PATENT DOCUMENT

Publication Number: US-10490881-B2
Application Number: US-201615066419-A
Country: US
Kind Code: B2

Title: Tuning circuits for hybrid electronic device antennas

Abstract:
An electronic device may have hybrid antennas that include slot antenna resonating elements formed from slots in a ground plane and planar inverted-F antenna resonating elements. The planar inverted-F antenna resonating elements may each have a planar metal member that overlaps one of the slots. A return path and feed may be coupled in parallel between the planar metal member and the ground plane. Adjustable circuits such as tunable inductors may be used to tune the hybrid antennas. Adjustable circuits may bridge the slots in hybrid antennas and may be included in return paths that are coupled between the planar metal members of the planar inverted-F antenna resonating elements and the ground plane. A slot may be selectively divided to from two slots using switching circuitry.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having a metal housing wall that forms a ground plane; 
 a slot in the metal housing wall that forms a slot antenna resonating element for a hybrid antenna; 
 a planar inverted-F antenna resonating element for the hybrid antenna; 
 an antenna feed having a positive antenna feed terminal and a ground antenna feed terminal coupled between the planar inverted-F antenna resonating element and the ground plane; and 
 a return path coupled between the planar inverted-F antenna resonating element and the ground plane in parallel with the antenna feed, wherein the return path includes an adjustable circuit; and 
 an additional adjustable circuit that bridges the slot. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the adjustable circuit comprises an adjustable inductor. 
     
     
       3. The electronic device defined in  claim 2  wherein the adjustable inductor comprises a plurality of inductors and switching circuitry. 
     
     
       4. The electronic device defined in  claim 3  further comprising control circuitry that is configured to tune an antenna resonance for the hybrid antenna by adjusting the additional adjustable circuit that bridges the slot. 
     
     
       5. The electronic device defined in  claim 4  wherein the control circuitry is configured to adjust the adjustable inductor to compensate for the presence of an external object adjacent to the slot. 
     
     
       6. The electronic device defined in  claim 1  further comprising:
 first and a second additional adjustable circuit, wherein the additional adjustable circuit and the second additional adjustable circuit that bridge the slot on opposing sides of the ground antenna feed terminal. 
 
     
     
       7. The electronic device defined in  claim 6  wherein the first additional and second additional adjustable circuits each include switching circuitry and at least one inductor. 
     
     
       8. The electronic device defined in  claim 7  wherein the first additional and second additional adjustable circuits each include a capacitor coupled in series with the at least one inductor. 
     
     
       9. The electronic device defined in  claim 8  wherein the adjustable circuit of the return path comprises an adjustable inductor. 
     
     
       10. The electronic device defined in  claim 9  wherein the adjustable inductor of the return path includes at least three inductors and switching circuitry coupled to the at least three inductors. 
     
     
       11. The electronic device defined in  claim 10  wherein the ground plane has first and second ground plane portions on opposing sides of the slot and wherein the return path and the ground antenna feed terminal are both coupled to the first ground plane portion. 
     
     
       12. The electronic device defined in  claim 1  further comprising:
 a transmission line coupled to the antenna feed, wherein the transmission line includes an adjustable component that is adjusted to tune the antenna. 
 
     
     
       13. The electronic device defined in  claim 1 , wherein the planar inverted-F antenna resonating element overlaps only a portion of the slot. 
     
     
       14. An electronic device, comprising:
 a metal housing that forms a ground plane, wherein the metal housing has a dielectric-filled slot that separates the metal housing into first and second portions and that is divided into first and second slots by at least one switch that bridges the slot, and the at least one switch is configured to form a conductive path that electrically shorts the first portion of the metal housing to the second portion of the metal housing in a mode of operation; 
 a first hybrid antenna that includes:
 a first slot antenna resonating element formed from the first slot; 
 a first planar inverted-F antenna resonating element that indirectly feeds the first slot antenna; and 
 
 a second hybrid antenna that includes:
 a second slot antenna resonating element formed from the second slot; 
 a second planar inverted-F antenna resonating element that indirectly feeds the second slot antenna. 
 
