Patent Application
20130027254
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
The present invention relates generally to antenna apparatus for use in electronic devices such as wireless or portable radio devices, and more particularly in one exemplary aspect to a multiband slotted loop or ring antenna, and methods of tuning and utilizing the same.
Internal antennas are an element found in most modern radio devices, such as mobile computers, mobile phones, Blackberry® Blackberry devices, smartphones, personal digital assistants (PDAs), or other personal communication devices (PCDs). Typically, these antennas comprise a planar radiating plane and a ground plane parallel thereto, which are connected to each other by a short-circuit conductor in order to achieve the matching of the antenna. The structure is configured so that it functions as a resonator at the desired operating frequency. It is also a common requirement that the antenna operate in more than one frequency band (such as dual-band, tri-band, or quad-band mobile phones), in which case two or more resonators are used.
Recent advances in the development of affordable and power-efficient display technologies for mobile applications (such as liquid crystal displays (LCD), light-emitting diodes (LED) displays, organic light emitting diodes (OLED), thin film transistors (TFT), etc.) have resulted in a proliferation of mobile devices featuring large displays, with screen sizes of for instance 89-100 mm (3.5-4 in.) in mobile phones, and on the order of 180 mm (7 in.) in some tablet computers. To achieve the best performance, display ground planes (or shields) are commonly used. These larger ground planes are required by modem displays, yet are no longer optimal for wireless antenna operation. Specifically, this lack of optimization stems from the fact that ground plane size plays a significant role in the design of the antenna for the air interface(s) of the device. As a result, antenna bandwidth is reduced due to, at least in part, impedance mismatch between antenna radiator and the large ground plane.
Furthermore, current trends increase demand for thinner mobile communications devices with large displays that are often used for user input (e.g., touch screen). This in turn requires a rigid structure to support the display assembly, particularly during the touch-screen operation, so as to make the interface robust and durable, and mitigate movement or deflection of the display. A metal body or a metal frame is often utilized in order to provide a better support for the display in the mobile device.
The use of metal enclosures/chassis, large ground planes, and the requirement for thinner device enclosure create new challenges for radio frequency (RF) antenna implementations. Typical antenna solutions (such as monopole, PIFA antennas) require ground clearance area and sufficient height from ground plane in order to operate efficiently in multiple frequency bands (a typical requirement of modem portable devices). These antenna solutions are often inadequate for the aforementioned thin devices with metal housings and/or chassis, as the vertical distance required to separate the radiator from the ground plane is no longer available. Additionally, the metal body of the mobile device acts as an RF shield and degrades antenna performance, particularly when the antenna is required to operate in several frequency bands
Various methods are presently employed to attempt to improve antenna operation in thin communication devices that utilize metal housings and/or chassis, such as for example a slot ring antenna described in European Patent Publication number EP1858112B1. This implementation requires fabrication of a slot within the printed wired board (PWB) in proximity to the feed point, as well as along the entire height of the device. For a device having a larger display, a slot location that is required for optimal antenna operation often interferes with device user interface functionality (e.g. buttons, scroll wheel, etc), therefore limiting device layout implementation flexibility.
Additionally, such metal housing must have openings in close proximity to the slot on both sides of the PCB. To prevent generation of radio frequency cavity modes within the device, the openings are typically connected using metal walls. All of these steps increase device complexity and cost, and impede antenna matching to the desired frequency bands of operation.
Another existing implementation employs a multi-resonant coupled feed antenna comprising a metal ring radiating element fitted around perimeter of the radio device. Several slots are fabricated within the radiator (typically on the sides) in order to achieve multiband antenna functionality; this approach unfortunately increases the cost and complexity of the device. Given that device users typically handle communication devices by their sides/edges, such configuration is susceptible to antenna detuning and communication failures due to a short circuit created when a user hand touches the radiator over the slot. Furthermore, wide slots (typically about 3 mm in width) are required to achieve the desired low band (typically 700-960 MHz) operation, and as such may adversely affect device aesthetic appeal.
