PATENT DOCUMENT

Publication Number: US-9497054-B1
Application Number: US-201514829418-A
Country: US
Kind Code: B1

Title: Electronic devices having interconnect radiation mitigation capabilities

Abstract:
Electronic devices may include unshielded connectors that convey radio-frequency signals with external devices. A first electronic device may include transmitter circuitry that transmits radio-frequency signals to phase shifting circuitry. The phase shifting circuitry may pass the radio-frequency signals to a first conductive contact of a connector on the first device, may generate modified signals by applying a phase shift of approximately 180 degrees to the radio-frequency signals, and may provide the modified signals to a second conductive contact on the connector. To mitigate undesirable resonance and radiation at the connector, the connector may concurrently convey the radio-frequency signals and the modified signals to an external device over the first and second contacts while mating contacts on a connector of the external electronic device are in electrical contact with the first and second conductive contacts.

Claims:
What is claimed is: 
     
       1. An electronic device that communicates with an external electronic device, the electronic device comprising:
 a transmitter that transmits radio-frequency data; 
 a connector having first and second conductive contacts; and 
 phase shifting circuitry having a first terminal that receives the radio-frequency data from the transmitter, a second terminal coupled to the first conductive contact, and a third terminal coupled to the second conductive contact, wherein the phase shifting circuitry is configured to pass the radio-frequency data from the first terminal to the external electronic device over the second terminal and the first conductive contact, the phase shifting circuitry is configured to generate modified radio-frequency by applying a phase shift to the radio-frequency data received over the first terminal, and the phase shifting circuitry is configured to convey the modified radio-frequency data to the external electronic device over the third terminal and the second conductive contact while the first and second conductive contacts are in electrical contact with the external electronic device. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the phase shifting circuitry is configured to generate the modified radio-frequency data by applying a phase shift of 180 degrees to the radio-frequency data. 
     
     
       3. The electronic device defined in  claim 1 , wherein the external electronic device has a mating connector that mates with the connector and the connector further comprises a third conductive contact that conveys power signals to the external device when the mating connector is coupled to the connector. 
     
     
       4. The electronic device defined in  claim 1 , wherein the external electronic device has a mating connector that mates with the connector and the connector further comprises a third conductive contact that conveys ground signals to the external device when the mating connector is coupled to the connector. 
     
     
       5. The electronic device defined in  claim 4 , wherein the connector further comprises a fourth conductive contact that conveys power signals to the external electronic device when the mating connector is coupled to the connector. 
     
     
       6. The electronic device defined in  claim 1 , wherein the phase shifting circuitry comprises a circuit selected from the group consisting of: a balun circuit, a directional coupler circuit, an active amplifier circuit, an inverter circuit, and a power divider circuit. 
     
     
       7. The electronic device defined in  claim 1 , further comprising:
 storage and processing circuitry, wherein the storage and processing circuitry is configured to provide control signals to the phase shifting circuitry that instruct the phase shifting circuitry to adjust the phase shift applied to the radio-frequency data when generating the modified radio-frequency data. 
 
     
     
       8. The electronic device defined in  claim 1 , wherein the external electronic device comprises a mating connector having first and second mating connector contacts, the electronic device further comprising:
 a metal housing for the electronic device; and 
 connector alignment structures mounted to the metal housing that align the first conductive contact with the first mating connector contact and that align the second conductive contact with the second mating connector contact. 
 
     
     
       9. The electronic device defined in  claim 1 , further comprising:
 a power source; and 
 a low pass filter circuit coupled between the power source and the first conductive contact. 
 
     
     
       10. The electronic device defined in  claim 9 , further comprising:
 a ground terminal; and 
 an additional low pass filter circuit coupled between the ground terminal and the second conductive contact. 
 
     
     
       11. The electronic device defined in  claim 10 , further comprising:
 a high pass filter circuit coupled between the phase shifting circuitry and the first conductive contact structure. 
 
     
     
       12. A method of operating an electronic device that communicates with an external electronic device, wherein the electronic device comprises conductive contacts, transceiver circuitry, and phase shifting circuitry, the method comprising:
 with the transceiver circuitry, providing radio-frequency data signals to the phase shifting circuitry; 
 with the phase shifting circuitry, generating phase shifted data signals that are out of phase with respect to the radio-frequency data signals; 
 with the phase shifting circuitry, concurrently conveying the radio-frequency data signals and the phase shifted data signals to the conductive contacts; and 
 with the conductive contacts, conductively conveying the radio-frequency data signals and the phase shifted data signals to mating conductive contacts on the external electronic device. 
 
     
     
       13. The method defined in  claim 12 ,
 wherein generating the phase shifted data signals comprises performing a phase shift of between 170 degrees and 190 degrees to the radio-frequency data signals. 
 
     
     
       14. The method defined in  claim 13 , further comprising:
 with control circuitry on the electronic device, identifying an updated phase shift; and 
 with the phase shifting circuitry, generating the phase shifted data signals by applying the identified updated phase shift to the radio-frequency data signals. 
 
     
     
       15. The method defined in  claim 12 , further comprising:
 with the phase shifting circuitry, receiving additional radio-frequency data signals and additional phase shifted data signals from the external electronic device over the conductive contacts; and 
 with the phase shifting circuitry, passing the additional radio-frequency data signals to the transceiver circuitry without performing any phase shift operations on the additional radio-frequency data signals. 
 
     
     
       16. The method defined in  claim 12 , wherein the conductive contacts comprise first and second conductive contacts, wherein the mating conductive contacts on the external electronic device comprise first and second mating contacts, and wherein conveying the radio-frequency data signals and the phase-shifted radio-frequency signals to the conductive contacts comprises:
 passing the radio-frequency data signals to the first mating contact through the first conductive contact without performing any phase shift operations on the radio-frequency data signals; and 
 conveying the phase-shifted radio-frequency data signals to the second mating contact through the second conductive contact. 
 
     
     
       17. The method defined in  claim 16 , wherein generating the phase-shifted radio-frequency signals comprises:
 applying a selected phase shift to the radio-frequency data signals so that the phase shifted radio-frequency data signals at the second conductive contact are between 170 degrees and 190 degrees out of phase with respect to the radio-frequency data signals at the first conductive contact. 
 
     
     
       18. An electronic device comprising:
 a connector having first and second conductive contacts that mate with respective first and second mating contacts on an external electronic device; 
 transmitter circuitry that transmits radio-frequency signals to the first mating contact on the external electronic device via the first conductive contact; 
 radiation mitigation circuitry that receives the radio-frequency signals, applies a first phase shift to the radio-frequency signals to generate modified radio-frequency signals, and transmits the modified radio-frequency signals to the second mating contact on the external electronic device via the second conductive contact to mitigate radiation of electromagnetic energy at the connector; and 
 control circuitry that provides a control signal to the radiation mitigation circuitry that controls the radiation mitigation circuitry to apply a second phase shift that is different from the first phase shift to the radio-frequency signals. 
 
     
     
       19. The electronic device defined in  claim 18 , wherein the first phase shift applied to the radio-frequency signals to generate the modified radio-frequency signals is between 170 and 190 degrees. 
     
     
       20. The electronic device defined in  claim 18 , wherein the radio-frequency signals are transmitted over the first conductive contact while the modified radio-frequency data is concurrently transmitted over the second conductive contact, and the radio-frequency signals at the first conductive contact are between 170 and 190 degrees out of phase with respect to the modified radio-frequency signals at the second conductive contact.

