US20200243978A1

US20200243978A1 - Systems and methods for virtual ground extension for monopole antenna with a finite ground plane using a wedge shape

Info

Publication number: US20200243978A1
Application number: US16/752,268
Authority: US
Inventors: Jørgen Bøjer; Mikkel Baumann-Jorgensen
Original assignee: Wispry Inc
Current assignee: Wispry Inc
Priority date: 2019-01-24
Filing date: 2020-01-24
Publication date: 2020-07-30
Also published as: US20200244327A1; WO2020154667A1; WO2020154695A1; WO2020154650A1; US11349217B2; US20200243958A1

Abstract

The present subject matter relates to positioning monopole antennas on a ground plane of a mobile device, the ground plane having a tapered edge near where the monopole is positioned. By placing the monopole near the tapered edge, the radiation pattern of the monopole is directed, at least partially, laterally towards the tapered edge. In some embodiments, a reflector is on the ground plane, where the monopole is between the reflector and the tapered edge. The reflector is configured to further direct radiation from the monopole towards the monopole antenna and tapered edge.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/796,390, filed Jan. 24, 2019, the entire disclosure of which is incorporated by reference herein. This application also relates to U.S. application Ser. No. ______ (to be assigned), entitled SPHERICAL COVERAGE ANTENNA SYSTEMS, DEVICES, AND METHODS and ______ (to be assigned), entitled METHOD FOR INTEGRATING ANTENNAS FABRICATED USING PLANAR PROCESSES commonly owned and filed on Jan. 24, 2020, both of which also claim priority to U.S. Provisional Patent Application Ser. No. 62/796,390, filed Jan. 24, 2019, the contents of all applications identified above which are incorporated by reference herein.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to mobile device ground planes. More particularly, the subject matter disclosed herein relates to mobile phone ground planes with monopole antennas.

BACKGROUND

In the design and performance of monopole and similar antennas for mobile devices the ground plane plays a significant role. Oftentimes, monopole antenna design is done with an assumption of an infinite ground plane or very large ground plane compared to the wavelength of wireless signals being sent to and from the wireless device.
In handheld wireless applications (e.g., mobile phones, tablets, etc.) the large or infinite ground plane assumption will not be true and the radiation pattern and performance will be strongly influenced by the shape and extent of the finite ground plane. In any direction where the ground plane extends more than a certain multiple of the wavelength of the transmitting and receiving signals, the radiation performance will approach the infinite ground plane assumption and in any direction where the ground plane extends less than a certain multiple of the wavelength the radiation performance will be scarified.
This is true for situations where the monopole antenna is placed near or at the edge of a finite ground plane and radiation performance will be strongly sacrificed in the direction of the edge.
For monopole antennas, that cannot be placed on a large extended ground plane, virtual ground plane techniques and solutions have been investigated and designed. This is true for monopole antennas like conical skirt antennas and wire virtual ground plane antennas, for example, see C.A. Balanis: Antenna Theory—Analysis and Design (ISBN 0-471-6039-1), the entire disclosure of which is expressly incorporated by reference herein.
Turning first to FIG. 1A, an example mobile phone antenna system 100 is provided that illustrates a ground plane 102 with a monopole antenna 104 positioned near the edge 106 of the ground plane 102. The mobile phone antenna system 100 depicted in FIG. 1A illustrates the typical, commercially available ground plane 102 shape. In this particular illustration, the edge 106 of the ground plane 102 is flat and un-tapered, or has an orthogonal cut (i.e., the angle formed between the top of the ground plane, in this view, and the side of the ground plane is approximately 90°).
This traditional design of mobile phone ground planes 102 generally produces very little radiation directed at the edge 106 of the ground plane 102, as illustrated by FIG. 1B. In FIG. 1B, the direction of propagation of the vast majority of the radiation is away from the edge 106. Although there is a small bit of radiation directed towards the edge 106, a large majority is directed away from the edge 106 and toward the rest of the ground plane 102. FIG. 10 illustrates the electric field (in dB) generated by the device described above in FIG. 1A and FIG. 1B.
Referring to FIG. 1D, in some instances, in order to better direct radiation towards the edge 106 a reflector 108 can be positioned behind or beside the monopole antenna 104. Depending on the properties of the reflector 108, its distance from the monopole antenna 104, the angle, and various other features of the reflector 108, the radiation propagated by the antenna can be reflected out towards the edge 106 of the ground plane 102. FIG. 1E illustrates this principle. These various designs demonstrate how current mobile devices operate with orthogonal cut ground planes.
FIG. 1F, FIG. 1G, and FIG. 1H illustrate various other designs for creating a virtual ground plane or creating virtual ground plane like effects using a conical skirt, a disk, and wire simulations. Each of these designs are configured to affect the radiation propagation from transmissions of the antennas. However, each of these designs and methods are unsuitable or impracticable for most mobile handset designs.

