Patent Publication Number: US-9900054-B2

Title: Link emission control

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of co-pending U.S. patent application Ser. No. 13/754,694, entitled “Link Emission Control,” filed Jan. 30, 2013, which claims priority under 35 U.S.C. § 119(e) from U.S. Provisional Patent Application No. 61/592,491, entitled “Link Emission Control System and Method,” filed Jan. 30, 2012, both of which are incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to connectors for electronic devices and more specifically to systems and methods for controlling electromagnetic emissions in connectors connecting the electronic devices. 
     BACKGROUND 
     Advances in semiconductor manufacturing and circuit design technologies have enabled the development and production of integrated circuits (ICs) with increasingly higher operational frequencies. In turn, electronic products and systems incorporating such integrated circuits are able to provide much greater functionality than previous generations of products. This additional functionality has generally included the processing of increasingly larger amounts of data at increasingly higher speeds. 
     Many electronic systems include multiple printed circuit boards (PCBs) upon which these high-speed ICs are mounted, and through which various signals are routed to and from the ICs. In electronic systems with at least two PCBs and the need to communicate information between those PCBs, a variety of connector and backplane architectures have been developed to facilitate information flow between the boards. Such connector and backplane architectures introduce unwanted electromagnetic signal emissions that may interfere with other circuits and devices. When wireless communication links are used, excessive electromagnetic emissions may occur prior to as well as during interconnection between two circuits or devices. 
     BRIEF SUMMARY 
     An embodiment of a method for managing a communication link between a first device and a second device in which the first device may have a first shield portion and the second device may have a second shield portion, may include receiving by the second device a first electromagnetic EHF signal transmitted by the first device. The second device may determine whether the received first electromagnetic EHF signal indicates that the first shield portion of the first device and the second shield portion of the second device are in alignment. In response to a determination that the received first electromagnetic EHF signal indicates that the first shield portion and the second shield portion are in alignment, the second device may enable transmission of a modulated second electromagnetic EHF signal by the second device. 
     An embodiment of a method for managing a communication link between a first device and a second device in which the first device may have a first shield portion and the second device may have a second shield portion, may include receiving by the second device a first electromagnetic EHF signal transmitted by the first device. The second device may determine whether the received first electromagnetic EHF signal indicates that the first shield portion of the first device and the second shield portion of the second device are in alignment. In response to a determination that the received first electromagnetic EHF signal indicates that the first shield portion and the second shield portion are not in alignment, the second device may disable transmission of a modulated second electromagnetic EHF signal by the second device. 
     An embodiment of a method for managing a communication link between a first device and a second device may include receiving by near field coupling to the second device, a first electromagnetic EHF signal transmitted by the first device. The second device may determine whether the received first electromagnetic EHF signal indicates that the first device is an acceptable device for communication with the second device. In response to a determination that the first device is an acceptable device, the second device may enable transmission by near field coupling of a modulated second electromagnetic EHF signal by the second device. 
     An embodiment of a method for managing a communication link may include transmitting by near field coupling from a first device, a first electromagnetic EHF signal that is low-level modulated with a predefined code required by a corresponding second device. The first device may receive by near field coupling to the first device a second electromagnetic EHF signal transmitted by the second device. The first device may determine whether the received second electromagnetic EHF signal is modulated with a high level of modulation. In response to a determination that the received second electromagnetic EHF signal is modulated with a high level of modulation, the first device may enable transmitting the first electromagnetic EHF signal with a high level of modulation. 
     An embodiment of a second device for use in a communication link with a first device, the first device having a first shield portion, may include a first EHF communication unit configured to receive a first electromagnetic EHF signal transmitted by the first device. A second shield portion may provide partial shielding for the EHF communication unit. A first signal controller may be coupled to the first EHF communication unit and be configured to determine whether the received first electromagnetic EHF signal indicates that the first shield portion of the first device and the second shield portion of the second device are in alignment. In response to a determination that the received first electromagnetic EHF signal indicates that the first shield portion and the second shield portion are in alignment, the first signal controller may enable transmission of a modulated second electromagnetic EHF signal by the EHF communication unit. 
     An embodiment of a second device for use in a communication link with a first device, may include a first EHF communication unit configured to receive by near field coupling a first electromagnetic EHF signal transmitted by the first device. A first signal controller may be coupled to the EHF communication unit and may be configured to determine whether the received first electromagnetic EHF signal indicates that the first device is an acceptable device for communication with the second device. In response to a determination that the first device is an acceptable device for communication with the second device, enabling transmission by near field coupling of a modulated second electromagnetic EHF signal by the EHF communication unit. 
     In some examples, a method for establishing a communication link may include transmitting by a first device a first electromagnetic EHF signal low-level modulated with a predefined code required by a corresponding second device, and receiving by the first device a second electromagnetic EHF signal transmitted by the second device. The first device may determine whether the received second electromagnetic EHF signal is modulated with a high level of modulation. If the received electromagnetic EHF signal is modulated with a high level of modulation, transmission of the low-level modulated first electromagnetic EHF signal may be terminated. The first electromagnetic EHF signal may then be transmitted with a high level of modulation. 
