PATENT DOCUMENT

Publication Number: US-10283844-B2
Application Number: US-201615275192-A
Country: US
Kind Code: B2

Title: Electronic devices having housing-integrated distributed loop antennas

Abstract:
An electronic device may include a metal housing and a distributed loop antenna. The antenna may include a dielectric carrier. The antenna may include a distributed loop antenna resonating element that extends around the carrier and a loop antenna feed element on the carrier. Portions of the feed element and loop antenna resonating element may be formed from the housing. The feed element may be directly fed and may indirectly feed the distributed loop antenna resonating element via near field electromagnetic coupling. The loop antenna resonating element may include a conductive sheet on the carrier. The conductive sheet and the housing may form a conductive loop path of the loop antenna resonating element. A capacitance may be interposed in the conductive loop path and may be formed by a gap between the conductive sheet and the housing. A speaker driver may be placed within a cavity in the carrier.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a conductive housing; 
 a dielectric carrier; 
 a loop antenna resonating element, wherein the loop antenna resonating element comprises a sheet of conductive material on the dielectric carrier; 
 an antenna feed structure that indirectly feeds the loop antenna resonating element and that is separated from the sheet of conductive material by a gap, wherein a portion of the antenna feed structure is formed from a portion of the conductive housing; and 
 an electrical component that bridges the gap. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the antenna feed structure comprises a loop of conductive material that includes the portion of the conductive housing. 
     
     
       3. The electronic device defined in  claim 2 , wherein the loop of conductive material comprises metal traces on the dielectric carrier. 
     
     
       4. The electronic device defined in  claim 3 , wherein the metal traces on the dielectric carrier are shorted to an end of the portion of the conductive housing that forms the portion of the antenna feed structure. 
     
     
       5. The electronic device defined in  claim 3 , further comprising:
 a first antenna feed terminal located on the metal traces; 
 a second antenna feed terminal located at an end of the portion of the conductive housing; and 
 a radio-frequency transmission line having a signal conductor that is directly connected to the first antenna feed terminal and a ground conductor that is directly connected to the second antenna feed terminal, wherein the metal traces comprise a first segment, a second segment that extends parallel to the first segment and that is shorted to the conductive housing, and a third segment that extends between the first and second segments, the first antenna feed terminal is located at an end of the first segment, the end of the first segment is separated from the portion of the conductive housing by a first additional gap, the third segment is separated from the portion of the conductive housing by a second additional gap that is wider than the first additional gap, and the second segment is interposed between the first segment and a portion of the sheet of conductive material. 
 
     
     
       6. The electronic device defined in  claim 3 , wherein the electrical component comprises:
 a capacitor coupled between the metal traces and the sheet of conductive material in the loop antenna resonating element. 
 
     
     
       7. The electronic device defined in  claim 3 , wherein the antenna feed structure comprises a parallel tank circuit that forms an open circuit between the metal traces and the conductive housing in a first frequency band and that forms a closed circuit between the metal traces and the conductive housing in a second frequency band that is lower than the first frequency band, the metal traces comprise an extended conductive segment that resonates in the second frequency band, the antenna feed structure resonates in the first frequency band, and the loop antenna resonating element resonates in the second frequency band. 
     
     
       8. The electronic device defined in  claim 1 , wherein the loop antenna resonating element comprises an additional portion of the conductive housing, the additional portion of the conductive housing and the sheet of conductive material forming a conductive loop path for the loop antenna resonating element, the conductive housing comprises a conductive housing sidewall for the electronic device that includes the portion of the conductive housing and at least some of the additional portion of the conductive housing, the electronic device further comprising:
 a display having a display cover layer, wherein the conductive housing comprises a conductive rear wall for the electronic device that opposes the display cover layer, and the additional portion of the conductive housing comprises a portion of the conductive rear wall. 
 
     
     
       9. The electronic device defined in  claim 1 , wherein the sheet of conductive material is formed on at least first and second adjacent sides of the dielectric carrier and an additional portion of the antenna feed structure is formed from conductive structures on the first side of the dielectric carrier. 
     
     
       10. The electronic device defined in  claim 9 , wherein the loop antenna resonating element comprises a portion of electronic device rear wall and a portion of the electronic device sidewall, the conductive structures and the portion of the conductive housing form a conductive loop path of the antenna feed structure, the sheet of conductive material, the portion of electronic device rear wall, and the portion of the electronic device sidewall form an additional conductive loop path of the loop antenna resonating element, and the conductive loop path of the antenna feed structure and the additional conductive loop path of the antenna feed structure are coupled using near-field electromagnetic coupling. 
     
     
       11. The electronic device defined in  claim 1 , wherein the dielectric carrier has an air-filled cavity, the electronic device further comprising:
 a speaker driver within the air-filed cavity, wherein the conductive housing comprises a first set of openings, the dielectric carrier comprises a second set of openings that are aligned with the first set of openings, and the speaker driver produces sound waves that pass through the first and second set of openings. 
 
     
     
       12. The electronic device defined in  claim 1 , wherein the sheet of conductive material is formed on at least one side of the dielectric carrier, the antenna feed structure comprises conductive structures formed on the one side of the dielectric carrier, and the electrical component comprises a capacitor that bridges the gap. 
     
     
       13. The electronic device defined in  claim 1 , wherein the sheet of conductive material forms at least part of a conductive loop path that loops around a first axis, the antenna feed structure includes an additional conductive loop path formed at least partly from the portion of the conductive housing, and the additional conductive loop loops around a second axis that is substantially perpendicular to the first axis.