 
     
     
       15. The electronic device defined in  claim 14  further comprising:
 a return path having a tunable inductor that is coupled between the first planar inverted-F antenna resonating element and the ground plane. 
 
     
     
       16. The electronic device defined in  claim 15  further comprising a tunable component that bridges the slot, wherein the tunable component includes switching circuity, inductors coupled to the switching circuitry, and capacitors coupled to the switching circuitry in parallel with the inductors. 
     
     
       17. The electronic device defined in  claim 15  wherein the at least one switch comprises a plurality of switches that bridge the slot. 
     
     
       18. An antenna, comprising:
 a metal electronic device housing wall; 
 a slot in the metal electronic device housing wall, wherein the slot divides the metal electronic device housing wall into first and second portions that are respectively located on opposing first and second sides of the slot; 
 a planar inverted-F antenna resonating element that has a planar metal element, a return path formed on the first side of the slot and coupled between the planar metal element and the first portion of the metal electronic device housing wall, and an antenna feed having a positive antenna feed terminal on the first side of the slot and a ground antenna feed terminal on the first side of the slot coupled respectively to the planar metal element and the first portion of the metal electronic device housing wall; and 
 a tunable circuit containing a capacitor that bridges the slot. 
 
     
     
       19. The antenna defined in  claim 18  wherein the tunable circuit includes switching circuitry to which the capacitor is coupled and includes a plurality of inductors coupled to the switching circuitry. 
     
     
       20. The antenna defined in  claim 19  further comprising a tunable inductor in the return path. 
     
     
       21. The electronic device defined in  claim 14  wherein the metal housing comprises a rear wall of the housing, the electronic device further comprising:
 a dielectric layer at a front of the housing, wherein the first planar inverted-F antenna resonating element is separated from the second planar inverted-F antenna resonating element by a gap, the first and second planar inverted-F antenna resonating elements are interposed between the dielectric layer and the rear wall.

