Patent Publication Number: US-2022221567-A1

Title: Electronic device, method for controlling electronic device, and program

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent. Application No. 2019-100698 filed in Japan on May 29, 2019, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an electronic device, a method for controlling an electronic device, and a program. 
     BACKGROUND ART 
     For example, in fields such as automobile-related industries, a technology for measuring a distance or the like between a vehicle of interest and a predetermined object is regarded as important. Recently, various studies have been conducted particularly on a radar (Radio Detecting and Ranging) technology for measuring a distance or the like to an object such as an obstacle by transmitting a radio wave such as a millimeter wave and receiving a reflected wave reflected off the object. Such a technology for measuring a distance or the like expectedly becomes more important in the future with progresses of a technology for assisting drivers in driving and a technology related to automated driving for partially or entirely automating driving. 
     Various suggestions have been made in relation to a technology for detecting the presence of a predetermined object by receiving a reflected wave of a radio wave that s been transmitted and reflected off the object. For example, PTL 1 discloses an FM-CW radar device. The FM-CW radar device performs linear frequency modulation (E14) on a transmission signal at a particular period, and radiates the transmission signal toward a target object. The FM-CW radar device then detects a beat signal on the basis of a difference between the transmission signal and a reception signal from the target object, and measures a distance and/or a velocity through frequency analysis of this signal. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 11-133144 
     SUMMARY OF INVENTION 
     In one embodiment, an electronic device includes a transmission antenna that transmits a transmission wave, a reception antenna that receives a reflected wave that is the transmission wave having been reflected, and a control unit. 
     The control unit detects a target by using a constant false alarm rate, based on a transmission signal transmitted. as the transmission wave and a reception signal received as the reflected wave. 
     The control unit establishes reference regions on a far side in a distance direction with respect to a test region in a distribution of signal intensities based on the reception signal in the distance direction, and sets a threshold for use in detection of the target, based on an order statistic among the signal intensities in the reference regions. 
     In one embodiment, a method for controlling an electronic device includes steps as follows: 
     (1) a step of transmitting a transmission wave from a transmission antenna; 
     (2) a step of receiving, from a reception antenna, a reflected wave teat is the transmission wave having been reflected; 
     (3) a step of detecting a target by using a constant false alarm rate, based on a transmission signal transmitted. as the transmission wave and a reception signal received as the reflected wave; 
     (4) a step of establishing reference regions on a far side in a distance direction with respect to a test region in a distribution of signal intensities based on the reception signal in the distance direction; and 
     (5) a step of setting a threshold for use in detection of the target, based on an order statistic among the signal intensities in the reference regions. 
     In one embodiment, a program causes a computer to perform the steps (1) to (5) above. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram for describing how an electronic device according to one embodiment is used. 
         FIG. 2  is a functional block diagram schematically illustrating a configuration of the electronic device according to the one embodiment. 
         FIG. 3  is a diagram for describing a configuration of a transmission signal according to the one embodiment. 
         FIG. 4  is a diagram for describing processing blocks in a control unit according to the one embodiment. 
         FIG. 5  is a diagram for describing an example in which the electronic device according to the one embodiment performs OS-CFER processing. 
         FIG. 6  is a diagram for describing the example in which the electronic device according to the one embodiment performs the OS-CFER processing. 
         FIG. 7  is a diagram for describing an example of processing of the control unit according to the one embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The target detection accuracy is desirably improved in a technology for detecting a predetermined object by receiving a reflected wave that is a transmitted transmission wave reflected off the object. An object of the present disclosure is to provide an electronic device, method for controlling an electronic device, and a program that can improve the target detection accuracy. According to one embodiment, an electronic device, a method for controlling an electronic device, and a program that can improve the target detection accuracy can be provided. One embodiment is described in detail below with reference to the drawings. 
     An electronic device according to one embodiment is mounted in a vehicle (mobility device) such as an automobile, for example, and thus is capable of detecting, as a target, a predetermined object located around the mobility device. To this end, the electronic device according to the one embodiment is capable of transmitting a transmission wave to an area around the mobility device from a transmission antenna installed on the mobility device. The electronic device according to the one embodiment is also capable of receiving a reflected wave that is the transmission wave having been reflected, from a reception antenna installed on the mobility device. At least one of the transmission antenna and the reception antenna may be included in a radar sensor or the like installed on the mobility device, for example. 
