Patent Publication Number: US-9886066-B2

Title: Mobile wireless communications device including a keyboard assembly for reducing SAR and related methods

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of wireless communications, and, more particularly, to mobile wireless communications devices and related methods. 
     BACKGROUND 
     Mobile wireless communications systems continue to grow in popularity and have become an integral part of both personal and business communications. For example, cellular telephones allow users to place and receive voice calls almost anywhere they travel. Moreover, as cellular telephone technology has increased, so too has the functionality of cellular devices and the different types of devices available to users. For example, many cellular devices now incorporate personal digital assistant (PDA) features such as calendars, address books, task lists, etc. Moreover, such multi-function devices may also allow users to wirelessly send and receive electronic mail (email) messages and access the Internet via a cellular network and/or a wireless local area network (WLAN), for example. 
     Even so, as the functionality of cellular communications devices continues to increase, so too does the demand for smaller devices which are easier and more convenient for users to carry. One challenge this poses for cellular device manufacturers is designing the layout of components for additional functionality and operational stability within the relatively limited amount of space available for the components. 
     Moreover, with the ever increasing trend towards smaller cell phone sizes with increased functionality, for a relatively small phone, it may be increasingly difficult for cellular device manufacturers to comply with certain requirements. For example, for a relatively small phone having an internal antenna, the antenna may be in relatively close proximity to the user&#39;s face or cheek, which may make complying with applicable SAR and/or hearing aid compatibility (HAC) requirements potentially difficult for manufacturers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a mobile wireless communications device including a keyboard assembly in accordance with one exemplary aspect. 
         FIG. 2  is a schematic block diagram of the mobile wireless communications device of  FIG. 1 . 
         FIG. 3  is an exploded perspective view of a portion of the keyboard assembly of  FIG. 1 . 
         FIGS. 4 a -4 b    are greatly enlarged cross-sectional views of a portion of the mask layer of the keyboard assembly of  FIG. 1 . 
         FIG. 5  is a schematic block diagram illustrating additional components that may be included in the mobile wireless communications device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present description is made with reference to the accompanying drawings, in which various example embodiments are shown. However, many different example embodiments may be used, and thus the description should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments. 
     In accordance with an exemplary aspect, a mobile wireless communications device may include a portable housing and wireless transceiver circuitry carried by the portable housing. The mobile wireless communications device may also include an antenna carried by the portable housing and coupled to the wireless transceiver circuitry, and a light source carried by the portable housing, for example. The mobile wireless communications device may further include a keyboard assembly carried by the portable housing. The keyboard assembly may further include a light guide coupled to the light source and having a plurality of input key receiving openings therein, and a mask carried by the light guide and having a plurality of input key receiving openings therein aligned with the plurality of input key receiving openings of the light guide, for example. The keyboard assembly may further include a plurality of input keys within respective input key receiving openings of the light guide and the mask. The mask may include an electrically conductive layer positioned relative to the antenna so as to reduce a Specific Absorption Rate (SAR) value of the mobile wireless communications device. Accordingly, the SAR value may be reduced, and, additionally, HAG compatibility may be increased. 
     The mask may include an opaque dielectric substrate supporting the electrically conductive layer. The electrically conductive layer may only be over a portion of the opaque dielectric substrate, for example. 
     The opaque dielectric substrate may include at least one of paper and plastic. The electrically conductive layer may include at least one of an electrically conductive ink and an electrically conductive paint, for example. 
     The portable housing may include an upper portion and a lower portion. The antenna and the keyboard assembly may each be carried by the lower portion of the portable housing, for example. The mobile wireless communications device may further include a display carried by the upper portion of the portable housing. 
     The input keys may be arranged in horizontal rows, for example, and the keyboard assembly may further include a plurality of spaced apart horizontal trim members between adjacent rows of said input keys. The wireless transceiver circuitry may include an electrical ground, for example, and the electrically conductive layer may be electrically floating with respect to the electrical ground. 
     A method aspect is directed to a method of reducing a Specific Absorption Rate (SAR) value in a mobile wireless communications device that may include a portable housing, wireless transceiver circuitry carried by the portable housing, and an antenna carried by the portable housing and coupled to the wireless transceiver circuitry, for example. The mobile wireless communications device may also include a light source carried by the portable housing, and a keyboard assembly carried by the portable housing and including a light guide coupled to the light source and having a plurality of input key receiving openings therein. The keyboard assembly may also include a mask carried by the light guide and having a plurality of input key receiving openings therein aligned with the plurality of input key receiving openings of the light guide, and a plurality of input keys within respective input key receiving openings of the light guide and the mask. The method may include forming the mask to include an electrically conductive layer relative to the antenna so as to reduce the SAR value of the mobile wireless communications device. 