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. 
     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 ground plane may, for example, be formed from a rear housing wall and sidewalls. The ground plane and other structures in the electronic device may be used in forming antennas. 
     The electronic device may include one or more hybrid antennas. The hybrid antennas may each include a slot antenna resonating element formed from a slot in the ground plane and a planar inverted-F antenna resonating element. The planar inverted-F antenna resonating element may serve as indirect feed structure for the slot antenna resonating element. 
     A planar inverted-F antenna resonating element may have a planar metal member that overlaps one of the slot antenna resonating elements. The slot of the slot antenna resonating element may divide the ground plane into first and second portions. A return path and feed may be coupled in parallel between the planar metal member and the first portion of the ground plane. The return path may include a tunable component. For example, the return path may include an adjustable inductor formed from inductors and switching circuitry. 
     A set of one or more switches may bridge a dielectric-filled slot in the metal housing and thereby form first and second slots for first and second hybrid antennas. During normal operation, the switches may be closed to form the first and second slots. When antenna operation is influenced by external objects adjacent to one of the antennas, the switches may be opened. This joins the first and second slots together and forms a single larger slot that is open at each end and less sensitive to influence to from external objects. 
     Tunable components such as tunable inductors may be used to tune the hybrid antennas. A tunable inductor may bridge the slot in a hybrid antenna, may be coupled between the planar metal member of the planar inverted-F antenna resonating element and the ground plane, or multiple tunable inductors may bridge the slot on opposing sides of the planar inverted-F antenna resonating element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a rear perspective view of a portion of the illustrative electronic device of  FIG. 1  in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative electronic device in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 5  is a diagram of illustrative wireless circuitry in an electronic device in accordance with an embodiment. 
         FIG. 6  is a perspective interior view of an illustrative electronic device with a metal housing having a dielectric-filled slot such as a plastic-filled slot that has been divided into left and right slots for hybrid planar inverted-F-slot antennas by a conductive structure that bridges the slot in accordance with an embodiment. 
         FIG. 7  is a graph of antenna performance (standing wave ratio SWR) plotted as a function of operating frequency for an illustrative antenna of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIGS. 8, 9, 10, and 11  are diagrams of illustrative adjustable circuitry for tuning antenna performance for antennas of the type shown in  FIG. 6  in accordance with embodiments. 
         FIG. 12  is a perspective view of an illustrative hybrid antenna with a return path that includes an adjustable circuit such as an adjustable inductor having switching circuitry coupled to three inductors 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 antenna structures. The antenna structures may include hybrid antennas. The hybrid antennas may be hybrid planar-inverted-F-slot antennas that include slot antenna resonating elements and planar inverted-F antenna resonating elements. The planar inverted-F antenna resonating elements may indirectly feed the slot antenna resonating elements and may contribute to the frequency responses of the antennas. Slots for the slot antenna resonating elements may be formed in ground structures such as conductive housing structures and may be filled with a dielectric such as plastic. 
     The wireless circuitry of device  10  may handles 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  has been 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.). 
     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 include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display 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 or clear plastic. 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 may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.). Openings in housing  12  may also be formed for audio components such as a speaker and/or a microphone. 
     Antennas may be mounted in housing  12 . For example, housing  12  may have four peripheral edges 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 slots in the rear of housing  12  in regions such as regions  20  and may emit and receive signals through the front of device  10  (i.e., through inactive portions of display  14 ) and/or through the rear of device  10 . Antennas may also be mounted in other portions of device  10 , if desired. The configuration of  FIG. 1  is merely illustrative. 
