HK1159328B - Bezel gap antennas - Google Patents

Description

Frame slot antenna

Technical Field

The present invention relates generally to wireless communication circuits, and more particularly to electronic devices having wireless communication circuits.

Background

Electronic devices such as handheld 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 a variety of such devices.

Devices such as these are often provided with wireless communication functionality. For example, an electronic device may use long-range wireless communication circuitry, such as cellular telephone circuitry, to communicate using cellular telephone bands of 850MHz, 900MHz, 1800MHz, and 1900MHz (e.g., the predominant global system for mobile communications or GSM cellular telephone bands). Long-range wireless communications circuitry may also handle the 2100MHz band. The electronic device may use the short-range wireless communication link to handle communications with nearby devices. For example, the electronic device may use signals at 2.4GHz and 5GHzAt (IEEE 802.11) frequency band and 2.4GHzFrequency bands.

To meet consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communication circuits, such as antenna components, with compact structures. Meanwhile, it may be desirable to include conductive structures, such as metal device case components, in the electronic device. Because conductive components can affect radio frequency performance, special care must be taken when incorporating the antenna into an electronic device that includes conductive structures.

It is therefore desirable to provide improved wireless communication circuitry for wireless electronic devices.

Disclosure of Invention

An electronic device including an antenna structure is provided. The antenna may be configured to operate in first and second communication bands. The electronic device may include radio-frequency transceiver circuitry coupled to the antenna using a transmission line. The transmission line may have a positive conductor and a ground conductor. The antenna may have a positive antenna feed terminal and a ground antenna feed terminal coupled to the positive conductor and the ground conductor of the transmission line, respectively.

The electronic device may have a rectangular outer perimeter. The rectangular display may be mounted on the front face of the electronic device. The electronic device may have a back side formed by a plastic housing part. The conductive sidewall structure may surround the periphery of the electronic device housing and the display. The conductive sidewall structure may serve as a bezel for the display.

The bezel may include at least one slot. The gap may be filled with a solid dielectric such as plastic. The antenna may be formed by a frame portion including the slot and a portion of the ground plane. To avoid being too sensitive to touch events, the antenna may be fed using a feeding arrangement that reduces the electric field concentration near the slot. An impedance matching network may be formed that provides satisfactory operation in both the first and second frequency bands.

The impedance matching network may include an inductive element formed in parallel with the antenna feed terminal and a capacitive element formed in series with one of the antenna feed terminals. The inductive element may be formed by a transmission line inductive structure bridging the antenna feed terminals. The capacitive element may be formed by a capacitor sandwiched (interpose) in the positive feed path of the antenna. The capacitor may be connected, for example, between the positive ground conductor of the transmission line and the positive antenna feed terminal.

Other features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.

Drawings

Fig. 1 is a perspective view of an exemplary electronic device having wireless communication circuitry in accordance with an embodiment of the present invention.

Fig. 2 is a schematic diagram of an exemplary electronic device having wireless communication circuitry in accordance with an embodiment of the present invention.

Fig. 3 is a cross-sectional end view of an exemplary electronic device having wireless communication circuitry in accordance with an embodiment of the present invention.

Fig. 4 is a schematic diagram of an exemplary antenna in accordance with an embodiment of the present invention.

Fig. 5 is a schematic diagram of an exemplary series-fed loop antenna (series-fed loop antenna) that may be used in an electronic device according to an embodiment of the invention.

Fig. 6 is a diagram illustrating how an electronic device antenna may be configured to appear to cover multiple communication bands, according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of an exemplary parallel-fed loop antenna (parallel-fed loop antenna) that may be used in an electronic device according to an embodiment of the invention.

Fig. 8 is a schematic diagram of an exemplary shunt-fed loop antenna with an inductor inserted in a loop (loop) according to an embodiment of the present invention.

Fig. 9 is a schematic diagram of an exemplary shunt-fed loop antenna having an inductive transmission line structure, in accordance with an embodiment of the present invention.

Fig. 10 is a schematic diagram of an exemplary shunt-fed loop antenna having an inductive transmission line structure and a series capacitive element, in accordance with an embodiment of the present invention.

FIG. 11 is a Smith chart illustrating the performance of various electronic device loop antennas according to embodiments of the invention.

Detailed Description

The electronic device may be provided with wireless communication circuitry. The wireless communication circuit may be used to support wireless communications in a plurality of wireless communication bands. The wireless communication circuitry may include one or more antennas.

The antenna may comprise a loop antenna. If desired, the conductive structure of the loop antenna may be formed from conductive electronics structures. The conductive electronic device structure may include a conductive shell structure. The shell structure may include a conductive bezel. The slot structure may be formed in the conductive bezel. The antennas may be shunt fed using a structure that helps minimize the sensitivity of the antennas to contact with a user's hand or other external objects.

Any suitable electronic device may be provided with wireless circuitry including a loop antenna structure. For example, loop antenna structures may be used in electronic devices such as desktop computers, gaming machines, routers, laptop computers, and the like. With one suitable structure, the loop antenna structure is disposed in a relatively compact electronic device, such as a portable electronic device, in which interior space is relatively valuable.

An exemplary portable electronic device according to an embodiment of the present invention is shown in fig. 1. A portable electronic device such as the exemplary portable electronic device 10 may be a laptop computer or a small portable computer such as an ultra-portable computer, a netbook computer, and a tablet computer. The portable electronic device may also be a smaller device. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, earphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic device is a handheld electronic device such as a cellular telephone.

