Patent Publication Number: US-2019179001-A1

Title: Radar device for object identification

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of German Patent Application No. 10 2017 222 272.7, filed on 8 Dec. 2017, the entire content of which is incorporated herein by reference. 
     FIELD OF THE DISCLOSURE 
     The disclosure generally relates to the field of object identification and/or limit level monitoring. The disclosure relates in particular to a radar device, such as a limit level radar device, for identifying an object and/or a limit level of a medium. The disclosure further relates to a method for identifying an object, using a radar device, a computer program element and a computer-readable medium. 
     BACKGROUND OF THE DISCLOSURE 
     Radar devices, such as Frequency Modulated Continuous Wave (FMCW) radar sensors, are frequently used for determining a fill level and/or limit level of a medium in a container. Radar devices can also be used for detecting an object and/or a limit level of a medium, it being possible for an echo at a specific location and/or in a specific region to be associated with the object and/or the limit level. If said echo is present, the object can be marked as present and/or the limit level can be marked as reached. In contrast, if said echo is not detected, the object can be marked as not present and/or the limit level can be marked as not reached. In order to detect the echo associated with the object and/or the limit level, existing radar devices or radar sensors calculate a complete echo curve by means of a Fourier transform, in particular by means of fast Fourier transform (FFT), which may be associated with high computational outlay and time expenditure. This may also require high processing power and therefore expensive signal processors and/or microcontrollers. Object identification is also often carried out using a continuous radar, it being possible in this case for all reflecting objects to generate a detection signal at different positions in the measuring range of the continuous radar, with the result that it is not possible to associate a detection signal with the presence of a specific object at a specific position. If a transceiver pair is used, for example in the case of a reflection microwave barrier, two devices are in addition required. 
     SUMMARY 
     An improved radar device for object identification and/or limit level monitoring can advantageously be provided by means of embodiments of the present disclosure. 
     An aspect of the disclosure relates to a radar device and/or a radar sensor for identifying an object. The radar device comprises at least one antenna for transmitting a transmission signal and for receiving a reflected signal, in particular a signal reflected on the object. The radar device further comprises an evaluation circuit that is configured to determine a receiving signal on the basis of the reflected signal. The radar device further comprises a control unit that is configured for evaluating the receiving signal in a frequency portion of the receiving signal, the control unit being configured to determine whether a specified frequency that corresponds to and/or is associated with a specific and/or specified distance of an object from the radar device is contained in the frequency portion of the receiving signal. In this case, the specified frequency may be associated with a reflection of the transmission signal on the object at a specific distance and/or may be caused by said reflection, with the result that, when the specified frequency is present, the radar device can determine whether or not the object is present. 
     The radar device can in general denote a radar sensor for object identification. In particular, the radar device may be a fill level measurement device for determining a fill level of a medium. Alternatively or in addition, the radar device may be a limit level radar device and/or a limit level sensor that is configured for determining a limit level of a medium, for example in a container. The radar device may be configured as an FMCW radar device. Likewise, the receiving signal may be an FMCW receiving signal. Alternatively or in addition, the radar device may be configured as a Stepped Frequency Continuous Wave (SFCW) radar. 
     Furthermore, the radar device may be configured as a limit level radar device for limit level monitoring of a medium, for example in a container, and/or for limit level monitoring of a channel. In other words, the object may be a limit level of a medium. 
     The object may also be a container, and/or the radar device may be configured to detect and/or determine the presence of the container. In general, the object may be any desired object that reflects the transmission signal, for example an object and/or product on a conveyor belt. The radar device may also determine a position of a boom, for example. 
     The radar device according to the disclosure may in particular be configured for examining the receiving signal for the presence of the specified frequency merely and/or exclusively in the frequency portion of the measuring signal. In this case, the frequency portion may be small relative to an overall frequency spectrum of the receiving signal. For example, the frequency portion may be at most 75% of the frequency spectrum, in particular at most 50% of the frequency spectrum, and preferably between 1% and 25% of the frequency spectrum of the receiving signal. Evaluating the receiving signal in the frequency portion means that it is not necessary to evaluate the entire receiving signal by frequency and/or it is not necessary to determine a complete echo curve, but rather the receiving signal can be analysed only at the location and/or only in the frequency portion in which an echo is anticipated, owing to reflection of the transmission signal on the object. The radar device can essentially analyse whether or not the specified frequency is present in the receiving signal. Compared with complete evaluation of the receiving signal or determination of a complete echo curve, computational outlay and/or time expenditure can thus be saved. The radar device according to the disclosure can thus quickly and efficiently determine the presence of the specified frequency and/or the presence of the object. It is also possible, as a result, to dispense with expensive signal processors, control units and/or microcontrollers, and therefore the radar device can be manufactured in a cost-effective manner overall. 
