Patent Publication Number: US-2023146480-A1

Title: Satellite communication system, communication terminal, and method of operation

Description:
BACKGROUND 
     Field of the Invention 
     The present disclosure generally relates to a communication terminal and its system and method of operation. In particular, the present disclosure relates to a communication terminal configured to function effectively when experiencing vibrations and its method of compensating for the vibrations. 
     Background Information 
     Many portable satellite terminals operate in mobile applications which cause vibrations. When a terminal experiences vibrations, all of its components also experience the vibrations. When the terminal uses a crystal oscillator as a common reference for frequency or timing, subjecting the crystal oscillator to vibrations causes its phase noise to degrade and the performance of the terminal suffers. In some cases the degradation of the phase noise can cause the terminal to fail completely. This makes it necessary to manufacture terminals with expensive crystal oscillators which do not have phase noise degraded by vibrations. 
     SUMMARY 
     It has been discovered that it is desirable to manufacture communication terminals (e.g., portable satellite terminals) with less expensive parts. However, less expensive crystal oscillators typically experience more phase noise degradation due to vibrations. The present disclosure provides systems and methods which compensate for the noise caused by vibration, thus enabling communication terminals to be manufactured with less expensive parts. 
     In view of the state of the known technology, one aspect of the present disclosure is to provide a communication terminal. The communication terminal includes at least one of a transmitter or a receiver, a common reference device, a vibration sensor, and a controller. The at least one of the transmitter or the receiver is configured for transmission of communications. The common reference device is configured to provide a common reference for at least one of frequency or timing of the communications sent or received by the at least one of the transmitter or the receiver. The vibration sensor is configured to detect vibrations. The controller is configured to adjust a control voltage applied to the common reference device based on the vibrations detected by the vibration sensor. 
     Another aspect of the present disclosure is to provide a method of transmitting or receiving communications by a communication terminal experiencing vibrations. The method includes measuring vibrations experienced by the communication terminal in at least one axis, determining a total error based on the measured vibrations, adjusting a control voltage applied to a common reference device based on the total error, and sending or receiving one or more communication using the common reference device for at least one of frequency or timing of the one or more communication. 
     Another aspect of the present disclosure is to provide a satellite communication system. The satellite communication system includes at least one communication terminal, at least one satellite, and at least one gateway. The at least one communication terminal is installed at a location that experiences vibrations. The at least one communication terminal includes a common reference device configured to provide a common reference for at least one of frequency or timing of communications sent or received by the at least one communication terminal. The at least one gateway is configured to communicate with the at least one communication terminal via the at least one satellite. The at least one communication terminal is configured adjust a control voltage applied to the common reference device based on detected vibrations and thereafter use the common reference device during transmission of communications with the at least one gateway via the at least one satellite. 
     Also, other objects, features, aspects and advantages of the disclosed communication terminal, communication system and method of operation will become apparent to those skilled in the art in the field of portable satellite terminals from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of a communication terminal, system and method with various features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG.  1    illustrates an example embodiment of a satellite communication system in accordance with the present disclosure; 
         FIG.  2    illustrates an example embodiment of a communication terminal in accordance with the present disclosure: 
         FIG.  3    illustrates an example embodiment of a method of operating a communication terminal in accordance with the present disclosure; 
         FIG.  4    illustrates an example embodiment of a low-pass filter configured for use with the communication terminal of  FIG.  2   ; 
         FIG.  5    illustrates an example embodiment of the adjustment of the control voltage to the common reference device of the communication terminal of  FIG.  2   ; and 
         FIG.  6    illustrates an example embodiment of the output of the common reference device of the communication terminal of  FIG.  2    being the integral of the control voltage. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
       FIG.  1    illustrates an example embodiment of a satellite communication system  10  in accordance with the present disclosure. In the illustrated embodiment, the system  10  includes at least one communication terminal  12 . The communication terminal  12  can be, for example, a portable satellite terminal. The communication terminals  12  are installed at locations that experience vibrations. Here, each of the communication terminals  12  is a mobile communication terminal installed on a respective mobile vehicle. The communication terminals  12  disclosed herein are particularly suited for mobile applications which experience turbulence, for example, for installation on automobiles, trains, boats, helicopters, airplanes and/or other vehicles. The communication terminals  12  disclosed herein are also particularly suited for nonmobile applications which experience vibrations, for example, for installation at oil wells or other structures which experience vibrations. These mobile and nonmobile applications have different vibration specifications, and the communication terminal  12  of the present disclosure is configured to self-correct based on the vibrations experienced at a particular location such that the communication terminal  12  can function regardless of the specific vibration specifications where it is installed. 