SUMMARY

The present disclosure describes a solution, for monopole antennas near an edge of a ground plane, that can be used to design the ground plane shape in such a manor that will make it possible to increase radiation towards the direction of the edge compared with other designs with the same distance from the monopole antenna to the edge of the ground plane.
In wireless terminals (mobile phones) the ground plane will have a finite extent and can often have a rectangular shape that follows the shape and the inside boundaries of the wireless terminal (mobile phone) cabinet. Oftentimes, a layer of a printed circuit board (PCB) is used as ground plane. In wireless terminals where milimeter wave (mmWave) communication is applied it can be desired to have monopole antennas or arrays of monopole antennas oriented perpendicular to the ground plane of the terminal so the ground plane can be used for radiation in the direction where the ground plane extends multiple wavelengths. The mmWave wavelength makes it possible to use the systems and devices of the present disclosure to shape the ground plane for mmWave wireless terminal applications.
In accordance with this disclosure, an antenna system for a mobile device is provided. In one aspect, the antenna system comprises a ground plane; and one or more monopole antennas near a first edge of the ground plane; wherein the one or more monopole antennas extends out from, and substantially orthogonal to, the ground plane; and wherein the first edge of the ground plane is tapered such that the first edge forms a wedge shape. In some embodiments, a radiation pattern of at least one of the one or more monopole antennas is directed substantially laterally towards the first edge.
In some embodiments, the antenna system further comprises at least one reflector on the ground plane; wherein the reflector has a shape that is configured to concentrate radiation fields onto the one or more monopole antennas. In some embodiments, the reflector has at least a partially cylindrical shape, a vertical wall shape, a parabolic shape, a hyperbolic shape, or a “V” shape having angles between and including about 30 and 175 degrees. In some embodiments, a reflection is created by having a first dielectric medium surrounding the one or more monopole antenna and a second dielectric medium such that fields incident to the one or more monopole antenna and not being picked up by the one or more monopole antenna will travel to an interface created where the first dielectric medium and the second dielectric medium meet, and the fields will be reflected, including partially reflected, towards the one or more monopole antenna.
Moreover, in some embodiments, one of the at least one reflector is positioned such that at least one monopole antenna of the one or more monopole antennas is positioned between the one reflector and the first edge of the ground plane. In some embodiments, the at least one reflector is configured to further direct radiating electromagnetic signals towards the first edge of the ground plane. In some embodiments, the one of the at least one reflector is positioned between and including about 0.1 and 0.7 wavelengths away from the at least one monopole antenna; and wherein a wavelength is equivalent to one wavelength of an operating or resonating frequency of the antenna system. In some embodiments, the ground plane extends less than about one wavelength to a second edge, opposite the first edge.
In some further embodiments, at least one of the one or more monopole antennas is positioned less than about 0.2 wavelengths away from a beginning of the edge of the ground plane that is tapered; wherein the beginning of the edge of the ground plane is a thickest portion of the taper; and wherein a wavelength is equivalent to one wavelength of an operating or resonating frequency of the antenna system.
In accordance with this disclosure, a method of controlling a direction of radiation of one or more monopole antennas is provided. In one aspect, the method comprises: positioning the one or more monopole antennas near a first edge of a ground plane; and reflecting radiation fields onto the one or more monopole antennas; wherein the first edge of the ground plane is tapered such that the first edge forms a wedge shape.
Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which:

FIG. 1A is a side view of an example mobile device antenna system according to some variations of mobile devices currently in the prior art;

FIG. 1B is a side view of the example mobile device antenna system from the prior art with a radiation pattern chart overlaid;

FIG. 1C is a side view of the example mobile device antenna system from the prior art with an electric field chart overlaid;

FIG. 1D is a side view of an example mobile device antenna system according to some variations of mobile devices currently in the prior art;

FIG. 1E is a side view of the example mobile device antenna system from the prior art with a radiation pattern chart overlaid;

FIG. 1F, FIG. 1G, and FIG. 1H are example monopole designs according to some devices in the prior art;

FIG. 2A is a side view of an example mobile device antenna system according to some embodiments of the present disclosure;

FIG. 2B is a side view of the example mobile device antenna system from the present disclosure with a radiation pattern chart overlaid;

FIG. 2C is a side view of the example mobile device antenna system from the present disclosure with an electric field chart overlaid;

FIG. 2D is a side view of the example mobile device antenna system from the present disclosure with an electric field chart overlaid;

FIG. 2E is a side view of another example mobile device antenna system according to some embodiments of the present disclosure;

FIG. 3A is a side view of an example mobile device antenna system according to some embodiments of the present disclosure;

FIG. 3B is a side view of the example mobile device antenna system from the present disclosure with a radiation pattern chart overlaid;

FIG. 3C and FIG. 3D are side views of the example mobile device antenna system from the present disclosure with electric field charts overlaid;

FIG. 3E, FIG. 3F, FIG. 3G, and FIG. 3H are perspective views of the example mobile device antenna system from the present disclosure depicting various shapes and implementations of the reflector or slot;

FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, FIG. 4E, FIG. 4F, FIG. 4G, and FIG. 4H are top views of various example placements and dimensions of mobile device antenna systems according to some embodiments of the present disclosure;

FIG. 5A is a close-up perspective view of an example mobile device antenna system detailing various dimensions thereof according to some embodiments of the present disclosure;

FIG. 5B and FIG. 5C are close-up side vides of the example mobile device antenna system detailing various dimensions thereof according to some embodiments of the present disclosure;

FIG. 6A is a perspective view of an example mobile device antenna system according to some embodiments of the present disclosure;

FIG. 6B is a front view of an example mobile device antenna system according to some embodiments of the present disclosure; and

