Antenna isolation for portable electronic devices

Portable electronic devices are provided with wireless circuitry that includes antennas and antenna isolation elements. The antennas may include antennas that have multiple arms and that are configured to handle communications in multiple frequency bands. The antennas may also include one or more antennas that are configured to handle communications in a single frequency band. The antennas may be coupled to different radio-frequency transceivers. For example, there may be first, second, and third antennas and first and second transceivers. The first and third antennas may be coupled to the first transceiver and the second antenna may be coupled to the second transceiver. The antenna isolation elements may be interposed between the antennas and may serve to reduce radio-frequency interference between the antennas. There may be a first antenna isolation element between the first and second antennas and a second antenna isolation element between the second and third antennas.

BACKGROUND

This invention relates generally to wireless communications circuitry, and more particularly, to wireless communications circuitry with antenna isolation for electronic devices such as portable electronic devices.

Handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers.

Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations. Cellular telephones and other devices with cellular capabilities may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portable electronic devices may also use short-range wireless communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) band at 2.4 GHz and the Bluetooth® band at 2.4 GHz. Communications are also possible in data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System band).

To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. For example, manufacturers have made attempts to miniaturize the antennas used in handheld electronic devices.

A typical antenna may be fabricated by patterning a metal layer on a circuit board substrate or may be formed from a sheet of thin metal using a foil stamping process. Antennas such as planar inverted-F antennas (PIFAs) and antennas based on L-shaped resonating elements can be fabricated in this way. Antennas such as PIFA antennas and antennas with L-shaped resonating elements can be used in handheld devices.

Although modern portable electronic devices often use multiple antennas, it is challenging to produce successful antenna arrangements in which multiple antennas operate in close proximity to each other without experiencing undesirable interference.

It would therefore be desirable to be able to provide improved antenna structures for wireless electronic devices.

SUMMARY

A portable electronic device such as a handheld electronic device is provided with wireless communications circuitry that includes antennas and antenna isolation elements. The antenna isolation elements may be interposed between respective antennas to reduce radio-frequency interference between the antennas and thereby improve antenna isolation.

With one suitable arrangement, there are at least three antennas in the wireless communications circuitry. The three antennas may each have a respective antenna resonating element. The antenna resonating elements may be formed from conductive structures such as traces on a flex circuit or stamped metal foil structures (as examples). Each antenna resonating element may have at least one antenna resonating element arm. The arms may be aligned along a common axis.

The antenna isolation elements may be formed from antenna isolation resonating elements such as L-shaped strips of conductor. The L-shaped conductive strips may have arms that are aligned with the common axis.

The antennas and the antenna isolation elements may share a common ground plane. With this type of configuration, a first antenna resonating element and the ground plane form a first antenna, a second antenna resonating element and the ground plane form a second antenna, a third antenna resonating element and a ground plane form a third antenna, a first antenna isolation resonating element and the ground plane form a first antenna isolation element, and a second antenna isolation resonating element and the ground plane form a second antenna isolation element.

If desired, some of the antennas and resonating elements may have multiple arms. For example, the first and third antenna resonating elements may have arms that are aligned with the common axis and arms that are perpendicular to the common axis.

The first and third antennas may be used to implement an antenna diversity scheme. With one suitable arrangement, a Wi-Fi transceiver that operates at 2.4 GHz and 5.1 GHz is coupled to the first and third antennas, whereas a Bluetooth transceiver that operates at 2.4 GHz is coupled to the second antenna. Antenna isolation elements that operate at 2.4 GHz may be placed between the first and second antennas and between the second and third antennas, thereby isolating the first antenna from the third antenna at 2.4 GHz and isolating the first and third antennas from the second antenna at 2.4 GHz.

DETAILED DESCRIPTION

The present invention relates generally to wireless communications, and more particularly, to wireless electronic devices and antennas for wireless electronic devices.

The wireless electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices are handheld electronic devices.

The wireless electronic devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. The wireless electronic devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid portable electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples.

An illustrative portable electronic device in accordance with an embodiment of the present invention is shown inFIG. 1. Device10ofFIG. 1may be, for example, a handheld electronic device.

Device10may have housing12. Antennas for handling wireless communications may be housed within housing12(as an example).

Housing12, which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. In some situations, housing12or portions of housing12may be formed from a dielectric or other low-conductivity material, so that the operation of conductive antenna elements that are located in proximity to housing12is not disrupted. Housing12or portions of housing12may also be formed from conductive materials such as metal. An illustrative housing material that may be used is anodized aluminum. Aluminum is relatively light in weight and, when anodized, has an attractive insulating and scratch-resistant surface. If desired, other metals can be used for the housing of device10, such as stainless steel, magnesium, titanium, alloys of these metals and other metals, etc. In scenarios in which housing12is formed from metal elements, one or more of the metal elements may be used as part of the antennas in device10. For example, metal portions of housing12may be shorted to an internal ground plane in device10to create a larger ground plane element for that device10. To facilitate electrical contact between an anodized aluminum housing and other metal components in device10, portions of the anodized surface layer of the anodized aluminum housing may be selectively removed during the manufacturing process (e.g., by laser etching).