Description:
BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for electronic devices with wireless communications circuitry. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of communications bands. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over a range of operating frequencies and with a satisfactory efficiency bandwidth. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device may have a metal housing that forms a ground plane. The metal housing may, for example, include a rear housing wall and sidewalls of the electronic device. The metal housing and other structures in the electronic device may be used in forming antennas. 
     The electronic device may include one or more distributed loop antennas. The antenna may include a dielectric carrier. The dielectric carrier may have an elongated shape that extends along a longitudinal axis. The antenna may include a distributed loop antenna resonating element formed over the carrier that extends around the longitudinal axis. The antenna may include a loop antenna feed element formed on the dielectric carrier. A portion of the loop antenna feed element and a portion of the distributed loop antenna resonating element may be formed from the metal housing. For example, a sidewall of the metal housing may form a part of the loop antenna feed element and a part of the distributed loop antenna resonating element. A rear wall of the metal housing may also form a part of the distributed loop antenna resonating element. 
     A first antenna feed terminal and a second antenna feed terminal may be directly connected to the loop antenna feed element. The feed element may receive radio-frequency signals from transceiver circuitry using a radio-frequency transmission line. The feed element may indirectly feed the radio-frequency signals to the distributed loop antenna resonating element via near field electromagnetic coupling. The feed element may exhibit an antenna resonance at a first frequency (e.g., 5.0 GHz) whereas the distributed loop antenna resonating element exhibits an antenna resonance at a second frequency (e.g., 2.4 GHz). A capacitor may be coupled between the feed element and the distributed loop antenna resonating element to reduce the second frequency if desired. If desired, a parallel tank circuit may be formed on the feed element to enhance isolation between signals at the first and second frequencies. 
     The distributed loop antenna resonating element may be formed from a conductive sheet placed over first and second sides of the dielectric carrier. The conductive sheet may be shorted to the rear wall of the metal housing using a conductive fastener. The conductive sheet, the rear wall of the metal housing, and the sidewall of the metal housing may form a conductive loop path of the distributed loop antenna resonating element. A capacitance may be interposed in the conductive loop path. The capacitance may be formed by a gap having edges defined by the conductive sheet and the conductive sidewall. A speaker driver may be placed within an air-filled cavity in the dielectric substrate. 
     The electronic device may include a display having an active area that emits light and an inactive area. The antenna may be placed within the inactive area. By forming part of the feed element and part of the distributed loop antenna resonating element using the metal housing, the size of the inactive area may be reduced while still allowing the antenna to exhibit sufficient bandwidth efficiency at frequencies of interest. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 3  is a diagram of illustrative wireless circuitry in an electronic device in accordance with an embodiment. 
         FIG. 4  is a diagram of illustrative distributed loop antenna structures in accordance with an embodiment. 
         FIG. 5  is a top view of an illustrative antenna mounted in a lower portion of an electronic device housing beneath an inactive area of a display in accordance with an embodiment. 
         FIG. 6  is a top view of an illustrative indirectly-fed distributed loop antenna formed partially from an electronic device housing in accordance with an embodiment. 
         FIGS. 7 and 8  are cross-sectional side views of an illustrative indirectly-fed distributed loop antenna formed partially from an electronic device housing in accordance with an embodiment. 
         FIG. 9  is a graph of antenna performance (standing wave ratio SWR) plotted as a function of operating frequency that shows how a capacitor may adjust the resonance of an antenna of the type shown in  FIGS. 6-8  in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative distributed loop antenna having a feeding element with an extended portion for handling high band communications in accordance with an embodiment. 
         FIG. 11  is an equivalent circuit diagram of an illustrative indirect feeding element of the type shown in  FIG. 10  in accordance with an embodiment. 
         FIG. 12  is a graph of antenna performance plotted as a function of operating frequency for an illustrative antenna of the type shown in  FIGS. 6-8, 10, and 11  that shows respective contributions to performance that may be made by an indirect feeding element and by a distributed loop antenna resonating element in accordance with an embodiment. 
         FIG. 13  is a graph of antenna performance (antenna efficiency) plotted as a function of operating frequency that shows how an illustrative antenna of the type shown in  FIGS. 6-12  may exhibit optimal antenna efficiency while occupying a minimal space in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may be provided with wireless circuitry that includes antennas. The antennas may be used to transmit and receive wireless signals. 
     The wireless circuitry of device  10  may handle one or more communications bands. For example, the wireless circuitry of device  10  may include a Global Position System (GPS) receiver that handles GPS satellite navigation system signals at 1575 MHz or a GLONASS receiver that handles GLONASS signals at 1609 MHz. Device  10  may also contain wireless communications circuitry that operates in communications bands such as cellular telephone bands and wireless circuitry that operates in communications bands such as the 2.4 GHz Bluetooth® band and the 2.4 GHz and 5 GHz WiFi® wireless local area network bands (sometimes referred to as IEEE 802.11 bands or wireless local area network communications bands). Device  10  may also contain wireless communications circuitry for implementing near-field communications at 13.56 MHz or other near-field communications frequencies. If desired, device  10  may include wireless communications circuitry for communicating at 60 GHz, circuitry for supporting light-based wireless communications, or other wireless communications. 
     Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  may be mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). In the example of  FIG. 1 , housing  12  includes a conductive peripheral sidewall structure  12 W that surrounds a periphery of device  10  (e.g., that surrounds the rectangular periphery of device  10  as shown in  FIG. 1 ). Housing  12  may, if desired, include a conductive rear wall structure  12 R that opposes display  14  (e.g., conductive rear wall structure  12 R may form the rear exterior face of device  10 ). If desired, rear wall  12 R and sidewalls  12 W may be formed from a continuous metal structure (e.g., in a unibody configuration) or from separate metal structures. Openings may be formed in housing  12  to form communications ports, holes for buttons, and other structures if desired. 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may have an active area AA that includes an array of display pixels. The array of pixels may be formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels or other light-emitting diode pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, transparent ceramic, sapphire, or other transparent crystalline material, or other transparent layer(s). The display cover layer may have a planar shape, a convex curved profile, a shape with planar and curved portions, a layout that includes a planar main area surrounded on one or more edges with a portion that is bent out of the plane of the planar main area, or other suitable shapes. The display cover layer may cover the entire front face of device  10  (e.g., extending across an entirety of a length dimension of device  10  parallel to the y-axis and a width dimension of device  10  parallel to the x-axis of  FIG. 1 ). In another suitable arrangement, the display cover layer may cover substantially all of the front face of device  10  or only a portion of the front face of device  10 . Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as a speaker port. Openings such as openings  8  may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.) and/or audio ports for audio components such as a speaker and/or a microphone. 
     Display  14  may have an inactive border region that runs along one or more of the edges of active area AA. Inactive area IA may be free of pixels for displaying images and may overlap circuitry and other internal device structures in housing  12 . To block these structures from view by a user of device  10 , the underside of the display cover layer or other layer in display  14  that overlaps inactive area IA may be coated with an opaque masking layer in inactive area IA. The opaque masking layer may have any suitable color. 
     Antennas may be mounted in housing  12 . For example, housing  12  may have four peripheral edges (e.g., conductive sidewalls  12 W) as shown in  FIG. 1  and one or more antennas may be located along one or more of these edges. As shown in the illustrative configuration of  FIG. 1 , antennas may, if desired, be mounted in regions  20  along opposing peripheral edges of housing  12  (as an example). The antennas may include antenna resonating elements that emit and receive signals through the front of device  10  (i.e., through inactive portions IA of display  14 ) and/or from the rear and sides of device  10 . In practice, active components within active display area AA may block or otherwise inhibit signal reception and transmission by the antennas. By placing the antennas within regions  20  of inactive area IA of display  14 , the antennas may freely pass signals through the display without the signals being blocked by active display circuitry. Antennas may also be mounted in other portions of device  10 , if desired. The configuration of  FIG. 1  is merely illustrative. 