FIG. 7A and FIG. 7B are perspective views of an example mobile device antenna system comprising multiple monopoles according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The present subject matter provides systems and methods for positioning monopole antennas near an edge of a ground plane, wherein the groundplane edge is designed and configured to increase radiation propogation of the antenna towards the direction of the edge compared with other designs with the same distance from the monopole antenna to the edge of the ground plane.
Referring to FIG. 2A, which illustrates a side view of an example mobile device antenna system 100 comprising a ground plane 102. A ground plane is a function that can come from conductors inherent in metal in the PCB, chassis or a shield or plated conductors on the PCB, chassis or shield or on some other structure fabricated for other purposes or for this specific purpose or combinations thereof. In some cases the ground plane 102 and chassis can be interchangeable. Therefore, hereinbelow, when reference is made to a ground plane 102 it could also be a chassis. In some embodiments, the ground plane 102 can be a solid conductor (i.e., such as copper or other suitable conductor) or a combination of a dielectric material (i.e. a PCB material, such as for example, FR-4) with copper (or other suitable conductor) foil on the ground surface. In some embodiments, the edge 106 can be plated or have a copper (or other suitable conductor) foil applied to it. In other words, the ground plane 102 can be comprised of a material that has an inherent conductive surface (i.e. a conductive material) or a material that has been given a conductive surface (i.e. like a conductive foil or other conductor applied to it). In order to achieve the desired antenna radiation directivity towards the edge 106 of the ground plane 102 of the mobile device antenna system 100, in some embodiments of the present disclosure, the edge 106 of the ground plane 102 comprises a wedge or tapered shape. The wedge shape or tapered shape of the edge 106 is configured to reflect the radiation emanating from the monopole 104 towards the direction of the edge 106.
In some embodiments, the monopole 104 is positioned on the ground plane 102 such that the length of the monopole 104 is approximately orthogonal (i.e. at a 90° angle) to the length of the ground plane 102. However, those having ordinary skill in the art will appreciate that the monopole 104 can be positioned such that the angle formed between the monopole 104 and the ground plane 102 is 90°+/−45°. For example and without limitation, in some embodiments, the angle formed between the monopole 104 and the ground plane 102 can be approximately 45°.
As illustrated in FIG. 2B, although a majority of the radiation pattern is directed away from the edge 106 and towards the rest of the ground plane 102, a significant portion of the radiation is directed toward the edge 106. The tapered edge 106 acts as a virtual ground plane where a full-length ground plane 102 cannot be implemented in the direction of the edge 106 because of the size limitations of the mobile device. The tapered edge 106 helps to generate such a radiation pattern because the incident field to the tapered edge 106 will be reflected and concentrated onto the quarter-wave monopole 104 onto the direct incident field arriving at the monopole 104.
Those having ordinary skill in the art will appreciate that, when comparing the radiation pattern of the non-tapered edge in FIG. 1B to the radiation pattern of the tapered edge in FIG. 2B, the radiation being reflected off the edge 106 of the tapered edge embodiment is much more significant than the embodiment where the edge is not tapered (like in FIG. 1B). This phenomenon (i.e. radiation pattern of the tapered edge in FIG. 2B) can be an ideal radiation pattern for mobile handsets, especially when the radiation or electromagnetic signals need to be directed toward or away from the edge or side of the mobile device. Those skilled in the art will appreciate that the reciprocity theorem is valid for the antennas and electromagnetic propagation and the receive or transmit scenario are interchangeable scenarios and any mention herein according to a receive or transmit scenario is used for explanatory and example purposes only and should not be construed as limiting the present subject matter in any way.
This particular design can be useful when the radiation produced by the monopole 104 would otherwise be interfered with or otherwise obstructed by some object such as, for example, a human hand holding the mobile device. The configurations described herein are also ideal for mobile handset designs that are restricted by other components that need to be included in the phone (i.e. such as a larger battery or other hardware to support certain features, etc.). Those having ordinary skill in the art will also appreciate that the radiation reflected by the device with the tapered edge reflects the radiation approximately orthogonally (i.e., about 90°) to the monopole 104. However, as illustrated in FIG. 1B, the radiation is slightly reflected at an angle of about 60° from the monopole 104. Additionally, the antenna gain towards the edge 106 is slightly higher (i.e., about 2 dB) for the tapered case than the non-tapered case (i.e., about 1 dB).
In the embodiment simulated in FIG. 2B, the operating frequency was 30 GHz and the free space/vacuum wavelength was 10 mm. The physical ground plane 102 used to simulate and generate the radiation plot was approximately 71 mm long from the left top edge to the beginning of the wedge (i.e. thickest part of the taper 106) and the bottom length of the ground plane 102 (i.e., the left edge of the board to the thinnest part of the taper 106 was 74.33 mm). Therefore, the taper length was 3.33 mm or about ⅓ wavelength. The thickness of the ground plane was also about 3.33 mm or about ⅓ wavelength. Furthermore, the monopole 104 was located about 1 mm (i.e., 0.1 wavelength) away from the beginning of the tapered edge (i.e. the thickest part of the tapered edge). The monopole height was about 0.25 wavelength or about 2.55 mm.
FIG. 2C and FIG. 2D illustrate the electric field generated by an example monopole 104 as described herein in dB and in volts per meter (V/m), respectively.
In some embodiments, the tapered edge 106 can be positioned on any edge of the ground plane 102. For example, and without limitation, assuming that the ground plane 102 is rectangular, the tapered edge 106 can be positioned at either of the short sides of the ground plane 102 or either of the long sides of the ground plane 102. Similarly, assuming the ground plane 102 is circular, the tapered edge 106 can be placed at any portion or section of the circumference of the circular ground plane 102. Those having ordinary skill in the art will appreciate that a ground plane 102 having any shape can have a tapered edge 106 at any position around the edge, perimeter, circumference, or other outer boundary of the shape of the ground plane 102. Additionally, as will be discussed further herein below, in some embodiments, the entire length of the edge or side of the ground plane 102 can have the wedge shape, or only a portion of the edge 106 can be tapered. FIG. 6A described hereinbelow details an example ground plane 102 where only a part of the edge is tapered, while the remaining portion of the edge has an orthogonal cut.