     A configuration in which the electronic device according to the one embodiment is mounted in an automobile such as a passenger car is described below as a typical example. However, the mobility device in which the electronic device according to the one embodiment is mounted is not limited to an automobile. The electronic device according to the one embodiment may be mounted in various mobility devices such as a bus, a taxi, a truck, motorcycle, a bicycle, a ship, an aircraft, a helicopter, a farm vehicle such as a tractor, a snowplow, a garbage truck, a police car, an ambulance, and a drone. The mobility device in which the electronic device according to the one embodiment is mounted is not necessarily limited to a mobility device that moves by its own motive power. For example, the mobility device in which the electronic device according to the one embodiment is mounted may be a trailer towed by a tractor. The electronic device according to the one embodiment is capable of measuring a distance or the like between the sensor and a predetermined object when at least one of the sensor and the object is movable. The electronic device according to the one embodiment is also capable of measuring the distance or the like between the sensor and the object even when both the sensor and the object are stationary. 
     An example of how the electronic device according to the one embodiment detects an object is described first. 
       FIG. 1  is a diagram for describing how the electronic device according to the one embodiment is used.  FIG. 1  illustrates an example in which a sensor including a transmission antenna and a reception antenna according to the one embodiment is installed on a mobility device. 
     A sensor  5  including a transmission antenna and a reception antenna according to the one embodiment is installed on a mobility device  100  illustrated in  FIG. 1 . It is assumed that an electronic device  1  according to the one embodiment is also mounted (for example, built) in the mobility device  100  illustrated in  FIG. 1 . A specific configuration of the electronic device  1  is described later. The sensor  5  may include at least one of the transmission antenna and the reception antenna, for example. The sensor  5  may also appropriately include at least any of other functional units, such as at least part of a control unit  10  ( FIG. 2 ) included in the electronic device  1 . The mobility device  100  illustrated in  FIG. 1  may be an automotive vehicle such as a passenger car but may be a mobility device of any type. In  FIG. 1 , the mobility device  100  may move (travel or slowly travel), for example, in a positive Y-axis direction (traveling direction) illustrated in  FIG. 1  or in another direction, or may be stationary without moving. 
     As illustrated in  FIG. 1 , the sensor  5  including the transmission antenna is installed on the mobility device  100 . In the example illustrated in  FIG. 1 , only one sensor  5  including the transmission antenna and the reception antenna is installed at a front portion of the mobility device  100 . The position where the sensor  5  is installed on the mobility device  100  is not limited to the position illustrated in  FIG. 1  and may be another appropriate position. For example, the sensor  5  illustrated in  FIG. 1  may be installed on a left side, on a right side, and/or at a rear portion of the mobility device  100 . The number of such sensors  5  may be any number equal to or greater than 1 depending on various conditions (or requirements) such as a range and/or an accuracy of measurement performed by the mobility device  100 . The sensor  5  may be installed inside the mobility device  100 . The inside the mobility device  100  may be, for example, a space inside a bumper, a space inside a body, a space inside a headlight, or a space such as a driver&#39;s space. 
     The sensor  5  transmits an electromagnetic wave as a transmission wave from the transmission antenna. For example, when a predetermined object (for example, an object  200  illustrated in  FIG. 1 ) is located around the mobility device  100 , at least part of the transmission wave transmitted from the sensor  5  is reflected off the object to become a reflected wave. For example, the reception antenna of the sensor  5  receives such a reflected wave. In this manner, the electronic device  1  mounted in the mobility device  100  can detect the object as the target. 
     The sensor  5  including the transmission antenna may be typically a radar (Radio Detecting and Ranging) sensor that transmits and receives a radio wave. However, the sensor  5  is not limited to a radar sensor. The sensor  5  according to the one embodiment may be, for example, a sensor based on the LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) technology that uses an optical wave. Each of these sensors can include, for example, a patch antenna. Since the technologies such as RADAR and LIDAR are already known, detailed description may be appropriately simplified or omitted. 
