PATENT DOCUMENT

Publication Number: US-9444540-B2
Application Number: US-201213631290-A
Country: US
Kind Code: B2

Title: System and methods for performing antenna transmit diversity

Abstract:
A wireless electronic device may include switching circuits that perform time division duplexing by toggling between a first configuration in which radio-frequency signals received from antennas are routed to the transceivers and a second configuration in which the antennas are coupled to antenna switching circuitry. The antenna switching circuitry may receive radio-frequency transmission signals from the transceivers and route the transmission signals to a selected one of the antennas. The antenna switching circuitry may be controlled by control circuitry such as baseband circuitry and/or storage and processing circuitry on the device. The antenna switching circuitry may be controlled to accommodate antenna transmit diversity without affecting reception of radio-frequency signals, because the switching circuits that perform time division duplexing may form signal reception paths that are unaffected by the configuration of the antenna switching circuitry.

Claims:
What is claimed is: 
     
       1. A wireless electronic device, comprising:
 upper and lower antennas that each operate using the same broadband cellular technology; 
 a housing for the wireless electronic device that comprises portions of the upper and lower antennas; 
 transceiver circuitry configured to repeatedly toggle between wireless reception operations that occur during a first time period and wireless transmission operations that occur during a second time period, wherein a duration of the first time period and a duration of the second time period are each dynamically adjusted based on detected bandwidth requirements; 
 a multi-transmit-port switch configured to route radio-frequency transmission signals from the transceiver circuitry to a selected antenna of the upper and lower antennas; and 
 transmit-receive switching circuitry coupled between the multi-transmit-port switch and the upper and lower antennas, wherein the transmit-receive switching circuitry is operable to repeatedly toggle between a first configuration in which radio-frequency reception signals are routed from the upper and lower antennas to the transceiver circuitry and a second configuration in which the radio-frequency transmission signals are provided from the multi-transmit-port switch to the selected antenna, and in the first configuration the upper and lower antennas are coupled to the transceiver circuitry through a corresponding one of a plurality of receive paths of the transmit receive switching circuitry while bypassing the multi-transmit-port switch. 
 
     
     
       2. The wireless electronic device defined in  claim 1 , the transmit-receive switching circuitry comprising:
 a first switch coupled between the upper antenna and the multi-transmit-port switch; and 
 a second switch coupled between the lower antenna and the multi-transmit-port switch. 
 
     
     
       3. The wireless electronic device defined in  claim 2  wherein the first switch couples the upper antenna to the multi-transmit-port switch during the second configuration. 
     
     
       4. The wireless electronic device defined in  claim 2  wherein the first switch couples the upper antenna to the transceiver circuitry during the first configuration while bypassing the multi-transmit-port switch. 
     
     
       5. The wireless electronic device defined in  claim 2  wherein the second switch couples the lower antenna to the multi-transmit-port switch during the second configuration. 
     
     
       6. The wireless electronic device defined in  claim 2  wherein the second switch couples the lower antenna to the transceiver circuitry during the second configuration while bypassing the multi-transmit-port switch, the wireless electronic device further comprising:
 at least one low noise amplifier coupled between the first switch and the transceiver circuitry, wherein the low noise amplifier is operable to amplify the radio-frequency reception signals. 
 
     
     
       7. The wireless electronic device defined in  claim 1  further comprising:
 at least one power amplifier coupled between the transceiver circuitry and the multi-transmit-port switch, wherein the power amplifier is operable to amplify the radio-frequency transmission signals. 
 
     
     
       8. The wireless electronic device defined in  claim 1 , wherein the transmit-receive switching circuitry is coupled to the transceiver circuitry through at least three duplexers that are configured to perform transmit operations while bypassing the multi-transmit-port switch. 
     
     
       9. The wireless electronic device defined in  claim 1 , wherein the housing comprises a conductive housing structure that extends around a periphery of the wireless electronic device and from a rear face to a front face of the wireless electronic device, the conductive housing structure comprising portions of the upper and lower antennas. 
     
     
       10. A method of operating a wireless electronic device having upper and lower antennas and having a wireless electronic device housing that comprises portions of the upper and lower antennas, wherein the upper antenna and the lower antennas each operate using the same broadband cellular technology, the method comprising:
 with switching circuitry having a plurality of receive ports, and a plurality of transmit ports, selecting a receive port of the plurality of receive ports and routing radio-frequency signals received from the upper antenna to the selected receive port of the plurality of receive ports during a first time period; 
 with the switching circuitry, routing radio-frequency transmit signals received at the transmit ports to a selected antenna of the upper and lower antennas during a second time period, wherein each of the plurality of receive ports is selectable with the switching circuitry when the upper antenna is selected; and 
 dynamically adjusting a duration of the first time period and a duration of the second time period based on detected bandwidth requirements. 
 