In some embodiments, as illustrated in FIG. 2A, the ground plane 102 on the opposite side of the monopole 104 as the edge 106 can be the remainder of a relatively large ground plane 102 extending various lengths from the monopole 104, depending on the design needs of the mobile device antenna system 100. These features and their respective dimensions will be described further herein. With that being said, in some embodiments, the area on the opposite side of the monopole 104 from the edge 106 can include other ground plane designs. For example and without limitation, the ground plane 102 on the opposite side of the monopole 104 from the tapered edge 106, can comprise various circuit components, glass, a plastic chassis or some other material that has a limited effect on the radiation performance of the monopole 104 in the direction away from the edge 106. In some further embodiments, there is no further extension of the ground plane 102 on the opposite side of the monopole 104 as the edge 106.
Additionally, although the tapered edge 106 in previous illustrations ended in a point, or narrow taper, in some embodiments, as illustrated in FIG. 2E, the tapered edge 106 can terminate and have a flat edge. In other words, in some embodiments, the tapered edge 106 does not end in a point, but tapers some and then terminates with a flat edge instead of the point. Another way of describing the edge 106 in this embodiment is that if the edge 106 were cut off at its thickest point (i.e. where the taper begins), a cross-section of the cut-off edge 106 would be in the shape of a right trapezoid. This particular embodiment has a similar effect on the radiation performance but does not include a harsh taper.
Referring to FIG. 3A, in some embodiments, a reflector 108 having a conducting shape can be positioned on the ground plane 102 on the opposite side of the monopole 104 as the tapered edge 106. In some embodiments, the reflector 108 is configured to reflect radiation emanating from the monopole 104 towards the tapered edge 106 and away from the rest of the ground plane 102. In some embodiments, the reflector 108 is made of a suitable material that can at least partially reflect monopole 104 radiation towards the tapered edge 106. For example and without limitation, the reflector 108 can comprise one or more of the following: copper, gold, silver, aluminum conductive paint or foil put onto a dielectric housing, or with plated vias through the dielectric housing. The outer surface of the reflector 108 can be plated with a conductive material, such as any of those discussed above, so long as the material passivates the surface and conducts well at the frequencies of operation of the monopole 104. Those having ordinary skill in the art will appreciate that the reflector 108 can be fabricated using edge plating or other planar PCB processes.
In some embodiments, the reflector 108 is configured such that it reflects most of the radiation emanating from the monopole 104 towards the tapered edge. In other words, in some embodiments, the reflector 108 is shaped, positioned, and made out of appropriate materials such that it reflects most of the radiation towards the tapered edge. These features (size and positioning of the reflector 108) are described in more detail herein. In other embodiments, the reflector 108 is configured such that it only reflects a small portion (i.e., less than half) of the radiation emanating from the monopole 104 towards the rest of the ground plane 102, reflecting the radiation back towards the tapered edge 106.
FIG. 3B and FIG. 3C illustrate the radiation pattern of the mobile device antenna system 100 when a reflector 108 is included in the design. When comparing the radiation lobe of FIG. 3B to the radiation lobe of FIG. 1E (i.e., with no tapered edge), the radiation lobe of FIG. 3B is directed closer to an orthogonal directivity (i.e., closer to about 90° with respect to the monopole 104), whereas the radiation lobe of FIG. 1E is directed closer to about 60°. Those having ordinary skill in the art will appreciate that, although both designs cause the radiation emanating from the monopole 104 to be directed generally toward the edge 106 of the ground plane 102, however, the tapered edge design of the present disclosure causes a more pronounced orthogonal reflection of the radiation. Additionally, the antenna gain of the device with the reflector 108 and the tapered edge is about 8 dB, which is similar to the antenna gain for just the reflector (i.e. no tapered edge), which indicates that the tapered edge has more impact on directivity of the radiation fields and less impact on the gain of the monopole 104.
In the embodiment simulated in FIG. 3B, the operating frequency was 30 GHz and the free space/vacuum wavelength was 10 mm. The physical ground plane 102 used to simulate and generate the radiation plot was approximately 71 mm long from the left top edge to the beginning of the wedge (i.e. thickest part of the taper 106) and the bottom length of the ground plane 102 (i.e., the left edge of the board to the thinnest part of the taper 106 was 74.33 mm). Therefore, the taper length was 3.33 mm or about ⅓ wavelength. The thickness of the ground plane was also about 3.33 mm or about ⅓ wavelength. Furthermore, the monopole 104 was located about 1 mm (i.e., 0.1 wavelength) away from the beginning of the tapered edge (i.e. the thickest part of the tapered edge) and the reflector 108 was located about 1.5 mm away from the monopole 104. The monopole height was about 0.25 wavelength or about 2.55 mm and the reflector 108 was about 1 mm thick.
FIG. 3C illustrates the electric field of the mobile device antenna system 100 in dB and FIG. 3D illustrates the electric field of the mobile device antenna system 100 in volts per meter (V/m).
In some embodiments, the reflector 108 has a shape that is configured or selected to concentrate the radiation fields onto the one or more monopole antennas 104. FIG. 3E, FIG. 3F, and FIG. 3G each illustrate different shapes or implementations of the reflector 108. For example and without limitation, in some embodiments, as shown in FIG. 3E, the reflector 108 can have a rod shape (i.e., any rod shape with a circular, rectangular, or any other suitable polygonal cross section) or at least partially cylindrical shape. In such embodiments, the reflector 108 is only slightly larger (i.e. taller and wider) than the monopole 104. However, as illustrated in FIG. 3F, in some embodiments, for example and without limitation, the reflector 108 can resemble a vertical wall or wide reflector (i.e., wider than the rod shape in FIG. 3E). In such embodiments, the vertical wall shaped reflector 108 can have a width greater than the width of the monopole 104 and greater than the width of the reflector as a rod shape, but the reflective benefit of the wall starts to diminish as the width of the wall gets greater than about 1 wavelength. Reflectivity of the reflector will not increase much as it gets wider than 1 wavelength. As a hypothetical example, given a radio wave at a frequency of about 26 GHz and the space surrounding the edge 106 having a relative permittivity of ε_r=3, the wavelength (λ) of the signal would be about 6.665 mm.
λ=v/f
v=velocity of the radio signal, f=frequency
v=c/√{square root over (ε)}
c=speed of light through vacuum (i.e. 2.998×10⁸m/s); and ε is the relative permittivity of the medium
v=(2.998×10⁸)/√{square root over (3)}=1.7308×10⁸ m/s
λ=(1.7308×10⁸ m/s)/26×10⁹ Hz
A=6.65 mm
Throughout the remainder of the description herein, the hypothetical described above will be used to demonstrate the wavelength values of the dimensions of some of the devices described herein.
