PATENT DOCUMENT

Publication Number: US-9543660-B2
Application Number: US-201414510724-A
Country: US
Kind Code: B2

Title: Electronic device cavity antennas with slots and monopoles

Abstract:
An electronic device may be provided with wireless circuitry. The wireless circuitry may include cavity antennas. A cavity antenna may be formed from a metal antenna cavity and resonating element structures. The metal antenna cavity may be formed from metal traces on a dielectric carrier. The resonating element structures may include directly fed and indirectly fed slot antenna resonating elements and monopole antenna resonating elements. The metal antenna cavity may exhibit a resonance that is tuned using a transmission line tuning stub. Filters and duplexer circuits may be used in routing signals at different frequency bands among the antenna resonating elements.

Claims:
What is claimed is: 
     
       1. A cavity antenna, comprising:
 a slot antenna resonating element; 
 a monopole antenna resonating element; 
 a metal antenna cavity that backs the slot antenna resonating element and the monopole antenna resonating element; and 
 a transmission line tuning stub coupled to the monopole antenna resonating element through a filter. 
 
     
     
       2. The cavity antenna defined in  claim 1 , wherein the filter is a low pass filter coupled between the monopole antenna resonating element and the transmission line tuning stub. 
     
     
       3. The cavity antenna defined in  claim 2  wherein the monopole antenna resonating element is directly fed. 
     
     
       4. The cavity antenna defined in  claim 3  wherein the slot antenna resonating element comprises an indirectly fed parasitic slot antenna resonating element. 
     
     
       5. The cavity antenna defined in  claim 4  wherein the indirectly fed parasitic slot antenna resonating element and the monopole antenna resonating element contribute antenna responses to a 5 GHz antenna band. 
     
     
       6. The cavity antenna defined in  claim 5  wherein the metal antenna cavity is associated with a cavity resonance at a given frequency and wherein the transmission line tuning stub lowers the cavity resonance of the metal antenna cavity from the given frequency to 2.4 GHz. 
     
     
       7. The cavity antenna defined in  claim 6  wherein metal antenna cavity comprises metal traces on a plastic carrier. 
     
     
       8. A cavity antenna, comprising:
 a first slot antenna resonating element; 
 a second slot antenna resonating element; 
 a monopole antenna resonating element; and 
 a metal antenna cavity that is overlapped at least by the first and second slot antenna resonating elements, wherein the metal antenna cavity has a protruding portion that extends under the monopole antenna resonating element. 
 
     
     
       9. The cavity antenna defined in  claim 8  wherein the first slot antenna resonating element is a directly fed slot antenna resonating element and wherein the second slot antenna resonating element is an indirectly fed parasitic slot antenna resonating element. 
     
     
       10. The cavity antenna defined in  claim 9  wherein the monopole antenna resonating element resonates at 2.4 GHz. 
     
     
       11. The cavity antenna defined in  claim 10  wherein the first and second slot antenna resonating elements contribute respective first and second antenna responses to an antenna resonance at 5 GHz. 
     
     
       12. The cavity antenna defined in  claim 11  further comprising a duplexer having a first port coupled to a transceiver, a second port coupled to the directly fed slot antenna resonating element, and a third port coupled to the monopole antenna resonating element. 
     
     
       13. The cavity antenna defined in  claim 12  further comprising a coaxial cable segment that extends from the third port to the monopole antenna resonating element, wherein the coaxial cable segment has an outer conductor. 
     
     
       14. The cavity antenna defined in  claim 13  further comprising a metal layer covering a surface of the cavity, wherein the first and second slot antenna resonating elements are formed from respective first and second openings in the metal layer and the outer conductor of the coaxial cable segment is electrically connected to the metal layer along the coaxial cable. 
     
     
       15. The cavity antenna defined in  claim 8  wherein the metal antenna cavity comprises a first portion having a periphery, the protruding portion extends beyond the periphery of the first portion, the first portion is overlapped by the first and second slot antenna resonating elements without being overlapped by the monopole antenna resonating element, and the protruding portion is overlapped by the monopole antenna resonating element without being overlapped by the first and second slot antenna resonating elements. 
     
     
       16. A cavity antenna, comprising:
 an antenna cavity; 
 a first slot antenna resonating element that is backed by the antenna cavity; 
 a second slot antenna resonating element that is backed by the antenna cavity; and 
 a monopole antenna resonating element that is not backed by the antenna cavity. 
 
