Abstract:
A space-efficient cellular modem device for machine-to-machine communications that includes: a multi-layer printed circuit board defining a top side and a bottom side and including a first circuit layer adjacent the top side, a second circuit layer adjacent the bottom side, a ground plane layer, and a power plane layer, the ground and power plane layers located between the first and second circuit layers; a cellular transceiver module configured to communicate over a cellular wireless cellular network; electrical power-management components attached to the multi-layer printed circuit board, the power-management components in electrical communication with the cellular transceiver module; first and second rows of pins in electrical communication with the cellular transceiver; and a communications port.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Application No. 61/936,651 filed Feb. 6, 2014, which is incorporated herein in its entirety by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is generally directed to embedded wireless modems. More specifically, the present invention is directed to improved, space-efficient embedded cellular modems for machine-to-machine communication. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wireless modems, and in particular, cellular modems, may be embedded in remotely-located machines such as meters, automatic teller machines (ATMs), temperature monitors, and so on, to enable wireless communication between the remotely-located “machine” and another “machine”, such as a computer server. Such machine-to-machine (M2M) communications facilitate remote monitoring of devices, including data collection, in a number of applications and industries, including agriculture, security, oil and gas, property management, and so on. 
         [0004]    While the use of embedded cellular modems in such M2M applications is generally known, presently-used modems remain relatively expensive, typically require a large footprint and may not be designed to be integrated with the latest standards of technology. 
       SUMMARY OF THE INVENTION 
       [0005]    Embodiments of the invention comprise various space-efficient, embedded cellular modems for use in M2M applications. In an embodiment, cellular modems of the invention include a cellular transceiver module, U.FL antenna port, power management electronics, level shifter electronics, and an interface, all in an XBee® form factor. The embedded cellular modem may be configured to operate on a CDMA, GSM, or other cellular network. 
         [0006]    Embedded cellular modems of the invention add robust cellular connectivity to M2M devices, and in the case of pre-certified modems, avoid the cost, delay and hassle of obtaining federal and carrier certifications. In an embodiment, modems of the invention comply with the XBee interface standard, optimized for 1xRTT, or other cellular networks, thereby minimizing costs of hardware and network access. 
         [0007]    Other embodiments of the invention include embedded cellular modem kits which include an embedded cellular modem, baseboard, antenna, communications cable, and power supply. 
         [0008]    An embodiment comprises a space-efficient cellular modem device for machine-to-machine communications that includes: a multi-layer printed circuit board defining a top side and a bottom side and including a first circuit layer adjacent the top side, a second circuit layer adjacent the bottom side, a ground plane layer, and a power plane layer, the ground and power plane layers located between the first and second circuit layers; a cellular transceiver module configured to communicate over a cellular wireless cellular network, the cellular transceiver module comprising a processor and attached to a top side of the multi-layer printed circuit board; electrical power-management components attached to the multi-layer printed circuit board, the power-management components in electrical communication with the cellular transceiver module; a first plurality of electrically-conductive pins in electrical connection with the cellular transceiver module and aligned along a first pin axis to form a first row of pins, each of the first plurality of pins extending outwardly and away from the bottom side of the multi-layer printed circuit board; a second plurality of electrically-conductive pins in electrical connection with the cellular transceiver module and aligned along a second pin axis to form a second row of pins, each of the second plurality of pins extending outwardly and away from the bottom side of the multi-layer printed circuit board a communications port, the second row of pins located opposite the first row of pins; and a communications port in electrical communication with the cellular transceiver module, the communications port configured to receive and transmit communication signals over the cellular wireless network. 
