Patent Publication Number: US-8116689-B2

Title: Determination of antenna noise temperature for handheld wireless devices

Description:
This application is a continuation of Ser. No. 12/412,899 filed Mar. 27, 2009 now U.S. Pat. No. 7,894,775 issued Feb. 22, 2011, which, in turn, is a continuation of Ser. No. 11/173,093 filed Jul. 1, 2005 now U.S. Pat. No. 7,519,329 issued Apr. 14, 2009, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of communications devices, and, more particularly, to mobile wireless communications devices and related methods. 
     BACKGROUND OF THE INVENTION 
     Cellular communications systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular phones allow users to place and receive voice calls most anywhere they travel. Cellular phones and other handheld wireless communication devices typically include a radio, e.g. having a wireless transceiver and associated circuitry connected thereto, and an antenna connected to the radio. 
     Antenna noise temperature has been discussed in many books and papers, such as John D. Kraus and Ronald J. Marhefka, “Antennas: For all Applications”, McGraw Hill, 2002, ch. 12; Constantine A. Balanis, “Antenna Theory: Analysis and Design” John Wiley &amp; Sons Inc. 1997, ch. 2; David M. Pozar, “Microwave Engineering”, Addison-Wesley Publishing Company, 1993, ch. 12; J. Dijk, MJeuken and E. J. Maanders, “Antenna noise temperature”, Proc. IEEE, Vol. 115, No. 10, October 1968, pp 1403-1409; and Warren L. Flock and Ernest K. Smith, “Natural Radio Noise—a Mini-Review”, IEEE Trans. on AP Vol. Ap-32, No. 7, July 1984 pp 762-767. 
     The definitions for antenna noise temperature are mainly given based on remote sensing and satellite receiving applications, where antennas are generally physically away or well shielded from radio receivers and high gain antennas are used to capture weak signals. In this case the total noise at the terminal of the receiver antenna is mainly contributed from thermal noise and background noise. In contrast, a wireless handheld antenna is physically very close to its receiver so that the printed circuit board and accessories operate as a part of the antenna. This makes the noise contributions to the handheld wireless device antenna different from the noise contributions to antennas for remote sensing and satellite receiving applications. 
     This difference makes the standard antenna temperature definition inadequate for explaining the receiver behavior of handheld wireless devices in a noisy environment. A wireless handheld device generally operates in an ever changing noise environment, and the handheld antenna radiation pattern is generally a broad beam antenna pattern. Furthermore, human physical interface and device usage scenarios change constantly in the practical application. For these reasons, antenna noise temperature is constantly changing in the practical sense. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a handheld wireless communication device for use with the method of the present invention. 
         FIG. 2  is a flowchart illustrating steps of the method in accordance with an embodiment of the present invention. 
         FIG. 3  is a schematic block diagram illustrating the various work stations to implement the method of  FIG. 2 . 
         FIG. 4  is a schematic block diagram showing basic functional circuit components that can be used in the mobile wireless communications device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     In view of the foregoing background, it is therefore an object of the present invention to provide a method of accurately determining the antenna noise temperature for a handheld wireless communication device. 
     A determination or definition of antenna noise temperature is presented herein. Radio noise temperature is introduced to explain the radio receiver behavior under a complex noise environment for handheld wireless devices. The noise sources and their coupling mechanisms are also discussed. A method of determining receive sensitivity including determining an antenna radiation pattern and independently determining a thermal noise temperature is also provided. 
     These and other objects, features, and advantages in accordance with the present invention are provided by a method of determining an antenna noise temperature for a handheld wireless communication device including a radio, e.g. having a wireless transceiver and associated circuitry connected thereto, and an antenna connected to the radio. The method includes measuring an antenna thermal noise component; measuring a radio noise component; measuring an environmental background noise component; and determining the antenna noise temperature based upon the measured antenna thermal noise, radio noise, and environmental background noise components. 
     The method may include measuring antenna efficiency, and determining may further include weighting at least one of the measured antenna thermal noise, radio noise and environmental background noise components based upon the measured antenna efficiency. 
     The antenna noise temperature T t  may be defined as
 
 T   t   =ηT   A +(1−2η) T   P   +ηT   R  
 
where η is measured antenna efficiency, T A  is the environmental background noise component, T P  is the antenna thermal noise component, and T R  is the radio noise component.
 
