Abstract:
A system and method for transmitting an information signal through a radio-frequency opaque barrier are disclosed. A transmitter is positioned on a first side of the barrier and a re-transmitter is positioned on a second side of the barrier. The transmitter includes a controller that modulates a received information signal with a carrier signal and forwards the modulated information signal to a vibration generator which converts the received electrical signal to a corresponding vibration signal. The re-transmitter includes an accelerometer that detects vibration signals and produces a corresponding electrical signal and a controller coupled to the accelerometer which receives the electrical signal from the accelerometer and demodulates the information signal included within the electrical signal received from the accelerometer. The transmitter may also include a vibration energy harvester which converts separate vibration signals received from the re-transmitter to energy that charges an energy storage device that powers the transmitter.

Description:
FIELD 
       [0001]    This disclosure relates generally to a system and method for data retransmission through radio-frequency (RF) opaque barriers. 
       BACKGROUND 
       [0002]    It is difficult to transmit RF information into or out of many types of metal or carbon fiber enclosures (or partial enclosures), such as a fuel tank (e.g., a complete enclosure) or an aircraft wheel well (e.g., a partial enclosure), because such the metal or carbon fiber wall forming such enclosure may act as a Faraday cage to block the transmission of RF signals into or out of that enclosure. In many cases, however, it is necessary to place an information source such as a sensor within such an enclosure, e.g., a sensor for measuring the amount of fuel remaining within a fuel tank. Although wires may be provided through an aperture in the metal or carbon fiber wall forming the enclosure, such apertures may provide a pathway for contamination or leakage and long runs may be needed for the wiring for each sensor. Furthermore, many common methods of transmitting data in low power and low data rate applications make use of the 2.4 to 2.4835 GHz frequency band (e.g., signals using the ZigBee protocol according to IEEE Standard 802.15.4). Signals transmitted in this frequency band have a wavelength of nearly five inches, which means that any metal or carbon fiber wall having openings which are only less than five inches in diameter will be RF opaque and prevent such type of signals from passing through such enclosure. 
         [0003]    In addition, given the nature of such enclosures, which may be a fully-encased enclosure like a fuel tank or a partially-encased enclosure like an aircraft wheel well, power may be available on only one side of such enclosure. In the case of a fuel tank, for example, power wiring may be available or desired only on the outside the fuel tank. In the case of an aircraft wheel well, power wiring may be available or desired only within the wheel well. Since, as discussed above, it is preferable that no aperture be used through the metal or carbon fiber wall forming such an enclosure, power would thus be available only for a transmitter on one side of the wall but not a re-transmitter on the other side of the wall (or vice versa). 
         [0004]    Accordingly, there is a need for a system and method of data transmission and/or retransmission which overcomes the problems recited above. 
       SUMMARY 
       [0005]    In a first aspect, a system for transmitting a first information signal through a radio-frequency opaque barrier is disclosed. The system includes a transmitter positioned on a first side of and in close proximity to the radio-frequency opaque barrier. The transmitter includes a vibration generator that converts an electrical signal received on an input to a corresponding vibration signal. The transmitter also includes a controller that is coupled to the input of the vibration generator and which receives a first information signal, modulates the first information signal with a first carrier signal to produce a modulated first information signal, and forwards the modulated first information signal to the input of the vibration generator. The system also include a re-transmitter positioned on a second side of and in close proximity to the radio-frequency opaque barrier. The second side of the radio-frequency opaque barrier is opposite the first side thereof. The re-transmitter includes an accelerometer that detects vibration signals and produces an electrical signal on an output corresponding to the detected vibration signals. The re-transmitter also includes a controller that is coupled to the output of the accelerometer and which receives the electrical signal from the output of the accelerometer and demodulates the first information signal included within the electrical signal received from the output of the accelerometer. 
