Abstract:
Methods, systems, and apparatus for EM isolation structures. One of the apparatus includes a communication module, the communication module including: a printed circuit board; a plurality of integrated circuit packages, each integrated circuit package including at least one transmitter, receiver, or transceiver; and one or more metallic blocking structures configured to at least partially encircle a corresponding one of the plurality of integrated circuit packages, wherein each metallic blocking structure is configured to reduce signal leakage from the corresponding integrated circuit package.

Description:
BACKGROUND 
       [0001]    This specification relates to electromagnetic communications. 
         [0002]    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 high frequency integrated circuits are able to provide greater functionality than previous generations of products. The additional functionality has typically included the processing of increasingly larger amounts of data at increasingly higher speeds. 
         [0003]    Many conventional electronic systems include multiple printed circuit boards (PCBs) upon which ICs are mounted, and through which various signals are routed to and from the ICs. The need to communicate information between PCBs in electric systems with at least two PCBs have led to the development of a variety of connector and backplane architectures to facilitate information flow between PCBs. However, conventional connector and backplane architectures typically introduce a variety of impedance discontinuities into the signal path, obstructing transmission, and resulting in a degradation of signal quality or integrity. Connecting to PCBs by conventional means, e.g., signal-carrying mechanical connectors, generally creates discontinuities, requiring expensive electronics to negotiate. Conventional mechanical connectors may also wear out over time, require precise alignment and manufacturing methods, and are susceptible to mechanical jostling. 
         [0004]    Signal isolation between different communication links is typically necessary in contactless communications to maintain signal quality. Conventional techniques for signal isolation include separation by frequency, time, code, polarization, and/or space. 
       SUMMARY 
       [0005]    In general, one innovative aspect of the subject matter described in this specification can be embodied in apparatus that include a communication module, the communication module including: a printed circuit board; multiple integrated circuit packages, each integrated circuit package including at least one transmitter, receiver, or transceiver; and one or more metallic blocking structures configured to at least partially encircle a corresponding one of the multiple integrated circuit packages, wherein each metallic blocking structure is configured to reduce signal leakage from the corresponding integrated circuit package. Other embodiments of this aspect include corresponding systems and methods. 
         [0006]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The multiple integrated circuit packages include one or more transmitter integrated circuit packages, one or more receiver integrated circuit packages, or one or more transceiver integrated circuit packages. Each of the multiple integrated circuit packages are positioned on a surface of the printed circuit board and wherein the spacing between each integrated circuit package is specified based on the reduced signal leakage provided by the one or more metallic blocking structures. The one or more metallic blocking structures each form a channel for passing electromagnetic signals. One of the metallic blocking structures is shaped to direct signal propagation in a specified direction. The metallic blocking structure is shaped to partially cover a portion of the integrated circuit package. The partial coverage of the integrated circuit package provides an open channel above a transducer of the integrated circuit package. The partial coverage of the integrated circuit package is provided by an asymmetrical horn shape. The partial coverage of the integrated circuit package is provided by a symmetrical horn shape. Each signal blocking structure is configured to reduce cross-talk between integrated circuit packages. 
         [0007]    In general, one innovative aspect of the subject matter described in this specification can be embodied in apparatus that include a communication module, the communication module including: a printed circuit board; multiple integrated circuit packages, each integrated circuit package including at least one transmitter, receiver, or transceiver; and one or more absorber structures configured to at least partially encircle a corresponding one of the multiple integrated circuit packages, wherein each absorber structure is configured to reduce signal leakage from the corresponding integrated circuit package. Other embodiments of this aspect include corresponding systems and methods. 
         [0008]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The plurality of integrated circuit packages includes one or more transmitter integrated circuit packages, one or more receiver integrated circuit packages, or one or more transceiver integrated circuit packages. Each of the multiple integrated circuit packages are positioned on a surface of the printed circuit board and wherein the spacing between each integrated circuit package is specified based on the reduced signal leakage provided by the one or more absorber structures. The communication module further comprises: multiple signal guiding structures, each signal guiding structure sounding at least a portion of a corresponding integrated circuit package. An absorber structure of the one or more absorber structures surrounds a corresponding signal guiding structure of the multiple signal guiding structures. The absorber structure has a varying thickness. The absorber structure is shaped to partially cover a portion of a corresponding integrated circuit package. 
         [0009]    In general, one innovative aspect of the subject matter described in this specification can be embodied in apparatus that include a communication module, the communication module including multiple integrated circuit packages, each integrated circuit package including at least one transmitter, receiver, or transceiver; a housing, wherein the housing is configured to enclose a the communication module; and one or more metallic blocking structures configured to at least partially encircle a corresponding one of the multiple integrated circuit packages, wherein each metallic blocking structure is configured to reduce signal cross talk between integrated circuit packages. Other embodiments of this aspect include corresponding systems and methods. 