Space is at a premium in portable electronic devices. Conductive structures are also typically present, which present challenges to effective antenna operation. For example, the conductive shell structure may surround a portion of the periphery or the entire periphery of the portable electronic device housing.

In such portable electronic device case arrangements, it may be particularly advantageous to use a loop-type antenna design that covers the communication band of interest. Thus, the use of portable devices such as handheld devices is sometimes described herein as an example, although any suitable electronic device having a loop antenna structure may be provided if desired.

The handheld device may be, for example, a cellular telephone, a media player with wireless communication capability, a handheld computer (also sometimes referred to as a personal digital assistant), a remote control, a Global Positioning System (GPS) device, and a handheld gaming device. Handheld and other portable devices may include the functionality of a number of conventional devices, if desired. Examples of multifunction devices include: a cellular telephone including media player functionality; a game device including a wireless communication function; a cellular telephone including gaming and email functions; and handheld devices capable of receiving e-mail, supporting mobile telephone calls, and supporting web browsing. These are merely illustrative examples. The device 10 of fig. 1 may be any suitable portable or handheld electronic device.

The device 10 includes a housing 12 and includes at least one antenna for handling wireless communications. The housing 12, sometimes referred to as a shell, may be formed of any suitable material, including: plastic, glass, ceramic, composite, metal, or other suitable material, or a combination of these materials. In some cases, portions of the housing 12 may be formed of a dielectric or other low conductivity material so that the operation of the conductive antenna elements located in the housing 12 is not disturbed. In other cases, the housing 12 may be formed from a metal element.

Device 10 may have a display such as display 14 if desired. The display 14 may be, for example, a touch screen incorporating capacitive touch electrodes. Display 14 may include image pixels formed from Light Emitting Diodes (LEDs), organic LEDs (oleds), plasma cells, electronic ink elements, Liquid Crystal Display (LCD) components, or other suitable image pixel structures. A cover glass (cover glass) member may cover the surface of display 14. A button, such as button 19, may pass through an opening in the glass.

The housing 12 may include a sidewall structure such as sidewall structure 16. Structure 16 may be implemented using a conductive material. For example, structure 16 may be implemented with a conductive loop member that substantially surrounds a rectangular periphery of display 14. The structure 16 may be formed of, for example, stainless steel, aluminum, or other suitable material. One, two, or more than two separate structures may be used to form structure 16. Structure 16 may serve as a bezel to secure display 14 to the front (top) surface of device 10. The structure 16 is therefore sometimes referred to herein as a bezel structure 16 or bezel 16. Bezel 16 surrounds the rectangular perimeter of device 10 and display 14.

Bezel 16 may have a thickness (dimension TT) of about 0.1mm to 3mm (as an example). The sidewall portions of bezel 16 may be substantially vertical (parallel to vertical axis V). Parallel to axis V, bezel 16 may have a dimension TZ of about 1mm to 2cm (as an example). The aspect ratio R (i.e., the ratio of TZ to TT) of the bezel 16 is typically greater than 1 (i.e., R may be greater than or equal to 1, greater than or equal to 2, greater than or equal to 4, greater than or equal to 10, etc.).

The rims 16 do not necessarily have the same cross-section. For example, if desired, an upper portion of bezel 16 may have an inwardly projecting flange (lip) that helps hold display 14 in place. The lower portion of the bezel 16 may also have an enlarged flange (e.g., in the plane of the rear surface of the device 10), if desired. In the example of fig. 1, bezel 16 has substantially straight vertical sidewalls. This is merely exemplary. The side walls of the bezel 16 may be curved or may have any other suitable shape.

The display 14 includes conductive structures such as capacitive electrode arrays, conductive lines for addressing pixel elements, drive circuitry, and the like. These conductive structures tend to block radio frequency signals. It may therefore be desirable to form part or all of the rear planar surface of the device from a dielectric material such as plastic.

Portions of the rim 16 may be provided with a slit structure. For example, the bezel 16 may be provided with one or more slits, such as slit 18, as shown in FIG. 1. Slot 18 is disposed along the outer perimeter of the housing of device 10 and display 12, and is therefore sometimes referred to as a peripheral slot. The slot 18 divides the bezel 16 (i.e., there are generally no conductive portions of the bezel 16 in the slot 18).

As shown in fig. 1, the slot 18 may be filled with a dielectric. For example, the gap 18 may be filled with air. To help provide the device 10 with a smooth, uninterrupted appearance and to ensure that the bezel 16 is aesthetically appealing, the gap 18 may be filled with a solid (non-air) dielectric, such as plastic. Bezel 16 and slots such as slot 18 (and their associated plastic filled structures) may form part of one or more antennas in device 10. For example, the bezel 16 and portions of the slots, such as slot 18, along with the internal conductive structure form one or more loop antennas. The internal conductive structure may include a printed circuit board structure, a frame member or other support structure, or other suitable conductive structure.

In a typical case, the device 10 may have an upper antenna and a lower antenna (as an example). The upper antenna may be formed, for example, at the upper end of the device 10 in the region 22. The lower antenna may be formed, for example, at the lower end of the device 10 in the region 20.

The lower antenna may be formed, for example, in part by the portion of the bezel 16 near the slot 18.