     In the illustrated embodiment, the system  10  includes at least one satellite  14 , at least one gateway  16  and/or a network management system  18 . The communication terminals  12 , the satellite  14  and the gateway  16  typically communicate with each other over a radio frequency link, such as a Ku-band link, a Ka-band link, an L band link, an S band link or any other suitable type of link as understood in the art. Thus, the communication terminals  12  are configured to communicate with the gateway  16  via the satellite  14 , and likewise the gateway  16  is configured to communicate with the communication terminals  12  via the satellite  14 . The gateway  16  is further configured to communicate with the network management system  18 , which communicates with remote sites, such as web content providers, via the Internet, cloud storage, or other communication networks as understood in the art. The gateway  16  and/or the network management system  18  can further include or be configured as an inroute group manager (IGM) which controls the bandwidth allocations to the communication terminals  12  (e.g., on an inroute or inroute group basis) and correspondingly controls and administers the bandwidth allocation approaches. 
     The system  10  can use various signal protocols to exchange communication signals between the communication terminal  12  and the gateway  16  via the satellite  14 . The system  10  is particularly advantageous for signal protocols which depend on the accuracy of frequencies and timing to synchronize the communication terminals  12  with the satellite  14  and/or gateway  16 . In an example embodiment, the system  10  can use a Time-Division Multiple Access (TDMA) signal protocol. As will be understood by those of ordinary skill in the art from this disclosure, TDMA is a channel access method in which data packets are transmitted within a narrow time window. In another example embodiment, the system  10  can use a Frequency-Divisional Multiple Access (FDMA) signal protocol. As will be understood by those of ordinary skill in the art from this disclosure. FDMA is a channel access method which provides different frequency bands to different data streams. Those of ordinary skill in the art will further recognize from this disclosure that there are various other signal protocols which benefit from accurate frequencies and timing at the communication terminal  12 . 
       FIG.  2    illustrates an example embodiment of the communication terminal  12  in more detail. As illustrated in  FIG.  2   , the communication terminal  12  includes a housing  20 . In the illustrated embodiment, the housing  20  is a box-shaped structure, but the housing  20  can also be other shapes and sizes. The housing  20  further includes one or more edges  22  which can be used as a reference for the X, Y and Z axes as discussed herein. The housing  20  can be formed of any suitable material and provides an outer shell to protect the other components located therein. In an embodiment, the housing  20  further includes a coupling mechanism  24  configured to enable the housing  20  to be installed in an appropriate location, for example, to a mobile vehicle or nonmobile structure which experiences vibrations. 
     In the illustrated embodiment, the communication terminal  12  includes a common reference device  26 , a vibration sensor  28 , a controller  32 , a transmitter  34  and/or a receiver  36  (e.g., a transceiver  38 ), a local server  40 , and/or a power source  42 . The controller  32  is configured to control the common reference device  26 , the vibration sensor  28 , the transmitter  34  and/or the receiver  36  (e.g., a transceiver  38 ), the local server  40 , and/or the power source  42  as discussed herein. 
     In the illustrated embodiment, the communication terminal  12  includes a common reference device  26 . The common reference device  26  provides a common reference for frequency and timing functions executed by the communication terminal  12 . More specifically, the common reference device  26  functions as a common reference for at least one of the frequency and timing of communications transmitted (e.g., sent and/or received) by the transmitter  34  and/or the receiver  36 . In an embodiment, the common reference device  26  is configured to keep track of time for communications sent and/or received by the transmitter  34  and/or the receiver  36 . In an embodiment, the common reference device  26  is configured to stabilize frequencies for communications sent and/or received by the transmitter  34  and/or the receiver  36 . In an embodiment, the common reference device  26  is configured to shift its oscillation frequency based on an applied voltage, as discussed in more detail below. 
     In an embodiment, the common reference device  26  includes a crystal oscillator. More specifically, the common reference device  26  includes a voltage controlled temperature compensated crystal oscillator (VCTCXO). As understood by those of ordinary skill in the art from this disclosure, a crystal oscillator typically includes an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electric signal with constant frequency. The frequency can be used to keep track of time and/or stabilize frequencies for radio transmitters and receivers. A VCTCXO is a type of crystal oscillator which uses a two-port crystal resonator with a special electrode structure, which allows the VCTCXO to compensate for temperature changes and shift its oscillation frequency independently. 