     In some examples, a first device for use in a system having first and second devices for establishing a communication link between the first and second devices may include a first EHF communication unit configured to transmit to the second device a first electromagnetic EHF signal low-level modulated with a predefined code required by a corresponding second device. A second EHF communication unit may be configured to receive a second electromagnetic EHF signal transmitted by the second device. A signal controller may be configured to determine whether the received second electromagnetic EHF signal is modulated with a high level of modulation. If the received second electromagnetic EHF signal is modulated with a high level of modulation, transmission of the low-level modulated first electromagnetic EHF signal by the first EHF communication unit may be disabled, and transmission of the first electromagnetic EHF signal with a high level of modulation may be enabled. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Having thus described communication between devices in general terms, reference is now made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  illustrates a various embodiments of a communication system; 
         FIG. 2  is a side view of a first example of an EHF communication unit useable in the system of  FIG. 1 ; 
         FIG. 3  is an isometric view of a second example of an EHF communication unit; 
         FIGS. 4A-4B  depict two graphs of representative emissions spectra associated with an unmodulated signal and a modulated signal; 
         FIGS. 5A-5B  are schematic illustrations showing a first device and a second device configured to reduce electromagnetic emissions; 
         FIG. 6  is a schematic illustration of an exemplary multiplexer circuit that may be used in a signal controller; and 
         FIG. 7  is a flow chart illustrating an example of a method for communicating between the first device and the second device while reducing the production of electromagnetic emissions. 
         FIG. 8  is a flow chart illustrating another example of a method for communicating between the first device and the second device while reducing the production of electromagnetic emissions. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments are now described more fully hereinafter with reference to the accompanying drawings, in which representative examples are shown. Indeed, the disclosed communication system and method may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. 
     In today&#39;s society and ubiquitous computing environment, high-bandwidth modular and portable electronic devices are being used increasingly. Security and stability of communication between and within these devices is important to their operation. In order to provide improved secure high-bandwidth communications, the unique capabilities of wireless communication between electronic devices and between subcircuits within each device may be utilized in innovative and useful arrangements. 
     Such communication may occur between radio frequency communication units, and communication at very close distances may be achieved using EHF frequencies (typically, 30-300 GHz) in an EHF communication unit. An example of an EHF communications unit is an EHF comm-link chip. Throughout this disclosure, the terms comm-link chip, and comm-link chip package are used to refer to EHF antennas embedded in IC packages. Examples of such comm-link chips are described in detail in U.S. Patent Application Publication Nos. 2012/0263244; and 2012/0307932, both of which are hereby incorporated in their entireties for all purposes. Comm-link chips are an example of a communication device, also referred to as communication unit, whether or not they provide wireless communication and whether or not they operate in the EHF frequency band. 
       FIG. 1  illustrates a communication system  100 . As shown, system  100  may include a first device  102  configured to couple to a second device  104 . The first device  102  may be configured to communicate with and/or connect to the second device  104  and vice versa. Further, the first device  102  and the second device  104  can be electronic devices capable of connecting and communicating with each other. The first device  102  may include an electromagnetic shield portion  106 , an EHF communication unit  108 , a signal controller  110 , and an EHF communication unit  112 . Similarly, the second device  104  may include an electromagnetic shield portion  114 , an EHF communication unit  116 , a signal controller  118 , and an EHF communication unit  120 . 
     In this example, the signal controller  118  may be configured to communicate with the EHF communication unit  116  and the EHF communication unit  120  of the second device  104 . Similarly, the signal controller  110  may communicate with the EHF communication unit  108  and the EHF communication unit  112  of the first device  102 . 
     In some embodiments, each of the EHF communication unit  108 , the EHF communication unit  116 , the EHF communication unit  112 , and the EHF communication unit  120  can be or may include an EHF transmitter and an EHF receiver. In such an example, a first or second device may include only one EHF communication unit. Further, the single or combination of two EHF communication units may be formed as a single integrated circuit and may be represented as a single communication unit or as separate communication units. The two EHF communication units  108  and  112  thus may be formed as a single communication circuit  122 . Similarly, EHF communication units  116  and  120  may be formed as a single communication circuit  124 . Though not shown, a person skilled in the art will appreciate that each of the first device  102  and the second device  104  may include any number of EHF communication units. 
     The EHF communication unit  108  may be configured for transmitting an unmodulated first electromagnetic EHF signal. As mentioned, the EHF communication unit  108  may be a receiver, transmitter, or a transceiver. The EHF communication unit  108  may transmit or receive one or more electromagnetic signals to/from the second device  104  or specifically from the EHF communication unit  116  and/or the EHF communication unit  120 , using EHF near-field coupling. The shield portion  106  may surround at least a portion of the EHF communication unit  108 , to provide electromagnetic shielding. Similarly, the shield portion  114  may surround at least a portion of the EHF communication unit  116 . The EHF communication units  108  and  112  may be configured to communicate with the signal controller  110 . Further, the EHF communication unit  112  can be a receiver, transmitter, or a transceiver. The EHF communication unit  112  may be configured to receive or transmit at least one electromagnetic EHF signal from/to other devices present in a predefined range of distance, for example within the near field. For example, the EHF communication unit  112  can receive or transmit one or more signals from/to the second device  104 . 
     In one example, EHF communication unit  108  may be a transmitter configured to transmit an electromagnetic EHF signal, whether modulated or unmodulated, to EHF communication unit  116 , which is configured as a receiver for receiving the electromagnetic EHF signal transmitted by the EHF communication unit  108 . Correspondingly, EHF communication unit  120  may be a transmitter configured to transmit a modulated or unmodulated electromagnetic EHF signal to EHF communication unit  112 , which is configured as a receiver for receiving the electromagnetic EHF signal transmitted by the EHF communication unit  120 . 