     In order to provide an end user of device  10  with as large of a display as possible (e.g., to maximize an area of the device used for displaying media, running applications, etc.), it may be desirable to increase the amount of area at the front face of device  10  that is covered by active area AA of display  14 . Increasing the size of active area AA may reduce the size of inactive area IA within device  10 . This may reduce the space  20  that is available for forming antennas within device  10 . In general, antennas that are provided with larger operating volumes or spaces may have higher bandwidth efficiency than antennas that are provided with smaller operating volumes or spaces. If care is not taken, increasing the size of active area AA may reduce the operating space available to the antennas, which can undesirably inhibit the efficiency bandwidth of the antennas (e.g., such that the antennas no longer exhibit satisfactory radio-frequency performance). It would therefore be desirable to be able to provide antennas that occupy a small amount of space within device  10  (e.g., to allow for as large of a display active area AA as possible) while still allowing the antennas to operate with optimal efficiency bandwidth. 
     A schematic diagram showing illustrative components that may be used in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  22 . Storage and processing circuitry  22  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  22  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  22  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  22  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO protocols, antenna diversity protocols, etc. 
     Input-output circuitry  24  may include input-output devices  26 . A user can control the operation of device  10  by supplying commands (user input) through input-output devices  26  and may receive status information and other output from device  10  using the output resources of input-output devices  26 . 
     Input-output devices  26  may include sensors and status indicators  30  such as an ambient light sensor, a proximity sensor, a temperature sensor, a pressure sensor, a magnetic sensor, an accelerometer, gyroscope, compass, and light-emitting diodes and other components for gathering information about the environment in which device  10  is operating and providing information to a user of device  10  about the status of device  10 . 
     Input-output devices  26  may include audio components  38 . Audio components  38  may include speakers and tone generators for presenting sound to a user of device  10  and microphones for gathering user audio input. As an example, speakers in audio components  38  may include acoustic cavities and speaker drivers that are placed within the acoustic cavities. When the speaker drives are driven with electrical audio (speaker) signals, the speaker driver may produce mechanical sound waves that resonate within the acoustic cavity. The acoustic cavity may amplify the sound waves to audible levels. The amplified sound waves may pass through audio ports such as speaker holes  8  of  FIG. 1  so that they can be heard by a user of device  10 . 
     Display  14  may be used to present images for a user such as text, video, and still images. Sensors  30  may include a touch sensor array that is formed as one of the layers in display  14 , for example. User input may be gathered using buttons and other input-output components  36  such as touch pad sensors, buttons, joysticks, scrolling wheels, click wheels, touch pads, key pads, keyboards, microphones, cameras, digital data port devices, etc. 
     Input-output circuitry  24  may include wireless communications circuitry  28  for communicating wirelessly with external equipment. Wireless communications circuitry  28  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, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  28  may include radio-frequency transceiver circuitry  46  for handling various radio-frequency communications bands. For example, circuitry  28  may include transceiver circuitry  38 ,  40 , and  42 . Transceiver circuitry  40  may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5.0 GHz bands for wireless local area network communications such as WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band. Circuitry  28  may use cellular telephone transceiver circuitry  42  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1400 MHz or 1500 MHz to 2170 MHz (e.g., a midband with a peak at 1700 MHz), and a high band from 2170 or 2300 to 2700 MHz (e.g., a high band with a peak at 2400 MHz) or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  42  may handle voice data and non-voice data. Wireless communications circuitry  28  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  28  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. Wireless communications circuitry  28  may include satellite navigation system circuitry such as global positioning system (GPS) receiver circuitry  38  for receiving GPS signals at 1575 MHz, Global Navigation Satellite System (GLONASS) signals, or for handling other satellite positioning data. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  28  may include antennas  44 . Antennas  44  may be formed using any suitable antenna types. For example, antennas  44  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, monopole antenna structures, dipole antenna structures, helical antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     As shown in  FIG. 3 , transceiver circuitry  46  in wireless circuitry  28  may be coupled to antenna structures  40  using paths such as path  48 . Wireless circuitry  28  may be coupled to control circuitry  22 . Control circuitry  22  may be coupled to input-output devices  26 . Input-output devices  26  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures  44  with the ability to cover communications frequencies of interest, antenna structures  44  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna structures  44  may be provided with adjustable circuits such as tunable components  58  to tune antennas over communications bands of interest. Tunable components  58  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. 
     During operation of device  10 , control circuitry  22  may issue control signals on one or more paths such as path  60  that adjust inductance values, capacitance values, or other parameters associated with tunable components  58 , thereby tuning antenna structures  44  to cover desired communications bands. 
     Path  48  may include one or more transmission lines. As an example, signal path  48  of  FIG. 3  may be a transmission line having first and second conductive paths such as paths  50  and  52 , respectively. Path  50  may be a positive signal line and path  52  may be a ground signal line. Lines  50  and  52  may form parts of a coaxial cable, a microstrip transmission line, or a stripline transmission line (as examples). A matching network (not shown) formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna structures  44  to the impedance of transmission line  48 , if desired. Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna structures  44 . 
     Transmission line  48  may be directly coupled to an antenna resonating element and ground for antenna  44  or may be coupled to near-field-coupled antenna feed structures for antenna  44 . As an example, antenna structures  44  may form an inverted-F antenna, a slot antenna, a loop antenna, or other antenna having an antenna feed with a positive (signal) antenna feed terminal such as terminal  54  and a ground antenna feed terminal such as ground antenna feed terminal  56 . Positive transmission line conductor  50  may be coupled to positive antenna feed terminal  54  and ground transmission line conductor  52  may be coupled to ground antenna feed terminal  56 . Antenna structures  44  may include an antenna resonating element such as a loop antenna resonating element or other element that is indirectly fed using near-field coupling. In a near-field coupling arrangement, transmission line  48  is coupled to a near-field-coupled antenna feed structure that is used to indirectly feed antenna structures such as a loop antenna resonating element or other element through near-field electromagnetic coupling. 
     Antenna structures  44  may be formed from metal traces or other conductive material supported by a dielectric carrier. With one suitable arrangement, antenna structures  44  may be based on loop antenna structures. For example, antenna structures  44  may include a strip of conductive material that is wrapped or arranged into a loop. Because the strip of conductive material has an associated width across which material is distributed, loop antenna structures such as these may sometimes be referred to as distributed loop antenna structures. A distributed loop antenna may be fed using a direct feeding arrangement in which feed terminals such as terminals  54  and  56  are coupled directly to the strip of material that forms the loop, may be fed indirectly by using near-field electromagnetic coupling to couple a loop antenna feeding element or other element to the loop that is formed from the strip of material, or may be fed using other suitable feed arrangements. 
     A schematic diagram of a distributed loop antenna of the type that may be used in electronic device  10  is shown in  FIG. 4 . As shown in  FIG. 4 , distributed loop antenna structures  44  (sometimes referred to as distributed loop antenna  44  or indirectly fed distributed loop antenna  44 ) may include a first loop antenna resonating element L 1  that is formed from a loop of conductor such as conductor  70  and a second loop antenna resonating element L 2  (a distributed loop element) that is formed from a loop of conductor such as conductor  72 . 
