 2001 and 3001 are formed within the boundaries 2000 and 3000, respectively, defined on the main substrate 1001. For example, to comply with the space requirements while maintaining a certain performance level, the first cell patch 1005 and the feed line 1003 may be extended to the elevated substrates 2001 and 3001.
Referring to
In
In this example, the performance of the CRLH antenna device is made possible by extending the cell patch and meander line within a confined area. The cell patch extension may help improve matching of the LH mode resonance, whereas the meander extension may improve matching of the monopole (RH) mode resonance.
Table 2 provides a summary of the elements of an MTM antenna structure according to such examples as illustrated in
Other CRLH antenna designs include a stack PCB configuration as shown in
While this specification contains many specifics, these should not be construed as limitations on the scope of an invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Only a few implementations are disclosed. However, it is understood that variations and enhancements may be made.
While this specification contains many specifics, these should not be construed as limitations on the scope of an invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Only a few implementations are disclosed. However, it is understood that variations and enhancements may be made.
This application claims the benefit of priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No. 61/302,121, entitled “DOUBLE FOLDED ANTENNA,” filed on Feb. 6, 2010, and to U.S. Provisional Patent Application Ser. No. 61/311,206, entitled “MULTI-ELEVATED AND DISTRIBUTED METAMATERIAL ANTENNA DEVICE,” filed on Mar. 5, 2010, both of which are incorporated herein by reference in their entireties.
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