Description:
BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to electronic devices with interconnects for communicating with other electronic devices. 
     Electronic devices often include communications circuitry for transmitting radio-frequency signals to external electronic devices over conductive (wired) paths. A typical electronic device might include a radio-frequency connector coupled to the communications circuitry that mounts to a radio-frequency connector on an external electronic device. The radio-frequency signals are conveyed to the external electronic device over the radio-frequency connectors. 
     In some scenarios, the radio-frequency connectors on the electronic device and the external electronic device are linked using a coaxial cable. A coaxial cable includes a signal conductor that conveys the radio-frequency signals and a ground conductor that completely surrounds the signal conductor. The ground conductor serves to convey ground signals between the devices while shielding any electromagnetic energy radiated at the signal conductor. However, interconnect structures having shielding layers can be unnecessarily bulky when the distance between radio-frequency connectors is relatively small and can be detrimental to the aesthetic appearance of the electronic devices. 
     In other scenarios, the space occupied by the radio-frequency interconnect is reduced by forming a ground conductor that conveys ground signals between the devices without shielding the corresponding signal conductor. However, an unshielded signal conductor linking the devices can leak or radiate signal power into the ambient surroundings of the devices, can be susceptible to ambient noise, can induce undesirable electromagnetic radiation on components of the devices, and can render data transmitted over the signal conductor insecure. It would therefore be desirable to be able to provide electronic devices with improved radio-frequency interconnect capabilities. 
     SUMMARY 
     Electronic devices may include unshielded connectors. The connectors may be used for conveying radio-frequency data signals to and from external electronic devices when the external electronic devices are coupled to the connector. The electronic devices may include radiation mitigation circuitry. The radiation mitigation circuitry may use phase shifting circuitry or other circuits for reducing the radiation of electromagnetic energy from the connectors. 
     For example, a first electronic device may include transceiver circuitry and a conductive connector. The conductive connector may include a number of contacts that mate with corresponding mating contacts on a mating connector of an external device. The transceiver circuitry may transmit radio-frequency signals (e.g., radio-frequency data signals) to phase shifting circuitry. The phase shifting circuitry may pass the radio-frequency data signals to a first conductive contact on the connector without adjusting a phase of the radio-frequency data signals. The phase shifting circuitry may generate modified (e.g., phase-shifted) radio-frequency data signals by applying a phase shift of approximately 180 degrees to the radio-frequency data signals. The phase shifting circuitry may provide the modified radio-frequency data signals to a second conductive contact on the connector. The connector may concurrently convey the radio-frequency data signals and the phase-shifted data signals to the mating contacts on the external electronic device over the first and second contacts, respectively. 
     If desired, the connector may include a pair of power and ground contacts. For example, the connector may include a third conductive contact and a fourth conductive contact. The third conductive contact may convey a direct current (DC) power voltage between a power terminal on the electronic device and the external electronic device. The fourth conductive contact may convey a ground voltage between a ground terminal on the electronic device and the external electronic device while the mating contacts of the external electronic device connector are in conductive contact with the connector on the electronic device. In another suitable arrangement, the power supply terminal may be coupled to the first conductive contact via a first low pass filter. The ground terminal may be coupled to the second conductive contact via a second low pass filter circuit (e.g., for filtering out radio-frequency signals while passing direct current ground or power voltages). If desired, the phase shifting circuitry may be coupled to the first and second conductive contacts via respective high pass filter circuits (e.g., for blocking direct current power and ground voltages while passing radio-frequency signals). Additional phase shifting circuitry may be formed on the external electronic device that provides additional radio-frequency data signals and additional phase shifted radio-frequency data signals to the electronic device over the radio-frequency connectors. 
     By concurrently conveying radio-frequency data signals and a phase shifted copy of the radio-frequency data signals over respective first and second contacts on the unshielded connector, undesirable signal leakage and radiation at the unshielded connector may be significantly mitigated (e.g., because the leaking fields generated by the two signals and established between the two devices are canceled out). By forming the connectors without electromagnetic shielding, the space occupied by the connectors may be reduced while improving the aesthetic appearance of the connector structures and of the corresponding system of linked devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of two illustrative electronic devices that are conductively linked using a conductive radio-frequency interconnect and that may include interconnect radiation mitigation circuitry in accordance with an embodiment. 
         FIG. 2  is a diagram of a shielded interconnect that can be used in forming a radio-frequency link between electronic devices in accordance with an embodiment. 
         FIG. 3  is a diagram of an unshielded interconnect that can be used in forming a radio-frequency link between electronic devices in accordance with an embodiment. 
         FIG. 4  is a schematic diagram showing how two electronic devices linked together using an unshielded conductive radio-frequency interconnect may include interconnect radiation mitigation circuitry for mitigating signal leakage at the interconnect in accordance with an embodiment. 
         FIG. 5  is a circuit block diagram showing illustrative circuitry that may generate phase shifted complementary radio-frequency signals for transmission over an unshielded conductive interconnect to mitigate signal leakage at the interconnect in accordance with an embodiment. 
         FIG. 6  is a diagram showing how illustrative radio-frequency connectors on first and second electronic devices may be placed into electrical contact while mitigating signal leakage at an interconnect between devices in accordance with an embodiment. 
         FIG. 7  is a circuit block diagram showing illustrative circuitry that may multiplex power and ground signals onto radio-frequency data lines for reducing the total size of the radio-frequency interconnect required to convey signals between the first and second devices in accordance with an embodiment. 
         FIG. 8  is a diagram showing how illustrative radio-frequency connectors may be placed into electrical contact while multiplexing power and ground signals onto radio-frequency data lines in accordance with an embodiment. 
         FIG. 9  is an illustrative plot showing how radio-frequency data signals may be phase shifted to cancel out the electromagnetic effects of corresponding un-shifted radio-frequency data in accordance with an embodiment. 
         FIG. 10  is an illustrative diagram showing how electric field resonance and undesirable signal leakage may be present at an unshielded radio-frequency interconnect and the chassis of a corresponding external electronic device (e.g., in a volume between two devices) when phase shifted complementary radio-frequency data is not transmitted over the interconnect in accordance with an embodiment. 
         FIG. 11  is an illustrative diagram showing how electric field resonance and undesirable signal leakage may be effectively mitigated at an interconnect when phase shifted complementary radio-frequency data is transmitted over the interconnect in accordance with an embodiment. 
         FIG. 12  is a flow chart of illustrative steps that may be performed by an electronic device of the type shown in  FIGS. 1-11  for transmitting radio-frequency data and corresponding phase shifted data to an external electronic device over an unshielded radio-frequency interconnect in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic components such as electronic devices and other equipment may be interconnected using conductive (wired) paths. As an example, a cable or other conductive interconnect structures may include conductors that convey power signals, ground signals, and data signals between two interconnected electronic devices. Conductive interconnect structures may, for example, convey power between a power adapter and a portable electronic device, may convey data between a first device and a second device such as between a laptop computer and a peripheral device such as a mouse or keyboard, between a laptop computer and a cellular telephone, between two laptop computers, between a laptop computer and a portable hard drive device, etc. The conductive interconnect structures may, for example, include connector structures on a first electronic device and connector structures on a second electronic device that is linked with the first electronic device. The connector structures on each device may include conductive contacts (e.g., contact pads or pins) that are placed into contact to form one or more electrically conductive paths between the electronic devices over which data signals and other signals may be conveyed. 
     An illustrative system in which two electronic devices are interconnected using a conductive path is shown in  FIG. 1 . As shown in  FIG. 1 , a system  10  of interconnected devices may include a first electronic device  12  coupled to a second electronic device  14  via conductive path  16 . Conductive path  16  may include one or more wired interconnect paths between first device  12  and second device  14  over which data signals, power signals, ground signals, and/or any other desired signals are conveyed. For example, first electronic device  12  may generate signals and transmit the signals to second electronic device  14  over conductive path  16  (e.g., over one or more conductive lines in path  16 ). If desired, second electronic device  14  may generate signals and transmit the signals to first electronic device  12  over path  16 . Conductive path  16  may include connector structures on first device  12  and/or second device  14  that are placed into contact to form conductive interconnect path  16 . Conductive path  16  may include any desired number of discrete conductive lines (e.g., wired paths) between device  12  and device  14 . For example, there may be two, three, four, five, six, or more than six separate conductive lines included in conductive interconnect  16 . 
     First electronic device  12  may be any desired electronic device having wireless and/or wired communications capabilities for transmitting and/or receiving data signals with a second, external electronic device such as second electronic device  14 . First electronic device  12  may be, for example, a desktop or portable computer, laptop computer, tablet computer, cellular telephone, portable television, audio receiver, portable media player, power adapter device, portable hard drive device, integrated circuit package device, portable gaming device, or any other desired electronic equipment. First electronic device  12  may be provided in the form of stand-alone equipment (e.g., a handheld device that is carried in the pocket of a user) or may be provided as an embedded system (e.g., a system embedded within a larger system such as an automotive system, a building, or other larger computing device). 
     Second electronic device  14  may be any desired device having communications capabilities that works in conjunction with first electronic device  12  (e.g., that transmits and/or receives data signals over a conductive path with an external electronic device such as first device  12 ). Examples of electronic device  14  include a portable electronic device, a desktop or portable computer, laptop computer, tablet computer, cellular telephone, portable television, audio receiver, portable media player, portable hard drive device, integrated circuit package device, portable gaming device, power adapter device, or any other desired electronic equipment. In one suitable arrangement that is sometimes described herein as an example, second device  14  may be a peripheral electronic device that interfaces with first electronic device  12  such as an input-output device (e.g., a mouse, keyboard, docking structure, camera device, microphone device, fingerprint sensor device, touch pad, display device, alert device, lighting device, sound emitting device, audio device, scanner device, touch screen device, printer device, track pad, scroll wheel, joystick, key pad, gaming pad, sensor device, button-based device, or any other desired input-output device) or any other device that provides data signals to and/or receives data signals from first device  12  for operation in conjunction with the operations of first device  12 . First electronic device  12  may therefore sometimes be referred to herein as primary electronic device  12  or primary device  12  whereas second electronic device  14  is sometimes referred to herein as peripheral electronic device  14 , peripheral device  14 , secondary device  14 , or secondary electronic device  14 . 