       FIG. 2  is a rear perspective view of the upper end of housing  12  and device  10  of  FIG. 1 . As shown in  FIG. 2 , one or more slots such as slot  122  may be formed in housing  12 . Housing  12  may be formed from a conductive material such as metal. Slot  122  may be an elongated opening in the metal of housing  12  and may be filled with a dielectric material such as glass, ceramic, plastic, or other insulator (i.e., slot  122  may be a dielectric-filled slot). The width of slot  122  may be 0.1-1 mm, less than 1.3 mm, less than 1.1 mm, less than 0.9 mm, less than 0.7 mm, less than 0.5 mm, less than 0.3 mm, more than 0.2 mm, more than 0.5 mm, more than 0.1 mm, 0.2-0.9 mm, 0.2-0.7 mm, 0.3-0.7 mm, or other suitable width. The length of slot  122  may be more than 4 cm, more than 6 cm, more than 10 cm, 5-20 cm, 4-15 cm, less than 15 cm, less than 25 cm, or other suitable length. 
     Slot  122  may extend across rear housing wall  12 R and, if desired, an associated sidewall such as sidewall  12 W. Rear housing wall  12 R may be planar or may be curved. Sidewall  12 W may be an integral portion of rear wall  12 R or may be a separate structure. Housing wall  12 R (and, if desired, sidewalls such as sidewall  12 W) may be formed from aluminum, stainless steel, or other metals and may form a ground plane for device  10 . Slots in the ground plane such as slot  122  may be used in forming antenna resonating elements. 
     In the example of  FIG. 2 , slot  122  has a U-shaped footprint (i.e., the outline of slot  122  has a U shape when viewed along dimension Z). Other shapes for slot  122  may be used, if desired (e.g., straight shapes, shapes with curves, shapes with curved and straight segments, etc.). With a layout of the type shown in  FIG. 2 , the bends in slot  122  create space along the left and right edges of housing  12  for components  126 . Components  126  may be, for example, speakers, microphones, cameras, sensors, or other electrical components. 
     Slot  122  may be divided into two shorter slots using a conductive member such as conductive structure  124  or a set of one or more switches that can be controlled by a control circuit. Conductive structure  124  may be formed from metal traces on a printed circuit, metal foil, metal portions of a housing bracket, wire, a sheet metal structure, or other conductive structure in device  10 . Conductive structure  124  may be shorted to metal housing wall  12 R on opposing sides of slot  122 . If desired, conductive structures such as conductive structure  124  may be formed from integral portions of metal housing  12  and/or adjustable circuitry that bridges slot  122 . 
     In the presence of conductive structure  124  (or when switches in structure  124  are closed), slot  122  may be divided into first and second slots  122 L and  122 R. Ends  122 - 1  of slots  122 L and  122 R are surrounded by air and dielectric structures such as glass or other dielectric associated with a display cover layer for display  14  and are therefore sometimes referred to as open slot ends. Ends  122 - 2  of slots  122 L and  122 R are terminated in conductive structure  124  and therefore are sometimes referred to as closed slot ends. In the example of  FIG. 2 , slot  122 L is an open slot having an open end  122 - 1  and an opposing closed end  122 - 2 . Slot  122 R is likewise an open slot. If desired, device  10  may include closed slots (e.g., slots in which both ends are terminated with conductive structures). The configuration of  FIG. 2  is merely illustrative. 
     Slot  122  may be fed using an indirect feeding arrangement. With indirect feeding, a structure such as a planar-inverted-F antenna resonating element may be near-field coupled to slot  122  and may serve as an indirect feed structure. The planar inverted-F antenna resonating element may also exhibit resonances that contribute to the frequency response of the antenna formed from slot  122  (i.e., the antenna may be a hybrid planar-inverted-F-slot antenna). 
     A cross-sectional side view of device  10  in the vicinity of slot  122  is shown in  FIG. 3 . In the example of  FIG. 3 , conductive structures  36  may include display  14 , conductive housing structures such as metal rear housing wall  12 R, etc. Dielectric layer  24  may be a portion of a glass layer (e.g., a portion of a display cover layer for protecting display  14 ). The underside of layer  24  may, if desired, be covered with an opaque masking layer to block internal components in device  10  from view. Dielectric support  30  may be used to support conductive structures such as metal structure  22 . Metal structure  22  may be located under dielectric layer  24  and may, if desired, be used in forming an antenna feed structure (e.g., structure  22  may be a planar metal member that forms part of a planar inverted-F antenna resonating element structure that is near-field coupled to slot  122  in housing  12 ). During operation, antenna signals associated with an antenna formed from slot  122  and/or metal structure  22  may be transmitted and received through the front of device  10  (e.g., through dielectric layer  24 ) and/or the rear of device  10 . 
     A schematic diagram showing illustrative components that may be used in device  10  is shown in  FIG. 4 . As shown in  FIG. 4 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  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  28  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  28  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  28  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  44  may include input-output devices  32 . Input-output devices  32  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  32  may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, motion sensors (accelerometers), capacitance sensors, proximity sensors, etc. 