Housing12may have a bezel14. The bezel14may be formed from a conductive material and may serve to hold a display or other device with a planar surface in place on device10. As shown inFIG. 1, for example, bezel14may be used to hold display16in place by attaching display16to housing12.

Display16may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, or any other suitable display. The outermost surface of display16may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display16or may be provided using a separate touch pad device. An advantage of integrating a touch screen into display16to make display16touch sensitive is that this type of arrangement can save space and reduce visual clutter.

Display screen16(e.g., a touch screen) is merely one example of an input-output device that may be used with electronic device10. If desired, electronic device10may have other input-output devices. For example, electronic device10may have user input control devices such as button19, and input-output components such as port20and one or more input-output jacks (e.g., for audio and/or video). Button19may be, for example, a menu button. Port20may contain a 30-pin data connector (as an example). Openings24and22may, if desired, form microphone and speaker ports. In the example ofFIG. 1, display screen16is shown as being mounted on the front face of handheld electronic device10, but display screen16may, if desired, be mounted on the rear face of handheld electronic device10, on a side of device10, on a flip-up portion of device10that is attached to a main body portion of device10by a hinge (for example), or using any other suitable mounting arrangement.

A user of electronic device10may supply input commands using user input interface devices such as button19and touch screen16. Suitable user input interface devices for electronic device10include buttons (e.g., alphanumeric keys, power on-off, power-on, power-off, and other specialized buttons, etc.), a touch pad, pointing stick, or other cursor control device, a microphone for supplying voice commands, or any other suitable interface for controlling device10. Although shown schematically as being formed on the top face of electronic device10in the example ofFIG. 1, buttons such as button19and other user input interface devices may generally be formed on any suitable portion of electronic device10. For example, a button such as button19or other user interface control may be formed on the side of electronic device10. Buttons and other user interface controls can also be located on the top face, rear face, or other portion of device10. If desired, device10can be controlled remotely (e.g., using an infrared remote control, a radio-frequency remote control such as a Bluetooth remote control, etc.).

Electronic device10may have ports such as port20. Port20, which may sometimes be referred to as a dock connector, 30-pin data port connector, input-output port, or bus connector, may be used as an input-output port (e.g., when connecting device10to a mating dock connected to a computer or other electronic device). Device10may also have audio and video jacks that allow device10to interface with external components. Typical ports include power jacks to recharge a battery within device10or to operate device10from a direct current (DC) power supply, data ports to exchange data with external components such as a personal computer or peripheral, audio-visual jacks to drive headphones, a monitor, or other external audio-video equipment, a subscriber identity module (SIM) card port to authorize cellular telephone service, a memory card slot, etc. The functions of some or all of these devices and the internal circuitry of electronic device10can be controlled using input interface devices such as touch screen display16.

Components such as display16and other user input interface devices may cover most of the available surface area on the front face of device10(as shown in the example ofFIG. 1) or may occupy only a small portion of the front face of device10. Because electronic components such as display16often contain large amounts of metal (e.g., as radio-frequency shielding), the location of these components relative to the antenna elements in device10should generally be taken into consideration. Suitably chosen locations for the antenna elements and electronic components of the device will allow the antennas of electronic device10to function properly without being disrupted by the electronic components.

Examples of locations in which antenna structures may be located in device10include region18and region21. These are merely illustrative examples. Any suitable portion of device10may be used to house antenna structures for device10if desired.

If desired, electronic device10may be a portable electronic device such as a laptop or other portable computer. For example, electronic device10may be an ultraportable computer, a tablet computer, or other suitable portable computing device. An illustrative portable electronic device10of this type is shown inFIG. 2. As shown inFIG. 2, such portable electronic devices may have a screen16on a housing12. Antennas may be placed at any suitable location within device10. For example, antenna structures may be located along the right-hand edge of housing12(e.g., in region18ofFIG. 2) or may be located along the upper edge of housing12(e.g., in region21ofFIG. 2). These are merely illustrative examples. If desired, antenna structures may be placed along a left-hand edge, a bottom edge, or in portions of housing12other than a housing edge (e.g., in the middle of housing12or on an extendable structure that is connected to device10). An advantage of locating antenna structures along a device edge is that this generally allows the antennas to be placed in a location that is separated somewhat from conductive structures that might otherwise impede the operation of the antenna structures.

A schematic diagram of an embodiment of an illustrative portable electronic device is shown inFIG. 3. Portable device10may be a mobile telephone, a mobile telephone with media player capabilities, a handheld computer, a remote control, a game player, a global positioning system (GPS) device, a laptop computer, a tablet computer, an ultraportable computer, a combination of such devices, or any other suitable portable electronic device.