     
     
       11. The method defined in  claim 10  further comprising:
 with control circuitry, selecting which antenna of the upper and lower antennas should be used for wireless transmission; and 
 with the control circuitry, directing the switching circuitry to route the radio-frequency transmit signals from the transmit ports to the selected antenna during the second time period. 
 
     
     
       12. The method defined in  claim 11  wherein the control circuitry comprises a baseband processor, and selecting which antenna of the upper and lower antennas should be used for wireless transmission comprises:
 with the baseband processor, selecting which antenna of the upper and lower antennas should be used for wireless transmission. 
 
     
     
       13. The method defined in  claim 10  further comprising:
 with transceiver circuitry, providing the radio-frequency transmit signals to the transmit ports of the switching circuitry during the second time period. 
 
     
     
       14. The method defined in  claim 13  further comprising:
 with the transceiver circuitry, receiving the radio-frequency signals from the selected receive port of the switching circuitry during the first time period. 
 
     
     
       15. The method defined in  claim 13  wherein routing the radio-frequency transmit signals received at the transmit ports to the selected antenna of the upper and lower antennas—during the second time period comprises:
 routing the radio-frequency transmit signals received at the transmit ports to the selected antenna of the upper and lower antennas during the second time period without changing which receive port is selected during the first time period. 
 
     
     
       16. The method defined in  claim 10 , wherein the plurality of receive ports comprises at least three receive ports that convey signals in three different respective frequency bands of the broadband cellular technology. 
     
     
       17. Wireless communications circuitry that wirelessly communicates using at least first and second antennas, wherein each of the first and second antennas is configured to communicate using a broadband cellular technology, the wireless communications circuitry comprising:
 transceiver circuitry configured to repeatedly toggle between wireless reception operations that occur during a first time period and wireless transmission operations that occur during a second time period, wherein a duration of the first time period and a duration of the second time period are each dynamically adjusted based on detected bandwidth requirements; 
 switching circuitry comprising first and second transmit-receive switches each having a plurality of ports, wherein the first and second transmit-receive switches are configured to provide radio-frequency transmit signals from the transceiver circuitry to only a selected antenna of the first and second antennas during the wireless transmission operations and are further configured to simultaneously route radio-frequency receive signals from both the first and second antennas to the transceiver circuitry during wireless reception operations; and 
 a multi-transmit-port switch that is configured to route only time domain duplexing (TDD) radio-frequency transmit signals, that is coupled to the transceiver circuitry via at least three transmit paths, and that is coupled between the transceiver circuitry and a subset of the plurality of ports on the first and second transmit-receive switches. 
 
     
     
       18. The wireless communications circuitry defined in  claim 17  wherein the multi-transmit-port switch has a first port coupled to the first antenna through the first transmit-receive switch, a second port coupled to the second antenna through the second transmit-receive switch, and a third port that receives the radio-frequency transmit signals from the transceiver circuitry, and the multi-transmit-port switch is operable in a first configuration in which the first port is coupled to the third port and a second configuration in which the second port is coupled to the third port. 
     
     
       19. The wireless communications circuitry defined in  claim 18  wherein the first transmit-receive switch is configured to couple the first antenna to the transceiver circuitry while bypassing the multi-port-transmit switch during wireless reception operations, and the first transmit-receive switch is configured to couple the first antenna to the first port of the multi-port-transmit switch during wireless transmission operations. 
     
     
       20. The wireless communications circuitry defined in  claim 19  wherein the second transmit-receive switch is configured to couple the second antenna to the transceiver circuitry while bypassing the multi-port-transmit switch during wireless reception operations, and the second transmit-receive switch is configured to couple the second antenna to the second port of the multi-port-transmit switch during wireless transmission operations. 
     
     
       21. The wireless communications circuitry defined in  claim 17  further comprising:
 control circuitry operable to determine which antenna of the first and second antennas is provided with the radio-frequency transmit signals by the switching circuitry during wireless transmission operations, wherein the control circuitry comprises baseband circuitry.