     Input-output circuitry  44  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications 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, 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  34  may include radio-frequency transceiver circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  36  may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  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  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  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  34  may include satellite navigation system circuitry such as global positioning system (GPS) receiver circuitry  42  for receiving GPS signals at 1575 MHz 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  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  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, 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. 5 , transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  92 . Wireless circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures  40  with the ability to cover communications frequencies of interest, antenna structures  40  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  40  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. Tunable components  102  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  28  may issue control signals on one or more paths such as path  104  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 5  may be a transmission line having first and second conductive paths such as paths  94  and  96 , respectively. Path  94  may be a positive signal line and path  96  may be a ground signal line. Lines  94  and  96  may form parts of a coaxial cable or a microstrip transmission line (as examples). A matching network formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna structures  40  to the impedance of transmission line  92 . 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  40 . 
     Transmission line  92  may be directly coupled to an antenna resonating element and ground for antenna  40  or may be coupled to near-field-coupled antenna feed structures that are used in indirectly feeding a resonating element for antenna  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Positive transmission line conductor  94  may be coupled to positive antenna feed terminal  98  and ground transmission line conductor  96  may be coupled to ground antenna feed terminal  92 . Antenna structures  40  may include an antenna resonating element such as a slot antenna resonating element or other element that is indirectly fed using near-field coupling. In a near-field coupling arrangement, transmission line  92  is coupled to a near-field-coupled antenna feed structure that is used to indirectly feed antenna structures such as an antenna slot or other element through near-field electromagnetic coupling. 
     Antennas  40  may include hybrid antennas formed both from inverted-F antenna structures (e.g., planar inverted-F antenna structures) and slot antenna structures. An illustrative configuration in which device  10  has two hybrid antennas formed from the left and right portions of slot  122  in housing  12  is shown in  FIG. 6 .  FIG. 6  is an interior perspective view of device  10  at the upper end of housing  12 . As shown in  FIG. 6 , slot  122  may be divided into left slot  122 L and right slot  122 R by conductive structures  124  that bridge the center of slot  122 . Rear housing wall  12 R (e.g., a metal housing wall in housing  12 ) may have a first portion such as portion  12 R- 1  and a second portion such as portion  12 R- 2  that is separated from portion  12 R- 1  by slot  122 . Conductive structures  124  may be shorted to rear housing wall portion  12 R- 1  on one side of slot  122  and may be shorted to rear housing wall portion  12 R- 2  on the other side of slot  122 . The presence of the short circuit formed by structures  124  across slot  122  creates closed ends  122 - 2  for left slot  122 L and right slot  122 R. 
     Antennas  40  of  FIG. 6  include left antenna  40 L and right antenna  40 R. Device  10  may switch between antennas  40 L and  40 R in real time to ensure that signal strength is maximized, may use antennas  40 L and  40 R simultaneously, or may otherwise use antennas  40 L and  40 R to enhance wireless performance for device  10 . 
     Left antenna  40 L and right antenna  40 R may be hybrid planar-inverted-F-slot antennas each of which has a planar inverted-F antenna resonating element and a slot antenna resonating element. 