As shown inFIG. 3, device10may include storage34. Storage34may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., battery-based static or dynamic random-access-memory), etc.

Processing circuitry36may be used to control the operation of device10. Processing circuitry36may be based on a processor such as a microprocessor and other suitable integrated circuits. With one suitable arrangement, processing circuitry36and storage34are used to run software on device10, such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. Processing circuitry36and storage34may be used in implementing suitable communications protocols. Communications protocols that may be implemented using processing circuitry36and storage34include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling 3G data services such as UMTS, cellular telephone communications protocols, etc.

Input-output devices38may be used to allow data to be supplied to device10and to allow data to be provided from device10to external devices. Display screen16, button19, microphone port24, speaker port22, and dock connector port20are examples of input-output devices38.

Input-output devices38can include user input-output devices40such as buttons, touch screens, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. A user can control the operation of device10by supplying commands through user input devices40. Display and audio devices42may include liquid-crystal display (LCD) screens or other screens, light-emitting diodes (LEDs), and other components that present visual information and status data. Display and audio devices42may also include audio equipment such as speakers and other devices for creating sound. Display and audio devices42may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors.

Wireless communications devices44may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications).

Device10can communicate with external devices such as accessories46and computing equipment48, as shown by paths50. Paths50may include wired and wireless paths. Accessories46may include headphones (e.g., a wireless cellular headset or audio headphones) and audio-video equipment (e.g., wireless speakers, a game controller, or other equipment that receives and plays audio and video content), a peripheral such as a wireless printer or camera, etc.

Computing equipment48may be any suitable computer. With one suitable arrangement, computing equipment48is a computer that has an associated wireless access point (router) or an internal or external wireless card that establishes a wireless connection with device10. The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user's own personal computer, a peer device (e.g., another portable electronic device10), or any other suitable computing equipment.

The antenna structures and wireless communications devices of device10may support communications over any suitable wireless communications bands. For example, wireless communications devices44may be used to cover communications frequency bands such as the cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz, data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System), the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz (also sometimes referred to as wireless local area network or WLAN bands), the Bluetooth® band at 2.4 GHz, and the global positioning system (GPS) band at 1550 MHz. The 850 MHz band is sometimes referred to as the Global System for Mobile (GSM) communications band. The 900 MHz communications band is sometimes referred to as the Extended GSM (EGSM) band. The 1800 MHz band is sometimes referred to as the Digital Cellular System (DCS) band. The 1900 MHz band is sometimes referred to as the Personal Communications Service (PCS) band.

Device10can cover these communications bands and/or other suitable communications bands with proper configuration of the antenna structures in wireless communications circuitry44.

With one suitable arrangement, which is sometimes described herein as an example, the wireless communications circuitry of device10may have at least two antennas that are used in a diversity arrangement to handle communications in a first communications band. Antenna diversity arrangements use multiple antennas in parallel to obtain improved immunity to proximity effects and improved throughput. The antennas may operate in any suitable frequency band. For example, the antennas may be used to handle local area network (LAN) communications in a communications band that is centered at 2.4 GHz (e.g., the 2.4 GHz IEEE 802.11 frequency band sometimes referred to as Wi-Fi®). If desired, antenna diversity arrangements may be implemented using more than two antennas (e.g., three or more antennas). For clarity, examples with two antennas are sometimes described herein as an example.

At least one additional antenna may be placed in close proximity to the diversity scheme antennas. The additional antenna may, for example, be placed in the vicinity of the other antennas to conserve space in electronic device10. For example, the additional antenna may be placed between the other antennas. With one suitable arrangement, the antennas have resonating element structures with longitudinal axis that are all aligned.

The additional antenna may operate at the same frequency as the other antennas. For example, the additional antenna may operate at 2.4 GHz (e.g., to handle Bluetooth® communications). Because the antennas operate in the same communications band, care should be taken to avoid undesirable interference between the antennas.

The amount of isolation that is required between the antennas depends on the particular requirements of the system in which the antennas are being used. For example, the designers of portable electronic device10may require that the two diversity scheme antennas exhibit greater than 25 dB of isolation from each other and may require that the additional antenna exhibit greater than 15 dB of isolation relative to the other two antennas. These isolation criteria may be applied to antenna structures that exhibit a three-dimensional antenna efficiency of about 25-50%.

To achieve these levels of isolation, antenna isolation elements may be provided in the vicinity of the antennas. The structures that make up the antenna isolation elements may, for example, be interposed between the antenna resonating elements of the antennas. The antennas and the antenna isolation elements may share a common ground plane.