     The specified frequency may be stored in a memory of the radar device, for example, and may be set by a user of the radar device, for example. For example, the radar device may comprise a user interface for inputting user input relating to the distance of the object. The control unit may furthermore be configured to determine the specified frequency in the receiving signal, on the basis of the user input relating to the distance of the object. For this purpose, for example a conversion table for converting distances into frequencies may be stored in the memory of the radar device. Alternatively or in addition, the specified frequency can be input via the user interface. 
     According to an embodiment of the disclosure, the control unit is configured to evaluate the receiving signal in the frequency portion on the basis of a Fourier transform. Alternatively or in addition, the control unit is configured to determine a partial echo curve in the frequency portion of the receiving signal, which partial echo curve is associated with a specific, in particular a specified, distance range from the radar device. For example, for this purpose, a fast Fourier transform (FFT) and/or a discrete Fourier transform (DFT) may be applied to the receiving signal for the frequencies of the frequency portion. 
     According to an embodiment of the disclosure, the control unit is configured to evaluate the receiving signal, for the specified frequency, in the frequency portion on the basis of a Goertzel filter. Alternatively or in addition, the control unit is configured to determine the presence of the specified frequency in the receiving signal using a Goertzel filter. Using a Goertzel filter can make it possible to quickly, efficiently, and reliably check the receiving signal for the presence of the specified frequency and thus for the presence of the object. 
     According to an embodiment of the disclosure, the control unit is configured to dismiss and/or hide all frequencies of the receiving signal outside the frequency portion. The control unit can therefore be configured to evaluate and/or analyse the receiving signal exclusively in the frequency portion. Alternatively or in addition, the control unit may be configured to examine the receiving signal exclusively for the presence of a single specified frequency. As a result, it is not necessary to analyse the receiving signal over the entire frequency spectrum thereof, but instead the presence of the specified frequency can be determined efficiently and quickly. 
     According to an embodiment of the disclosure, the control unit is configured to evaluate the receiving signal in a plurality of frequency portions and to determine whether a specified frequency is contained in the respective frequency portions. In this case, it is possible for the individual frequency portions not to overlap and/or to be mutually separated. As a result, it is possible to quickly and efficiently determine the presence of a plurality of different objects at different distances from the radar device. 
     According to an embodiment of the disclosure, the control unit is configured to emit a control signal and/or switching signal if the specified frequency is contained in the receiving signal. Via the control signal a user can be informed, for example, of the presence of the object. For this purpose, the control signal can be used for example for actuating a signal light. It is also possible for an output to be provided for example on a user interface and/or on a display element, on the basis of the control signal, which output can indicate to the user the presence of the object. 
     A further aspect of the disclosure relates to the use of a Goertzel filter in a radar device for determining the presence of a specified frequency in a receiving signal of the radar device. 
     A further aspect of the disclosure relates to a method for identifying an object using a radar device. The method comprises the following steps:
         transmitting a transmission signal and receiving a reflected signal by means of an antenna of the radar device;   generating, by means of an evaluation circuit of the radar device, a receiving signal, on the basis of the reflected signal; and   evaluating, by means of a control unit of the radar device, a frequency portion of the receiving signal while determining the presence, in the frequency portion, of a specified frequency that corresponds to a specific distance of an object from the radar device.       

     Features, elements and/or properties of the radar device, as described above and in the following, may be features, elements and/or steps of the method, as described above and in the following, and vice versa. In other words, any disclosure with respect to one aspect of the disclosure essentially applies for all other aspects of the disclosure. 
     A further aspect of the disclosure relates to a computer program element which, when executed on a control unit of a radar device, prompts the radar device to carry out the steps of the method, as described above and in the following. 
