PATENT DOCUMENT

Publication Number: US-8432836-B2
Application Number: US-94293710-A
Country: US
Kind Code: B2

Title: Wireless circuitry with simultaneous voice and data capabilities and reduced intermodulation distortion

Abstract:
An electronic device has wireless communications circuitry that includes transmitters and receivers. The transmitters and receivers may share an antenna. Transmitted signals from multiple transmitters may be merged using a combining circuit. Merged signals from the transmitter may be conveyed to the antenna through a circulator. The circulator may route incoming signals from the antenna to receivers. The receivers may be coupled to the circulator through a filter. An additional filter may be interposed between the circulator and the antenna. An additional transmitter may transmit signals through the antenna using the additional filter. An additional receiver may receive some of the incoming signals that are received by the antenna through the additional filter.

Claims:
What is claimed is: 
     
       1. Wireless communications circuitry configured to operate in different communications bands without producing excessive interference between the different communications bands, comprising:
 a first radio-frequency transmitter that operates in a first transmit communications band; 
 a second radio-frequency transmitter that operates in a second transmit communications band; 
 a radio-frequency receiver that operates in a receive communications band; 
 an antenna that is shared by the first and second radio-frequency transmitters and the radio-frequency receiver; 
 a circulator; 
 a first path coupled between a first port of the circulator and the antenna, wherein the first path conveys signals in the first transmit communications band, the second transmit communications band, and the receive communications band; 
 a second path coupled between a second port of the circulator and the radio-frequency receiver that conveys signals in the receive communications band; and 
 a third path coupled to a third port of the circulator that conveys signals in the first and second transmit communications bands, wherein the circulator is configured to route the signals in the first and second transmit communications bands from the third path to the first path, to route the signals in the receive communications band from the first path to the second path, and to isolate the radio-frequency receiver from noise on the third path. 
 
     
     
       2. The wireless communications circuitry defined in  claim 1  further comprising a duplexer, wherein the first radio-frequency transmitter is coupled to the duplexer, wherein the second radio-frequency transmitter is coupled to the duplexer, and wherein the duplexer is coupled to the circulator by the third path. 
     
     
       3. The wireless communications circuitry defined in  claim 2  wherein the first transmit communications band has a frequency range of 777 to 787 MHz and wherein the first radio-frequency transmitter is configured to transmit radio-frequency signals in a frequency range of 777 to 787. 
     
     
       4. The wireless communications circuitry defined in  claim 3  wherein the second transmit communications band has a frequency range of 824 to 849 MHz and wherein the second radio-frequency transmitter is configured to transmit radio-frequency signals in a frequency range of 824 to 849 MHz. 
     
     
       5. The wireless communications circuitry defined in  claim 4  wherein the receive communications band has a frequency range of 869 to 894 MHz and wherein the radio-frequency receiver is configured to receive radio-frequency signals in a frequency range of 869 to 894 MHz. 
     
     
       6. The wireless communications circuitry defined in  claim 1  further comprising a diplexer interposed between the circulator and the antenna, wherein the diplexer has first, second, and third ports, wherein the first diplexer port is coupled to the antenna, wherein the second diplexer port is coupled to the first path, and wherein the third diplexer port is coupled to a filter. 
     
     
       7. The wireless communications circuitry defined in  claim 6  wherein the filter comprises a duplexer. 
     
     
       8. The wireless communications circuitry defined in  claim 7  further comprising a third radio-frequency transmitter that is coupled to the duplexer and an additional radio-frequency receiver that is coupled to the duplexer. 
     
     
       9. The wireless communications circuitry defined in  claim 8  further comprising an additional duplexer that is coupled between the second path and the radio-frequency receiver. 
     
     
       10. The wireless communications circuitry defined in  claim 6  wherein the filter comprises a first duplexer and wherein the wireless communications circuitry further comprises:
 a second duplexer that is coupled between the second path and the radio-frequency receiver; and 
 a third duplexer, wherein the first radio-frequency transmitter is coupled to the third duplexer, wherein the second radio-frequency transmitter is coupled to the third duplexer, and wherein the third duplexer is coupled to the circulator by the third path. 
 