         [0010]    In general, one innovative aspect of the subject matter described in this specification can be embodied in apparatus that include a communication module, the communication module including multiple integrated circuit packages, each integrated circuit package including at least one transmitter, receiver, or transceiver; a housing, wherein the housing is configured to enclose a the communication module; and one or more absorber structures configured to at least partially encircle a corresponding one of the multiple integrated circuit packages, wherein each absorber structure is configured to reduce signal leakage from the corresponding integrated circuit package. Other embodiments of this aspect include corresponding systems and methods. 
         [0011]    The subject matter described in this specification can be implemented in particular embodiments so as to realize one or more of the following advantages. The isolation structures can reduce cross-talk between communication channels having a small separation distance. Consequently, the overall package footprint of a communication module can be minimized. Isolation structures can be used to preserve preserve frequency spectrum and avoid time-sharing, which allows for faster data transfer. The shielding against stray signals provided by the disclosed isolation structures are effective, simple, easy to integrate, and are low cost. 
         [0012]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is an overhead view of an example IC package. 
           [0014]      FIG. 2  shows a side view representation of an example communication device including an IC package. 
           [0015]      FIG. 3  is a side view of an example communication module including a signal guiding structure. 
           [0016]      FIG. 4  is a side view diagram illustrating an example of communication between a transmitter and a receiver. 
           [0017]      FIG. 5A  shows a side view diagram illustrating a first example metallic signal isolation structure. 
           [0018]      FIG. 5B  shows a top view diagram illustrating the first example metallic signal isolation structure of  FIG. 5A . 
           [0019]      FIG. 6  shows a side view diagram illustrating a second example metallic signal isolation structure. 
           [0020]      FIG. 7  shows a side view diagram illustrating a third example metallic signal isolation structure. 
           [0021]      FIG. 8A  shows a side view diagram illustrating a first example absorber signal isolation structure. 
           [0022]      FIG. 8B  shows a top view diagram illustrating the first example absorber signal isolation structure of  FIG. 8A . 
           [0023]      FIG. 9A  shows a side view diagram illustrating a second example absorber signal isolation structure. 
           [0024]      FIG. 9B  shows a top view diagram illustrating the second example absorber signal isolation structure of  FIG. 9A . 
           [0025]      FIG. 10A  shows a side view diagram illustrating a third example absorber signal isolation structure. 
           [0026]      FIG. 10B  shows a top view diagram illustrating the third example absorber signal isolation structure of  FIG. 10A . 
           [0027]      FIG. 11  shows a side view diagram illustrating a fourth example absorber signal isolation structure. 
           [0028]      FIG. 12  shows a perspective view diagram illustrating a fourth example metallic signal isolation structure. 
           [0029]      FIG. 13  shows a side view diagram illustrating a fifth example metallic signal isolation structure. 
       
    
    
       [0030]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0031]    This specification describes electromagnetic (EM) isolation structures for contactless communication. In particular, this specification describes the use of signal isolation structures to guide signals and reduce cross-talk between communication channels. This specification describes both metallic and absorber structures that can be used to isolate signals that might otherwise interfere with each other, e.g., between communication channels. The signal isolation structures are used to reduce cross talk between communication channels while minimizing the physical spacing between the channels. 
         [0032]    Contactless communication may be used to provide signal communications between components on a device or may provide communication between devices. In one example, tightly-coupled transmitter/receiver pairs may be deployed with a transmitter disposed at a terminal portion of a first conduction path and a receiver disposed at a terminal portion of a second conduction path. The transmitter and receiver may be disposed in close proximity to each other depending on the strength of the transmitted energy, and the first conduction path and the second conduction path may not be contiguous with respect to each other. In some examples, the transmitter and receiver may be disposed on separate circuit carriers positioned with transducers (e.g., one or more antennas) of the transmitter/receiver pair in close proximity. 
         [0033]    A transmitter, receiver, or transceiver may be configured as an integrated circuit (IC) package, in which one or more transducers may be positioned adjacent to a die and held in place by a dielectric or insulating encapsulation or bond material. A transducer may also be held in place by a lead frame substrate. Examples of transducers embedded in IC packages are shown in the drawings and described below. Note that IC packages may also be referred to as simply packages, and are examples of contactless communication units that are also variously referred to as communication units, communication devices, comm-link chips, comm-link chip assemblies, comm-link chip packages, and/or comm-link packages, which may be configured in various ways. For example, IC packages, communication units, communication devices, comm-link chips, comm-link chip assemblies, comm-link chip packages, and/or comm-link packages may each include one or more ICs, chips, or dies and have circuit functionality appropriate for particular applications. 