     First electronic device  12  may, if desired, include a number of electronic components arranged on one or more substrates such as one or more printed circuit boards or integrated circuits arranged within an electronic device housing  18 . Second electronic device  14  may, if desired, include a number of electronic components arranged on one or more substrates such as one or more printed circuit boards or integrated circuits arranged within an electronic device housing  20 . Housings  18  and  20  may include dielectric housing structures (e.g., plastic or polymer based structures), conductive housing structures (e.g., metal housing structures such as stainless steel, aluminum, etc.), ceramic housing structures, glass housing structures, fiber composite housing structures, other suitable materials, or a combination of two or more of these materials. Housings  18  and  20  may be formed using a unibody configuration in which some or all of housing  18 / 20  is machined or molded as a single structure or can be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Electronic devices interconnected using conductive (wired) interconnect structures such as first and second devices  12  and  14  often convey signals at high frequencies such as radio-frequency signals over conductive interconnect paths  16 . Conveying data at radio-frequencies may allow for the transmitted data to have a greater bandwidth than when the data is transmitted at lower frequencies. For example, first device  12  may transmit radio-frequency signals to peripheral device  14  at a frequency of 5.5 GHz, 2.4 GHz, both 5.5 GHz and 2.4 GHz, or at any other desired radio frequency or combinations of radio-frequencies. Conductive interconnect structures over which radio-frequency signals are conveyed may sometimes be referred to herein as radio-frequency interconnect structures. Transmitting signals at radio-frequencies may cause unshielded signal lines over which the signals are conveyed to be susceptible to leakage of the signals into the ambient environment. 
     In some scenarios, radio-frequency interconnect structures such as structures  16  may include shielded connector structures that block leakage of signals into the ambient environment such as coaxial cable structures or other radio-frequency cabling.  FIG. 2  shows an example of a coaxial cable structure that may be used to form conductive interconnect path  16 . As shown in  FIG. 2 , coaxial cable  22  may be coupled between first device  12  and second device  14  for conveying radio-frequency signals between the devices. First device  12  may include coaxial cable connector structure  24  mounted to housing  18  for interfacing with coaxial cable  22 . Second device  14  may include coaxial cable connector structure  26  mounted to housing  18  for interfacing with cable  22 . Coaxial cable  22  may include an inner signal conductor  28  coupled between signal terminal  32  on coaxial connectors  24  and  26  and an outer ground conductor  30  wrapped completely around signal conductor  28 . Ground conductor  30  may be coupled between ground terminals  34  on coaxial connectors  24  and  26 . Signal conductor  28  may be used to convey radio-frequency data signals between signal terminals  32 . 
     When conveying radio-frequency data signals, signal conductor  28  may leak radio-frequency energy away from signal conductor  28 . As shown in  FIG. 2 , coaxial ground conductor  30  is wrapped completely around signal conductor  28  along its length. Coaxial ground conductor  30  may serve as a radio-frequency shield for radio-frequency signals conveyed on signal line  28  that blocks radio-frequency signals radiated from signal conductor  28  from reaching the surrounding environment (as shown by path  36 ). Similarly, ground shield  30  may prevent ambient radiation (e.g., radio-frequency energy or other ambient noise) from interfering with the signals conveyed on shielded signal line  28 . The schematic example of  FIG. 2  shows that coaxial shield  30  is shorted to connectors  24  and  26  at a single point  34  for the sake of clarity. In practice, coaxial shield  30  is shorted to connectors  24  and  26  for an entirety of the 360 degrees around signal conductor  28 . 
     While coaxial cable  22  allows radio-frequency interconnection  16  to convey radio-frequency signals between devices  12  and  14  without leaking radio-frequency energy onto signal conductor  28  or leaking radio-frequency energy from conductor  28  into the ambient environment, shielded interconnects such as coaxial cable  22  are often difficult to implement in scenarios where the distance between devices  12  and  14  is relatively small (e.g., a few centimeters or fewer). For example, cables such as coaxial cable  22  can limit the minimum distance between devices  12  and  14  required to form conductive interconnect  16  and typically occupy an undesirably large amount of space in system  10 . 
     If desired, wired interconnect  16  may be formed without a shielding layer such as shielding layer  30  of coaxial cable  22  to reduce the space consumed by interconnect  16  and to improve the aesthetic appearance of system  10 . As shown in  FIG. 3 , first device  12  may include radio-frequency connector structure  38  mounted to housing  18  and second device  14  may include radio-frequency connector structure  40  mounted to housing  20 . Conductive signal path  42  may be coupled between RF signal terminals  46  on connectors  38  and  40  and may convey a radio-frequency signal between devices  12  and  14 . Conductive ground path  44  may be coupled between ground terminals  48  on connectors  38  and  40  and may convey ground signals GND (e.g., a DC ground voltage) between devices  12  and  14 . Conductors  42  and  44  may be formed from any desired un-shielded conductive structures such as copper wires or contacts. While unshielded lines  42  and  44  occupy less space and are more aesthetically attractive than coaxial structures  22  of  FIG. 2 , unshielded structures  42  and  44  can leak radio-frequency energy while conveying radio-frequency signals such that radio-frequency energy  50  is emitted or leaked in the space between devices  12  and  14  (i.e., at interconnect  16 ). Leaked radio-frequency energy  50  may give rise to undesirable electromagnetic compatibility concerns in system  10 , such as generation of electromagnetic interference with other electronic components such as antenna structures or other sensitive components on device  12  and/or  14  or interference with other electronic devices external to interconnected system  10 . Such interference can deteriorate wireless performance of first device  12 , second device  14 , and other devices in the vicinity of linked system  10 . In addition, leaked radio-frequency energy  50  may drive one or more metal portions of devices  12  and  14  (e.g., metal portions of housings  18  and  20 ) or nearby metal objects external to system  10  to radiate and receive ambient radio-frequency signals, further deteriorating wireless performance of system  10  and of electronic devices in its vicinity. It may therefore be desirable to be able to provide devices  12  and  14  in system  10  with improved radio-frequency interconnect capabilities that mitigate radiation such as radiation  50  along interconnect  16  without utilizing bulky and aesthetically unattractive interconnect shielding structures. 
     If desired, first electronic device  12  and/or second electronic device  14  may include interconnect resonance mitigation circuitry for mitigating leakage of electromagnetic energy at conductive path  16  without forming electromagnetic shielding structures at path  16 .  FIG. 4  is an illustrative schematic diagram of electronic devices  12  and  14  having interconnect radiation mitigation circuitry. As shown in  FIG. 4 , first electronic device  12  may include control circuitry such as storage and processing circuitry  52  for supporting the operation of device  12 . The storage and processing circuitry 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 circuitry  52  may be used to control the operation of device  12 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  52  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 communications band selection during radio-frequency transmission and reception operations, etc. To support interactions with external equipment, storage and processing circuitry  52  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wired radio-frequency data transfer protocols, universal serial bus (USB) protocols, universal asynchronous receiver/transmitter (UART) 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. 
     First device  12  may include input-output circuitry such as input-output devices  54 . Input-output devices  54  may be used to allow data to be supplied to first device  12  and to allow data to be provided from first device  12  to external devices such as second electronic device  14 . Input-output devices  54  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, displays, touch screens, data ports, etc. A user can control the operation of first device  12  by supplying commands through input-output devices  54  and may receive status information and other output from first device  12  using the output resources of input-output devices  54 . 
     As shown in  FIG. 4 , input-output devices  54  may include radio-frequency transceiver circuitry  56  for communicating with external equipment such as second device  14 . Radio-frequency transceiver circuitry  56  may be formed from one or more integrated circuits, power amplifier circuitry, mixing circuitry, baseband circuitry, receiver circuitry, transmitter circuitry, filtering circuitry, low-noise input amplifiers, passive radio-frequency (RF) components, transmission line structures, and other circuitry for handling radio-frequency wired and/or wireless signals. Radio-frequency transceiver circuitry  56  may generate and convey radio-frequency signals to radio-frequency connector structures  58  and may receive radio-frequency signals from external devices via radio-frequency connector structures  58 . Radio-frequency connector structures  58  may be electrically and/or mechanically coupled to second device  14  via conductive interconnect paths  16 . Radio-frequency connector structures  58  may convey radio-frequency data signals generated at radio-frequency transceiver circuitry  56  to second device  14  via conductive interconnect  16  and may convey radio-frequency signals received over conductive interconnect  16  to radio-frequency transceiver circuitry  46 . Conductive interconnect  16  may be an unshielded interconnect to reduce the overall space occupied by interconnect  16  and connectors  58  and  73 . 
     In order to mitigate radiation or leakage of electromagnetic energy at unshielded interconnect  16 , input-output devices  54  may include interconnect radiation mitigation circuitry  60 . If desired, radiation mitigation circuitry  60  may be interposed between radio-frequency transceiver circuitry  56  and radio-frequency connector  58 . In another suitable arrangement, circuitry  60  may be integrated into transceiver circuitry  56 . Interconnect radiation mitigation circuitry  60  may modify radio-frequency data signals transmitted by radio-frequency transceiver  56  prior to conveying the modified radio-frequency data signals to connector  58  for mitigating radiation of energy on path  16  despite path  16  being provided without an electromagnetic shielding structure. If desired, mitigation circuitry  60  may include one or more phase shifting circuits that apply a phase shift to the radio-frequency data signals received from radio-frequency transceiver circuitry  56 . Mitigation circuitry  60  may, if desired, provide a phase shift to the radio-frequency data signals within the frequency band of the radio-frequency data signals (e.g., without providing any phase shift to the radio-frequency signals at other frequencies). 
     If desired, input-output devices  54  may include optional sensor circuitry  62  and optional antenna circuitry  64 . Sensor circuitry  62  may include capacitive sensor structures, inductive sensor structures, proximity sensor structures, phase and magnitude sensor structures, power sensor structures, or any other desired sensor structures for sensing conditions of the surroundings of first device  12 . Antennas  64  may be used for establishing wireless links to other devices such as second device  14 , a cellular base station, a wireless access point, etc. 
     First electronic device  12  may include power supply circuitry such as power supply circuitry  66 . Power supply circuitry  66  may be used to power input-output devices  54  and processing circuitry  52 . If desired, power supply circuitry  66  may convey power signals to second electronic device  14  via path  16  to power one or more portions of device  14 . 
     Second electronic device  14  coupled to first device  12  may include storage and processing circuitry  68  for controlling operations of second device  14 . Second device  14  may include input-output circuitry  70  having radio-frequency transceiver circuitry  72  coupled to conductive interconnect path  16  via radio-frequency connector structures  73 . If desired, second device  14  may include interconnect radiation mitigation circuitry such as phase shifting circuitry  74  for applying phase shifts to data signals provided to first electronic device  12 . Components on second device  14  may be powered using power supply circuitry  76  and/or using power signals received from first device  12 . If desired, second device  14  may include optional sensors  78  for gathering information about the surroundings of second device  14  and optional antennas  80  for establishing wireless links with other devices such as first device  12 . 