     
     
       11. The wireless communications circuitry defined in  claim 1  further comprising a combiner, wherein the first radio-frequency transmitter is coupled to the combiner, wherein the second radio-frequency transmitter is coupled to the combiner, and wherein the combiner has a port on which signals from the first and second radio-frequency transmitters are provided to the third path. 
     
     
       12. The wireless communications circuitry defined in  claim 11  wherein the combiner comprises a Wilkinson splitter. 
     
     
       13. The wireless communications circuitry defined in  claim 12  further comprising a first bandpass filter interposed between the first radio-frequency transmitter and the Wilkinson splitter and a second bandpass filter interposed between the second radio-frequency transmitter and the Wilkinson splitter. 
     
     
       14. The wireless communications circuitry defined in  claim 1  further comprising a diplexer, wherein the first radio-frequency transmitter is coupled to the diplexer, wherein the second radio-frequency transmitter is coupled to the diplexer, and wherein the diplexer has a port on which signals from the first and second radio-frequency transmitters are provided to the third path. 
     
     
       15. The wireless communications circuitry defined in  claim 14  further comprising a first bandpass filter interposed between the first radio-frequency transmitter and the diplexer and a second bandpass filter interposed between the second radio-frequency transmitter and the diplexer. 
     
     
       16. Wireless communications circuitry, comprising:
 first, second, and third radio-frequency transmitter circuits that operate in first, second, and third transmit communications bands, respectively; 
 first, second, and third radio-frequency receiver circuits that operate in first, second, and third receive communications bands, respectively; 
 an antenna that is shared by the first, second, and third radio-frequency transmitter circuits and the first, second, and third radio-frequency receiver circuits; and 
 a circulator that has a first port that receives signals in the first and second transmit communications bands from the first and second radio-frequency transmitter circuits, a second port that is coupled to the antenna, and a third port through which the first and second receiver circuits receive signals in the first and second receive communications bands, wherein the circulator is configured to route the signals in the first and second transmit communications bands from the first port to the second port, to route signals in the first and second receive communications bands from the second port to the third port, and to isolate the first and second radio-frequency receiver circuits from noise at the first port of the circulator. 
 
     
     
       17. The wireless communications circuitry defined in  claim 16  further comprising a diplexer that is coupled between the antenna and the second port, wherein the diplexer receives signals in the third transmit communications band from the third radio-frequency transmitter and provides signals in the third receive communications band to the third radio-frequency receiver. 
     
     
       18. The wireless communications circuitry defined in  claim 17  further comprising a first duplexer, a second duplexer, and a third duplexer, wherein the third radio-frequency transmitter transmits signals in the third transmit communications band to the diplexer through the first duplexer, wherein the third radio-frequency receiver receives signals in the third receive communications band from the diplexer through the first duplexer, wherein the first and second radio-frequency transmitters transmit signals in the first and second transmit communications band to the first port of the circulator through the second duplexer, and wherein the first and second radio-frequency receivers receive signals in the first and second receive communications band from the third port of the circulator through the third duplexer. 
     
     
       19. Wireless communications circuitry, comprising:
 a plurality of transmitters that transmits radio-frequency signals in respective transmit communications bands; 
 a receiver that operates in a receive communications band; 
 an antenna through which the radio-frequency signals are transmitted; 
 a filter that receives the radio-frequency signals in the transmit communications bands from the plurality of transmitters and that combines the radio-frequency signals received from the plurality of transmitters to produce merged signals; and 
 a circulator having a first port that receives the merged radio-frequency signals from the filter, a second port that is coupled to the antenna, and a third port through which signals in the receive communications band are routed to the receiver, wherein the circulator is configured to route the merged signals from the first port to the second port, to route signals in the receive communications band from the second port to the third port, and to isolate the receiver from noise at the first port of the circulator. 
 
     
     
       20. The wireless communications circuitry defined in  claim 19  further comprising:
 a diplexer that is coupled between the circulator and the antenna; and 
 an additional receiver that is coupled to the diplexer, wherein the diplexer routes incoming signals from the antenna to the circulator and routes additional incoming signals from the antenna to the additional receiver.