     The slot antenna resonating element of antenna  40 L may be formed by slot  122 L. Planar-inverted-F resonating element  130 L serves as an indirect feeding structure for antenna  40 L and is near-field coupled to the slot resonating element formed from slot  122 L. During operation, slot  122 L and element  130 L may each contribute to the overall frequency response of antenna  40 L. As shown in  FIG. 6 , antenna  40 L may have an antenna feed such as feed  136 L. Feed  136 L is coupled between planar inverted-F antenna resonating element  130 L and ground (i.e., metal housing  12 R- 1 ). A transmission line (see, e.g., transmission line  92  of  FIG. 5 ) may be coupled between transceiver circuitry  90  and antenna feed  136 L. Feed  136 L has positive antenna feed terminal  98 L and ground antenna feed terminal  100 L. Ground antenna feed terminal  100 L may be shorted to ground (e.g., metal wall  12 R- 1 ). Positive antenna feed terminal  98 L may be coupled to planar metal element  132 L via a leg or other conductive path that extends downwards from planar-inverted-F antenna resonating element  130 L towards the ground formed from metal wall  12 R- 1 . Planar-inverted-F antenna resonating element  130 L may also have a return path such as return path  134 L that is coupled between planar element  132 L and antenna ground (metal housing  12 R- 1 ) in parallel with feed  136 L. 
     The slot antenna resonating element of antenna  40 R is formed by slot  122 R. Planar-inverted-F resonating element  130 R serves as an indirect feeding structure for antenna  40 R and is near-field coupled to the slot resonating element formed from slot  122 R. Slot  122 R and element  130 R both contribute to the overall frequency response of hybrid planar-inverted-F-slot antenna  40 R. Antenna  40 R may have an antenna feed such as feed  136 R. Feed  136 R is coupled between planar inverted-F antenna resonating element  130 R and ground (metal housing  12 R- 1 ). A transmission line such as transmission line  92  may be coupled between transceiver circuitry  90  and antenna feed  136 R. Feed  136 R may have positive antenna feed terminal  98 R and ground antenna feed terminal  100 R. Ground antenna feed terminal  100 R may be shorted to ground (e.g., metal wall  12 R- 1 ). Positive antenna feed terminal  98 R may be coupled to planar metal structure  132 R of planar-inverted-F antenna resonating element  130 R. Planar-inverted-F antenna resonating element  130 R may have a return path such as return path  134 R that is coupled between planar element  132 R and antenna ground (metal housing  12 R- 1 ). 
     Return paths  134 L and  134 R may be formed from strips of metal without any tunable components or may include tunable inductors or other adjustable circuits for tuning antennas  40 . Additional tunable components may also be incorporated into antennas  40 , if desired. For example, tunable (adjustable) components  140 L and  142 L may bridge slot  122 L in antenna  40 L and tunable (adjustable) components  140 R and  142 R may bridge slot  122 R in antenna  40 R. 
     Antennas  40  may support any suitable frequencies of operation. As an example, antennas  40  may operate in a low band LB, midband MB, and high band HB, as shown in the graph of  FIG. 7  in which antenna performance (standing wave ratio SWR) has been plotted as a function of operating frequency f. Slots  122 L and  122 R may have lengths (quarter wavelength lengths) that support resonances in low communications band LB (e.g., a low band at frequencies between 700 and 960 MHz). Midband coverage (e.g., for a midband MB from 1400 or 1500 MHz to 1.9 GHz or other suitable midband range) may be provided by the resonance exhibited by planar inverted-F antenna resonating elements  130 L and  130 R. High band coverage (e.g., for a high band centered at 2400 MHz and extending to 2700 MHz or other suitable frequency) may be supported using harmonics of the slot antenna resonating element resonance (e.g., a third order harmonic, etc.). 
     Tuning circuits (see, e.g., components  102  of  FIG. 5 ) may be used in adjusting antenna frequency response. Illustrative antenna tuning circuitry for antennas  40  is shown in  FIGS. 8, 9, 10, and 11 . The adjustable circuits for antenna tuning that are shown in  FIGS. 8 and 9  may include capacitors that can bridge slot  122 . This may help allow the width of conductive structure  124  to be widened to improve isolation between antennas  40 L and  40 R without overly increasing the frequency of operation of antennas  40 L and  40 R due to the resulting decrease in the lengths of slots  122 L and  122 R. Switchable inductors in these circuits may help tune antenna resonance peaks to cover frequencies of interest. 
     Tunable circuitry such as tunable circuit  140  of  FIG. 8  may be used for implementing tunable circuit  140 L and/or tunable circuit  140 R of  FIG. 6 . Tunable circuit  140  includes first terminal  160  and second terminal  162 . Two respective branches of circuitry each having different circuit components may be coupled between terminals  160  and  162  in parallel. Switches SW 1  and SW 2  may be turned on or off to switch the circuitry of circuit  140  into or out of use. In the illustrative configuration of  FIG. 8 , a capacitor C 1  (i.e., a capacitor without a parallel inductor) is switched into use when switch SW 1  is closed and is switched out of use when switch SW 1  is opened. Switch SW 2  is closed when it is desired to switch inductor L 1  and capacitor C 2  into use and may otherwise be opened. 