     
     
       17. The cavity antenna defined in  claim 16  further comprising:
 a low pass filter coupled to the monopole antenna resonating element. 
 
     
     
       18. The cavity antenna defined in  claim 17  further comprising:
 a high pass filter coupled to the first slot antenna resonating element. 
 
     
     
       19. The cavity antenna defined in  claim 18  wherein the low pass filter passes 2.4 GHz signals to and from the monopole antenna resonating element and wherein the high pass filter passes 5 GHz signals to and from the first and second slot antenna resonating elements. 
     
     
       20. The cavity antenna defined in  claim 19  wherein the first slot antenna resonating element is a directly fed antenna resonating element and wherein the second slot antenna resonating element is an indirectly fed parasitic slot antenna resonating element and wherein the first and second slot antenna resonating elements contribute respective first and second antenna responses to an antenna resonance at 5 GHz.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with antennas. 
     Electronic devices often include antennas. For example, cellular telephones, computers, and other devices often contain antennas for supporting wireless communications. 
     It can be challenging to form electronic device antenna structures with desired attributes. In some wireless devices, the presence of conductive housing structures can influence antenna performance. Antenna performance may not be satisfactory if the housing structures are not configured properly and interfere with antenna operation. Device size can also affect performance. It can be difficult to achieve desired performance levels in a compact device, particularly when the compact device has conductive housing structures. 
     It would therefore be desirable to be able to provide improved antennas for electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry. The wireless circuitry may include cavity antennas. A cavity antenna may be formed from a metal antenna cavity and resonating element structures. The metal antenna cavity may be formed from metal traces on a dielectric carrier. The resonating element structures may include directly fed and indirectly fed slot antenna resonating elements and monopole antenna resonating elements. The metal antenna cavity may exhibit a resonance that is tuned using a transmission line tuning stub. Filters and duplexer circuits may be used in routing signals at different frequency bands among the antenna resonating elements. 
     With one arrangement, a cavity antenna may have a directly fed monopole antenna resonating element and a parasitic slot antenna resonating element that are backed by an antenna cavity. The monopole antenna resonating element and the parasitic antenna resonating element may contribute antenna responses at first and second respective frequencies to a high band resonance. The antenna cavity may exhibit a low band resonance that is tuned to a desired frequency using a transmission line tuning stub that is coupled to the monopole antenna resonating element by a low pass filter. 
     A cavity antenna first and second slot antenna resonating elements that are backed by a metal antenna cavity. The first and second slot antenna resonating elements may contribute antenna responses at first and second respective frequencies to a high band resonance. A monopole antenna resonating element may exhibit a low band resonance. The first slot antenna element may be directly fed and the second slot antenna element may be a parasitic element that is indirectly fed by the first slot. A duplexer may route high band signals to the slots and low band signals to the monopole. A segment of coaxial cable may couple the duplexer to the monopole antenna resonating element. The antenna cavity may be covered with a metal layer that has openings to form the first and second slots. The segment of coaxial cable may have an outer conductor that is shorted along its length to the metal layer. 
     A cavity antenna may include first and second slot antenna resonating elements that are backed by an antenna cavity and a monopole antenna resonating element that is not backed by the antenna cavity. The first slot antenna resonating element may be directly fed. The second slot antenna resonating element may be near-field coupled to the first slot antenna resonating element and may broaden the bandwidth of the antenna in a high frequency band (e.g., a band at 5 GHz). A transmission line may be coupled to a radio-frequency transceiver operating at 2.4 GHz and 5 GHz. A low pass filter may be coupled between the transmission line and the monopole antenna resonating element to allow 2.4 GHz signals to pass to and from the monopole antenna resonating element. A high pass filter may be coupled between the transmission line and the first slot antenna to allow 5 GHz signals to pass to and from the first and second slot antenna resonating elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment. 
         FIG. 3  is a diagram of illustrative wireless circuitry in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative cavity antenna in accordance with an embodiment. 
         FIG. 5  is a top view of an illustrative cavity antenna with a monopole resonating element, a parasitic slot resonating element, and a transmission line tuning stub to tune a cavity resonance for the antenna in accordance with an embodiment. 