An illustrative antenna arrangement of this type is shown inFIG. 4. As shown inFIG. 4, wireless communications circuitry44may include first and second radio-frequency transceivers such as radio-frequency transceiver52and radio-frequency transceiver54(sometimes referred to as “radios”). Transceiver54may be, for example, a Bluetooth transceiver that is connected to antenna60by transmission line68. Transceiver52may be, for example, a Wi-Fi transceiver that is connected to antennas56and64by transmission lines70and72. Transmission lines68,70, and72may be any transmission lines suitable for carrying radio-frequency signals between radio-frequency transceivers and antennas. For example, transmission lines68,70, and72may be coaxial cable transmission lines, microstrip transmission lines, etc.

Transceiver52or other circuitry in device10may monitor the status of antennas56and64to implement an antenna diversity scheme. With this type of arrangement, transceiver52may use both antennas simultaneously or may opt to use primarily or exclusively antenna56or antenna64depending on which antenna has a higher associated signal strength or is less affected by proximity effects (e.g., from the close proximity of a user's hand or other part of a user's body), etc. Transceiver52may include coupling circuitry that routes radio-frequency signals to antenna56and/or antenna64from a transmitter in transceiver52during radio-frequency transmissions and that routes radio-frequency signals from antenna56and/or antenna64to a receiver in transceiver52during reception of radio-frequency signals. Transceiver54may include radio-frequency transmitter circuitry for transmitting radio-frequency signals and may include receiver circuitry for receiving radio-frequency signals.

During operation of device10, it may be desirable to use transceiver54and transceiver52at the same time. The ability to operate transceivers54and52asynchronously may allow, for example, a user to use a Bluetooth headset to use device10to make a voice-over-internet-protocol (VOIP) telephone call. Transceiver54may be used to establish a wireless Bluetooth link with the Bluetooth headset. At the same time, transceiver52may be used to establish an IEEE 802.11(n) Wi-Fi link with a wireless access point connected to the Internet. Because both links may be used simultaneously, both links may carry data traffic without interruption.

The IEEE 802.11(n) protocol is an example of a protocol that may use antenna diversity to improve performance. This type of arrangement uses two antennas (e.g., antennas56and64) to carry Wi-Fi traffic. In general, any suitable number of antennas such as antennas56and64may be used in an antenna diversity scheme. For example, there may be three or more antennas coupled to transceiver52. The use of an arrangement with two diversity antennas is described herein as an example. Moreover, the Bluetooth link or other communications link that is established between transceiver54and antenna60is merely illustrative. There may be more than one antenna60and there may be more than one associated transceiver54that is coupled to that antenna if desired.

As shown inFIG. 4, antennas56,60, and64may share a common ground plane (e.g., ground plane66). With this type of arrangement, each of antennas56,60, and64may have an associated antenna resonating element. These antenna resonating elements may be formed using inverted-F structures, planar inverted-F structures, L-shaped monopole structures, or any other suitable antenna resonating element configuration. The antenna resonating element portions of antennas56,60, and64are generally spaced somewhat above common ground66. Common ground66may be formed from conductive elements in device10such as housing12, printed circuit boards, conductive packages for integrated circuits in device10, conductive components that are electrically connected to printed circuit boards or other grounded elements, etc. In a typical arrangement, some or all of these grounded structures are substantially planar. Accordingly, common ground structure66is sometimes referred to as a ground plane and is sometimes depicted schematically as an ideal plane. In practice, however, some non-planar structures may protrude slightly from portions of the ground plane. To ensure good efficiency for antennas56,60, and64, sufficient clearance may be provided between such protruding conductive structures and the antenna resonating elements of antennas56,60, and64.

Antenna60is generally located between antennas56and64, as shown inFIG. 4. If there were an unlimited amount of space in device10, it might be possible to place antenna60at a remote location, thereby ensuring adequate isolation between antenna60and antennas56and64based on physical separation. In real-world configurations for device10, this type of layout may not be practical. Accordingly, antenna60may be located between antennas56and64. This may provide a compact layout arrangement that fits within the potentially tight confines of housing12.

Because the printed circuit board and other conductive elements of ground plane66are electrically connected to form a common ground plane structure for antennas56,60, and64, it may not be possible to create electrical gaps in ground plane66to help isolate antennas56,60, and64from each other. Particularly in situations such as these, it may be advantageous to use antenna isolation elements. As shown inFIG. 4, for example, radio-frequency isolation between antennas56,60, and64may be enhanced using antenna isolation elements58and62. Antenna isolation elements58and62may be formed from antenna resonating element structures that are similar to the antenna resonating element structures used in antennas56,60, and64. For example, antenna isolation elements58and62may be formed using inverted-F structures, planar inverted-F structures, L-shaped structures, etc. Unlike antennas56,60, and64, however, the antenna isolation elements58do not have antenna feed terminals that are coupled to transmission lines such as transmission lines68and70. Rather, antenna isolation elements58and62serve to provide enhanced levels of radio-frequency isolation between antennas56,60, and64. In effect, isolation elements58and62may serve as radio-frequency chokes that prevent undesirable near-field electromagnetic coupling between antennas56,60, and64at the frequency of interest (e.g., in the common communications frequency band of 2.4 GHz in this example).

