Patent Application
20130154886
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 an internal multiband antenna for use with conductive enclosures, 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® 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. These trends, combined with user demands for robust and ascetically attractive device enclosures, increase the use of metal chassis and all-metal device enclosures. These metal enclosures and components often act as electromagnetic shields and reduce antenna efficiency and bandwidth, which adversely affects operation of internal radio frequency antennas, particularly at low frequencies.
Furthermore, modern third and fourth generation high-speed wireless networks, such as Wideband Code Division Multiple Access (W-CDMA), Universal Mobile Telecommunications System (UMTS), High-Speed Packet Access (HSPA), and 3GPP Long Term Evolution (LTE/LTE-A), require radio devices that operate in multiple frequency bands over a wide range of frequencies (e.g., 700 MHz to 2700 MHz).
Various methods are presently employed to attempt to improve antenna operation with metallic or metalized enclosures. Capacitively fed monopole antennas achieve wide bandwidth using switches. However, the use of electrical switching requires specialized matching, and often results in high electrical losses. Some existing solutions utilize various cut-outs and partial metalized enclosures in order to minimize antenna radiation losses and improve performance. In addition, active switching and tuning circuits require additional components which increase complexity, cost and size of the portable radio device. As the number of supported frequency bands increases (e.g., to support LTE/LTE-A), active switching antennas become more difficult to implement in metalized enclosures while maintaining antenna performance (and obeying aesthetic considerations such as shape and size).
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 use with metal/metalized device enclosures. Ideally, such solution would also offer a lower cost and complexity, as well as supporting multiple frequency bands while maintain good radiation efficiency.
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, an antenna apparatus is disclosed. In one embodiment, the apparatus comprises: a loosely coupled main antenna radiator having a single feed point connection; and a diversity antenna element. The antenna apparatus is configured to utilize at least a portion of a metallic enclosure of a host device as a parasitic resonator; and is capable of at least receiving signals in a plurality of frequency bands within both lower and upper operating frequency ranges.
In one variant, the antenna apparatus does not include any tuning circuitry or switches.
In another variant, the host device includes a mobile cellular telephone, and the frequency bands are at least in part compliant with those specified in the Long Term Evolution (LTE) wireless standard.
In yet another variant, the antenna apparatus forms a first parasitic resonator using the main antenna radiator, and a second parasitic resonator using the diversity antenna element.
In a second aspect of the invention, a radio frequency communications device is disclosed. In one embodiment, the device includes: an electronics assembly comprising a ground plane and a feed port; at least partially electrically conductive external enclosure comprising a main portion enclosing the electronics assembly, and a first end cap enclosing a first antenna radiator having a feed structure connected to the feed port. The first antenna radiator is configured to operate in at least a first frequency band; and the first end cap is connected to the ground plane at least at a first location, thereby forming a first parasitic radiator in a second frequency band.
In one variant, the first antenna radiator and the first parasitic radiator form a first multiband antenna apparatus; and the first parasitic radiator is configured to widen an operating bandwidth of the first multiband antenna apparatus.
In another variant, the grounding of the first end cap is configured to increase radiation efficiency of the multiband antenna apparatus.
In another variant, the first end cap is disposed proximate a first end of the device, and the external enclosure is fabricated from metal (e.g., all metal, or a non-conductive carrier and a conductive layer disposed thereon).
In yet another variant, the main portion is connected to ground in at least one location; and the connection of the first end cap to the ground plane is effected via the main portion.
In a third aspect of the invention, a multiband antenna apparatus for use in a radio communications device is disclosed. In one embodiment, the device has at least partially conductive external enclosure, and the antenna apparatus comprising a directly fed radiator structure having a feed portion configured to be connected to feed port of the radio communications device. The directly fed radiator structure is operable in at least a first frequency band and configured to be electromagnetically coupled to an end cap portion of the external enclosure; the end cap is electrically connected to a ground plane of the radio device via a ground structure; the grounding of the end cap is configured to widen operating bandwidth of the multiband antenna apparatus; and the enclosing of the directly fed radiator structure by the end cap and the grounding of the end cap cooperate to form a parasitically-fed radiator of the antenna apparatus in a second frequency band.
In one variant, the grounding of the end cap is configured to increase radiation efficiency of the multiband antenna apparatus, and the second band is lower than the first band.
In another variant, the end cap is configured to substantially enclose the directly fed radiator structure on at least on five sides.
In yet another variant, the directly fed radiator structure includes a first portion configured substantially parallel to the ground plane, and a second portion configured substantially perpendicular to the ground plane. The antenna includes a parasitic radiator disposed proximate to the feed portion and configured to form an electromagnetically coupled resonance in at least a third frequency band.
