Patent Publication Number: US-2022236327-A1

Title: Signal generator and a method for controlling the signal generator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims Convention priority to Japanese Patent Application No. 2021-009307, filed Jan. 25, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a signal generator and a method for controlling the signal generator. 
     BACKGROUND ART 
     Conventionally, for example, Patent Document 1 proposes a signal generator having a plurality of ports and performing a test while switching a plurality of devices under test connected to the plurality of ports. 
     CITATION LIST 
     Patent Literature 
     [Patent Document 1] Japanese Patent Application Publication No. 2013-187803 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, in the conventional signal generator as described above, the loss of the cable for connecting to the device under test is not taken into consideration, so that there is such a problem that the intensity of the signals inputted to the plurality of devices under test varies. 
     The present invention has been made to solve such a problem, and it is the object of the present invention to provide a signal generator capable of suppressing variation in the intensity of signals inputted to a plurality of devices under test, and a method for controlling the signal generator. 
     Means to Solve the Problem 
     The signal generator of the present invention comprises: a signal generation unit ( 10 ) that generates a test signal; a first attenuator ( 11 ) that attenuates the test signal generated by the signal generation unit; a plurality of output ports ( 12   a  to  12   f ) to which a plurality of devices under test ( 3   a  to  3   f ) are connected through each of cables; a distributor ( 13 ) that distributes the test signal, attenuated by the first attenuator, to each of the plurality of output ports; a plurality of second attenuators ( 14   a  to  14   f ) that attenuate each of the test signals outputted from the distributor; an attenuation amount setting unit ( 15 ) that sets attenuation amount of the first attenuator and the plurality of second attenuators; and a cable loss storage unit ( 16 ) that stores losses of the cables connected to the plurality of output ports, wherein the attenuation amount setting unit is configured to set a reference attenuation amount, obtained by subtracting the maximum amount of the losses stored in the cable loss storage unit with respect to the cables connected to the output ports from a target attenuation amount, to the first attenuator, and to set an output attenuation amount, obtained by subtracting the losses stored in the cable loss storage unit with respect to each of the cables connected to the output ports from the maximum amount of the losses, to each of the second attenuators. 
     By this configuration, the signal generator of the present invention can suppress the variation in the intensity of the test signals inputted to the plurality of devices under test connected to the output ports, since the attenuation amounts of the first attenuator and the second attenuator are set in consideration of the loss of each of the cables connected to the output ports. 
     Further, since the signal generator of the present invention can input the test signals in which the variation in intensity is suppressed to a plurality of devices under test connected to the output ports in parallel, the test time can be shortened. 
     The signal generator of the present invention may be so configured that, when any one of the output attenuation amounts exceeds a specified amount, the attenuation amount setting unit corrects the reference attenuation amount with the correction attenuation amount obtained by subtracting the specified amount from the output attenuation amount exceeding the specified amount, sets the reference attenuation amount to the first attenuator, and recalculates the output attenuation amount by subtracting the correction attenuation amount from the maximum amount of the losses. 
     By this configuration, the signal generator of the present invention can prevent a test signal having an unexpected intensity from being inputted to the device under test, by setting a specified amount within a range not exceeding the allowable attenuation amount of the second attenuator. 
     Further, in the signal generator of the present invention, the attenuation amount setting unit may be so configured to change the output attenuation amount to 0, when any of the output attenuation amounts becomes negative as a result of recalculating the output attenuation amount. 
     By this configuration, the signal generator of the present invention can prevent the second attenuator from setting a negative output attenuation amount that cannot be set to the second attenuator. 
     Further, the signal generator of the present invention may be so configured to comprise a notification unit ( 17 ) capable of notifying information on each output port of the plurality of output ports, and the attenuation amount setting unit may be so configured to notify the information on the output port corresponding to the second attenuator whose output attenuation amount has been changed to 0 as a result of the output attenuation amount of any one of the output attenuation amounts turning negative. 