Description:
This application claims priority to U.S. provisional patent application No. 61/568,608 filed Dec. 8, 2011, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This invention relates generally to electronic devices, and more particularly, to wireless electronic devices that have two or more antennas. 
     Electronic devices such as handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include cellular telephones, handheld computers, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers. 
     Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, portable electronic devices may use long-range wireless communications to communicate with wireless base stations and may use short-range wireless communications links such as links for supporting the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth® band at 2.4 GHz. 
     Wireless electronic devices may perform antenna transmit diversity to select an optimal antenna to use when transmitting radio-frequency signals. In a conventional wireless electronic device, transmit paths and receive paths are coupled together via duplexing circuitry that isolates transmitted signals from received signals. Because the transmit and receive paths are coupled together, operation of the wireless electronic device may be inefficient. For example, receive paths must be switched along with transmit paths when performing antenna transmit diversity. 
     It would therefore be desirable to be able to provide electronic devices with improved wireless communications capabilities. 
     SUMMARY 
     A wireless electronic device may include antennas formed at different locations on the device. For example, the antennas may be formed at opposite ends of the device. The wireless electronic device may include transceivers that are used to wirelessly communicate in different frequency bands by transmitting and receiving radio-frequency signals in the frequency bands. The wireless electronic device may include switching circuits that accommodate time division multiplexing protocols such as Long Term Evolution-Time Division Duplexing (LTE-TDD) protocols. 
     The switching circuits may perform time division duplexing by toggling between a first configuration in which radio-frequency signals received from the antennas are routed to the transceivers and a second configuration in which the antennas are coupled to antenna switching circuitry. The antenna switching circuitry may receive radio-frequency transmission signals from the transceivers and route the transmission signals to a selected one of the first and second antennas. The antenna switching circuitry may be controlled by control circuitry such as baseband circuitry and/or storage and processing circuitry on the device. The antenna switching circuitry may accommodate antenna transmit diversity without affecting reception of radio-frequency signals (e.g., because the switching circuits that perform time division duplexing may form signal reception paths that are unaffected by the configuration of the antenna switching circuitry). 
     Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with antenna switching capabilities in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram showing how radio-frequency transceiver circuitry may be coupled to one or more antennas within an electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is an illustrative diagram showing antenna transmit diversity operations performed simultaneously with time division multiplexing operations in accordance with an embodiment of the present invention. 
         FIG. 5  is an illustrative diagram of wireless communications circuitry with antenna switching circuitry in accordance with an embodiment of the present invention. 
         FIG. 6  is an illustrative diagram of front end circuitry with antenna switching circuitry in accordance with an embodiment of the present invention. 
         FIG. 7  is a flow chart of illustrative steps that may be performed to control antenna switching circuitry so that antenna transmit diversity is performed without affecting wireless reception paths in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to wireless communications, and more particularly, to wireless electronic devices with switching circuitry that accommodates antenna transmit diversity. 
     The wireless electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may include tablet computing devices (e.g., a portable computer that includes a touch-screen display). Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices may be handheld electronic devices. 
     The wireless electronic devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, tablet computers, and handheld gaming devices. The wireless electronic devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid portable electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples. 
     An illustrative wireless electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  of  FIG. 1  may be, for example, a portable electronic device. 
     Device  10  may have housing  12 . Antennas for handling wireless communications may be housed within housing  12  (as an example). 
     Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. In some situations, housing  12  or portions of housing  12  may be formed from a dielectric or other low-conductivity material, so that the operation of conductive antenna elements that are located in proximity to housing  12  is not disrupted. Housing  12  or portions of housing  12  may also be formed from conductive materials such as metal. An illustrative housing material that may be used is anodized aluminum. Aluminum is relatively light in weight and, when anodized, has an attractive insulating and scratch-resistant surface. If desired, other metals can be used for the housing of device  10 , such as stainless steel, magnesium, titanium, alloys of these metals and other metals, etc. In scenarios in which housing  12  is formed from metal elements, one or more of the metal elements may be used as part of the antennas in device  10 . For example, metal portions of housing  12  may be shorted to an internal ground plane in device  10  to create a larger ground plane element for that device  10 . To facilitate electrical contact between an anodized aluminum housing and other metal components in device  10 , portions of the anodized surface layer of the anodized aluminum housing may be selectively removed during the manufacturing process (e.g., by laser etching). 
     Housing  12  may have a bezel  14 . The bezel  14  may be formed from a conductive material and may serve to hold a display or other device with a planar surface in place on device  10 . As shown in  FIG. 1 , for example, bezel  14  may be used to hold display  16  in place by attaching display  16  to housing  12 . 
     Display  16  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, or any other suitable display. The outermost surface of display  16  may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display  16  or may be provided using a separate touch pad device. An advantage of integrating a touch screen into display  16  to make display  16  touch sensitive is that this type of arrangement can save space and reduce visual clutter. 
     Display screen  16  (e.g., a touch screen) is merely one example of an input-output device that may be used with electronic device  10 . If desired, electronic device  10  may have other input-output devices. For example, electronic device  10  may have user input control devices such as button  19 , and input-output components such as port  20  and one or more input-output jacks (e.g., for audio and/or video). Button  19  may be, for example, a menu button. Port  20  may contain a 30-pin data connector (as an example). Openings  24  and  22  may, if desired, form microphone and speaker ports. In the example of  FIG. 1 , display screen  16  is shown as being mounted on the front face of portable electronic device  10 , but display screen  16  may, if desired, be mounted on the rear face of portable electronic device  10 , on a side of device  10 , on a flip-up portion of device  10  that is attached to a main body portion of device  10  by a hinge (for example), or using any other suitable mounting arrangement. 
     A user of electronic device  10  may supply input commands using user input interface devices such as button  19  and touch screen  16 . Suitable user input interface devices for electronic device  10  include buttons (e.g., alphanumeric keys, power on-off, power-on, power-off, and other specialized buttons, etc.), a touch pad, pointing stick, or other cursor control device, a microphone for supplying voice commands, or any other suitable interface for controlling device  10 . Although shown schematically as being formed on the top face of electronic device  10  in the example of  FIG. 1 , buttons such as button  19  and other user input interface devices may generally be formed on any suitable portion of electronic device  10 . For example, a button such as button  19  or other user interface control may be formed on the side of electronic device  10 . Buttons and other user interface controls can also be located on the top face, rear face, or other portion of device  10 . If desired, device  10  can be controlled remotely (e.g., using an infrared remote control, a radio-frequency remote control such as a Bluetooth® remote control, etc.). 
     Electronic device  10  may have ports such as port  20 . Port  20 , which may sometimes be referred to as a dock connector, 30-pin data port connector, input-output port, or bus connector, may be used as an input-output port (e.g., when connecting device  10  to a mating dock connected to a computer or other electronic device). Device  10  may also have audio and video jacks that allow device  10  to interface with external components. Typical ports include power jacks to recharge a battery within device  10  or to operate device  10  from a direct current (DC) power supply, data ports to exchange data with external components such as a personal computer or peripheral, audio-visual jacks to drive headphones, a monitor, or other external audio-video equipment, a subscriber identity module (SIM) card port to authorize cellular telephone service, a memory card slot, etc. The functions of some or all of these devices and the internal circuitry of electronic device  10  can be controlled using input interface devices such as touch screen display  16 . 
     Components such as display  16  and other user input interface devices may cover most of the available surface area on the front face of device  10  (as shown in the example of  FIG. 1 ) or may occupy only a small portion of the front face of device  10 . Because electronic components such as display  16  often contain large amounts of metal (e.g., as radio-frequency shielding), the location of these components relative to the antenna elements in device  10  should generally be taken into consideration. Suitably chosen locations for the antenna elements and electronic components of the device will allow the antennas of electronic device  10  to function properly without being disrupted by the electronic components. 
     Examples of locations in which antenna structures may be located in device  10  include region  18  (e.g., a first antenna) and region  21  (e.g., a second antenna). Region  18  may be separated from region  21  by a distance D. These are merely illustrative examples. Any suitable portion of device  10  may be used to house antenna structures for device  10  if desired. 
