Abstract:
A method for operating an amplifier module of a communication satellite involves saving at least one configuration parameter of the amplifier module in a non-volatile memory designed to store the configuration parameter when the amplifier module is not energized. The configuration parameter can be loaded from the non-volatile memory and used to configure the amplifier module.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2013 003 903.7, filed Mar. 8, 2013, the entire disclosure of which is herein expressly incorporated by reference. This application is related to U.S. patent application Ser. No. 14/200,586, filed on even date herewith, entitled “Method for Operating a Traveling-Wave Tube Module,” the entire disclosure of which is herein expressly incorporated by reference. 
     FIELD OF THE INVENTION 
     Exemplary embodiments of the present invention relate to a method for operating an amplifier module of a communication satellite as well as to an amplifier module. 
     BACKGROUND OF THE INVENTION 
     Traveling wave tube amplifiers (TWTA) are used primarily in satellites as a power amplifier and are usually designed as traveling wave tube modules. These traveling wave tube modules comprise a traveling wave tube, which determines primarily the high frequency properties, and a power supply, which generates primarily the supply voltages for the traveling wave tube, a telemetry and/or telecommand interface to the satellite, as well as a control unit. The traveling wave tube module can be complemented with a pre-amplifier (also called a channel amplifier), which can also include a linearizer, which can also be integrated with other components in a housing. This combination is referred to as a high frequency power module. 
     A high frequency signal is amplified in a traveling wave tube by conveying an electron beam past a conductor that usually exhibits the shape of a helix and through which the high frequency signal flows. When the conductor and the electron beam are suitably configured, the energy from the electron beam can be transferred to the high frequency signal. 
     Traveling wave tube modules and, in general, amplifier modules are generally constructed in such a way that devices of the same type are interchangeable, so that a user can place them on the satellite in any way. In particular, a satellite can have a plurality of identically structured traveling wave tube modules, each of which is assigned a channel of the satellite; and these traveling wave tube modules are used to amplify the high frequency signal of the respective channel. 
     This means that the properties of the individual channels are not taken into consideration. After the amplifier modules are switched on, they can then be configured for the channel properties and/or type of mode per telecommand (i.e. by means of a command from a ground station). This configuration process has to be performed anew after each power on. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present invention are directed to an amplifier module that is simple and easy to configure. 
     One aspect of the invention relates to a method for operating an amplifier module of a communication satellite. 
     The amplifier module can comprise an amplifier unit and a control unit to drive the amplifier unit. It should be recognized that the communication satellite can have a plurality of amplifier modules, each of which can be assigned to a channel of the satellite. 
     The amplifier module can be a traveling wave tube module, in which the gain takes place by means of a traveling wave tube. However, it is also possible that the amplifier module is a semiconductor amplifier module with a semiconductor amplifier. 
     According to one embodiment of the invention, the method comprises the steps: saving at least one configuration parameter of the amplifier module in a non-volatile memory designed to store the configuration parameter, when the amplifier module is not energized; after the amplifier module is energized, loading the configuration parameter from the non-volatile (data) memory; and configuring the amplifier module as a function of the loaded configuration parameter. 
     In this context “energizing the amplifier module” should be understood to mean switching on the amplifier module by supplying power to the circuit of the amplifier module, such as, for example, a pre-amplifier/a linearizer of a traveling wave tube module. 
     The non-volatile memory is usually designed to withstand the environmental conditions in space. That is, the non-volatile memory can be resistant to temperature fluctuations over a large range and/or resistant to radiation. The environmental conditions, to which a satellite in operation is exposed, discourage the person skilled in the art from installing a plurality of electronic components that are not interchangeable or that can be interchanged only with difficulty, when the satellite is in orbit. 
     The non-volatile memory is usually designed to buffer a plurality of configuration parameters, when the amplifier module is not energized, for example, when it has been separated from the power supply of the satellite by a master controller of the satellite. 
     In this case a configuration parameter may be, in general, a data value that can be used by a control unit of the amplifier module to configure and/or to adjust itself and/or additional components of the amplifier module, such as, for example, a regulator unit and/or an amplifier unit. 
     In particular, adjustments (i.e. configuration parameters), which are made by the operator of the satellite, can be saved and retrieved when the amplifier module is switched on, so that the amplifier module is immediately in the desired configuration. 
     For example, the non-volatile memory can be read out, and a read-out value can be transferred into a register. Then any changes made in this register can be written back either automatically or upon command into the non-volatile memory. Even if changes are not made directly in the non-volatile memory, it is possible that these changes are then automatically applied and/or applied per command in the register. 