     First and second devices may be configured as peers and have corresponding functionality, or they may be configured as host and client with different functionality. In one example, the signal controller  110  may perform one or more checks to authorize communication between the first device  102  and the second device  104 . Further, the signal controller  110  may determine whether the first device  102  is an acceptable device when connected to the second device  104 . The signal controller  110  may analyze the one or more signals received from the second device  104 , such as from the EHF communication units  116  and/or  120 . The signal controller of the second device  104  may analyze and/or process the electromagnetic signals received from the first device  102  or more specifically from the EHF communication unit  108 . 
     The shield portion  106  and the shield portion  114  may be configured to effectively connect to each other, thus acting as a continuous shield portion rather than two separated shield portions, when the first device  102  and the second device  104  are aligned properly and preferably positioned proximate to or in contact with each other. Additionally, the signal controller  118  may further be configured for determining whether the shield portion  106  is in effective electrical contact with the shield portion  114 , sufficiently to form a continuous shield when the first shield portion  106  and the second shield portion  114  are aligned relative to each other and preferably positioned proximate to or in contact with each other. In  FIG. 1  the shield portion  106  is shown spaced apart from and in partial alignment with shield portion  114 . 
     The first signal controller  118  may be configured for determining whether the electromagnetic EHF signal received by the second EHF communication unit indicates that the shield portion  106  and the shield portion  114  are in alignment. Further, the signal controller  118  may be configured to produce one or more modulation signals. In an embodiment, the signal controller  118  may generate a modulated electromagnetic EHF signal when the received electromagnetic EHF signal indicates that the shield portion  106  and the shield portion  114  are in alignment. In another embodiment, the signal controller  118  may disable transmission of the modulated second electromagnetic EHF signal when the received electromagnetic EHF signal indicates that the shield portion  106  and the shield portion  114  are not in alignment. 
     The second EHF communication unit  116  when configured as a transceiver, or the fourth EHF communication unit  120 , may further be configured to transmit an unlock code to the first device  102  when the second electromagnetic EHF signal is modulated. The unlock code may include a device identifier. In an embodiment, the communication unit  112  may receive the unlock code from the EHF communication unit  116 . The signal controller  118  may authorize the second device  104  based on the unlock code. In some embodiments, the EHF communication unit  108  may transmit an unlock code to the second device  104  and either the EHF communication unit  116  or the EHF communication unit  120  may receive the unlock code. The first signal controller  118  may authorize the first device  104  based on the received unlock code. 
     A signal controller of one of the devices may be configured to modulate an output or transmit an electromagnetic EHF signal contingent on meeting one or more predefined criteria. For example, the one or more predefined criteria may include matching at least one of a first data pattern, a first data rate, a first bit-error rate, and a first protocol of the first device  102  with a corresponding second data pattern, a second data rate, a second bit-error rate, and a second protocol of the second device  104 . The one or more predefined criteria may include determining if strength of the generated electrical EHF signal is greater than a predefined threshold for a predefined time period. In an embodiment, the first signal controller  118  may determine if strength of the received electromagnetic EHF signal is greater than a predefined threshold for a predefined time duration. 
     In some examples, the one or more predefined criteria or determination of whether the two devices are aligned may include detecting impedance of at least one of a first antenna of the first device  102  and/or a second antenna of the second device  104 . In some embodiments, the first signal controller  118  may detect impedance of at least one of the first antenna (such as antenna  206  as shown in  FIG. 2  or antenna  306  shown in  FIG. 3 ) and the second antenna. In some examples, the one or more predefined criteria may include determining and analyzing a time-of-flight for a round-trip EHF signal, i.e., for an electromagnetic EHF signal transmitted from one device to the other device and retransmitted back to the one device. The signal controller  118  may be configured to determine whether the generated electrical EHF signal indicates that the shield portion  106  and the shield portion  114  are in alignment. Further, the EHF communication unit  108  may be configured to transmit modulated signals to the second device  104  when the first device  102  and the second device  104  are in alignment. 
     In some embodiments, the signal controller of one of the devices may determine whether the other device is an acceptable or compatible device for communication. For example, the signal controller of one of the devices, such as signal controller  110 , may determine whether an unlock code transmitted by the other device, such as transmitted by the EHF communication unit  116 , is an acceptable unlock code. A signal controller may be configured to determine whether the electromagnetic EHF signal received from the other device is modulated with data formatted according to an acceptable qualification pattern. 
     In some embodiments, the user may move a position of at least one of the first device  102  and the second device  104  relative to each other when the generated electrical EHF signal indicates that the shield portion  106  and the shield portion  114  are not in alignment (See  FIG. 5A ). Further, the first device  102  and the second device  104  may be moved until the received electromagnetic EHF signal indicates that the shield portion  106  and shield portion  114  are in alignment (See  FIG. 5B ). The shield portion  106  and the shield portion  114  may form a continuous shield when aligned relative to each other and the shield portions are sufficiently close to each other. 
     The EHF communication unit  108  may transmit a modulated first electromagnetic EHF signal to the second device  104  in response to receipt by the first device  102  of a modulated second electromagnetic EHF signal from the second device  104 . The first device  102  and the second device  104  may be configured such that alignment of the EHF communication unit  108  and the EHF communication unit  116  results in substantial alignment of the shield portion  106  and the shield portion  114 . 