         [0034]      FIG. 1  shows an example IC package  100 . The IC package  100  includes a die  102  and a transducer  104  providing conversion between electrical and EM signals. The IC package  100  may include additional structures, for example, conductive connectors, such as bond wires, electrically connecting the transducer to bond pads connected to a transmitter and/or receiver circuit included in die  102 . The IC package  100  further includes an encapsulating material  106  formed around at least a portion of the die  102  and/or the transducer  104 . In the example IC package  100 , the encapsulating material  104  completely covers the die  100  and the transducer  104 . 
         [0035]    The die  102  includes any suitable structure configured as a circuit on a suitable die substrate. In some implementations, the die can alternatively be referred to as a chip or an integrated circuit. The die substrate may be composed of any suitable semiconductor material, for example, silicon. In some implementations, the die  102  has a length and a width dimension each of substantially 1.0 mm to about 2.0 mm. The die  102  may be mounted with electrical conductors, such as a lead frame, not shown in  FIG. 1 , electrically coupling the die  102  to one or more external circuits. The IC package  100  can further include a transformer to provide impedance matching between a circuit on the die  102  and the transducer  104 . 
         [0036]    The transducer  104  may be in the form of a folded dipole or loop antenna and is configured to transmit and/or receive electromagnetic signals. In some implementations, the transducer  104  is configured to operate at radio frequencies including radio frequencies in the extremely high frequency (EHF) band of the electromagnetic spectrum, e.g., frequencies from 30 to 300 gigahertz. As shown in IC package  100 , the transducer  104  is separate from the die  102 , but is coupled to the die  102  by suitable conductors, not shown. 
         [0037]    The dimensions of the transducer are determined such that they are suitable for operation in the specified frequency band of the electromagnetic spectrum, e.g., the EHF band. 
         [0038]    In one example, a loop configuration of the transducer can be configured to include a substantially 0.1 mm band of material, laid out in a loop substantially 1.4 mm long and substantially 0.53 mm wide, with a gap of substantially 0.1 mm at the mouth of the loop, and with the edge of the loop approximately 0.2 mm from the edge of die  102 . 
         [0039]    The encapsulating material  106  can be used to assist in holding the various components of IC package  100  in fixed relative positions. The encapsulating material  106  may be formed from a suitable material configured to provide electrical insulation and physical protection for the components of IC package  100 . Additionally, the encapsulating material  106  can be selected from a material that does not impede, or that optimizes passage of, signals to or from the transducer  104 . For example, the encapsulating material  106  can be composed of glass, plastic, or ceramic. The encapsulating material  106  may also be formed in any suitable shape. For example, the encapsulating material  106  may be in the form of a rectangular block, encapsulating all components of the IC package  100  except for any unconnected ends of conductors connecting the die  102  to external circuits. 
         [0040]      FIG. 2  shows a side view representation of an example communication device  200  including an IC package  202  mounted to a PCB  204 . The IC package  202  includes a die  206 , a ground plane  208 , a transducer  210 , and one or more bond wires  212  connecting the die  206  to the transducer  210 . The die  206  and transducer  210  are mounted on a package substrate  214  and encapsulated in an encapsulating material. The ground plane  208  is within the package substrate  214  and is a suitable structure configured to provide an electrical ground for the transducer  210 . The ground plane  208  can extend the entire length of the package substrate  214  or just a portion, in particular, a portion underneath the transducer  210 . The PCB  204  includes a top dielectric layer  216  having a surface  218 . The IC package  202  is mounted to the surface  218  with mounting bumps  220  attached to a metallization pattern (not shown). 
         [0041]    The PCB  204  also optionally includes a layer  222  spaced from dielectric layer  216  made of conductive material forming a ground plane within the PCB  204 . The PCB ground plane may be any suitable structure configured to provide an electrical ground to circuits and components on the PCB  204 . 
         [0042]      FIG. 3  is a side view of an example communication module  300  including a signal guiding structure. As shown in  FIG. 3 , the communication module  300  includes a PCB  302 , an IC package  304 , and a signal guiding structure  306  providing a signal pathway. The communication module  300 , can include a transmitter or receiver for transmitting or receiving signals, e.g., radio frequency signals. 