Description:
BACKGROUND 
     This relates generally to wireless communications circuitry, and more particularly, to circuitry in wireless electronic devices that allows communications bands for voice and data to be simultaneously operated without producing excessive interference. 
     Electronic devices such as cellular telephones contain wireless circuitry that is capable of handling a variety of cellular telephone communications bands. These bands may include bands that support communications protocols that are associated with voice telephone calls. The bands handled by a device may also support communications protocols associated with data communications. 
     It can be challenging to operate the wireless circuitry in an electronic device in more than one band at a time due to the potential for interference. Not all wireless components perform ideally. For example, filter components may exhibit nonlinearities that can give rise to intermodulation distortion when signals associated with multiple communications bands are simultaneously active. Interference from intermodulation distortion and other effects may make it difficult or impossible to satisfy desired performance criteria in a device. For example, the level of interference that is produced when attempting to simultaneously operate certain voice and data bands in a device may calls to be dropped or may reduce data transfer rates to undesirably low levels. 
     It would therefore be desirable to be able to provide wireless communications circuitry that satisfactorily handles multiple communications bands of interest such as bands associated with voice and data communications. 
     SUMMARY 
     An electronic device may be provided with wireless communications circuitry. The wireless communications circuitry may include radio-frequency transmitters and receivers for handling wireless communications. The transmitters and receivers may share an antenna. 
     A circulator and filtering circuitry may be used to route signals from the transmitters to the antenna. Incoming signals that have been received by the antenna from an external source may be routed to the receivers by the circulator and filtering circuitry. 
     The circulator and filtering circuitry may include components such as bandpass filters, duplexers, diplexers, and combiners formed from passive components. 
     With one suitable arrangement, there are at least first, second, and third transmitters in the wireless communications circuitry and at least first, second, and third receivers in the wireless communications circuitry. Each transmitter may transmit radio-frequency signals in a different respective transmit communications band and each receiver may receiver radio-frequency signals in a different respective receive communications band. 
     Signals from the first and second transmitters may be merged onto a path that is coupled to the circulator using a duplexer, using a pair of respective bandpass filters and a passive combiner such as a Wilkinson splitter, using a pair of respective bandpass filters and a diplexer, or using other signal multiplexing circuitry. The circulator may have first, second, and third ports. The merged signals from the first and second transmitters may be received at the first port of the circulator and may be supplied to the antenna at the second port of the circulator. 
     Incoming signals from the antenna may be routed from the second port to the third port by the circulator. The first and second receivers may receive the incoming signals from the third port of the circulator. A filter circuit such as a duplexer may be used to divide the signals from the third port into a first path for the first receiver and a second path for the second receiver. 
     A diplexer or other filter may be interposed between the second port of the circulator and the antenna. The diplexer may route some incoming signals to the circulator and may route some incoming signals to an additional duplexer. The additional duplexer may be used to couple the third transmitter and the third receiver to the diplexer. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram showing how radio-frequency transceiver circuitry may be coupled to one or more antennas within an electronic device of the type shown in  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 3  is a table showing illustrative communications bands that may be handled using circuitry of the type shown in  FIG. 2  in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of illustrative wireless communications circuitry of the type that may be used in a device such as the device of  FIG. 1  while handling bands such as the bands of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of illustrative transmitter circuitry based on a combiner circuit that may be used in wireless communications circuitry of the type shown in  FIG. 4  in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of illustrative transmitter circuitry based on a diplexer circuit and bandpass filters that may be used in wireless communications circuitry of the type shown in  FIG. 4  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as device  10  of  FIG. 1  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 bands. 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, and other bands. 