     In the illustrated embodiment, the communication terminal  12  includes a vibration sensor  28 . The vibration sensor  28  is configured to detect vibrations experienced by the communication terminal  12 . More specifically, the vibration sensor  28  is configured to measure vibrations experienced by the communication terminal  12 . In an embodiment, the vibration sensor  28  is configured to measure vibrations experienced by the communication terminal  12  in multiple vectors. The multiple vectors can include the X, Y and/or Z axes (e.g., as illustrated in  FIG.  2   ). Thus, in an embodiment, the vibration sensor  28  is configured to detect the vibrations in each of X, Y and Z axes. In an embodiment, the vibration sensor  28  is configured to measure the amplitude of vibrations in one or more respective axis, the frequency of vibrations in one or more respective axis, and/or the mode of vibrations in one or more respective axis. 
     In an embodiment, the vibration sensor  28  is located adjacent to the common reference device  26  within the housing  20  so as to detect vibrations experienced by the common reference device  26  (e.g., in the X, Y and Z axes) as accurately as possible. The vibration sensor  28  is further configured to output signals reflecting the detected vibrations to the controller  32  for further processing in accordance with the present disclosure. In an embodiment, the vibration sensor  14  includes a piezoelectric sensor. As understood by those of ordinary skill in the art from this disclosure, a piezoelectric sensor transforms mechanical energy into an electrical output which can be transmitted to the controller  32 . 
     In the illustrated embodiment, the vibration sensor  28  is calibrated and positioned so that its X, Y and Z axes match the X, Y and Z axes used as a reference from the communication terminal  12 . Thus, in an embodiment, the vibration sensor  28  is installed in the communication terminal such that that its X, Y and Z axes are referenced off of the edges  22  of the housing  20 . 
     In an embodiment, the communication terminal  12  includes one or more low-pass filter  30  at the output of the vibration sensor  28 . In an embodiment, the vibration sensor  28  includes one or more low-pass filter  30 . In an embodiment, the communication terminal  12  includes a low-pass filter  30  for each of the X, Y and Z axes which are being used to measure vibrations. An example embodiment of one or more low pass filter  30  is illustrated by  FIG.  4   . In an embodiment, each low pass filter  30  is configured to pass signals with a frequency lower than a predetermined value and attenuate signals with a frequency higher than the predetermined value. In an embodiment, each low-pass filter  30  can be added in series with a control pin to average the error and filter out noise. 
     In the illustrated embodiment, the communication terminal  12  includes a controller  32 . As explained in more detail below, the controller  32  is configured to adjust a control voltage applied to the common reference device  26  based on the vibrations detected by the vibration sensor  28 . More specifically, the controller  32  is configured to determine a total error based on the detected vibrations and adjust the control voltage applied to the common reference device  26  based on the total error. The controller  32  is configured to determine the total error based on the vibrations detected by the vibration sensor  28  in each of the X, Y and Z axes. In doing so, the controller  32  is configured to cause the common reference device  26  to shift its oscillating frequency. In this way, the communication terminal  12  is configured adjust the control voltage applied to a common reference device  26  based on detected vibrations and thereafter use the common reference device  26  during the transmission of communications with the gateway  16  via the satellite  14 . 
     In the illustrated embodiment, the controller  32  includes a processor  44  and a memory  46 . As understood in the art, the controller  32  can include a microcomputer with a control program that controls the communication terminal  12  as discussed herein. The controller  32  can also include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The RAM and ROM store processing results and control programs that are run by the controller  32 . The controller  32  is operatively coupled to the various components of the communication terminal  12  as appropriate, in a conventional manner. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the controller  32  can be any combination of hardware and software that will carry out the functions of the present disclosure. 
     The memory  46  can include, for example, an internal memory in the communication terminal  12 , or other types of memory devices such as a flash memory or hard drives with external high speed interface such as a USB bus or an SATA bus, or remote memories such as cloud storage and so on. These other types of memory can be present at the terminal  12  or accessible at a location apart from the terminal  12  via a network connection such as an Ethernet connection, a WiFi connection or any other suitable type of connection as understood in the art. Moreover, the memory  46  can include at least one buffer which is configured to buffer, for example, received data packets transmitted from the gateway  16 . 