         [0043]    In particular, the IC package  304  can correspond to the IC packages described above with respect to  FIGS. 1 and 2 . The IC package  304  is mounted on the PCB  302 . For example, the IC package  304  can be mounted to the PCB as described with respect to  FIG. 2 . 
         [0044]    The communication module  300  can be configured to transmit or receive data using radio frequency communication. For example, if the communication module  300  includes a transmitter, the communication module  300  can transmit data, which can then be received by a receiver, e.g., of another communication module. 
         [0045]    The signal guiding structure  306  is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The signal guiding structure  306  can surround a perimeter of the IC package and extend in the direction of signal transmission and/or reception by a specified amount to provide a channel for emitted or received RF signals. For example, the signal guiding structure  306  can have a height  310  suitable for a particular device including the communication module  300  and that allows the signal guiding structure  306  to be positioned in proximity to a corresponding signal guiding structure of another communication module when used to communicate with another device. The height of the signal guiding structure  306  relative to the PCB  302  can be configured such that when the communication module  300  is positioned the signal guiding structure  306  is proximal to an external device housing. The signal guiding structure can be composed of a suitable material that is configured to reduce extraneous signals without disrupting passage of communications along the channel formed by the signal guiding structure  306 . 
         [0046]      FIG. 3  illustrates one IC package  304  mounted to the PCB  302 . However, in other implementations, more than one IC package can be mounted to the same PCB  302 . For example, a linear array of two or more IC packages, each having a corresponding signal guiding structure, are mounted to a single PCB. 
         [0047]    The communication module  300  can be part of a communication system of a device, e.g., a computer, mobile phone, tablet, kiosk, or other device/system. The communication system can be configured to provide contactless communication using one or more IC packages. For example, the communication system can include two IC packages, one configured as a transmitter and the other configured as a receiver. The communication system can be in communication with a storage device. Thus, for example, the communication system can transfer data between the data storage unit and an external device using contactless communication provided by the IC packages. 
         [0048]      FIG. 4  is a side view diagram  400  illustrating an example of communication between a transmitter (Tx) and a receiver (Rx). For example, a user of a first device may wish to exchange data with a second device. The two devices can be positioned in proximity to each other such that the respective communication modules for transmitting and receiving data are aligned and in range of each other. In particular, for EHF frequencies, the transmitter and receiver of the two devices may need to be within specified distances. The distances can vary, for example, depending on the particular frequencies used, the materials between the transmitter and receiver, and the strength of the transmission. 
         [0049]    In  FIG. 4 , a first device includes a first communication module having a transmitter IC package  402  positioned on a first PCB  404 . The transmitter IC package  402  is surrounded by a first signal guiding structure  406  forming a channel. The first signal guiding structure  406  extends to a surface of a first housing  408  of the first device. For example, the first device can be a first mobile phone and the first housing  408  can correspond to the outer case of the first mobile phone. 
         [0050]    A second device includes a second communication module having a receiver IC package  410  positioned on a second PCB  412 . The receiver IC package  410  is surrounded by a second signal guiding structure  414  forming a channel. The second signal guiding structure  414  extends to a surface of a second housing  416  of the second device. For example, the second device can be a second mobile phone and the second housing  416  can correspond to the outer case of the second mobile phone. The signal guiding structures can be formed of metallic or metallic lined walls that surround the IC package  410 . 
         [0051]    As illustrated by diagram  400 , the first signal guiding structure  406  and the second signal guiding structure  414  are aligned and an outer surface of the first housing  408  and the second housing  416  are in physical contact to provide optimal communication distance and interference. 
         [0052]    A data transmission from the transmitter IC package  402  passes through the channel formed by the first signal guiding structure  406  and the second signal guiding structure  414  to the receiver IC package  410 . For example, a pair of devices can communicate data between each other by transmitting data from the transmitter IC package  402  to the receiver IC package  410 . The signal guiding structures along with proper alignment can maximize the power of the transmission that is received by the receiver IC package. In some implementations, the signal guiding structures can be formed from, or include a layer of, a metallic material that reflects the transmitted data along the signal guiding structures toward the receiver. In some other implementations, the signal guiding structures can be formed from, or include a layer of, an electromagnetic absorbing material to reduce stray signals that may cause interference. 
         [0053]    Although transmitted signals from a transmitter are intended for receipt by a particular receiver, cross talk caused by leaking of signals to another channel can result in unintended coupling that interferes with communication on that other channel. With small spacing between communication channels, e.g., between integrated circuit packages, mechanical structures can be used to isolate signals that may otherwise interfere with each other. The following figures describe example structures for reducing signal leakage allowing for small spacing between communication channels. 