     By this configuration, the signal generator of the present invention can notify the output port to which the cable with too much loss is connected. 
     A method for controlling a signal generator of the present invention is a method for controlling a signal generator ( 1 ), comprising: a signal generation unit ( 10 ) that generates a test signal; a first attenuator ( 11 ) that attenuates the test signal generated by the signal generation unit; a plurality of output ports ( 12   a  to  12   f ) to which a plurality of devices under test ( 3   a  to  3   f ) are connected through each of cables ( 4   a  to  4   f ); a distributor ( 13 ) that distributes the test signal, attenuated by the first attenuator, to each of the plurality of output ports; a plurality of second attenuators ( 14   a  to  14   f ) that attenuate each of the test signals outputted from the distributor; an attenuation amount setting unit ( 15 ) that sets attenuation amount of the first attenuator and the plurality of second attenuators; and a cable loss storage unit ( 16 ) that stores losses of the cables connected to the plurality of output ports, the method causing the attenuation amount setting unit to execute: a first setting step to set an attenuation amount, obtained by subtracting the maximum amount of the losses stored in the cable loss storage unit with respect to the cables connected to the output ports from a target attenuation amount, to the first attenuator; and a second setting step to set an output attenuation amount, obtained by subtracting the losses stored in the cable loss storage unit with respect to each of the cables connected to the output ports, from the maximum amount of the losses, to each of the second attenuators. 
     As described above, the method for controlling the signal generator of the present invention can suppress the variation in the intensity of test signals inputted to the plurality of devices under test connected to the output ports, since the attenuation amount of the first attenuator and the second attenuators are set in consideration of the loss of each of the cables connected to the output ports. 
     Effect of the Invention 
     The present invention can provide a signal generator and a method for controlling the signal generator, capable of suppressing the variation in the intensity of signals inputted to a plurality of devices under test. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a signal generator according to an embodiment of the present invention. 
         FIG. 2  is a first conceptual diagram for explaining a configuration of an attenuation amount setting unit constituting a signal generator according to an embodiment of the present invention. 
         FIGS. 3A, 3B, and 3C  collectively constitute a second conceptual diagram for explaining a configuration of an attenuation amount setting unit constituting a signal generator according to an embodiment of the present invention. 
         FIG. 3A  shows an example in which the output attenuation amount exceeds the specified amount is shown,  FIG. 3B  shows an example in which the output attenuation amount is corrected so as not to exceed the specified amount, and  FIG. 3C  shows an example in which the output attenuation amount is corrected so as not to be negative. 
         FIGS. 4A, 4B, and 4C  collectively constitute a third conceptual diagram for explaining a configuration of an attenuation amount setting unit constituting a signal generator according to an embodiment of the present invention. 
         FIG. 4A  shows an example in which the output attenuation amount exceeds the specified amount. 
         FIG. 4B  shows an example in which the output attenuation amount is corrected so as not to exceed the specified amount. 
         FIG. 4C  shows an example in which the output attenuation amount is corrected so as not to be negative. 
         FIG. 5  is a flowchart showing an attenuation amount setting operation of the signal generator according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     As shown in  FIG. 1 , a control computer device  2  is connected to a signal generator  1 . The computer device  2  is constituted by a general-purpose computer device. This computer device includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk device, a communication module, a display device, and an input device such as a pointing device, a keyboard device, and the like, which are not shown. 
     The signal generator  1  comprises of a signal generation unit  10  that generates a test signal, a first attenuator  11  that attenuates the test signal generated by the signal generation unit  10 , output ports  12   a  to  12   f  to which devices under test  3   a  to  3   f  are respectively connected through cables  4   a  to  4   f,  and a distributor  13  that distributes the test signal attenuated by the first attenuator  11  to output ports  12   a  to  12   f.    