     As shown in  FIG. 4 , loop antenna resonating element L 2  may be indirectly fed using loop-shaped antenna resonating element L 1 , which serves as an indirect antenna feeding structure. Loop-shaped antenna resonating element L 1  may therefore sometimes be referred to herein as loop antenna feeding element L 1 , loop antenna feed L 1 , antenna feeding element L 1 , or antenna feed element L 1 . As illustrated by electromagnetic fields  78  of  FIG. 4 , antenna element L 1  and loop-shaped antenna resonating element L 2  may be coupled using near-field electromagnetic coupling. 
     Antenna structures  44  of  FIG. 4  may be coupled to radio-frequency transceiver circuitry  46  ( FIG. 3 ) using transmission line  48 . For example, positive transmission line conductor  50  may be coupled to positive antenna feed terminal  54  and ground transmission line conductor  52  may be coupled to ground antenna feed terminal  56 . 
     In the illustrative configuration of  FIG. 4  in which the conductive lines of transmission line  48  are coupled to the feed terminals  54  and  56  of antenna element L 1 , antenna resonating element L 2  may be indirectly fed. Antenna element L 1  may be directly fed using feed terminals  54  and  56 . Directly fed element L 1  may indirectly feed radio-frequency antenna signals to element L 2  via near field coupling  78 . If desired, antenna resonating element L 2  may be directly fed by coupling transmission line  48  across pairs of terminals in element L 2 . Indirect feeding arrangements for loop antenna structures  44  may sometimes be described herein as an example. This is, however, merely illustrative. In general, any suitable feeding arrangement may be used for feeding antenna  44  if desired. 
     Loop antenna structures  44  may be formed using conductive antenna resonating element structures such as metal traces on a dielectric carrier. The dielectric carrier may be formed from glass, ceramic, plastic, or other dielectric material. As an example, the dielectric carrier may be formed from a plastic support structure. The plastic support structure may, if desired, be formed from a hollow speaker box enclosure that serves as a resonant cavity for a speaker driver. 
     The conductive structures that form loop antenna structures  44  may include wires, metal foil, conductive traces on printed circuit boards, portions of conductive housing structures such as conductive housing walls and conductive internal frame structures, and other conductive structures. 
     As shown in  FIG. 4 , antenna resonating element L 2  may have a longitudinal axis such as axis  74 . Axis  74  may sometimes be referred to as the longitudinal axis of loop distributed loop antenna structures  44  and/or the longitudinal axis of a dielectric carrier used to support conductive loop structures. Loop antenna structures  44  may have resonating element conductive structures that are spread out (“distributed”) along longitudinal axis  74  of loop L 2 . For example, conductive structures  72  in resonating element loop L 2  of antenna structures  44  may include a strip or sheet of conductor that has a first dimension that is wrapped around longitudinal axis  74  and a second dimension that extends along the length of longitudinal axis  74 . Conductive structures  72  may wrap around axis  74 . During operation, antenna currents can flow within the strip-shaped conductive material of loop L 2  around axis  74 . In effect, conductive material  72  will form a wide strip of conductor in the shape of a loop that is characterized by a perimeter P. The antenna currents flowing in loop L 2  tend to wrap around longitudinal axis  74 . When installed within device  10 , longitudinal axis  74  of antenna element L 2  may extend parallel to an adjacent edge of housing  12  in electronic device  10  (as an example). 
     It may be desirable to form distributed loop antenna structures  102  from conductive structures that exhibit a relatively small dimension P. In a loop without any break along periphery P, the antenna may resonate at signal frequencies where the signal has a wavelength approximately equal to P. In compact structures with unbroken loop shapes, the frequency of the communications band covered by antenna loop L 2  may therefore tend to be high. By incorporating a gap or other capacitance-generating structure into the loop, a capacitance C can be introduced into antenna loop L 2 . Conductive material  72  may also be configured to form one or more inductor-like paths to introduce inductance L into antenna loop L 2  if desired. Material  72  may, for example, be configured to produce segments of conductive material  72  within loop L 2  that serve as inductance-producing wires. With the presence of capacitance C and inductance L within the perimeter of loop antenna element L 2 , the resonant frequency of antenna element L 2  may be reduced to a desired frequency of operation without enlarging the value of perimeter P. 
     Indirect feed element L 1  may be formed from conductive structures  70 . Conductive structures  70  may include a strip or sheet of conductor that winds around longitudinal axis  76 . The width of conductor  70  may be less than the width (e.g., second dimension) of distributed loop L 2 . In order to ensure efficient near field coupling  78  between loops L 1  and L 2 , longitudinal axis  76  of feed element L 1  may be oriented at a substantially perpendicular angle with respect to longitudinal axis  74  of distributed loop element L 2 . For example, axis  76  may be oriented at 90 degrees with respect to axis  74  or at an angle between 75 and 105 degrees with respect to axis  74 . Loop element L 1  may, for example, be placed at a distance from element L 2  that is less than or equal to a wavelength of operation of antenna  44 . During operation, currents flow through loop L 1  between feed terminals  54  and  56  (e.g., in a loop path around axis  76 ). These currents electromagnetically induce currents to flow through loop L 2  via near field coupling  78 . 
     During operation, both elements L 1  and L 2  may contribute to the overall performance of antenna structures  44 . For example, at lower frequencies such as frequencies in a low band such as a 2.4 GHz frequency band, antenna resonating element L 2  may serve as the primary radiating element in structures  44  and antenna resonating element L 1  serves as a secondary radiating element in structures  44 . At higher frequencies such as frequencies in high band such as a 5.0 GHz frequency band, antenna resonating element L 1  may serve as the primary radiating element in antenna structures  44  and antenna resonating element L 2  serves as a secondary radiating element. This example is merely illustrative and, in general, each loop element may provide any desired contribution to antenna performance in any desired band. 
       FIG. 5  is a front view of device  10  showing how antenna  44  may be integrated within housing  12  of device  10 . As shown in  FIG. 5 , one or more antennas  44  may be formed under inactive area IA of display  44  within region  20 . 
     In the example of  FIG. 5 , two antennas  44  are formed within region  20 . For example, a left antenna  44 L may be formed on a first side of button  16  whereas a right antenna  44 R is formed on a second side of button  16 . Left and right antennas  44  may be identical antennas, mirrored antennas, or may be different antennas. If desired, some of antennas  44 L or  44 R may be formed under button  16 . 
     In order to provide as large an active area AA for display  14  as possible, the width W occupied by inactive area IA of display  14  may be reduced. This reduces the amount of space available for antennas  44  within region  20 . In order to conserve the space required for inactive area IA (e.g., so that more area on device  10  is available for active area AA), audio components such as speaker drivers  64  may be mounted within antennas  44  (e.g., a first speaker driver  64 L may be mounted within left antenna  44 L whereas a second speaker driver  64 R is mounted within right antenna  44 R). In this scenario, each antenna  44  may define an acoustic speaker cavity that is driven by speaker driver  64  to generate audio signals that are transmitted out of device  10  through speaker holes  8 . The example of  FIG. 5  is merely illustrative and, in general, any desired number of antennas  44  may be formed at any desired location within region  20  (e.g., two antennas, one antenna, or more than two antennas  44  may be formed in region  20 ). If desired, speaker driver  64  may be formed within one or none of antennas  44 L and  44 R. Driver  64  may be located near and end of antenna  44  that is adjacent to button  16  or at any other desired location. 
     In order to further conserve the amount of space required for inactive area IA (e.g., to maximize the space available for active area AA), the size of antennas  44  may be reduced, thereby reducing width W. However, if care is not taken, reducing width W and the corresponding size of antennas  44  can undesirably inhibit the efficiency bandwidth of antennas  44 . 
       FIG. 6  is a front view of device  10  showing how antennas  44  may be integrated within housing  12  of device  10 . As shown in  FIG. 6 , antenna  44  (e.g., an antenna such as antenna  44 L of  FIG. 5 ) may be formed under inactive area IA of display  14  near the edge of device  10 . 
     Antenna feeding element loop L 1  and distributed loop antenna resonating element L 2  may be formed from metal, conductive materials that contain metal, or other conductive substances. For example, antenna feeding element L 1  may be formed from conductive structures  70  (e.g., as shown in  FIG. 4 ). Distributed loop antenna element L 2  may be formed from conductive structures  72 . In order to further reduce the space occupied by antenna  44 , part of the conductive structures  70  that form loop feeding element L 1  and part of the conductive structures  72  that form distributed loop antenna resonating element L 2  may be formed from conductive housing  12  (e.g., from sidewall  12 W of housing  12 ). 