Accordingly, there is a salient need for a wireless multiband antenna solution for e.g., a portable radio device, with a small form factor and which is suitable for the device perimeter, and that offers a lower cost and complexity, as well as providing for improved control of antenna resonance.
The present invention satisfies the foregoing needs by providing, inter alia, a space-efficient multiband antenna apparatus, and methods of tuning and use thereof.
In a first aspect of the invention, a mobile communications device is disclosed. In one embodiment, the device comprises: an enclosure and an electronics assembly contained substantially therein, the electronics assembly comprising a ground plane and at least one feed port; and a multiband antenna apparatus. The multiband antenna apparatus comprises: a first antenna structure comprising an element disposed substantially around an outside perimeter of the enclosure; and a second antenna structure comprising a plurality of monopole radiator branches. In one variant, the first antenna structure is connected to the ground plane in at least two ground points, thereby forming a virtual portion and an operational portion, the operational portion comprising a slot disposed in the element proximate a bottom side of the enclosure; an exterior perimeter of the virtual portion substantially envelops the ground plane; and an exterior perimeter of the operational portion is disposed external to the ground plane, and substantially envelops the second antenna structure.
In another embodiment, the mobile device comprises: a device enclosure; and an antenna having a substantially external radiator element, the radiator element having at least one slot disposed relative to the enclosure so as to minimize the potential for radiator element shorting across the slot due to device handling by a user during use of the device.
In one variant of the alternate embodiment, the radiator element comprises a substantially closed loop, and the at least one slot comprises a single slot disposed substantially on a bottom edge of the enclosure of the device, the bottom edge being not normally grasped by the user during the use of the device.
In another variant, the radiator element comprises a substantially closed loop disposed on top, bottom and side edges of the enclosure of the mobile device; and the at least one slot comprises a single slot disposed at either one of the top or the bottom edges.
In a second aspect of the invention, a multiband antenna apparatus is disclosed. In one embodiment, the apparatus is adapted for use in a portable radio communications device, and comprises: a first antenna structure comprising an element configured to be disposed substantially around an outside perimeter of a device enclosure. In one variant, the first antenna structure is connected to a ground plane of the device in at least two locations, thereby forming a virtual portion and an operational portion; and the operational portion comprises a slot formed in the element so as to be disposed proximate a bottom side of the enclosure.
In another variant, an exterior perimeter of the virtual portion substantially envelops the ground plane; and an exterior perimeter of the second antenna structure is disposed external to the ground plane.
In yet another variant, the slot is configured to effect antenna resonance in at least one upper frequency band.
In a third aspect of the invention, a method of operating a multiband antenna apparatus is disclosed. In one embodiment, the antenna apparatus if for use in a portable radio device and has a feed, a loop radiator element disposed substantially around a perimeter region of an enclosure of the device. The loop radiator element has a slot disposed substantially at a bottom edge of the enclosure, and a ground plane of the radio device is disposed a distance away from a bottom edge of the loop radiator element. The method comprises: energizing the feed with a feed signal comprising a lower frequency component and a higher frequency component; and causing radio frequency oscillations in the loop radiator element at least at the higher frequency. The slot is configured to effect tuning of the antenna apparatus in the range of the higher frequency.
In a fourth aspect of the invention, a method of mitigating the effects of user interference on a radiating and receiving mobile device is disclosed. In one embodiment, the mobile device is characterized by a preferred user grasping location, and the method comprises: energizing a loop antenna element with a signal comprising at least a first frequency component; the loop radiator element being disposed substantially around a perimeter region of an enclosure of the device, and causing an electromagnetic field across a slot formed within the loop antenna element. The slot is distally located relative to the preferred grasping location so as to mitigate electromagnetic interference due to the grasping by the user.
In a fifth aspect of the invention, a method of tuning a multiband antenna apparatus is disclosed.
Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description.
The features, objectives, and advantages of the invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein:
All Figures disclosed herein are © Copyright 2011 Pulse Finland Oy. All rights reserved.
Reference is now made to the drawings wherein like numerals refer to like parts throughout.
As used herein, the terms “antenna,” “antenna system,” “antenna assembly”, and “multi-band antenna” refer without limitation to any apparatus or system that incorporates a single element, multiple elements, or one or more arrays of elements that receive/transmit and/or propagate one or more frequency bands of electromagnetic radiation. The radiation may be of numerous types, e.g., microwave, millimeter wave, radio frequency, digital modulated, analog, analog/digital encoded, digitally encoded millimeter wave energy, or the like.
As used herein, the terms “board” and “substrate” refer generally and without limitation to any substantially planar or curved surface or component upon which other components can be disposed. For example, a substrate may comprise a single or multi-layered printed circuit board (e.g., FR4), a semi-conductive die or wafer, or even a surface of a housing or other device component, and may be substantially rigid or alternatively at least somewhat flexible.
The terms “frequency range”, “frequency band”, and “frequency domain” refer without limitation to any frequency range for communicating signals. Such signals may be communicated pursuant to one or more standards or wireless air interfaces.
As used herein, the terms “portable device”, “mobile computing device”, “client device”, “portable computing device”, and “end user device” include, but are not limited to, personal computers (PCs) and minicomputers, whether desktop, laptop, or otherwise, set-top boxes, personal digital assistants (PDAs), handheld computers, personal communicators, tablet computers, portable navigation aids, J2ME equipped devices, cellular telephones, smartphones, personal integrated communication or entertainment devices, or literally any other device capable of interchanging data with a network or another device.
Furthermore, as used herein, the terms “radiator,” “radiating plane,” and “radiating element” refer without limitation to an element that can function as part of a system that receives and/or transmits radio-frequency electromagnetic radiation; e.g., an antenna or portion thereof.
The terms “RF feed,” “feed,” “feed conductor,” and “feed network” refer without limitation to any energy conductor and coupling element(s) that can transfer energy, transform impedance, enhance performance characteristics, and conform impedance properties between an incoming/outgoing RF energy signals to that of one or more connective elements, such as for example a radiator.
As used herein, the terms “loop” and “ring” refer generally and without limitation to a closed (or virtually closed) path, irrespective of any shape or dimensions or symmetry.
As used herein, the terms “top”, “bottom”, “side”, “up”, “down”, “left”, “right”, and the like merely connote a relative position or geometry of one component to another, and in no way connote an absolute frame of reference or any required orientation. For example, a “top” portion of a component may actually reside below a “bottom” portion when the component is mounted to another device (e.g., to the underside of a PCB).
As used herein, the term “wireless” means any wireless signal, data, communication, or other interface including without limitation Wi-Fi, Bluetooth, 3G (e.g., 3GPP, 3GPP2, and UMTS), HSDPA/HSUPA, TDMA, CDMA (e.g., IS-95A, WCDMA, etc.), FHSS, DSSS, GSM, PAN/802.15, WiMAX (802.16), 802.20, narrowband/FDMA, OFDM, PCS/DCS, Long Term Evolution (LTE) or LTE-Advanced (LTE-A), analog cellular, CDPD, satellite systems such as GPS, millimeter wave or microwave systems, optical, acoustic, and infrared (i.e., IrDA).
The present invention provides, in one salient aspect, a multiband antenna apparatus for use in a mobile radio device. The antenna apparatus advantageously provides reduced complexity and cost, and improved antenna performance, as compared to prior art solutions. In one embodiment, the mobile radio device comprises a metallic structure (e.g., a loop or ring) that at least partly encircles the outside perimeter of the device enclosure, and acts as the antenna radiating element. The “loop” radiator in one implementation comprises a single narrow slot disposed so as to minimize potential radiator shorting over the slot due to device handling during use, and to improve device visual appeal.