         FIG. 6  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency for an antenna of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 7  is a top view of an illustrative cavity antenna with a directly fed slot, a parasitic slot, and monopole antenna in accordance with an embodiment. 
         FIG. 8  is a top view of an illustrative cavity antenna having a directly fed slot, a parasitic slot antenna resonating element, and a monopole element that lies outside of the cavity in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may contain wireless circuitry. The wireless circuitry may include antenna structures such as one or more cavity antennas. 
     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 pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma pixels, an array of organic light-emitting diode pixels, an array of electrowetting pixels, or 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  40  may be mounted along the edges of housing  12 , at the corners of housing  12  (as shown in  FIG. 1 ) or elsewhere in device  10 . There may be any suitable number of antennas  40  in device  10  (e.g., one antenna, two antennas, three antennas, or four or more antennas). 
     A schematic diagram showing illustrative components that may be used in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  30 . Storage and processing circuitry  30  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  30  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, baseband processor integrated circuits, application specific integrated circuits, etc. 
     Storage and processing circuitry  30  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  30  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  30  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, satellite navigation system protocols, etc. 
     Device  10  may include input-output circuitry  44 . 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, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, accelerometers or other components that can detect motion and device orientation relative to the Earth, capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, a connector port sensor or other sensor that determines whether device  10  is mounted in a dock, and other sensors and input-output components. 
     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  40 , 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 1710 to 2170 MHz, and a high band from 2300 to 2700 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 (e.g., GLONASS signals at 1609 MHz). 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. 
     Antennas  40  in wireless communications circuitry  34  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. If desired, one or more of antennas  40  may be cavity-backed antennas formed by placing slot antennas, monopole antennas, and other resonating element structures over the opening in a metal antenna cavity. 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. Dedicated antennas may be used for receiving satellite navigation system signals or, if desired, antennas  40  can be configured to receive both satellite navigation system signals and signals for other communications bands (e.g., wireless local area network signals and/or cellular telephone signals). 
     Transmission line paths may be used to couple antenna structures  40  to transceiver circuitry  90 . Transmission lines in device  10  may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired. 
     Device  10  may contain multiple antennas  40 . The antennas may be used together or one of the antennas may be switched into use while the other antenna(s) may be switched out of use. If desired, control circuitry  30  may be used to select an optimum antenna to use in device  10  in real time and/or an optimum setting for a phase shifter or other wireless circuitry coupled to the antennas (e.g., an optimum antenna to receive satellite navigation system signals, etc.). Control circuitry  30  may, for example, make an antenna selection or antenna array phase adjustment based on information on received signal strength, based on sensor data (e.g., orientation information from an accelerometer), based on other sensor information (e.g., information indicating whether device  10  has been mounted in a dock in a portrait orientation), or based on other information about the operation of device  10 . 
     As shown in  FIG. 3 , transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as transmission line path  92 . Wireless circuitry  34  may be coupled to control circuitry  30 . Control circuitry  30  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  30  may issue control signals on one or more paths such as path  88  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. Configurations in which antennas  40  are fixed (not tunable) may also be used. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 3  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 on a printed circuit (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 coupled to antenna feed structures associated with antenna structures  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna, a monopole antenna, an antenna having a parasitic antenna resonating element, 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 . Other types of antenna feed arrangements may be used if desired. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     It may be desirable to form one or more of antennas  40  using cavity-backed antenna designs. In a cavity antenna, a metal cavity forms antenna ground. The antenna cavity may be formed by metal traces on a plastic carrier (e.g., plated metal traces), may be formed from stamped metal structures, may be formed from portions of housing  12 , or may be formed from other conductive structures. The cavity may, as an example, have a box shape with an open top. One or more resonating elements may be formed in the open top. Cavity antennas may offer good isolation with respect to internal components in device  10  and other antennas and may satisfy limits on emitted radiation levels (sometimes known as specific absorption rate limits). 