In a fourth aspect of the invention, a method of expanding operational bandwidth of a multiband antenna useful in a radio device is disclosed. In one embodiment, the device has an at least partially conductive external enclosure, and the method includes: energizing a first radiator structure in at least a first frequency band by effecting an electric connection between the first radiator and a feed port of the radio device; and energizing a second antenna radiator structure in at least a second frequency band by: (i) electromagnetically coupling the second radiator structure to the feed port; and (ii) effecting an electric ground connection between the second radiator structure and a ground plane of the radio device.
In one variant, the second radiator structure includes an end cap portion of the external enclosure; and the end cap portion is connected to the ground plane at least at a first location that is selected to widen operating bandwidth of the multiband antenna.
In a fifth aspect of the invention, an antenna radiator structure for use in a wireless device is disclosed. In one embodiment, the structure includes: a directly fed radiating element in electrical communication with a feed structure; and a second radiating element with a slot formed therein. The directly fed radiating element and the second radiating element are configured to be disposed in a substantially perpendicular orientation when installed within a host device enclosure.
In one variant, the structure further includes a parasitic element adapted for communication with a ground of the host device, the parasitic element configured for placement proximate the feed structure and to resonate at a frequency other than that of the directly fed radiating element or the second radiating element.
In another variant, the slot is configured to create a first resonant frequency of a high frequency band associated with the structure. The directly fed radiating element includes an end portion used to tune a first harmonic of a low band resonance into the high frequency band, thus forming a second high frequency resonance.
In another aspect of the invention, a method of operating a multiband antenna apparatus is disclosed. In one embodiment, the antenna apparatus is for use in a portable radio device, and the method includes causing a resonance in a parasitic resonator of the antenna to create a frequency band outside the main antenna band(s).
In yet another 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 “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), TD-LTE, 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 having an electrically conductive enclosure. The exemplary embodiments of the antenna apparatus described herein advantageously offer reduced complexity and cost, and improved antenna performance, as compared to prior art solutions. In one implementation, the antenna apparatus comprises a main antenna radiator disposed on one end of the device enclosure, and diversity or a multiple-input multiple-output (MIMO) antenna radiator disposed on opposite end. The mobile radio device comprises a metallic enclosure (e.g., a fully metallic, or an insulated metal carrier) which comprises a main portion and two antenna cover portions (caps) that substantially completely enclose the main and the diversity antenna radiating elements, respectively. Both antenna caps are separated from the main enclosure portion by a narrow gap extending along the circumference of the device. In order to reduce losses due to handling during operation, the surface of metal cover may be comprise a non-conductive layer, e.g., plastic film.
The main antenna radiator comprises a loosely-coupled antenna, which is also referred to as the ring antenna. The feed of the main antenna is connected to the device RF feed structure, thus requiring only a single connection between the main antenna radiator and the device electronics. The main portion of the device conductive enclosure is connected to ground at one or more predetermined locations. In one implementation, the main portion is grounded at four points (two per side, one on each end) disposed substantially along a longitudinal axis of the enclosure. In another implementation, additional grounding points are used, such as, for example, proximate the device sides.
The cap portion that covers the main antenna feed is loosely coupled to the feed element, thus forming a parasitic antenna resonator. In some implementations, the antenna cap is connected to device ground plane in order to adjust antenna resonant frequency in low frequency band, to widen the antenna bandwidth, and to enhance radiation efficiency of the antenna.
Advantageously, the coupling of the feeding element to the grounded (short-circuited) metallized cover portion surrounding the feeding element and being a part of metallized phone enclosure enables the cover portion to operate as a parasitic antenna resonator at low frequencies. Furthermore, coupling of the main and diversity antenna to the device electronics described herein is much simplified, as only a single feed connection is required (albeit not limited to a single feed).
In one particular implementation, a high frequency band parasitic resonator structure is disposed proximate to the directly fed radiator structure of the feeding element radiator in order to widen antenna operating bandwidth. The parasitic structure is located along one side of the device enclosure and is galvanically connected to ground.
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 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 (e.g., base stations or femtocells), cellular or otherwise.
Referring now to
A printed circuit board (PCB), comprising radio frequency electronics and a ground plane, is disposed within the device 100. In one variant, the enclosure 101 is fabricated using a plastic carrier structure with a metalized conductive layer (e.g., copper alloy) disposed on its external surface.
As shown in
In one approach, the end caps are fabricated from solid metal, and are spaced from the feeding element by a predetermined distance (typically on the order of 1 mm). In another approach, the end caps comprise a metal covered plastic, fabricated by any suitable manufacturing method (such as, for example laser direct structuring, (LDS)). In this variant, the plastic thickness provides sufficient gap between the metal end cap portion and the feed structure; hence, additional spacing is not required.