     The EHF communication unit  120  may be coupled to the signal controller  118  and may be configured to transmit the second electromagnetic EHF signal to the first device  102 . The EHF communication unit  112  may be configured to receive the second electromagnetic EHF signal from the second device  104 . The signal controller  110  may be configured to determine whether the first device  102  and the second device  104  are in alignment by assessing one or more characteristics of the second electromagnetic EHF signal transmitted by the EHF communication unit  120  and received by the EHF communication unit  112 . 
     Each of the first EHF communication units  108 ,  112 ,  116 , and  120  may include an insulating material, a chip having an integrated circuit (IC), and an antenna configured to communicate with the IC and held in a fixed location by the insulating material as shown and described in  FIGS. 2 and 3 . In some embodiments, the first and second devices may have contact surfaces that interlock or mate when the first and second EHF communication units are in alignment. The devices may also include one or more respective magnets to draw the devices together and/or LEDs for indicating a proper positioning between the devices. 
       FIG. 2  is a side view of an exemplary EHF communication circuit  200  showing a simplified view of some structural components. Communication circuit  200  may include one or more EHF communications units and may also include a signal controller as has been described for devices  102  and  104  in the communication system  100 . As illustrated, the communication circuit may include an integrated circuit package  201  that includes a die  202  mounted on a connector printed circuit board (PCB)  203 , a lead frame (not shown), one or more conductive connectors such as bond wires  204 , a transducer such as antenna  206 , and an encapsulating material  208 . 
     The die  202  may include any suitable structure configured as a miniaturized circuit on a suitable die substrate, and is functionally equivalent to a component also referred to as a “chip” or an “integrated circuit (IC).” The die substrate may be formed using any suitable semiconductor material, such as, but not limited to, silicon. The die  202  may be mounted in electrical communication with the lead frame. The lead frame (similar to lead frame  318  of  FIG. 3 ) may be any suitable arrangement of electrically conductive leads configured to allow one or more other circuits to operatively connect with the die  202 . The leads of the lead frame may be embedded or fixed in a lead frame substrate. The lead frame substrate may be formed using any suitable insulating material configured to substantially hold the leads in a predetermined arrangement. 
     Further, the electrical communication between the die  202  and leads of the lead frame may be accomplished by any suitable method using conductive connectors such as, one or more bond wires  204 . The bond wires  204  may be used to electrically connect points on a circuit of the die  202  with corresponding leads on the lead frame. In another embodiment, the die  202  may be inverted and conductive connectors including bumps, or die solder balls rather than bond wires  204 , which may be configured in what is commonly known as a “flip chip” arrangement. 
     The antenna  206  may be any suitable structure configured as a transducer to convert between electrical and electromagnetic signals. The antenna  206  may be configured to operate in an EHF spectrum, and may be configured to transmit and/or receive electromagnetic signals, in other words as a transmitter, a receiver, or a transceiver. In an embodiment, the antenna  206  may be constructed as a part of the lead frame. IC package  201  may include more than one antenna  206 . In another embodiment, the antenna  206  may be separate from, but operatively connected to the die  202  by any suitable method, and may be located adjacent to the die  202 . For example, the antenna  206  may be connected to the die  202  using antenna bond wires (similar to  320  of  FIG. 3 ). Alternatively, in a flip chip configuration, the antenna  206  may be connected to the die  202  without the use of the antenna bond wires (see  320 ). In other embodiments, the antenna  206  may be disposed on the die  202  or on the PCB  216 . 
     The encapsulating material  208  may hold the various components of the IC package  201  in fixed relative positions. The encapsulating material  208  may be any suitable material configured to provide electrical insulation and physical protection for the electrical and electronic components of the IC package. For example, the encapsulating material  208  may be a mold compound, glass, plastic, or ceramic. The encapsulating material  208  may be formed in any suitable shape. For example, the encapsulating material  208  may be in the form of a rectangular block, encapsulating all components of the IC package except the unconnected leads of the lead frame. One or more external connections may be formed with other circuits or components. For example, external connections may include ball pads and/or external solder balls for connection to a printed circuit board. 
     The IC package  201  may be mounted on a connector PCB  203 . The connector PCB  203  may include one or more laminated layers  212 , one of which may be a PCB ground plane  210 . The PCB ground plane  210  may be any suitable structure configured to provide an electrical ground to circuits and components on the IC package. 
       FIG. 3  is a simplified isometric view of another example of a communication circuit  300  showing some structural components. As with communication circuit  200 , communication circuit  300  may include one or more EHF communications units and may also include a signal controller as has been described for devices  102  and  104  in the communication system  100 . As illustrated, communication circuit  300  may include an IC package  301  that may in turn include a die  302 , a lead frame  318 , one or more conductive connectors such as bond wires  304 , a transducer such as antenna  306 , one or more antenna bond wires  320 , and an encapsulating material  308 . The die  302 , the lead frame  318 , one or more bond wires  304 , the antenna  306 , the antenna bond wires  320 , and an encapsulating material may be functionality similar to components such as the die  202 , the bond wires  204 , the antenna  206 , and the encapsulating material  208  of IC package  201  as described in  FIG. 2 . Further, communication circuit  300  may include a connector PCB similar to PCB  203 , not shown). 
     In  FIG. 3 , it may be seen that the die  302  is encapsulated in encapsulating material  308 , along with the bond wires  304  and  320 . In this embodiment, the IC package may be mounted on the connector PCB. The connector PCB may include one or more laminated layers, one of which may be a PCB ground plane. The PCB ground plane may be any suitable structure configured to provide an electrical ground to circuits and components on the PCB of the second EHF communication unit  314 . 