     The antenna thermal noise component may be based upon a measured conductive sensitivity which is based upon a minimum detectable signal-to-noise ratio and a minimum input signal level when the antenna is replaced by a signal generator. The antenna thermal noise component T P  may be defined as 
               T   P     =       P     sig   ,   min         F   ·     SNR     out   ,   min       ·   k   ·   B             
where SNR out.min  is the minimum detectable signal-to-noise ratio, P sig.min  is the minimum input signal level, k is Boltzman&#39;s constant, B is the channel bandwidth and F is a device noise figure which is defined as a ratio of the input signal-to-noise ratio and the output signal-to-noise ratio (SNR in /SNR out ).
 
     The radio noise component may be based upon a measured radiated sensitivity of the communication device in an anechoic chamber at room temperature. The radio noise component T R  may be defined as 
               T   R     =         P     sig   ,   min         F   ·     SNR     out   ,   min       ·   k   ·   B   ·   η       -         (     1   -   η     )     ⁢     T   P       η             
where SNR out.min  is the minimum detectable signal-to-noise ratio, P sig.min  is the minimum input signal level, k is Boltzman&#39;s constant, B is the channel bandwidth, F is a device noise figure which is defined as a ratio of the input signal-to-noise ratio and the output signal-to-noise ratio (SNR in /SNR out ), η is measured antenna efficiency, and T P  is the antenna thermal noise component.
 
     The environmental background noise component may be based upon measured radiated sensitivity of the communication device in an operating environment including a plurality of noise sources. The environmental background noise component T A  may be defined as 
               T   A     =         P     sig   ,   min         F   ·     SNR     out   ,   min       ·   k   ·   B   ·   η       -         (     1   -     2   ⁢   η       )     ⁢     T   P       η     -     T   R             
where SNR out.min  is the minimum detectable signal-to-noise ratio, P sig.min  is the minimum input signal level, k is Boltzman&#39;s constant, B is the channel bandwidth, F is a device noise figure which is defined as a ratio of the input signal-to-noise ratio and the output signal-to-noise ratio (SNR in /SNR out ), η is measured antenna efficiency, T P  is the antenna thermal noise component, and T R  is the radio noise component.
 