For example, with antenna isolation elements58and62in place, antennas56and64may exhibit greater than 25 dB of isolation from each other, whereas antenna60may exhibit greater than 15 dB of isolation relative to antennas58and64. These isolation specifications may be achieved for antennas56,60, and64that exhibit three-dimensional antenna efficiencies of about 25-50% (as an example). Moreover, these isolation specification (or other suitable specifications) may be achieved when operating all antennas56,60, and64in the same frequency band (e.g., at 2.4 GHz or other suitable resonant frequency).

To enhance the capabilities of antennas56,60, and64, some or all of antennas56,60, and64may operate in multiple communications bands. For example, antennas56and64may be configured to handle communications at both 2.4 Hz and 5.1 GHz (e.g., to handle additional Wi-Fi bands). In this type of configuration, radio-frequency transceiver52(or an associated transceiver) may be used to convey signals at 5.1 GHz to and from antennas56and64over communications paths such as transmission lines70and72in addition to the 2.4 GHz signals that are being conveyed between the antennas and transceiver52. Antenna60may be a single band antenna or may be a multiband antenna.

In a typical configuration, the resonating element structures of antennas56,60, and64and of antenna isolation elements58and62may have lateral dimensions on the order of a quarter of a wavelength at each frequency of interest (e.g., on the order of a couple of centimeters for 2.4 GHz communications). Antennas56and64may be separated by about 14 centimeters (as an example). Antenna60may be located midway between antennas56and64. With one suitable arrangement, antennas56,60, and64and antenna isolation elements58and62are arranged in a line (i.e., along a common axis that is aligned with the longitudinal axis of each of the resonating elements in antennas56,60, and64and antenna isolation elements58and62). Collinear arrangements such as these are illustrative. Other configurations (e.g., with different antenna resonating element sizes and/or different spacings and relative positions for the antennas) may be used if desired.

An illustrative configuration for an antenna such as antenna56or64is shown inFIG. 5. This type of configuration may also be used for antenna60(e.g., when antenna60is a dual-band antenna).

As shown inFIG. 5, antenna74may have an antenna resonating element76and ground plane portion66. Together, antenna resonating element76and ground plane66make up the two poles in antenna74. Ground plane66is preferably shared by other antennas in device10as shown inFIG. 4. These other antennas are not shown inFIG. 5to avoid over-complicating the drawing.

Antenna resonating element76, ground plane66and the other antenna structures in device10(including the resonating element structures associated with isolation elements58and62) may be formed from any suitable conductive materials (e.g., copper, gold, metal alloys, other conductors, or combinations of such conductive materials). Such structures may be formed from stamped foils, from screen-printed structures, from conductive traces formed on flexible printed circuit substrates (so-called flex circuits) or using any other suitable arrangement.

In the example ofFIG. 5, antenna resonating element76has multiple branches formed by first arm78and second arm80. These branches each form a resonant structure with a different effective length. A longer length L1is associated with longer arm78of antenna resonating element76. A shorter length L2is associated with shorter arm80of antenna resonating element76. The length L1may be equal to about a quarter of a wavelength at a first operating frequency. The length L2may be equal to about a quarter of a wavelength at a second operating frequency. For example, the length L1may be equal to a quarter of a wavelength at 2.4 GHz and the length L2may be equal to a quarter of a wavelength at 5.1 GHz. As shown inFIG. 5, resonating element76may include a vertical portion94that extends parallel to vertical axis90. Vertical axis90is perpendicular to ground plane66. Resonating element76also generally includes horizontal portions such as arms78and80in theFIG. 5example.

The horizontal portions of antenna resonating element76run parallel to ground plane66. Antenna74ofFIG. 5has a longitudinal axis92that is defined by the main portions of antenna resonating element76(e.g., by arm78in the example ofFIG. 5). Arms such as arm78and arm80may run parallel to longitudinal axis92. With one suitable arrangement, antennas56,60, and64and antenna isolation elements58and62are substantially collinear with axis92and each other.

If desired, some or all of the antennas and isolation elements can be located off of axis92(e.g., by a small offset amount such as by a few millimeters or by a relatively larger distance such as centimeter or more), but in general, such off-axis locations may not be highly favored because locating isolation elements58and62off of the longitudinal axis that runs through antennas56,60, and64will generally tend to reduce the effectiveness of isolation elements58and62in isolating the antennas from each other. Locating antennas56,60, and64at off-axis positions also tends to increase the overall footprint for the antennas, which makes it more difficult to fit the desired antenna structures into a device with a compact form factor.