     Tunable circuitry such as tunable circuit  142  of  FIG. 9  may be used for implementing tunable circuit  142 L and/or tunable circuit  142 R of  FIG. 6 . Tunable circuit  142  includes first terminal  164  and second terminal  166 . Two respective branches of circuitry each having different circuit components are coupled between terminals  164  and  166  in parallel in the illustrative configuration of  FIG. 9 . Capacitor C 2  and inductor L 3  of circuit  142  are switched into use when switch SW 3  is closed and are switched out of use when switch SW 3  is opened. Switch SW 4  is closed when it is desired to switch inductor L 4  and capacitor C 4  into use and may otherwise be opened. Switches SW 3  and SW 4  may be turned on or off to switch the circuitry of circuit  142  into or out of use. 
     Switching circuitry in circuits  140  and  142  such as switches SW 1 , SW 2 , SW 3 , and SW 4  may be adjusted by control signals from control circuitry  28  based on real-time impedance measurements, received signal strength information, or other information. 
     If desired, one or more switchable inductors or other adjustable circuitry may be incorporated into return path  134 L and/or return path  134 R (e.g., to switch an inductor L 1  into use when tuning antennas  40  to cover midband MB and to switch a short circuit path into use when tuning antennas  40  to cover low band LB). Configurations in which return paths  134 L and  134 R are formed from strips of metal, metal traces on a printed circuit or plastic carrier, or other short circuit paths without tunable components may also be used. 
     Using circuits such as circuits  140  and  142  of  FIGS. 8 and 9 , the low band antenna resonance associated with each of antennas  40  can be tuned. For example, the low band resonance of each antenna may be centered on a first frequency in band LB when switch SW 1  is on and SW 2 , SW 3 , and SW 4  are off, may be centered on a second frequency in band LB that is greater than the first frequency when SW 1 , SW 2 , SW 3 , and SW 4  are off, may be centered on a third frequency in band LB that is greater than the second frequency when SW 3  is on, SW 1  is off, SW 2  is off, and SW 4  is off, and may be centered on a fourth frequency in band LB that is greater than the third frequency when SW 3  and SW 4  are on and SW 1  and SW 2  are off. In low band LB, inductors L 1  and L 3 , and L 4  provide low band tuning, but tend to pull resonant frequencies high. The capacitors in circuits  140  and  142  help lower the resonant frequencies to suitable values. 
     Antennas  40 L and  40 R may cover identical sets of frequencies or may cover overlapping or mutually exclusive sets of frequencies. As an example, antenna  40 R may serve as a primary antenna for device  10  and may cover frequencies of 700-960 MHz and 1700-2700 MHz, whereas antenna  40 L may serve as a secondary antenna that covers frequencies of 700-960 MHz and 1575-2700 MHz (or 1500-2700 MHz or 1400-2700 MHz, etc.). Global positioning system (GPS) signals are associated with the frequency of 1575 MHz. To help ensure that antenna  40 L covers GPS signals, return path  134 L may be formed from an inductor (e.g., a surface mount technology inductor or other packaged inductor), whereas return path  134 R in antenna  40 R may be formed from a strip of metal or other short circuit path. 
     The presence of the body of a user (e.g., a user&#39;s hand) or other external objects in the vicinity of antennas  40  may change the operating environment and tuning of antennas  40 . For example, the presence of an external object may shift the low band resonance of antennas  40  to lower frequencies. Real time antenna tuning using the adjustable components of  FIGS. 8 and 9  and/or other adjustable components may be used to ensure that antennas  40  operate satisfactorily regardless of whether external objects adjacent to antennas  40  are loading antennas  40 . For example, one or more inductors may be switched into use in circuits  140  and  142  (e.g., by closing some or all of the switches in circuits  140  and  142 ) to tune antenna resonant frequencies for antennas  40  to higher frequencies. 
     If desired, conductive structure  124  can be implemented using an array of switches each of which bridges slot  122 , as shown in  FIG. 10 . In the illustrative configuration of  FIG. 10 , there is a set of four switches SW bridging slot  122 . If desired, a single switch or more than four or fewer than four switches may be provided in the set of switches implementing conductive structures  124 . During normal operation, the switches of  FIG. 10  may be closed. When the presence of an external object is detected in the vicinity of antennas  40  that affects antenna operation (e.g., by measuring changes in impedance for antennas  40 L and  40 R using impedance monitoring circuitry coupled to antennas  40 L and  40 R, by measuring received signal strength information for each of antennas  40 L and  40 R, by using proximity detector measurements, etc.), the circuitry of  FIG. 10  can be adjusted accordingly. As an example, if an external object is detected and if antenna  40 L is performing better than antenna  40 R (as determined by impedance measurements, received signal strength information measurements, etc.), than switches SW of  FIG. 10  can be opened and antenna  40 R can be disconnected. With switches SW open, slots  122 L and  122 R will no longer be isolated by a conductive path shorting portions  12 R- 1  and  12 R- 2  and will join to form a single large open-ended slot with electric fields at the ends of the slot that are less concentrated than they otherwise would be at the end of a slot with one open and one closed end (i.e., with switches SW all open, the conductive bridging structure that would otherwise short  12 R- 1  and  12 R- 2  together is selectively removed). This reduces the sensitivity of slot  122  and therefore antenna  40 L to the presence of external objects. If desired, tunable components may be adjusted to restore the frequency response of antenna  40 L to a desired set of frequencies in the presence of an external object. 