         [0054]    Metallic Structures 
         [0055]      FIG. 5A  shows a side view diagram  500  illustrating a first example metallic signal isolation structure. In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0056]    As shown in diagram  500 , an IC package  502 , for example a transmitter IC package, is positioned on a PCB  504 . The IC package  502  is at least partially encircled by a metallic outfit  506 . The metallic outfit  506  forms a channel extending from the PCB  504  to a surface of a housing  508 . For example, the housing  508  can be the housing portion of a device such as portion of a mobile phone case. 
         [0057]    In some implementations, the housing portion  508  includes a portion formed from a different material than other portions of the housing portion  508 . For example, the housing portion  508  can be primarily formed of a metallic material that would inhibit passage of electromagnetic signals to or from the IC package. The metallic material can also cause signals to be confined within the channel so that minimal signal energy is dissipated outside of the communication link. A portion of the housing portion  508  that is in a transmission path of signals to or from the IC package  502  can be made of a different material such as plastic that allows for transmission of the signals. 
         [0058]    The metallic outfit  506  functions as a signal guiding structure that is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The metallic outfit  506  can at least partially surround a perimeter of the IC package  502  and extend in the direction of signal transmission and/or reception by a specified “height” relative to the PCB  504  to provide a channel for emitted or received RF signals. 
         [0059]    The metallic outfit  506  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the metallic outfit makes a substantially right angle after rising to a particular height above the IC package  502 . From the height, the metallic outfit extends over a portion of the IC package  502  such that only a portion is open as a channel to the housing  508 . Opposite the overhang, the metallic outfit forms a side wall to the housing portion  508  that is substantially perpendicular to the PCB  504 . In some alternative implementations, the side walls of the metallic outfit can have a specified angle from perpendicular to the PCB  504 , e.g., +/−30 degrees. The open portion can be positioned over a transducer of the IC package  502 , e.g., a loop antenna. In alternative implementations, the overhanging portion of the metallic outfit can have an angle up toward the housing or down toward the IC package. Additionally, portions of the metallic outfit  506  can have a curved shape instead of linear segments. 
         [0060]      FIG. 5B  shows a top view diagram  510  illustrating the first example metallic signal isolation structure of  FIG. 5A . In particular, diagram  510  shows metallic outfit  506  covering a portion of the IC package  502 , leaving a region over a transducer  512  open. Thus, the IC package  502  is mostly enclosed by the metallic outfit  506  except for the open channel portion. 
         [0061]      FIG. 6  shows a side view diagram  600  illustrating a second example metallic signal isolation structure. In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0062]    As shown in diagram  600 , an IC package  602 , for example a transmitter IC package, is positioned on a PCB  604 . The IC package  602  is at least partially encircled by a metallic outfit  606 . The metallic outfit  606  forms a channel extending from the PCB  604  to a surface of a housing  608 . For example, the housing  608  can be the housing portion of a device such as portion of a mobile phone case. 
         [0063]    In some implementations, the housing portion  608  includes a portion formed from a different material than other portions of the housing portion  608 . For example, the housing portion  608  can be primarily formed of a metallic material that would inhibit passage of electromagnetic signals to or from the IC package  602 . A portion of the housing portion  608  that is in a transmission path of signals to or from the IC package  602  can be made of a different material such as plastic that allows for transmission of the signals. 
         [0064]    The metallic outfit  606  functions as a signal guiding structure that is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The metallic outfit  606  can at least partially surround a perimeter of the IC package  602  and extend in the direction of signal transmission and/or reception by a specified “height” relative to the PCB  604  to provide a channel for emitted or received RF signals, e.g., similar to the metallic outfit  506 . The metallic outfit can be used for IC packages having a transmitter as well as IC packages having a receiver. For example, the angle of the metallic horn shown in  FIG. 6  can provide a more gradual transition between large (device housing side) and small apertures (side closer to the IC package). The more gradual transition, as opposed to an abrupt one, can provide better performance because discontinuities generally diffract RF energy. 
         [0065]    The metallic outfit  606  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the metallic outfit makes a substantially right angle after rising to a particular height above the IC package  602 . From the height, the metallic outfit extends over a portion of the IC package  602  such that only a portion is open as a channel to the housing  608 . Opposite the overhang, the metallic outfit forms a sidewall to the housing portion  608  that is substantially perpendicular to the PCB  604 . The overhang forms an asymmetrical horn shape that angles back in the opposite direction and toward the housing portion  608 . The open portion can be positioned over a transducer of the IC package  602 . In alternative implementations, the overhanging portion of the metallic outfit can have an angle up toward the housing or down toward the IC package  602  instead of a right angle compared to the sidewall. 