     Objects, features, and advantages in accordance with the present invention are also provided by a method for determining receive sensitivity for a wireless handheld device including an antenna and a radio connected thereto. Again, the radio preferably includes a wireless transceiver and associated circuitry connected thereto. The method may include determining an antenna radiation pattern; and independently determining a thermal noise temperature by measuring an antenna thermal noise component, measuring a radio noise component, measuring an environmental background noise component, and determining the antenna noise temperature based upon the measured antenna thermal noise, radio noise, and environmental background noise components. The receive sensitivity may be determined based upon antenna radiation pattern and the thermal noise temperature. 
     Referring now to  FIG. 1 , an example of a mobile wireless communications device  20 , such as a handheld portable cellular radio, which can be used with the present invention is first described. This device  20  illustratively includes a housing  21  having an upper portion  46  and a lower portion  47 , and a dielectric substrate (i.e., circuit board)  67 , such as a conventional printed circuit board (PCB) substrate, for example, carried by the housing. A housing cover (not shown in detail) would typically cover the front portion of the housing. The illustrated housing  21  is a static housing, for example, as opposed to a flip or sliding housing which are used in many cellular telephones. However, these and other housing configurations may also be used. 
     Circuitry  48  is carried by the circuit board  67 , such as a microprocessor, memory, one or more wireless transceivers (e.g., cellular, WLAN, etc.), which includes RF circuitry, including audio and power circuitry, including any keyboard circuitry. It should be understood that keyboard circuitry could be on a separate keyboard, etc., as will be appreciated by those skilled in the art. A rechargeable battery (not shown) is also preferably carried by the housing  21  for supplying power to the circuitry  48 . The term RF circuitry could encompass the cooperating RF transceiver circuitry, power circuitry and audio circuitry. 
     Furthermore, an audio output transducer  49  (e.g., a speaker) is carried by an upper portion  46  of the housing  21  and connected to the circuitry  48 . One or more user input interface devices, such as a keypad, is also preferably carried by the housing  21  and connected to the circuitry  48 . The term keypad as used herein also refers to the term keyboard, indicating the user input devices having lettered and/or numbered keys commonly known and other embodiments, including multi-top or predictive entry modes. Other examples of user input interface devices include a scroll wheel, a back button, a stylus or touch screen interface. The device  20  would typically include a display (not shown), for example, a liquid crystal display (LCD) carried by the housing  21  and connected to the circuitry  48 . 
     An antenna  45  is illustratively positioned at the lower portion  47  in the housing and can be formed as a pattern of conductive traces that make an antenna circuit, which physically forms the antenna. It is connected to the circuitry  48  on the main circuit board  67 . In one non-limiting example, the antenna could be formed on an antenna circuit board section that extends from the circuit board at the lower portion of the housing. By placing the antenna  45  adjacent the lower portion  47  of the housing  21 , the distance is advantageously increased between the antenna and the user&#39;s head when the phone is in use to aid in complying with applicable SAR requirements. Also, a separate keyboard circuit board could be used. 
     More particularly, a user will typically hold the upper portion  46  of the housing  21  very close to his head so that the audio output transducer  49  is directly next to his ear. Yet, the lower portion  47  of the housing  21  where an audio input transducer (i.e., microphone) is located need not be placed directly next to a user&#39;s mouth, and can be held away from the user&#39;s mouth. That is, holding the audio input transducer close to the user&#39;s mouth may not only be uncomfortable for the user, but it may also distort the user&#39;s voice in some circumstances. 
     Another important benefit of placing the antenna  45  adjacent the lower portion  47  of the housing  21  is that this may allow for less impact on antenna performance due to blockage by a user&#39;s hand. That is, users typically hold cellular phones toward the middle to upper portion of the phone housing, and are therefore more likely to put their hands over such an antenna than they are an antenna mounted adjacent the lower portion  47  of the housing  21 . Accordingly, more reliable performance may be achieved from placing the antenna  45  adjacent the lower portion  47  of the housing  21 . 
     Still another benefit of this configuration is that it provides more room for one or more auxiliary input/output (I/O) devices  50  to be carried at the upper portion  46  of the housing. Furthermore, by separating the antenna  45  from the auxiliary I/O device(s)  50 , this may allow for reduced interference therebetween. 
     Some examples of auxiliary I/O devices  50  include a WLAN (e.g., Bluetooth, IEEE 802.11) antenna for providing WLAN communication capabilities, and/or a satellite positioning system (e.g., GPS, Galileo, etc.) antenna for providing position location capabilities, as will be appreciated by those skilled in the art. Other examples of auxiliary I/O devices  50  include a second audio output transducer (e.g., a speaker for speaker phone operation), and a camera lens for providing digital camera capabilities, an electrical device connector (e.g., USB, headphone, secure digital (SD) or memory card, etc.). 
     It should be noted that the term “input/output” as used herein for the auxiliary I/O device(s)  50  means that such devices may have input and/or output capabilities, and they need not provide both in all embodiments. That is, devices such as camera lenses may only receive an optical input, for example, while a headphone jack may only provide an audio output. 
     Accordingly, the mobile wireless communications device  20  as described may advantageously be used not only as a traditional cellular phone, but it may also be conveniently used for sending and/or receiving data over a cellular or other network, such as Internet and email data, for example. Of course, other keypad configurations may also be used in other embodiments. Multi-tap or predictive entry modes may be used for typing e-mails, etc. as will be appreciated by those skilled in the art. 
     The antenna  45  may be formed as a multi-frequency band antenna, which provides enhanced transmission and reception characteristics over multiple operating frequencies. More particularly, the antenna  45  may provide high gain, desired impedance matching, and meet applicable SAR requirements over a relatively wide bandwidth and multiple cellular frequency bands. By way of example, the antenna  45  may operate over five bands, namely a 850 MHz Global System for Mobile Communications (GSM) band, a 900 MHz GSM band, a DCS band, a PCS band, and a WCDMA band (i.e., up to about 2100 MHz), although it may be used for other bands/frequencies as well. To conserve space, the antenna  45  may advantageously be implemented in three dimensions although it may be implemented in two-dimensional or planar embodiments as well. 
     Referring now to  FIGS. 2 and 3 , a method and processing system for determining an antenna noise temperature for a handheld wireless communication device  20  will be described. As discussed above, the handheld device  20  includes a radio, e.g. having a wireless transceiver and associated circuitry  48  connected thereto, and an antenna  45  connected to the radio. The method begins at block  100  ( FIG. 2 ) and includes measuring an antenna thermal noise component (Block  102 ), measuring a radio noise component (Block  104 ), measuring an environmental background noise component (Block  106 ), and, at Block  112 , determining the antenna noise temperature based upon the measured antenna thermal noise, radio noise, and environmental background noise components. Preferably, the method includes measuring antenna efficiency (Block  108 ), and weighting at least one of the measured antenna thermal noise, radio noise and environmental background noise components based upon the measured antenna efficiency (Block  110 ). 
     As will be described in greater detail below, the antenna thermal noise component may be based upon a measured conductive sensitivity which is a ratio of the minimum detectable signal-to-noise ratio and a minimum input signal level when the antenna is replaced by a signal generator. The radio noise component may be based upon a measured radiated sensitivity of the communication device  20  in an anechoic chamber at room temperature, and the environmental background noise component may be based upon measured radiated sensitivity of the communication device  20  in an operating environment including a plurality of noise sources. 
     More specifically, for antenna noise temperature determination, one of the quantities by which one can define the overall performance of a radio receiver system is the signal-to-noise ratio. For a radio receiver system, the system noise figure F is defined as input signal-to-noise ratio over output signal-to-noise ratio. It follows that 
                     F   =       SNR   in     /     SNR   out         ⁢     
     ⁢   where           (   1   )                 SNR   in     =       P   sig       P   n               (   2   )               
P sig =the input signal power per unit bandwidth,
 