         [0009]    Another embodiment comprises a space-efficient cellular modem device for machine-to-machine communications that includes: a multi-layer printed circuit board defining a top side and a bottom side and including a circuit layer, a ground plane layer and a power plane layer, the top side of the multi-layer printed circuit board defining a top-side surface area; a cellular transceiver module configured to communicate over a cellular wireless cellular network, the cellular transceiver module comprising a housing defining a top-side surface area and attached to a top side of the multi-layer printed circuit board, the top-side surface area of the cellular transceiver module being in a range of 50% to 100% of the top-side surface area of the multi-layer printed circuit board; electrical power-management components attached to the multi-layer printed circuit board, the power-management components in electrical communication with the cellular transceiver module; a first row of electrically-conductive pins in electrical connection with the cellular transceiver module, each of the pins extending outwardly and away from the bottom side of the multi-layer printed circuit board; a second row of electrically-conductive pins in electrical connection with the cellular transceiver module, each of the pins extending outwardly and away from the bottom side of the multi-layer printed circuit board; an antenna port in electrical communication with the cellular transceiver module, the communications port configured to receive and transmit communication signals over the cellular wireless network. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]    The invention can be understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
           [0011]      FIG. 1  depicts an embodiment of an embedded cellular modem, according to an embodiment of the invention; 
           [0012]      FIG. 2  depicts a block diagram of the embedded cellular modem of  FIG. 1 ; 
           [0013]      FIGS. 3   a  and  3   b  depict a circuit diagram of the embedded cellular modem of  FIGS. 1 and 2 ; 
           [0014]      FIG. 4  depicts pin connectors and receiver of the embedded cellular modem of  FIG. 1 ; 
           [0015]      FIG. 5  depicts a base board compatible with the embedded cellular modem of  FIG. 1 ; 
           [0016]      FIG. 6  depicts a multi-layer PC board assembly of the embedded cellular modem of  FIG. 1 ; 
           [0017]      FIG. 7  depicts a CDMA EV-DO enabled embodiment of an embedded cellular modem, according to an embodiment of the invention; 
           [0018]      FIG. 8  depicts a PC board with connector locations of the embedded cellular modem of  FIG. 7 ; 
           [0019]      FIG. 9  depicts a GSM enabled embodiment of an embedded cellular modem, according to an embodiment of the invention; 
           [0020]      FIG. 10  depicts a PC board with connector locations of the embedded cellular modem of  FIG. 9 ; 
           [0021]      FIGS. 11   a - 11   g  depict various view of the embedded cellular modem of  FIG. 1 ; 
           [0022]      FIGS. 12   a - g  depict various views of the embedded cellular modem of  FIG. 7 ; 
           [0023]      FIGS. 13   a - g  depict various views of the embedded cellular modem of  FIG. 9 ; 
           [0024]      FIG. 14  depicts a development kit, according to an embodiment of the invention; and 
           [0025]      FIGS. 15-19  depict electrical schematics of the development kit of  FIG. 14 . 
       
    
    
       [0026]    While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0027]    Referring to  FIGS. 1-3   b , an embodiment of an embedded cellular modem  100  is depicted. In an embodiment, cellular modem  100  includes printed-circuit (PC) board  102 , cellular transceiver module  104 , communication port  106 , which may comprise an antenna port  106 , power management and level shifter electronics  108 , pin connectors  110  and interface  112 . 
         [0028]    As will be described further below, in an embodiment, PC board  102  may comprise a multi-layer board having multiple sub-boards electrically connected by inter-board vias. 
         [0029]    In an embodiment cellular transceiver module  104  comprises a cellular transceiver configured to communicate over a cellular network, such as a CDMA network, including 1xRTT and EVDO networks, GSM networks, including GPRS, UMTS, HSPA+ and other cellular networks. In other embodiments, module  104  may communicate non-cellular RF networks. 
         [0030]    In a specific embodiment, cellular transceiver module  104  comprises a Telit CE910-Dual 1xRTT communications module; in other embodiments, cellular transceiver module  104  comprises a Telit DE 910 Dual module, GE910 Quad, and LE  910  for CDMA EV-DO networks, GSM networks, and LTE networks, respectively. In an embodiment, cellular transceiver module  104  comprises a processor. 
         [0031]    In an embodiment, antenna port  106  may comprise a U.FL antenna port configured to interface with a micro antenna cable. Although a single antenna port is depicted in  FIG. 1 , additional antenna ports  106  may be present, as described further below. In an embodiment, antenna port  106  may comprise an antenna port other than a U.FL antenna port. The use of micro-coaxial cables and antenna ports facilitates universal antenna options off-the-module. 
         [0032]    Power management and level shifter electronics  108  are located on PC board  102  and are described in further detail in  FIGS. 3   a  and  3   b , an electrical schematic of embedded cellular modem  100 . 
         [0033]    Embodiments of embedded cellular modem  100  may be configured for use in CDMA 1XRTT. 
         [0034]    Referring also to  FIG. 4 , pin connectors  110 , as depicted, may comprise two 10-pin connectors,  110   a  and  110   b , having a 2 mm pitch, so as to comprise an XBee form factor. The ten pin connectors are configured to fit into corresponding female receptacles, such as receptacles R, depicted. In an embodiment, and as depicted, pin connectors  110  may comprise surface mount pins. 
         [0035]    Referring also to  FIG. 5 , pin connectors  110  may be electrically connected, such as by soldering, to base PC board  116 . In an embodiment, PC board  116  defines an envelope dimension of 33.60 mm×29.00 mm, with pin connections distributed about PC board  102  as depicted. 