Additionally, in some embodiments, as shown in FIG. 3G, the reflector 108 can be implemented using a slot 112. In some embodiments, the slot 112 can be a horizontal rectangular hole formed (i.e. drilled, etched, etc.) in the ground plane 102. In some embodiments, the slot 112 can be plated by any suitable plating process known to those having ordinary skill in the art. In such an embodiment, where the slot 112 is included, instead of the rod or wall shaped reflector 108, the slot 112 operates in a very similar fashion as the other shapes. The slot 112 is configured to reflect radiation back out towards the tapered edge 106. Moreover, in some embodiments, the reflector 108 can be a “V” shape having angles between and including about 30 and 175 degrees, a parabolic shape or hyperbolic shape as well. In some embodiments, the reflector 108 can be a dielectric reflector, where the reflector 108 is created by an interface where a first medium (i.e., for example a dielectric medium) having a relative permittivity of ε₁and a second medium (i.e., for example a dielectric medium) with a relative permittivity of ε₂meet. In such a scenario, ε₁is greater than or less than ε₂. FIG. 3H illustrates such an embodiment. In FIG. 3H, the monopole 104 is enclosed in a first dielectric medium 144 that has a relative permittivity of ε₁that is surrounded by a second dielectric medium 146 that has a relative permittivity of ε₂. This principle is very similar to a DRA (Dielectric Resonator Antenna).
Referring to FIG. 4A, FIG. 4B, and FIG. 4C, which each illustrate a top view of a mobile device antenna system 100 comprising a rectangular ground plane 102 having a reflector 108 positioned near a monopole 104 in various positions near the edge 106 of the ground plane 102. For example, in some embodiments, as illustrated in FIG. 4A, the monopole 104 can be positioned approximately in the middle of the ground plane 102 at the edge 106. In embodiments where the reflector 108 is included, the reflector 108 can likewise be positioned approximately in the middle of the ground plane 102 at the edge 106, as shown in FIG. 4A. As illustrated in FIG. 4B and FIG. 4C, the monopole 104 and the reflector 108 (if it is included) can be positioned to the left or to the right of the middle of the ground plane 102 near the edge 106. However, the above-mentioned illustrations should not be construed as limiting the placement of the monopole 104 and/or the reflector 108. Those having ordinary skill in the art will appreciate that the monopole 104 and the reflector 108 (if it is included) can be positioned at any suitable location along any side or edge of the ground plane 102.
The particular design requirements of the mobile device antenna system 100 will dictate the particular positioning of the monopole 104 and reflector 108. In general, however, the position of the monopole 104 and the reflector 108 (if it is included) can be positioned such that the radiation emanating from the monopole 104 is not obstructed by a user's hand or by another object envisioned by the mobile handset designer. Additionally, those having ordinary skill in the art will appreciate that in the direction towards the tapered edge 106, the monopole antenna 104 can operate under a virtual ground plane assumption mode. In the direction away from the tapered edge 106 (i.e., in the direction towards the rest of the ground plane 102) the monopole 104 can operate under a large ground plane assumption mode. Thus, in some embodiments, the wedge shape along the edge 106 of the ground plane 102, allows for a smooth transition between the two ground plane assumption modes.
Referring to FIG. 4D, the following description of certain example embodiments utilizes the frequency and permittivity values of the hypothetical described above (i.e., given a radio wave at a frequency of about 26 GHz and the space surrounding the edge 106 having a relative permittivity of ε_r=3). FIG. 4D illustrates a top view of an example mobile device antenna system 100 as described herein. Example dimensions of the various components are described herein for illustrative purposes only and should not be construed as limiting the dimensions or design of the mobile device antenna system 100. In some embodiments, a first length 120 of the ground plane 102 or the chassis, measured from the monopole 104 to the other end (i.e., non-tapered end) of the ground plane 102 can range from about the size of the handheld device to less than a quarter wavelength. This is so because the reflector 108 acts to reflect the radiation and the ground plane 102 does not have much of an impact on the radiation being reflected. For example and without limitation, in some embodiments, the first length 120 can be three wavelengths or it can be less than a quarter wavelength.
Thus, the first length 120 is dependent upon whether the reflector 108 or slot 112 is included. Additionally, a second length 122, measured as the distance between the reflector 108 and the monopole 104, can be an odd number of quarter wavelengths. In other words, the reflector 108 in this visualization can be ¼, ¾, or 5/4, etc. wavelengths away from the monopole 104, where the numerator is an odd number and the denominator is 4 (i.e. for quarter wavelength). In other words, in some embodiments, the second length 122 can be between, and including, about 0.1 and 1.75 wavelengths. For example and without limitation, the second length 122 can be approximately 1.66 mm at about 0.25 wavelengths (i.e., with a wavelength of about 6.65 mm). In some embodiments, the second length 122 can be approximately equal to about an eighth of a wavelength (i.e., ⅛*λ, where λ is the wavelength of the operating or resonating frequency of the monopole 104) or approximately a multiple of half a wavelength plus an eighth of a wavelength (i.e., λ/8+N*λ/2).
A third length 124, measured between the monopole 104 and the beginning of the tapered edge 106, can be less than about 0.2 wavelengths. For example and without limitation, the third length 124 can be as close to about 0 wavelengths as possible, depending on manufacturing constraints. Moreover, a fourth length 126, measured, from a top perspective of the mobile device antenna system 100, between the beginning of the taper and the tip or point of the edge 106, can be between, and including, about 0.2 and 0.5 wavelengths. For example and without limitation, the fourth length 126 can be approximately 0.4 wavelengths. Under the hypothetical scenario discussed above, (i.e., at a frequency of 26 GHz and the space surrounding the edge 106 having a relative permittivity of ε_r=3) the fourth length 126 (i.e., the wedge length) can be about 0.4 wavelengths or about 2.66 mm.
Moreover, in this particular embodiment, where the reflector 108 is included as either a rod or a wall, the first length 120 (i.e., the length of the ground plane 102 beyond the reflector) can be any suitable length as discussed above. The ground plane 102 can be such a length as to allow other components 110 to be mounted on it. These components can be any suitable component that can be mounted to a PCB that is desired. Because the reflector 108 works to reflect the radiation towards the edge 106, the ground plane 102 is not needed for reflecting of the radiation. Thus, the remainder of the ground plane 102 area within the range of the first length 120 can be used to mount other components 110.
Turning next to FIG. 4E, which illustrates a top view of another example mobile device antenna system 100 comprising a monopole 104 and a ground plane 102 with the tapered edge 106, where the length of the ground plane 102 is sized such that the ground plane 102 acts to reflect back the radiation towards the edge 106. As described above, the first length 120 is measured from the monopole 104 to the non-tapered edge of the ground plane 102. The first length 120 can be an even number of quarter wavelengths long. In other words, the first length 120 can be 2/4, 4/4, 6/4, etc. wavelengths long. In some embodiments, for example and without limitation, the first length 120 can be ½ wavelengths long. In this particular embodiment, the third distance 124, measured between the monopole 104 and the beginning of the taper, can be also be between and including about 0-0.2 wavelengths. The key here, again, is to have a distance between the monopole 104 and the edge to be as close to 0 wavelengths as manufacturing processes will allow. In some embodiments, the first length 120 can be three wavelengths. The fourth length 126 remains the same as the fourth length 126 in FIG. 4D.
