PATENT DOCUMENT

Publication Number: US-10218052-B2
Application Number: US-201514710377-A
Country: US
Kind Code: B2

Title: Electronic device with tunable hybrid 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. The slot of each 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. Tunable components such as tunable inductors may be used to tune the hybrid antennas. A tunable inductor may bridge the slot in 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.

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 that indirectly feeds antenna signals for the slot antenna resonating element via near-field electromagnetic coupling; and 
 first and second tunable components that are configured to tune the hybrid antenna, wherein the planar inverted-F antenna resonating element overlaps the slot across an area, the first and second tunable components extend across the slot at first and second respective locations, and the area is interposed between the first and second locations. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the planar inverted-F antenna resonating element has a planar metal element, a return path coupled between the planar metal element and the ground plane, and an antenna feed having a positive antenna feed terminal and a ground antenna feed terminal coupled between the planar metal element and the ground plane in parallel with the return path. 
     
     
       3. The electronic device defined in  claim 2  wherein the slot divides the ground plane into 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. 
     
     
       4. The electronic device defined in  claim 3  wherein the first tunable component includes a tunable inductor. 
     
     
       5. The electronic device defined in  claim 4  wherein the tunable inductor bridges the slot and is coupled between the first and second ground plane portions. 
     
     
       6. The electronic device defined in  claim 5  wherein the second tunable component comprises an additional tunable inductor that bridges the slot and is coupled between the first and second ground plane portions. 
     
     
       7. The electronic device defined in  claim 6  wherein the slot has an open end and a closed end and wherein the tunable inductor bridges the slot at a location between the planar inverted-F antenna resonating element and the closed end. 
     
     
       8. The electronic device defined in  claim 7  wherein the additional tunable inductor bridges the slot at a location between the planar inverted-F antenna resonating element and the open end. 
     
     
       9. The electronic device defined in  claim 8  wherein the tunable inductor and the additional tunable inductor are switchable between open and closed states to tune the hybrid antenna to at least three different low band resonances. 
     
     
       10. The electronic device defined in  claim 1 , wherein the first tunable component has first and second terminals respectively coupled to first and second opposing sides of the slot. 
     
     
       11. The electronic device defined in  claim 1 , wherein the slot divides the ground plane into first and second ground plane portions on opposing sides of the slot, and a conductive member that bisects the slot and that shorts the first ground plane portion to the second ground plane portion. 
     
     
       12. An electronic device, comprising:
 a metal housing with four edges; 
 first and second antennas located along one of the four edges, wherein each of the first and second antennas is a hybrid antenna that includes:
 a ground plane formed from a portion of the metal housing; 
 a slot in the ground plane that forms a slot antenna resonating element for the hybrid antenna, wherein a conductive structure separates the slot of the first antenna from the slot of the second antenna; 
 a planar inverted-F antenna resonating element for the hybrid antenna that indirectly feeds the slot antenna resonating element, wherein the conductive structure is interposed between the planar inverted-F antenna resonating element of the first antenna and the planar inverted-F antenna resonating element of the second antenna; and 
 a tunable inductor that tunes the hybrid antenna. 
 
 
     
     
       13. The electronic device defined in  claim 12  wherein the tunable inductor for the first antenna is coupled between a portion of the planar inverted-F antenna resonating element for the first antenna and the ground plane for the first antenna. 
     
     
       14. The electronic device defined in  claim 12  wherein the tunable inductor for the first antenna bridges the slot. 
     
     
       15. The electronic device defined in  claim 12  wherein the metal housing has a metal rear housing wall and metal housing sidewalls wherein the ground plane for the first antenna is formed from the metal rear housing wall and metal housing sidewalls. 
     
     
       16. The electronic device in  claim 12 , wherein the conductive structure comprises a shorting structure having first and second opposing sides, the first side forms a first closed end for the slot of the first antenna, and the second side forms a second closed end for the slot of the second antenna. 
     
     
       17. The electronic device in  claim 12 , wherein the planar inverted-F antenna resonating element of the first antenna overlaps the slot of the first antenna at a first location, the planar inverted-F antenna resonating element of the second antenna overlaps the slot of the second antenna at a second location and the conductive structure is interposed between the first and second locations. 
     
     
       18. The electronic device in  claim 12 , wherein the slot for each of the first and second antenna has a closed end defined by the conductive structure and an open end that terminates at the one of the four edges. 
     
     
       19. An antenna, comprising:
 a metal electronic device housing wall; 
 a slot in the metal electronic device housing wall, wherein first and second portions of the metal electronic device housing wall are located on opposing first and second sides of the slot; 
 a planar inverted-F antenna resonating element that has a planar metal element having an edge on the first side of the slot, a return path coupled between the edge of the planar metal element and the first portion of the metal electronic device housing wall on the first side of the slot, and an antenna feed having a positive antenna feed terminal coupled to the edge of the planar metal element on the first side of the slot and a ground antenna feed terminal coupled to the first portion of the metal electronic device housing wall on the first side of the slot; and 
 a tunable inductor having a first terminal coupled to a location along the edge of the planar metal element between the return path and the positive antenna feed terminal and having a second terminal coupled to the first portion of the metal electronic device housing wall on the first side of the slot between the return path and the ground antenna feed terminal. 
 