       FIG. 4  is an exploded perspective view of an illustrative cavity antenna. As shown in  FIG. 4 , illustrative antenna  40  of  FIG. 4  has cavity  100 . Cavity  100  may have a hollow interior or may have an internal dielectric support structure such as a plastic carrier. The plastic carrier may have one or more air-filled cavities or may be solid. Structures based on foam and other dielectric materials may also be used, if desired. 
     Metal cavity walls  104  may be formed on the surfaces of the dielectric carrier (as an example). Metal cavity walls  104  may be formed on the lower surface of the carrier and on front, back, left, and right sidewalls of the carrier to form an open-topped box or other cavity shapes may be formed. One or more antenna resonating elements or other structures may be mounted in region  106  in the top surface of the box so that these antenna resonating elements are backed by the cavity. 
     If desired, metal coating layer  102  may cover some of the top of the box forming cavity  100 . Metal coating layer  102  may be formed from metal traces on a plastic carrier, patterned metal foil, traces on a printed circuit that overlap the opening in cavity  100 , and/or other suitable structures. Slot antenna resonating elements may be formed from openings in layer  102 . Antenna structures may also be formed using wires, cables, portions of housing  12 , metal structures such as brackets, metal traces on printed circuits, etc. The metal structures in region  106  and elsewhere in antenna  40  may be patterned to form monopole elements, slot antennas (i.e., antennas formed from openings in metal), inverted-F antenna resonating elements, or other suitable antenna elements. 
     In the example of  FIG. 4 , cavity  100  has four sidewalls, one of which is curved to allow antenna  40  to be mounted along a curved inner surface of a curved wall of housing  12 . Other cavity shapes may be used if desired. 
     Antenna  40  may be fed using signals that are conveyed to antenna  40  using a transmission line. The transmission line may be coupled to one or more portions of antenna  40 . The transmission line may be a coaxial cable, may be a microstrip transmission line in flexible printed circuit  108  or other printed circuit, or may be any other suitable transmission line. If desired, optional dielectric loading layer  110  may be placed on top of region  106  (e.g., to provide dielectric loading for the antenna that helps tune antenna  40 ). 
       FIG. 5  is a top view of antenna  40  in an illustrative configuration that includes a transmission line tuning stub. Antenna  40  may operate in a band at 5 GHz (e.g., to support wireless area network communications such as IEEE 802.11 communications) and may operate in a band at 2.4 GHz (e.g., to support wireless local area network communications such as IEEE 802.11 communications, to support Bluetooth® communications, and/or to support cellular telephone communications. 
     As shown in  FIG. 5 , antenna  40  may have a cavity such as cavity  100  of  FIG. 4 . The upper surface of cavity  100  may be covered with metal  102 . Parasitic slot antenna resonating element  112  may be formed from an opening in metal  102  (e.g., an elongated rectangular opening or other elongated slot opening that is backed by cavity  100 ). Monopole antenna resonating element  114  may be directly fed using antenna feed terminals  98  and  100 . Transmission line  92  may have a positive signal line such as line  94  that is coupled to positive antenna feed terminal  98  and a ground signal line such as line  96  that is coupled to ground antenna feed terminal  100 . 
     Monopole antenna resonating element  114  may overlap the upper surface of cavity  100  (i.e., element  114  may be backed by cavity  100 ) and may be separated from metal layer  102  by a layer of dielectric or other suitable structure. As shown in  FIG. 5 , monopole element  114  may have first and second opposing ends such as ends  114 - 1  and  114 - 2 . End  114 - 1  may be coupled to positive terminal  98 . Element  114  may be bent at bend  114 - 3 , so that element  114  has an L shape or other suitable shape. The segment of element  114  that extends between bend  114 - 3  and end  114 - 2  may run parallel to slot  112 . 
     Transmission line stub  116  may be formed from a segment of coaxial cable or other transmission line. Stub  116  may tune a cavity resonance associated with cavity  100  so that antenna  40  resonates at desired frequencies. Low pass filter  118  may have circuit elements such as capacitor  120  and inductor  122 . Capacitor  120  and inductor  122  may be coupled in parallel between monopole element  114  and end  116 - 1  of stub  116 . Stub  116  may run parallel to element  114  between end  116 - 1  and end  116 - 2 . 