The antennas in device10may be fed directly using feed terminals that are connected to portions of the antenna or indirectly through near-field coupling arrangements. In the illustrative example ofFIG. 5, antenna74is fed using positive antenna feed terminal86and negative (ground) antenna feed terminal84. A transmission line such as coaxial cable82may be used to convey signals to and from feed terminals86and84. Transmission line center conductor88may be used to convey signals to and from positive antenna feed terminal86. The outer ground conductor of transmission line82is connected to terminal84. The outer ground conductor of transmission line82to terminal84. The antenna feed arrangement ofFIG. 5is merely illustrative. Any suitable feed arrangement may be used. For example, antenna feed terminals86and84may be located at other portions of antenna74(e.g., so that the positive terminal is coupled to long arm78or so that the horizontal position of the feed point is adjusted for impedance matching). Moreover, a tuning network (e.g., a circuit formed from capacitors, inductors, etc.) may be coupled to antenna74or may be used as part of a feed network.

The antennas and isolation elements of device10may have dielectric support structures. An example of this type of arrangement is shown inFIG. 6. As shown inFIG. 6, antenna74may have an antenna resonating element such as element76that is supported by a dielectric support structure such as dielectric support structure96. Resonating element76may be formed from conductive traces on a flex circuit substrate or other suitable conductive materials. Dielectric support structure96may be formed from plastic or other suitable dielectric materials. In the example ofFIG. 6, antenna74is being fed using a positive feed terminal86that is connected to antenna resonating element arm78. Antenna ground terminal84is connected to ground plane66. Arrangements of the type shown inFIG. 6may be used for antennas56and64(e.g., when antennas56and64are dual-band antennas). Arrangements of the type shown inFIG. 6may also be used for antenna60(e.g., when antenna60is a dual-band antenna). If one of arms78and80is omitted, antenna resonating element76will have an L-shape configuration. In this type of configuration, resonating element76may be used for a single-band antenna60. When feed terminals86and84are omitted, single-arm or multi-arm resonating elements such as element76ofFIG. 6may serve as antenna isolation elements58and62.

As shown inFIG. 7, it is not necessary for the longer arm of a resonating element (in either an antenna or an antenna isolation element) to be located farther from the ground plane than the shorter arm of the resonating element. In theFIG. 7example, shorter resonating element arm78in resonating element76is located farther from ground plane66than longer resonating element arm80.

Antenna feed terminals for antennas such as antenna74ofFIG. 7may be placed at any suitable location. For example, positive antenna feed terminal86may be connected to arm80and ground antenna feed terminal84may be connected to ground conductor66.

The bandwidth of an antenna such as the antenna ofFIG. 7is in part determined by the vertical position of its arms. Antennas with antenna resonating element arms that are located relatively farther from ground plane66tend to exhibit relatively more bandwidth than antennas with resonating element structures that are located near to ground plane66. An illustrative antenna resonating element configuration in which both antenna resonating element arms are located at substantially the same vertical distance from ground plane66(and which therefore both produce antenna resonances with maximum bandwidth) is shown inFIG. 8. As shown inFIG. 8, antenna74may have a longer arm such as long arm78that is aligned with longitudinal axis92and a shorter arm such as short arm80that lies perpendicular to arm78. Both arm78and arm80lie parallel to ground plane66.

Particularly in situations in which it is desirable to provide the higher-frequency band of a multi-band antenna with a maximized bandwidth (e.g., when handling the 5.1 GHz band of a 2.4 GHz/5.1 GHz dual-band Wi-Fi antenna), it may be advantageous to use an arrangement of the type shown inFIG. 8orFIG. 7, because these configurations for antenna resonating element76place shorter antenna resonating element arm80at a relatively large vertical position relative to ground plane66than would otherwise be possible. An advantage of theFIG. 8arrangement is that the enhanced vertical spacing associated with arm80is achieved without adversely affecting the vertical spacing associated with arm78.

A perspective view of an illustrative antenna configuration of the type that is shown schematically inFIG. 4is shown inFIG. 9. As shown inFIG. 9, antennas56,60, and64may be arranged in a line on common ground plane66(i.e., aligned in a collinear fashion with axis92). Each antenna may have a longitudinal axis defined by its longest arm. Each such longitudinal axis may, if desired, be aligned with axis92as shown inFIG. 9. Similarly, isolation elements58and62may be configured so that they each have a longitudinal axis that is aligned with axis92. Antennas56and64may be dual-band antennas each having two respective resonating element arms. Antenna60may be a single band antenna (as an example). Antenna60may be formed from an L-shaped resonating element, as shown inFIG. 9. Antenna isolation elements58and62may be formed from any suitable antenna resonating element structures. For example, antenna isolation elements58and62may be formed from L-shaped resonating elements, as shown inFIG. 9.