     Signal security and integrity are important when communicating between any two EHF communication units. One method for enhancing or ensuring proper signal security and integrity is to verify that a second EHF communication unit is within a predetermined range of a first EHF communication unit before or during a communication. To that end, systems and methods may be used for detecting the presence of a second EHF communication unit and/or for ensuring another device or device surface is within a certain distance. Examples of such systems and methods are described in U.S. Published Patent Application No. 2012/0319496, which is hereby incorporated in its entirety for all purposes. 
     Turning to  FIGS. 4A-4B , amplitude versus frequency graphs of typical emissions spectra are depicted, with superimposed lines  402  representing illustrative governmental emissions limits for a given licensed band.  FIG. 4A  depicts a graph of typical emissions spectra  404  for an unmodulated signal(s) or a low-level modulated signal. As depicted in  FIG. 4A , an unmodulated signal or a sufficiently low-level modulated signal may include a narrow band  404 A of emissions that are contained within the emissions limit  402 . The modulated signal may be low-level in the sense that modulation occurs at a low frequency so as to produce a low level of electromagnetic emissions. 
       FIG. 4B  depicts a graph of typical emission spectra  406  for a signal(s) modulated at frequencies commensurate with the information content the EHF carrier is able to convey, also referred to as a high-level modulated signal. It may be seen in  FIG. 4B  that a high-level modulated signal may produce a frequency band  406 A that is outside the licensed band. It is desirable to avoid producing emissions outside the licensed band. A graphical representation  406  shows emissions within a shielded enclosure of frequency. An emissions band  406 A is of frequency spectra  406  are outside the licensed band and emissions band  406 B are within the licensed band. For a communication circuit that is not shielded, then a portion of frequency spectra are outside the licensed band when a high-level modulated signal is produced. When the communication circuit is shielded, frequency band  406  represents the frequency spectra inside the shielded enclosure, and spectra  408  shows the frequency spectra outside the shielded enclosure. It is seen that when a shielded enclosure is used, the frequency spectra outside the shielded enclosure is within the emissions limits  402 . 
       FIGS. 5A-5B  are schematic illustrations of an exemplary communication system  500  showing a first device  502  relative to a second device  504  configured to avoid producing emissions outside a given band when properly aligned relative to each other. The first device  502  may include two exemplary communication units, specifically an EHF transmitter  506  and an EHF receiver  508 , electrically connected to a signal controller  510 . A discontinuous shield portion  512  may partly surround the EHF transmitter  506  and the EHF receiver  508 . In some examples, the shield portion may also extend around signal controller  510 . 
     For example, a portion of first device  502  may include a layer or section of material that acts to inhibit or block electromagnetic signals. This layer or section may be discontinuous in the sense that it may not form a continuous shield in every direction, but rather can include an opening or openings  514  in one or more directions along which electromagnetic EHF signals are transmitted from transmitter  506  and transmitted to receiver  508 . This configuration is represented in  FIG. 5A  by a U-shaped cross section. As shown in the figure, the shield portion  512  (corresponding to shield portion  106 ) may be constructed to facilitate a mating relationship with a corresponding shield  516  (corresponding to shield portion  114 ) on second device  504 . The shield portions  512  and  516  are discontinuous shields and may not adequately shield transmissions between the first device  502  and the second device  504  when the shield portions are not aligned.  FIG. 5A  shows the devices and thereby the shield portions out of alignment. Therefore, the first device and the second device may be moved until a proper alignment is established between the two devices, as shown in  FIG. 5B . 
     The EHF transmitter  506  may be an example of the previously described EHF communication unit  108 , and may be adapted to transmit selectively a modulated and an unmodulated EHF signal provided by one or more circuits in the first device  502  upstream to the signal controller  510 . For example, the EHF transmitter  506  may transmit a substantially constant signal, a modulated signal, an intermittent signal, a combination of these, or any other signal capable of being transmitted in the licensed EHF band. 
     The EHF receiver  508  may also be an example of the previously described EHF communication unit  112 , and may be adapted to receive an EHF signal and to provide that signal in electronic form to one or more circuits in the first device  502 , including the signal controller  510 . The signal controller  510  may determine whether an unmodulated signal received by EHF receiver  508  is adequate to enable modulation of transmitted signals. Transmitter  506  and receiver  508  may form a communication circuit  517 . 
     The second device  504  may be similar to the first device  502 , and may include an EHF receiver  518 , an EHF transmitter  520 , a signal controller  522 , as well as shield portion  512  with similar functions and connections as the corresponding components of the first device  502 . Receiver  518  and transmitter  520  may be part of a communication circuit  524 . The signal controller  522  may also be configured to receive modulated or unmodulated signals from receiver  518  that are received from other devices such as, but not limited to the first device  502 . 
     In some embodiments, the signal controller  510  of the first device  502  may determine whether the second device  504  is an acceptable or compatible device. In an embodiment, the signal controller  510  may determine whether the second device  504  is an acceptable device based on an unlock code. The unlock code may be a device identifier that can include alphanumeric data, symbols, or a combination of these. The second signal controller may determine whether the unlock code transmitted by the EHF transmitter  520  is an acceptable unlock code. The second signal controller may be configured to determine whether an electromagnetic EHF signal received by receiver  508  is modulated based on the one or more predefined criteria. For example, the signal controller may be configured to determine whether the received electromagnetic EHF signal is modulated with data formatted according to an acceptable qualification pattern. 