     The example of  FIG. 4  is merely illustrative. If desired, second electronic device  14  may be formed without one or more of control circuitry  68 , power supply circuitry  76 , sensors  78 , and antennas  80 . In scenarios where second electronic device  14  does not transmit radio-frequency signals to first electronic device  12  (e.g., in a unidirectional communications scheme in which only first electronic device  12  conveys radio-frequency signals to second electronic device  14  over conductive interconnect path  16 ), interconnect resonance mitigation circuitry  74  may be omitted from second device  14 . Radio-frequency transceiver circuits  56  and  72  may include one or more radio-frequency transmitters, radio-frequency receivers, or both radio-frequency transmitters and receivers (e.g., transceiver circuitry that both transmits and receives radio-frequency signals). 
       FIG. 5  is an illustrative circuit block diagram showing how first electronic device  12  may interface with second electronic device  14  via unshielded conductive interconnect path  16  while mitigating radiation of radio-frequency energy at path  16 . As shown in  FIG. 5 , first device  12  may be coupled to second device  14  via wired radio-frequency interconnect  16  (e.g., an interconnect formed without any shielding structures). Interconnect  16  may include portions formed on one or both of devices  12  and  14 . For example, interconnect  16  may include radio-frequency connector structures  58  formed on first device  12  placed into electrical contact with radio-frequency connector structures  73  formed on second device  14 . Radio-frequency connector structures  58  and  73  may be electrically coupled together using any desired electrical contacts such as conductive contact pins or contact pads (not shown for the sake of clarity). If desired, additional radio-frequency connector structures such as cabling or additional wiring may be formed between connector structures  58  and  73 . 
     As shown in the example of  FIG. 5 , unshielded radio-frequency interconnect  16  may include four conductive paths (lines) coupled between first device  12  and second device  14 . For example, radio-frequency interconnect  16  may include a first path  110  that conveys powering signals such as a power voltage Vcc between first device  12  and second device  14  (sometimes referred to herein as powering path  110  or power line  110 ). Power path  110  may be coupled between powering terminal  122  on first device  12  and powering terminal  124  on second device  14 . Powering terminal  122  may be coupled to a voltage source such as power supply circuitry  66  of first device  12  whereas powering terminal  124  may be coupled to a voltage source such as power supply circuitry  66  of second device  14  ( FIG. 4 ). If desired, first device  12  may provide powering voltage Vcc to power one or more electronic components on second device  14  and/or second device  14  may provide powering voltage Vcc to power one or more electronic components on first device  12 . Powering voltage Vcc may be a direct current (DC) or an alternating current (AC) supply voltage. 
     Interconnect structures  16  may include a second path  112  and a third path  114  that convey radio-frequency data signals between devices  12  and  14 . A fourth path  116  may be included in interconnect  16  for conveying ground level signals such as ground voltage Vss between devices  12  and  14  (e.g., for electrically coupling ground terminal  118  on device  12  to ground terminal  120  on device  14 ). Ground terminals  118  and  120  may be coupled to any desired ground level voltage source on devices  12  and  14 , to ground terminals on transceivers  52  and  73 , or other structures such as metal portions of housings  18  and  20 . Radio-frequency connector structures  58  and  73  may each include four conductive lines and four corresponding conductive contacts for implementing wired paths  110 ,  112 ,  114 , and  116  of interconnect  16 . 
     First electronic device  12  may include radio-frequency transceiver (TX/RX) circuitry  56  that receives data signals for transmission via input line  126 . For example, transceiver circuitry  56  may receive data for transmission to second device  14  from storage and processing circuitry  52 , baseband processing circuitry, or any other desired communications circuitry via path  126 . Radio-frequency transceiver circuitry  56  may generate radio-frequency data signals D (sometimes referred to herein as radio-frequency data D, data D, or data signals D) based on the data received over input  126  and may output radio-frequency data signals D at signal (positive) terminal  100  for transmission to second device  14 . Transceiver circuitry  56  may include mixing circuitry, data conversion circuitry (e.g., analog-to-digital and/or digital-to-analog convert circuitry), amplifier circuitry, filtering circuitry, or any other desired circuitry for converting baseband data or other data signals received over path  126  into radio-frequency data signals D. Radio-frequency data signals D may be output from signal terminal  100  at a signal phase of X° (e.g., zero degrees, ten degrees, forty-five degrees, or any other desired signal phase). 
     Signal terminal  100  of transceiver  56  may be coupled to a terminal of interconnect radiation mitigation circuitry  60  via path  104 . Mitigation circuitry  60  may have a first terminal coupled to first data path  112  (e.g., to a portion of radio-frequency connector structure  58  used to implement a portion of first data path  112 ), a second terminal coupled to second data path  114  (e.g., to a portion of radio-frequency connector structure  58  used to implement a portion of second data path  114 ), and, if desired, a terminal coupled to ground  118 . If desired, one or more optional AC coupling capacitors  106  may be interposed on transceiver output line  104 . Radiation mitigation circuitry  60  may receive radio-frequency data signals D from signal terminal  100  over path  104 . Radiation mitigation circuitry  60  may pass received radio-frequency data signals D to first data line  112  without altering the phase of data signals D (e.g., data signals D may be output on first data line  112  at the phase X° with which transceiver  56  outputs data signals D). Data signals D may be conveyed to second device  14  over path  112  at phase X°. 
     Radiation mitigation circuitry  60  may include phase shifting circuitry (sometimes referred to as phase shifter circuitry, phase adjustment circuitry, electromagnetic energy leakage mitigation circuitry, or phase adjusting circuitry) that is configured to generate modified radio-frequency data signals D′ by performing a phase shift operation on the radio-frequency data signal D received from transceiver  56  (e.g., on a copy of the radio-frequency data D received from transceiver  56 ) so that modified data signals D′ are approximately 180° out of phase with data signals D (e.g., shifting circuitry  60  may provide an approximately 180° phase shift to data D to generate modified data D′ having a phase of Y°). Radiation mitigation circuitry  60  may output modified radio-frequency data signals D′ on second data line  114 . Modified data signals D′ having phase Y° may be conveyed to second device  14  over path  114  concurrently (e.g., simultaneously) with the transmission of corresponding data signals D having phase X° over path  112  (e.g., the data D′ transmitted over path  114  may be identical to the data D transmitted over path  112  but shifted in phase with respect to data D by approximately 180°). Modified data signals D′ may sometimes be referred to herein as phase shifted signals D′, shifted data D′, phase shifted data D′, or modified data D′, complementary data D′, complementary signals D′, or phase shifted data signals D′. 
     Phase shifting circuitry  60  may provide a predetermined phase shift to data signals D when generating modified data signals D′ such that the difference between phases Y° and X° at the location of interconnect  16  is approximately 180° (e.g., phase shifter circuitry  60  may generate modified signals D′ having a selected phase such that the absolute value of X−Y is between 170 and 190 degrees, between 175 and 185 degrees, exactly 180 degrees, between 179 and 181 degrees, or any other value that is approximately equal to 180 degrees). For example, when data signals D are received from transceiver  56  at phase X=0° phase shifting circuitry  60  may apply a phase shift of 180° to data signals D to generate modified (phase-shifted) data signals D′ having phase Y=180°, when data signals D are received at phase X=60° phase shifting circuitry  60  may apply a phase shift of 180° to generate modified data signals D′ having phase Y=240°, when data signals D are received at phase X=−180° phase shifting circuitry  60  may apply a phase shift of 180° to generate modified data signals D′ having phase Y=0°, etc. 
     In this way, modified data signals D′ are provided on unshielded conductive path  114  approximately 180° out of phase with the corresponding data signals D provided on unshielded conductive path  112 . Because modified data signals D′ are identical to but out of phase with data signals D, the modified data signals D′ may interact with the electric field in the vicinity of interconnect  16  in a manner that is approximately equal and opposite to the interaction of data signals D with the electric field in the vicinity of interconnect  16 . In other words, phase shifting circuitry  60  on first device  12  may intentionally introduce noise (e.g., a disruptive signal) in the form of modified data D′ over unshielded interface  16  that is capable of disrupting or balancing out the electric field resonating modes established by the leaked power of data signals D at interface  16 . In this way, the electromagnetic field effects of radio-frequency data signals D on unshielded interconnect  16  may be canceled out by the electrical effects of modified radio-frequency data signals D′ such that any resonance or radiation at unshielded interconnect  16  is substantially eliminated, thereby preventing undesirable electromagnetic compatibility and interference effects due to the lack of radio-frequency shielding on interconnect  16 . 
     In one suitable arrangement, interconnect radiation mitigation circuitry  60  may be configured to provide signals with the same phase shift of approximately 180° for all data signals transmitted by transceiver circuitry  56  (e.g., circuitry  60  may be hard-coded or hardwired to provide the same phase shift). In practice, the arrangement of connectors  58  and  73 , local environment factors, or other perturbations generated by second device  14  may slightly perturb the difference between phases X° and Y° at the location of interconnect  16  such that it may be desirable to be able to adjust the phase shift provided by circuitry  60 . If desired, interconnect radiation mitigation circuitry  60  may be dynamically adjusted to provide one of a number of different possible phase shifts during normal operation of system  10 . For example, radiation mitigation circuitry  60  may receive control signals CTR 1  over input path  108  (e.g., from storage and processing circuitry  52  or other control circuitry) that control phase shifting circuitry  60  to provide a selected one of many possible different phase shifts to data signals D. In this way, the phase shift provided by circuitry  60  may be dynamically adjusted in real time to ensure that phase X° is approximately 180° out of phase with phase Y° at the location of interconnect  16 , even if the difference of phase X° and phase Y° at interconnect  16  is perturbed over time. If desired, control signals CTR 1  may be provided based on data obtained by sensors  62  on first device  12  and/or sensors  78  on second device  14  ( FIG. 4 ) that identifies when an adjustment to the phase shift provided by circuitry  60  is needed. 
     Interconnect radiation mitigation circuitry  60  may include any desired circuitry for generating phase-shifted data signals D′ that are conveyed over path  114  in conjunction with data signals D on path  112 . For example, interconnect resonance mitigation circuitry  60  may include balun circuitry, directional coupler circuitry, power divider circuitry in conjunction with a phase shifter, active circuitry such as an amplifier or inverter, combinations of these circuits, or any other desired phase shifting circuitry. Radiation mitigation circuitry  60  may be formed on a common substrate, integrated circuit, or printed circuit board as radio-frequency transceiver circuitry  56 , may be integrated within radio-frequency transceiver circuitry  56 , or may be formed on a discrete (dedicated) substrate, integrated circuit, or printed circuit board. 
     Second electronic device  14  may include interconnect radiation mitigation circuitry  74  having a first terminal coupled to first data path  112 , a second terminal coupled to second data path  114 , a third terminal coupled to signal (positive) terminal  130  of radio-frequency transceiver  72  via path  132 , and, if desired, a terminal coupled to ground  120 . If desired, optional AC coupling capacitor  134  may be interposed on path  132 . Radiation mitigation circuitry  74  may receive data signals D having phase X° from first device  12  over path  112  and may receive phase-shifted data signals D′ having phase Y° from first device  12  over path  114 . Radiation mitigation circuitry  74  may pass data signals D to path  132  without modifying the phase of data signals D so that data signals D having phase X° are received at transceiver circuitry  72  (e.g., so that the original data signals as transmitted by transceiver  56  on first device  12  are received at transceiver circuitry  72  on second device  14 ). Radio-frequency transceiver circuitry  72  may down-convert the received radio-frequency data to extract the data that was received by transceiver  56  on first device  12  over path  126  and may pass the extracted data to storage and processing circuitry  68 , baseband circuitry, or any other desired circuitry on second device  14  via path  136  for further processing. Mitigation circuitry  74  may short phase-adjusted data signals D′ to ground, may pass phase-adjusted data signals D′ to other circuitry on device  14 , or may otherwise discard the phase adjusted data signals. 