     In the illustrated embodiment, the communication terminal  12  includes at least one of a transmitter  34  and a receiver  36 . The transmitter and the receiver are configured for transmission of communications. More specifically, the transmitter and the receiver are configured for satellite communications with the gateway  16  via the satellite  14 . The communications can include data packets. The transmitter  34  and the receiver  36  can be separate components or can both be part of a single transceiver  38 . Thus, in an embodiment, a transceiver  38  includes the transmitter  34  and the receiver  36 . A transceiver  38  can include, for example, an integrated satellite modem and any other suitable equipment which enables the transceiver  38  to communicate with one or more of the orbiting satellites  14  as understood in the art. The transmitter  34  and/or the receiver  36  can also be coupled to and/or be part of an antenna, which can be included as part of the communication terminal  12  or can be an external antenna that is attached to the communication terminal  12  via an antenna port. 
     The transmitter  34  is configured to send communications from the communication terminal  12 . More specifically, the transmitter  34  is configured to send communications from the communication terminal  12  to the gateway  16  via the satellite  14 . Phase noise caused by vibrations applied to the communication terminal  12  can affect the transmitter&#39;s  32  error vector magnitude, adjacent power and/or in orthogonal frequency division multiplexing inter carrier interference. The error vector magnitude can affect the accuracy of the phase being transmitted by the transmitter  34 . 
     The receiver  36  is configured to receive communications at the communication terminal  12 . More specifically, the receiver  36  is configured to receive communications from the gateway  16  via the satellite  14 . Phase noise caused by vibrations applied to the communication terminal  12  can affect the receiver&#39;s  34  bit error rate, acquisition, linearity and timing. 
     In the illustrated embodiment, the communication terminal  12  includes a local server  40 . The local server  40  is configured to communicate with an access point, such as a wireless application protocol (WAP) or any other suitable device, which enables the local server  40  to enable end user devices to access the system  10 . Such end user devices include, for example, desktop computers, laptop or notebook computers, tablets (e.g., iPads), smart phones, smart TVs and any other suitable devices as understood in the art. Naturally, the communications between the local server  40  and the access point and/or the end user devices can occur over wireless connections, such as WiFi connections, as well as wired connections as understood in the art. 
     In the illustrated embodiment, the communication terminal  12  includes a power source  42 . The power source  42  is configured to provide power to one or more components of the communication terminal  12 . More specifically, the power source  42  is configured to provide power to one or more of the common reference device  26 , the vibration sensor  28 , the controller  42 , the transmitter  34  and/or the receiver  36  (e.g., the transceiver  38 ), the local server  40  and/or other components. The power source  42  can include a battery. The power source  42  can also include a port or wireless device which receives power from an external power source, for example, by being plugged into the external power source. In an embodiment, the controller  32  controls power distribution from the power source  42  to one or more components of the communication terminal  12 . In an embodiment, the controller  32  controls power distribution from the power source  42  to adjust the control voltage applied to the common reference device  26 . 
       FIG.  3    illustrates an example embodiment of a method  100  of transmitting or receiving communications by a communication terminal  12  experiencing vibrations. The steps of the method  100  can be executed by the controller  32 , for example, by being stored as instructions on the memory  46  and executed by the processor  44 . It should be understood that some of the steps described herein can be reordered or omitted without departing from the spirit or scope of the method  100 . 
     Prior to executing the method  100 , the communication terminal  12  is calibrated. Calibration can occur prior to the communication terminal  12  being dispatched into the field for use (e.g., prior to being attached to a mobile vehicle or nonmobile structure which experiences vibrations). During calibration, the common reference device  26  is characterized. Specifically, the common reference device  26  is characterized to determine how the common reference device  26  is affected by the amplitude, frequency and/or mode of vibrations in each of the X, Y and Z axes. The calibration can be performed by vibrating the common reference device  26  along each of the X, Y and Z axes to determine how the common reference device  26  is affected by the amplitude, frequency and/or mode of vibrations in each of the X, Y and Z axes. The X, Y and Z axes can be determined with reference to an edge of the common reference device  26  and/or the communication terminal  12 . In an embodiment, the common reference device  26  can be calibrated prior to being installed into a communication terminal  12 , with the common reference device  26  then installed into the communication terminal so that the X, Y and Z axes used for calibration align with the X, Y and Z axes of the communication terminal  12  (e.g., using an edge  22  for reference). In an embodiment, calibration can be performed using one common reference device  26  and applied to other common reference devices  26 , such that each common reference device  26  does not need to be individually calibrated. In an embodiment, the calibration is performed by the manufacturer of the common reference devices  26 , which may be different from the manufacturer of the communication terminal  12 . 