     Further, the signal generator  1  includes second attenuators  14   a  to  14   f  that respectively attenuate the test signals distributed to the output ports  12   a  to  12   f,  an attenuation amount setting unit  15  that sets the attenuation amount of the first attenuator  11  and the second attenuators  14   a  to  14   f,  a cable loss storage unit  16  that stores the loss of cables  4   a  to  4   f  connected to the plurality of output ports  12   a  to  12   f,  and a notification unit  17  capable of notifying information on each output port of the plurality of output ports  12   a  to  12   f.    
     In the present embodiment, the cables  4   a  to  4   f  are composed of, for example, a coaxial cable, and the output ports  12   a  to  12   f  are composed of a coaxial connector. Although  FIG. 1  shows an example in which the signal generator  1  has six output ports  12   a  to  12   f,  it is sufficient for the signal generator  1  to have two or more output ports. 
     Each output port  12   a  to  12   f  can be set to either effective or ineffective by the computer device  2 . The test signal is outputted from the output port that is set to be effective among the output ports  12   a  to  12   f,  but the test signal is not outputted from the output port that is set to be ineffective. In the following description, the output port that is set to be effective is also referred to as “effective port”. 
     The signal generation unit  10  is composed of a signal generator that generates a test signal of the intensity and frequency set by the computer device  2 . The first attenuator  11  and the second attenuators  14   a  to  14   f  are composed of a digital control type variable attenuator or a voltage control type variable attenuator. 
     The cable loss storage unit  16  is composed of a rewritable non-volatile storage medium such as a flash memory. In the cable loss storage unit  16 , a loss table representing the loss of the cables  4   a  to  4   f  connected to the output ports  12   a  to  12   f  with respect to the combinations of the output ports  12   a  to  12   f  and the measurement frequency (hereinafter, also simply referred to as “cable loss”) is stored. The loss table can be rewritten from the computer device  2 , thereby allowing the user to set the loss table according to the test environment. 
     The attenuation amount setting unit  15  is composed of, for example, an ASIC (Application Specific Integrated Circuit). The attenuation amount setting unit  15  sets the attenuation amount individually for the first attenuator  11  and the second attenuators  14   a  to  14   f  based on the loss table stored in the cable loss storage unit  16 . 
     The notification unit  17  is composed of LEDs (Light Emitting Diodes) corresponding to the output ports  12   a  to  12   f,  and external output terminals for outputting the information on the output ports  12   a  to  12   f  to an external device such as the computer device  2 . 
     Hereinafter, the configuration of the attenuation amount setting unit  15  will be described in detail with reference to  FIGS. 2 to 4 .  FIGS. 2 to 4  collectively show an example in which the test signal of the measurement frequency generated by the signal generation unit  10  is attenuated and outputted from the effective ports PortA to PortD. 
     In  FIGS. 2 to 4 , “Loss Level” represents the cable loss of each PortA to PortD stored in the loss table, “Basis Level” represents the maximum amount of the cable loss of each PortA to PortD stored in the loss table. (Hereinafter referred to as “maximum cable loss”), and “Loss Level Adjust” represents the attenuation amount set in the second attenuator corresponding to each PortA to PortD. 
     In  FIG. 2 , the cable loss of each Port A to Port D stored in the loss table with respect to the measurement frequency is defined as “4”, “5”, “3”, and “11”. The attenuation amount setting unit  15  sets a reference attenuation amount obtained by subtracting the maximum cable loss “11” from the target attenuation amount to the first attenuator  11 . 
     Further, the attenuation amount setting unit  15  sets the output attenuation amounts “7”, “6”, “8”, and “0” obtained by subtracting the cable loss of each of PortA to PortD stored in the loss table from the maximum cable loss to the second attenuator corresponding to each PortA to PortD. By configuring the attenuation amount setting unit  15  in this way, test signals attenuated by the target attenuation amount are inputted to the devices under test connected to each Port A to Port D. 