The antennas in device 10 may be used to support any communications band of interest. For example, device 10 may include a wireless communication interface for supporting local area network communications, voice and data cellular telephone communications, Global Positioning System (GPS) communications, wireless communication,Antenna structures for communications, etc. E.g. in the area 20 of the device 10The lower antenna may be used to handle voice and data communications in one or more cellular telephone bands.

A schematic diagram of an exemplary electronic device is shown in fig. 2. The device 10 of fig. 2 may be a portable computer, such as: a portable tablet computer, a mobile phone with media player functionality, a handheld computer, a remote control, a game console, a Global Positioning System (GPS) device, a combination of these devices, or any other suitable portable electronic device.

As shown in fig. 2, handheld device 10 may include storage and processing circuitry 28. The storage and processing circuitry 28 may include storage devices such as hard disk drive storage devices, non-volatile memory (e.g., flash memory or other electrically programmable read-only memory used to form solid state drives), volatile memory (e.g., static or dynamic random access memory), and so forth. Processing circuitry in storage and processing circuitry 28 may be used to control the operation of device 10. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc.

The storage and processing circuitry 28 may be used to run software on the device 10, such as an internet browsing application, a Voice Over Internet Protocol (VOIP) telephone call application, an email application, a media playback application, operating system functions, and so forth. To support interaction with external devices, the storage and processing circuitry 28 may be used to execute communication protocols. Communication protocols that may be implemented using storage and processing circuitry 28 include internet protocols, wireless local area network protocols (e.g., IEEE802.11 protocols-sometimes referred to as IEEE802.11 protocols)) Protocols for other short-range wireless communication links (e.g. for short-range wireless communicationProtocols), cellular telephone protocols, etc.

Input-output circuitry 30 may be used to allow data to be provided to device 10 and to allow data to be provided from device 10 to external devices. Input-output devices 32, such as touch screens and other user interfaces, are examples of the input-output circuitry 30. Input-output devices 32 also include user input-output devices such as buttons, joysticks, click wheels, scroll wheels, touch pads, keypads, keyboards, microphones, cameras, etc. A user may be able to provide commands through these user input devices to control the operation of device 10. Display and audio devices, such as display 14 (FIG. 1) and other components that present visual information and status data, may be included in device 32. The display and audio components in the input-output device 32 may also include audio devices such as speakers and other devices for producing sound. If desired, the input-output devices 32 may include audio-video interface devices such as jacks and other connectors for external headphones and monitors.

Wireless communication circuitry 34 may include Radio Frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low noise input amplifiers, passive RF components, one or more antennas, and other circuitry for processing RF wireless signals. Wireless signals may also be transmitted using light (e.g., using infrared communication). The wireless communication circuitry 34 may include radio-frequency transceiver circuitry for handling multiple radio-frequency communication bands. For example, circuitry 34 may include transceiver circuitry 36 and 38. Transceiver circuitry 36 may process for2.4GHz and 5GHz bands for (IEEE 802.11) communications, and can handle 2.4GHzA communication frequency band. The circuitry 34 may use cellular telephone transceiver circuitry 38 for handling wireless communications in cellular telephone bands (e.g., GSM bands of 850MHz, 900MHz, 1800MHz, and 1900 MHz) and in a 2100MHz data band (as an example). The wireless communication circuitry 34 may include circuitry for other short-range and long-range wireless links, if desired. For example, wireless communicationThe link 34 may include a Global Positioning System (GPS) receiving device, radio circuitry for receiving radio and television signals, paging circuitry, and the like. In thatAndin links, as well as other short-range wireless links, wireless signals are typically used to communicate data over tens or hundreds of feet. In cellular telephone links and other long range links, wireless signals are typically used to communicate data over a range of thousands of feet or miles.

The wireless communication circuit 34 may include an antenna 40. Antenna 40 may be formed using any suitable antenna type. For example, antenna 40 may include an antenna having a resonating element formed from a loop antenna structure, a patch antenna structure, an inverted-F antenna structure, a slot antenna structure, a planar inverted-F antenna structure, a helical antenna structure, a hybrid of these designs, and so forth. Different types of antennas may be used for different frequency bands and combinations of frequency bands. For example, one type of antenna may be used to form a local wireless link antenna, while another type of antenna may be used to form a remote wireless link.

Using one suitable arrangement, sometimes described herein as an example, the lower antenna in device 10 (i.e., antenna 40 located in region 20 of device 10 of fig. 1) may be formed using a loop antenna design. When a user holds device 10, the user's fingers may contact the exterior of device 10. For example, a user may touch the touch device 10 in the area 20. To ensure that the antenna performance is not overly sensitive to the presence or absence of user touch or other external object contact, the loop antenna may be fed using an arrangement that does not overly concentrate the electric field near the slot 18.

A cross-sectional side view of the apparatus 10 of fig. 1, taken along line 24-24 of fig. 1 and viewed from direction 26, is shown in fig. 3. As shown in FIG. 3, display 14 may be mounted to a front surface of device 10 using bezel 16. The housing 12 may include side walls formed by the bezel 16 and one or more rear walls formed by, for example, a flat rear housing structure 42. Structure 42 may be formed of a dielectric such as plastic or other suitable material. Fasteners (snap), clips, screws, adhesives, and other structures may be used to attach bezel 16 to display 14 and rear housing wall structure 42.