     Saving the configuration parameters in a non-volatile memory can have the following advantages. 
     The operator of the satellite can optimize the individual amplifier modules during satellite tests on the ground. For example, the operator can adjust an output power to a value that is used in the channel that is to be provided; and/or the operator can configure a channel amplifier and/or a linearizer. In orbit the amplifier module is in the optimal state immediately after it has been switched on and does not have to be first adjusted by means of a number of telecommands. 
     Furthermore, the situation may arise that the amplifier module is switched off in orbit because of a safety circuit and/or is switched off per telecommand for operational reasons. After the amplifier module is switched on again, the amplifier module may be in exactly the state, in which it was prior to the last power off, and does not have to be re-adjusted. 
     According to one embodiment of the invention, the method comprises the further steps of: separating the amplifier module from a power supply of the satellite, after the configuration parameter has been saved; and connecting the amplifier module to the power supply prior to loading the configuration parameter. As stated, these steps can be executed by a master controller and/or a control unit outside the amplifier module, for example, by means of a safety circuit and/or by means of a telecommand, which can be sent, for example, from a ground station to the satellite. 
     According to one embodiment of the invention, the method further comprises the step of: determining a change in the configuration parameter, in which case the configuration parameter is automatically saved in the non-volatile memory, when a change has been determined. For example, a software function of the control unit can monitor certain memory areas of a volatile memory of the control unit and then, whenever these memory areas are changed, the changes are immediately applied in the non-volatile memory. Every time that the configuration is changed or more specifically every time certain configuration parameters are changed, the new configuration or more specifically the modified configuration parameters is and/or are automatically saved in the non-volatile memory. 
     It is also possible that the current configuration or more specifically the configuration parameter(s) is and/or are applied automatically in the non-volatile memory prior to the last power off, independently of whether a change was made or not. 
     It is also possible that all or only some of the configuration parameters are automatically saved. If the operator of the satellite would like to have certain configuration parameters, independently of the current adjustment or rather configuration, always in a certain setting after power on, then it is possible to suppress the save operation of the current adjustment of these parameters. 
     According to one embodiment of the invention, the method further comprises the step of receiving a telecommand that a configuration parameter is to be saved; in this case the configuration parameter is saved in the non-volatile memory, when the telecommand has been received. In this way configuration parameters can be changed only once by the ground station and are then made available after the amplifier module is restarted. 
     The current adjustment does not have to be automatically saved or more specifically the current configuration parameters do not have to be automatically saved, but rather they are not saved until after a corresponding (tele)command. In the event of a corresponding memory command, the configuration parameters can be loaded into the non-volatile memory, from where they can be retrieved again. This approach may have the advantage that the amplifier module can always be switched on, if desired by the operator of the satellite, in the same wake-up state, but thereafter can be put into the desired operating state without a comprehensive configuration process. 
     According to one embodiment of the invention, a configuration area can be transferred or rather copied from a volatile memory of the amplifier module to the non-volatile memory in order to save the configuration parameter. In order to load the configuration parameter, the content of the non-volatile memory can be transferred or more specifically copied to the configuration area. This approach allows a plurality of configuration parameters to be saved and set at the same time. 
     According to one embodiment of the invention, the method further comprises the step of: determining that at least one specific configuration parameter is not transferred or more specifically copied from the configuration area to the non-volatile memory, in order to prevent the configuration parameter in the non-volatile memory from being overwritten. 
     According to one embodiment of the invention, a configuration parameter is an adjustment of a regulator unit designed to regulate a voltage of a traveling wave tube of a traveling wave tube module, a cathode voltage of the traveling wave tube, a Wehnelt voltage of the traveling wave tube, an anode voltage of the traveling wave tube, one or more collector voltages or any other operating variable of the traveling wave tube. Any or all specific control parameters of the traveling wave tube can be buffered in the non-volatile memory, in order to be able to operate the traveling wave tube again in the same configuration after the last power off, without having to make any additional adjustments. 
     According to one embodiment of the invention, the method further comprises the step of saving a set of the configuration parameters of the amplifier module in the non-volatile memory. It is not only possible to save individual configuration parameters, but it is also possible, as an alternative or in addition, to save groups or rather sets of configuration parameters and/or information that relates to these sets. The adjustments of the voltages and the currents can be combined together to form sets of parameters that can be retrieved only as a set, for example, as a function of the frequency range, in which the amplifier module is to be operated. The user can select a set between 1 and n as the set that is to be saved. The information (i.e., for example, a number between 1 and n) which set of parameters is selected for saving can also be saved in the non-volatile memory. Then, in addition and beyond this step, additional adjustments or rather additional configuration parameters, for example, the output power, can be made and saved. 