     The vibration sensor  28  can also be calibrated prior to being installed into the communication terminal  12 . The calibration can be performed to determine the X, Y and Z axes of the vibration sensor  28 . In an embodiment, the vibration sensor  28  can be calibrated prior to being installed into a communication terminal  12 , with the vibration sensor  28  then installed into the communication terminal so that the X, Y and Z axes used for calibration align with the X, Y and Z axes of the communication terminal  12  (e.g., using an edge  22  for reference). In an embodiment, the vibration sensor  28  is installed into the communication terminal  12  so as to be located adjacent to the common reference device  26  such that the calibrated X, Y and Z axes of the vibration sensor  28  align with the X, Y and Z axes of the common reference device  26 . In an embodiment, the X, Y and Z axes of the vibration sensor  28  and the X, Y and Z of the common reference device  26  are both aligned with the X, Y and Z axes of the communication terminal  12  (e.g., using an edge  22  for reference). In an embodiment, calibration can be performed using one vibration sensor  28  and applied to other vibration sensors  28 , such that each vibration sensor  28  does not need to be individually calibrated. In an embodiment, the calibration is performed by the manufacturer of the vibration sensors  28 , which may be different from the manufacturer of the communication terminal  12 . The communication terminal  12  can further optionally be calibrated once the vibration sensor  28  has been installed to verify that the X, Y and Z axes are aligned and/or by further performing the method  100  at different vibrations to ensure that the corrections applied by the controller  32  function accurately. 
     The method  100  illustrated in  FIG.  2    begins as the communication terminal  10  is being used in a mobile or other vibrating application and thus experiencing vibrations. The vibrations can occur in one or more of the X, Y and Z directions. In most circumstances, the vibrations will likely occur in all three of the X, Y and Z directions. The X, Y and Z directions can be in relation to one or more edge  22  of the communication terminal  12  as discussed herein. 
     At step  102 , the communication terminal  12  detects vibrations. Specifically, the vibration sensor  28  detects that the communication terminal  12  is vibrating. In embodiment, the vibration sensor  28  detects the level of vibrations in at least one of the X, Y and Z directions. In an embodiment, the controller  32  only triggers step  104  of the method  100  if a minimum level of vibrations is detected in at least one of the X, Y and Z directions. In an embodiment, the controller  32  only triggers step  104  of the method  100  if vibrations are detected in at least one of the X, Y and Z directions for a minimum period of time. In another embodiment, the controller  32  triggers step  104  of the method  100  upon any detected vibrations. 
     At step  104 , the communication terminal  12  measures the vibrations experienced by the communication terminal  12  in at least one axis. More specifically, the vibration sensor  28  measures the vibrations and outputs a corresponding signal to the controller  32 . The signal can indicate, for example, the amplitude of vibrations in one or more respective axis, the frequency of vibrations in one or more respective axis, and/or the mode of vibrations in one or more respective axis. In an embodiment, the vibration sensor  28  measures the vibrations experienced by the communication terminal  12  in each of the X, Y and Z axes and outputs one or more corresponding signal to the controller  32  for each of the X, Y and Z axes. 
     At step  106 , the communication terminal  12  converts the measured vibrations into sensitivity values. The measured vibrations can be converted into sensitivity values by the vibration sensor  28  and/or by the controller  32 . In an embodiment, the measured vibrations are converted into sensitivity values for each of the X, Y and Z directions. Thus, the communication terminal  10  has a sensitivity value in the X axis (A), a sensitivity value in the Y axis (B), and a sensitivity value in the Z axis (C). In an embodiment, the sensitivity values are weight factors that are dependent on the level of the vibrations. In an embodiment, the sensitivity value for each axis is proportional to the amount of phase noise generated by the vibrations in that axis. In an embodiment, each sensitivity value is determined based on the amplitude of vibrations in a respective axis, the frequency of vibrations in a respective axis, and/or the mode of vibrations in a respective axis. The shape of the communication terminal  12  and the location of the common reference device  26  within the communication terminal  12  can affect which axis has the highest sensitivity value. 