         [0006]    In a second aspect, a method for transmitting a first information signal through a radio-frequency opaque barrier is disclosed. A first information signal is modulated with a first carrier signal to produce a modulated first information signal in a first device positioned on a first side of and in close proximity to the radio-frequency opaque barrier. The modulated first information signal is converted to a corresponding first vibration signal in the first device. The first vibration signal is detected in a second device positioned on a second side of and in close proximity to the radio-frequency opaque barrier to produce a detected first vibration signal. The second side of the radio-frequency opaque barrier is opposite the first side thereof. The detected first vibration signal is converted to a first electrical signal in the second device. Finally, the first information signal included within the first electrical signal is demodulated in the second device. 
         [0007]    In a third aspect, a system for transmitting energy through a radio-frequency opaque barrier is disclosed. The system includes a first device positioned on a first side of and in close proximity to the radio-frequency opaque barrier. The first device includes a vibration generator that converts an electrical signal received on an input to a corresponding vibration signal. The first device also includes a controller that is coupled to the input of the vibration generator and which forwards a predetermined signal to the input of the vibration generator. The system also include a second device positioned on a second side of and in close proximity to the radio-frequency opaque barrier. The second side of the radio-frequency opaque barrier is opposite the first side thereof The second device includes a vibration energy harvester device that generates an electrical signal on an output corresponding to detected vibration signals. The second device also includes an energy storage device coupled to the output of the vibration energy harvester device which is charged by the electrical signal received from the output of the vibration energy harvester device and supplies electrical power for the second device. 
         [0008]    In a fourth aspect, a method for transmitting energy through a radio-frequency opaque barrier is disclosed. A predetermined electrical signal is converted to a corresponding vibration signal in a first device positioned on a first side of and in close proximity to the radio-frequency opaque barrier. The vibration signal is detected in a second device to produce a detected vibration signal and the detected vibration signal is converted to a corresponding electrical signal. The second device is positioned on a second side of and in close proximity to the radio-frequency opaque barrier. The second side of the radio-frequency opaque barrier is opposite the first side thereof. An energy storage device in the second device is charged using the corresponding electrical signal converted from the detected vibration signal. 
         [0009]    The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The following detailed description, given by way of example and not intended to limit the present disclosure solely thereto, will best be understood in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  is an illustration of a first embodiment of an energy scavenging data transmission system of the present disclosure; 
           [0012]      FIG. 2  is a flowchart of a method of operation of the first embodiment of the energy scavenging data transmission system of the present disclosure; 
           [0013]      FIG. 3  is an illustration of a second embodiment of an energy scavenging data transmission system of the present disclosure; and 
           [0014]      FIG. 4  is a flowchart of a method of operation of the second embodiment of the energy scavenging data transmission system of the present disclosure. 
       
    
    
       [0015]    Each figure shown in this disclosure shows a variation of an aspect of the embodiments presented, and only differences will be discussed in detail. 
       DETAILED DESCRIPTION 
       [0016]    In the present disclosure, like reference numbers refer to like elements throughout the drawings, which illustrate various exemplary embodiments of the present disclosure. 
         [0017]    Referring now to  FIG. 1 , a first embodiment of an energy scavenging data transmission system  100  of the present disclosure is shown for use when power is available outside an enclosure  105  but not within such enclosure  105 . In particular, an information source  110  is positioned within an enclosure  105  having an outer wall formed from a material which acts as a barrier to prevent any RF signals from passing through such outer wall into or out of enclosure  105 . Information source  110  may be a sensor or any other type of source that provides information to be transmitted and may provide any type of output signal (e.g., analog or digital) to transmitter  112  via a link  111 . The outer wall of enclosure  105  is formed from metal, carbon fiber or any other type of material which is opaque to RF signals. The data transmission system  100  of the present disclosure uses a paired transmitter  112  and re-transmitter  120  to forward information signals from information source  110  to a higher-level control system for further processing or usage while at the same time providing a source of power for transmitter  112 . The information signals are converted from electrical energy to vibratory energy that can be transmitted through the outer wall of enclosure  105  from transmitter  112  to re-transmitter  120  when transmitter  112  and re-transmitter  120  are positioned on opposite sides of the outer wall of enclosure  105  but in close proximity to each other such that a vibration transmitted through the outer wall of enclosure  105  by one of transmitter  112  and re-transmitter  120  can be effectively sensed and acted upon by the other of transmitter  112  and re-transmitter  120 . 