     The electronic device  1  mounted in the mobility device  100  illustrated in  FIG. 1  receives, from the reception antenna, the reflected wave of the transmission wave transmitted from the transmission antenna of the sensor  5 . In this manner, the electronic device  1  can detect, as the target, the predetermined object  200  located within a predetermined distance from the mobility device  100 . For example, as illustrated in  FIG. 1 , the electronic device  1  can measure a distance L between the mob mobility device  100 , which is a vehicle of interest, and the predetermined object  200 . The electronic device  1  can also measure a relative velocity between the mobility device  100 , which is the vehicle of interest, and the predetermined object  200 . The electronic device  1  can further measure a direction (an angle of arrival θ) from which the reflected wave from the predetermined object  200  arrives at the mobility device  100 , which is the vehicle of interest. 
     The object  200  may be, for example, at least any of an oncoming automobile traveling in a lane adjacent to a lane of the mobility device  100 , an automobile traveling side by side with the mobility device  100 , an automobile traveling in front of or behind the mobility device  100  in the same lane, and the like. The object  200  may also be any object located around the mobility device  100 , such as a motorcycle, a bicycle, a stroller, a person such as a pedestrian, an animal, an insect, other forms of life, a guardrail, a median strip, a road sign, a step on a sidewalk, a wall, a manhole, or an obstacle. The object  200  may be in motion or stationary. For example, the object  200  may be an automobile or the like that is parked or stationary around the mobility device  100 . 
     In  FIG. 1 , a ratio between a size of the sensor  5  and a size of the mobility device  100  does not necessarily indicate an actual ratio.  FIG. 1  illustrates the sensor  5  that is installed on an outer portion of the mobility device  100 . However, the one embodiment, the sensor  5  may be installed at various positions of the mobility device  100 . 
     For example, in one embodiment, the sensor  5  may be installed inside a bumper of the mobility device  100  so as not to be seen in the appearance of the mobility device  100 . 
     Description is given below on the assumption that the transmission antenna of the sensor  5  transmits a radio wave in a frequency band, such as a millimeter wave (equal to or higher than 30 GHz) or a quasi-millimeter wave (for example, around 20 GHz to 30 GHz) as a typical example. For example, the transmission antenna of the sensor  5  may transmit a radio wave having a frequency bandwidth of 4 GHz such as from 77 GHz to 81 GHz. 
       FIG. 2  is a functional block diagram schematically illustrating an example of a configuration of the electronic device  1  according to the one embodiment. An example of the configuration of the electronic device  1  according to the one embodiment is described below. 
     When a distance or the like is measured by using a millimeter-wave radar, a frequency-modulated continuous wave radar (hereinafter, referred to as an FMCW radar) is often used. The FMCW radar sweeps a frequency of a to-be-transmitted radio wave to generate a transmission signal. Thus, a frequency of the radio wave used by such a millimeter-wave FMCW radar, which uses a radio wave of a frequency band of 79 GHz, for example, has a frequency bandwidth of 4 GHz such as from 77 GHz to 81 GHz, for example. The radar of the frequency bandwidth of 79 GHz has a characteristic that the usable frequency bandwidth is wider than another millimeter-wave and/or quasi-millimeter-wave radar of a frequency band of 24 GHz, 60 GHz, or 76 GHz, for example. Such an embodiment is described below as an example. 
     As illustrated in  FIG. 2 , the electronic device  1  according to the one embodiment is constituted by the sensor  5  and an ECU (Electronic Control Unit)  50 . The ECU  50  controls various operations of the mobility device  100 . The ECU  50  may be constituted by at least one or more ECUs. The electronic device  1  according to the one embodiment includes the control unit  10 . The electronic device  1  according to the one embodiment may also appropriately include another functional unit such as at least any of a transmission unit  20 , reception units  30 A to  30 D, and a storage unit  40 . As illustrated in  FIG. 2 , the electronic device  1  may include a plurality of reception units such as the reception units  30 A to  30 D. When the reception units  30 A,  30 B,  30 C, and  30 D are not distinguished from one another, the reception units  30 A,  30 B,  30 C, and  30 D are simply referred to as “reception units  30 ” below. 