     Similar to radio-frequency transceiver circuitry  56  on first device  12 , radio-frequency transceiver circuitry  72  on second device  14  may receive data signals for transmission over input line  136 . For example, transceiver circuitry  72  may receive data for transmission to first device  12  from storage and processing circuitry  68 , baseband processing circuitry, or any other desired communications circuitry via path  136 . Radio-frequency transceiver circuitry  72  may generate radio-frequency data signals D based on the data received over input  136  and may output radio-frequency data signals D at signal terminal  130  for transmission to first device  12 . Transceiver circuitry  72  may include mixing circuitry, data conversion circuitry, amplifier circuitry, filtering circuitry, or any other desired circuitry for converting baseband data or other data signals received over path  136  into radio-frequency data signals D. Radio-frequency data signals D may be output from signal terminal  130  at signal phase X° and conveyed to interconnect resonance mitigation circuitry  74  via path  132 . Radiation mitigation circuitry  74  may receive the radio-frequency data signals D from signal terminal  130  over path  132 . Radiation mitigation circuitry  74  may pass received radio-frequency data signals D to first data line  112  without altering the phase of data signals D (e.g., data signals D may be output on first data line  112  at the phase X° with which transceiver  72  outputs data signals D). Data signals D may be conveyed to first device  12  over path  112  at phase X°. 
     Radiation mitigation circuitry  74  may include phase shifting circuitry that is configured to generate modified radio-frequency data signals D′ by performing a phase shift operation on the radio-frequency data signal D received from transceiver  72 . For example, phase shifting circuitry  74  may shift the phase of data signals D to generate modified data D′ that is approximately 180° out of phase with data D (e.g., shifting circuitry  74  may provide an approximately 180° phase shift to data D to generate modified data D′ having a phase of Y°). Radiation mitigation circuitry  74  may output modified radio-frequency data signals D′ on second data line  114 . Modified data signals D′ having phase Y° may be conveyed to first device  12  over path  114  concurrently (e.g., simultaneously) with the transmission of corresponding data signals D having phase X°. 
     Phase shifting circuitry  74  may provide a predetermined phase shift to data signals D when generating modified data signals D′ such that the difference between phases Y° and X° at interconnect  16  is approximately 180° (e.g., phase shifter circuitry  60  may generate modified signals D′ having a selected phase such that the absolute value of X−Y is between 170 and 190 degrees, between 175 and 185 degrees, exactly 180 degrees, between 179 and 181 degrees, or any other value that is approximately equal to 180 degrees). In this way, modified data signals D′ are provided on unshielded conductive path  114  approximately 180° out of phase with data signals D provided on unshielded conductive path  112 . Because modified data signals D′ are out of phase with data signals D, the modified data signals D′ may interact with the electric field in the vicinity of interconnect  16  in a manner that is approximately equal and opposite to the interaction of data signals D with the electric field in the vicinity of interconnect  16 . 
     In one suitable arrangement, interconnect radiation mitigation circuitry  74  may be configured to provide signals with the same phase shift of approximately 180° for all data signals transmitted by transceiver circuitry  72  (e.g., circuitry  74  may be hard-coded or hardwired to provide the same phase shift). In practice, the arrangement of connectors  58  and  73 , local environment factors, or other perturbations generated by first device  12  may slightly perturb the difference between phases X° and Y° such that it may be desirable to be able to adjust the phase shift provided by circuitry  74 . If desired, interconnect radiation mitigation circuitry  74  may be dynamically adjusted to provide one of a number of different phase shifts during normal operation of system  10 . For example, radiation mitigation circuitry  74  may receive control signals CTR 2  over input path  140  (e.g., from storage and processing circuitry  68  or other control circuitry) that control phase shifting circuitry  74  to provide a selected one of many possible phase shifts to data signals D. In this way, the phase shift provided by circuitry  74  may be dynamically adjusted in real time to ensure that phase X° is approximately 180° out of phase with phase Y° at the location of interconnect  16 , even if the difference of phase X° and phase Y° at interconnect  16  is perturbed over time. If desired, control signals CTR 2  may be provided based on data obtained by sensors  62  on first device  12  and/or sensors  78  on second device  14  ( FIG. 4 ) that identifies when an adjustment to the phase shift provided by circuitry  74  is needed. 
     Interconnect radiation mitigation circuitry  74  may include any desired circuitry for generating phase-shifted data signals D′ for conveying on path  114  in conjunction with conveying data signals D on path  112 . For example, interconnect resonance mitigation circuitry  74  may include balun circuitry, directional coupler circuitry, power divider circuitry in conjunction with a phase shifter, active circuitry such as an inverter, combinations of these circuits, or any other desired phase shifting circuitry. Radiation mitigation circuitry  74  may be formed on a common substrate, integrated circuit, or printed circuit board as radio-frequency transceiver circuitry  72 , may be integrated within radio-frequency transceiver circuitry  72 , or may be formed on a discrete (dedicated) substrate, integrated circuit, or printed circuit board. Interconnect radiation mitigation circuitry  60  and  74  may sometimes be referred to herein as phase shifting circuitry, phase shift circuitry, phase shifter circuitry, phase adjustment circuitry, interconnect resonance mitigation circuitry, radiation mitigation circuitry, resonance mitigation circuitry, leakage mitigation circuitry, dynamic phase adjustment circuitry (e.g., in scenarios where the phase shift provided by circuitry  60 / 74  is adjustable), or dynamic phase shifting circuitry. 
     Radiation mitigation circuitry  60  on first device  12  may receive data signals D having phase X° from second device  14  over path  112  and may receive phase-shifted data signals D′ having phase Y° from second device  14  over path  114 . Radiation mitigation circuitry  74  may pass data signals D to path  104  without modifying the phase of data signals D so that data signals D having phase X° are received at transceiver circuitry  56  (e.g., so that the original data signals as transmitted by transceiver  72  on second device  14  are received at transceiver circuitry  56  on first device  12 ). Radio-frequency transceiver circuitry  56  may down-convert the received radio-frequency data to extract the data that was received by transceiver  72  on second device  14  over path  136  and may pass the extracted data to storage and processing circuitry  52 , baseband circuitry, or any other desired circuitry on first device  12  via path  126 . Mitigation circuitry  60  may short phase-adjusted data signals D′ to ground, may pass phase-adjusted data signals D′ to other circuitry on device  12 , or may otherwise discard the phase adjusted data signals. 
     In the example of  FIG. 5 , interconnect  16  is a bi-directional conductive link between devices  12  and  14  such that radio-frequency data may be conveyed from device  12  to device  14  and from device  14  to device  12 . This example is merely illustrative. If desired, interconnect  16  may be a unidirectional interconnect in which data is only ever conveyed from one of devices  12  and  14  to the other. In scenarios where interconnect  16  is a unidirectional interconnect, one of phase shifting circuits  60  and  74  may be omitted (e.g., in systems  10  where radio-frequency data is only ever conveyed from first device  12  to second device  14  and not from second device  14  to first device  12 , second device  14  may be formed without phase shifting circuit  74 , whereas in systems  10  where radio-frequency data is only ever conveyed from second device  14  to first device  12  and not from first device  12  to second device  14 , first device  12  may be formed without phase shifting circuit  60 ). The example of  FIG. 5  is merely illustrative. In general, circuitry  56  and  60  on first device  12  may be connected in any desired manner and circuitry  74  and  72  on second device  14  may be connected in any desired manner (e.g., intervening electronic components may be formed between these circuits, ground path  116  may pass through circuitry  60  and  74 , ground path  116  may be coupled between ground terminals on transceivers  56  and  72 , etc.). 
       FIG. 6  is an illustrative diagram showing how first connector structures  58  on first device  12  may interface with second connector structures  73  on second device  14  to form conductive interconnect path  16 . As shown in  FIG. 6 , connector structures  58  on first device  12  may be mounted to housing  18  of first device  12 , whereas connector structures  73  on second device  14  may be mounted to housing  20  of second device  14 . Connector structures  58  may serve as an electrical (conductive) interface between conductive lines internal to housing  18  and conductive structures external housing  18  whereas connector structures  73  may serve as a conductive interface between conductive lines internal to housing  20  and conductive structures external to housing  20 . Connector structures  58  may be mounted to connector structures  73  (e.g., second device  14  may be mounted or otherwise placed into contact with first device  12  such that connector structures  58  are in conductive contact with connector structures  73 ) to establish conductive contact between first electronic device  12  and second electronic device  14  for conveying radio-frequency signals between the devices. In one suitable arrangement, connector structures  58  are removably mounted to connector structures  73  (e.g., so that second device  14  may be easily detached from first device  12  after radio-frequency data has been conveyed between the devices). 
     In the example of  FIG. 6 , connector structures  58  include four contact pads  150  that form a portion of the conductive paths of radio-frequency interconnect  16  (e.g., a first contact pad  150 - 1 , a second contact pad  150 - 2 , a third contact pad  150 - 3 , and a fourth contact pad  150 - 4 ). Contact pads  150  may be coupled to electrical components within device  12  via corresponding conductive traces. For example, contact pad  150 - 1  may be coupled to power supply terminal  122  via conductive powering trace  154 , contact pad  150 - 2  may be coupled to phase shifting circuitry  60  via conductive data trace  156 , contact pad  150 - 3  may be coupled to shifting circuitry  60  via conductive data trace  158 , and contact pad  150 - 4  may be coupled to ground terminal  118  via conductive grounding trace  160 . Conductive traces  154 ,  156 ,  158 , and  160  may be formed on different substrates or on one or more common substrates (e.g., on one or more printed circuit boards or other dielectric substrates within device  12 ). In another suitable arrangement, one or more of traces  154 ,  156 ,  158 , and  160  may be formed from conductive wires, conductive connector structures, conductive vias structures, pogo pins, spring pins, solder structures, transmission line structures, or any other desired conductive structures within or on first device  12  for electrically coupling contact pads  150  to phase shifting circuitry  60  and terminals  122  and  118 . Contact pads  150  may include any desired electrical contact structures such as conductive pin structures, flat conductive pad structures, conductive structures having a shape that mates with corresponding pads  152  on second device  14 , or any other desired conductive structures. For example, contact pads  150  may protrude from housing  18  so that contact pads  150  are easily biased against corresponding contacts on second device  14  or so that contact pads  150  are inserted within a recessed portion of an external device such as a recess in housing  20  of second device  14 . As another example, contact pads  150  may be formed within a recessed portion of housing  18  that receives corresponding protruding portions associated with connector  73  on second device  14 . In scenarios where housing  18  is formed from metal, contact pads  150  may be insulated from the metal housing (e.g., by dielectric such as a dielectric support structure or dielectric coating). 
