Abstract:
An apparatus for powering a wireless peripheral includes a controller and a power management circuit. The controller is configured to determine the strength of wireless signals received by the peripheral. The power management circuit selectively powers the peripheral with either an external power source or a combination of the external power source and an internal power source included in the wireless peripheral. If the wireless signal strength is weak, the power management circuit uses both the internal an external sources to power the peripheral. This allows the wireless peripheral to boost its transmit power, even though its power requirement may exceed that available from the external source. If the wireless signal strength is strong, the power management circuit uses only the external source to power the peripheral. When this occurs the internal power source may also be simultaneously charged by the external power source.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to computer peripherals, and more particularly, to power management techniques for wireless peripherals. 
       BACKGROUND 
       [0002]    Peripherals attach to computers and other electronic devices to add functionality. Wireless modems are an example of one type of peripheral. An external wireless modem can be connected to a computer or other device using a standard data bus, such as a Universal Serial Bus. A wireless modem allows a computer to wirelessly communicate with a communications system, such as a cellular system. During operation of the modem, the modem transmits and receives wireless signals to and from the communications system. In some instances, the communications system requests that the modem increase the transmit power of its signals. The modem can increase the transmit power up to a maximum transmit power. 
         [0003]    Some peripherals, including some wireless modems, are powered by a power supply located in the device to which the modem is connected. However, it is frequently the case that these external power supplies are insufficient for the peripheral. For example, with a wireless modem, increasing the transmit power of the modem increases the current draw of the modem. As a result, the increased transmit power can cause the modem&#39;s current draw to exceed the maximum current available from the external power supply in the attached device. 
         [0004]    To overcome this problem, some wireless modems include internal batteries to handle their extra power needs. However, in these modems, the internal battery must be separately charged, which typically requires an additional power adapter and cable. Other solutions, such as ganging host device ports connected to the peripheral to supply additional power, are not available in all circumstances. 
         [0005]    Thus, there is a need for a wireless peripheral that offers a more elegant solution the power limitations often faced by peripheral devices. 
       SUMMARY 
       [0006]    In accordance with an exemplary embodiment of the invention, an apparatus for powering a wireless peripheral includes a controller and a power management circuit. The controller is configured to determine the strength of wireless signals received by the peripheral. The power management circuit selectively powers the peripheral with either an external power source or a combination of the external power source and an internal power source included in the wireless peripheral. If the wireless signal strength is weak, the power management circuit uses both the internal an external sources to power the peripheral. This allows the wireless peripheral to boost its transmit power, even though its power requirement may exceed that available from the external source. If the wireless signal strength is strong, the power management circuit uses only the external source to power the peripheral. When this occurs the internal power source may also be simultaneously charged by the external power source. 
         [0007]    Other aspects, features, advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional aspects, features, and advantages be included within this description and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    It is to be understood that the drawings are solely for purpose of illustration and do not define the limits of the invention. Furthermore, the components in the figures are not necessarily to scale. In the figures, like reference numerals designate corresponding parts throughout the different views. 
           [0009]      FIG. 1  illustrates an exemplary computer system configured to transmit and receive wireless signals in a communications system. The computer system includes a wireless modem connected to a computer such that the computer provides power to the modem. 
           [0010]      FIG. 2  illustrates another exemplary computer system configured to transmit and receive wireless signals in a communications system. The computer system includes a wireless modem having an alternative architecture to the wireless modem of  FIG. 1 . 
           [0011]      FIG. 3  is a flowchart illustrating a method of powering the wireless modems of  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The following detailed description, which references to and incorporates the drawings, describes and illustrates one or more specific embodiments of the invention. These embodiments, offered not to limit but only to exemplify and teach the invention, are shown and described in sufficient detail to enable those skilled in the art to practice the invention. Thus, where appropriate to avoid obscuring the invention, the description may omit certain information known to those of skill in the art. 
         [0013]      FIG. 1  illustrates a computer  104  in wireless communication with a base station  106  of a wireless communications system  100 . To effect wireless communications, the computer  104  is attached to a wireless modem peripheral  102  by way of a wired data bus  117 . 
         [0014]    The modem  102  enables the computer  104  to wirelessly communicate through the wireless communications system  100  over a wireless air-link. Examples of suitable wireless communications systems  100  include, but are not limited to, code-division multiple access (CDMA) based networks. 
         [0015]    The modem  102  is configured to be detachably connected to the computer  104 . When the modem  102  is connected to the computer  104 , a power source  108  in the computer  104  provides power to the modem  102  (supplied power) by way of the data bus  117 . The externally supplied power powers the operation of electronics in the modem  102 . The electronics employ the supplied power to transmit wireless signals in the communications system  100 . The modem  102  can vary the transmit power of the signals up to a maximum transmit power. Increasing the transmit power draws more current from the power source  108 . 