The exemplary embodiment of the multiband antenna apparatus further comprises a tuning circuit, including multiple branches each configured to effect antenna tuning in a predetermined frequency band. The metallic loop is grounded to the device ground plane at multiple locations, thus controlling the electrical length of the antenna. The dimensions of the slot are selected to optimize antenna performance in an upper frequency band of operation. The slot location effects low band lower band resonance frequency, which is configured to reside well below the lowest operating frequency of the antenna for proper operation of the radio device. In one approach, antenna lower band operation is tuned using an inductor connected in series between the feed and the lower band resonance circuit.
Advantageously, antenna coupling to the device electronics with the exemplary antenna disclosed herein is much simplified, as only a single feed connection is required (albeit not limited to a single feed). In one particular implementation, an upper frequency band tuning strip is galvanically connected to the loop element, thereby enabling tuning of the highest upper band resonances without changing or adversely affecting the visual appearance of the device
In another implementation, the tuning element is capacitively coupled via an electromagnetic field induced over a non-conductive gap between the tuning strip and the loop radiator.
Methods of tuning and operating the antenna apparatus are also disclosed.
Detailed descriptions of the various embodiments and variants of the apparatus and methods of the invention are now provided. While primarily discussed in the context of mobile devices, the various apparatus and methodologies discussed herein are not so limited. In fact, many of the apparatus and methodologies described herein are useful in any number of complex antennas, whether associated with mobile or fixed devices, cellular or otherwise.
Referring now to
A metal loop or ring 110 is disposed substantially at the outside perimeter of the device housing, as shown in
The ring 110 of
The ground points 116, 117 are used for antenna tuning, and their locations effectively define the length of the ring or loop antenna operational portion (i.e., the portion of the antenna that emits/receives RF radiation). The ground points 115, 119 are preferably separated by a distance that is less than a quarter wavelength of the antenna (at the highest operating frequency). In one variant, the ground structure 115 is configured to cover the majority of the upper edge of the ring, as shown in
The ring upper part (i.e., bounded by the ground points 116, 117, 119, 115 and marked by the broken line rectangle 112 in
As a brief aside, the antenna of the embodiment shown in
Returning now to
Moreover, the present invention contemplates the use of (i) a slot with a varying or non-constant width (that is: different slot width at different locations across the ring thickness); and (ii) use of two or more slots.
In the embodiment of
Antenna frequency tuning in the illustrated embodiment is achieved as follows: the tuning branch 124 effects antenna tuning in a first lower frequency band (LFB1), which corresponds to antenna low frequency resonance f1. In one variant, the LFB1 comprises frequency band from 824 to 894 MHz, and f1 is centered at about 850 MHz (also referred to as the 850 MHz band). In another variant, the LFB1 comprises frequency band from 880 to 960 MHz, and f1 is centered at about 900 MHz (also referred to as the 900 MHz band).
In one variant of the embodiment of
In one implementation, the tuning circuit 136 comprises a coil configured to provide a series inductance of about 10 nano-Henry (nH) to the radiator branch 124, with LFB1 being the 850 MHz band, and LFB2 being the 900 MHz band. As will be appreciated by those skilled in the art, other tuning element implementations are equally applicable to the invention including, but not limited to a discrete inductor, a capacitive element, or a combination thereof.
Antenna operation of the embodiment shown in
The antenna high frequency operational range is formed by at least two high frequency resonances, hereinafter referred to as the f2 resonance and the f3 resonance. The first high frequency resonance (f2) is formed by the shorter portion 127 of the ring 110 formed between the slot 114 and the ground point 116. Antenna tuning of this resonance is achieved in the illustrated embodiment by varying the length of the strip in the tuning branch 130. The tuning branch 130 is coupled to the ring 110 either galvanically or capacitively, as described in detail below with respect to
The directly fed antenna high frequency tuning structure 128 is configured to form a resonance at the second high frequency resonance (f3). The value of the f3 resonance is tuned in the illustrated embodiment by the length of the tuning branch 128 (and its proximity to the bottom portion of the ring). Each of the f2 and f3 resonances may be configured to provide antenna functionality in one or more upper frequency bands.