     The control unit  10  may include a distance FFT processing unit  11 , a distance detection determining unit  12 , a velocity FFT processing unit  13 , a velocity detection determining unit  14 , an angle-of-arrival estimating unit  15 , and an object detecting unit  16 . These functional units included in the control unit  10  are further described later. 
     As illustrated in  FIG. 2 , the transmission unit  20  may include a signal generating unit  21 , a synthesizer  22 , phase control units  23 A and  23 B, amplifiers  24 A and  24 B, and transmission antennas  25 A and  25 B. When the phase control units  23 A and  23 B are not distinguished from each other, the phase control units  23 A and  23 B are simply referred to as “phase control units  23 ” below. When the amplifiers  24 A and  24 B are not distinguished from each other, the amplifiers  24 A and  24 B are simply referred to as “amplifiers  24 ” below. When the transmission antennas  25 A and  25 B are not distinguished from each other, the transmission antennas  25 A and  25 B are simply referred to as “transmission antennas  25 ” below. 
     As illustrated in  FIG. 2 , each of the reception units  30  may include a respective one of reception antennas  31 A to  31 D. When the reception antennas  31 A,  31 B,  31 C, and  31 D are not distinguished from one another, the reception antennas  31 A,  31 B,  31 C, and  31 D are simply referred to as “reception antennas  31 ” below. As illustrated in  FIG. 2 , each of the plurality of reception units  30  may include an LNA  32 , a mixer  33 , an IF unit  34 , and an AD conversion unit  35 . The reception units  30 A to  30 D may have the same and/or similar configuration.  FIG. 2  schematically illustrates the configuration of only the reception unit  30 A as a representative example. 
     The sensor  5  described above may include, for example, the transmission antennas  25  and the reception antennas  31 . The sensor  5  may also appropriately include at least any of other functional units such as the control unit  10 . 
     The control unit  10  included in the electronic device  1  according to the one embodiment is capable of controlling the individual functional units of the electronic device  1  and also controlling operations of the entire electronic device  1 . To provide control and processing capabilities for executing various functions, the control unit  10  may include at least one processor, for example, a CPU (Central Processing Unit). The control unit  10  may be collectively implemented by one processor, may be implemented by some processors, or may be implemented by discrete individual processors. The processor may be implemented as one integrated circuit. The integrated circuit is also referred to as an IC. The processor may be implemented as a plurality of integrated circuits and discrete circuits connected to be able to perform communication. The processor may be implemented on the basis of various other known technologies. In the one embodiment, the control unit  10  may be configured as, for example, a CPU and a program executed by the CPU. The control unit  10  may appropriately include a memory required for operations of the control unit  10 . 
     The storage unit  40  may store a program executed in the control unit  10 , results of processing performed by the control unit  10 , etc. The storage unit  40  m function as a work memory of the control unit  10 . The storage unit  40  may be constituted, for example, by a semiconductor memory or a magnetic disk. However, the storage unit  40  is not limited to these, and can be any storage device. The storage unit  40  may be, for example, a storage medium such as a memory card inserted to the electronic device  1  according to the present embodiment. The storage unit  40  may be an internal memory of the CPU used as the control unit  10  as described above. 
     In the one embodiment, the storage unit  40  may store various parameters for setting a range in which an object is detected on the basis of a transmission wave T transmitted from each transmission antenna  25  and a reflected wave R received from each reception antenna  31 . 
     In the electronic device  1  according to the one embodiment, the control unit  10  is capable of controlling at least one of the transmission unit  20  and the reception units  30 . In this case, the control unit  10  may control at least one of the transmission unit  20  and the reception. units  30  on the basis of various kinds of information stored in the storage unit  40 . In the electronic device  1  according to the one embodiment, the control unit.  10  may instruct the signal generating unit  21  to generate a signal or may control the signal generating unit  21  to generate a signal. 