To ensure that isolation elements58and62provide satisfactory radio-frequency isolation for antennas56,60, and64, the resonating element structures that make up antenna isolation elements58and62may be tuned to resonate at the frequency at which isolation is desired. For example, if antennas56and64resonate at 2.4 GHz and 5.1 GHz and antenna60resonates at 2.4 GHz, and if isolation is desired at 2.4 GHz, antenna isolation elements58and62may have L-shaped resonating elements of length L, where L is equal to a quarter of a wavelength at 2.4 GHz.

As shown inFIG. 9, the antenna isolation elements may have termination points such as termination points98. L-shaped conductive elements such as elements100may have lengths L that are selected to provide isolation between antennas56and64and between antenna60and antennas56and64. Antennas56and64may have antenna resonating elements104that are connected to ground plane66at points102. Antenna60may have an antenna resonating element such as resonating element108that is connected to ground plane66at point106.

In the example ofFIG. 9, resonating elements104and108of antennas56,60, and64extend upwards and to the right (in the orientation shown inFIG. 9). Similarly, antenna isolation elements58and62have resonating elements100that extend upwards and to the right from points98. This configuration is merely illustrative. Antennas56,60, and64and antenna isolation elements58and62may extend upwards and to the left and/or upwards and to the right in any suitable combination (e.g., all facing to the right, all facing to the left, the antennas facing to the right and the isolation elements facing to the left, the antennas facing to the left and the isolation elements facing to the right, some of the antennas facing to the right and some to the left, some of the isolation elements facing to the right and some to the left, or combinations of these arrangements).

FIG. 10shows an illustrative antenna configuration in which antennas56,60, and64have resonating elements that extend upwards and to the right (i.e., elements that face to the right) and in which isolation elements58and62face to the left. In this type of configuration, points98are located in the vicinity of points106and102.

An alternative configuration for the antennas of device10is shown inFIG. 11. In the arrangement ofFIG. 11, antenna isolation elements58and62have resonating elements with perpendicular conductive portions such as portion112of element58. Resonating element100is connected to ground conductive structure66at point98. Vertical portion108extends vertically in vertical direction110, perpendicular to the plane of ground conductor66. Horizontal perpendicular section112extends in direction114. Direction114is parallel to ground plane66and is perpendicular to vertical direction110and longitudinal axis92. Horizontal portion116of resonating element100extends parallel to longitudinal axis92, perpendicular to horizontal direction114, and perpendicular to vertical direction110. If desired, antennas56,60, and64may have bends (e.g., perpendicular sections such as perpendicular portion112and/or U-shaped portions or serpentine paths). Isolation elements58and62may also have bends of different shapes and orientations. The arrangement ofFIG. 11is merely illustrative.

If desired, the antenna isolation elements may be located at positions that are offset somewhat from axis92.FIG. 12shows potential offset positions in which isolation element58may be placed relative to antenna56.

Isolation element58may be located so that it contacts ground plane66at point118. In this type of situation, the resonant element of isolation element58will be positioned where indicated by solid line120. As indicated by dashed line122, in this configuration, the resonating element of antenna56is collinear with the resonating element of antenna isolation element58. Because point118lies on line122, there is no lateral offset between the location of resonating element58and the longitudinal axis of the antennas in device10(e.g., antenna56and the antennas that are not shown inFIG. 12).

If desired, isolation element58may be located so that it contacts ground plane66at point132. In this configuration, antenna isolation element58will be positioned where indicated by dashed line134. Contact point132is offset from dashed line122by lateral offset distance136. Provided that lateral offset136is not too large, antenna isolation element58may still provide sufficient isolation for the antennas of device10. For example, a lateral offset of a fraction of a millimeter or a few millimeters may be acceptable for antennas that are a few centimeters in length.

Isolation element58may be provided with both a lateral and longitudinal offset with respect to antenna56. This type of configuration is illustrated by dashed line126. When the resonating element of antenna isolation element58is aligned with the position indicated by dashed line126, the resonating element contacts ground plane66at point124. As shown inFIG. 12, point124is laterally offset from dashed line122by lateral offset distance128and is longitudinally offset from point118(which is substantially vertically aligned with the tip of the longer resonating element arm of antenna56) by longitudinal offset distance130. Provided that the magnitudes of the longitudinal offset and lateral offset are not too large (e.g., several millimeters as an example), isolation element58may provide sufficient radio-frequency isolation for the antennas of device10.

One isolation element, two isolation elements, or more than two isolation elements (e.g., in arrangements with four or more antennas) may be offset as shown inFIG. 12. If desired, mixed arrangements may be used (e.g., in which some isolation elements are laterally and/or longitudinally offset and in which some isolation elements are not offset). Moreover, antennas such as antennas56,60, and64may be longitudinally and/or laterally offset with respect to each other and with respect to the isolation elements.