Referring to FIG. 4F, which illustrates a top view of the example mobile device antenna system 100 comprising the monopole 104 between a slot 112 and the tapered edge 106. In this embodiment, the slot 112 replaces the reflector 108 as the mechanism configured to reflect radiation back towards the edge 106. The slot 112 can be a substantially rectangular hole formed (i.e., drilled, etched, or via other processes known to those having ordinary skill in the art) in the ground plane 102. In some embodiments, the slot 112 can be formed such that its largest dimension runs parallel to the tapered edge 106.
In such an embodiment, the first length 120 is measured between the monopole 104 and the other edge (i.e., non-tapered edge) of the ground plane 102, opposite the tapered edge 106. In some embodiments, the first length 120 can be similarly dimensioned to the case illustrated in FIG. 4D, where the reflector 108 is present. This is so because in this embodiment, the slot 112 is configured to act similarly as the reflector 108, thereby minimizing the impact that the size of the ground plane 102 has on the amount of radiation reflected back towards the edge 106. Additionally, a fifth length 123, measured between the monopole 104 and the slot 112 can be an even number of ¼ wavelengths (i.e., 2/4, 4/4, 6/4, etc. wavelengths). For example and without limitation, in some embodiments, the fifth length 123 can be about ½ wavelength. Moreover, the third length 124 and the fourth length 126 do not change. However, the width of the slot 128 (i.e., the shortest dimension of the slot 112 from a top two-dimensional view) can be between and including about 0.2-0.3 wavelengths.
In some embodiments, a length of the slot 129 (i.e., the largest dimension of the slot from a top two-dimensional view) can be greater than the width of the monopole 104 and greater than the width of the reflector as a rod shape, but the reflective benefit of the slot starts to diminish as the length of the slot 129 increases to more than about 1 wavelength. Reflectivity of the slot 112 will not increase much as it gets wider than 1 wavelength.
Referring to FIG. 4G, which illustrates a top view of the example mobile device antenna system 100 comprising the monopole 104 and the reflector 108 between the slot 112 and the tapered edge 106. In this particular embodiment, the slot 112 and the reflector 108 perform the necessary reflection of radiation, however, the vast majority of the reflection occurs from the reflector 108. In this embodiment, the first length 120 is very similar to the scenario in FIG. 4D, in that it can be any suitable length that fits within the mobile device because the reflector 108 and slot 112 are performing the reflection. The second length 122 can be about ¼ wavelength and the third length 124 can be between and including about 0-0.2 wavelengths. The fourth length 126 will remain the same.
Additionally, a fifth length 123 measured as the distance between the monopole 104 and the slot 112 can be about ½ a wavelength. In any event in some embodiments, for example and without limitation, the reflector 108 can be about ¼ wavelength away from the monopole 104 and the slot 112 can be about ½ wavelength away from the monopole 104.
Furthermore, the width 128 and length 129 of the slot 112 can remain the same as it was in FIG. 4F.
FIG. 4H illustrates the case where the reflector 108 is created at the interface between two mediums, a first dielectric medium 144 with a first relative permittivity ε₁and a second dielectric medium 146 having a second relative permittivity ε₂. In some embodiments, a reflection is created by having the first dielectric medium 144 (i.e., it could be ambient air or any other suitable material or dielectric medium) surrounding the one or more monopole antenna and a second dielectric medium 146 (i.e., it could also be ambient air or any other suitable material or dielectric medium) such that fields incident to the monopole antenna 104 and not being picked up by the monopole antenna 104 will travel to an interface created where the first dielectric medium 144 and the second dielectric medium 146 meet, and the fields will be reflected, including partially reflected, towards the monopole antenna 104.
In embodiments where ε₁>ε₂the reflection is positive and the distance from the monopole 104 to the “backside” boundary (i.e. second length 122) should be close to integer multiples (i.e., 0, 1, 2, etc.) of ½ wavelengths. For example and without limitation, in some embodiments, the second length 122 can be about ½ wavelength. The distance from the monopole 104 to the front side, distance 142 (i.e., in the direction of the wedge 106), should be a positive integer multiple (i.e., 1, 2, 3, etc.) of ½ wavelengths in the case for ε₁>ε₂. In some embodiments, for example and without limitation, the front side distance 142 can be about ½ wavelength as well. In some other embodiments, the front distance 142 can be approximately 1 wavelength and the second length 122 can be between and including about 0 and 0.05 wavelength.
In embodiments where ε₁<ε₂the reflection is negative and the distance from the monopole 104 to the “backside” boundary (i.e. second length 122) should be close to integer multiples (i.e., 0, 1, 2, etc.) of ¼ wavelengths. The distance from the monopole 104 to the front side, distance 142 (i.e., in the direction of the wedge 106), should be a positive integer multiple (i.e., 1, 2, 3, etc.) of ¼ wavelengths in the case for ε₁<ε₂.
Referring to FIG. 5A, which illustrates a perspective view of the mobile device antenna system 100 along with example dimensions of the various components described herein. From this illustration, those having ordinary skill in the art will appreciate better how the different components might appear and/or be dimensioned according to some embodiments of the present disclosure.
Referring to FIG. 5B, which illustrates a side view of the mobile device antenna system 100 along with example dimensions of the various components. Using the same hypothetical as described above (i.e., assuming a radio signal with a frequency of about 26 GHz, propagating in a media with a relative permittivity of ε_r=3) some of the other dimensions of the board can be multiples of wavelengths long. For example and without limitation, in some embodiments, the ground plane 102 can have a thickness 130 of between, and including, about 0.2 and 0.5 wavelengths. More specifically, in some embodiments, the ground plane 102 can have a thickness 130 of about 0.3 wavelengths, or about 2.06 mm according to the hypothetical described above.
However, in some embodiments the thickness 130 of the ground plane can change depending on the needed additional layers in the board. Next, in some embodiments, the monopole 104 can have a monopole height 134 of between, and including, about 0.1 and 0.4 wavelengths. More specifically, in some embodiments, the monopole 104 can have a monopole height 134 of about 0.24 wavelengths, or about 1.6 mm according to the hypothetical described above. In embodiments where the reflector 108 is included, the reflector 108 can have a reflector height 132 greater than, equal to, or less than the monopole height 134. For example and without limitation, the reflector 108 can have a reflector height 132 of between, and including, about 0.1 and 0.5 wavelengths. More specifically, in some embodiments, the reflector 132 can have a reflector height 132 of about 0.36 wavelengths, or about 2.37 mm according to the hypothetical described above.