The device 10 may include a printed circuit board such as the printed circuit board 46. Printed circuit board 46 and other printed circuit boards in device 10 may be formed from a rigid printed circuit board material (e.g., fiberglass-filled epoxy) or a sheet of flexible material such as a polymer. A flexible printed circuit board ("flex circuit") may be formed, for example, from a polyimide flex sheet.

The printed circuit board 46 may include interconnects such as interconnect 48. The interconnects 48 may be formed from conductive traces (traces), such as gold plated copper or other metal traces. Connectors such as connector 50 may be connected to interconnect 48 using solder or conductive adhesive (as examples). Integrated circuits, discrete components such as resistors, capacitors, and inductors, and other electronic components may be mounted to printed circuit board 46.

The antenna 40 may have an antenna feed terminal. For example, antenna 40 may have a positive antenna feed terminal, such as positive antenna feed terminal 58, and a ground antenna feed terminal, such as ground antenna feed terminal 54. In the exemplary arrangement of fig. 3, a transmission line path such as a coaxial cable 52 may be coupled between the antenna feed formed by terminals 58 and 54 and the transceiver circuitry in component 44 through connector 50 and interconnect 48. The components 44 may include one or more integrated circuits that implement the transceiver circuits 36 and 38 of fig. 2. The connector 50 may be, for example, a coaxial cable connector that connects to the printed circuit board 46. The cable 52 may be a coaxial cable or other transmission line. The terminal 58 may be coupled to the coaxial cable center connector 56. The terminal 54 may be connected to a ground conductor (e.g., a conductive outer braid conductor) in the cable 52. Other arrangements may be used to couple the transceiver in device 10 to antenna 40, if desired. The arrangement of fig. 3 is merely exemplary.

As best shown in the cross-sectional view of fig. 3, the side walls of the housing 12 formed by the rim 16 may be relatively tall. At the same time, the amount of area available for forming an antenna in the region 20 of the lower end of the device 10 may be limited, particularly in compact devices. The compact size desired for forming an antenna may make it difficult to form a slot antenna shape of sufficient size to resonate in a desired communication band. The shape of the bezel 16 may tend to reduce the efficiency of conventional planar inverted-F antennas. Such challenges can be addressed using a loop design of antenna 40, if desired.

The antenna arrangement of fig. 4 is taken as an example. As shown in fig. 4, antenna 40 may be formed in region 20 of device 10. As described in connection with fig. 1, the region 20 may be located at the lower end of the apparatus 10. The conductive areas 68, sometimes referred to as ground planes or ground plane elements, may be formed from one or more conductive structures (e.g., planar conductive traces on the printed circuit board 46, internal structural elements in the device 10, electronic components 44 on the board 46, radio frequency shields mounted on the board 46, etc.). Conductive region 68 in region 66 is sometimes referred to as forming a "ground region" for antenna 40. The conductive structure of fig. 4 may be formed by the bezel 16. Region 70 is sometimes referred to as a ground plane extension. A slot 18 may be formed in the conductive bezel portion (as shown in fig. 1).

The ground plane extension 70 (i.e., the portion of the bezel 16) and the portion of the ground region 68 along the edge 76 of the region 68 form a conductive loop around the opening 72. The opening 72 may be formed of air, plastic, or other solid dielectric. The profile of the opening 72 may be curved, may have more than 4 straight segments, and/or may be defined by the profile of the conductive member, if desired. The rectangular dielectric region 72 in fig. 4 is merely exemplary.

If desired, the conductive structure of fig. 4 may be fed by coupling radio-frequency transceiver 60 across a ground antenna feed terminal 62 and a positive antenna feed terminal 64. As shown in fig. 4, in this type of arrangement, the feed portion of antenna 40 is not located in the vicinity of slot 18 (i.e., feed terminals 62 and 64 are located to the left of the transverse center dividing line 74 of opening 72, while slot 18 is located to the right of dividing line 74 along the right-hand side of device 10). While this type of arrangement may be satisfactory in some situations, an antenna feed arrangement that positions the antenna feed terminal at the location of ends 62 and 64 of fig. 4 tends to strengthen the electric field strength of the radio frequency antenna signal near slot 18. If a user moves a finger 80 in direction 78 to just place an external object such as finger 80 in the vicinity of slot 18 (e.g., when grasping device 10 in the user's hand), the presence of the user's finger may interfere with the operation of antenna 40.

To ensure that antenna 40 is not overly sensitive to touch (i.e., to reduce the sensitivity of antenna 40 to touch events involving the hand of a user of device 10 and other external objects), antenna 40 may be fed using antenna feed terminals (e.g., as shown by positive antenna feed terminal 58 and ground antenna feed terminal 54 in the example of fig. 4) located near slot 18. When the antenna feed portion is located on the right side of the line 74, more specifically, when the antenna feed portion is close to the slot 18, the electric field generated at the slot 18 tends to decrease. This helps to minimize the sensitivity of antenna 40 to the presence of the user's hand, ensuring satisfactory operation regardless of whether external objects are in contact with device 10 near slot 18.

In the arrangement of fig. 4, the antenna 40 is series fed. A schematic diagram of a series fed loop antenna of the type shown in figure 4 is shown in figure 5. As shown in fig. 5, the series fed loop antenna 82 may have a loop conductive path, such as loop 84. A transmission line made up of a positive transmission line conductor 86 and a ground transmission line conductor 88 may be coupled to the antenna feed terminals 58 and 54, respectively.