       FIGS. 3A, 3B, and 3C  collectively show an example in which the output attenuation amount exceeds a specified amount (“8” in this example) according to an allowable attenuation of the second attenuators  14   a  to  14   f,  as compared with the example shown in  FIG. 2 . In  FIG. 3A , the cable loss of each PortA to PortD stored in the loss table with respect to the measurement frequency is defined as “4”, “5”, “2”, and “11”. The attenuation amount setting unit  15  sets a reference attenuation amount obtained by subtracting the maximum cable loss “11” from the target attenuation amount to the first attenuator  11 . 
     Further, the attenuation amount setting unit  15  sets the output attenuation amounts “7”, “6”, “9”, “0”, obtained by subtracting the cable loss of each of PortA to PortD stored in the loss table from the maximum cable loss, to the second attenuator corresponding to each PortA to PortD. In this case, the output attenuation amount “9” set in the second attenuator corresponding to PortC exceeds the specified amount “8”. 
     When the output attenuation amount exceeds the specified amount in this way, the attenuation amount setting unit  15  corrects the reference attenuation amount with the correction attenuation amount “1” obtained by subtracting the specified amount “8” from the output attenuation amount “9” exceeding the specified amount, and sets the reference attenuation amount to the first attenuator  11 . This means that the attenuation amount setting unit  15  adds the correction attenuation amount to the reference attenuation amount set in the first attenuator  11 . 
     Further, as shown in  FIG. 3B , the attenuation amount setting unit  15  recalculates the output attenuation amount by subtracting the correction attenuation amount “1” from the maximum cable loss “11”. This means that the maximum cable loss is “10”, and the output attenuation amounts set in the second attenuator corresponding to each PortA to PortD are “6”, “5”, “8”, and “−1”. 
     However, since a negative output attenuation amount cannot be set in the second attenuator, the attenuation amount setting unit  15  changes the negative output attenuation amount to “0”. This means that, in this example, as shown in  FIG. 3C , the attenuation amount setting unit  15  sets the output attenuation amount “0” to the second attenuator corresponding to PortD. 
     Thus, when the negative output attenuation amount is changed to “0”, the attenuation amount setting unit  15  causes the notification unit  17  to notify the corresponding port. For example, the attenuation amount setting unit  15  lights the LED which is arranged corresponding to PortD. 
       FIGS. 4A, 4B, and 4C  collectively show an example in which the cable loss stored in the loss table contains a negative amount. Specifically, if the amplifier is placed between the output port and the cable, between the cables, or between the cable and the devices under test, the cable loss is set to a negative value. 
     In  FIG. 4A , the cable loss of each PortA to PortD stored in the loss table with respect to the measurement frequency is defined as “−4”, “−3”, “2”, and “11”. The attenuation amount setting unit  15  sets a reference attenuation amount obtained by subtracting the maximum cable loss “11” from the target attenuation amount to the first attenuator  11 . 
     Further, the attenuation amount setting unit  15  sets the output attenuation amounts “15”, “14”, “9”, and “0” obtained by subtracting the cable loss of each PortA to PortD stored in the loss table from the maximum cable loss to each PortA to PortD the corresponding second attenuator. In this case, the output attenuation amounts “15”, “14”, and “9” set in the second attenuator corresponding to each PortA to PortC exceed the specified amount “8”. 
     When a plurality of output attenuation amounts exceed the specified amount in this way, the attenuation amount setting unit  15  corrects the reference attenuation amount with the correction attenuation amount “7” obtained by subtracting the specified amount “8” from the maximum amount “15” of the output attenuation amount exceeding the specified amount, and sets the reference attenuation amount to the first attenuator  11 . This means that the attenuation amount setting unit  15  adds the correction attenuation amount to the reference attenuation amount set in the first attenuator  11 . 
     Further, as shown in  FIG. 4B , the attenuation amount setting unit  15  recalculates the output attenuation amount by subtracting the correction attenuation amount “7” from the maximum cable loss “11”. This means that the maximum cable loss is “4”, and the output attenuation amounts set in the second attenuators corresponding to each PortA to PortD are “8”, “7”, “2”, and “−7”. However, since a negative output attenuation amount cannot be set in the second attenuator, the attenuation amount setting unit  15  sets the output attenuation amount “0” to the second attenuator corresponding to the PortD, as shown in  FIG. 4C . 