In some embodiments, the wedge-shaped edge 106 is configured to reflect emanating radiation from the monopole 104 towards the edge 106. Those having ordinary skill in the art will appreciate that, depending on the angle created by the tapered edge 106, the amount and direction of the radiation reflected towards the edge 106 will be altered. Various dimensions of the edge 106 can help determine the angle created by the taper. Those having ordinary skill in the art will appreciate that, in some embodiments, the taper forms a triangle. The ground plane thickness 130 is approximately equal to the length of one side of the triangle, the fourth length 126 is approximately equal to the length of a second side of the triangle, and the hypotenuse 136 or angled length of the edge 106 can be calculated by using the Pythagorean theorem. For example and without limitation, the hypotenuse 136 can have a length of between, and including, about 0.28 and 0.71 wavelengths. More specifically, the hypotenuse 136 can have a length of approximately 0.5 wavelengths, or about 3.36 mm according to the hypothetical described above. Thus, those having ordinary skill in the art will appreciate that the edge 106 has a taper angle θ between and including about 20 and 70 degrees. For example and without limitation, in the hypotheticals described herein above, assuming the ground plane thickness 130 is 0.3 wavelengths and the wedge length 126 is 0.4 wavelengths, then the taper angle θ would be approximately 37°. Those having ordinary skill in the art can calculate the geometry and angles of the wedge shape by using traditional triangle geometry principles.
Referring to FIG. 5C, which illustrates a side view of the example mobile device antenna system 100 of FIG. 5B, except here, the sharp point of the edge 106 is cut off similar to the right trapezoid described in FIG. 2E. As discussed above, the thickness 130 of the ground plane can be altered to accommodate additional layers. In this scenario, all of the other dimensions remain the same except for the hypotenuse 136 and the wedge length 126, which are both cut short because the edge 106 does not have the sharp taper. The hypotenuse 136 can be appropriately sized by cutting off the acute corner and sized appropriately to reflect radiation at the desired angle off the edge 106. In order to keep the hypotenuse 136 in the cut-off scenario in FIG. 5C, the thickness 130 of the ground plane 102 can be increased such that the hypotenuse 136 increases such that it is about the same length (i.e., a length of between, and including, approximately 0.28 and 0.71 wavelengths, or, more specifically, the hypotenuse 136 can have a length of approximately 0.5 wavelengths, or about 3.36 mm according to the hypothetical described above) as the hypotenuse 136 in FIG. 5B.
Referring to FIG. 6A, which illustrates a perspective view of an example mobile device antenna system 100 having a ground plane 102 that is partially tapered, and the rest not tapered at all. In this particular example, only a portion of the edge 106 is tapered. As illustrated in FIG. 6A, as well as the front view of FIG. 6B, in some embodiments, the monopole 104 and reflector 108 can be spaced close to (i.e., but not within) the tapered edge 106 and centered between the boundaries of the taper 106. In this view, a width 140 of the tapered edge 106 extends from the monopole 104 by greater than or equal to about ½ wavelength on either side of the monopole 104.
Referring to FIG. 7A and FIG. 7B, which illustrate various embodiments of how multiple monopoles 104 can be incorporated onto the ground plane 102. For example and without limitation, as illustrated in FIG. 7A, in some embodiments, the example mobile device antenna system 100 can comprise a plurality (i.e., two) of monopoles 104 spaced apart from one another, each monopole 104 having a corresponding reflector 108 on the other side of the tapered edge 106 from them. In this particular embodiment, each of the plurality of monopoles 104 can be spaced apart by about ½ wavelength. FIG. 7B illustrates a similar embodiment, except instead of having respective reflectors, the mobile device antenna system 100 can comprise a single wall-shaped reflector 108 like that shown in FIG. 3F. In this embodiment, again, each of the monopoles 104 can be spaced apart by about ½ wavelength. In such an embodiment, the wall-shaped reflector will need to conform to the principles described herein, with respect to FIG. 3F and the width or extent of the wall-shaped reflector 108.
In some embodiments, the subject matter of the present disclosure also comprises a method of controlling a direction of radiation of one or more monopole antennas, the method comprising: positioning the one or more monopole antennas near a first edge of a ground plane; and reflecting radiation fields onto the one or more monopole antennas; wherein the first edge of the ground plane is tapered such that the first edge forms a wedge shape. In some embodiments, a radiation pattern of at least one of the one or more monopole antennas is directed substantially laterally towards the first edge. In some embodiments, the method further comprises providing at least one reflector on the ground plane; wherein the reflector has a shape that is configured to concentrate the radiation fields onto the one or more monopole antennas.
In some embodiments, for example and without limitation, the reflector has at least a partially cylindrical shape, a vertical wall shape, a parabolic shape, a hyperbolic shape, or an “L” shape having angles between and including about 30 and 175 degrees. In some embodiments, the method further comprises positioning one of the at least one reflector such that at least one monopole antenna of the one or more monopole antennas is positioned between the one reflector and the first edge of the ground plane. In some other embodiments, the method further comprises using the at least one reflector to further direct radiating electromagnetic signals back towards the first edge of the ground plane. In some embodiments, the ground plane extends less than about one wavelength to a second edge, opposite the first.
Moreover, in some embodiments, reflecting radiation fields onto the one or more monopole antennas comprises providing a first dielectric medium surrounding the one or more monopole antenna and a second dielectric medium such that fields incident to the one or more monopole antenna and not being picked up by the one or more monopole antenna will travel to an interface created where the first dielectric medium and the second dielectric medium meet, and the fields will be reflected, including partially reflected, towards the one or more monopole antenna
In some embodiments, the method further comprises positioning one of the at least one reflector between and including about 0.1 and 0.7 wavelengths away from the at least one monopole antenna; wherein a wavelength is equivalent to one wavelength of an operating or resonating frequency of the antenna system. In some embodiments, the method further comprises positioning at least one of the one or more monopole antennas less than about 0.2 wavelengths away from a beginning of the first edge of the ground plane that is tapered; wherein the beginning of the edge of the ground plane is a thickest portion of the taper; and wherein a wavelength is equivalent to one wavelength of an operating or resonating frequency of the antenna system. In some embodiments, the first edge has a taper angle of between and including about 20 and 70 degrees. In some embodiments, the first edge has a taper that terminates with a flat edge such that a cross-section of the first edge is shaped as a right trapezoid. In some embodiments, the ground plane extends more than about three wavelengths to a second edge, opposite the first edge.
The present subject matter can be embodied in other forms without departure from the spirit and essential characteristics thereof. The embodiments described therefore are to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described in terms of certain specific embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter.