     Devices  502  and  504  may be changed or moved relative to each other when an electrical EHF signal generated from a received electromagnetic EHF signal indicates that shield portions  512  and  516  are not in alignment. The devices may be moved until the generated electrical EHF signal indicates that shield  512  and shield  516  are in alignment. When the devices are in alignment, the shield portions  512  and  516  may form a continuous shield  524  that reduces the amount of emissions, as was described with reference to  FIGS. 3A and 3B . 
     The EHF transmitter  506  may transmit a modulated electromagnetic EHF signal to the second device  504  in response to receipt by the first device  502  of a modulated electromagnetic EHF signal from the second device  504 . The devices  502  and  504  may be configured such that alignment of the EHF transmitter  506  and the EHF receiver  518  results in substantial alignment of shield portions  512  and  516 . 
     The signal controller  510  may be configured to determine whether the devices  502  and  504  are in alignment by assessing one or more characteristics of an electromagnetic EHF signal transmitted by EHF transmitter  520  and received by EHF receiver  508 . 
     The alignment of devices  502  and  504  refers to axial and proximal alignment of the EHF transmitter/receiver pairs, namely EHF transmitter  506  with EHF receiver  518  as well as EHF transmitter  520  with EHF receiver  508 . The proper alignment of these pairs may allow EHF signal communication between at least one of the pairs of transmitter and receiver and thus communication between the two devices. The shield portions  512  and  516  of the two devices, respectively, may also be configured to ensure that the shield portions are aligned and form a continuous shield  524  when the transmitter/receiver pairs are in proper alignment. Further, the shield portions may be configured to be in electrical contact when they are aligned relative to each other. 
     As mentioned previously, the discontinuous shield portions may form a continuous shield  524  around the transmitter/receiver pairs as shown in  FIG. 5B  when the shield portions are in an aligned and mated position. The continuous shield  524  around the EHF transmitter/receiver pairs may block spurious emissions sufficiently to comply with regulation emission limits. Thus, when the devices are properly aligned, the EHF transmitters may transmit modulated EHF signals or carriers without violating emission limits. 
     Further as has been mentioned, one or both of the devices may determine whether the other device is an acceptable device based on one or more criteria. When the devices are properly aligned, the respective signal controller may determine that the received signal is properly qualified and may enable modulation and accordingly produce a modulated EHF signal accordingly. Thereafter, the modulated EHF signal may be transmitted by the respective EHF transmitter to the counterpart receiver. 
     In an embodiment, the signal controller and EHF communication unit(s) in one or both of the devices may be adapted to provide verification of transmitter/receiver alignment. This may in turn provide a corresponding verification that physical shielding is also in proper alignment. This may allow the device to avoid transmission of modulated signals except when the shielding is in place to prevent excessive signals from being broadcast outside the licensed band. Taking device  502  as an illustrative example, this may be accomplished by configuring the signal controller  510  to output an unmodulated signal stream to transmitter  506  unless the EHF receiver  508  receives and passes along an indication of receipt of a qualified signal transmission from device  504 . In this example, that signal may be transmitted by EHF transmitter  520 . A transmitted signal may be checked to determine whether it meets certain predetermined criteria such as transmission strength or whether it includes one or more pieces of certain encoded information pertinent to the qualification determination. 
     In response to determining that a received transmission is qualified, the signal controller  510  may select a modulated signal stream to be passed to EHF transmitter  506  and transmitted. Likewise, signal controller  522  of device  504  may be configured to look for a qualified signal from device  502 , and may only transmit a modulated signal via EHF transmitter  520  in response to that qualified signal. As previously described, this mutual arrangement results in the prevention of modulated transmissions unless the transmitter/receiver pairs are aligned and the respective devices transmit in compliance with the qualification criteria. 
     The signal controller  522  and the signal controller  510  may be any suitable circuit configured to select between two or more signals based on one or more inputs. In the embodiment shown in  FIGS. 5A and 5B , a signal controller may include a multiplexer circuit (MUX)  602  as shown in  FIG. 6 . As discussed with reference to  FIGS. 5A and 5B , the multiplexer circuit  602  may be adapted to receive inputs or signals on an input  603 , such as signals from one or more signal generating circuits (not shown). The signal generating circuits may produce a modulating data baseband signal (not shown). The multiplexer circuit may further receive different types of input signals from which one is selected for transmitting to the associated transmitter, such as EHF transmitter  506  for signal controller  510 . These signals may include an exemplary pilot-tone signal input  604  that is an unmodulated carrier tone that produces emissions within a license-free band without relying on an electromagnetic shield. Logic 1 may be produced in signal input  614  to provide a simple unmodulated signal or carrier  604  received by the multiplexer circuit. A data sequence  606  may indicate an unlock code for transmitting to a second device, such as second device  504 . Another data sequence  608  may indicate a link enumeration or a qualification sequence or qualification pattern for transmitting to the second device. 
     As discussed with reference to  FIGS. 1, and 5A and 5B , the signal controller  522  may determine whether one or more criteria are satisfied before sending the first device a modulated data signal. A modulated output signal may be produced when the one or more criteria are satisfied. In an embodiment, the multiplexer circuit  602  may also receive indication signals  610 ,  612 , and  614  that result from a determination of the characteristics of signals received from the second device, such as device  504 . 