     The attenuation amount setting operation of the signal generator  1  according to the embodiment of the present invention configured as described above will be described with reference to  FIG. 5 . 
     First, in step S 1 , the attenuation amount setting unit  15  calculates a reference attenuation amount obtained by subtracting the maximum cable loss of the cable loss of each effective port stored in the loss table from the target attenuation amount with respect to the measurement frequency. After executing the process of step S 1 , the attenuation amount setting unit  15  executes the process of step S 2 . 
     In step S 2 , the attenuation amount setting unit  15  calculates the output attenuation amount obtained by subtracting the cable loss of each effective port stored in the loss table from the maximum cable loss. After executing the process of step S 2 , the attenuation amount setting unit  15  executes the process of step S 3 . 
     In step S 3 , the attenuation amount setting unit  15  determines whether or not there is an output attenuation amount exceeding the specified amount. If it is determined that there is no output attenuation amount exceeding the specified amount, the attenuation amount setting unit  15  executes the process of step S 11 . If it is determined that there is an output attenuation amount exceeding the specified amount, the attenuation amount setting unit  15  executes the process of step S 4 . 
     In step S 4 , the attenuation amount setting unit  15  calculates a correction attenuation amount obtained by subtracting the specified amount from the maximum amount of the output attenuation amount exceeding the specified amount. After executing the process of step S 4 , the attenuation amount setting unit  15  executes the process of step S 5 . 
     In step S 5 , the attenuation amount setting unit  15  corrects the reference attenuation amount with the correction attenuation amount. After executing the process of step S 5 , the attenuation amount setting unit  15  executes the process of step S 6 . In step S 6 , the attenuation amount setting unit  15  corrects the maximum cable loss by subtracting the correction attenuation amount from the maximum cable loss. After executing the process of step S 6 , the attenuation amount setting unit  15  executes the process of step S 7 . 
     In step S 7 , the attenuation amount setting unit  15  recalculates the output attenuation amount by subtracting the cable loss of each effective port stored in the loss table from the corrected maximum cable loss. After executing the process of step S 7 , the attenuation amount setting unit  15  executes the process of step S 8 . 
     In step S 8 , the attenuation amount setting unit  15  determines whether or not there is a negative output attenuation amount. If it is determined that there is a negative output attenuation amount, the attenuation amount setting unit  15  executes the process of step S 9 . If it is determined that there is no negative output attenuation amount, the attenuation amount setting unit  15  executes the process of step S 11 . 
     In step S 9 , the attenuation amount setting unit  15  changes the negative output attenuation amount to 0. After executing the process of step S 9 , the attenuation amount setting unit  15  executes the process of step S 10 . 
     In step S 10 , the attenuation amount setting unit  15  causes the notification unit  17  to notify the output port in which the output attenuation amount is changed to 0. After executing the process of step S 10 , the attenuation amount setting unit  15  executes the process of step S 11 . 
     In step S 11 , the attenuation amount setting unit  15  sets the reference attenuation amount to the first attenuator  11 . Step S 11  corresponds to the first setting step. After executing the process of step S 11 , the attenuation amount setting unit  15  executes the process of step S 12 . 
     In step S 12 , the attenuation amount setting unit  15  sets each output attenuation amount to the corresponding second attenuator. Step S 12  corresponds to the second setting step. After executing the process of step S 12 , the attenuation amount setting unit  15  ends the attenuation amount setting operation. 
     As shown in  FIGS. 3B and 4B , the factor that causes the negative output attenuation amount lies in the fact that the difference between the maximum amount and the minimum amount of the cable loss stored in the loss table corresponding to the effective port exceeds the specified amount. 