In one variant, the combination of f2 and f3 resonance bands spans a frequency range from about 1710 MHz to 2170 MHz, thus enabling device operation in the following high-frequency bands of an LTE-compliant system: 1710-1880 MHz, 1850-1990 MHz, and 1930-2170 MHz, corresponding to UFB1-UFB3, respectively.
In another embodiment, the directly fed low frequency range radiating structure 122 is used, in combination with the tuning branch 124, to form a harmonic resonance, referred to as the f4 resonance, of a frequency component of the low frequency range, thereby effecting antenna operation in a fourth upper frequency band (UFB4). The value of the UFB4 is tuned by the length of the horizontal branch 122 of the C-shaped structure (having two turns) formed by the tuning branches 122, 124 of
Referring now to
In another embodiment (shown in
In the capacitive coupling setup, the dielectric gap between the tuning strip and the operational portion of the metal ring needs to be sufficiently small in order to form the gap resonance above the highest operating frequency of the antenna. Capacitive coupling of the tuning branch to the ring structure does not require any physical attachment (e.g., soldering, welding) of the tuning structure to the ring, therefore advantageously facilitating antenna manufacturing and allowing for a wider range of material selection.
The gap between the ring portion 127 and the tuning branch 142 causes a gap resonance at a frequency that is defined by the capacitance between the surfaces of the ring portion 127 and the tuning branch 142 due to a strong electric field between these surfaces. Reducing the gap creates a tighter coupling between these elements, and shifts the gap resonance frequency higher and beyond the antenna operating bands. The gap resonance frequency is further affected by the size the overlapping surface area (also referred to as the coupling area) between the strips 144, 146 of the tuning branch 142 and the ring portion 127. Larger coupling area allows for a larger gap.
In another embodiment (not shown), the multiband antenna is configured without the tuning element 136, thereby forming a 4-band resonator with a single lower band frequency band LFB1 and three upper frequency bands (UFB1, UFB2, UFB3).
In another aspect of the invention, the antenna structure (such as that shown in
An efficiency of zero (0) dB corresponds to an ideal theoretical radiator, wherein all of the input power is radiated in the form of electromagnetic energy.
The curves marked with designators 402-412 in
Comparison between the two antenna responses 510, 512 demonstrates an increased antenna bandwidth in the lower frequency range for the response 510, which allows antenna operation in the 850 MHz and 900 MHz lower frequency bands.
The data presented in
Advantageously, the slotted loop or ring antenna configuration (as in the illustrated embodiments described herein) further allows for improved device operation by reducing potential for antenna shorting (and associated adverse effects) due to user handling, in addition to the aforementioned breadth and multiplicity of operating bands. Furthermore, the use a bottom-placed gap (for example, a small single gap as shown in the exemplary embodiments herein) improves device aesthetic appeal in that the bottom of the device is rarely if ever seen during use, and reduces the need for non-conductive or decorative covering elements (often required in prior art solutions), thereby reducing the device cost as well.
It will be recognized that while certain aspects of the invention are described in terms of a specific sequence of steps of a method, these descriptions are only illustrative of the broader methods of the invention, and may be modified as required by the particular application. Certain steps may be rendered unnecessary or optional under certain circumstances. Additionally, certain steps or functionality may be added to the disclosed embodiments, or the order of performance of two or more steps permuted. All such variations are considered to be encompassed within the invention disclosed and claimed herein.
While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the invention. The foregoing description is of the best mode presently contemplated of carrying out the invention. This description is in no way meant to be limiting, but rather should be taken as illustrative of the general principles of the invention. The scope of the invention should be determined with reference to the claims.