Efficient use of a series fed feed arrangement of the type shown in figure 5 can be challenging. For example, it may be desirable to operate the loop antenna in the lower frequency band covering 850MHz and 900MHz GSM sub-bands and the upper frequency band covering 1800MHz and 1900MHz GSM sub-bands and 2100MHz data sub-bands. This type of arrangement may be considered a dual band arrangement (e.g., 850/900 for the first band, and 1800/1900/2100 for the second band), or may be considered to have 5 bands (850, 900, 1800, 1900, and 2100). In a multi-band arrangement such as this, a series fed antenna such as the loop antenna 82 of fig. 5 may exhibit substantially better impedance matching in the high frequency communication band than in the low frequency communication band.

The Standing Wave Ratio (SWR) versus frequency curve shown in fig. 6 illustrates this effect. As shown in fig. 6, the SWR curve 90 may exhibit a satisfactory resonance peak (peak 94) at the high-band frequency f2 (e.g., to cover sub-bands of 1800MHz, 1900MHz, and 2100 MHz). However, when the antenna 40 is series fed, the SWR curve 90 may exhibit relatively poor performance in a low frequency band centered at the frequency f 1. For example, the SWR curve 90 for the series fed loop antenna 82 of fig. 5 may be characterized by a weak resonant peak 96. As demonstrated by this example, the series fed loop antenna may provide satisfactory impedance matching for the transmission line 52 (fig. 3) in the higher frequency band of f2, but may not provide satisfactory impedance matching for the transmission line 52 (fig. 3) in the lower frequency band f 1.

A more satisfactory level of performance (represented by the low band resonant peak 92) can be achieved using a shunt feed arrangement with appropriate impedance matching characteristics.

An exemplary shunt-fed loop antenna is schematically illustrated in fig. 7. As shown in fig. 7, the shunt loop antenna 90 may have a conductor loop such as loop 92. The ring 92 in the example of fig. 7 is shown as circular. This is merely exemplary. The ring 92 can have other shapes (e.g., a rectangular shape, a shape with curved and straight sides, a shape with irregular boundaries, etc.) if desired. The transmission line TL may include a positive signal conductor 94 and a ground signal conductor 96. Paths 94 and 96 may be included in coaxial cables, in flexible circuits, in microstrip transmission lines on rigid printed circuit boards, and so forth. The transmission line TL may be coupled to the feed portion of the antenna 90 using the positive antenna feed terminal 58 and the ground antenna feed terminal 54. Electrical element 98 may bridge terminals 58 and 54, thereby "closing" the loop formed by path 92. When the ring is closed in this manner, the element 98 is sandwiched in the conductive path forming the ring 92. The impedance of a shunt-fed loop antenna, such as the loop antenna 90 of fig. 7, may be adjusted by appropriate selection of the element 98 and other circuitry (if desired), for example a capacitor or other element sandwiched in one of the feed lines, such as the line 94 or the line 96.

The element 98 may be formed from one or more electrical components. Components that may be used as all or part of element 98 include resistors, inductors, and capacitors. The desired resistance, inductance, and capacitance for the element 98 may be formed using an integrated circuit, using discrete components, and/or using dielectric and conductive structures that are not discrete components or part of an integrated circuit. For example, a resistance may be formed using a thin wire of resistive metal alloy, a capacitance may be formed by bringing two conductive plates close to each other and separated by a dielectric, and an inductance may be formed by creating a conductive path on a printed circuit board. These types of structures may be referred to as resistors, capacitors, and/or inductors, or may be referred to as capacitive, resistive, and/or inductive antenna feed structures.

An exemplary configuration of antenna 40 is shown in fig. 8, where component 98 in the schematic of fig. 7 has been implemented using an inductor. As shown in fig. 8, ring 92 (fig. 7) may be implemented using conductive region 70 and the conductive portion of region 68 along edge 76 of opening 72. The antenna 40 of fig. 8 may be fed using a positive antenna feed terminal 58 and a ground antenna feed terminal 54. Terminals 54 and 58 may be located near slot 18 to reduce electric field concentrations in slot 18 and thereby reduce the sensitivity of antenna 40 to touch events.

The presence of the inductor 98 may at least partially assist in matching the impedance of the transmission line 52 with the antenna 40. If desired, the inductor 98 may be formed using discrete components, such as Surface Mount Technology (SMT) inductors. The inductance of the inductor 98 may also be achieved using an arrangement of the type shown in fig. 9. Using the arrangement of fig. 9, the loop conductor of shunt-fed loop antenna 40 may have an inductance segment SG parallel to ground plane edge GE. The segments SG may be, for example, conductive traces or other conductive elements on a printed circuit board. Dielectric opening DL (e.g., an air-filled or plastic-filled opening) may separate edge portion GE of ground 68 from segment SG of conductive ring portion 70. The segment SG may have a length L. Segment SG and associated ground GE form a transmission line with an associated inductance (i.e., segment SG and ground GE form inductor 98). The inductance of the inductor 98 is in parallel with the feed terminals 54 and 58, thus forming a parallel inductance tuning element of the type shown in fig. 8. Because the inductive element 98 of fig. 9 is formed using a transmission line structure, the inductive element 98 of fig. 9 may introduce less loss than an arrangement in which discrete inductors are used to bridge the feed terminals. For example, the transmission line inductive element 98 may maintain high band performance (as shown by the satisfactory resonant peak 94 of fig. 6), while the discrete inductor may degrade high band performance.