       FIG. 11  is a diagram showing how adjustable circuitry  168  (e.g., adjustable impedance matching circuitry) may be incorporated into transmission line  92  to adjust the operation of antennas  40 L and/or  40 R in response to changes in operating environment (e.g., the presence or absence of external objects in the vicinity of antenna  40 ). The adjustable impedance matching circuitry of  FIG. 11  may be used in conjunction with adjustable circuitry such as the circuitry of  FIGS. 8, 9, and 10 , adjustable return path circuitry, and/or other adjustable circuitry or may be used independently. As shown in  FIG. 11 , path  92  may include lines  94  and  96 . Circuitry  168  may include switch  170  in line  94  that allows a component such as capacitor C to be selectively bypassed. During normal operation, capacitor C may be bypassed by connecting switch  170  to terminal  174 . In the presence of an external object that is affecting the performance of antenna  40 L and/or  40 R, switch  170  may be coupled to terminal  172  to switch capacitor C into use and thereby tune the antenna that is associated with path  92  to compensate for the presence of the external object. 
     If desired, an adjustable inductor or other tunable component in the return path of each antenna (i.e., in the short circuit path between element  132 L and the antenna ground formed from rear housing  12 R- 1  and/or the short circuit path between element  132 R and ground) may be adjusted to help tune antenna performance in midband MB. Configurations in which return path  132 L and/or return path  132 R do not include adjustable components may also be used. 
       FIG. 12  is a diagram of illustrative antenna configuration for device  10  in which the antenna return path includes an adjustable component. Antenna  40 ′ of  FIG. 12  may be used in implementing an antenna such as antenna  40 R and/or  40 L of  FIG. 6 . In the arrangement of  FIG. 12 , planar inverted-F antenna resonating element  130  is formed from planar metal structure  132 . Structure  132  may overlap slot  122 . Antenna  40 ′ may be a hybrid antenna that includes a planar inverted-F antenna formed from resonating element  130  and ground (metal housing  12 R- 1  and  12 R- 2 ) and that includes the slot antenna formed from slot  122 . Antenna  130  may serve as an indirect feed for the slot antenna formed from slot  122 . Transmission line  92  may be coupled to terminals  98  and  100  of feed  136  for antenna  130 . Return path  134  may be coupled between element  132  and the antenna ground formed from metal housing  12 R- 1  in parallel with feed  136 . Return path  134  may include an adjustable circuit such as an adjustable inductor. The adjustable inductor may include switching circuitry such as switches  180  and respective inductors  196  coupled in parallel between terminal  182  on the ground formed from metal  12 R- 1  and terminal  184  on element  132 . Control circuitry  28  may adjust adjustable circuits in device  10  such as adjustable return path circuit  134  of  FIG. 12  to tune antenna  40 ′. For example, switches  180  may be selectively opened and/or closed to switch desired inductors  196  into or out of use, thereby adjusting the inductance of the adjustable circuitry of return path  134 . 
     Antenna  40 ′ of  FIG. 12  may also have adjustable circuitry such as adjustable circuits  140 ′ and  142 ′ that bridge slot  122 . Circuits  140 ′ and  142 ′ may have inductors  192  or other circuit components that can be selectively switched into or out of use with switching circuitry such as switches  190 . If desired, capacitors may be coupled in parallel with one or more of inductors  192 , as described in connection with  FIGS. 8 and 9 . 
     During operation, antenna  40 ′ may operate in frequency bands such as low band LB, midband MB (e.g., a midband that extends down to 1400 MHz or other suitable frequency), and high band HB of  FIG. 7 . Circuits  140 ′ and  142 ′ (e.g., adjustable inductors formed from switching circuitry and individual inductors with our without capacitors coupled in parallel with the individual inductors) may be used to tune antenna  40 ′ in low band LB. The adjustable inductor of return path  134  may be used to provide multiple tuning states for midband MB. In scenarios in which the presence of an external object adjacent to slot  122  affects the operation of antenna  40 ′ (e.g., by shifting the low band resonance of antenna  40 ′ low), switches  180  may be opened, thereby shifting the low band resonance of antenna  40 ′ high to compensate. Tuning within low band LB may then be performed by adjusting the inductances of circuits  140 ′ and  142 ′. 
     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: 20160310
Publication Date: 20191126
Grant Date: 20191126
Priority Date: 20160310
Inventors: AZAD, Umar
RAJAGOPALAN, HARISH
GOMEZ ANGULO, RODNEY A.
ROMANO, Pietro
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 59788091