         [0018]    Re-transmitter  120  is coupled to (and powered by) a power source  130  which is available outside of enclosure  105  but, due to the nature of enclosure  105  but which cannot be coupled into enclosure  105 . Re-transmitter  120  includes a controller  123  that is coupled to a vibration generator  121  and to an accelerometer  122 . Controller  123  is configured to generate a carrier signal that is supplied to vibration generator  121 . Vibration generator  121  generates a vibratory signal  140  based on the carrier signal received from controller  123  which vibratory signal  140  is applied to the adjacent wall of enclosure  105 . In a further embodiment where information signals are to be transmitted to transmitter  112  and/or information source  110 , controller  123  may modulate such information signals with the carrier signal and provide the modulated signal to vibration generator  121 . In this latter case, the vibratory signal  140  applied to the wall of enclosure  105  is based on the modulated signal. Accelerometer  122  is configured to detect a separate vibratory signal  141  (discussed below) and to convert such vibratory signal  141  into an electrical signal that is provided to controller  123 . Controller  123 , in turn, is configured to receive the converted electrical signal, to demodulate information signals included therein from the base carrier signal, and to forward the demodulated information signals to a higher level control system for further processing or usage. As one of ordinary skill in the art will readily recognize, re-transmitter  120  may forward the demodulated information signals wirelessly, via antenna  124 , or alternatively via a wired interface (not shown in  FIG. 1 ). The conversion of an electrical signal to a vibratory signal applied to one side of the wall of enclosure  105  permits such signals to be detected by on an opposite side of the wall of enclosure  105 , even when such wall is formed from a material which blocks RF signals (i.e., formed from an RF opaque material). 
         [0019]    Transmitter  112  includes a controller  115  that is coupled to a vibration generator  114  and to an accelerometer  113 . Transmitter  112  also includes a vibration energy harvester device  117  that is coupled to an energy storage device  116  (e.g., a battery or a capacitor) and is configured to detect vibratory signal  140  (generated on an opposite side of the wall forming enclosure  105  by re-transmitter  120 ) and to convert such vibratory signal  141  into an electrical signal that is used to charge the energy storage device  116 . Vibration energy harvester device  117  may convert vibrations to electrical energy using one or more of the following technologies: piezoelectric, electromagnetic, electrostatic (capacitive), and magnetostrictive. Energy storage device  116  is configured to provide all the power necessary to operate transmitter  112  and may also be used to power information source  110  in some cases. Accelerometer  113  is only necessary in the further embodiment where information signals are transmitted from re-transmitter  120  to transmitter  112 . Accelerometer  113  is configured to detect vibratory signal  140  and to convert such vibratory signal  140  into an electrical signal that is provided to controller  115 . Controller  115 , in the further embodiment, is configured to monitor the converted vibratory signal, to demodulate any information signals included therein from the base carrier signal, and, in some cases, to forward such demodulated information signals to information source  110 . The demodulated information signals may consist of configuration information for transmitter  112  and/or configuration information for information source  110 . Controller  115  is also configured to receive an information signals from information source  110 , to modulate such information signals with a carrier signal, and to forward the modulated information signals to vibration generator  114 . In the event that transmitter  112  receives analog signals from information source  110 , controller  115  is also configured to convert such analog signals to digital form as well. Vibration generator  114  converts the modulated information signals from an electrical signal to the vibratory signal  141  that is processed and forwarded by re-transmitter  120  on the opposite side of the wall forming enclosure  105 . 