       FIG. 6  is a graph of antenna performance (standing wave ratio SWR) for antenna  40  of  FIG. 5 . As shown in  FIG. 6 , antenna  40  may exhibit an antenna resonance at 2.4 GHz (curve  126 ) and a resonance at 5 GHz (curve  128 ). During operation, monopole element  114  may resonate at 5.3 GHz and may therefore contribute a response at 5.3 GHz to resonance  128 . Slot element  112  is indirectly fed through near-field electromagnetic coupling from element  114 . Slot  112  may resonate at 5.7 GHz and may therefore contribute a broadening response at 5.7 GHz to resonance  128 . 
     Low pass filter  118  may block signals at 5 GHz and thereby isolate cavity  100  from tuning stub  116 . Cavity  100  may have a size (e.g., 12 mm by 18 mm or other suitable size that is sufficiently small to allow nearby components to be mounted within the limited interior volume of housing  12 ). In the absence of tuning stub  116 , cavity  100  may resonate at a frequency such as 2.9 GHz, as shown by dashed line  124 . In the presence of tuning stub  116 , the resonance at 2.9 GHz may be tuned to a desired lower frequency of 2.4 GHz, as shown by curve  126 . 
     In the illustrative example of  FIG. 7 , antenna  40  has cavity  100 . Antenna  40  of  FIG. 7  may operate at both 2.4 GHz and 5 GHz. Metal layer  102  covers the upper opening of cavity  100 . Openings in layer  102  form slot antenna resonating element  112 - 1  and parasitic slot antenna resonating element  112 - 2 , which are backed by cavity  100 . Transmission line  92 C is coupled between transceiver circuitry  90  and duplexer  130 . Duplexer  130  has three ports. The first port of duplexer  130  is coupled to transmission line  92 C and carries both 2.4 GHz and 5 GHz antenna signals. The second port of duplexer  130  is coupled to transmission line  92 A and carries only 5 GHz antenna signals. The third port of duplexer  130  is coupled to transmission line  92 B and carries only 2.4 GHz signals. 
     Transmission line  92 A carries 5 GHz antenna signals for slots  112 - 1  and  112 - 2 . Line  94 A of transmission line  92 A is coupled to positive antenna feed terminal  98 A. Line  96 A of transmission line  92 A is coupled to ground antenna feed terminal  100 A. Feed terminals  98 A and  100 A bridge slot  112 - 1  and directly feed slot  112 - 1 . Through near-field electromagnetic coupling, slot  112 - 1  indirectly feeds parasitic slot antenna resonating element  112 - 2 . Slots  112 - 1  and  112 - 2  have sizes selected to resonate at different portions of the 5 GHz band (e.g., 5.3 GHz and 5.7 GHz, or vice versa), thereby covering the 5 GHz band with a desired bandwidth. The use of a pair of slots in antenna  40 , one of which is directly fed and the other of which serves as a bandwidth-broadening parasitic element is merely illustrative. If desired, different slot antenna configurations may be used for cavity antenna  40  of  FIG. 7 . 
     Transmission line  92 B carries 2.4 GHz signals. Line  94 B is coupled to positive terminal  98 B of transmission line  92 D. Line  96 B is coupled to terminal  100 B of transmission line  92 D. Transmission line  92 B may be a coaxial cable having a grounded outer conductor. The outer conductor of transmission line  92 B may be electrically connected to metal layer  102  at electrical connections  132  (welds, solder joints, clamped metal tabs, conductive adhesive, etc.) along the length of transmission line  92 B. Terminal  100 D of coaxial cable  92 D is coupled to metal layer  102 . Terminal  98 D is coupled to monopole antenna resonating element  114 . Cavity  100  may have a protruding portion such as portion  134  that extends under monopole antenna element  114  or cavity  110  may have a wall that terminates along line  136  (as examples). Terminals  98 D and  100 D may serve as an antenna feed for monopole antenna resonating element  114 . During operation, monopole element  114  may handle signals at 2.4 GHz and slots  112 - 1  and  112 - 2  may handle 5 GHz signals. 
     In the illustrative configuration of  FIG. 8 , monopole antenna element  114  is formed outside of cavity  100 . Transmission line  92  is coupled to transceiver circuitry  90  and carries 2.4 and 5 GHz signals. High pass filter  162  is interposed between transmission line  92  and slot antenna  112 - 1  and allows 5 GHz signals to pass to and from slot antenna  112 - 1  and parasitic slot antenna  112 - 2 , which are backed by metal antenna cavity  100  Slot antenna  112 - 1  may be directly fed using feed terminals  98 A and  100 A, which bridge slot antenna  112 - 1 . Parasitic slot antenna resonating element  112 - 2  is near-field coupled to slot  112 - 1  and may contribute a broadening resonance to the performance of antenna  40 . For example, slot  112 - 1  may contribute a response at 5.2 GHz and parasitic slot  112 - 2  may contribute a response at 5.7 GHz. 
     Low pass filter  160  may allow 2.4 GHz signals to pass to and from monopole antenna resonating element  114 . Monopole antenna resonating element  114  may have a length that is configured to resonate at 2.4 GHz. Terminals  98 B and  100 B may form an antenna feed for monopole  114 . 
     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: 20141009
Publication Date: 20170110
Grant Date: 20170110
Priority Date: 20141009
Inventors: RAJAGOPALAN HARISH
HUANG HUAN-CHU
SUN KE
LI QINGXIANG
SCHLUB ROBERT W.
GOMEZ ANGULO RODNEY A.
AZAD UMAR
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0407", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/392", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54595665