     Wireless electronic devices such as device  10  of  FIG. 2  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support long-range wireless communications such as communications in cellular telephone frequency bands (e.g., ranges of frequencies associated with wireless standards or protocols). Examples of long-range (cellular telephone) bands that may be handled by device  10  include the 800 MHz band, the 850 MHz band, the 900 MHz band, the 1800 MHz band, the 1900 MHz band, the 2100 MHz band, the 700 MHz band, the 2500 MHz band, and other frequency bands. Each long-range band may be associated with a range of frequencies. For example, the 850 MHz band may be associated with frequency range 824-849 MHz and the 2500 MHz band may be associated with frequency range 2500-2570 MHz. Examples of wireless standards or protocols that are associated with the cellular telephone frequency bands include Global System for Mobile (GSM) communications standard, the Universal Mobile Telecommunications System (UMTS) standard, and standards that use technologies such as Code Division Multiple Access, time division multiplexing, frequency division multiplexing, etc. The long-range bands used by device  10  may include the so-called LTE (Long Term Evolution) bands. The LTE bands are numbered (e.g., 1, 2, 3, etc.) and are sometimes referred to as E-UTRA operating bands. As an example, LTE band  7  corresponds to uplink frequencies between 2.5 GHz and 2.57 GHz (e.g., frequencies used to transmit wireless signals to a base station) and downlink frequencies between 2.62 GHz and 2.69 (e.g., frequencies used to receive wireless signals from a base station). 
     Long-range signals such as signals associated with satellite navigation bands may be received by the wireless communications circuitry of device  10 . For example, device  10  may use wireless circuitry to receive signals in the 1575 MHz band associated with Global Positioning System (GPS) communications. Short-range wireless communications may also be supported by the wireless circuitry of device  10 . For example, device  10  may include wireless circuitry for handling local area network links such as Wi-Fi® links at 2.4 GHz and 5 GHz, Bluetooth® links and Bluetooth® Low Energy links at 2.4 GHz, etc. 
     As shown in  FIG. 2 , device  10  may include 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, functions related to radio-frequency transmission and reception such as selection of communications frequencies, 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 Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO (multiple input multiple output) protocols, antenna diversity protocols, etc. Wireless communications operations such as communications frequency selection operations may be controlled using software stored and running on device  10  (e.g., stored and running on storage and processing circuitry  28 ). 
     Electronic device  10  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Therefore, electronic device  10  may sometimes be referred to as a wireless device or a wireless electronic device. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, baseband circuitry, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry such as front-end 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 for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry that handles 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications and/or handles the 2.4 GHz band for Bluetooth® communications. Circuitry  34  may include cellular telephone transceiver circuitry for handling wireless communications in cellular telephone bands such as at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, the LTE bands, and other bands (as examples). Circuitry  34  may handle voice data and non14 voice data. If desired, wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. 
     Wireless communications circuitry  34  may include one or more 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. 
     Antenna diversity schemes may be implemented in which multiple redundant antennas are used in handling communications for a particular band or bands. In an antenna diversity scheme, storage and processing circuitry  28  may select which antenna to use in real time based on signal strength measurements or other data. For example, storage and processing circuitry  28  may select which antenna to use for LTE communications with a base station. In multiple-input-multiple-output (MIMO) schemes, multiple antennas may be used to transmit and receive multiple data streams, thereby enhancing data throughput. In antenna receive diversity schemes, multiple antennas may be used to receive radio-frequency signals, and the received signals may be combined to enhance received signal quality. 
     Illustrative locations in which antennas  40  may be formed in device  10  are shown in  FIG. 3 . As shown in  FIG. 3 , electronic device  10  may have a housing such as housing  12 . Housing  12  may include plastic walls, metal housing structures, structures formed from carbon-fiber materials or other composites, glass, ceramics, or other suitable materials. Housing  12  may be formed using a single piece of material (e.g., using a unibody configuration) or may be formed from a frame, housing walls, and other individual parts that are assembled to form a completed housing structure. The components of device  10  that are shown in  FIG. 1  may be mounted within housing  12 . Antenna structures  40  may be mounted within housing  12  and may, if desired, be formed using parts of housing  12 . For example, housing  12  may include metal housing sidewalls, peripheral conductive members such as band-shaped members (with or without dielectric gaps), conductive bezels, and other conductive structures that may be used in forming antenna structures  40 . 