     A further aspect of the disclosure relates to a computer-readable medium and/or storage medium on which a computer program element is stored which, when executed on a control unit of a radar device, prompts the radar device to carry out the steps of the method, as described above and in the following. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the disclosure will be described in the following, with reference to the accompanying drawings. In this case, the same reference signs may denote identical, identically functioning or similar elements. 
         FIG. 1  shows a radar device according to an embodiment of the disclosure. 
         FIG. 2A  shows a radar device according to an embodiment of the disclosure. 
         FIG. 2B  shows an echo curve determined using the radar device  10  of  FIG. 2A . 
         FIG. 3  is a flow diagram for illustrating steps of a method for identifying an object according to an embodiment of the disclosure. 
     
    
    
     The illustrations in the figures are merely schematic and are not to scale. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a radar device  10  according to an embodiment of the disclosure. The radar device  10  is in particular configured for identifying an object  12 , which is located at a distance  13  from the radar device  10  and/or is arranged at a spacing  13  from the radar device  10 . In this case, the object  12  can in particular be a limit level of a medium, for example in a container, and/or a limit level of a channel. However, the object  12  can also be any other object. 
     The radar device  10  comprises an antenna  14  for transmitting and/or sending a transmission signal, a radar-based transmission signal, and/or a radar signal. The antenna  14  is furthermore configured for receiving a reflected signal and/or reflection signal. In order to generate the transmission signal, the radar device  10  may comprise a radar module for example. 
     The radar device  10  may in particular be configured as an FMCW radar  10 . A frequency of the transmission signal can therefore be increased in a ramp-like manner, during a measurement cycle, from a starting frequency to an end frequency. In other words, the radar device  10  may be configured to pass through a frequency ramp when transmitting the transmission signal. 
     The radar device  10  further comprises an evaluation circuit  16  that is coupled to the antenna  14  and is configured to determine a receiving signal on the basis of the reflected signal. For this purpose, the evaluation circuit  16  may for example comprise a frequency mixer  16   a  that is configured to generate an intermediate-frequency signal on the basis of the transmission signal and/or the reflected signal. The evaluation circuit  16  may also comprise an intermediate-frequency amplifier  16   b  for amplifying the intermediate-frequency signal. The evaluation circuit  16  may also comprise a scanning unit  16   c  for scanning and/or digitising the intermediate-frequency signal and/or the amplified intermediate-frequency signal. The receiving signal can therefore generally denote a measuring signal that correlates with the intermediate-frequency signal and/or the reflected signal. For example, the receiving signal may denote the scanned intermediate-frequency signal and/or correlate thereto. 
     The radar device  10  further comprises a control unit  18  that is coupled to the evaluation circuit  16  and is configured to evaluate, analyse, and/or process the receiving signal and/or a portion of the receiving signal. The control unit  18  may, for example, denote and/or comprise a control circuit, a processor, a logic means, a data processing means, a signal processor, and/or a microcontroller. 
     The control unit  18  is configured to determine whether a specified frequency  17  (see  FIGS. 2A and 2B ) that corresponds to and/or is associated with the distance  13  is contained in a frequency portion  15 . 
     The radar device  10  may for example comprise a user interface  20  by means of which a user can perform a user input. In this case, the user interface may comprise any desired actuation element  21  and/or operating element  21  and/or a touchscreen display  21 , for example. The user input may be and/or correlate with the distance  13  of the object  12 , for example. Alternatively or in addition, the user can input the specified frequency  17  via the user interface  20 . The specified frequency  17  can then be converted into the distance  13 , for example, using a conversion table stored in a memory  23  of the radar device  10 . The distance  13  itself and/or the specified frequency  17  may also be stored in the memory  23 . 