     Referring initially to  FIGS. 1-3 , a mobile wireless communications device  10  illustratively includes a portable housing  11 . The portable housing  11  includes an upper portion and a lower portion. In some example embodiments, the upper portion may correspond to an upward or skyward direction when being used, while the lower portion may be directed to downward direction, or toward the ground. 
     The mobile wireless communications device  10  also includes wireless transceiver circuitry  16 . The mobile wireless communications device  10  a controller  18  or processor, carried by the portable housing  11 . The wireless transceiver circuitry  16  includes an electrical ground  17 . For example, the wireless transceiver circuitry  16  may be coupled to a ground plane on a PCB, for example. A display  13  is also carried by the upper portion of the portable housing  11 . 
     The mobile wireless communications device  10  also illustratively includes an audio transducer  15  carried by the portable housing  11 . The audio transducer  15  may be a microphone, for example. The audio transducer  15  may also be a speaker. In some example embodiments, there may be more than one audio transducer  15 , for example, a microphone  15   b  and speaker  15   a  may be used and carried by the portable housing, respectively ( FIG. 2 ). 
     The mobile wireless communications device  10  includes a keyboard assembly  30  carried by the lower portion of the portable housing  11 . In some embodiments (not shown), the keyboard assembly  30  may be carried by one or both of the upper and lower portion of the housing  11 . 
     The keyboard assembly  30  includes a plurality input devices or keys  21 . The input keys  21  illustratively are push buttons. The input keys  21  may be alphanumeric keys and are illustratively arranged in horizontal rows. For example, the input keys  21  may correspond to letters and numbers for typing a message, for example, an electronic mail (email) message or short messaging service (SMS) message. A thumb wheel or scroll wheel for navigation, for example, or other type of input device, may also be included, as will be appreciated by those skilled in the art. 
     As will be appreciated by those skilled in the art, the input keys  21  may be for cooperating with the wireless transceiver circuitry  16  and may also correspond to wireless communication functions, for example, for placing or ending a telephone call. Additional input devices may be included outside of the keyboard assembly  30 , and may be carried by another portion of the portable housing  11 . 
     The mobile wireless communications device  10  also includes an antenna  22  carried by the lower portion of the portable housing  11 . The antenna  22  is also coupled to the wireless transceiver circuitry  16 . The antenna  22  may be a cellular antenna, for example, and cooperate with the wireless transceiver circuitry  16 , to provide cellular communications. The antenna  22  may be another type of antenna, for example, a wireless local area network (WLAN) antenna, and may be carried by the upper portion of the portable housing  11 . The antenna  22  may also be carried by both the upper and lower portions of the portable housing  11  in other embodiments. The mobile wireless communications device  10  may include more than one antenna, which may be positioned in one or both of the upper and lower portions of the portable housing  11 . 
     A light source  23  is also carried by the portable housing  11 . The light source  23  may be one or more light emitting diodes (LEDs), for example. The light source  23  may be another type of source, as will be appreciated by those skilled in the art. 
     The mobile wireless communications device  10  also includes a keyboard assembly  30  carried by the portable housing  11 . The keyboard assembly  30  illustratively includes a light guide  32  coupled to the light source  23 . The light guide  32  may be a molded, translucent plastic light guide, for example. Of course, the light guide  32  may be transparent, and may be another material. The light guide  32  also includes input key receiving openings  34  therein. 
     A mask  33  is carried by the light guide  32  and also has input key receiving openings  35  therein aligned with the plurality of input key receiving openings  34  of the light guide  32 . The input keys  21  are positioned within respective input key receiving openings  35 ,  34  of the light guide  32  and the mask  33 , respectively. 
     Referring additionally to  FIGS. 4 a  and 4 b   , the mask  33  includes an electrically conductive layer  36 . The electrically conductive layer  36  may be provided by an electrically conductive ink. The electrically conductive layer  36  may also be provided by an electrically conductive paint. The electrically conductive layer  36  may be another type of conductive material, for example, a conductive metal, as will be appreciated by those skilled in the art. In some example embodiments (not shown), a non-conductive layer of non-conductive ink, paint, or other material may cover the electrically conductive layer  36 . 
     The mask  33  includes an opaque dielectric substrate  37  supporting the electrically conductive layer. The opaque dielectric substrate  37  may be paper, for example, and may be in a sheet form ( FIG. 4 a   ). In another embodiment, the opaque dielectric substrate  37 ′ may be plastic ( FIG. 4 b   ). The opaque dielectric substrate  37  may include other types of materials, as will be appreciated by those skilled in the art, and, in some embodiments, may not be opaque. 