     The configuration that can be selected may be a set of parameters, for example, composed of different voltages and/or currents. In addition and beyond this feature, individual configuration parameters can also be saved in order to adjust, for example, the output power by way of the anode voltage and/or the cathode current. A configuration can comprise a set of operating parameters and/or the adjustment of individual parameters that are included in the set of operating parameters. 
     If, for example, an amplifier is to be operated in a specific frequency band, then this operation will require, for example, a set of parameters having a specific number (as such, for example, the number 2). Of this set of parameters the anode voltage and/or the cathode current can be changed in certain steps, in order to be able to adjust the output power, for example, to a level 18. 
     Therefore, one example of a configuration that could be filed could be: set number 2, output power level 18. 
     The same could apply to sets of configuration parameters of a pre-amplifier/a linearizer. In this case, too, a suitable set of operating parameters could be selected (such as, for example, number 2), which can include, among other things, the adjustment of the linearizer and/or a basic gain in such a way that this adjustment matches the frequency band. For example, the operating mode (the fixed gain mode (FGM), the automatic level control (ALC)), the level (gain in FGM, output power in ALC) and/or also mute on or off can be changed. Therefore, the configuration that is filed can comprise the number of the set of parameters together with the states of the parameters to be changed. 
     According to one embodiment of the invention, a linearization curve of a linearizer of a traveling wave tube module is saved as a plurality of configuration parameters. A traveling wave tube module can comprise a linearizer, i.e. an amplifier that is designed to balance a non-linear gain characteristic of the traveling wave tube. For this purpose a linearization curve can be saved for the linearizer; and this linearization curve is used by the linearizer to amplify the high frequency signal, which is fed to the traveling wave tube in a non-linear way. This linearization curve can be modified, for example, as a function of the frequency range; and the changes can be buffered in the non-volatile memory. In addition to a strictly linearization curve or more specifically the linearization characteristic it is also possible to save configuration parameters for the gain and the frequency response. 
     The linearizer can also be combined with a pre-amplifier, or it can involve a strictly pre-amplifier without a linearizer. It is also possible to save the gain and/or the frequency response of an equalizer. In this case, too, the adjustments for the linearizer/the pre-amplifier can be combined together to form 1 to n sets of parameters; and these sets of parameters can be retrieved and/or saved as a function of the application. Configuration parameters that can be saved include the set that is currently being selected. In addition and beyond this feature, additional adjustments can also be saved, for example, the different modes, for example, a fixed gain mode (FGM) or an automatic level control (ALC), different levels of gain (in FGM) and/or different levels of output power (in ALC) that can also be saved as the configuration. 
     An additional aspect of the invention relates to an amplifier module for a communication satellite. A module can be, for example, a module with a common housing or a common carrier element, to which the components of the amplifier module are attached and/or with which the components of the amplifier module, such as, for example, a control unit, regulator units, the amplifier unit, such as, for example, a traveling wave tube or a semiconductor amplifier, etc., can be installed together in the satellite. 
     According to one embodiment of the invention, the amplifier module comprises an amplifier unit and a control unit, in order to drive the amplifier unit. 
     The amplifier unit can be a traveling wave tube. The traveling wave tube can comprise, for example: an emitter designed to generate an electron beam when a voltage is applied; a section of an amplifier, which is traversed by the electron beam, and in which a conductor is arranged, and in which a high frequency signal, which runs through the conductor, can be amplified by means of the electron beam; and a collector that is designed to accommodate the electron beam and that feeds the electron beam back to the emitter. 
     Furthermore, the control unit comprises a non-volatile, writable memory designed to store at least one configuration parameter of the amplifier module, when the amplifier module is not energized by an external power supply. The non-volatile memory can be provided, for example, in a special chip that can be installed separately from the electronics of the control unit in the amplifier module. 
     According to one embodiment of the invention, the control unit comprises a volatile memory. It is possible that the amplifier module comprises an additional memory, the content of which is erased when the amplifier module is separated from the power supply. 
     According to one embodiment of the invention, the amplifier module further comprises an auxiliary voltage supply designed to supply the non-volatile memory with energy, when the amplifier module is not energized by an external power supply. For example, the auxiliary voltage supply can comprise a capacitor or a battery. In this case the capacitor or battery is charged by the external power supply, when the amplifier module is not connected to the power supply. 