         [0066]      FIG. 7  shows a side view diagram  700  illustrating a third example metallic signal isolation structure. In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0067]    As shown in diagram  700 , an IC package  702 , for example a transmitter IC package, is positioned on a PCB  704 . The IC package  702  is at least partially encircled by a metallic outfit  706 . The metallic outfit  706  forms a channel extending from the PCB  704  to a surface of a housing  708 . For example, the housing  708  can be the housing portion of a device such as portion of a mobile phone case. 
         [0068]    In some implementations, the housing portion  708  includes a portion formed from a different material than other portions of the housing portion  708 . For example, the housing portion  708  can be primarily formed of a metallic material that would inhibit passage of electromagnetic signals to or from the IC package  702 . A portion of the housing portion  708  that is in a transmission path of signals to or from the IC package  702  can be made of a different material such as plastic that allows for transmission of the signals. 
         [0069]    The metallic outfit  706  functions as a signal guiding structure that is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The metallic outfit  706  can at least partially surround a perimeter of the IC package  702  and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. 
         [0070]    The metallic outfit  706  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the metallic outfit makes a substantially right angle after rising to a particular height above the IC package  702  from at least two sides of the IC package  702 . From the height, the metallic outfit extends from each respective side of one or more sides and over a portion of the IC package  702  such that only a portion is open as a channel to the housing  708 . The overhang thus forms symmetrical horns that angle back in the opposite direction and toward the housing portion  708 . The open portion can be positioned over a transducer of the IC package  702 . In alternative implementations, the overhanging portion of the metallic outfit can have an angle up toward the housing or down toward the IC package  702 . 
         [0071]      FIGS. 6 and 7  illustrate cross sections along a particular plane. However, the respective metallic outfits illustrated in the example views can include structures on other sides not illustrated by the cross-section. For example, instead of a single or double horn shape, the metallic outfit can include a horn on any number of sides surrounding the IC package. An example three sided horn metallic outfit is shown in  FIG. 12 . An example two sided horn metallic outfit is shown in  FIG. 13 . 
         [0072]    In  FIG. 12 , a perspective view diagram  1200  illustrates a fourth example metallic signal isolation structure. As shown in diagram  1200 , an IC package  1202 , for example a transmitter IC package, is positioned on a PCB  1204 . The IC package  1202  is at least partially encircled by a metallic outfit  1206 . The metallic outfit  1206  forms a channel extending from the PCB  1204  to a surface of a housing (not shown). 
         [0073]    The metallic outfit  1206  can at least partially surround a perimeter of the IC package  1202  and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. The metallic outfit  1206  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the metallic outfit makes a substantially right angle after rising to a particular height above the IC package  1202  from at least three sides of the IC package  1202  illustrated by portions  1208 ,  1210 , and  1212 . 
         [0074]    From the height, the metallic outfit extends from each respective side of the three sides and over a portion of the IC package  1202  such that only a portion is open as a channel to the housing. The three overhang portions are shown as joined together forming a continuous overhang around three sides of the metallic outfit  1206 . In some implementations, an overhang portion can be included on the fourth side. The overhang angles back in the opposite direction similar to the metallic outfits shown in  FIGS. 6 and 7 . Although straight lines and right angles are illustrated in diagram  1200 , the metallic outfit  1206  can include one or more curved or angled segments in place of linear segments. 
         [0075]    In  FIG. 13 , a side view diagram  1300  illustrates a fifth example metallic signal isolation structure. As shown in diagram  1300 , an IC package  1302 , for example a transmitter IC package, is positioned on a PCB  1304 . The IC package  1302  is at least partially encircled by a metallic outfit  1306 . The metallic outfit  1306  forms a channel extending from the PCB  1304  to a surface of a housing (not shown). 
         [0076]    The metallic outfit  1306  can at least partially surround a perimeter of the IC package  1302  and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. The metallic outfit  1306  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the metallic outfit makes a substantially right angle after rising to a particular height above the IC package  1302  from at least three sides of the IC package  1302 . However, in contrast to the metallic outfit of  FIG. 7 , the two sides are adjacent rather than opposite, illustrated by portions  1308  and  1310 . 
         [0077]    From the height, the metallic outfit extends from each respective side of the two adjacent sides and over a portion of the IC package  1302  such that only a portion is open as a channel to the housing. The adjacent overhangs  1308  and  1310  of the metallic outfit  1306  angle back in the opposite direction similar to the metallic outfits shown in  FIGS. 6 and 7 . Although straight lines and right angles are illustrated in diagram  1300 , the metallic outfit  1306  can include one or more curved or angled segments in place of linear segments. 