     The electrically conductive layer  36  is illustratively only over a left-hand portion of the opaque dielectric substrate  37 . For example, the electrically conductive layer  36  may be within a perimeter of about 1 cm by 2 cm. Of course, the perimeter of the electrically conductive layer may have other dimensions. For example, in some exemplary embodiments, the electrically conductive layer  36  may be over all of the opaque dielectric substrate  37 , or more than one portion. Covering only a portion of the opaque dielectric substrate  37  may advantageously reduce the SAR value in an area of increased exposure while reducing the effects on antenna operation. 
     Additionally, the electrically conductive layer  36  is electrically floating with respect to the electrical ground  17 . The electrically conductive layer  36  being electrically floating reduces the electromagnetic interference (EMI) shielding from the antenna  22  as will be appreciated by those skilled in the art. 
     The electrically conductive layer  36  is positioned relative to the antenna  22  to advantageously reduce a SAR value of the mobile wireless communications device  10 . For example, the relative positioning of the electrically conductive layer  36  to the antenna  22  may reduce radiation power exposure by 0.5 to 1.0 dB and, thus, reduce SAR for antenna operation in the Personal Communication Service (PCS) frequency band. 
     As will be appreciated by those skilled in the art, SAR values are increasingly an issue for mobile wireless communications devices. For example, regulatory authorities may set maximum SAR values for a mobile wireless communications device. Accordingly, it may be desirable to reduce a SAR value for a mobile wireless communications device. 
     Existing approaches for reducing a SAR value may include adjusting the antenna, both electrically and physically, and changing geometry of the mobile wireless communications device, for example changing the size and shape of the housing. Both antenna adjustment and form factor changing may result in costly design changes that may increase the size of a portable housing, for example. Indeed, the relative positioning of the electrically conductive layer to the antenna  22  advantageously reduces a SAR value of the mobile wireless communications device  10  without changing the geometry of the portable housing, or making adjustments to the antenna, for example. Thus, the SAR value is reduced at a relatively low cost. 
     The keyboard assembly  30  also includes spaced apart horizontal trim members  31 . The spaced apart horizontal trim members  31  are positioned between adjacent rows of the input keys  21 . As will be appreciated by those skilled in the art, the spaced apart horizontal trim members  31  may provide increased rigidity to the keyboard assembly  30 . Additionally, the horizontal trim members  31  may couple the mask  33  to the light guide  32 . 
     A method aspect is directed to a method of reducing a Specific Absorption Rate (SAR) value in a mobile wireless communications device  10  that includes a portable housing  11 , wireless transceiver circuitry  16  carried by the portable housing, and an antenna  22  carried by the portable housing and coupled to the wireless transceiver circuitry, for example. The mobile wireless communications device  10  may includes a light source  23  carried by the portable housing  11 , and a keyboard assembly  30  carried by the portable housing and including a light guide  32  coupled to the light source and having a plurality of input key receiving openings  34  therein. The keyboard assembly  30  also includes a mask  33  carried by the light guide  32  and having a plurality of input key receiving openings  35  therein aligned with the plurality of input key receiving openings  34  of the light guide, and a plurality of input keys  21  within respective input key receiving openings  34 ,  35  of the light guide  32  and the mask  33 . The method may include forming the mask  33  to include an electrically conductive layer  36  relative to the antenna  22  so as to reduce the SAR value of the mobile wireless communications device  10 . 
     Exemplary components that may be used in various embodiments of the above-described mobile wireless communications device are now described with reference to an exemplary mobile wireless communications device  1000  shown in  FIG. 5 . The device  1000  illustratively includes a housing  1200 , a keypad  1400  and an output device  1600 . The output device shown is a display  1600 , which may comprise a full graphic LCD. In some embodiments, display  1600  may comprise a touch-sensitive input and output device. Other types of output devices may alternatively be utilized. A processing device  1800  is contained within the housing  1200  and is coupled between the keypad  1400  and the display  1600 . The processing device  1800  controls the operation of the display  1600 , as well as the overall operation of the mobile device  1000 , in response to actuation of keys on the keypad  1400  by the user. In some embodiments, keypad  1400  may comprise a physical keypad or a virtual keypad (e.g., using a touch-sensitive interface) or both. 
     The housing  1200  may be elongated vertically, or may take on other sizes and shapes (including clamshell housing structures, for example). The keypad  1400  may include a mode selection key, or other hardware or software for switching between text entry and telephony entry. 
     In addition to the processing device  1800 , other parts of the mobile device  1000  are shown schematically in  FIG. 5 . These include a communications subsystem  1001 ; a short-range communications subsystem  1020 ; the keypad  1400  and the display  1600 , along with other input/output devices  1060 ,  1080 ,  1100  and  1120 ; as well as memory devices  1160 ,  1180  and various other device subsystems  1201 . The mobile device  1000  may comprise a two-way RF communications device having voice and data communications capabilities. In addition, the mobile device  1000  may have the capability to communicate with other computer systems via the Internet. 