     In an embodiment, criteria determination circuits of the signal controller may provide the indication signals  610 ,  612 , and  614  to the multiplexer  602 . Indication signal  610  may provide an indication as to whether a received EHF electromagnetic signal strength is above a predefined threshold for a predefined time duration. Indication signal  612  may provide an indication as to whether a received EHF electromagnetic signal includes a proper unlock code. Indication signal  614  may provide an indication as to whether a received pattern meets a required link specification. 
       FIG. 7  is a flow chart illustrating an example of a method  700  for allowing communication between the first device  102  (or  502 ) and the second device  104  (or  504 ) while avoiding or reducing the production of electromagnetic emissions that are outside a licensed band. As discussed with reference to  FIG. 1 , the first device  102  ( 502 ) may include the EHF communication unit  108  (transmitter  506 ), the shield portion  106  (or  512 ), the signal controller  110  (or  510 ), and in some examples the EHF communication unit  112  (receiver  508 ). Similarly, the second device  104  ( 504 ) may include the shield portion  114  ( 516 ), the EHF communication unit  116  (receiver  518 ), the signal controller  118  ( 522 ), and in some examples the EHF communication unit  120  (transmitter  520 ). The device  102  ( 502 ) and the device  104  ( 504 ) may communicate with each other by transmitting and/or receiving electromagnetic signals. 
     At step  702 , a low-level modulated signal or carrier may be transmitted by the first device  102  ( 502 ). The modulated signal is being transmitted initially without confirmation that the two devices are in alignment. As mentioned, the modulated signal may be low-level in the sense that modulation occurs at a low frequency so as to produce a low level of electromagnetic emissions. In this example, the EHF communication unit  108  ( 506 ) may transmit the modulated signal to the device  104  ( 504 ). 
     At step  704 , it is determined whether the strength of the low-level modulated signal received by the receiver (such as, the EHF communication unit or receiver  116  or  518 , or more generally at the second device  104  or  504 ) is over a predetermined threshold. In other words, the amplitude of a signal may be compared with a predefined minimum signal amplitude (or predefined threshold) to determine whether the signal meets the predefined threshold that indicates proper alignment of a transmitter/receiver pair. If the predefined threshold is not met, then the user may be notified at step  706 , such as by a display, sound, light, or other sensible indicator. This may then prompt the user to adjust the relative position of the devices  102  ( 502 ) and  104  ( 504 ) at step  708 , and the signal strength checked again at step  704  while the first device continues to transmit the low-level modulated signal at step  702 . Since a user may move one or both of the devices, it is sufficient that the positions of the two devices relative to each other are moved. The second device may then continually monitor the signal strength and provide an indication as to whether alignment exists or continues to exist. 
     If at step  704  the signal strength is determined to be greater than the predefined threshold, then step  710  is performed, and if not, the signal strength is monitored while a user continues to perform step  708  by further moving the devices. In some examples, the second device may also transmit an unmodulated signal or a low-level modulated signal back to the first device, upon receipt of which the first device makes determinations of the propriety of the second device, similar to those described, for sending data signals to the second device. 
     At step  710 , the content of the signal may be analyzed to determine whether a desired, predefined unlock code is present. The unlock code would be data in the received low-level modulated signal. If at step  710  a desired unlock code is not present, then a user is notified at step  712 , and step  704  is repeated and the signal is analyzed again. 
     It is also possible that a spurious signal, or a signal from an unsupported transmitter, may be present, and further adjustment of the relative positions of the first device  102  ( 502 ) and the second device  104  ( 504 ) may be ineffective to meet the above-identified tests without removing the source of the spurious signal. If the predefined unlock code is present in the signal, 
     At step  714 , the signal may be further analyzed to determine whether an acceptable qualification pattern is present. If a proper qualification pattern is not present, then the user is notified and step  712  and the analysis returns to step  704  to continue checking the received signal for compliance with these tests. In some embodiments, when the proper qualification pattern is not present then adjustment of the relative device positions may or may not be needed. 
     Note that steps  704 ,  710 , and/or  714  constitute aspects of qualifying the first device, and may be performed in a different order or even in parallel. It is also noted that different, fewer or additional criteria may be used to qualify the first device. For example, antenna impedance may be detected, or time-of-flight for a round-trip signal may be analyzed to determine whether the devices are sufficiently close, as is disclosed in U.S. Published Patent Application No. 2012/0319496, which reference is incorporated herein by reference. 
     If all criteria are satisfied, then at step  716  a modulated signal may be transmitted from the second device to the first device. Thereafter at step  718 , a user may also be notified of proper alignment (i.e., that all criteria are met) by a suitable indicator. For example, an LED may be lit, an audible alert may be sounded, and/or a vibration may be created to notify the user about proper alignment of the two devices. The proper alignment of the first device  102  ( 502 ) and the second device  104  ( 504 ) may reduce or avoid the production of undesired emissions that are outside a licensed band by the limitation of transmitted emissions until formation of the continuous shield formed by the shield portions of the two devices is confirmed. Although not specifically shown, the first device may begin transmitting a low-level or high-level modulated first electromagnetic EHF signal to the second device in response to receipt by the first device of a second electromagnetic EHF signal from the second device that is modulated at a corresponding low or high level. 