     However, it may also be the case that the auxiliary voltage supply is used only to generate the internal power supplies during normal operation. In this case it is possible that all of the circuits of the amplifier module are in the de-energized state. That is, when the amplifier module is switched off, the circuits are disconnected from the power supply. 
     According to one embodiment of the invention, the amplifier module further comprises a telecommand interface designed to receive a telecommand that initiates that the configuration parameter(s) is and/or are saved in the non-volatile memory. For example, this telecommand interface may be an external interface of the amplifier module, with which the amplifier module can communicate with an additional control unit of the satellite. 
     According to one embodiment of the invention, the amplifier module further comprises at least one regulator unit designed to drive the amplifier unit. For example, one or more collector voltages, an anode voltage, a cathode voltage and/or any other operating variable can be regulated with this regulator unit. The control unit is designed to read out a configuration parameter of the regulator unit and to save this configuration parameter in the non-volatile memory and/or to read out the configuration parameter from the non-volatile memory and to set correspondingly in the regulator unit. 
     In this case, too, it is possible that the adjustments of the regulator for the various voltages are filed in sets of parameters and that it is possible to select with the configuration only the set that is currently being used. In other words, the selection of the current set of parameters may be a configuration parameter that is filed in the non-volatile memory. 
     According to one embodiment of the invention, the control unit is designed to carry out the method for operating the amplifier module, as described above and below. It goes without saying that the features of the amplifier module may also be the features of the method and vice versa. 
     The non-volatile memory and/or the control unit can be accommodated individually or in total in the power supply of the amplifier module. The non-volatile memory and/or the control unit can also be accommodated in the pre-amplifier and/or the linearizer; or it is also possible that one portion can be accommodated in the power supply, and the other portion can be accommodated in the pre-amplifier and/or the linearizer. 
     Furthermore, it is possible that in the case of one traveling wave tube module two traveling wave tubes are supplied with power by one power supply and, if necessary, have a common pre-amplifier; or each traveling wave tube has individually a pre-amplifier. 
     Some exemplary embodiments of the invention are described in detail below with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows in schematic form a view of a communication satellite according to one embodiment of the invention. 
         FIG. 2  shows in schematic form a view of an amplifier module according to one embodiment of the invention. 
         FIG. 3  shows a flow chart for a method for operating an amplifier module according to one embodiment of the invention. 
     
    
    
     In principle, identical or similar parts are provided with the same reference numerals. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a communication satellite  10  with an antenna  12 , a master control unit or rather a master controller  14  and a power supply  16 , which is supplied with energy from, for example, a solar panel  18 . 
     Furthermore, the communication satellite  10  has an amplifier module  20  in the form of a traveling wave tube module  20 .  FIG. 1  shows only one channel of the communication satellite  10 . Typically a communication satellite  10  can have a plurality of channels, each of which can comprise a traveling wave tube module  20 . 
     The communication satellite  10  can receive a high frequency signal  22  by means of the antenna  12  and can pass the high frequency signal to the traveling wave tube module  20 , where the high frequency signal  22  is amplified to an amplified high frequency signal  24  and can be emitted again by means of the antenna  12  (or an additional antenna). In this case the traveling wave tube module  20  is supplied with power  26  by means of the power supply  16 . Furthermore, the traveling wave tube module  20  can be driven by the control unit  14  and can receive, for example, telecommands  28 , which were received, for example, by means of the antenna  12  and were evaluated by the control unit  14 . 
     The traveling wave tube module can be separated from the power supply  16  and re-connected again to the power supply with these telecommands and/or with a safety circuit of the control unit  14 . 
       FIG. 2  shows a traveling wave tube module  20  in detail. The traveling wave tube module  20  comprises a traveling wave tube  30 , which receives the high frequency signal  22  over a high frequency input  32  and emits the amplified high frequency signal  24  over a high frequency output  34 . 
     The traveling wave tube  30  comprises an emitter  36 , with which an electron beam  38  can be generated, and a collector  40 , which accommodates again the electron beam  38 . This arrangement allows the electric current from the electron beam  38  to be fed back again to the emitter  36 . Between the emitter and the collector  38  there is an amplifier region  42 , in which the high frequency signal  22  is amplified by means of the electron beam  38 . In this case the high frequency signal  22  is sent by way of a conductor  44  through the traveling wave tube  30 . 