         [0078]    Absorber Structures 
         [0079]      FIG. 8A  shows a side view diagram  800  illustrating a first example absorber signal isolation structure.  FIG. 8B  shows a top view diagram  801  illustrating the first example absorber signal isolation structure of  FIG. 8A . 
         [0080]    In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0081]    As shown in diagram  800 , an IC package  802 , for example a transmitter IC package, is positioned on a PCB  804 . The IC package  802  is at least partially encircled by an absorbing outfit  810 . The absorbing outfit  810  forms a channel extending from the IC package  802  to a surface of a housing portion  808 . 
         [0082]    The absorbing outfit  810  is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. For example, the absorbing outfit  810  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. The absorbing outfit  810  can at least partially surround a perimeter of the IC package and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. 
         [0083]    The absorbing outfit  810  can be positioned relative to communication units, e.g., an IC package, to absorb signals that might otherwise cause crosstalk to adjacent channels. In some implementations, the absorbing outfit is placed around each IC package on a communication module whether it is a transmitter, or receiver. 
         [0084]    In  FIGS. 8A-8B , the absorbing outfit  810  forms an absorptive wall around the IC package  802 . In particular, in the example of  FIGS. 8A-B , the absorbing outfit  810  can be positioned on the PCB  804  encircling the IC package  802  and extending substantially to a surface of the housing portion  808 . The absorbing outfit  810  is formed from a material that absorbs electromagnetic radiation, particularly radio frequency electromagnetic radiation including EHF RF electromagnetic radiation. For example, the absorbing outfit  810  can be composed of a silicone, epoxy or other injection-molded plastic (not silica or silicon) with ferrite or iron particle loading. In some implementations, the material is further selected based on heat tolerance properties. For example, the material can be selected based in part on a melting or deformation point in excess of temperatures generated by device components. The absorbing outfit  810  can have a thickness configured to optimize the amount of stray signal absorption and may depend on the particular absorbing material used and the proximity to another communication channel. 
         [0085]      FIG. 9A  shows a side view diagram  900  illustrating a second example absorber signal isolation structure.  FIG. 9B  shows a top view diagram  901  illustrating the second example absorber signal isolation structure of  FIG. 9A . 
         [0086]    For ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0087]    As shown in diagram  900 , an IC package  902 , for example a transmitter IC package, is positioned on a PCB  904 . The IC package  902  is at least partially encircled by an absorbing outfit  910 . The absorbing outfit  910  forms a channel extending from the IC package  902  to a surface of a housing portion  908 . 
         [0088]    The absorbing outfit  910  is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The absorbing outfit  910  can at least partially surround a perimeter of the IC package and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. 
         [0089]    The absorbing outfit  910  forms an absorptive wall around the IC package  902 . In particular, in the example of  FIGS. 9A-B , the absorbing outfit  910  is configured to form an opening for signal passage that is smaller and offset from the absorbing outfit of  FIGS. 8A-8B . For example, absorbing outfit  910  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. In particular, the absorbing outfit  910  can makes a substantially right angle after rising to a specified height above the PCB  904  on one side of the IC package  902 . From the specified height, the absorbing outfit  910  extend over a portion of the IC package  902  such that only a portion is open as a channel to the housing portion  908 . Opposite the overhang, the absorbing outfit  910  forms a wall to the housing portion  908  similar to that shown in  FIG. 8A-B . The open portion can be positioned over a transducer  912  (shown in  FIG. 9B ) of the IC package  902 . In alternative implementations, the overhanging portion can have an angle up toward the housing or down toward the IC package. 
         [0090]    The absorbing outfit  910  can be formed of a similar material to that of absorbing outfit  810  of  FIGS. 8A-8B . The absorbing outfit  910  forms an opening for passage of signals. In some implementations, the edge of the opening formed by the absorbing outfit  910  is straight or may be recessed from the top surface of the absorbing outfit  910 . The recess can be straight, curved, slanted, or a combination. 
         [0091]      FIG. 10A  shows a side view diagram  1000  illustrating a third example absorber signal isolation structure.  FIG. 10B  shows a top view diagram  1001  illustrating the third example absorber signal isolation structure of  FIG. 10A . 
         [0092]    In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0093]    As shown in diagram  1000 , an IC package  1002 , for example a transmitter IC package, is positioned on a PCB  1004 . The IC package  1002  is at least partially encircled by an absorbing outfit  1010 . The absorbing outfit  1010  forms a channel extending from the IC package  1002  to a surface of a housing portion  1008 . 