     One or more support structures such as support structures  90  may be used to support conductive structures  70  and  72 . Support structures  90  may be formed from a dielectric such as plastic. In one suitable arrangement, support structures  90  may include a single elongated dielectric carrier that extends across the width  113  of antenna  44 . If desired, support structures  90  may include multiple separate carrier structures. Conductive structures  70  in feed element L 1  may include a first portion  70 - 1 , a second portion  70 - 2 , and a third portion  70 - 3  that are formed on top surface  99  of dielectric carrier  90 . Conductive structures  72  in distributed loop antenna resonating element L 2  may include a first portion  72 - 1  formed on top surface  99  of dielectric carrier  90 . Conductor  72 - 1  may extend down and over side  91  of carrier  90  (e.g., the side of carrier  90  that opposes housing sidewall  12 W). If desired, conductive structures  72 - 1 ,  70 - 1 ,  70 - 2 , and/or  70 - 3  may be formed from metal traces that are in direct contact with carrier  90 . For example, conductive structures  72 - 1 ,  70 - 1 ,  70 - 2 , and/or  70 - 3  may be patterned or etched directly onto carrier  90 . In another suitable arrangement, conductive structures  72 - 1 ,  70 - 1 ,  70 - 2 , and/or  70 - 3  may be formed from metal traces on a flexible printed circuit board that is placed over carrier  90 . If desired, conductive structures  72 - 1 ,  70 - 1 ,  70 - 2 , and/or  70 - 3  may be formed from stamped pieces of sheet metal that are placed on top surface  99  of carrier  90 . The stamped sheet metal used to form conductive structure  72 - 1  may extend over side  91  of carrier  90 , for example. 
     Conductive structures  70  of feed element L 1  may include a portion  70 - 4  of conductive housing sidewall  12 W. Conductive structures  72  in distributed loop antenna resonating element L 2  may include a portion  72 - 2  of conductive housing wall  12 W. Conductive structures  72  may also include a portion of the metal rear wall of device  10 , which is not shown in  FIG. 6  for the sake of clarity. Carrier  90  may be placed within device  10  so that housing sidewall  12 W covers side (surface)  93  of dielectric carrier  90 . The opposing side  91  of carrier  90  may be substantially, partially, or completely covered by conductive structure  72 - 1 . The bottom side of carrier  90  (i.e., the side of carrier  90  opposing top side  99 ) may be covered by the metal rear wall of housing  12 . Left side  97  and right side  95  of carrier  90  may be covered with other conductive structures or may be free from conductive structures. 
     By forming part of feed loop L 1  and part of distributed loop antenna resonating element L 2  from conductive portions of housing  12 , the total space occupied by antenna  44  in device  10  may be reduced relative to scenarios where the antenna is formed separately from housing  12 . For example, antenna  44  may occupy a width W′ within device  10  that is much smaller than when antenna  44  is formed separately from housing  12 . By reducing the width W′ occupied by antenna  44 , display  14  may have a maximal active area AA and a minimal inactive area IA, thereby maximizing the viewable size of the display on the device. Width W′ may be, for example, 5 mm, less than 5 mm, 9 mm, between 5 and 9 mm, between 9 and 15 mm, more than 15 mm, or any other desired length. 
     Dielectric carrier  90  may be a hollow carrier that includes a cavity that is filled with air. Speaker driver  64  may be placed within the cavity defined by dielectric carrier  90 . Speaker driver  64  may, for example, include speaker coils, magnets, shunt structures, diaphragm structures, or any other desired speaker driver components. Speaker driver  64  may be driven using electrical audio signals and may convert the electrical audio signals into sound waves. The sound waves may be mechanically amplified by the cavity within dielectric carrier  90 . Openings within dielectric carrier  90  may be aligned with speaker openings  8  in housing sidewall  12 W so that the audio signals can escape out of device  10  and be heard by a user. 
     In one suitable arrangement, antenna feed element loop traces  70 - 1 ,  70 - 2 , and  70 - 3  may be mounted in a ground cavity (i.e., loop L 1  may be mounted in a cavity-backed antenna environment). For example, metal structure  72 - 1 , housing sidewall  12 W, a metal housing rear wall, and optionally conductive structures on sides  97  and  95  may define a conductive cavity that backs feed L 1 . By placing traces  70 - 1 ,  70 - 2 , and  70 - 3  within the conductive cavity, feed element L 1  can be decoupled from surrounding metal structures in device  10  (e.g., the performance of loop L 1  will not be affected by variations in the distance between carrier  90  and nearby conductive structures). 
     Loop feeding element L 1  may be directly fed by transmission line  48  using an antenna feed that includes positive (+) antenna feed terminal  54  and ground (−) antenna feed terminal  56 . For example, signal conductor  50  (e.g., a signal conductor of a coaxial cable or other transmission line structure) and ground conductor  52  (e.g., a ground conductor or outer braid of a coaxial cable or other transmission line structure) of transmission line  48  ( FIG. 3 ) may be in direct contact with conductive structures  70  of feeding loop L 1 . In the example of  FIG. 6 , positive antenna feed terminal  54  is located at a bottom edge of conductive trace  70 - 1  whereas ground antenna feed terminal  56  is located on an inner edge of housing sidewall  12 W (e.g., portion  70 - 4  of loop feed L 1 ). If desired, feed terminal  54  may be placed at another location on conductive portion  70 - 1 . Feed terminals  54  and  56  may be separated by gap  150  (e.g., a portion of the surface of carrier  90  that is free from conductive material). 
     Conductive trace  70 - 3  of feed element L 1  may be coupled to housing sidewall  12 W at location  92 . For example, trace  70 - 3  may be directly and electrically connected to sidewall  12 W using solder, welds, conductive adhesive, conductive fastening structures such as screws, or any other desired structures that form a direct electrical connection between trace  70 - 3  and sidewall  12 W. Portion  70 - 4  of feed L 1  that is formed using housing sidewall  12 W may include the portion of housing sidewall  12 W that extends between connecting location  92  and ground feed terminal  56 . Conductive trace  70 - 2  of feed element L 1  may extend from an edge of portion  70 - 1  that opposes feed terminal  54  to the edge of trace  70 - 3  that opposes housing sidewall  12 W. For example, trace  70 - 1  may extend substantially parallel to trace  70 - 3  whereas trace  70 - 2  extends substantially perpendicular to traces  70 - 1  and  70 - 3 . Trace  70 - 2  may be separated from housing sidewall  12 W by gap  116  and may, if desired, extend substantially parallel to housing sidewall  12 W. In the example of  FIG. 6 , trace  70 - 2  is longer than trace  70 - 1  and trace  70 - 3  is longer than trace  70 - 2 . This example is merely illustrative and, in general, traces  70 - 1 ,  70 - 2 , and  70 - 3  may have any desired relative lengths, shapes, relative orientations, and perimeters. 
     During operation, currents in structure L 1  may circulate within structure L 1  as indicated by loop I 1  (e.g., current I 1  may flow between feed terminals  54  and  56  over conductive portions  70 - 1 ,  70 - 2 ,  70 - 3 , and  70 - 4  in a loop pattern). Feed element L 1  may be separated from conductor  72 - 1  of distributed loop antenna resonating element L 2  by gap  114 . Gap  114  may be, for example, small enough to ensure satisfactory near field coupling between feed element L 1  and resonating element L 2  (e.g., as shown by coupling  78  in  FIG. 4 ). If desired, gap  114  may be dimensioned to allow conductors  70 - 2  and  72 - 1  to exhibit a desired parasitic capacitance  104  (e.g., to optimize antenna efficiency and bandwidth). Gap  114  may have the same width between trace  70 - 2  and conductor  72 - 1  as between trace  70 - 3  and conductor  72 - 1 . In another suitable arrangement, the width of gap  114  between trace  70 - 2  and conductor  72 - 1  may be different than between trace  70 - 3  and conductor  72 - 1 . Gap  115  may have a uniform width across its length or may have varying widths. By near field coupling feed element L 1  to resonating element L 2 , currents I 1  that are directly fed onto element L 1  may induce currents I 2  to flow on resonating element L 2 . Currents I 2  induced on resonating element L 2  may flow through conductor  72 - 1 , the rear metal wall of housing  12 , and through housing sidewall  12 W at portion  72 - 1 . Currents I 1  and I 2  may resonate with high efficiency to transmit and receive wireless radio-frequency signals for antenna  44  in one or more frequency bands. 
     Conductor  72 - 1  of distributed loop antenna resonating element L 2  may be separated from housing sidewall  12 W (e.g., from portion  72 - 2  of element L 2 ) by gap  100 . Gap  100  may extend from an end of gap  114  adjacent to feed segment  70 - 3  to the end of antenna  44  adjacent to end  95  of substrate  90 . Gap  100  may be smaller than gap  116 , for example. Gap  100  interposed in the loop of structure L 2  may establish a desired capacitance within the loop of structure L 2  (e.g., gap  100  may establish capacitance C of  FIG. 4 ). By distributing gap  100  between conductor  72 - 1  and housing  12 W across the width of element L 2 , current hotspots along the length of element L 2  may be reduced (e.g., current I 2  may spread evenly across the width of element L 2 ). This may reduce the likelihood of emitting excessive signal radiation into the body of a user of device  10  (e.g., thereby satisfying requirements on the absorption of electromagnetic energy by the body of a user of wireless electronic devices). This may also reduce the sensitivity of antenna  44  to detuning or other effects caused by the presence of a user&#39;s body near or in contact with the side of housing  12 . 