     Similarly, connector structures  73  on second device  14  may include four contact pads  152  that form a portion of the conductive paths of interconnect  16  (e.g., a first contact pad  152 - 1 , a second contact pad  152 - 2 , a third contact pad  152 - 3 , and a fourth contact pad  152 - 4 ). Contact pads  152  may be coupled to electrical components within device  14  via corresponding conductive traces. For example, contact pad  152 - 1  may be coupled to power supply terminal  144  via conductive powering trace  162 , contact pad  152 - 2  may be coupled to phase shifting circuitry  74  via conductive data trace  164 , contact pad  150 - 3  may be coupled to shifting circuitry  74  via conductive data trace  166 , and contact pad  150 - 4  may be coupled to ground terminal  120  via conductive grounding trace  168 . Conductive traces  162 ,  164 ,  166 , and  168  may be formed on different substrates or on one or more common substrates (e.g., on one or more printed circuit boards or other dielectric substrates within device  14 ). In another suitable arrangement, one or more of traces  162 ,  164 ,  166 , and  168  may be formed from conductive wires, conductive connector structures, conductive via structures, pogo pins, spring pins, solder structures, transmission line structures, or any other desired conductive structures within device  12  for electrically coupling contact pads  152  to phase shifting circuitry  74  and terminals  144  and  120 . Contact pads  152  may include any desired electrical contact structures such as conductive pin structures, flat conductive pad structures, conductive structures having a shape that mates with corresponding pads  150  on first device  12 , or any other desired conductive structures. For example, contact pads  152  may protrude from housing  20  so that contact pads  150  are easily biased against corresponding contacts  150  on first device  12  or so that contact pads  152  are inserted within a recessed portion of an external device such as a recess in housing  18  of first device  12 . As another example, contact pads  152  may be formed within a recessed portion of housing  20  that receives corresponding protruding portions associated with connector  58  on first device  12 . 
     The conductive traces on first device  12 , the conductive traces on second device  14 , first contact structures  150 , and second contact structures  152  may collectively form the conductive paths of radio-frequency interconnect  16 . For example, conductive trace  154 , conductive trace  162 , contact  150 - 1 , and contact  152 - 1  may collectively form conductive powering path  110  (e.g., as shown in  FIG. 5 ), conductive trace  156 , conductive trace  164 , contact  150 - 2 , and contact  152 - 2  may collectively form conductive data path  112 , conductive trace  158 , conductive trace  166 , contact  150 - 3 , and contact  152 - 3  may collectively form conductive phase shifted data path  114 , and conductive trace  160 , conductive trace  168 , contact  150 - 4 , and contact  152 - 4  may collectively form conductive ground path  116  (e.g., power voltage Vcc may be conveyed between power terminals  122  and  144  on devices  12  and  14  via traces  154  and  162  and contact pads  150 - 1  and  152 - 1 , data signals D may be conveyed between phase shifting circuitry  60  and phase shifting circuitry  74  via traces  156  and  164  and contact pads  150 - 2  and  152 - 1 , phase shifted data signals D′ may be conveyed between phase shifting circuitry  60  and  74  via traces  158  and  166  and contact pads  150 - 3  and  152 - 3 , and ground signals Vss may be conveyed between terminals  118  and  120  via traces  160  and  168  and contact pads  150 - 4  and  152 - 4 ). 
     If desired, portions of housing  18  may be in contact with portions of housing  20  when device  14  is mounted to device  12  at interconnect  16  or there may be a gap between portions of housing  18  and portions of housing  20 . In general, there may be a distance L between housing  18  and housing  20  when device  14  is mounted to device  12  (e.g., a distance L equal to a few millimeters, 1 centimeter, between 1-10 centimeters, less than 1 centimeter, etc.). In scenarios where phase shifted data signals D′ are not provided over contact pads  150 - 3  and  152 - 3 , radio-frequency data signals D provided over contact pads  150 - 2  and  152 - 2  may leak electromagnetic power outwards and may induce radiation at interconnect  16  that interferes with one or more other components on devices  12  and  14  or separate from devices  12  and  14  (e.g., electromagnetic compatibility issues may arise such as scenarios in which portions of housings  18  and  20  are induced to radiate electromagnetic energy). By providing phase shifted data signals D′ approximately 180° out of phase with radio-frequency data D over contact pads  150 - 3  and  152 - 3 , the electromagnetic field contributions of radio-frequency data D may be effectively canceled out, thereby preventing radiation of energy outwards from the unshielded contact pads. 
     If desired, connector structures  58  on first device  12  may include optional connector alignment structures  170  mounted to housing  18  for aligning contact pads  150  with corresponding contact pads  152  on device  14 . Alignment structures  170  may include, for example, one or more alignment protrusions (e.g., pins or other protrusions of housing  18  for mating with corresponding slot or notch structures in housing  20  of device  14 ), screws, magnets (e.g., for biasing first device  12  towards device second  14  at locations on housing  20  that include ferromagnetic materials or magnets), ferromagnetic structures (e.g., for biasing first device  12  towards second device  14  at locations on housing  20  that include magnets), alignment holes or grooves (e.g., notches, holes, or slots cut into housing  18  for aligning with corresponding protruding structures on second device  14 ), retractable alignment pins, adhesive, hooks (e.g., for hooking onto portions of housing  20 ), device support structures (e.g., for mechanically supporting some or all or of second device  14  or for ensuring that second device  14  is always at a predetermined distance from first device  12  when mounted to first device  12 ), or any other desired structures for ensuring or otherwise facilitating alignment of contact pads  150  with contact pads  152  when mounting first device  12  to second device  14 ). Alignment structures  170  may be formed on one side of contact pads  150 , on two sides of contact pads  150 , or may surround some or all of contact pads  150 . Optional alignment structures  170  may, for example, facilitate alignment of contact pads  150  and  152  for a user who wishes to transfer radio-frequency data between devices  12  and  14  via interconnect  16  (e.g., so that the user need not focus their close attention on the alignment of pads  150  and  152  when mounting second device  14  to first device  12  to establish interconnect  16 ). 
     If desired, connector structures  73  on second device  14  may include optional connector alignment structures  172  mounted to housing  20  for aligning contact pads  152  with corresponding contact pads  150  on device  12 . Alignment structures  172  may include, for example, one or more alignment protrusions (e.g., pins or other protrusions of housing  20  for mating with corresponding slot or notch structures in housing  18  of first device  12 ), screws, magnets (e.g., for biasing second device  14  towards first device  12  at locations on housing  18  that include ferromagnetic materials or magnets), ferromagnetic structures (e.g., for biasing second device  14  towards first device  12  at locations on housing  18  that include magnets), alignment holes or grooves (e.g., notches, holes, or slots cut into housing  20  for aligning with corresponding protruding structures on first device  12 ), retractable alignment pins, adhesive, device support structures (e.g., for mechanically supporting some or all or of first device  12  or for ensuring that first device  12  is always at a predetermined distance from device  14  when mounted to device  14 ), or any other desired structures for ensuring or otherwise facilitating alignment of contact pads  150  with contact pads  152  when mounting device  14  to device  12 ). Alignment structures  172  may be formed on one side of contact pads  152 , on two sides of contact pads  152 , or may surround some or all of contact pads  152 . Optional alignment structures  172  may, for example, facilitate alignment of contact pads  150  and  152  for a user who wishes to transfer radio-frequency data between devices  12  and  14  via interconnect  16 . If desired, one, both, or neither of devices  12  and  14  may include corresponding connector alignment structures. 
     When conveying radio-frequency data between devices  12  and  14 , phase shifting circuitry  60  may provide phase-shifted data signals D′ at a suitable signal phase such that data signals D′ are approximately out of phase with (e.g., approximately 180° out of phase with) data signals D. For example, if data signals D have a phase of zero degrees when provided on path  156 , phase shifting circuitry  60  may provide modified data signals D′ at a phase of 180 degrees. When data signals D reach contact pad  150 - 2  and phase shifted data signals D′ reach contact pad  150 - 3 , data signals D will still have a phase of zero degrees and data signals D′ will still have a phase of 180 degrees. The electromagnetic contributions of modified data signals D′ will thereby cancel out the electromagnetic contributions of data signals D at contact pads  150 / 152 , thereby mitigating any potential radiation at contact pads  150 / 152 . In this example, the path lengths of traces  156  and  158  are the same and any phase shift in the data signals due to the path length between circuitry  60  and contact pads  150  will be uniform for both data signals D and modified data signals D′. In other words, an additional phase shift generated for signals D by the path length of path  156  will be equal to an additional phase shift generated for signals D′ by the path length of path  158  and signals D and D′ will still be out of phase with respect to each other at contact pads  150 . 
     However, in some scenarios, the path lengths of traces  156  and  158  may be different. For example, trace  156  may follow a meandering path when coupling phase shifting circuitry  60  to contact pad  150 - 2  such as that shown by dashed line  174  (e.g., a path having a different path length than trace  158 ). Because path  174  has a different path length than trace  158  between phase shifting circuitry  60  and the corresponding contact pad, the path length associated with trace  158  adds a phase shift to the modified data signals D′ that is different from the phase shift added to data signals D by the path length associated with path  174 . Phase shifting circuitry  60  may therefore provide modified data signals D′ at a desired phase such that modified data signals D′ are approximately 180 degrees out of phase with data signals D at the location of contact pads  150 , even if this means that modified data signals D′ need to be provided at a phase that is not 180 degrees out of phase with data signals D at the output of phase shifting circuitry  60 . 
     For example, the path length of path  174  may add ten degrees of phase shift to data signals D whereas the path length of path  158  may add twenty-five degrees of phase shift to modified data signals D′. If data signals D are passed onto path  174  by phase shifting circuitry  60  at a phase of zero degrees and modified data signals D′ are provided to path  174  by phase shifting circuitry  60  at a phase of 180 degrees, data signals D will be received at contact pad  150 - 2  at a phase of ten degrees whereas modified data signals D′ will be received at contact pad  150 - 3  at a phase of 205 degrees (e.g., 195 degrees out of phase with data signals D). As the modified data signals are no longer approximately 180 degrees out of phase with data signals D in this scenario, radiation may still be undesirably induced at contacts  150 . Phase shift circuitry  60  may thereby output modified data signals D′ at a phase of 165 degrees so that modified data signals D′ are received at contact pad  150 - 2  at a phase of 190 degrees, which is 180 degrees out of phase with the phase of data signals D at contact pad  150 - 1  (e.g., 10 degrees). Any potential radiation at contacts  150  may thereby be mitigated despite the differing path lengths of the conductive traces within device  12 . In general, phase shift circuitry  60  may provide a modified data signals D′ at a desired phase such that modified data signals D′ are approximately 180 degrees out of phase with data signals D at the location of contact pads  150 , regardless of the relative path lengths of conductive lines  156  and  158 . If desired, the path lengths of traces  156  and  158  may be characterized during manufacture of device  12  such that phase shifting circuitry  60  is pre-programmed (e.g., in a manufacturing setting prior to use of device  12  by an end user) to provide modified data signals D′ with a desired phase shift. 
     In scenarios where the path lengths of traces  156  and  158  are different, there may be a difference in signal magnitude between paths  156  and  158  at the location of contacts  150  (e.g., the signal magnitude of data D may be less than the signal magnitude of modified data D′ at contacts  150  when trace  156  follows path  174 ). If desired, magnitude offset compensation circuitry may be interposed on one or both of traces  156  and  158 . The magnitude offset compensation circuitry may compensate for signal magnitude variations between paths  156  and  158 . For example, amplifier circuitry and/or attenuator circuitry may be interposed on traces  156  and  158 . Amplifier circuitry may provide a gain to data signals D or modified data signals D′ to increase the magnitude of those signals when received at contacts  150 . Attenuator circuitry may attenuate data signals D or modified data signals D′ to decrease the magnitude of those signals when received at contacts  150 . The magnitude offset compensation circuitry may suitably reduce or increase the magnitude of one or both of signals D and D′ so that the magnitudes are approximately equal at the location of contacts  150 . 