Capacitive tuning may also be used to improve the impedance matching of the antenna 40. For example, the capacitor 100 of fig. 10 may be connected in series with the center conductor 56 of the coaxial cable 52, or other suitable arrangements may be used to introduce series capacitance in the antenna feed portion. As shown in fig. 10, the capacitor 100 may be sandwiched in the coaxial cable center conductor 56 or in other conductive structures located between one end of the transmission line 52 and the positive antenna feed terminal 58. Capacitor 100 may be formed from one or more discrete components (e.g., SMT components), from one or more capacitive structures (e.g., overlapping printed circuit board traces separated by dielectric, etc.), from lateral gaps between conductive traces on a printed circuit board or other substrate, and the like.

The conductive loop of loop antenna 40 of fig. 10 is formed from conductive structure 70 and a conductive portion along edge 76 of grounded conductive structure 66. The loop current may also pass through other portions of the ground plane 68 as shown by the current path 102. A positive antenna feed terminal 58 is connected to one end of the loop path and a ground antenna feed terminal 54 is connected to the other end of the loop path. Inductor 98 bridges terminals 54 and 58 of antenna 40 of fig. 10, so that antenna 40 forms a parallel-fed loop antenna with a bridged inductance (and a series capacitance from capacitor 100).

During operation of the antenna 40, a plurality of circuit paths 102 having different lengths may be formed through the ground plane 68. This may help to broaden the frequency response of antenna 40 in the frequency band of interest. The presence of tuning elements such as shunt inductance 98 and series capacitance 100 may help form an effective impedance matching circuit for antenna 40 that enables antenna 40 to operate with high efficiency in both the high band and the low band (e.g., such that antenna 40 exhibits high band formant 94 of fig. 6 and low band formant 92 of fig. 6).

A simplified smith chart illustrating the possible effects of tuning elements such as inductor 98 and capacitor 100 on the shunt-fed loop antenna 40 is shown in fig. 11. The point Y at the center of the circle 104 represents the impedance of the transmission line 52 (e.g., the 50 ohm coaxial cable impedance to which the antenna 40 is to be matched). A configuration in which the impedance of the antenna 40 is close to the point Y in both the low frequency band and the high frequency band will exhibit satisfactory operation.

Using the shunt-fed antenna 40 of fig. 10, high-band matching is relatively insensitive to the presence or absence of inductive element 98 and capacitor 100. However, these components can significantly affect the low band impedance. An example is an antenna configuration without the inductor 98 and without the capacitor 100 (i.e., a parallel-fed loop antenna of the type shown in fig. 4). In this type of configuration, the low frequency band (e.g., the band at frequency f1 of fig. 6) may be characterized by the impedance represented by point X1 on the circle 104. When an inductor, such as shunt inductance 98 of fig. 9, is added to the antenna, the impedance of the antenna at the low frequency band may be characterized by point X2 of the circular diagram 104. When a capacitor such as the capacitor 100 is added to the antenna, the antenna may be configured as shown in fig. 10. In this type of configuration, the impedance of antenna 40 may be characterized by point X3 of circular diagram 104.

At point X3, antenna 40 matches the impedance of cable 50 well in both the high frequency band (the frequency centered at frequency f2 in fig. 6) and the low frequency band (the frequency centered at frequency f1 in fig. 6). This may enable antenna 40 to support a desired communication band of interest. For example, such a matching arrangement may enable an antenna such as the antenna 40 of fig. 10 to operate in communication bands such as communication bands of 850MHz and 900MHz (a low-frequency band region collectively formed at the frequency f 1), and communication bands of 1800MHz, 1900MHz, and 2100MHz (a high-frequency band region collectively formed at the frequency f 2).

Further, the placement of point X3 helps to ensure that detuning due to touch events is minimized. When a user touches the housing 12 of the device 10 in the vicinity of the antenna 10, or when other external objects are in close proximity to the antenna 40, these external objects affect the impedance of the antenna. In particular, these external objects may tend to introduce capacitive impedance contributions to the antenna impedance. The effect of this type of contribution to the antenna impedance tends to move the impedance of the antenna from point X3 towards X4, as shown by line 106 of circle 104 in fig. 11. Due to the original position of point X3, point X4 is not too far from the optimal point Y. Thus, antenna 40 may perform satisfactorily in a variety of situations (e.g., when device 10 is touched, when device 10 is not touched, etc.).

Although the schematic diagram of fig. 11 represents impedance as points for various antenna configurations, the antenna impedance is typically represented by a set of points (e.g., curved segments on the circular diagram 104) due to the frequency dependence of the antenna impedance. However, the overall representation of the circle 104 represents the representation of the antenna at the frequency of interest. The use of curve segments to represent the frequency dependent antenna impedance has been omitted from figure 11 to avoid overcomplicating the figure.

According to one embodiment, there is provided a shunt-fed loop antenna in an electronic device having an outer periphery, comprising: a conductive annular path formed at least in part by conductive structures disposed along the outer periphery; an inductor sandwiched in the conductive loop path; and first and second antenna feed terminals bridged by the inductor.