     Gap  100  between conductor  72 - 1  and housing sidewall  12 W and gap  114  between feed conductor  70  and conductor  72 - 1  may, for example, form a continuous slot structure (e.g., an open slot structure having a first open end adjacent to side  97  defined by conductor  70 - 2  and conductor  72 - 1  and a second open end adjacent to side  95  defined by conductor  72 - 1  and sidewall  12 W). In general, the continuous slot defined by gaps  114  and  100  may have any desired shape. 
     The overall size (e.g., resonant length) of elements L 1  and L 2  may determine the minimum frequency achievable by antenna  44 . For example, larger sizes for elements L 1  and L 2  may support longer resonating wavelengths and thus lower resonating frequencies than smaller sizes for elements L 1  and L 2 . If desired, capacitor  98  may be coupled between feed element L 1  and distributed loop antenna element L 2 . For example, capacitor  98  may have a first terminal  94  coupled to conductive structure  70 - 3  and a second terminal  96  coupled to conductor  72 - 1 . Capacitor  98  may be, for example, a discrete capacitor such as a surface mounted capacitor, or any other desired capacitive component. Capacitor  98  may have a selected capacitance C 1 . As an example, capacitance C 1  may be 0.6 pF, between 0.3 pF and 0.9 pF, greater than 0.9 pF, less than 0.3 pF, or any other desired capacitance. The particular value of capacitance C 1  may depend on the frequency band of interest. 
     Capacitor  98  may serve to shift the resonant frequency of antenna  44  to a lower frequency than would otherwise be possible given the physical length of elements L 1  and L 2  (e.g., to a resonant frequency that is less than the minimum possible resonant frequency allowed by the dimensions of L 1  and L 2 ). For example, the frequency of antenna  44  may be inversely proportional to the capacitance between feed element L 1  and distributed loop L 2 . Forming capacitor  98  in gap  114  may increase the capacitance between elements L 1  and L 2 , thereby decreasing the frequency of antenna  44  to a lower frequency than would otherwise be possible given the size of elements L 1  and L 2 . In this way, forming capacitor  98  may allow the size of elements L 1  and/or L 2  to be reduced, while still maintaining a desired frequency of operation. This may allow the size of antenna  44  and thus width W′ to be further reduced, thereby maximizing the possible size of active display area AA in device  10  without sacrificing antenna performance at a desired communications frequency. 
     The example of  FIG. 6  is merely illustrative. In general, conductor  72 - 1  may have any desired shape, perimeter, or size. Gap  100  may have a meandering shape or any other desired shape (e.g., as defined by the shape of the lower edge of conductor  72 - 1 ). If desired, more than one capacitor  98  may be coupled between feed loop L 1  and resonating element loop L 2 . Capacitor  98  may, if desired, be a switchable capacitor that is switched into or out of use. Capacitor  98  may be connected between trace  70 - 3  and conductor  72 - 1  at other locations across gap  114 . If desired, capacitor  98  may be coupled between trace  70 - 2  and conductor  72 - 1  or between trace  70 - 1  and conductor  72 - 1 . In the example of  FIG. 6 , speaker driver  64  is placed within dielectric carrier  90  at an opposing side from feed L 1  (e.g., driver  64  is located adjacent to side  95  whereas feed L 1  is adjacent to side  97 ). This may minimize interference between driver  64  and feed L 1 , for example. However, in general, speaker driver  64  may be placed at any desired location within carrier  90 . 
     If desired, a similar structure to that shown in  FIG. 6  may be used to form antenna  44 R of  FIG. 5 . In the example of  FIG. 6 , element L 1  is adjacent to side  97  whereas element L 2  is adjacent to side  95  of carrier  90 . If desired, element L 1  may be formed adjacent to side  95  whereas element L 2  is formed adjacent to side  97  (e.g., the arrangement shown in  FIG. 6  may be mirrored about the y-axis) or element L 1  may be formed at any other desired location along the length of antenna  44  (e.g., along the x-dimension of  FIG. 6 , so long as element L 1  is separated from element L 2  by gap  114 ). In the example of  FIG. 6 , conductor  72 - 1  of distributed loop element L 2  may extend to side  97  of carrier  97  (e.g., so that the entire length of segment  70 - 2  is separated from conductor  72 - 1  by gap  114 ). If desired, conductor  72 - 1  may extend parallel to only a portion of segment  70 - 2  or may extend past segment  70 - 2 . In the example of  FIG. 6 , feed element L 1  is arranged in a half-loop configuration (e.g., a loop configuration where a portion of the loop is formed using grounded housing structures  12 ). In general, feeding element L 1  may have any desired configuration (e.g., element L 1  may be an inverted-F element, monopole element, dipole element, full loop element, or any other desired element that is formed at least partially from housing  12  and that indirectly feeds element L 2 ). In an example where element L 1  is an inverted-F element, the ground plane of the inverted-F element may be formed from housing portion  70 - 4  of sidewall  12 W. Two or more of segments  70 - 1 ,  70 - 2 , and  70 - 3  of feed element L 1  may each have the same width, or each of segments  70 - 1 ,  70 - 2 , and  70 - 3  may have different respective widths. The width of segments  70 - 1 ,  70 - 2 , and  70 - 3  may be the same as or less than the width (thickness) of housing sidewall  12 W. 
       FIG. 7  is a cross-sectional side view of a portion of electronic device  10  (e.g., taken along line TT′ of  FIG. 6 ) showing how distributed loop antenna resonating element L 2  may include a portion of metal housing  12 . As shown in  FIG. 7 , electronic device  10  may have a display such as display  14  that has an associated display module  140  and display cover layer  138 . Display module  140  may be a liquid crystal display module, an organic light-emitting diode display, or other display for producing images for a user. Display module  140  may include touch sensitive components in scenarios where display  14  is a touch-sensitive display, for example. Display cover layer  138  may be a clear sheet of glass, a transparent layer of plastic, or other transparent member. If desired, display cover layer  138  may form a portion of display module  138 . 
     In active area AA, an array of display pixels associated with display structures such as display module  140  may present images to a user of device  10 . In inactive display border region IA, the inner surface of display cover layer  138  may be coated with a layer of black ink or other opaque masking layer  136  to hide internal device structures from view by a user. Antenna  44  may be mounted within housing  12  under opaque masking layer  136 . During operation, antenna signals may be transmitted and received through a portion display cover layer  138 . Forming antenna  44  under inactive region IA of display  14  may allow antenna  44  to transmit and receive radio-frequency signals through display cover layer  138  without the signals being blocked or otherwise impeded by active circuitry in display module  140 . Other components  142  may be formed within housing  12  (e.g., components such as printed circuit boards, transceiver circuitry for antenna  44 , any other desired components used for implementing storage and processing circuitry  22  and/or input-output circuitry  24  ( FIG. 2 ), or any other desired components). 
     As shown in  FIG. 7 , dielectric carrier  90  may be a plastic substrate having a hollow cavity  124 . Cavity  124  may be filled with air or other dielectric materials. Speaker driver  64  may be placed within cavity  124 . Dielectric carrier  90  may have openings  126 . Openings  126  may be aligned with openings  8  in housing sidewall  12 W. Sound produced by speaker driver  64  may pass through opening  126  and opening  8  so that the sound may be heard by a user of device  10 . 
     Housing  12  of device  10  may have a rear housing wall  12 R (e.g., a surface of device  10  that opposes display cover layer  138  may be defined by rear housing wall  12 R). Housing rear wall  12 R and housing sidewall  12 W (or at least the portion of walls  12 R and  12 W that are in contact with dielectric carrier  90 ) may be formed from metal. Housing sidewalls  12 W may extend from rear housing wall  12 R towards display cover layer  138 . Sidewall  93  of dielectric carrier  90  may be substantially or completely covered by housing sidewall  12 W. The top side of housing sidewall  12 W may provide mechanical support for display cover layer  138 . If desired, housing sidewall  12 W may include an inwardly-extending ledge portion  130 . Ledge  130  may support display cover layer  138  (e.g., ledge  130  may enhance the structural support for display cover layer  138  provided by housing sidewall  12 W). Ledge  130  may be formed over or on top surface  99  of dielectric carrier  90 . Ledge  130  may have a width  132 . If desired, ledge  130  may be omitted (e.g., width  132  may be equal to zero mm). 