P n =the input noise power per unit bandwidth,
 
SNR in =the input signal to noise ratio, and
 
SNR out =the output signal to noise ratio.
 
     Since the overall signal power and noise power are distributed across the channel bandwidth, B, the total mean square power P sigt  and P nt  can be obtained by integrating over the bandwidth. Thus for the total power in a channel, we have
 
 P   sigt   =P   nt   ·F·SNR   out   (3)
 
This equation also predicts the radio sensitivity as output signal to noise ratio reaches its threshold.
 
     Noise energy as a function of frequency for an ideal black body is given by Planck&#39;s radiation law and the Rayleigh-Jeans approximation, which holds reasonably well at microwave frequencies. Assuming conjugate match at the receiver input and for a noise flat channel, we have
 
 P   nt   =kT   t   B   (4)
 
where T t =the total temperature in degrees Kelvin (K) and k=1380×10 −23  J/° K (Boltzman&#39;s constant).
 
     For the handheld wireless receiver, P nt  is the total antenna noise power at the antenna terminal. T t  is the antenna temperature. There are various noise sources for the handheld radio receiver, and it may be desirable that the individual noise be separable. Due to the antenna aperture size and application requirement, the handheld antenna generally has a broad beam radiation pattern. It is more efficient and convenient to classify the handheld noise types based on the measurable quantities. Accordingly, the handheld antenna noise temperature is classified into three types. 
     The first type of noise is the antenna thermal noise. Antenna thermal noise is caused by the random thermally excited vibration of the charge carriers in the antenna conductor. This carrier motion is similar to the Brownian motion of particles. In every conductor or resistor at a temperature above absolute zero, the electrons are in random motion, and its vibration is dependent on temperature. The available noise power can be in the same equation form as (4) and it is
 
 P   P   =kT   P   B   (5)
 
where T P =the thermal or physical temperature.
 