         [0036]    Referring to  FIG. 6 , the compact, space-efficient embedded cellular modem  100  achieves the XBee form factor by utilizing a multi-layer PC board. In an embodiment, PC board  102  comprises a multi-layer PC board including a silkscreened and solder-masked top side, a first layer (Layer 1) comprising a circuit top side, a second layer (Layer 2) comprising a ground plane, a third layer (Layer 3) comprising a power plane, a fourth layer (Layer 4) comprising a circuit bottom side, and finally, a silkscreened/solder-masked bottom side. 
         [0037]    In an embodiment, and as depicted, PC board  102  as assembled defines a height of only 0.062 in+/−0.007 in. 
         [0038]    Such a multi-layer, or 4-layer in this embodiment, allows for efficient spacing of surface-mounted components, connectors, and interfaces for the XBee form factor. 
         [0039]    Referring to  FIG. 7 , an embodiment of embedded cellular modem  100  configured to operate on a CDMA EV-DO network is depicted in a block diagram. In this embodiment, modem  100  includes a transceiver  104  that is configured for the EV-DO network, which in an embodiment comprises a Telit module DE910-DUAL. Further, this embodiment includes a pair of antenna ports  106 . In an embodiment, three antenna ports  106 , two of which are located at a top side of PC board  102 , and one at a bottom side of PC board  102 . 
         [0040]      FIG. 8  is a mechanical drawing of PC board  102  of an EV-DO modem  100  showing locations of connectors. Such a drawing may be used to assist a designer in knowing where to align mating connectors on their baseboard as well as physical routing of RF cables inside their end product. 
         [0041]    Referring to  FIG. 9 , an embodiment of embedded cellular modem  100  configured to operate on a GPRS network is depicted in a block diagram. In this particular embodiment, modem  100  includes a micro-SIM slot  120 . In an embodiment, micro-SIM slot  120  may be on a bottom side of PC board  120 . 
         [0042]      FIG. 10  is a mechanical drawing of PC board  102  of a GSM-GPRS modem  100  showing locations of connectors. Such a drawing may be used to assist a designer in knowing where to align mating connectors on their baseboard as well as physical routing of RF cables inside their end product. 
         [0043]    Embodiments of embedded cellular modems configured for a CDMA network are depicted in  FIGS. 11   a  to  11   g ; embodiments of embedded cellular modems configured for a CDMA EV-DO network are depicted in  FIGS. 12   a  to  12   g ; and embodiments of embedded cellular modems configured for a GSM GPRS network are depicted in  FIGS. 13   a  to  13   g.    
         [0044]    Embodiments of the invention may also comprise an LTE-capable modem  100 . 
         [0045]    As is evident from the above-described figures, embodiments of the invention provide a number of unique features and benefits. The space-efficient size of embedded cellular modem  100  is enabled by the use of surface mount connectors to meet XBee pinout requirements while freeing up surface area on a topside of the modem and its PC board. The use of solder-masked vias support high-volume manufacturing of small geometry board features under BGA components. Further, the use of a micro-SIM card slot on an XBee-sized board provides unique advantages over known modems. 
         [0046]    PCB panel design using a combination of scored edges and routered edges supports low cost, high volume PCB manufacturing and subsequent module assembly. Further, the multi-layer stackup approach not only minimizes size and cost, but also maximizes RF performance, such as minimizing signal loss and improving RX sensitivity. 
         [0047]    GPS and GLONASS positioning support in an XBee-sized board is also unique, as is the ability to support antenna diversity in an XBee form factor. 
         [0048]    In addition to the advantages offered by embodiments of embedded cellular modem  100  as described above, embodiments of the invention also include a cellular modem kit. 
         [0049]    Referring to  FIG. 14 , a block diagram of an assembled development kit is depicted. In an embodiment, the kit includes cellular modem  100  with debugging headers, power management electronics supplied by a power source (depicted as a 12V source). Other components include a USB Mini-B connected to modem  100 , another USB Mini-B interfacing with a MUX via a UART to USB interface, an universal CPU connection, and an Arduino Shield interface. 
         [0050]    Details of the block diagram are further depicted and described in the schematic diagrams of  FIGS. 15-19 . 
         [0051]    Embodiments of the invention also include algorithms for sending SMS messages using embedded cellular modem  100 . 
         [0052]    The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. In addition, although aspects of the present invention have been described with reference to particular embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention, as defined by the claims. 
         [0053]    Persons of ordinary skill in the relevant arts will recognize that the invention may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the invention may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the invention may comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. 
         [0054]    Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
         [0055]    For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section  112 , sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.