     Device  10  may support one or more different cellular telephone standards. Examples of cellular telephone standards that may be supported by device  10  include: the Global System for Mobile Communications (GSM) “2G” cellular telephone standard, the Evolution-Data Optimized (EVDO) cellular telephone standard, the “3G” Universal Mobile Telecommunications System (UMTS) cellular telephone standard, the “3G” Code Division Multiple Access 2000 (CDMA 2000) cellular telephone standard, and the “4G” Long Term Evolution (LTE) cellular telephone standard. Other cellular telephone standards may be used if desired. These cellular telephone standards are merely illustrative. 
     Different cellular telephone standards may be implemented using different respective cellular telephone protocols. In a device that supports more than one cellular telephone standard, multiple protocols may be implemented. The cellular bands that are used in device  10  are sometimes given names that are associated with particular protocols. For example, communications (e.g., data communications) that involve the LTE cellular telephone standard may be handled using LTE bands. The LTE bands are numbered (e.g., Band  1 , Band  2 , Band  3 , etc.) and are sometimes referred to as E-UTRA operating bands. As another example, communications (e.g., voice communications) that involve the CDMA 2000 cellular telephone standard may be handled using CDMA 2000 bands. The CDMA 2000 bands are sometimes referred to as band classes (e.g., band class  0 , band class  1 , etc.). Certain bands (i.e., LTE bands and CDMA band classes) are sometimes described herein as examples. In general, however, device  10  may communicate using radio-frequency signals of any suitable frequency. 
     In a typical device configuration, one, two, or more than two different cellular telephone standards may be supported. In configurations where multiple cellular telephone standards are supported, it may be desirable to operate device  10  while simultaneously using multiple different communications protocols. Illustrative configurations in which voice calls may be handled using a protocol such as the CDMA 2000 protocol and in which data communications may be handled using a protocol such as the LTE protocol are sometimes described herein as an example. This type of arrangement may allow a user to simultaneously hold a voice conversation (using a CDMA 2000 voice link) while handling data communications (using an LTE link). This type of configuration is, however, merely illustrative. Device  10  may support any suitable number of cellular telephone standards and may perform any suitable number of simultaneous communications activities. 
     When a device such as device  10  is operating using multiple different communications frequencies simultaneously, there is a potential for interference. For example, if signals are being conveyed simultaneously in multiple nearby cellular telephone bands, there is a potential for intermodulation distortion and other interference. Intermodulation distortion may arise due to the nonlinear behavior of filters and other wireless components. If care is not taken, interference can cause calls to be dropped and data communications to be disrupted. 
     To ensure that the operation of the wireless circuitry of device  10  is not impeded by interference, device  10  preferably includes wireless circuitry that mitigates the effects of intermodulation distortion by creating sufficient isolation between nearby communications band. Components such as circulators, bandpass filters, duplexers, and diplexers may be used to enhance isolation. These components may be included in wireless communications circuitry  34  of device  10 . 
     As shown in  FIG. 1 , wireless communications circuitry  34  may form part of input-output circuitry  30  in device  10 . 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 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 handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in cellular telephone bands such as at 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz and other bands (as examples). Circuitry  38  may handle voice data and non-voice data. 
     Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as 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 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 structure, 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 device  10  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. In multiple-input-multiple-output (MIMO) schemes, multiple antennas may be used to transmit and receive multiple data streams, thereby enhancing data throughput. 