     The antenna thermal noise is practically achievable in a system operating at room temperature. It may not be possible to achieve any lower noise unless the temperature of the receiver antenna is lowered. So it is also referred to as the “noise floor”. The thermal noise determines the minimum sensitivity of a radio receiver. Thermal noise is not antenna efficiency dependent. 
     The second type of the noise is man-made environmental noises and background noises. The man-made environment noise refers to the intentional or unintentional man-made noise other than the radio noise of its own. The man-made environmental noises include electrical and electronics noise, such as fluorescent lights, ignitions, radio transmitters, computers etc. The man-made environmental noise is generally greater than a wavelength away from the radio receiver of the handheld device. The background noise here refers to the natural noise including natural noise at the earth&#39;s surface, atmospheric noises and extraterrestrial noises. Man-made environmental and background noises couple to the antenna through electromagnetic radiation. Due to the broad beam pattern of the antenna, it is difficult to separate the noise sources. This type of noise is antenna radiation pattern and antenna efficiency dependent. 
     The third type of noise is radio noise of its own, which includes radio processor noise, liquid crystal display (LCD) noise and keyboard noise, etc. A handheld wireless device antenna is generally very close to the radio (much less than a wavelength). The radio noise can couple to the receiver antenna through near-field electrical and near-field magnetic fields. A handheld device antenna may use radio PCB or accessories as part of the antenna. Thus, noise can couple to the radio through a conducted path. The conducted path is due to the antenna having shared impedance with the radio receiver. The near-field electrical and near-field magnetic coupling is due to the loop or dipole kind of noise emission from radio getting picked up by the nearby handheld antenna. The coupling efficiency of this type of noise is also antenna efficiency and antenna type related. The better the antenna efficiency the more of third type of noise gets coupled to the receiver. 
     Thus, from the above described noise contribution, the total equivalent antenna noise temperature is determined to be the weighted average of the three types of noise temperature,
 
 T   t   =ηT   A +(1−2η) T   P   +ηT   R   (6)
 
where η=antenna efficiency, T R =the radio noise temperature, and T A =the environmental background noise temperature.
 
     The environmental background temperature received at all angles can be expressed as follows 
                     T   A     =         ∫   0     2   ⁢   π       ⁢       ∫   0   π     ⁢         T   B     ⁡     (     θ   ,   ϕ     )       ⁢     G   ⁡     (     θ   ,   ϕ     )       ⁢   sin   ⁢           ⁢   θ   ⁢     ⅆ   θ     ⁢     ⅆ   ϕ               ∫   0     2   ⁢   π       ⁢       ∫   0   π     ⁢       G   ⁡     (     θ   ,   ϕ     )       ⁢   sin   ⁢           ⁢   θ   ⁢     ⅆ   θ     ⁢     ⅆ   ϕ                     (   7   )               
where T B (θ,φ)=the distribution of the environmental temperature over all angles about the antenna, and G(θ,φ)=the power gain pattern of the antenna.
 
     It is desirable that the three types of temperature be measurable. The measurement of the temperature is not only important in understanding the radio noise characteristics, but also a very effective tool for radio design and trouble shooting. The measurement and calculation procedure is described below with each type of the noise temperature being separately identified. 
     A thermal temperature measurement is measured by disconnecting the antenna, and connecting a signal generator at the antenna terminal. To the radio receiver it is like it has a matching resistor connected thereto. In this case, antenna efficiency is zero, from the equation (6) it can be seen that the noise temperature that the receiver is detecting is thermal temperature T P . For the handheld radio this process is called conductive measurement and the thermal temperature is equal to 
                     T   P     =       P     sig   ,   min         F   ·     SNR     out   ,   min       ·   k   ·   B               (   8   )               
where SNR out.min =the minimum detectable signal-to-noise ratio, and P sig.min =the minimum input signal level, i.e. radio sensitivity.
 
     For antenna efficiency measurement, a handheld device antenna is generally small in size, and in a controlled environment the receive antenna efficiency η can be measured. The receive antenna efficiency may be measured in any one of the known methods, as would be appreciated by those skilled in the art. 
     The radio temperature measurement is performed by placing the radio in an anechoic chamber at room temperature T P , so from equation (7) we have
 
 T   A   =T   P   (9)
 
Then a radiated sensitivity for the receiver can be determined. In other words, the radio&#39;s sensitivity is measured with the antenna connected. Then the radio temperature can be calculated from the measured radiated sensitivity
 
     
       
         
           
             
               
                 
                   
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     The environmental and background temperature measurement proceeds after thermal and radio temperature have been measured. The man-made environmental and background temperature can be measured by placing the radio in a working environment, then measuring the radio&#39;s radiated sensitivity, such that 
     