     As shown in  FIG. 3 , antenna structures  40  may be coupled to transceiver circuitry  90  by paths such as paths  45 . Paths  45  may include transmission line structures such as coaxial cables, microstrip transmission lines, stripline transmission lines, etc. Paths  45  may also include impedance matching circuitry, filter circuitry, and switching circuitry. Impedance matching circuitry may be used to ensure that antennas  40  are efficiently coupled to transceiver circuitry  90  in communications bands of interest. Filter circuitry may be used to implement frequency-based multiplexing circuits such as diplexers, duplexers, and triplexers. Switching circuitry may be used to selectively couple antennas  40  to desired ports of transceiver circuitry  90 . For example, in one operating mode a switch may be configured to route one of paths  45  to a given antenna and in another operating mode the switch may be configured to route a different one of paths  45  to the given antenna. The use of switching circuitry between transceiver circuitry  90  and antennas  40  allows device  10  to support multiple communications bands of interest with a limited number of antennas. 
     In a device such as a cellular telephone that has an elongated rectangular outline, it may be desirable to place antennas  40  at one or both ends of the device. As shown in  FIG. 3 , for example, some of antennas  40  may be placed in upper end region  42  of housing  12  and some of antennas  40  may be placed in lower end region  44  of housing  12 . The antenna structures in device  10  may include a single antenna in region  42 , a single antenna in region  44 , multiple antennas in region  42 , multiple antennas in region  44 , or may include one or more antennas located elsewhere in housing  12 . 
     Antenna structures  40  may be formed within some or all of regions such as regions  42  and  44 . For example, an antenna such as antenna  40 T- 1  may be located within region  42 - 1  or an antenna such as antenna  40 T- 2  may be formed that fills some or all of region  42 - 1 . An antenna such as antenna  40 B- 1  may fill some or all of region  44 - 2  or an antenna such as antenna  40 B- 2  may be formed in region  44 - 1 . These types of arrangements need not be mutually exclusive. For example, region  44  may contain a first antenna such as antenna  40 B- 1  and a second antenna such as antenna  40 B- 2 . 
     Transceiver circuitry  90  may contain transmitters such as transmitters  48  and receivers such as receivers  50 . Transmitters  48  and receivers  50  may be implemented using one or more integrated circuits (e.g., cellular telephone communications circuits, wireless local area network communications circuits, circuits for Bluetooth® communications, circuits for receiving satellite navigation system signals). Transceiver circuitry  90  may be formed with associated power amplifier circuits for increasing transmitted signal power, low noise amplifier circuits for increasing signal power in received signals, other suitable wireless communications circuits, and combinations of these circuits. 
     Transceiver circuitry may communicate in frequency bands using time division multiplexing protocols. For example, the LTE standard may use time division multiplexing protocols such as protocols that use time division duplexing for selected LTE frequency bands (e.g., LTE bands  33 - 43 ). Wireless electronic devices that communicate using LTE bands  33 - 43  may be required to perform time division duplexing operations in which transmitted signals and received signals are each assigned to predetermined time slots. LTE bands  33 - 43  may therefore be referred to as Long Term Evolution-Time Division Duplexing (LTE-TDD) frequency bands. 
       FIG. 4  is an illustrative diagram showing how wireless communications using time division duplexing operations may be partitioned in time into radio-frequency signal reception and radio-frequency signal transmission. As shown in  FIG. 4 , signal reception may be assigned to periods (portions) of time  102  and signal transmission may be assigned to periods of time  104 . Each period of time may correspond to one or more time slots (e.g., a minimum length of time defined by a given protocol for signal reception or transmission). The length of each period of time (e.g., the number of time slots assigned to that period of time) may be selected based on bandwidth requirements of reception and transmission operations. For example, if device  10  transmits more data than it receives, transmission time periods  104  may be allocated more time slots than reception time periods  102 . The time slots allocated to each time period may be adjusted dynamically to accommodate changing bandwidth requirements. 
     Device  10  may perform antenna transmit diversity operations to select an optimal antenna for transmission time periods  104 . For example, during time period T 1 , device  10  may identify that an upper antenna such as antenna  40 T- 1  should be used for radio-frequency transmissions and during time period T 2 , device  10  may identify that a lower antenna such as antenna  40 B- 1  should be used for radio-frequency transmissions. In this example, radio-frequency signals may be transmitted using upper antenna  40 T- 1  during time periods  104  that lie within time period T 1  and radio-frequency signals may be transmitted using lower antenna  40 B- 1  during time periods  104  that lie within time period T 2 . 