     The control unit  18  is configured to evaluate the receiving signal on the basis of a Fourier transform. In order that the receiving signal can be quickly and efficiently examined for the presence of the specified frequency  17  in the frequency portion  15  of the receiving signal, the control unit  18  may comprise a Goertzel filter  18   a  and/or may evaluate the receiving signal using a Goertzel filter  18   a . In this case, the Goertzel filter  18   a  may correspond to and/or be used for the calculation of a single frequency component  15 ,  17 , for example a FFT. This can be calculated more quickly than an entire echo curve, only a reflection on the object  12  at the distance  13  being evaluated. All other reflections and/or frequencies outside the frequency portion  15  can be hidden. The control unit  18  can therefore carry out a Fourier transform only in the frequency portion  15 , selectively and/or for the specified frequency  17 . Essentially, the control unit  18  can be configured to determine only a partial echo curve  19  (see  FIGS. 2A and 2B ), on the basis of the receiving signal. In this case, the partial echo curve  19  may take place in the spatial region that corresponds to the frequency portion  15  and in which the object  12  is to be expected. In other words, the control unit  18  can analyse the receiving signal only at the location or region in which an echo and/or a reflection from the object  12  is expected, on the basis of the test as to whether or not the specified frequency  17  is present in the receiving signal. The radar device  10  can thus carry out the object identification efficiently and quickly. 
     In general, however, the radar device  10  may also be configured for determining a specified frequency  17  in each case in a plurality of frequency portions  15 , in order to thus determine the presence of a plurality of different objects  12  at different distances  13 . For this purpose, the radar device  10  may comprise a plurality of Goertzel filters  18   a  which may differ with respect to the frequencies that can be determined thereby. 
     Once the control unit  18  has determined the specified frequency  17  in the frequency portion  15 , the control unit  18  can then generate and/or emit a control signal and/or switching signal, for example by means of a display element  23  of the user interface  20 . 
     A computer program element, for example software instructions, may furthermore be stored in the memory  23 , which instructions, when executed on the control unit  18 , prompt the radar device  10  to analyse the receiving signal for the presence of the specified frequency  17 . 
     In principle, the radar device  10  can be used for monitoring the object  12  at the specific distance  13  and it is possible to determine whether or not the object  12  is present. Alternatively or in addition, the radar device  10  may be used for monitoring a gap between the radar device  10  and a fixed, reflecting object, such as a wall. It is thus possible to check whether or not the gap is clear. 
       FIG. 2A  shows a radar device  10  according to an embodiment of the disclosure. Unless otherwise described, the radar device  10  of  FIG. 2A  comprises the same elements and features as the radar device  10  of  FIG. 1 .  FIG. 2B  shows a (hypothetical) echo curve  30  determined using the radar device  10  of  FIG. 2A , which curve represents the intensity of the receiving signal as a function of the distance and/or the frequency. 
     In the example shown in  FIGS. 2A and 2B , an interfering object  25  is located between the object  12  or the object  12  to be identified and the radar device  10 . In addition to the reflection on the object  12  to be identified, the transmission signal is also reflected on the interfering object  25  at least in part. The reflection on the interfering object  25  therefore results in an interfering reflection  27  in the echo curve  30 . 
     In order to quickly determine the presence of the object  12 , the radar device  10  is configured to determine the partial echo curve  19  merely and/or exclusively in the frequency portion  15  in which the specified frequency  15  associated with the object  12  is contained, as described above with respect to  FIG. 1 . All other frequency portions of the receiving signal can be dismissed by the control unit  18 . The overall echo curve  30  shown in  FIG. 2B  therefore shows an echo curve  30  determined only hypothetically by the radar device  10 . 
       FIG. 3  is a flow diagram for illustrating steps of a method for identifying an object  12  using a radar device  10  according to an embodiment of the disclosure. The method may denote a method for operating the radar device  10 . 
     In a first step S 1 , a transmission signal is transmitted and a reflected signal is received by means of an antenna  14  of the radar device  10 . In a further step S 2 , a receiving signal is generated by means of an evaluation circuit  16  of the radar device  10 , on the basis of the reflected signal. In a further step S 3 , a frequency portion  15  of the receiving signal is evaluated by means of a control unit  18  of the radar device  10 . In a further step S 4 , the presence of a specified frequency  17  in the frequency portion  15  is determined, which frequency corresponds to and/or is associated with a distance  13  of an object  12  from the radar device  10 . 
     In addition, it should be noted that “comprising” does not exclude any other elements or steps, and “a” or “one” does not exclude a plurality. It is furthermore noted that features or steps that have been described with reference to one of the above embodiments can also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered limiting.