In accordance with another embodiment, a shunt-fed loop antenna is provided, wherein the conductive structure of the conductive loop path is formed at least in part by a conductive bezel surrounding the periphery of the electronic device.

In accordance with another embodiment, a shunt-fed loop antenna is provided, wherein the conductive bezel includes a slot.

In accordance with another embodiment, a parallel-feed loop antenna is provided, wherein the first and second antenna feed terminals are located on opposite sides of the slot.

According to another embodiment, there is provided a shunt feed loop antenna, further comprising: an antenna feed that conveys an antenna signal between a transmission line and the first antenna feed terminal; and a capacitor interposed in the antenna feed line.

In accordance with another embodiment, a shunt-fed loop antenna is provided, wherein the inductor comprises an inductive transmission line structure.

In accordance with another embodiment, a shunt-fed loop antenna is provided, wherein the inductive transmission line structure includes a first conductive structure formed by a portion of a ground plane, and a second conductive structure parallel to the first conductive structure, wherein the first conductive structure and the second conductive structure are separated by an opening.

According to one embodiment, there is provided an electronic device including: a housing having an outer periphery; a conductive structure disposed along the outer perimeter and having at least one gap on the outer perimeter; and an antenna formed at least in part from the conductive structure.

In accordance with another embodiment, an electronic device is provided that further includes a display, wherein the conductive structure includes a bezel for the display.

According to another embodiment, an electronic device is provided, the electronic device further comprising a first antenna feed terminal and a second antenna feed terminal for the antenna, wherein the antenna comprises a parallel-fed loop antenna.

According to another embodiment, there is provided an electronic apparatus, further comprising: a substantially rectangular ground plane, wherein a portion of the loop antenna is formed by the substantially rectangular ground plane.

According to another embodiment, an electronic device is provided, wherein the second antenna feed terminal is connected to the substantially rectangular ground plane.

According to another embodiment, there is provided an electronic apparatus, further comprising: radio frequency transceiver circuitry; a transmission line having a positive conductor and a ground conductor, wherein the transmission line is coupled between the radio-frequency transceiver circuitry and the first and second antenna feed terminals; and a capacitor interposed in the positive conductor of the transmission line.

According to another embodiment, an electronic device is provided, further comprising an inductor bridging the first and second antenna feed terminals.

According to another embodiment, an electronic device is provided wherein the second antenna feed terminal is connected to the substantially rectangular ground plane and the first antenna feed terminal is electrically connected to the bezel.

According to one embodiment, there is provided a wireless circuit including: a ground plane; a conductive electronic device bezel having a gap;

a solid dielectric filling the gap; and a first antenna feed terminal and a second antenna feed terminal, wherein the ground plane, the bezel, the first antenna feed terminal, and the second antenna feed terminal form a shunt-feed loop antenna.

In accordance with another embodiment, a wireless circuit is provided that further includes an inductive element, wherein the inductive element bridges the first and second antenna feed terminals.

According to another embodiment, there is provided a wireless circuit, the wireless circuit further comprising: radio-frequency transceiver circuitry coupled to the shunt-fed loop antenna and configured to operate in at least a first communication band and a second communication band.

According to another embodiment, there is provided a wireless circuit, the wireless circuit further comprising: radio-frequency transceiver circuitry coupled to the feed loop antenna and configured to operate in a first communication band covering sub-bands at 850MHz and 900MHz and a second communication band covering sub-bands at 1800MHz, 1900MHz, and 2100 MHz.

According to another embodiment, there is provided a wireless circuit, the wireless circuit further comprising: a capacitive element coupled in series with the first antenna feed terminal, wherein the second antenna feed terminal is connected to the ground plane.

According to one embodiment, there is provided an electronic device including: a display having a rectangular periphery; radio frequency transceiver circuitry; a conductive structure surrounding the rectangular periphery of the display and having a gap along the periphery; an antenna comprising a portion of the conductive structure having the slot and comprising an antenna feed terminal; and a transmission line coupled between the radio-frequency transceiver circuitry and the antenna feed terminal.

In accordance with another embodiment, an electronic device is provided that further includes a solid dielectric in the slot.

According to another embodiment, an electronic device is provided, further comprising an inductive element bridging the antenna feed terminal.

In accordance with another embodiment, an electronic device is provided wherein the conductive structure includes a bezel for the display.

In accordance with another embodiment, an electronic device is provided wherein the inductive element includes a portion of a ground plane and a conductive member separated by an opening.

According to another embodiment, an electronic device is provided, further comprising a capacitive element connected to one of the antenna feed terminals.

According to another embodiment, an electronic device is provided, further comprising a capacitive element connected to a first one of the antenna feed terminals.

According to another embodiment, an electronic device is provided, wherein the transmission line comprises a positive conductor and the capacitive element is connected in series between the positive conductor and the first antenna feed terminal.

In accordance with another embodiment, an electronic device is provided wherein the conductive structure includes a bezel for the display.

According to another embodiment, there is provided an electronic apparatus, further comprising: a printed circuit board having a component mounted thereon, wherein the printed circuit board and the component form at least a portion of a ground plane, and the antenna is formed at least in part by the ground plane.

According to another embodiment, an electronic device is provided, wherein the second antenna feed terminal comprises a ground antenna feed terminal connected to the ground plane.

According to another embodiment, an electronic device is provided, wherein a second one of the antenna feed terminals, different from the first antenna feed terminal, comprises a ground antenna feed terminal connected to the ground plane.