     
     
       20. The antenna defined in  claim 19  further comprising a tunable inductor having a terminal coupled to the first portion of the metal electronic device housing 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. 
     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 housing slot that has been divided into left and right slots for hybrid planar inverted-F-slot antennas in accordance with an embodiment. 
         FIG. 7  is a top view of an illustrative hybrid antenna showing how the antenna may be tuned using a tunable inductor that bridges a slot resonating element in accordance with an embodiment. 
         FIG. 8  is a perspective view of a planar inverted-F antenna resonating element and a portion of an associated slot in a hybrid antenna showing how the antenna may be tuned using a tunable inductor that is coupled between the planar inverted-F antenna resonating element and ground in accordance with an embodiment. 
         FIG. 9  is a perspective view of an illustrative planar inverted-F antenna resonating element and a portion of an associated slot in a hybrid antenna showing how the antenna may be tuned using a pair of tunable inductors that bridge the slot on opposing sides of the planar inverted-F antenna resonating element in accordance with an embodiment. 
         FIG. 10  is a schematic diagram of an illustrative tunable inductor based on a switch and three inductors in accordance with an embodiment. 
         FIG. 11  is a schematic diagram of an illustrative tunable inductor based on an inductor and a switch that switches the inductor into use or out of use in accordance with an embodiment. 
         FIG. 12  is a graph in which antenna performance (standing-wave ratio SWR) has been plotted as a function of operating frequency showing how antenna tuning operations may be used to cover desired communications frequencies 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. 
     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. 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 structure such as conductive member  124 . Conductive member  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 member  124  may be shorted to metal housing wall  12 R on opposing sides of slot  122 . 
     In the presence of conductive member  124 , 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  37  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 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 1500 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 a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . 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 half slot  122 L and right half 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 F 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 is 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 to planar inverted-F antenna resonating element  130 L. 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 may 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 to planar inverted-F antenna resonating element  130 R. 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 element  132 R of planar-inverted-F antenna resonating element  130 R. Planar-inverted-F antenna resonating element  130 R may also 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 ). 
     Slots  122 L and  122 R may have lengths (quarter wavelength lengths) that support a native resonance at about  1 . 1  GHz or other suitable frequency. The presence of planar-inverted-F elements  130 L and  130 R and other components (e.g., tuning components) may lower the frequency of the slot resonance to cover a low communications band (e.g., a low band at frequencies between 700 and 960 MHz). Mid-band coverage (e.g., for a mid-band centered at 1700 MHz) 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) may be supported using harmonics of the slot antenna resonating element resonance (e.g., a third order harmonic, etc.). 
     Once way to lower the slot resonance to cover desired low band frequencies involves incorporating inductive components into antennas  40 L and  40 R (e.g., fixed and/or tunable components such as tunable components  102  of  FIG. 5 ). As shown in the left antenna example of  FIG. 7 , a tunable inductor such as inductor  140 L for antenna  40 L may have a first terminal such as terminal  142 L that is coupled to portion  12 R- 2  of metal housing wall (ground)  12 R on one side of slot  122 L and may have a second terminal such as terminal  144 L that is coupled to portion  12 R- 1  of housing (ground)  12 R on the opposing side of slot  122 L. There may be two or more inductors such as tunable inductor  140 L that bridge each slot. The example of  FIG. 7  in which a single inductor  140 L bridges slot  122 L at a location between planar inverted-F antenna resonating element  130 L and closed slot end  122 - 2  of left slot  122 L is merely illustrative. 
     Another potential tuning arrangement for antennas  40 L and  40 R is shown in  FIG. 8 . In the example of  FIG. 8  (which shows an illustrative tuning arrangement for left antenna  40 L), tunable inductor  146 L has been coupled between terminal  148 L on planar element  132 L of planar inverted-F antenna resonating element  130 L and terminal  150 L at the antenna ground (metal housing portion  12 R- 1 ). In this arrangement, tunable inductor  146 L is coupled between planar structure  132 L and ground in parallel with feed  136 L and return path  134 L. 