         [0020]    Referring now to  FIG. 2 , flowchart  200  shows the operation of system  100  in  FIG. 1 . In particular, at step  205 , a first vibratory signal (e.g., signal  140  in  FIG. 1 ) is generated outside of the enclosure by vibration generator  121 . As discussed above, the first vibratory signal may consist of a carrier signal alone or in a further embodiment may consist of a carrier signal modulated with information signals. Next, at step  210 , the first vibratory signal is detected inside the enclosure by vibration energy harvester device  117  and converted, at step  215 , to an electrical signal. This converted vibratory signal, now in electrical form, is next coupled, at step  220 , to charge an energy storage device (thereby storing the energy converted from vibratory form to electrical form). The energy storage device  116  in  FIG. 1  is used to power transmitter  112 . As discussed above, accelerometer  113  may convert the first vibratory signal into an electrical signal provided controller  115  and, if any information signals were previously modulated with the carrier signal in the vibratory signal, controller  115  may then demodulate such information signals for further processing. At step  225 , controller  115  receives information signals from information source  110 , and modulates such information signals with a carrier signal. The modulated signal created by controller  115  is then provided, at step  230 , to vibration generator  114  to generate a second vibratory signal (e.g., vibratory signal  141  in  FIG. 1 ) inside enclosure  105 . The second vibratory signal is detected, at step  235 , outside of enclosure  105  by accelerometer  122  in re-transmitter  120  and converted to an electrical signal. At step  240 , controller  123  demodulates the information signals included within the converted second vibratory signal. Finally, at step  245 , controller  123  forwards the demodulated information signals for further processing, e.g., via antenna  124  in  FIG. 1 . In this manner, information signals such as sensor data may be transmitted from a transmitter  112  inside an enclosure  105  through a wall of such enclosure to re-transmitter  120  outside enclosure  105  without requiring any aperture in such wall. Furthermore, since transmitter  112  uses the vibratory signals  140  to charge an internal energy storage device  116  which powers transmitter  112 , transmitter  112  may transmit such information signals to re-transmitter  120  even though no local source of power is available to be directly wired to transmitter  112 . 
         [0021]    Referring now to  FIG. 3 , a second embodiment of an energy scavenging data transmission system  300  of the present disclosure is shown for use when power is available within an enclosure  305  but not immediately outside enclosure  305 . In particular, an information source  310  is positioned within enclosure  305  having an outer wall formed from a material which acts as a barrier to prevent any RF signals from passing through such outer wall into or out of enclosure  305 . Information source  310  may be a sensor or any other type of source that provides information to be transmitted and may provide any type of signals (e.g., analog or digital) to transmitter  312 . The outer wall of enclosure  305  is formed from metal, carbon fiber or any other type of material which is opaque to RF signals. The data transmission system  300  of the present disclosure uses a paired transmitter  312  and re-transmitter  320  to forward information signals from information source  310  to a higher-level control system for further processing or usage while at the same time providing a source of power for re-transmitter  320 . As with the first embodiment shown in  FIG. 1 , transmitter  312  is preferably positioned in close proximity to re-transmitter  320 , but with transmitter  312  and re-transmitter  320  on opposite sides of the wall of enclosure  305 . 
         [0022]    Transmitter  312  is mounted inside of enclosure  305  and is coupled to (and powered by) a power source  330  which is available inside of enclosure  305 . However, due to the nature of enclosure  305 , power source  330  cannot be coupled to the point available immediately outside of enclosure  305  where re-transmitter  320  is mounted outside of the wall forming enclosure  305 . Transmitter  312  includes a controller  315  that is coupled to a vibration generator  314  and may also be coupled to an accelerometer  322  in a further embodiment which allows information signals to be transferred from re-transmitter  320  to transmitter  312 . In this further embodiment, accelerometer  313  is configured to detect a vibratory signal  340  (discussed below) and to convert such signal  340  into an electrical signal. Controller  315  receives the converted vibratory signal and demodulates the information signals included therein from a base carrier signal, and, if necessary, to forward such demodulated information signals to information source  310 . The demodulated information signals may consist of configuration information for transmitter  312  and/or for information source  310 . Controller  315  also receives information signals from information source  310 , modulates such information signals with a carrier signal, and forwards the modulated information signals to vibration generator  314 . In the event that transmitter  312  receives the information signals from information source  310  in analog form, controller  315  also to converts such analog signals to digital form as well. Vibration generator  314  converts the modulated information signals from an electrical signal to vibratory signal  341  that is applied to the inner wall of enclosure  305 . 