     Conductive structure  72 - 1  of distributed loop antenna resonating element L 2  may be formed over (e.g., wrapped around) top surface  99  and sidewall  91  of dielectric carrier  90 . In one suitable arrangement, conductive structure  72 - 1  is formed using stamped sheet metal that is placed over sides  99  and  91  of dielectric carrier  90 . If desired, adhesive or other structures may be used to hold conductor  72 - 1  in place on dielectric carrier  90 . Conductive sheet  72 - 1  may be separated from housing sidewall  12 W (e.g., from ledge  130  in scenarios where width  132  is non-zero) by gap  100  (e.g., as shown in  FIG. 6 ). Conductive sheet  72 - 1  may be electrically coupled to (e.g., in direct electrical contact with) housing rear wall  12 R adjacent to side  91  of dielectric carrier  90 . If desired, fastening structures  128  may be used to secure conductive sheet  72 - 1  to housing rear wall  12 R. Fastening structures  128  may ensure that a reliable mechanical and electrical connection is provided between conductive sheet  72 - 1  and housing rear wall  12 R. Fastening structures may be conductive fastening structures such as conductive screws, conductive pins, conductive adhesive, conductive foam structures, conductive tape, solder, welds, or other conductive fastening structures. Multiple fastening structures may be used at multiple points along the length of carrier  90  (e.g., along the x-dimension of  FIG. 6 ) if desired. For example, screws may be placed at regular or irregular intervals along sheet  72 - 1  to mechanically and electrically secure sheet  72 - 1  to rear wall  12 R along the length of antenna  44 . 
     Antenna current I 2  induced on distributed loop antenna resonating element L 2  by feed element L 1  (not shown in  FIG. 7 ) may flow through conductive sheet  72 - 1 , conductive fastener  128 , a portion  72 - 3  of housing rear wall  12 R, and portion  72 - 2  of housing sidewall  12 W (e.g., in a loop through conductive structures  70  of resonating element L 2 ). By forming two of the four sides of loop  70  of distributed loop antenna resonating element L 2  using housing  12  and by forming gap  100  between conductive sheet  72 - 1  and housing sidewall  12 W, antenna  44  may occupy a smaller space within device  10  relative to scenarios where the antenna is separate from housing  12  (e.g., without sacrificing antenna performance at the resonant frequencies of interest). 
     In the example of  FIG. 7 , carrier  90  has a polygonal cross-sectional shape (e.g., side  91 ,  93 ,  99 , and  89  are substantially planar). This is merely illustrative. If desired, some or all of each of sides  91 ,  99 ,  93 , and/or  89  may be curved. In general, sides  89  and  93  of carrier  90  may conform to (e.g., accommodate, extend parallel to, or abut) the shape of housing sidewall  12 W and housing rear wall  12 R. Side  93  of carrier  90  and housing sidewall  12 W may be substantially parallel to side  91  of carrier  90  or side  91  and conductor  72 - 1  may be oriented at a non-parallel angle with respect to side  93  and sidewall  12 W. Similarly, side  99  of carrier  90  (and the top portion of conductor  72 - 1 ) may be substantially parallel to bottom side  89  of carrier  90  and housing rear wall  12 R or conductor  72 - 1  and side  99  may be oriented at a non-parallel angle with respect to side  89  and rear wall  12 R. Side  91  and conductor  72 - 1  may be oriented at a non-zero angle with respect to the z-axis in  FIG. 7  (e.g., at a non-vertical angle) to provide more space to accommodate components  142  and display module  140 , or may be oriented at a vertical angle if desired. The cross section of carrier  90  may have more than four sides if desired. In general, carrier  90 , conductor  72 - 1 , housing sidewall  12 W, and housing rear wall  12 R may have any desired shapes. 
       FIG. 8  is a cross-sectional side view of a portion of electronic device  10  (e.g., as taken along line RR′ of  FIG. 6 ) showing how loop feed element L 1  may include a portion of metal housing  12 . Descriptions of many of the components shown in  FIG. 8  are provided in connection with  FIG. 7  and are not repeated for the sake of brevity. As shown in  FIG. 8 , loop feed element L 1  may include metal trace  70 - 2  and a portion  70 - 4  of housing sidewall  12 W adjacent to top surface  99  of carrier  90 . In scenarios where ledge  130  is formed (e.g., when width  132  is non-zero), ledge  130  may form portion  70 - 4  of loop feed element L 1 . 
     In the example of  FIG. 8 , gap  116  separating trace  70 - 2  and housing portion  70 - 4  may have a width  150 . Width  150  may be greater than width  152  of gap  114  between trace  70 - 2  and metal sheet  72 - 1  (e.g., the stamped metal sheet used to form distributed loop antenna resonating element L 2 ). Width  150  of gap  116  may be greater than width  132  of ledge  130 . This is merely illustrative. If desired, width  150  may be less than or equal to width  152  and/or may be less than or equal to width  132 . 
     Radio-frequency antenna signals are directly fed to feed element L 1  over antenna feed terminals  54  and  56  ( FIG. 6 ). These antenna signals form currents I 1  that flow on conductive loop structures  70  of feed element L 1 . Currents I 1  may induce currents I 2  to flow through distributed loop antenna resonating element L 2  (e.g., through conductor  72 - 1 , portion  72 - 3  of rear wall  12 R, and portion  72 - 2  of sidewall  12 W ( FIG. 7 )). 
       FIG. 9  is a graph showing how capacitor  98  of antenna  44  may affect the performance of antenna  44 . As shown in  FIG. 9 , antenna performance (standing wave ratio) is plotted as a function of frequency. Curve  160  shows how antenna  44  may exhibit a resonance at frequency F 2  in the absence of capacitor  98  (e.g., when capacitor  98  is switched out of use or when capacitor  98  is omitted from antenna  44 ). Curve  162  shows how antenna  44  may exhibit a resonance at frequency F 1  that is lower than frequency F 2  in the presence of capacitor  98  (e.g., when capacitor  98  is switched into use or when capacitor  98  is formed within antenna  44 ). Resonance  160  may, for example, be at least partially determined by the shape (e.g., overall size) of antenna  44 . For example, the size of antenna  44  may provide a lower limit on the possible resonant frequency of antenna  44  (e.g., lower resonances may not be possible without increasing the size of antenna  44 ). However, forming capacitor  98  between feed element conductor  70  and distributed loop antenna resonating element conductor  72 - 1  may effectively shift the resonance of antenna  44  to lower frequency  162  as shown by arrow  164  (e.g., to a frequency lower than what would otherwise be possible given the size of antenna  44 ). 
     As an example, frequency F 2  may be 3.3 GHz. It may be desirable to provide a resonance at 2.4 GHz such as to cover a wireless local area network communications band at 2.4 GHz. However, the size of antenna  44  may make it difficult to achieve such a low frequency resonance (e.g., without undesirably increasing the size of antenna  44  and thus the size of inactive display portion IA). By forming capacitor  98  in antenna  44 , the resonance of antenna  44  may be shifted to a frequency F 1  of 2.4 GHz without the need to increase the physical size or perimeter of antenna  44 . In this way, antenna  44  may cover a desired 2.4 GHz wireless local area network frequency band while having a small size that would otherwise be limited to higher frequencies such as 3.3 GHz. This may allow further reduction to width W′ ( FIG. 6 ) and a corresponding maximization of the size of active display area AA without reducing antenna performance in the frequency band of interest. The example of  FIG. 9  is merely illustrative. In general, any desired frequency bands may be covered by antenna  44 . If desired antenna  44  may simultaneously cover multiple different frequency bands. For example, antenna  44  may resonate in both 2.4 GHz and 5.0 GHz frequency bands (e.g., 2.4 GHz and 5.0 GHz wireless local area network communications bands). 
     In such scenarios, the lower frequency band covered by antenna  44  may sometimes be referred to as a lower frequency band LB (e.g., 2.4 GHz) whereas the higher frequency band covered by antenna  44  may sometimes be referred to as a higher frequency band HB (e.g., 5.0 GHz). During operation, both elements L 1  and L 2  may contribute to the overall performance of antenna structures  44 . For example, at lower frequencies such as frequencies in low band LB, antenna resonating element L 2  may serve as the primary radiating element in structures  44  (e.g., because element L 2  has a much larger size than feeding element L 1 ) whereas antenna resonating element L 1  serves as a secondary radiating element in structures  44 . At higher frequencies such as frequencies in high band HB, antenna feeding element L 1  may serve as the primary radiating element in antenna structures  44  and antenna resonating element L 2  may serve as a secondary radiating element. 
     If desired, antenna feed element L 1  may include additional structures that enhance the efficiency of antenna  44  in a second frequency band (e.g., high band HB).  FIG. 10  is a front view showing how feed element L 1  may include structures for enhancing coverage of a second frequency band for antenna  44 . As shown in  FIG. 10 , antenna feed element L 1  may include an extended conductive segment  70 - 4 . Conductive segment  70 - 4  may extend from segment  70 - 2  (and perpendicularly from an end of directly fed segment  70 - 1 ) adjacent to edge  97  of dielectric carrier  90 . Segment  70 - 4  may adjust the resonant length of feed element L 1  so that element L 1  has increased antenna efficiency in the second band. This may allow element L 1  to efficiently transmit and receive radio-frequency signals for antenna  44  in the second band (e.g., 5.0 GHz) while also serving as a feed element for distributed loop element L 2  (e.g., so that loop L 2  may serve as a primary radiating element in the first frequency band such as 2.4 GHz). 