The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The above-described embodiments may be implemented individually or in combination.

Claims (21)

1. A shunt-fed loop antenna in an electronic device having an outer perimeter, comprising:

a conductive annular path formed at least in part by conductive structures disposed along the outer periphery;

an inductor sandwiched in the conductive loop path; and

a first antenna feed terminal and a second antenna feed terminal bridged by the inductor, wherein the conductive structure of the conductive loop path is formed at least in part by a conductive bezel surrounding the periphery of the electronic device.

2. The shunt-fed loop antenna of claim 1, wherein the conductive bezel comprises a slot.

3. The shunt-fed loop antenna of claim 2, wherein the first and second antenna feed terminals are located on opposite sides of the slot.

4. A shunt-fed loop antenna in an electronic device having an outer perimeter, comprising:

a conductive annular path formed at least in part by conductive structures disposed along the outer periphery;

an inductor sandwiched in the conductive loop path; and

a first antenna feed terminal and a second antenna feed terminal bridged by the inductor;

an antenna feed that conveys an antenna signal between a transmission line and the first antenna feed terminal; and

a capacitor interposed in the antenna feed line.

5. The shunt-fed loop antenna of claim 4, wherein the inductor comprises an inductive transmission line structure.

6. A shunt-fed loop antenna in an electronic device having an outer perimeter, comprising:

a conductive annular path formed at least in part by conductive structures disposed along the outer periphery;

an inductor sandwiched in the conductive loop path; and

a first antenna feed terminal and a second antenna feed terminal bridged by the inductor, wherein the inductor comprises an inductive transmission line structure, wherein the inductive transmission line structure comprises a first conductive structure formed by a portion of a ground plane and a second conductive structure parallel to the first conductive structure, and the first and second conductive structures are separated by an opening.

7. An electronic device, further comprising:

a housing having an outer periphery;

a conductive structure disposed along the outer perimeter and having at least one gap on the outer perimeter;

an antenna formed at least in part from the conductive structure;

a display, wherein the conductive structure comprises a bezel for the display;

a first antenna feed terminal and a second antenna feed terminal for the antenna, wherein the antenna comprises a parallel-fed loop antenna;

a substantially rectangular ground plane, wherein a portion of the loop antenna is formed by the substantially rectangular ground plane, and wherein the second antenna feed terminal is connected to the substantially rectangular ground plane;

radio frequency transceiver circuitry;

a transmission line having a positive conductor and a ground conductor, wherein the transmission line is coupled between the radio-frequency transceiver circuitry and the first and second antenna feed terminals; and

a capacitor interposed in the positive conductor of the transmission line.

8. The electronic device defined in claim 7 further comprising an inductor that bridges the first and second antenna feed terminals.

9. The electronic device defined in claim 7 wherein the second antenna feed terminal is connected to the substantially rectangular ground plane and the first antenna feed terminal is electrically connected to the bezel.

10. A wireless circuit, comprising:

a ground plane;

a conductive electronic device bezel having a gap;

a solid dielectric filling the gap;

a first antenna feed terminal and a second antenna feed terminal, wherein the ground plane, the bezel, the first antenna feed terminal, and the second antenna feed terminal form a parallel-feed loop antenna; and

an inductive element, wherein the inductive element bridges the first and second antenna feed terminals.

11. The wireless circuitry defined in claim 10 further comprising:

radio-frequency transceiver circuitry coupled to the shunt-fed loop antenna and configured to operate in at least a first communication band and a second communication band.

12. The wireless circuitry defined in claim 10 further comprising:

radio-frequency transceiver circuitry coupled to the feed loop antenna and configured to operate in a first communication band covering sub-bands at 850MHz and 900MHz and a second communication band covering sub-bands at 1800MHz, 1900MHz, and 2100 MHz.

13. The wireless circuitry defined in claim 12 further comprising: a capacitive element coupled in series with the first antenna feed terminal, wherein the second antenna feed terminal is connected to the ground plane.

14. An electronic device, comprising:

a display having a rectangular periphery;

radio frequency transceiver circuitry;

a conductive structure surrounding the rectangular periphery of the display and having a gap along the periphery;

an antenna comprising a portion of the conductive structure having the slot and comprising an antenna feed terminal; and

a transmission line coupled between the radio-frequency transceiver circuitry and the antenna feed terminal;

a solid dielectric in the gap; and

an inductive element bridging the antenna feed terminal.

15. The electronic device defined in claim 14 wherein the conductive structures comprise a bezel for the display.

16. The electronic device defined in claim 14 wherein the inductive element comprises portions of a ground plane and a conductive member separated by an opening.

17. The electronic device defined in claim 14 further comprising a capacitive element connected to a first of the antenna feed terminals.

18. The electronic device defined in claim 17 wherein the transmission line comprises a positive conductor and the capacitive element is connected in series between the positive conductor and the first antenna feed terminal.

19. The electronic device defined in claim 18 wherein the conductive structures comprise a bezel for the display.

20. The electronic device of claim 17, further comprising:

a printed circuit board having a component mounted thereon, wherein the printed circuit board and the component form at least a portion of a ground plane, and the antenna is formed at least in part by the ground plane.

21. The electronic device defined in claim 20 wherein a second one of the antenna feed terminals that is different than the first antenna feed terminal comprises a ground antenna feed terminal that is connected to the ground plane.