     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, baseband modules, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, email applications, media playback applications, operating system functions, functions related to communications band selection during radio-frequency transmission and reception operations, 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 (multiple input multiple output) protocols, antenna diversity protocols, etc. Wireless communications operations such as communications band selection operations may be controlled using software stored and running on device  10  (i.e., stored and running on storage and processing circuitry  28  and/or storage and processing circuitry in input-output circuitry  30 ). 
     Input-output circuitry  30  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, click wheels, 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. 
     Illustrative cellular telephone transceiver circuitry  38  and antennas  40  that may be used in wireless communications circuitry  34  of  FIG. 1  are shown in  FIG. 2 . As shown in  FIG. 2 , cellular telephone transceiver circuitry  38  may be coupled to one or more antennas  40  using respective transmission lines  60 . Transmission lines  60  may include coaxial cables, microstrip transmission line structures, stripline transmission lines structures, combinations of transmission lines of these types, or other suitable transmission lines. Front-end module  58  or other suitable circuitry may be used to connect multiple power amplifiers such as power amplifier  54  and multiple low noise amplifiers such as low noise amplifier  56  to antennas  40 . Front-end module  58  may include switches, filtering circuitry, matching networks, and other circuits that form an interface between antennas  40  and amplifiers such as amplifiers  54  and  56 . 
     There may be multiple power amplifiers  54  and multiple low noise amplifiers  56  in circuitry  38 . For example, each communications band or part of a communications band may have a respective power amplifier and a respective low noise amplifier. Power amplifiers  54  may be used to increase the strength of transmitted radio-frequency signals before these signals are transmitted over the air using antennas  40 . Low noise amplifiers  56  may be used to increase the strength of incoming radio-frequency signals that have been received from external sources using antennas  40 . 
     Circuitry in device  10  such as storage and processing circuitry  28  may generate and consume data (including voice data for voice calls and non-voice data). Digital data that is to be transmitted may be provided to a circuit such as baseband module  46  at path  44  (e.g., from a microprocessor or other storage and processing circuitry  28 ). Baseband module  46  may modulate these signals in accordance with a desired cellular telephone standard and modulation scheme and may provide corresponding output signals on an appropriate path (path  48 ) for transmission by a corresponding transmitter (transmitter  50 ). Transmitter  50  may generate corresponding radio-frequency signals that are amplified by power amplifier  54  and transmitted over antenna(s)  40 . When incoming radio-frequency signals are received by antenna(s)  40 , these signals may be amplified using low noise amplifier  56  and passed to a corresponding receiver  52 . The receiver may use path  50  to provide corresponding demodulated output to baseband module  46 . Baseband module  46  may provide corresponding digital data signals on path  44 . 
     When transmitting wireless signals using the wireless circuitry of  FIG. 2 , baseband module  46  may select an appropriate output path  48  and transmitter  50  based on which communications band is being used. If, for example, a first band is being used such as a band associated with a voice telephone call, baseband module  46  may supply its output to a first output path and a first transmitter. If, however, a second band is being used such as a band associated with a data transmission activity, baseband module  46  may supply its output to a second output path and second corresponding transmitter. Receiver selection may also be adjusted depending on band usage. For example, if incoming radio-frequency signals that are associated with one band are being received, a first of receivers  52  may be used, whereas a second of receivers  52  may be used when incoming radio-frequency signals are being received that are associated with another band. 