Claims

What is claimed is:

1. An antenna system for a mobile device, the antenna system comprising:

a ground plane; and

one or more monopole antennas near a first edge of the ground plane;

wherein the one or more monopole antennas extends out from, and substantially orthogonal to, the ground plane; and

wherein the first edge of the ground plane is tapered such that the first edge forms a wedge shape.

2. The antenna system of claim 1, wherein a radiation pattern of at least one of the one or more monopole antennas is directed substantially laterally towards the first edge.

3. The antenna system of claim 1 further comprising at least one reflector on the ground plane;

wherein the reflector has a shape that is configured to concentrate radiation fields onto the one or more monopole antennas.

4. The antenna system of claim 3 wherein the reflector has at least a partially cylindrical shape, a vertical wall shape, a parabolic shape, a hyperbolic shape, or a “V” shape having angles between and including about 30 and 175 degrees.

5. The antenna system of claim 3 wherein a reflection is created by having a first dielectric medium surrounding the one or more monopole antenna and a second dielectric medium such that fields incident to the one or more monopole antenna and not being picked up by the one or more monopole antenna will travel to an interface created where the first dielectric medium and the second dielectric medium meet, and the fields will be reflected, including partially reflected, towards the one or more monopole antenna.

6. The antenna system of claim 3 wherein one of the at least one reflector is positioned such that at least one monopole antenna of the one or more monopole antennas is positioned between the one reflector and the first edge of the ground plane.

7. The antenna system of claim 3 wherein the at least one reflector is configured to further direct radiating electromagnetic signals towards the first edge of the ground plane.

8. The antenna system of claim 3 wherein the one of the at least one reflector is positioned between and including about 0.1 and 0.7 wavelengths away from the at least one monopole antenna; and

wherein a wavelength is equivalent to one wavelength of an operating or resonating frequency of the antenna system.

9. The antenna system of claim 3, wherein the ground plane extends less than about one wavelength to a second edge, opposite the first edge.

10. The antenna system of claim 1 wherein at least one of the one or more monopole antennas is positioned less than about 0.2 wavelengths away from a beginning of the edge of the ground plane that is tapered;

wherein the beginning of the edge of the ground plane is a thickest portion of the taper; and

11. The antenna system of claim 1 wherein the first edge has a taper angle of between and including about 20 and 70 degrees.

12. The antenna system of claim 1 wherein the first edge has a taper that terminates with a flat edge such that a cross-section of the first edge is shaped as a right trapezoid.

13. The antenna system of claim 1 wherein the ground plane extends more than about three wavelengths to a second edge, opposite the first edge.

14. A method of controlling a direction of radiation of one or more monopole antennas, the method comprising:

positioning the one or more monopole antennas near a first edge of a ground plane; and

reflecting radiation fields onto the one or more monopole antennas;

15. The method of claim 14 wherein a radiation pattern of at least one of the one or more monopole antennas is directed substantially laterally towards the first edge.

16. The method of claim 14 further comprising providing at least one reflector on the ground plane;

wherein the reflector has a shape that is configured to concentrate the radiation fields onto the one or more monopole antennas.

17. The method of claim 16 wherein the reflector has at least a partially cylindrical shape, a vertical wall shape, a parabolic shape, a hyperbolic shape, or a “V” shape having angles between and including about 30 and 175 degrees.

18. The method of claim 16 further comprising positioning one of the at least one reflector such that at least one monopole antenna of the one or more monopole antennas is positioned between the one reflector and the first edge of the ground plane.

19. The method of claim 16 further comprising using the at least one reflector to further direct radiating electromagnetic signals back towards the first edge of the ground plane.

20. The method of claim 16 wherein the ground plane extends less than about one wavelength to a second edge, opposite the first.

21. The method of claim 14 wherein reflecting radiation fields onto the one or more monopole antennas comprises providing a first dielectric medium surrounding the one or more monopole antenna and a second dielectric medium such that fields incident to the one or more monopole antenna and not being picked up by the one or more monopole antenna will travel to an interface created where the first dielectric medium and the second dielectric medium meet, and the fields will be reflected, including partially reflected, towards the one or more monopole antenna.

22. The method of claim 14 further comprising positioning one of the at least one reflector between and including about 0.1 and 0.7 wavelengths away from the at least one monopole antenna;

23. The method of claim 14 further comprising positioning at least one of the one or more monopole antennas less than about 0.2 wavelengths away from a beginning of the first edge of the ground plane that is tapered;

24. The method of claim 14 wherein the first edge has a taper angle of between and including about 20 and 70 degrees.

25. The method of claim 14 wherein the first edge has a taper that terminates with a flat edge such that a cross-section of the first edge is shaped as a right trapezoid.

26. The method of claim 14 wherein the ground plane extends more than about three wavelengths to a second edge, opposite the first edge.