     At step  108 , the controller  32  determines a total error based on the measured vibrations. In an embodiment, the controller  32  determines the total error based on the detected vibrations in each of the X, Y and Z axes. More specifically, the controller  32  calculates the total error by combining the sensitivity values. In an embodiment, the controller  32  is configured to use a method of goodness to calculate the total error for optimizing performance of the common reference device  26 . In an embodiment, the controller  32  combines the vibration values using the following equation: 
         {right arrow over (E)}=A *{right arrow over ( E   x )}+ B*{right arrow over (E)}   Y   +C*{right arrow over (E)}   z   (Equation 1)
 
     In Equation 1, {right arrow over (E)} is a total error vector, {right arrow over (E x )} is an error vector in the X direction, {right arrow over (E Y  )} is an error vector in the Y direction, and {right arrow over (E Z  )} is an error vector in the Z direction. Each of the error vectors can be indicated by a low-pass filter  30  of the output from the vibration sensor  28 , as illustrated for example by  FIG.  4   . A is the sensitivity value in the X direction, B is the sensitivity value in the Y direction, and C is the sensitivity value in the Z direction. 
     At step  110 , the controller  32  adjusts the control voltage to the common reference device  26  based on the calculated total error (e.g., the total error vector). More specifically, the controller  32  adjusts the magnitude of the voltage applied to the common reference device  26  based on the total error (e.g., the total error vector). By adjusting the magnitude of the voltage applied to the common reference device  26 , the controller  32  causes the common reference device  26  to shift its oscillating frequency. More specifically, since the applied voltage is based on the vibrations detected by the vibration device  28 , the controller  32  causes the common reference device  26  to shift its oscillation frequency to account for the vibrations detected by the vibration device  28 .  FIG.  5    illustrates an example embodiment of the adjustment of the control voltage to the common reference device  26 .  FIG.  6    illustrates an example embodiment of the output of the common reference device  26  being the integral of the control voltage. 
     An example embodiment of equations that can be used to correct the phase error are as follows: 
     
       
         
           
             
               
                 
                   
                     
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     From Equations 2 and 3 the magnitude and phase can be calculated and applied to the common reference device  26 . 
     At step  112 , the communication terminal  12  sends or receives one or more communication using the common reference device  12  for at least one of the frequency or timing of the communication. In an embodiment, communication terminal  12  sends or receives the communication using the common reference device  26  for the frequency of the communication. For example, certain signal protocols rely on the communication terminal  12  and the gateway  16  operating on the same frequency for the transmission and reception of a communication. In an embodiment, communication terminal  12  sends or receives the communication using the common reference device  26  for the timing of the communication. For example, certain signal protocols rely on the communication terminal  12  and the gateway  16  having accurate timing for the transmission and reception of a communication. The controller  32  is configured to send and/or receive communications by controlling the transmitter and/or receiver  36  (e.g., transceiver  38 ) using the common reference device  12  as a reference. Thus, the communications can be sent or received from a mobile vehicle including the communication terminal  12  while the mobile vehicle is experiencing vibrations. 
     The method  100  is continuously performed by the communication terminal  12  during its use. This enables the communication terminal  12  to continue to adjust the control voltage to the common reference device  26  as the vibrations change and/or shift directions in relation to the X, Y and/or Z axes. In this way, the communication terminal  12  constantly adjusts the oscillation frequency of the common reference device  26  to ensure that the timing of communications sent and/or received is always accurate, whether or not the communication terminal  12  experiences vibrations. A communication terminal  12  may degrade with continued use or experience different vibrations under different circumstances, so the applied voltage needed to correct for vibrations in a first instance is not necessarily the same as the applied voltage needed to correct for vibrations in a second instance. 
     In an embodiment, the method  100  can be triggered by the gateway  16  in response to a detection that the timing and/or frequency of the communication terminal  12  is off. 
     The embodiments described herein provide improved systems and methods for communication terminals  12  that are installed in locations that experience vibrations. These include law enforcement applications, emergency applications, fleet management applications, military applications and commercial applications (e.g., marine, railroad, etc.). These also include oil well and other nonmobile applications that experience vibrations. The improved systems and methods ensure accurate timing for communications even during periods of extreme vibrations that would otherwise cause the communication terminal  12  to fail. It should be understood that various changes and modifications to the systems and methods described herein will be apparent to those skilled in the art and can be made without diminishing the intended advantages. 
     The embodiments described herein can be employed in, for example, the Ligado and 9410 mobile satellite terminals made by Hughes Network Systems, as well as any present or future mobile satellite terminal or other type of satellite communication system as understood in the art. 
     General Interpretation of Terms 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. 
     The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such features. Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.