The first end cap 104 is separated from the main portion 102 by a gap 122, and the other end cap 106 is separated from the main portion 102 by a gap 130. In the embodiment shown in
The main portion 102 of the enclosure is connected to the ground plane device (not shown) at multiple locations 118, 128, 119, 129 in order to achieve good coupling, and to minimize electrostatic discharge (ESD) problems. In the embodiment of
In one variant, additional ground contacts (not shown) are disposed along the left and right sides of the main portion in order to minimize potential occurrence of unwanted resonances, thereby improving the robustness of antenna operation.
The radio device 100 comprises a main antenna apparatus 114 and a diversity antenna apparatus 116, disposed proximate the bottom and top ends of the device, respectively, as shown in
The main antenna 114, in the embodiment shown in
The main antenna end cup 104 is connected to PCB ground at a grounding structure 121. As shown in the embodiment of
In some embodiments, the diversity antenna 116 comprises a capacitively fed monopole antenna, such as for example that described in PCT Patent Publication No. 2011/101534, entitled “ANTENNA PROVIDED WITH COVER RADIATOR”, incorporated herein by reference in its entirety.
Referring now to
In one embodiment, the antenna feeding structure 202 comprises a parasitically coupled feed structure that is electrically connected to the main enclosure portion (or PCB ground) via the grounding structure 120, and which forms a parasitically coupled resonance in the high frequency range, thereby increasing the antenna operating bandwidth.
As used herein, the terms “low frequency” and “high frequency” are used to describe a first frequency range which is lower in frequency than the second range, respectively, and which may contain multiple bands. In the exemplary embodiment, the lower range extends from about 800 MHz to about 950 MHz, while the high or upper frequency range extends from about 1700 MHz to about 2700 MHz. However, the invention described herein is not so limited, and other frequency band configurations (including those which overlap with one another) may be used consistent with the invention, based on the specific application The main antenna apparatus 114, including the feeding element 202 and the main end cap radiator 104, comprises a loosely-coupled antenna structure, which is also referred to as a “ring antenna”. The ring antenna is formed, in one embodiment, by electromagnetically coupling the directly fed radiator 208 to the short-circuited conductive end cap enveloping the radiator surrounding the feeding element, and by virtue of being a part of metallized phone enclosure. In one implementation, only a single electrical connection between the device PCB and the antenna radiator is advantageously required (i.e., the feed connection 204), thereby simplifying manufacturing and construction.
The parasitic element 314 is disposed proximate the feed structure 304 so as to ensure sufficient electromagnetic coupling to the antenna feed port via the slot 316 formed between the elements 304, 314, thus forming a third high frequency resonance (FH3).
As will be understood by those skilled in the arts when given this disclosure, the radiator structure of
The five antenna frequency bands in this sample include two 850 MHz and 900 MHz low frequency bands, and three upper frequency bands (i.e., 1,710-1,880 MHz, 1,850-1,990 MHz, and 1,920-2,170 MHz). The solid lines designated with the designators 402 in
The curves marked with designators 410, 420, 430 in
Data presented in
Exemplary antenna isolation data (not shown) obtained by the Assignee hereof reveals about 9 dB, 17 dB of antenna isolation in the lower and upper frequency ranges, between the main and the diversity antennas. Such increased isolation advantageously reduces potential detrimental effects due to e.g., Electrostatic Discharge (ESD) during device operation.
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.
Measurement presented in
The total efficiency measurements presented in
The data presented in
Furthermore, a multiband antenna configured according to the invention advantageously does not require matching circuitry (thereby saving cost and space), and comprises a passive structure that does not use active switching, thus further reducing radiation losses, antenna size, and cost. A single connection to the device electronics is also utilized, which simplifies antenna installation and increases operational robustness. Increased bandwidth, particularly at lower frequencies, lower loses and improved isolation allow antenna multiband operation with a fully metallic device covers, while maintaining the same performance, device size, and/or antenna cost as with non-metallized or only partially metallized device covers.
This capability advantageously allows operation of a portable computing device with a single antenna over several mobile frequency bands such as GSM850, GSM900, GSM1900, GSM1800, PCS-1900, as well as LTE/LTE-A and/or WiMAX (IEEE Std. 802.16) frequency bands. Furthermore, the use of a separate tuning branch enables formation of a higher order antenna resonance, therefore enabling antenna operation in an additional high frequency band (e.g., 2500-2600 MHz band). Such capability further expands antenna uses to, inter alia, Wi-Fi (802.11) and additional LTE/LTE-A bands. As persons skilled in the art will appreciate, the frequency band composition given above may be modified as required by the particular application(s) desired, and additional bands may be supported/used 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.
In one approach, a half-cup implementation may be used so that there is no metal on one side (for example, the top side of the device that, typically, comprises a display
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.