       
         
           
             
               
                 
                   
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     In the measurement process, the order of the thermal temperature measurement and antenna efficiency measurement is interchangeable, but they both should be measured before the radio temperature measurement. 
     It is noted that in a handheld radio receiver system the noise from the ground and the surroundings of the antenna including ignition noise, electrical and electronics noise are the dominant noise source of environmental temperature. The distribution function is a function of the specific environment and time. Since a handheld wireless antenna may have a broad beam antenna and, in use, the handheld orientation is also constantly changing, the power gain pattern is also changing with respect to noise source distribution. In this condition, the environmental temperature is changing all the time. An average antenna temperature measurement is a more appropriate approach. 
     Another factor that affects the antenna temperature in a real world application is that the antenna efficiency changes with human physical interface. For example, when the wireless handheld is in the talking position, it will have a few dB antenna average gain degradation compared to the stand alone position in free space. In this case the antenna temperature is generally lower than the stand alone position in free space. 
     So, the definition of antenna temperature determination for handheld wireless devices is general. For the remote sensing and satellite application, the radio noise temperature is negligible, then equation (6) may become
 
 T   t   =ηT   A +(1−η) T   P   (12)
 
which is the same as the equation (3).
 
     The results of the antenna temperature determination illustrate that different radio noise sources have different coupling mechanisms. The radio noise of its own is proportional to the antenna efficiency, but has no direct relationship with the antenna radiation pattern. Accordingly, with the antenna temperature determination of the present invention, handheld sensitivity and antenna pattern can be measured separately. The antenna temperature measurement according to the present invention can be used in the design and trouble shooting of handheld radios. It can also be an important factor for other radio parameter measurements such as total isotropic sensitivity (TIS) measurement. 
     Referring to  FIG. 3 , a system  200  for implementing the above method, will now be described. The system  200  may include an antenna thermal noise test station  202 , for example, to implement the step of disconnecting the antenna and connecting a signal generator at the antenna terminal, to determine the antenna thermal temperature as described above. A radio noise test station  204 , such as an anechoic chamber, is included to determine the radio noise component, and a background/environmental noise test station  206 , such as an operating environment or simulated operating environment, is included to determine the background/environmental noise, as described above. As illustrated in the example, a calculation station  210  may determine the antenna noise temperature based upon the measured components and in view of the antenna efficiency which may be measured at the antenna efficiency test station  208 . Furthermore, the receive sensitivity of the handheld device  20  may be determined based upon independent determination of the antenna radiation pattern, e.g. at the antenna pattern test station  212 , and the antenna noise temperature in accordance with the above described method. 
     An example of a handheld mobile wireless communications device  1000  that may be used in accordance the present invention is further described with reference to  FIG. 4 . The device  1000  includes a housing  1200 , a keyboard  1400  and an output device  1600 . The output device shown is a display  1600 , which is preferably a full graphic LCD. Other types of output devices may alternatively be utilized. A processing device  1800  is contained within the housing  1200  and is coupled between the keyboard  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 keyboard  1400  by the user. 
     The housing  1200  may be elongated vertically, or may take on other sizes and shapes (including clamshell housing structures). The keyboard 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. 4 . These include a communications subsystem  1001 ; a short-range communications subsystem  1020 ; the keyboard  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  is preferably a two-way RF communications device having voice and data communications capabilities. In addition, the mobile device  1000  preferably has the capability to communicate with other computer systems via the Internet. 
     Operating system software executed by the processing device  1800  is preferably 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  1300 A- 1300 N on the device  1000 . 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 is preferably capable of organizing and managing data items, such as e-mail, calendar events, voice mails, appointments, and task items. The PIM application is also preferably capable of sending and receiving data items via a wireless network  1401 . Preferably, the PIM data items are 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 . The antenna system can be designed so that when one antenna is covered by a hand, performance of one or more other antennas, including antenna gain and match, may not be degraded. 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, PCS, GSM, etc. Other types of data and voice networks, both separate and integrated, may also be utilized with the mobile device  1000 . 
     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 requires 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 keyboard  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 of the invention 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 invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.