     It may be desirable to perform antenna transmit diversity operations without affecting wireless reception or other normal operations of device  10 .  FIG. 5  shows how wireless communications circuitry  34  (e.g., wireless communications circuitry that may be used in device  10  to handle radio-frequency communications) may be provided with antenna switching circuitry  112  that accommodates antenna transmit diversity operations for LTE-TDD frequency bands (or other frequency bands associated with time division multiplexing protocols) without affecting wireless reception in the LTE-TDD frequency bands. Wireless communications circuitry  34  may include front-end circuitry  44  that handles radio-frequency signals that are transmitted and received by wireless communications circuitry  34 . Front-end circuitry  44  may include switching circuitry such as switching circuits  64 A,  64 B, and circuitry  112 . Front-end circuitry  44  may include filtering circuitry such as duplexer  54  and other components used to handle radio-frequency signals. 
     Wireless communications circuitry  34  may include antennas  40 A and  40 B. Antennas  40 A and  40 B may, for example, correspond to upper and lower antennas  40 T- 1  and  40 B- 1  of  FIG. 3 . Antennas  40 A and  40 B may be coupled to respective switching circuits  64 A and  64 B at terminals (ports) T 10  and T 14 . Switching circuits  64 A and  64 B may have ports that are associated with LTE-TDD signal reception paths and ports associated LTE-TDD signal transmission paths. For example, ports T 6  and T 12  may be associated with reception paths for LTE-TDD bands TDB 1  and ports T 7  and T 13  may be associated with reception paths for LTE-TDD band TDB 2 . Radio-frequency signals may be received from a selected one of antennas  40 A and  40 B via the LTE-TDD signal reception paths or, if desired, may be received simultaneously from both antennas  40 A and  40 B (e.g., by performing antenna receive diversity). 
     Ports T 8  and T 11  may be associated with radio-frequency signal transmission paths (e.g., transmission paths between transceiver circuitry  90  and antennas  40 A and  40 B. Switching circuits  64 A and  64 B may be used to perform time division duplexing by alternately coupling ports associated with signal reception and signal transmission to antennas  40 A and  40 B. For example, during time periods  102  of  FIG. 4 , switching circuit  64 A may be configured to couple port T 6  to port T 10  and during time periods  104 , switching circuit  64 A may be configured to couple port T 8  to port T 10 . In other words, switching circuits  64 A and  64 B may be controlled to perform time division duplexing by repeatedly toggling between receive and transmit paths. Switching circuits  64 A and  64 B may be controlled via paths  62  (e.g., controlled by control circuitry such as baseband circuitry  46 , storage and processing circuitry  28 , or dedicated control circuitry associated with switching circuits  64 A and  64 B). 
     Power amplifiers  52  may be used to amplify transmitted radio-frequency signals to a desired power level (e.g., a power level sufficient for other wireless devices to receive the transmitted signals). Low noise amplifiers  60  may be used to amplify received radio-frequency signals so that the received radio-frequency signals have sufficient strength to be processed by transceiver circuitry  90 . 
     Antenna switching circuitry  112  may be interposed between transceiver circuitry  90  and switching circuits  64 A and  64 B. Antenna switching circuitry  112  may include ports T 1  and T 2  that are associated with signal transmissions in respective LTE-TDD frequency bands. For example, port T 1  may be associated with signals transmitted in LTE-TDD frequency band TDB 1  (e.g., TDB 1  TX) and port T 2  may be associated with signals transmitted in LTE-TDD frequency band TDB 2  (e.g., TDB 2  TX). Antenna switching circuitry  112  may be configured via control path  114  to selectively route transmitted signals to either antenna  40 A or  40 B (e.g., by selectively coupling ports T 1  and T 2  to either ports T 4  or T 5 ). In other words, antenna switching circuitry  112  may be configured to form transmit paths between transceiver circuitry  90  and either antennas  40 A and  40 B. Control signals may be provided to antenna switching circuitry  112  via control path  114  from storage and processing circuitry  28 , baseband circuitry  46 , or any desired control circuitry. 
     Antenna switching circuitry  112  may accommodate antenna transmit diversity without affecting normal operations of wireless communications circuitry  34  (e.g., without affecting LTE-FDD signal reception). Consider the scenario in which wireless communications circuitry  34  communicates with a base station such as base station  6  using LTE-TDD frequency band TDB 1 . Wireless communications circuitry  34  may initially use antenna  40 A to transmit radio-frequency signals to base station  6  in frequency band TDB 1  (e.g., switching circuitry  112  may be configured to couple port T 1  to port T 4 , thereby forming a signal transmission path between transceiver circuitry and antenna  40 A). Device  10  may monitor the communications with base station  6  and determine that antenna  40 B should be used for transmissions in frequency band TDB 1  (e.g., based on received signal strength or other indicators of communications link quality). In response to determining that antenna  40 B should be used for communications with base station  6 , device  10  may configure switching circuitry  112  to couple port T 1  to port T 5 , thereby routing transmission signals in frequency band TDB 1  from transceiver circuitry  90  to antenna  40 B. In this scenario, radio-frequency signal reception associated with LTE-TDD frequency band TDB 1  may be unaffected by the change in the transmission signal path, because antenna switching circuitry  114  is only configured to adjust signal transmission paths. 