         [0016]    The modem includes at least one antenna  110 , an air interface with radio frequency (RF) transceiver  114  having a transmitter (not shown) and a receiver (not shown), a controller  114 , a power management circuit  116 , a bus interface (Int)  115 , and an internal power source such as a battery  118 . 
         [0017]    The bus interface  115  permits the wireless modem  102  to communicate with and receive power from the computer  104 . It also allows the wireless modem  102  to be detachably connected to the computer  104 . The computer  104  includes a corresponding bus interface (Int)  109  having port or a slot configured to detachably receive the data bus  117 . Suitable bus interfaces include, but are not limited to, the Universal Serial Bus (UBS), Personal Computer Memory Card International Association (PCMCIA cards or PC cards), Express Cards, Miniature Cards (Mini Cards), and Express Mini Cards or Mini Express Cards. 
         [0018]    The controller  114  includes a processor  120  and a memory  122 . A suitable processor  120  may include, but is not limited to, a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions attributed to the controller  114 , bus interface  115 , processor  120  and/or power management circuit  116 . A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor  120  may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
         [0019]    The memory  122  is in communication with the processor  120 . The memory  122  can store data for communicating with the communications system  100  and computer  104 . For instance, signal strength and current thresholds can be stored in the memory  122 . The memory  38  can be any memory device or combination of memory devices suitable for read/write operations. The memory  122  can also store an operating system and one or more firmware/software programs having instructions to be executed by the processor  120  to carry out the operational functions of the wireless modem  102 . 
         [0020]    The transceiver  112  and controller  114  are preferably implemented using an off-the-shelf mobile station modem (MSM) chipset. 
         [0021]    The power management circuit  116  includes a load sensing circuit  124  and a charging circuit  126 . The power management circuit  116  may be any suitable combination of hardware and/or software components for supplying power to the modem  102 . Preferably, the power management circuit  116  is a commercially-available power management IC (integrated circuit) having a digital communications interface for communicating with the controller  114 . The power management circuit  116  is configured to selectively supply power from the modem battery  118 , an external source such as the computer power source  108 , or a combination of the battery  118  and the power source  108  at the direction of the controller  114 . The power management circuit  116  is connectable to the computer power source  108  through the bus interface  115 . 
         [0022]    The load sensing circuit  124  includes an ammeter or its equivalent for monitoring the amount current being supplied to the modem  102  by power management circuit  116 . The load sensing circuit  124  is configured to present modem current readings to the controller  114  upon receiving a request signal from the controller  114  to do so. The load sensing circuit  124  may include any suitable combination of hardware and/or software components for providing the above functions. 
         [0023]    The charging circuit  126  includes a battery charger circuit and circuitry for activating and deactivating the battery charger circuit upon request from the controller  114 . The battery charger circuit receives input power from the computer power source  108  through the bus interface  115  when the modem is connected to the computer  104 . It then selectively supplies power to the modem battery  118  to recharge it during certain operational states of the modem  102 , for example, as discussed below in connection with  FIG. 2 . Alternatively or additionally, the battery charger circuit can include a connector for connecting to separate input power supply source, such as an AC wall adapter. Suitable charging circuits are well known by those of ordinary skill in the art. 
         [0024]    The battery  118  is a rechargeable battery, such as NiMH, Lithium-ion, NiCad battery, lead acid or the like. 
         [0025]    The computer  104  includes, among other things, a wired bus interface  109  for communicating with the modem  102  and a power source  108 , such as a power supply or battery. The power source  108  is external to the wireless modem  102 . If the power source  108  is a battery, it can be a rechargeable battery, such as NiMH, Lithium-ion, NiCad battery, lead acid or the like. The computer  104  can be any suitable computing device, including a laptop computer, notebook computer, but can also be another type of computer, such as a desktop, game system, office equipment, home appliance or the like. 
         [0026]    The power source  108  is an external power source that provides power to electronics in the wireless modem  102  through the data bus  117 . For instance, wireless modem  102  may operate at about 5 V or 3.3 V. In some instances, the power source  108  provides power to the wireless modem  102  at about 5 V or at about 3.3 V. 
         [0027]    The transceiver  112  is in communication with the antenna  110 . The controller  114  is in communication with the transceiver  112 . The controller  114  can employ the transceiver  112  to wirelessly transmit signals to the communications system  100  and to wirelessly receive signals from the communications system  100 . 
         [0028]    During operation of the modem  102 , the modem  102  communicates with the communications system  100 . Communication with the communications system  100  can include the modem  102  transmitting signals to the communications system  100  and receiving signals from the communications system  100 . During communication with the communications system  100 , the communications system  100  may determine that the signals transmitted by the modem  102  are undesirably weak. In response, the communications system  100  sends the modem  102  a signal requesting that the modem  102  increase the transmit power for the signals transmitted from the modem  102 . The transmit power is the signal power at the output of the antenna  110  and is typically measured in units such as dBm or watts. 