     The example of  FIG. 10  is merely illustrative. If desired, segment  70 - 4  may extend at any desired angle from segment  70 - 2 . Segment  70 - 4  may have any desired width (e.g., a width that is different from the width of segment  70 - 2 ), any desired perimeter, and any desired shape (e.g., segment  70 - 4  may be polygonal, rectangular, triangular, curved, circular, etc.). Segment  70 - 4  may be formed from a conductive trace, stamped sheet metal, or any other desired conductive structure (e.g., segment  70 - 4  may be an extension of segments  70 - 2  and  70 - 1  or may be formed from a separate conductor that is otherwise conductively connected to segments  70 - 1  and  70 - 2 ). 
     If desired, feeding element L 1  may include filtering circuitry to enhance isolation between radio-frequency signals in the first and second frequency bands. For example, element L 1  may include an additional conductive segment  192 . Segment  192  may be a conductive trace, stamped sheet metal, or any other desired conductor. Segment  192  may be connected to housing sidewall  12 W at point  194 . For example, segment  192  may be soldered to wall  12 W, welded to wall  12 W, formed as an integral extension to wall  12 W, screwed into wall  12 W, taped to wall  12 W, coupled to wall  12 W via conductive adhesive, etc. 
     Capacitor  200  may be coupled between segment  70 - 2  and segment  192 . For example, a first terminal  198  of capacitor  200  may be coupled to segment  70 - 2  whereas a second terminal  196  of capacitor  200  is coupled to an end of segment  192 . Capacitor  200  may have a corresponding capacitance C 2 . Segment  192  and segment  70 - 3  may exhibit desired inductances (e.g., based on the widths and lengths of segments  192  and  70 - 3 ). The inductances of segments  192  and  70 - 3  and the capacitance C 2  of capacitor  200  may be selected to perform desired filtering operations on the antenna signals provided to feed element L 1  over feed terminals  54  and  56 . 
       FIG. 11  is an equivalent circuit diagram of antenna feed L 1  of the type shown in FIG.  10 . As shown in  FIG. 10 , capacitor  200  may be coupled in series with inductor  210  (e.g., an inductor formed by the inductance of segment  192  of  FIG. 10 ) between segment  70 - 2  and ground (e.g., formed from a segment  70 - 4  of housing sidewall  12 W). Inductor  212  may, for example, be formed by the inductance of segment  72 - 3 . Capacitor  98  may be coupled between a portion of inductor  212  (e.g., a terminal  94  on segment  70 - 3 ) and distributed loop antenna resonating element L 2  at terminal  96 . Inductor  212  may be coupled in parallel with the series-connected capacitor  200  and inductor  210  between feed terminal  54  and ground conductor  70 - 4 . When coupled in this way, inductor  212 , inductor  210 , and capacitor  200  may form filter  216  (e.g., a parallel tank circuit or parallel tank filter). 
     The value of capacitances C 1  and C 2  and the corresponding inductances of inductors  210  and  212  may be selected so that filter  216  forms a closed circuit (e.g., a zero impedance path) between feed terminal  54  and ground connections  194  and  92  at a first frequency and an open circuit (e.g., an infinite impedance path) between feed terminal  54  and ground terminals  194  and  92  at a second frequency. For example, filter  216  may form an open circuit at a high band frequency in high band HB (e.g., at 5.0 GHz) so that currents I 1  at the high band frequency does not pass to through ground connections  92  and  194 . This may disrupt the loop path formed by currents I 1  at the high band frequency, thereby reducing near field coupling between element L 1  and distributed loop L 2  at the high band frequency. Segment  70 - 4  may exhibit a resonance at the high band frequency to transmit and receive radio-frequency signals at the high band frequency. If desired, the shape and perimeter of segment  70 - 4  may be selected to provide the desired resonance (e.g., segment  70 - 4  may affect the tuning characteristics of antenna  44  at the high band frequency). 
     Filter  216  may form a closed circuit at a low band frequency in low band LB (e.g., at 2.4 GHz) so that currents I 1  at the low band frequency are shorted to ground (housing) segment  70 - 4  at locations  92  and  194 . This may maintain a loop path for current I 1 , thereby providing high efficiency near field coupling between element L 1  and element L 2  at the low band frequency (e.g., so that element L 1  may serve as an indirect feeding element to distributed loop element L 2  that induces current I 2  to flow in distributed loop element L 2  at the low band frequency). The example of  FIGS. 10 and 11  is merely illustrative. In general, any desired filtering circuitry may be used. If desired, filter  216  may be omitted (e.g., as shown in  FIG. 6 ). 
       FIG. 12  is a graph in which antenna performance (standing wave ratio) for antenna structures such as antenna  44  of  FIGS. 6-11  has been plotted as a function of operating frequency. In the example of  FIG. 12 , antenna  44  has been configured to resonate in a lower frequency band LB and a higher frequency band HB. Communications bands LB and HB may be cellular telephone bands, satellite navigation system bands, local area network bands, and/or other suitable communications bands. As an example, low band LB may centered around a low band frequency F 3  and may be associated with a 2.4 GHz wireless local area network band. High band HB may be centered around a high band frequency F 4  and may be associated with a 5.0 GHz wireless local area network band (as an example). 
     Dashed curve  220  of  FIG. 12  corresponds to the contribution of distributed loop antenna resonating element L 1  to the performance of antenna  44 . Dashed-and-dotted curve  222  corresponds to the contribution of loop antenna resonating (feed) element L 2  to the performance of antenna structures  44 . During operation, both elements L 1  and L 2  contribute to the overall performance of antenna  44 , represented by curve  224 . At lower frequencies such as frequencies in low band LB, antenna resonating element L 2  serves as the primary radiating element in antenna  44  and antenna resonating element L 1  serves as a secondary radiating element in antenna  44 . At higher frequencies such as frequencies in high band HB, antenna resonating element L 1  serves as the primary radiating element in antenna  44  and antenna resonating element L 2  serves as a secondary radiating element. In this way, antenna  44  may transmit and receive signals in both low band LB and high band HB (e.g., 2.4 GHz and 5.0 GHz bands). When element L 1  is provided with extension  70 - 4  ( FIGS. 10 and 11 ), antenna  44  may be provided with greater efficiency in high band HB than in scenarios where extension  70 - 4  is not formed, for example. If desired, capacitor  98  may shift frequency F 3  of curve  224  to a lower frequency than would otherwise be feasible given the size of antenna  44  (e.g., as described in connection with  FIG. 9 ). 
       FIG. 13  is a graph showing how antenna efficiency varies as a function of frequency for different antenna configurations within device  10 . Curve  232  illustrates the efficiency of an antenna in region  20  ( FIG. 1 ) when implemented using a cavity-backed inverted-F antenna that is separate from housing  12 . Such an arrangement may occupy a first inactive area width W ( FIG. 5 ) such as 12 mm. The efficiency of the antenna in this configuration may peak at a level E 2  at resonant frequency F (e.g., 2.4 GHz or 5.0 GHz). As the width W is reduced (e.g., to maximize the size of active display area AA), the antenna efficiency decreases. Curve  234  illustrates the efficiency of a cavity-backed inverted-F antenna that is separate from housing  12  when contained within a second width that is narrower than the first width (e.g., a width of 9 mm). The efficiency of the antenna in this configuration may peak at a level E 3  at frequency F that is less than peak efficiency E 2  of configuration  232 . While the active area AA of display  14  is greater in this scenario, the peak antenna efficiency E 3  may be less than a minimum acceptable antenna efficiency threshold associated with device  10 . 
     Curve  230  illustrates the efficiency of antenna  44  having a configuration of the type shown in  FIGS. 1-12  (e.g., in which feed element L 1  and distributed loop element L 2  both include portions of conductive housing  12 ). Such an arrangement may occupy a width W′ that is less than the first width associated with curve  232 . For example, width W′ may be the same as the width associated with curve  232  (e.g., 9 mm) or any other desired width. However, the efficiency of antenna  44  in this configuration may peak at level E 1  at frequency F that is greater than peak efficiencies E 2  and E 3 . Similarly, antenna  44  may exhibit greater efficiency bandwidth (e.g., corresponding to a horizontal width of curve  232 ) than antenna configurations  232  and  234 . In this way, antenna  44  may occupy a minimal amount of space within device  10  while still exhibiting an optimal (e.g., maximum) antenna efficiency E 1 , thereby minimizing the size of inactive area IA of display  14  and maximizing the size of active area AA of display  14  (e.g., without sacrificing antenna performance at the frequency of interest F). The example of  FIG. 13  is merely illustrative. In general, antenna  44  may exhibit any desired antenna efficiency (e.g., an efficiency that exceeds a minimum acceptable antenna efficiency threshold) while occupying a minimal amount of space within device  10 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20160923
Publication Date: 20190507
Grant Date: 20190507
Priority Date: 20160923
Inventors: RAJAGOPALAN, HARISH
ROMANO, Pietro
GOMEZ ANGULO, RODNEY A.
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q7/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2291", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q7/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2291", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61685751