     Wireless communications circuitry  34  may accommodate other wireless standards and protocols via additional ports on switching circuits  64 A and  64 B. For example, wireless standards such as Long Term Evolution-Frequency Division Duplexing (LTE-FDD) may be handled by duplexer  54  that is coupled to port T 9  of switching circuit  64 A. In this scenario, duplexer  54  may be formed from filters such as high pass and low pass filters that perform frequency division duplexing by partitioning radio-frequency signals into transmit frequencies and receive frequencies. 
     The example of  FIG. 5  in which antenna switching circuitry  112  has two ports associated with two LTE-TDD frequency bands is merely illustrative. If desired, antenna switching circuitry  112  may include any desired number of ports associated with multiple LTE-TDD frequency bands. If desired, antenna switching circuitry  112  may be coupled to multiple antennas (e.g., coupled to two or more antennas via switching circuits such as switching circuits  64 A and  64 B and/or filtering circuitry) and be configured to perform antenna transmit diversity without affecting signal reception paths by routing transmitted signals to a selected one of the antennas. If desired, antenna switching circuitry  112  may be used to perform antenna transmit diversity for any wireless standards that use time division multiplexing protocols to partition transmitted signals from received signals. 
     The example of  FIG. 5  in which switching circuits  64 A and  64 B are each coupled to a single antenna is merely illustrative. If desired, switching circuits  64 A and  64 B may be coupled to multiple antennas via additional filtering and switching circuitry (not shown). The additional filtering and switching circuitry may accommodate additional wireless technologies such as Wi-Fi®, Bluetooth®, GPS, etc. 
       FIG. 6  is a diagram showing how front-end circuitry  44  may be provided with switching circuitry  152  having antenna switching circuitry  112  that receives transmitted signals at multiple frequency bands via ports T. Switching circuitry  152  may be coupled to two or more antennas (e.g., antennas  40 A and  40 B). Switching circuitry  152  may have ports B 1  RX, B 2  RX, etc. to which signals received from the antennas are provided. Switching circuitry  112  may include ports ANT 1  and ANT 2  that are assigned to antennas  40 A and  40 B, respectively. 
     To communicate using time division multiplexing protocols such as LTE-TDD, switching circuitry  152  may be configured via control path  62  to alternately couple each antenna to a selected receive port (e.g., ports B 1  RX, B 2 , RX, etc.) and an assigned transmit port of antenna switching circuitry  112 . For example, antenna  40 A may be coupled to port B 1  RX during times  102  of  FIG. 4  and coupled to port ANT 1  during times  104 . As another example, antenna  40 B may be coupled to port ANT 2  during times  104 . By providing switching circuitry  152  with antenna switching circuitry  112  that is dedicated to signal transmit paths, antenna transmit diversity may be performed without affecting receive paths. 
       FIG. 7  shows a flowchart of illustrative steps that may be performed by wireless communications circuitry (e.g., by control circuitry such as storage and processing circuitry  28  or baseband circuitry  46  in wireless communications circuitry  34 ) to perform antenna transmit diversity without affecting wireless reception. 
     In step  202 , the wireless communications circuitry may select an antenna for transmission. For example, the wireless communications circuitry may communicate with a base station such as base station  6  in a given frequency band using a time division multiplexing protocol such as LTE-TDD. In this scenario, the wireless communications circuitry may select the antenna for transmission based on received signal strength or other indicators of communications link quality between the wireless communications circuitry and the base station. 
     In step  204 , the wireless communications circuitry may configure dedicated switching circuitry so that transmitted signals are routed to the selected antenna without affecting signal reception (e.g., without modifying receive paths in the wireless communications circuitry). For example, the wireless communications circuitry may provide control signals to antenna switching circuitry  112  that direct circuitry  112  to route transmit signals to the selected antenna. The control signals may be provided to antenna switching circuitry  112  via path  114  without modifying control signals that are provided to switching circuits  64 A and  64 B via path  62 . Processing may then return to step  202  via path  206  to perform antenna transmit diversity operations without affecting wireless reception. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20120928
Publication Date: 20160913
Grant Date: 20160913
Priority Date: 20111208
Inventors: YU QISHAN
YANG JAMES T.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B7/0602", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0868", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0868", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0602", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/44", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0602", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0868", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 48572411