     In accordance with control performed by the control unit  10 , the signal generating unit  21  generates a signal (transmission signal) to be transmitted as the transmission wave T from each of the transmission antennas  25 . When generating the transmission signal, the signal generating unit  21  may allocate a frequency of the transmission signal in accordance with control performed by the control unit  10 , for example. Specifically, the signal generating unit  21  may allocate a frequency of the transmission signal in accordance with a parameter set by a parameter setting unit  16 . For example, the signal generating unit  21  receives frequency information from the control unit  10  (the parameter setting unit  16 ) and generates a signal having a predetermined frequency in a frequency band such as from 77 GHz to 81 GHz, for example. The signal generating unit  21  may include a functional unit serving as a voltage control oscillator (VCO), for example. 
     The signal generating unit  21  may be configured as hardware having the function, as for example a microcomputer, or as for example a processor such as a CPU and a program or the like executed by the processor. Each functional unit described below may also be configured as hardware having the function, as for example a microcomputer if possible, or as for example a processor such as a CPU or a program or the like executed by the processor. 
     In the electronic device  1  according to the one embodiment, the signal generating unit  21  may generate a transmission signal (transmission chirp signal) such as a chirp signal, for example. In particular, the signal generating unit  21  may generate a signal (linear chirp signal) whose frequency changes linearly and periodically. For example, the signal generating unit  21  may generate a chirp signal whose frequency linearly and periodically increases from 77 GHz to 81 GHz as time elapses. For example, the signal generating unit  21  may generate a signal whose frequency periodically repeats a linear increase (up-chirp) from 77 GHz to 81 GHz and a decrease (down-chirp) as time elapses. The signal to be generated by the signal generating unit  21  may be set in advance by the control unit  10 , for example. The signal generated by the signal generating unit  21  may be stored in advance in the storage unit  40  or the like, for example. Since chirp signals used in a technical field such as a radar are known, more detailed description is appropriately simplified or omitted. The signal generated by the signal generating unit  21  is supplied to the synthesizer  22 . 
       FIG. 3  is a diagram for describing an example of chirp signals generated by the signal generating unit  21 . 
     In  FIG. 3 , the horizontal axis represents an elapse of time, and the vertical axis represents a frequency. In the example illustrated in  FIG. 3 , the signal generating unit  21  generates linear chirp signals whose frequency linearly changes periodically. In  FIG. 3 , the individual chirp signals are denoted by c 1 , c 2 , . . . , c 8 . As illustrated in  FIG. 3 , the frequency of each chirp signal linearly increases as time elapses. 
     In the example illustrated in  FIG. 3 , eight chirp signals c 1 , c 2 , . . . , c 8  constitute one subframe. That is, each of subframes such as a subframe  1  and a subframe  2  illustrated in  FIG. 3  includes eight chirp signals cl, c 2 , . . . , c 8 . In the example illustrated in  FIG. 3, 16  subframes such as the subframes  1  to  16  constitute one frame. That is, each of frames such as a frame  1  and a frame  2  illustrated in.  FIG. 3  includes  16  subframes. As illustrated in  FIG. 3 , a frame interval of a predetermined length may be included between frames. One frame illustrated in  FIG. 3  may have a length of about 30 ms to 50 ms, for example. 
     In  FIG. 3 , the frame  2  and subsequent frames may have the same and/or similar configuration. In  FIG. 3 , the frame  3  and subsequent frames may have the same and/or similar configuration. In the electronic device  1  according to the one embodiment, the signal generating unit  21  may generate a transmission signal as any number of frames. In  FIG. 3 , an illustration of some chirp signals is omitted. As described above, a relationship between time and a frequency of the transmission signal generated by the signal generating unit  21  may be stored in the storage unit  40  or the like, for example. 
     As described above, the electronic device  1  according to the one embodiment may transmit a transmission signal constituted by subframes each including a plurality of chirp signals. The electronic device  1  according to the one embodiment may transmit a transmission signal constituted by frames each including a predetermined number of subframes. 