     As shown in the illustrative configuration of  FIG. 9 , a pair of tunable inductors may be used to bridge slot  122 L at two different locations. Tunable inductor  152 L- 1  is coupled between terminal  154 L on one side of slot  122 L and terminal  156 L on an opposing side of slot  122 L. Terminals  154 L and  156 L are coupled to the antenna ground formed by metal housing wall portions  12 R- 2  and  12 R- 1 , respectively. Tunable inductor  152 L- 2  is coupled between terminal  158 L on metal housing wall portion  12 R- 2  and terminal  160 L on metal housing wall portion  12 R- 1 . With this configuration, inductor  152 L- 1  bridges slot  122 L at a location between closed slot end  122 - 2  and planar inverted-F antenna resonating element  130 L and inductor  152 L- 2  bridges slot  122 L at a location between planar inverted-F antenna resonating element  130 L and open end  122 - 1  of slot  122 L. If desired, both of inductors  152 L- 1  and  152 L- 2  may be located on the same side of planar inverted-F antenna resonating element  130 L. Moreover, configurations of the types shown in  FIGS. 7, 8, and 9  and other configurations for incorporating tunable inductors and other tunable components  102  into antenna  40 L (and  40 R) may be used in combination with each other. 
     The number of tuning states for the inductor circuitry of antennas  40 L and  40 R may be selected based on the bandwidth of the slot  122  and the frequency range to be covered. Low band tuning with tunable inductors preferably does not significantly impact mid-band and high band coverage, so tunable inductors can be adjusted to ensure that the slot resonance from the slot-antenna resonating element structures covers the low band without disrupting mid-band and high band operation. Two or more tuning states, three or more tuning states, or four or more different tuning states may be used to cover the low band with the slot resonances of the antennas. 
     Consider, as an example, a tuning arrangement of the type shown in  FIG. 7  or  FIG. 8 . With these arrangements, tunable inductor  146 L ( FIG. 8 ) or tunable inductor  140 L ( FIG. 7 ) may be implemented using a tunable inductor circuit of the type shown by tunable inductor  186  in  FIG. 10 . As shown in  FIG. 10 , tunable inductor  186  may have three discrete inductors L 1 , L 2 , and L 3  and a switch such as switch  180  that switches a desired discrete inductor into use between terminals  182  and  184 . Tunable inductor  186  can be adjusted to switch inductor L 1  (e.g., a 1 nH inductor), L 2  (e.g. a 5 nH inductor), or L 3  (e.g., a 30 nH inductor) into use (as an example), so tunable inductor  186  can create three different tuning states for an antenna. If desired, one of the tuning states of inductor  186  may be achieved by disconnecting all inductors to produce “infinite” impedance (infinite inductance). Configurations of the type shown in  FIG. 10  may also be used to form desired inductances using combinations of parallel inductors and/or may be used with fewer inductors or more inductors. The arrangement of  FIG. 10  is merely illustrative. 
     As another example, consider tunable inductor  190  of  FIG. 11 . With this arrangement, tunable inductor  190  has discrete inductor L and switch  196  coupled in series between terminals  192  and  194 . Tunable inductors such as tunable inductor  190  may be used to implement inductors  152 L- 1  and  152 L- 2  of  FIG. 9  (as an example). 
     Discrete inductors for tunable inductor components can be incorporated into the same package or die as switching circuitry or may be mounted as separate parts on a shared printed circuit (as examples). 
     Antenna tuning results of the type that may be achieved using tunable inductors such as inductors  186  and  190  are shown in  FIG. 12 . In the graph of  FIG. 12 , antenna performance (standing wave ratio SWR) has been plotted as a function of operating frequency f for a low band LB, a mid-band MB, and a high band HB. Low band LB may be covered by adjusting an antenna (e.g., left antenna  40 L or right antenna  40 R) to cover resonances  200 ,  202 , and  204 . 
     Using a tunable antenna such as the antenna of  FIG. 7  or the antenna of  FIG. 8 , a three-state tunable inductor such as inductor  186  of  FIG. 10  may be placed in a first state (e.g., an inductance of 30 nH or other suitable inductance) to tune the antenna so that the antenna exhibits low band resonance  200  (e.g., to cover band B 17 ), may be placed in a second state (e.g., an inductance of 5 nH or other suitable inductance) to tune the antenna so that the antenna exhibits low band resonance  202  (e.g., to cover band B 20 ), and may be placed in a third state (e.g., an inductance of 1 nH or other suitable inductance) to tune the antenna so that the antenna exhibits low band resonance  204  (e.g., to cover band B 8 ). Switch  180  may be a single-pole triple-throw switch or other suitable switch in this type of scenario. 
     Using a tunable antenna such as the antenna of  FIG. 9  with tunable (switchable) inductors  190  of  FIG. 11  for inductors  152 L- 1  and  152 L- 2 , resonance  204  may be achieved by opening the switches in both tunable inductor  152 L- 1  and tunable inductor  152 L- 2 . Resonance  202  (to cover band B 20 ) may be achieved by closing inductor  152 L- 1  so that its inductance bridges slot  122  and by simultaneously opening inductor  152 L- 2  (i.e., by opening switch  196  in this inductor) to create an open circuit for inductor  152 L- 2 . Resonance  202  (band B 8 ) may be achieved by closing the switch in inductor  152 L- 2  and opening the switch in inductors  152 L- 1 . The switches  196  in the tunable inductors  152 L- 1  and  152 L- 2  may be single-pole single-throw switches (as an example). 
     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: 20150512
Publication Date: 20190226
Grant Date: 20190226
Priority Date: 20150512
Inventors: PASCOLINI, MATTIA
AZAD, Umar
GOMEZ ANGULO, RODNEY A.
IRCI, Erdinc
LI, QINGXIANG
MOW, MATTHEW A.
RAJAGOPALAN, HARISH
SAMARDZIJA, Miroslav
TSAI, MING-JU
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 56096764