The arms of the antenna isolation elements and/or antennas in device10may also be oriented at non-zero angles with respect to longitudinal axis92if desired. An example of this type of arrangement is shown inFIG. 13. As shown inFIG. 13, antenna56has a longitudinal axis92. The other antennas of device10(e.g., antennas60and64) may be aligned with axis92. Isolation elements such as isolation element58may be interposed between adjacent antennas to provide enhanced levels of radio-frequency signal isolation. Antenna isolation element58may have an L-shaped resonating element conductor. Arm138of the resonating element may be oriented at a non-zero angle α with respect to axis92. Any suitable angle α may be used. For example, isolation element58may have a resonating element arm138that is oriented at an angle α of about 1-10° with respect to axis92(as an example).

Non-zero resonating element arm orientations of the type illustrated by the orientation of isolation element arm138ofFIG. 13may be used for antenna resonating elements and/or isolation element resonating elements. None of the elements, one or more of the elements, or all of the elements may be angled with respect to axis92if desired. Moreover, angled resonating element arrangements such as these may be used in configurations in which the resonating elements are longitudinally and/or laterally offset from axis92.

If desired, one or more of the antenna isolation elements may be implemented using multiple resonating element structures. As shown inFIG. 14, for example, antenna isolation element56may be implemented using three L-shaped conductive resonating elements: resonating element140, resonating element142, and resonating element144. Each of these conductive structures may be oriented at a zero angle with respect to longitudinal axis92of antennas56and60or at a non-zero angle with respect to longitudinal axis92of antennas56and60(as described in connection withFIG. 13). Lateral and longitudinal offsets may be used in positioning resonating elements140,142, and144as described in connection withFIG. 12. Moreover, different numbers of resonating element structures may be used. For example, antenna isolation element58may have more than three L-shaped conductive structures, or may have two L-shaped conductive structures.

The conductors of antenna isolation element58may have any suitable shape (e.g., L-shaped, multi-branched, shapes with bends, shapes with U-shaped and/or serpentine layouts, structures with combinations of these configurations, etc.). One of the antenna isolation elements may use multiple conductive structures, two of the antenna isolation elements may use multiple conductive structures, or (in arrangements using more than three antennas) three or more of the antenna isolation elements may use multiple conductive structures. The conductive structures in a given antenna isolation element may be substantially similar in shape or may have different shapes and sizes.

Antenna isolation elements58and62may be formed using multi-arm configurations. When the antenna isolation elements have multiple arms, the frequency response of the antenna isolation elements may be broadened to help enhance radio-frequency signal isolation effectiveness. An illustrative configuration in which antenna isolation element58is provided with multiple arms is shown inFIG. 15. As shown inFIG. 15, antenna isolation element58may have a first arm such as arm146and a second arm such as arm148. Additional arms may be used if desired.

Arm146may be longer than arm148(as an example). Arm146may be oriented so that it is parallel to longitudinal axis92of antennas such as antennas56and60. Arm148may be oriented perpendicular to axis92and parallel to ground plane66.

Additional suitable multi-arm configurations for the antenna isolation elements are shown inFIG. 16. In the example ofFIG. 16, antenna isolation element58has two arms. Arm152is longer than arm150. Both arm150and arm152lie parallel to axis92(which is aligned with the longitudinal axis of each antenna and isolation structure in theFIG. 16arrangement). Antenna isolation element62is formed from multiple free-standing structures. One resonating element structure in antenna isolation element62is formed from L-shaped conductive strip156. Another resonating element structure in antenna isolation element62is formed from smaller L-shaped conductive strip160. As shown inFIG. 16, arm158of resonating element156may be larger than arm162of element160. If desired, structures such as resonating element160may be laterally or longitudinally offset, so that their attachment points to ground plane66are shifted with respect to the position shown for element160. For example, the position of a resonating element such as resonating element160may be longitudinally shifted so that it is aligned with the position indicated by dashed line164.

In general, the antenna isolation elements may have one or more individual resonating element structures. The structures may have the same shapes and sizes or may have different shapes and sizes. The structures may have one arm (e.g., in an L-shaped conductive strip) or may have multiple arms. The structures may be aligned with the longitudinal axis of the antenna structures or may be oriented at a non-zero angle. Lateral and longitudinal offsets may be used in positioning the resonating element structures. Combinations of these arrangements may be used in forming antenna isolation elements.

Antennas such as antennas56,60, and64may also use these types of resonating element structures. For example, antenna56may be formed from two closely spaced resonating elements such as elements156and160ofFIG. 16, provided that these elements are fed using appropriate antenna feed terminals such as feed terminals86and84ofFIG. 5. In this type of arrangement, one of the antenna resonating elements may be directly fed using antenna feed terminals that are connected to the resonating element arm and ground plane as shown for arm80of antenna74inFIG. 5. The other antenna resonating element may be indirectly fed through near-field electromagnetic coupling (as an example).