     As discussed above, during operation of the second device, the received signal is continually monitored at step  720  to confirm that suitable alignment continues to exist. So long as the signal strength (or other determinant) is sufficient, the second device continues to transmit modulated signals to the first device. If at any time the signal strength diminishes below the threshold, the transmission of the modulated signal is terminated at step  722 , the user is notified at step  706  for adjustment of the two devices by the user at step  708 , and the process of linking the two devices is re-initiated at step  702 . 
       FIG. 8  is a flow chart illustrating another example of a method  800  for allowing communication between the first device  102  (or  502 ) and the second device  104  (or  504 ) while avoiding or reducing the production of electromagnetic emissions that are outside a licensed band. In this example, at step  802 , an unmodulated signal or carrier may be transmitted by the first device  102  ( 502 ). The unmodulated signal is being transmitted initially without confirmation that the two devices are in alignment because it inherently produces low levels of emissions even when the devices do not form an electromagnetic shield. In this example, the EHF communication unit  108  ( 506 ) may transmit the modulated signal to the device  104  ( 504 ). 
     At step  804 , it is determined whether the strength of the unmodulated signal received by the receiver (such as, the EHF communication unit or receiver  116  or  518 , or more generally at the second device  104  or  504 ) is over a predetermined threshold. If the predefined threshold is not met, then the user may be notified at step  806 . This may then prompt the user to adjust the relative position of the devices  102  ( 502 ) and  104  ( 504 ) at step  808 , and the signal strength checked again at step  804  while the first device continues to transmit the unmodulated signal at step  802 . 
     Since a user may move one or both of the devices, it is sufficient that the positions of the two devices are moved relative to each other. The second device may then continually monitor the signal strength and provide an indication as to whether alignment exists or continues to exist based on the signal strength. As also mentioned above, other criteria may be examined for determining alignment, such as antenna impedance or time-of-flight for a round-trip signal. 
     If at step  804  the strength of the signal received at the second device is determined not to be greater than the predefined threshold, the second device continues to monitor the received signal strength at step  804  while a user continues to move the devices at step  708 . If the received signal strength is determined to be greater than the predefined threshold, then the second device may in turn transmit an unmodulated signal or even a low-level modulated signal to the first device at step  810  for use by the first device in determining whether it is appropriate to send data to the second device using similar steps. 
     Then, at step  812  a determination may be made at the first device as to whether the signal received from the second device is greater than a predefined threshold, and if not, the signal strength continues to be monitored while a user continues to perform step  708  by further moving the devices. If the signal received from the second device is greater than a predefined threshold, the first device may then begin transmitting a signal modulated with an unlock code and with a predefined qualification pattern at step  814 . This signal may be a low-level modulated signal or it may be a high-level modulated signal. 
     After the second device has determined that the received signal has sufficient strength, at step  816 , the content of the signal may be analyzed to determine whether a desired, predefined unlock code is present in the modulated signal received from the first device. If at step  816  a desired unlock code is not present, then a user is notified at step  818 , and step  804  is repeated and the signal is analyzed again. 
     If the predefined unlock code is present in the signal, at step  816 , the signal may be further analyzed at step  820  to determine whether an acceptable qualification pattern is present. If a proper qualification pattern is not present, then the user is notified at step  818  and the analysis returns to step  804  to continue checking the received signal for compliance with these tests. In some embodiments, when the proper qualification pattern is not present then adjustment of the relative device positions may or may not be needed. 
     If a required qualification pattern is present, then at step  822  the second device transmits a modulated signal containing data, including control and further handshake protocols to establish communication with the first device. A user may also be notified at step  824  with an indication that the two devices are aligned and communication is taking place. As in method  700 , the first device may begin transmitting a high-level modulated first electromagnetic EHF signal to the second device in response to receipt by the first device of a high-level modulated second electromagnetic EHF signal from the second device. 
     During operation of the second device, the received signal is continually monitored at step  826  to confirm that suitable alignment continues to exist. So long as the signal strength (or other determinant) is sufficient, the second device continues to transmit modulated signals to the first device. If at any time the signal strength diminishes below the threshold, the transmission of the modulated signal is terminated at step  828 , the user is notified at step  806  for adjustment of the two devices by the user at step  808 , and the process of linking the two devices is re-initiated at step  802 . 
     Again, the steps shown for qualifying the first device for communication with the second device are exemplary, and may be performed in a different order or even in parallel. Also, different, fewer or additional criteria may be used to qualify the first device for communication. 
     If all criteria are satisfied, then at step  716  a modulated signal may be transmitted from the second device to the first device. Thereafter at step  718 , a user may also be notified of proper alignment (i.e., that all criteria are met) by a suitable indicator. For example, an LED may be lit, an audible alert may be sounded, and/or a vibration may be created to notify the user about proper alignment of the two devices. As discussed above, the proper alignment of the first device  102  ( 502 ) and the second device  104  ( 504 ) may reduce or avoid the production of undesired emissions that are outside a licensed band by the limitation of transmitted emissions until formation of the continuous shield formed by the shield portions of the two devices is confirmed. 
     It is believed that the disclosure set forth herein encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Each example defines an embodiment disclosed in the foregoing disclosure, but any one example does not necessarily encompass all features or combinations that may be eventually claimed. Where the description recites “a” or “a first” element or the equivalent thereof, such description includes one or more such elements, neither requiring nor excluding two or more such elements. Further, ordinal indicators, such as first, second or third, for identified elements are used to distinguish between the elements, and do not indicate a required or limited number of such elements, and do not indicate a particular position or order of such elements unless otherwise specifically stated.