     In the example of  FIGS. 5 and 6 , connectors  58  and  73  each include four conductive contacts for forming conductive interconnect  16  (e.g., so that each connector handles a respective one of a ground voltage, a power voltage, a radio-frequency data signal, and a phase shifted radio-frequency data signal required between first device  12  and second device  14  without radiating electromagnetic energy at the interconnect). In general, a greater number of conductive contacts can increase the relative size of connector structures  58  and  73  and reduce the aesthetic appeal of devices  12  and  14 . If desired, connectors  58  and  73  may be formed using two conductive contacts instead of four conductive contacts to reduce the relative sizes of connectors  58  and  73  (e.g., thereby freeing up additional space on devices  12  and  14  for forming other components such as a display or additional connector structures and thereby improving the aesthetic appearance of devices  12  and  14  relative to scenarios in which more than two contacts are used). The two conductive contacts may be used to each convey two of the ground voltage, power voltage, radio-frequency data signal, and phase shifted radio-frequency data signal between devices  12  and  14 . 
       FIG. 7  is an illustrative circuit block diagram showing how first electronic device  12  and second electronic device  14  may multiplex power and ground voltages onto the conductive paths used to convey data signal D and modified data signal D′ (e.g., to reduce the number of conductive contacts included in conductive interconnect  16  relative to scenarios where ground and power voltages are provided with respective conductive paths on interconnect  16 ). 
     As shown in  FIG. 7 , power terminal  122  on first device  12  may be coupled to node  204  on data path  112  via conductive path  190  and ground terminal  118  may be coupled to node  206  on phase shifted data path  114  via conductive path  194 . Device  12  may include low pass filtering circuitry  192  interposed on path  190  between power terminal  122  and data path  112  and low pass filtering circuitry  196  interposed on path  194  between ground terminal  118  and phase shifted data path  114 . In the example of  FIG. 7 , filtering circuitry  192  and  196  include inductors interposed on paths  190  and  194  respectively. In general, filtering circuitry  192  and  196  may include any desired low pass filter circuitry that allows low frequency signals to pass while blocking high frequency signals (e.g., filtering circuitry  192  and  196  may include any desired networks of one or more inductors, capacitors, and/or resistors connected in any desired manner). 
     Filtering circuit  192  may pass relatively low frequency signals such as power signal Vcc (e.g., a DC power voltage or other relatively low frequency AC voltage signal) onto path  112  and/or onto terminal  122  (e.g., in scenarios where power signal Vcc is received from second device  14 ) while blocking relatively high frequency signals (e.g., radio-frequency signals) such as radio-frequency data signals D from passing onto powering terminal  122 . Filtering circuit  196  may pass relatively low frequency signals such as ground voltage Vss (e.g., a DC ground signal) onto path  114  and/or onto node  118  while blocking relatively high frequency (e.g., radio-frequency signals) such as modified radio-frequency data signals D′ from passing onto ground terminal  118 . 
     If desired, first device  12  may include high pass filtering circuitry interposed on paths  112  and  114  between phase shifting circuitry  60  and nodes  204  and  202  (e.g., a first filtering circuit  200  may be interposed on data line  112  between phase shifting circuit  60  and node  204  whereas a second filtering circuit  202  may be interposed on phase shifted data line  114  between phase shifting circuit  60  and node  206 ). In the example of  FIG. 7 , filtering circuitry  200  and  202  include capacitors interposed on paths  112  and  114  respectively. In general, filtering circuitry  200  and  202  may include any desired high pass filter circuitry that allows high frequency signals to pass while blocking low frequency signals (e.g., filtering circuits  200  and  202  may include any desired networks of one or more inductors, capacitors, and/or resisters connected in any desired manner). 
     Filtering circuit  200  may pass relatively high frequency signals (e.g., radio-frequency signals) such as radio-frequency data signals D onto path  112  and/or onto phase shifting circuitry  60  while blocking relatively low frequency signals such as power voltage Vcc from passing to phase shifting circuitry  60 . Filtering circuit  202  may pass relatively high frequency signals such as phase shifted radio-frequency data signals D′ onto path  114  and/or onto phase shifting circuitry  60  (e.g., in scenarios where device  12  received data signals D′ from device  14 ) while blocking relatively low frequency signals such as ground level voltage Vss from passing to phase shifting circuitry  60 . Radio-frequency data signals D and power signals such as power voltage Vcc may be conveyed to second device  14  over path  112  whereas phase shifted radio-frequency data signals D′ and ground voltage Vss may be passed to second device  14  over path  114 . In this way, ground voltage Vss and phase shifted data signals D′ may be frequency multiplexed onto path  114  and power voltage Vcc and data signals D may be frequency multiplexed onto path  112  without the need for dedicated lines to convey power voltage Vcc and ground voltage Vss. 
     Power terminal  124  on second device  14  may be coupled to node  210  on data path  112  via conductive path  212  and ground terminal  120  on second device  14  may be coupled to node  216  on phase shifted data path  114  via conductive path  218 . Device  14  may include low pass filtering circuitry  214  interposed on path  212  between power terminal  124  and data path  112  and low pass filtering circuitry  220  interposed on path  218  between ground terminal  120  and phase shifted data path  114 . In the example of  FIG. 7 , filtering circuitry  214  and  220  include inductors interposed on paths  212  and  218  respectively. In general, filtering circuitry  214  and  220  may include any desired low pass filter circuitry that allows low frequency signals to pass while blocking high frequency signals (e.g., filtering circuitry  214  and  220  may include any desired networks of one or more inductors, capacitors, and/or resistors connected in any desired manner). 
     Filtering circuit  214  may pass relatively low frequency signals such as power signal Vcc (e.g., a DC power voltage or other relatively low frequency AC voltage signal) onto path  112  and/or onto terminal  124  (e.g., in scenarios where power signals Vcc are received from first device  12 ) while blocking relatively high frequency signals (e.g., radio-frequency signals) such as radio-frequency data signals D from passing onto powering terminal  124 . Filtering circuit  220  may pass relatively low frequency signals such as ground voltage Vss (e.g., a DC ground signal) onto path  114  and/or onto node  120  while blocking relatively high frequency (e.g., radio-frequency signals) such as modified radio-frequency data signals D′ from passing onto ground terminal  120 . 
     If desired, second device  14  may include high pass filtering circuitry interposed on paths  112  and  114  between phase shifting circuitry  74  and nodes  210  and  216  (e.g., a first filtering circuit  222  may be interposed on data line  112  between phase shifting circuit  74  and node  210  whereas second filtering circuit  224  may be interposed on phase shifted data line  114  between phase shifting circuit  74  and node  216 ). In the example of  FIG. 7 , filtering circuits  222  and  224  include capacitors interposed on paths  112  and  114  respectively. In general, filtering circuitry  222  and  224  may include any desired high pass filter circuitry that allows high frequency signals to pass while blocking low frequency signals (e.g., filtering circuits  222  and  224  may include any desired networks of one or more inductors, capacitors, and/or resisters connected in any desired manner). 
     Filtering circuit  222  may pass relatively high frequency signals (e.g., radio-frequency signals) such as radio-frequency data signals D onto path  112  and/or onto phase shifting circuitry  74  while blocking relatively low frequency signals such as power voltage Vcc from passing to phase shifting circuitry  74 . Filtering circuit  224  may pass relatively high frequency signals such as phase shifted radio-frequency data signals D′ onto path  114  and/or onto phase shifting circuitry  74  while blocking relatively low frequency signals such as ground level voltage Vss from passing to phase shifting circuitry  74 . Radio-frequency data signals D and power signals Vcc may be received from first device  12  over path  112 . Filtering circuitry  214  may filter out radio-frequency data signals D and may pass power voltage Vcc to power terminal  124 . Filtering circuitry  222  may filter out power voltage Vcc and may pass radio-frequency data signals D to phase shifting circuitry  74 . Phase adjusted radio-frequency data signals D′ and ground signals Vss may be received from first device  12  over path  114 . Filtering circuitry  220  may filter out phase shifted data signals D′ and may pass ground voltage Vss to terminal  120 . Filtering circuitry  224  may filter out ground voltage Vss and may pass phase shifted radio-frequency data signals D′ to phase shifting circuitry  74 . In this way, second device  14  may extract the data signals from the ground and power signals received over shared conductive paths from device  12 . Similarly, if desired, radio-frequency data signals D and power voltage Vcc may be conveyed to first device  14  over path  112  whereas phase shifted radio-frequency data signals D′ and ground voltage Vss may be passed to first device  12  over path  114 . 
     The example of  FIG. 7  is merely illustrative and does not serve to limit the scope of the present invention. If desired, power voltage Vcc may be provided to phase shifted data signal line  114  via filtering circuitry  196  and  220  (e.g., terminals  122  and  124  may be coupled to nodes  206  and  216  respectively) whereas ground voltage Vss is provided to data signal line  112  via filtering circuitry  192  and  214  (e.g., terminals  118  and  120  may be coupled to nodes  204  and  210  respectively). In another suitable arrangement, interconnect  16  may include three conductive paths such that one of ground voltage Vss and power voltage Vcc may be frequency multiplexed onto one of paths  112  and  114  while the other of ground voltage Vss and power voltage Vcc are conveyed between devices  12  and  14  over a dedicated conductive line (e.g., one of paths  110  or  116  of  FIG. 5 ). If desired, filtering circuits  200  and  202  may be omitted and coupling capacitor  106  may be used as a high pass filter that filters out low frequency ground and power signals from passing to transceiver circuitry  56  and/or filtering circuits  222  and  224  may be omitted and coupling capacitor  134  may be used as a high pass filter that filters out low frequency ground and power signals from passing to transceiver circuitry  72 . If desired, coupling capacitors  106  and/or  134  may be omitted. In another suitable arrangement, first device  12  may transmit data D to second device  14  at multiple frequencies at once. For example, device  12  may transmit data D to second device  14  at 2.4 GHz and 5.5 GHz. In this scenario, first device  12  may transmit phase shifted data D′ to second device  14  to be 180 degrees out of phase with each frequency of the data signals D conveyed to second device  14  (e.g., device may provide a first signal at 2.4 GHz and a second signal at 5.5 GHz to second device  14  over path  112  at a given time and may concurrently provide a third signal at 2.4 GHz that is 180 out of phase with the first signal on path  114  and a fourth signal at 5.5 GHz that is 180 out of phase with the second signal on path  114 , etc.). 
       FIG. 8  is an illustrative diagram showing how first connector structures  58  on first device  12  may interface with second connector structures  73  on second device  14  to form conductive path  16  when interconnect  16  is formed using only two paths for frequency multiplexing the data signals with ground and power signals. As shown in  FIG. 8 , connector structures  58  may be mounted to connector structures  73  to establish conductive contact between first electronic device  12  and second electronic device  14  for conveying radio-frequency signals between the devices. Connector structures  58  include two contact pads  150  that form a portion of the conductive paths of radio-frequency interconnect  16  (e.g., data contact  150 - 2  and phase shifted data contact  150 - 3 ). Contact pad  150 - 2  may be coupled to node  204  via conductive trace  156 . Node  204  may be coupled to power supply terminal  122  via conductive trace  190 . Contact pad  150 - 3  may be coupled to node  206  via conductive trace  158 . Node  206  may be coupled to ground terminal  118  via conductive trace  194 . Similarly, connector structures  73  include two contact pads  152  that form a portion of the conductive paths of radio-frequency interconnect  16  (e.g., data contact  152 - 2  and phase shifted data contact  152 - 3 ). Contact pad  152 - 2  may be coupled to node  210  via conductive trace  164 . Node  210  may be coupled to power supply terminal  124  via conductive trace  212 . Contact pad  152 - 3  may be coupled to node  216  via conductive trace  166 . Node  216  may be coupled to ground terminal  120  via trace  218 . 