     The filter and switching circuitry of front-end module  58  of  FIG. 2  can ensure that transmitted signals and received signals are routed between antenna(s)  40  and appropriate transmit and receive paths in transceiver circuitry  38 . To minimize space, it may be desirable, for example, to route transmitted signals and received signals for multiple communications bands through a common antenna. For example, it may be desirable to transmit signals for multiple communications bands and to receive signals for multiple communications bands using the same antenna. This scheme may be applied in devices that include one antenna or multiple antennas. In systems that include multiple antennas, each of the multiple antennas may be shared between multiple respective communications bands, rather than dedicating a different antenna to each band. 
     In systems that support simultaneous use of multiple bands (e.g., to support a simultaneous voice telephone call and data communications link), there is a potential for nearby bands to be in simultaneous use. Particularly in a system with a shared antenna, this can lead to the potential for signal interference. 
     Consider, as an example, the illustrative communications bands shown in the table of  FIG. 3 . These bands, which may represent only a subset of the bands supported by wireless communications circuitry  34 , may include LTE bands such as LTE Band  13  (“B 13 ”) for handling data communications, and CDMA 2000 bands such as Band Class  0  (“BC 0 ”) and Band Class  1  (“BC 1 ”). As shown in the  FIG. 3  table, each of these bands may have two associated sub-bands. For example, in band B 13 , signals may be transmitted in the range of 777 to 787 MHz (a first band sometimes referred to as band B 13  TX) and signals may be received in the range of 746 to 756 MHz (a second band sometimes referred to as band  13  RX). In band BC 0 , the frequency range of 824 to 849 MHz may be associated with a transmit band (band BC 0  TX) and the frequency range of 869 to 894 MHz may be associated with a receive band (band BC 0  RX). Band BC 1  may likewise include a transmit band (e.g., a band covering signal frequencies from 1850 to 1910 MHz that is sometimes referred to as band BC 1  TX) and a receive band (e.g., a band covering signal frequencies from 1930 to 1990 MHz that is sometimes referred to as band BC 1  RX). 
     In wireless communications circuits that support communications with the TX and RX bands associated with bands B 13 , BC 0 , and BC 1 , it can be challenging to route signals between an antenna and respective transmitters and receivers through front end circuitry  58  of  FIG. 2  without interference. For example, it can be challenging to handle signals in the B 13  TX band at 777 to 787 MHz simultaneously with the signals in the adjacent BC 0  TX band at 824 to 849 MHz without creating intermodulation distortion (IMD) noise that affect other bands such as the BC 0  RX band. In particular, noise in band BC 0  RX may be produced by frequencies corresponding to the second harmonic of band BC 0  TX minus the fundamental frequencies of band B 13  TX. 
     The close spacing and frequency interrelationships between these bands makes it possible for interference to be created by intermodulation distortion as signals pass through components such as filters that exhibit nonlinearities. The impact of this type of interference may be mitigated by satisfactory selection of circuitry for front-end module  58 . Circuitry of the type that may be used in front-end module  58  or other filtering and switching circuitry that is interposed between an antenna and the transceiver circuitry of device  10  is shown in  FIG. 4 . The illustrative circuit configuration of  FIG. 4  may help mitigate the impact of interference due to the simultaneous operation of multiple communications bands (e.g., voice and data bands). 
     As shown in  FIG. 4 , over-the-air radio-frequency signals may be received by antenna  40  and, using filter circuitry  58 , may be routed to respective receivers  52 - 1 ,  52 - 2 , and  52 - 3  and their associated output paths  50 - 1 ,  50 - 2 , and  50 - 3  based on signal frequency. In this capacity, filter circuitry  58  serves as a demultiplexer circuit that separates out a multi-band antenna signal on path  60  into signals in respective bands. The received signals on paths  50 - 1 ,  50 - 2 , and  50 - 3  may be provided to baseband circuit  46  ( FIG. 2 ). Output signals from baseband circuit  46  may be provided to paths  48 - 1 ,  48 - 2 , and  48 - 3 . Respective transmitters  50 - 1 ,  50 - 2 , and  50 - 3  may transmit output signals in different corresponding bands. During signal transmission, filter circuitry  58  may serve as a multiplexing circuit that combines the signals from each of the different bands and routes the resulting multi-band signal to antenna  40  for over-the-air transmission. The transceiver circuitry of transmitters  50 - 1 ,  50 - 2 , and  50 - 3  and receivers  52 - 1 ,  52 - 2 , and  52 - 3  may be implemented on one or more integrated circuits. 