     Description is given below on the assumption that the electronic device  1  transmits a transmission signal having a frame structure illustrated in  FIG. 3 . However, the frame structure illustrated in  FIG. 3  is an example. For example, the number of chirp signals included in one subframe is not limited to eight. In the one embodiment, the signal generating unit  21  may generate a subframe including any number (for example, a plurality) of chirp signals. A subframe structure illustrated in  FIG. 3  is an example. For example, the number of subframes included in one frame is not limited to  16 . In the one embodiment, the signal generating unit  21  may generate a frame including any number (for example, a plurality) of subframes. The signal generating unit  21  may generate signals having different frequencies. The signal generating unit  21  may generate a plurality of discrete signals of bandwidths in which frequencies f are different from each other. 
     Referring back to  FIG. 2 , the synthesizer  22  increases the frequency of the signal generated by the signal generating unit  21  to a frequency in a predetermined frequency band. The synthesizer  22  may increase the frequency of the signal generated by the signal generating unit  21  to a frequency selected as a frequency of the transmission wave T to be transmitted from each of the transmission antennas  25 . The frequency selected as the frequency of the transmission wave T to be transmitted from each of the transmission antennas  25  may be set by the control unit  10 , for example. For example, the frequency selected as the frequency of the transmission wave T to be transmitted from each of the transmission antennas  25  may be a frequency selected by the parameter setting unit  16 . The frequency selected as the frequency of the transmission wave T to be transmitted from each of the transmission antennas  25  may be stored in the storage unit  40 , for example. The signal whose frequency has been increased by, the synthesizer  22  is supplied to the phase control unit  23  and the mixer  33 . When the plurality of phase control units  23  are present, the signal whose frequency has been increased by the synthesizer  22  may be supplied to each of the plurality of phase control units  23 . When the plurality of reception units  30  are present, the signal whose frequency has been increased by the synthesizer  22  may be supplied to each of the mixers  33  of the plurality of reception units  30 . 
     Each of the phase control units  23  controls a phase of the transmission signal supplied from the synthesizer  22 . Specifically, for example, in accordance with control performed by the control unit  10 , each of the phase control units  23  may appropriately advance or delay the phase of the signal supplied from the synthesizer  22  to adjust the phase of the transmission signal. In this case, on the basis of a difference between paths of the transmission waves T to be transmitted from the plurality of transmission antennas  25 , the phase control units  23  may adjust the phases of the respective transmission signals. The phase control units  23  appropriately adjust the phases of the respective transmission signals. Consequently, the transmission waves transmitted from the plurality of transmission antennas  25  enhance with each other in a predetermined direction to form a beam (beamforming). In this case, a correlation between a direction of beamforming and amounts of phase by which the respective transmission signals transmitted by the plurality of transmission antennas  25  are controlled may be stored in the storage unit  40 , for example. The transmission signal whose phase is controlled by each of the phase control units  23  is supplied to a respective one of the amplifiers  24 . 
     The amplifier  24  amplifies power (electric power) of the transmission signal supplied from the phase control unit  23  in accordance with control performed by the control unit  10 , for example. When the sensor  5  includes the plurality of transmission antennas  25 , each of the plurality of amplifiers  24  may amplify power (electric power) of the transmission signal supplied from a respective one of the plurality of phase control units  23  in accordance with control performed by the control unit  10 , for example. Since the technology for amplifying power of a transmission signal is already known, more detailed description is omitted. Each of the amplifiers  24  is connected to a respective one of the transmission antennas  25 . 
     The transmission antenna  25  outputs (transmits), as the transmission wave T, the transmission signal amplified by the amplifier  24 . When the sensor  5  includes the plurality of transmission antennas  25 , each of the plurality of transmission antennas  25  may output (transmit), as the transmission wave T, the transmission signal amplified by a respective one of the plurality of amplifiers  24 . Since the transmission antennas  25  can be configured in a manner that is the same as and/or similar to that of transmission antennas for use in the known radar technology, more detailed description is omitted. 