     Conductive traces  190 ,  156 ,  158 , and  194  may be formed on different substrates or on one or more common substrates (e.g., on one or more printed circuit boards or other dielectric substrates within device  12 ). In another suitable arrangement, one or more of traces  190 ,  156 ,  158 , and  194  may be formed from conductive wires, connector structures, conductive vias structures, pogo pins, spring pins, solder structures, transmission line structures, or any other desired conductive structures within device  12  for electrically coupling contact pads  150  to phase shifting circuitry  60  and terminals  122  and  118 . 
     Similarly, connector structures  73  on second device  14  may include two contact pads  152  that form a portion of the conductive paths of interconnect  16  (e.g., a data contact  152 - 2  and a phase-shifted data contact  152 - 3 ). Contact pad  152 - 2  may be coupled to node  210  via trace  164 . Node  210  may be coupled to power supply terminal  124  via conductive trace  162 . Contact pad  152 - 3  may be coupled to node  216  via trace  166 . Node  216  may be coupled to ground terminal  120  via trace  218 . Conductive traces  212 ,  164 ,  166 , and  218  may be formed on different substrates or on one or more common substrates (e.g., on one or more printed circuit boards or other dielectric substrates within device  12 ). In another suitable arrangement, one or more of traces  212 ,  164 ,  166 , and  218  may be formed from conductive wires, connector structures, conductive vias structures, pogo pins, spring pins, solder structures, transmission line structures, or any other desired conductive structures within device  14  for electrically coupling contact pads  152  to phase shifting circuitry  74  and terminals  124  and  120 . Because the ground and power signals are frequency multiplexed onto signal contacts  150 - 2 ,  152 - 2 ,  150 - 3 , and  152 - 3 , connector  16  may be formed using only two conductive paths thereby reducing the total area required to form interconnect  16  relative to a four path interconnect as shown in the example of  FIG. 4 . 
       FIG. 9  is an illustrative signal diagram showing how phase shifting circuitry  60  and/or  74  of devices  12  and  14  may generate phase shifted data signals D′ that are approximately 180 degrees out of phase with a corresponding data signal D. The illustrative signal diagrams of  FIG. 9  plot signal strength as a function of the lateral position between devices  12  and  14  while device  14  is connected to device  12  (e.g., at a position ranging between 0 and L). As shown in  FIG. 9 , curve  300  illustrates the signal strength of radio-frequency data signal D on path  112  between electronic devices  12  and  14 . The signal waveform of data signal  300  may be, for example, a standing wave having a signal peak at location A 1  between devices  12  and  14 . This example is merely illustrative and, in general, radio-frequency signal D may have any desired signal pattern. For example, data signal  300  need not be a standing waveform, as the transceiver circuitry on both devices is likely to be well matched. 
     Curve  302  illustrates the signal strength of phase-shifted radio-frequency data signal D′ when provided with a phase shift of zero degrees relative to the radio-frequency data signal D associated with curve  300 . In other words, signal  302  may be generated by phase shifting circuitry  60  by merely passing a copy of data signal D onto path  114  without changing the phase of signal D′ relative to signal D (e.g., modified signal D′ associated with curve  302  may have peaks or maxima that overlap with the peaks of signal  300  such as a peak at position A 1  that aligns with the peak at position A 1  of data signal  300 ). When signal  300  is provided on line  112  concurrently with providing signal  302  on line  114 , the electric field generated by signals  300  and  302  may constructively interfere, generating a resonance that undesirably radiates (leaks) electromagnetic energy at interconnect  16 . 
     Curve  304  illustrates the signal strength of phase-shifted radio-frequency data signal D′ when provided with a phase shift of 180° relative to data signal D associated with curve  300 . In other words, signal  304  may be generated using phase circuitry  60  by shifting a copy of data signal D by 180° and passing the shifted signal D′ onto path  114  (e.g., so that the minimum of signal  300  at location A 1  is shifted to location A 2  in shifted signal  304  as shown by arrow  306 ). In this way, signal  304  is 180° out of phase with data signal  300  (e.g., signal  304  may have troughs or minima such as the minimum at position A 1  that overlap with the maxima of data signal  300  such as the maximum at position A 1 ). When signal  304  is provided on line  114  concurrently with providing signal  300  on line  112 , the electric field generated by signals  300  and  302  may destructively interfere, mitigating resonance and undesired radiation of electromagnetic energy at interconnect  16 . 
       FIG. 10  is an illustrative diagram showing an example of the electric field generated between devices  12  and  14  while conveying radio-frequency data signals D on conductive path  112  without providing phase shifted data signals D′ that are out of phase with signals D on second conductive path  114 . As shown in  FIG. 10 , first device  12  has data contact pad  150 - 2  and phase shifted data contact pad  150 - 3  on a given surface of device  12  while device  12  is in conductive contact with second device  14  (second device  14  has been omitted from  FIG. 10  for the sake of clarity). Surface  310  illustrates the electric field strength at the surface of device  12  (e.g., at interconnect  16 ) while transmitting data D over contact pad  150 - 2  and without transmitting phase-shifted modified data D′ over contact pad  150 - 3  (or while transmitting modified data D′ substantially in-phase with data D such as shown by curve  302  of  FIG. 9 ). Contour lines  312  of surface  310  exhibit locations of constant electric field magnitude. Surface  310  exhibits a resonance as shown by well-defined field peaks (maxima)  314  and troughs (minima)  316 . The electric field resonance shown by surface  310  may induce portions of device  12  and/or device  14  to radiate electromagnetic energy and/or may generate other undesirable electromagnetic interference effects in system  10 . Similarly, resonance  310  may lead to undesired absorption of electromagnetic energy (e.g., noise) onto signal line  150 - 2  from the ambient surroundings. For example, for a given device size, resonance  310  may lead to radiation that has a strength as high as 72 dBμV/m at 5.5 GHz and at three meters away from system  10  when signals D are provided at a power level of −20 dBm, and/or may collect noise signals having a power level −17 dBm at signal port  150 - 2  (e.g., if 3 V/m of noise is present in the vicinity of system  10 ). The example of  FIG. 10  is merely illustrative and, in general, any electromagnetic current distribution pattern may be induced at the surface of device  12  (e.g., at any given corresponding resonant frequency). If desired, device  12  may include additional ground and power contact pads (e.g., as described in connection with  FIGS. 5 and 6 ). 
       FIG. 11  is an illustrative diagram showing an example of the electric field generated between devices  12  and  14  while conveying data D on conductive path  112  and while providing phase shifted data signals D′ that are out of phase with signals D on second path  114 . As shown in  FIG. 11 , surface  318  illustrates the electric field strength at interconnect  16  while transmitting data D over contact pad  150 - 2  and while providing phase-shifted modified data D′ over contact pad  150 - 3  that is approximately 180° out of phase with data D (e.g., as shown by curve  304  of  FIG. 9 ). Contour lines  312  of surface  310  exhibit locations of constant electric field magnitude. Surface  318  does not exhibit any well-defined maxima or minima (except for perhaps small perturbations in the vicinity of contacts  150 ). Field  318  thereby does not exhibit strong enough resonance to induce portions of devices  12  and  14  to radiate electromagnetic energy or to otherwise interfere with other device components or absorb ambient noise. For example, resonance  318  may lead to radiation that has a strength that is reduced by 41 dB and absorption of noise that is reduced by 41 dB relative to the scenario described in connection with  FIG. 10 . By providing signals D′ at contact  150 - 3  that are approximately 180° out of phase with signals D, device  12  may mitigate resonance and radiation of electromagnetic energy in the vicinity of unshielded interconnect  16 . 
       FIG. 12  is a flow chart of illustrative steps that may be performed by first device  12  to convey radio-frequency data to second electronic device  14  while mitigating electromagnetic radiation in the vicinity of interconnect  16 . The steps of  FIG. 12  may, for example, be performed by first device  12  after second device  14  has been conductively connected to first device  12  (e.g., after second device  14  has been mounted to first device  12  such that contacts  152  on connector  73  are in electrical contact with contacts  150  on connector  58 ). The steps of  FIG. 12  may, for example, be performed by first device  12  after identifying data D for transmission and after providing data D to phase shifting circuitry  60  (e.g., using transceiver circuitry  56 ). 
     At step  320 , first device  12  may identify a phase shift to be added to data signals D to generate modified data signals D′. The phase shift to be provided may, for example, be hardcoded into phase shifting circuitry  60  or may be identified by control signal CTR 1 . The phase shift to be provided may be identified such that the modified data signals D′ are approximately 180° out of phase with data signals D at the location of interconnect  58  (e.g., including any contributions from path length differences between traces  156  and  158 ). 
     At step  322 , phase shifting circuitry  60  may pass the radio-frequency data signals D received from transceiver circuitry  56  to path  156  without modifying the phase of signals D. Phase shifting circuitry  60  may modify a copy of data D by performing the identified phase shift on a copy of data D to generate modified data D′ (e.g., to generate modified data D′ having a phase that is approximately 180° degrees out of phase with data D at the location of connector  58  accounting for any difference in path length of paths  156  and  158 ) and may provide modified data D′ to path  158 . 
     At step  324 , first device  12  may transmit data signals D and modified data signals D′ to second device  14  over contact pads  150 - 2  and  150 - 3 . If desired, first device  12  may concurrently transmit ground signals Vss and power signals Vcc to second device  14  over paths  110  and  116  (e.g., as shown in  FIG. 5 ) or over paths  112  and  114  (e.g., as shown in  FIG. 7 ). 
     In some scenarios, external factors such as factors associated with the operation of second device  14  may perturb the relative phase shift of signals D and D′ at interconnect  16 . In order to ensure that modified signal D′ remains approximately 180° out of phase with signal D, it may be desirable to be able to update the phase shift provided by circuitry  60 . At optional step  326 , device  12  may identify that the phase shift to be provided to the modified data signals D′ needs to be changed. For example, first device  12  may identify that the phase shift needs to be updated based on information obtained at first device  12  (e.g., sensor information obtained by sensors  62  identifying a change in the phase of modified signal D′ relative to signal D at interconnect  16 ), feedback from second device  14  (e.g., sensor information obtained by sensors  78  of second device  14 ), predetermined settings, etc. If first device  12  determines that the phase shift needs to be updated, first device  12  may identify the updated phase shift to apply and processing may loop back to path  322  as shown by  328  to generate modified data signals D′ using the updated phase shift. For example, storage and processing circuitry  52  may control phase shift circuitry  60  to apply the updated phase shift using control signals CTR 1 . 
     If desired, second device  14  may monitor the relative phase of signals D and D′ at interconnect  16  to determine whether modified signal D′ is no longer suitably out of phase with signals D. If it is determined that modified signal D′ is no longer suitably out of phase with signals D, second device  14  may inform first device  12  (e.g., over a wired link or a wireless link) that the phase shift needs to be updated and/or may identify the updated phase shift to apply. If desired, second device  14  and/or first device  12  may monitor interconnect  16  for the presence of electromagnetic radiation generated at interconnect  16  (e.g., indicative of modified signal D′ no longer being out of phase with signal D) and may instruct phase shift circuitry  60  to update the phase shift used to generate modified data signals D′ accordingly. In this way, system  10  may ensure that signals D′ are 180° out of phase with respect to signals D for a wide variety of operating conditions, thereby mitigating electromagnetic energy leakage at interface  16 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20150818
Publication Date: 20161115
Grant Date: 20161115
Priority Date: 20150818
Inventors: LI TIANQI
LAM CHEUNG-WEI
PATHAK VANEET
Assignee: APPLE INC
CPC Classifications: [{"code": "H04L27/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/0475", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B15/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B15/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L25/0264", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0475", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L25/0264", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 57234891