     When receiving signals, low noise amplifiers  56 - 1 ,  56 - 2 , and  56 - 3  may be used to increase signal strength. Each low noise amplifier and each associated receiver in transceiver circuitry  38  of  FIG. 4  may handle signals in a different respective communications band. For example, signals in band B 13  RX may be amplified and provided to receiver  52 - 1  using low noise amplifier  56 - 1 , signals in band BC 0  RX may be amplified and provided to receiver  52 - 2  using low noise amplifier  56 - 2 , and signals in band BC 1  RX may be amplified and provided to receiver  52 - 3  via low noise amplifier  56 - 3 . 
     Transmitted signals may likewise be handled by different components in each respective output path. For example, transmitted signals in band B 13  TX may be handled by transmitter  50 - 1  and corresponding power amplifier  54 - 1 , transmitted signals in band BC 0  TX may be handled by transmitter  50 - 2  and power amplifier  54 - 2 , and transmitted signals in band BC 1  TX may be handled by transmitter  50 - 3  and power amplifier  54 - 3 . 
     Filter circuitry  58  may include components such as bandpass filters, low-pass filters, high-pass filters, diplexers, duplexers, circulators, etc. These components may include two ports (e.g., for bandpass filters), three ports (e.g., for diplexers, duplexers, circulators, and other such components), etc. 
     In configurations of the type shown in  FIG. 4 , diplexer filter  74  may be used to divide incoming signals on path  60  into paths  68  and  76  based on frequency. Received signals on path  60  may potentially include signals in bands BC 1 , BC 0 , and B 13 . Signals in bands BC 1  and BC 0  may, for example, correspond to voice telephone call signals, whereas signals in band B 13  may correspond to data signals (as an example). After passing through diplexer  74  signals in band BC 1  may be routed to path  76 , whereas signals in bands BC 0  and B 13  may be routed to path  68 . During transmission operations, signals in bands BC 0  and B 13  that are passed to diplexer  74  by path  68  are routed to path  60  and antenna  40  by diplexer  74  and signals in band BC 1  that are passed to diplexer  74  by path  76  are routed to path  60  and antenna  40  by diplexer  74 . 
     Duplexer  78  may be used to handle the RX and TX sub-bands associated with band BC 1 . Transmitted signals from power amplifier  54 - 3  in band BC 1  TX may be routed by duplexer  78  to path  76 . Received signals in band BC 1  RX that are present on path  76  may be passed by duplexer  78  to low noise amplifier  56 - 3  and receiver  52 - 3 . 
     Circulator  64  (which may be implemented using a ferromagnetic material, as an example) may have three ports. Circulator  64  may route signals that are flowing in direction  80  on path  68  (i.e., incoming signals in both band BC 0  and band B 13 ) to path  72  and duplexer  70 . Duplexer  70  may route the signals in band B 13  Rx from path  72  to low noise amplifier  56 - 1  and receiver  52 - 1  and may route the signals in band BC 0  RX from path  72  to low noise amplifier  56 - 2  and receiver  52 - 2 . 
     Duplexer  62  in circuitry  84  may be used to combine the transmitted signals from transmitters  50 - 1  and  50 - 2  onto path  66 . In particular, duplexer  62  may route signals in band B 13  TX from transmitter  50 - 1  and power amplifier  54 - 1  onto path  66  and may route signals in band BC 0  TX from transmitter  50 - 2  and power amplifier  54 - 2  to path  66 . Due to nonlinearities in duplexer  62 , there is a potential for producing noise on path  66  due to intermodulation distortion when signals in BC 0  TX and B 13  TX are present simultaneously (e.g., when a voice call in band BC 0  is being held at the same time as data is being conveyed using band B 13  TX). 
     Transmitted signals on path  66  (i.e., signals in bands BC 0  TX and B 13  TX and any associated noise signals) that are flowing in direction  82  may be routed to path  68  and diplexer  74  by circulator  64 . During these data transmission operations, the isolation provided by circulator  64  may ensure that minimal signal power will leak into path  72  (i.e., the power of the signal flowing on path  66  will be mostly coupled to path  68 ). The amount of power flowing in direction  82  on path  66  that leaks onto path  72  during signal transmission will typically be reduced by a factor of 5 dB or more, 10 dB or more, or 20 dB or more relative to the power on path  66  and path  68 . 