     Therefore, the attenuation amount setting unit  15  may confirm that the difference between the maximum amount and the minimum amount of the cable loss corresponding to the effective port does not exceed the specified amount, at a predetermined timing before setting the attenuation amount of the first attenuator  11  and the second attenuators  14   a  to  14   f.    
     The predetermined timing, including when the loss table is changed, when the elements of the loss table are changed, when the measurement frequency is changed, when the effective port is changed, and the like, can be determined based on the test scenario controlled by the computer device  2 . 
     When the difference between the maximum amount and the minimum amount of the cable loss corresponding to the effective port exceeds the specified amount, the attenuation amount setting unit  15  causes the notification unit  17  to notify the port until the difference between the maximum amount and the minimum amount of the cable loss corresponding to the effective port does not exceed the specified amount. 
     For example, the attenuation amount setting unit  15  may light the LED arranged in correspondence to the port having the maximum amount of cable loss, may light the LED arranged in correspondence to the port having the minimum amount of cable loss, and may light the LEDs arranged in correspondence to the ports having the maximum amount and the minimum amount of the cable loss. 
     Further, when lighting the LEDs arranged in correspondence to the ports where the cable loss is the maximum amount and the minimum amount, the attenuation amount setting unit  15  may change the emission color of the LEDs depending on whether the cable loss is the maximum amount or the minimum amount. 
     In this way, since the attenuation amount setting unit  15  confirms the loss table in advance, the processing in the case that the output attenuation amount exceeds the specified amount corresponding to the allowable attenuation amount of the second attenuators  14   a  to  14   f,  which is, steps S 3  to S 10  of the attenuation amount setting operation of the signal generator  1  described with reference to  FIG. 5  can be omitted. 
     As described above, in the present embodiment, since the attenuation amounts of the first attenuator  11  and the second attenuators  14   a  to  14   f  are set in consideration of the loss of the cables  4   a  to  4   f  connected to the output ports  12   a  to  12   f,  it is possible to suppress the variation in the intensity of the test signals inputted to the devices under test  3   a  to  3   f  connected to the output ports  12   a  to  12   f,  respectively. 
     Further, in the present embodiment, the test signal in which the variation in intensity is suppressed can be inputted in parallel to the devices under test  3   a  to  3   f  connected to the output ports  12   a  to  12   f,  respectively, so that the test time can be shortened. 
     Further, in the present embodiment, by setting a specified amount within a range not exceeding the allowable attenuation amount of the second attenuators  14   a  to  14   f,  it is possible to prevent a test signal having an unexpected intensity from being inputted to each of the devices under test  3   a  to  3   f.    
     Further, in the present embodiment, since when any one of the output attenuation amounts becomes negative as a result of recalculating the output attenuation amount, the output attenuation amount is set to 0, it is possible to prevent a negative output attenuation amount that cannot be set to the second attenuators  14   a  to  14   f  from being set to the second attenuators  14   a  to  14   f    
     Further, in the present embodiment, since the notification unit  17  is caused to notify the information on the output port corresponding to the second attenuator in which the output attenuation amount is changed to 0, it is possible to notify the output port to which the cable having too large loss is connected. 
     In the present embodiment, an example in which the signal generator  1  and the computer device  2  are separately configured has been described, but in the signal generator of the present invention, the signal generator  1  and the computer device  2  may be integrally configured. 
     Although the embodiments of the present invention have been disclosed above, it is easy to make changes to the embodiments without departing from the scope of the present invention. Embodiments of the present invention are disclosed on the premise that the equivalents to which such modifications have been made are included in the invention described in the claims. 
     EXPLANATION OF REFERENCE NUMERALS
       1  Signal Generator     3   a - 3   f  Device Under Test     4   a - 4   f  Cable     10  Signal Generation Unit     11  First Attenuator     12   a - 12   f  Output Port     13  Distributor     14   a - 14   f  Second Attenuator     15  Attenuation Amount Setting Unit     16  Cable Loss Storage Unit     17  Notification Unit