     Operating system software executed by the processing device  1800  may be stored in a persistent store, such as the flash memory  1160 , but may be stored in other types of memory devices, such as a read only memory (ROM) or similar storage element. In addition, system software, specific device applications, or parts thereof, may be temporarily loaded into a volatile store, such as the random access memory (RAM)  1180 . Communications signals received by the mobile device may also be stored in the RAM  1180 . 
     The processing device  1800 , in addition to its operating system functions, enables execution of software applications or modules  1300 A- 1300 N on the device  1000 , such as software modules for performing various steps or operations. A predetermined set of applications that control basic device operations, such as data and voice communications  1300 A and  1300 B, may be installed on the device  1000  during manufacture. In addition, a personal information manager (PIM) application may be installed during manufacture. The PIM may be capable of organizing and managing data items, such as e-mail, calendar events, voice mails, appointments, and task items. The PIM application may also be capable of sending and receiving data items via a wireless network  1401 . The PIM data items may be seamlessly integrated, synchronized and updated via the wireless network  1401  with the device user&#39;s corresponding data items stored or associated with a host computer system. 
     Communication functions, including data and voice communications, are performed through the communications subsystem  1001 , and possibly through the short-range communications subsystem. The communications subsystem  1001  includes a receiver  1500 , a transmitter  1520 , and one or more antennas  1540  and  1560 . In addition, the communications subsystem  1001  also includes a processing module, such as a digital signal processor (DSP)  1580 , and local oscillators (LOs)  1601 . The specific design and implementation of the communications subsystem  1001  is dependent upon the communications network in which the mobile device  1000  is intended to operate. For example, a mobile device  1000  may include a communications subsystem  1001  designed to operate with the Mobitex™, Data TAC™ or General Packet Radio Service (GPRS) mobile data communications networks, and also designed to operate with any of a variety of voice communications networks, such as AMPS, TDMA, CDMA, WCDMA, PCS, GSM, EDGE, etc. Other types of data and voice networks, both separate and integrated, may also be utilized with the mobile device  1000 . The mobile device  1000  may also be compliant with other communications standards such as GSM, 3G, UMTS, 4G, etc. 
     Network access requirements vary depending upon the type of communication system. For example, in the Mobitex and DataTAC networks, mobile devices are registered on the network using a unique personal identification number or PIN associated with each device. In GPRS networks, however, network access is associated with a subscriber or user of a device. A GPRS device therefore utilizes a subscriber identity module, commonly referred to as a SIM card, in order to operate on a GPRS network. 
     When required network registration or activation procedures have been completed, the mobile device  1000  may send and receive communications signals over the communication network  1401 . Signals received from the communications network  1401  by the antenna  1540  are routed to the receiver  1500 , which provides for signal amplification, frequency down conversion, filtering, channel selection, etc., and may also provide analog to digital conversion. Analog-to-digital conversion of the received signal allows the DSP  1580  to perform more complex communications functions, such as demodulation and decoding. In a similar manner, signals to be transmitted to the network  1401  are processed (e.g. modulated and encoded) by the DSP  1580  and are then provided to the transmitter  1520  for digital to analog conversion, frequency up conversion, filtering, amplification and transmission to the communication network  1401  (or networks) via the antenna  1560 . 
     In addition to processing communications signals, the DSP  1580  provides for control of the receiver  1500  and the transmitter  1520 . For example, gains applied to communications signals in the receiver  1500  and transmitter  1520  may be adaptively controlled through automatic gain control algorithms implemented in the DSP  1580 . 
     In a data communications mode, a received signal, such as a text message or web page download, is processed by the communications subsystem  1001  and is input to the processing device  1800 . The received signal is then further processed by the processing device  1800  for an output to the display  1600 , or alternatively to some other auxiliary I/O device  1060 . A device user may also compose data items, such as e-mail messages, using the keypad  1400  and/or some other auxiliary I/O device  1060 , such as a touchpad, a rocker switch, a thumb-wheel, or some other type of input device. The composed data items may then be transmitted over the communications network  1401  via the communications subsystem  1001 . 
     In a voice communications mode, overall operation of the device is substantially similar to the data communications mode, except that received signals are output to a speaker  1100 , and signals for transmission are generated by a microphone  1120 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on the device  1000 . In addition, the display  1600  may also be utilized in voice communications mode, for example to display the identity of a calling party, the duration of a voice call, or other voice call related information. 
     The short-range communications subsystem enables communication between the mobile device  1000  and other proximate systems or devices, which need not necessarily be similar devices. For example, the short-range communications subsystem may include an infrared device and associated circuits and components, or a Bluetooth™ communications module to provide for communication with similarly-enabled systems and devices. 
     Many modifications and other embodiments will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the disclosure is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included.