         [0094]    The absorbing outfit  1010  is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. For example, the absorbing outfit  810  can be shaped to aid in reflecting signal energy and directing signal propagation in a specified direction. The absorbing outfit  1010  can at least partially surround a perimeter of the IC package and extend in the direction of signal transmission and/or reception by a specified “height” relative to the PCB  1004  to provide a channel for emitted or received RF signals. 
         [0095]    In  FIGS. 10A-10B , the absorbing outfit  1010  forms an absorptive wall around the IC package  1002 . In particular, in the example of  FIGS. 10A-B , the absorbing outfit  1010  is slanted such that the thickness of the absorbing outfit  1010  is greater near the PCB  1004  than near the housing portion  1008 . 
         [0096]    The absorbing outfit  1010  is formed from a material that absorbs electromagnetic radiation, particularly radio frequency electromagnetic radiation including EHF RF electromagnetic radiation. For example, the absorbing outfit  1010  can be composed of a silica-ferrite material, e.g., a material formed by mixing small iron pieces with silicon. In some implementations, the material is further selected based on heat tolerance properties. For example, the material can be selected based in part on a melting or deformation point in excess of temperatures generated by device components. The absorbing outfit  1010  can have a thickness configured to optimize the amount of stray signal absorption and may depend on the particular absorbing material used and the proximity to another communication channel. In some other implementations, the absorbing outfit can have other shapes. 
         [0097]    In each of the examples shown in  FIGS. 8-10  above, the absorbing outfit is used without a distinct signal guiding structure and instead can act as both the absorbing outfit and signal guiding structure. However, in some implementations, the absorbing outfit of  FIGS. 8-10  can be used in combination with a respective signal guiding structure that can be similar to the signal guiding structure described above, e.g., with respect to  FIG. 3 . For example, the absorbing outfit can surround an inner signal guiding structure that has a similar shape. When the signal guiding structure is used with the absorbing outfit, the signal guiding structure should not be formed from or coated on an interior surface with a metallic material. 
         [0098]      FIG. 11  shows a side view diagram  1100  illustrating a fourth example absorber signal isolation structure. 
         [0099]    In particular, for ease of illustration a portion of a communication module is shown having a single integrated circuit package and positioned relative to a housing. In operation, the communication module can have one or more integrated circuit packages positioned on a common PCB. The communication module can be positioned within a device relative to a device housing such that signals can pass through the housing. The device can be positioned relative to another device to communicate data, e.g., as illustrated in  FIG. 4 . 
         [0100]    As shown in diagram  1100 , an IC package  1102 , for example a transmitter IC package, is positioned on a PCB  1104 . The IC package  1102  is at least partially encircled by a signal guiding structure  1106 . The signal guiding structure  1106  forms a channel extending from the IC package  1102  to a surface of a housing portion  1108 . The signal guiding structure, e.g., similar to signal guiding structure  306  of  FIG. 3 , is configured to aid in directing radio frequency (RF) signals as well as to reduce interference from spurious signals. The signal guiding structure can at least partially surround a perimeter of the IC package and extend in the direction of signal transmission and/or reception by a specified “height” to provide a channel for emitted or received RF signals. The signal guiding structure can be composed of a suitable material that is configured to reduce extraneous signals without disrupting passage of communications along the channel formed by the signal guiding structure. In particular, the signal guiding structure  1106  should not be metallic. 
         [0101]    An absorbing outfit can be positioned relative to communication units, e.g., an IC package, to absorb signals that might otherwise cause crosstalk to adjacent channels. In some implementations, the absorbing outfit is placed around each IC package on a communication module whether it is a transmitter or a receiver. This, in combination with the signal guiding structure, provides two layers of absorptive materials for absorbing stray signals. 
         [0102]    In  FIG. 11 , an absorbing outfit  1110  forms an absorptive wall around the IC package  1102 . For example, the absorbing outfit  1110  can surround the signal guiding structure  1106 . In particular, the absorbing outfit  1110  can be substantially parallel to the signal guiding structure  1106  and can be affixed to the signal guiding structure  1106  by a suitable affixing structure or adhesive. When viewed from above, the signal guiding structure  1106  and the absorbing outfit  1110  can form concentric squares surrounding the IC package  1102 . The absorbing outfit  1110  can have a thickness configured to optimize the amount of stray signal absorption and may depend on the particular absorbing material used and the proximity to another communication channel. In some alternative implementations, the absorbing outfit is positioned on an inside layer of the signal guiding structure such that the signal guiding structure surrounds the absorbing outfit. 
         [0103]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims. 
         [0104]    While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially be claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
         [0105]    Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
         [0106]    Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.