         [0023]    Re-transmitter  320  includes a controller  323  which is coupled to an accelerometer  322  and, in the further embodiment discussed above, to a vibration generator  321 . Re-transmitter  320  also includes a vibration energy harvester device  326  which is coupled to an energy storage device  325  and is configured to detect the vibratory signal  341  (discussed above) and to convert such vibratory signal  341  into an electrical signal that is used to charge energy storage device  325 . Vibration energy harvester device  117  may convert vibrations to electrical energy using one or more of the following technologies: piezoelectric, electromagnetic, electrostatic (capacitive), and magnetostrictive. Energy storage device  325  provides all the power necessary to operate re-transmitter  320 . Accelerometer  322  is configured to detect vibratory signal  341  and to convert such vibratory signal  341  to an electrical signal that is provided to controller  323 . Controller  323  is configured to receive the electrical signal output by accelerometer  322  and demodulate the information signals included within that signal from the base carrier signal, and to forward the demodulated information signals to a higher level control system for further processing or usage. As with system  100  in  FIG. 1 , re-transmitter  320  may forward the demodulated information signals wirelessly, via antenna  324 , or via a wired interface, (not shown in  FIG. 3 ). By converting the electrical signals from controller  315  inside enclosure to vibratory signals  341  permits such signals to be detected outside of the outer wall of enclosure  305 , even when such wall is formed from a material such as metal or carbon fiber which blocks RF signals. In addition, by using the converted vibratory signals output by vibration energy harvester device  326  to charge energy storage device  325 , re-transmitter  320  is able to operate in areas where there is no wired source of electrical power. 
         [0024]    Referring now to  FIG. 4 , flowchart  400  shows the operation of system  300  in  FIG. 3 . First, at step  410 , a first vibratory signal (e.g., signal  340  in  FIG. 3 ) may be generated outside of the enclosure by vibration generator  321  consisting of a carrier signal modulated with first information signals. As discussed above, this step is only necessary in the further embodiment where information is to be transmitted to transmitter  312  for use by transmitter  312  and/or by information source  310  (e.g., configuration information). Next, at step  420 , the first vibratory signal may be detected inside the enclosure by accelerometer  313  and then converted to an electrical signal. This converted vibratory signal, now in electrical form, next by be demodulated by controller  315  at step  430  for further processing. Steps  420  and  430  are also optional and only necessary in the further embodiment. At step  440 , controller  315  receives information signals from information source  310 , and modulates such information signals with a carrier signal. The modulated signal created by controller  315  is then provided, at step  450 , to vibration generator  314  to generate a second vibratory signal (e.g., vibratory signal  341  in  FIG. 3 ) inside enclosure  305 . The second vibratory signal is detected, at step  460  and outside of enclosure  305 , by accelerometer  322  in re-transmitter  320  and converted to an electrical signal. The second vibratory signal is also detected by vibration energy harvester device  326  and converted to an electrical signal. At step  470 , controller  323  demodulates the information signals included within the converted second vibratory signal and forwards such information signals for further processing, e.g., via antenna  324  in  FIG. 3 . Finally, at step  480 , the electrical signal from vibration energy harvester device  326  is applied to charge energy storage device  325 . In this manner, information signals such as sensor data may be transmitted from inside an enclosure  305  through a wall of such enclosure to re-transmitter  320  outside enclosure  305  without requiring any aperture in such wall. Furthermore, since re-transmitter  320  uses the vibratory signals  341  to charge an internal energy storage device  325  which powers transmitter  320 , re-transmitter  320  may receive and forward such information signals even though no local source of power is available to be directly wired to re-transmitter  320 . 
         [0025]    In the systems shown in  FIGS. 1 and 3 , an accelerometer generates an electrical signal based on detected vibratory signals which is used to decode information signals, while a separate vibration energy harvester converts the same vibratory signals to electrical signals used to charge an energy storage device such as a battery or capacitor. In some cases, depending on the type of vibration energy harvester device employed, it may be possible to omit the separate accelerometer and use the output of the vibration energy harvester both as a signal applied to the controller to decode information signals and as a signal used to charge an energy storage device. 
         [0026]    Although the present disclosure has been particularly shown and described with reference to the preferred embodiments and various aspects thereof, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure. It is intended that the appended claims be interpreted as including the embodiments described herein, the alternatives mentioned above, and all equivalents thereto.