     Because circulator  64  isolates receivers  52 - 1  and  50 - 2  from noise and other signals on path  66 , the performance requirements for filter components such as duplexer  62  (or other such transmitter multiplexing circuitry) may be relaxed. For example, the filter architecture of  FIG. 4  may allow duplexer  62  to exhibit nonlinearity. This nonlinearity might be reduced by fabricating duplexer  62  from a relatively large ceramic substrate (e.g., a ceramic substrate having a lateral dimension of over 1 cm), but this might result in an undesirably bulky size for device  10 . When circulator  64  is present, noise from path  66  is prevented from reaching receivers  52 - 1  and  52 - 2 , so duplexer  62  may be implemented using a less bulky ceramic diplexer arrangement than might otherwise be possible or may be implemented using a bulk acoustic wave design or other design that has the potential for producing more noise than would be tolerable without circulator  64 . 
     If desired, circuitry  84  of  FIG. 4  may be implemented using other components. For example, circuitry  84  may be implemented using bandpass filters and a combiner circuit as shown in  FIG. 5  or using bandpass filters and a and a diplexer as shown in  FIG. 6  (as examples). 
     As shown in  FIG. 5 , circuitry  84  may include a first bandpass filter such as bandpass filter  86 - 1  and a second bandpass filter such as bandpass filter  86 - 2 . Bandpass filter  86 - 1  may have a pass band that coincides with the signals being transmitted by transmitter  50 - 1  (i.e., the pass band of bandpass filter  86 - 1  may be centered on frequencies in the range of 777 to 787 MHz to coincide with band B 13  TX in the example of  FIG. 5 ). Bandpass filter  86 - 2  may have a pass band that coincides with the frequencies being transmitted by transmitter  50 - 2  (i.e., frequencies in the range of 824 to 849 MHz to coincide with band BC 0  TX in the example of  FIG. 5 ). Noise signals that fall outside of the pass bands of filters  86 - 1  and  86 - 2  will tend to be blocked by filters  86 - 1  and  86 - 2 . 
     With a circuit configuration of the type shown in  FIG. 1 , signals in band B 13  TX and signals from band BC 0  TX are merged onto path  66  and are provided to circulator  64  ( FIG. 4 ) for transmission over antenna  40 . Path  94 - 1  may be used to route the output signals from bandpass filter  86 - 1  to a first input of combiner  88 . Path  94 - 2  may be used to route the output signals from bandpass filter  86 - 2  to a second input of combiner  88 . Combiner  88  may be formed from passive elements. For example, combiner  88  may be implemented using a Wilkinson splitter having a resistor such as resistor  92  that bridges paths  94 - 1  and  94 - 2  and transmission lines  90 - 1  and  90 - 2  that respectively route signals from paths  94 - 1  and  94 - 2  to path  66 . Resistor  92  may have an impedance of 100 ohms and transmission lines  90 - 1  and  90 - 2  may each have an impedance of 50 ohms (as an example). Combiner  88  may exhibit a minimum loss of about 3 dB for signals in path  94 - 1  and for signals in path  94 - 1 , but because combiner  88  may be implemented using passive elements, combiner  88  may exhibit minimal nonlinearity and therefore minimal noise due to nonlinearity. 
       FIG. 6  shows an illustrative configuration that may be used for circuitry  84  of  FIG. 4  in which signals on paths  94 - 1  and  94 - 2  are merged onto path  66  by a filter such as diplexer  88 . Transmitter  50 - 1  may receive signals on path  48 - 1  and may pass corresponding output signals to power amplifier  54 - 1 . Transmitter  50 - 2  may receive signals on path  48 - 2  and may pass corresponding output signals to power amplifier  54 - 2 . The signals at the output of amplifier  54 - 1  may be associated with band B 13  TX and the signals at the output of amplifier  54 - 2  may be associated with band BC 0  TX (in the  FIG. 6  example), so bandpass filter  86 - 1  may be configured to have a pass band centered around band B 13  TX and bandpass filter  86 - 2  may be configured to have a pass band centered around band BC 0  TX. 
     Diplexer  88  may receive the signals in band B 13  TX on path  94 - 1  and may receive the signals in band BC 0  TX on path  94 - 2  and may combine these signals onto output path  66 . The signals on path  66  may be provided to circulator  64  ( FIG. 4 ) for transmission over antenna  40 . Diplexer  88  may be implemented using any suitable filter technology (e.g., as a bulk acoustic wave device, as a surface acoustic wave device, as a device based on a ceramic substrate, etc.). Because circulator  64  helps isolate receivers such as receivers  52 - 1  and  52 - 2  from noise on path  66 , diplexer  88  may be implemented using a design that generates some noise due to intermodulation distortion while still permitting transceiver circuitry  38  to function properly during simultaneous voice and data communications. 
     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. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20101109
Publication Date: 20130430
Grant Date: 20130430
Priority Date: 20101109
Inventors: SANGUINETTI LOUIE J.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/525", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/525", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 46019568