     The traveling wave tube module  20  can have a channel amplifier and/or a linearizer  46  between the high frequency input  32  and the traveling wave tube  30 . The non-amplified high frequency signal  22  can be either pre-amplified with the channel amplifier and/or can be linearized with the linearizer, before the high frequency signal is fed to the traveling wave tube  30 . 
     The traveling wave tube  30  is driven by a plurality of secondary regulators or rather regulator units  48 , which can adjust and/or regulate, for example, an anode voltage  50 , one or more collector voltages  52 , and a cathode voltage of the emitter and additional adjustable voltages or more specifically operating variables  54  of the traveling wave tube  30 . 
     The secondary regulators  48  are supplied with a high voltage  58  by a high voltage generating device  56 , which is supplied with current and/or voltage  62  by a pre-regulator and a filter  60 . The pre-regulator and the filter  60  convert the current  26  from the power supply  16  of the satellite  10  to a constant and uniform direct current  62 . 
     In addition, the traveling wave tube module  20  comprises an electronic control unit  64 , which can adjust and drive the regulator units  48  and the channel amplifier and/or the linearizer  46 . The unit  46  can also be a strictly pre-amplifier or a combination of an amplifier and a linearizer. Furthermore, the traveling wave tube module  20  can comprise a telecommand interface  66 , which can pre-condition the telecommands  28  for the control unit  64 . 
     The control unit  64  comprises a memory module  68 , which comprises a non-volatile memory or more specifically a read only memory  70  and a volatile memory  72 . 
     The memory module  68  or more specifically at least the non-volatile memory  70  can be supplied with power  76  by an auxiliary voltage supply  74 , which is connected to the pre-regulator and the filter  60 . The auxiliary voltage supply  74  can comprise a battery or a capacitor; and this battery or capacitor can be charged, when the traveling wave tube module  20  is connected to the power supply  16 . 
     However, it is also possible that the non-volatile memory  70  is able to save de-energized data, such as, for example, a FLASH memory. 
     In order to control the traveling wave tube module  20 , the control unit  64  can adjust certain configuration parameters, manipulated variables and/or settings  78  of the components  46 ,  48 ,  56 ,  60 ,  66 ,  74  and/or can send configuration parameters  78  to these components and/or can read out the configuration parameters from these components. 
     For example, the control unit  64  can set the values  78   a  of a linearization curve of the linearizer  46  and/or the desired value  78  for the cathode voltage  54  and/or the desired value  78   b  for the collector voltage  52 . 
     Then the configuration parameters  78  can be saved automatically by the control unit  64  and/or on command in the non-volatile memory. For example, the volatile memory  72  comprises a configuration memory area  80 , which can be balanced, for example, automatically with the non-volatile memory  70 . 
       FIG. 3  shows a flow chart, with which the traveling wave tube module  20  can be operated. 
     In step  90  at least one of the configuration parameters  78  of the traveling wave tube module  20  is saved in the non-volatile memory  70 . This step can be performed already on the ground and/or also in orbit. The save operation can be initiated by a telecommand  28  and/or can be done automatically by the control unit  64 . 
     In step  92  the traveling wave tube module  20  is separated from the power supply  16  of the satellite  10 . For example, a corresponding telecommand  28  can cause the master controller  14  of the satellite  10  to switch off the traveling wave tube module  20 . It is also possible that the traveling wave tube module  20  is switched off by a safety circuit. 
     In step  94  the traveling wave tube module  20  is connected again to the power supply  16 . For example, the master controller  14  of the satellite  10  receives again a corresponding telecommand and energizes again the traveling wave tube module  20 . 
     In step  96  the configuration parameter  78  is loaded from the non-volatile memory  70  by means of the control unit  64 ; and the traveling wave tube module  20  is configured as a function of the loaded configuration parameter  78 . If, for example, the control unit  64  detects that the traveling wave tube module  20  is switched on again or more specifically is energized again, then the control unit  64  can execute a start sequence, in which the configuration parameters  78 , saved in the non-volatile memory  70 , are set again for the traveling wave tube module  20 . For example, the control unit can set the desired values  78   a ,  78   b  for the anode voltage  50  and the collector voltage  52  again to the values that were set, prior to the last power off of the traveling wave tube module  20 . 
     For the sake completeness, it must be noted that the term “comprising” does not exclude other elements or steps; and that the term “one” or “a” does not exclude a plurality. Furthermore, it must be pointed out that the features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference numerals in the claims should not be regarded as reflecting a limitation. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.