         [0029]      FIG. 2  illustrates another exemplary communication system  150  that includes a wireless modem  102  having an alternative internal architecture to that illustrated in  FIG. 1 . In this modem architecture, the wireless modem  102  is a peripheral that includes a wireless modem card  152  that is detachably connected to an adapter  154 . The adapter  154  is detachably connected to the computer  104  using data bus  117 . In this configuration, the computer power source  108  supplies power to the modem card  152  through the adapter  154 . 
         [0030]    The modem card  152  is preferably a PCI Express type card having CDMA wireless modem capabilities and additionally functionality as described herein. However, other suitable modem card configurations include, but are not limited to, Personal Computer Memory Card International Association (PCMCIA cards or PC cards) having wireless modem capabilities, Miniature Cards (Mini Cards) having wireless modem capabilities, and Express Mini Cards or Mini Express Cards having wireless modem capabilities. 
         [0031]    The modem card  152  includes a connector interface (Int)  156  that permits the modem card  152  to be detachably connected to a connector interface (Int)  158  in the adapter  154 . For instance, a PCI Express Card typically employs a 26-contact beam on blade connector. The adapter  154  can include a port or a slot configured to receive all or a portion of the modem card  152 . The connector interface  158  can be positioned in the port or slot such that the connector on the modem card  152  is connectable with the connector on the adapter  154 . 
         [0032]    The adapter  154  is preferably an external peripheral that connects to the computer  104  using a USB port. 
         [0033]    The controller  114  in the modem card  152  and the power management circuit  116  communication with each other using the USB lines included in the PCI Express bus. 
         [0034]      FIG. 3  is a flowchart  200  illustrating a method of powering the wireless modem  102 . In step  202 , the modem  102  is initially powered by the computer power supply  108  by way of the data bus  117 . In this initial state, the modem&#39;s transmit power is set such that the power requirement of the modem  102  does not exceed that available from the computer power source  108 . 
         [0035]    In step  204 , the controller  114  determines the strength of the CDMA signal. This can be done by monitoring the pilot signal emitted from the base station  106  using well known techniques. For example, the wireless modem  102  may perform a channel estimation by determining the strength of the pilot signal using a conventional network parameter, such as the carrier-to-interference ratio (C/I). Other techniques for determining signal strength may be used. 
         [0036]    If the CDMA signal is above a predefined signal strength threshold, the controller  114  signals the power management circuit  116  to activate the charging circuit  126  to begin charging the modem battery  118 , if necessary (step  206 ), using current drawn from the computer power source  108  over the data bus  117 . The charging circuit  126  is configured to determine the charged state of the battery  118  and whether battery re-charging is necessary. In this state, the modem  102  is also supplied power by only the computer power source  108  (step  208 ) over the data bus  117 . 
         [0037]    If the CDMA signal is below the signal strength threshold, the modem  102  waits to receive a request from the base station  106  to increase the modem&#39;s transmit (Tx) power (step  212 ). The weak CDMA signal is typically the result of the modem  102  being located in a poor coverage area. With CDMA, the base station  106  can transmit the request over a control channel using known protocols and techniques. 
         [0038]    Upon receiving the request for a stronger transmit signal, the controller  114  boosts the modem&#39;s transmit power and signals the load sensing circuit  124  to determine the modem&#39;s current draw. The modem&#39;s current draw varies directly with its transmit power: as the transmit power increase, so does the current required by the modem  102 . 
         [0039]    If the modem&#39;s current draw exceeds a predefined current threshold, the controller  114  deactivates the charging circuit  126  (step  214 ) and signals the power management circuit  116  to power the modem  102  using both the modem battery  118  and the computer power source  108  (step  216 ). To do this, the power management circuit  116  essentially connects the modem battery  118  in parallel with the power supply line(s) of the bus interface  115 . The power management circuit  116  may include circuitry to ensure compatibility of the modem battery  118  and the computer power source  108 , e.g., voltage leveler, reverse current protection, and the like. 
         [0040]    The current threshold is set to a value that is not greater than the maximum current limit available from the computer power source  108  over the data bus  117 . Preferably, the current threshold is slightly less than maximum output current of the data bus  117 . 
         [0041]    If the modem&#39;s current draw is below the current threshold, the controller  114  signals the power management circuit  116  to activate the charging circuit  126  to begin charging the modem battery  118 , if necessary (step  206 ). The modem  102  is also supplied power by only the computer power source  108  (step  208 ). 
         [0042]    All or a portion of the method described above can be executed by the modem electronics. In some instances, the electronics include a computer-readable medium and instructions for executing all or a portion of the methods disclosed above are included on the computer-readable medium. The processor  120  can execute these instructions during operation of the modem  102 . 
         [0043]    Other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined with reference to the appended claims along with their full scope of equivalents.