     The electronic device  1  according to the one embodiment, which includes the transmission antennas  25 , is capable of transmitting transmission signals (for example, transmission chirp signals) as the transmission waves T from the respective transmission antennas  25  in this manner. At least one of the functional units constituting the electronic device  1  may be housed in one housing. In this case, the one housing may have a hard-to-open structure. For example, the transmission antennas  25 , the reception antennas  31 , and the amplifiers  24  are desirably housed in one housing, and this housing desirably has a hard-to-open structure. When the sensor  5  is installed on the mobility device  100  such as an automobile, each of the transmission antennas  25  may transmit the transmission wave T to outside the mobility device  100  through a cover member such as a radar cover, for example. In this case, the radar cover may be made of a material, for example, a synthetic resin or rubber, that allows electromagnetic waves to pass therethrough. This radar cover may also serve as a housing of the sensor  5 , for example. The transmission antennas  25  are covered with a member such as the radar cover, so that a risk of the transmission antennas  25  being damaged or malfunctioning because of a contact with an external object can be reduced. The radar cover and the housing may also be referred to as a radome. 
       FIG. 2  illustrates an example in which the electronic device  1  includes two transmission antennas  25 . However, in the one embodiment, the electronic device  1  may include any number of transmission antennas  25 . On the other hand, in the one embodiment, the electronic device  1  may include the plurality of transmission antennas  25  in the case where the transmission waves T transmitted from the respective transmission antennas  25  form a beam in a predetermined direction. In the one embodiment, the electronic device  1  may include a plurality of transmission antennas  25 . In this case, the electronic device  1  may include the plurality of phase control units  23  and the plurality of amplifiers  24  to correspond to the plurality of transmission antennas  25 . Each of the plurality of phase control units  23  may control the phase of a respective one of the plurality of transmission waves supplied from the synthesizer  22  and to be transmitted from the plurality of transmission antennas  25 . Each of the plurality of amplifiers  24  may amplify power of a respective one of the plurality of transmission signals to be transmitted from the plurality of transmission antennas  25 . In this case, the sensor  5  may include the plurality of transmission antennas. AS described above, when the electronic device  1  illustrated  FIG. 2  includes the plurality of transmission antennas  25 , the electronic device  1  may include a plurality of functional units necessary for transmitting the transmission waves T from the plurality of transmission antennas  25 . 
     The reception antenna  31  receives the reflected wave R. The reflected wave R is the transmission wave T reflected off the predetermined object  200 . As the reception antenna  31 , a plurality of antennas such as the reception antennas  31 A to  31 D, for example, may be included. Since the reception antennas  31  can be configured in a manner that is the same as and/or similar to that of reception antennas for use in the known radar technology, more detailed description is omitted. Each of the reception antennas  31  is connected to the LNA  32 . A reception signal based on the reflected wave R received by each of the reception antennas  31  is supplied to the LNA  32 . 
     The electronic device  1  according to the one embodiment can receive, from each of the plurality of reception antennas  31 , the reflected wave R that is the transmission wave T that has been transmitted as the transmission signal (transmission chirp signal) such as a chirp signal, for example, and has been reflected off the predetermined object  200 . When the transmission chirp signal is transmitted as the transmission wave T in this manner, the reception signal based on the received reflected wave R is referred to as a reception chirp signal. That is, the electronic device  1  receives the reception signal (for example, the reception chirp signal) as the reflected wave R from each of the reception antennas  31 . When the sensor  5  is installed on the mobility device  100  such as an automobile, each of the reception antennas  31  may receive the reflected wave R from outside the mobility device  100  through a cover member such as a radar cover, for example. In this case, the radar cover may be made of a material, for example, a synthetic resin or rubber, that allows electromagnetic waves to pass therethrough. This radar cover may also serve as a housing of the sensor  5 , for example. The reception antennas  31  are covered with a member such as the radar cover, so that a risk of the reception antennas  31  being damaged or malfunctioning because of a contact with an external object can be reduced. The radar cover and the housing may also be referred to as a radome. 
     When the reception antennas  31  are installed near the transmission antennas  25 , these may be collectively included in one sensor  5 . That is, for example, one sensor  5  may include at least one transmission antenna  25  and at least one reception antenna  31 . For example, one sensor  5  may include the plurality of transmission antennas  25  and the plurality of reception antennas  31 . In such a case, one radar sensor may be covered with a cover member such as one radar cover, for example. 
     The LNA  32  amplifies, with low noise, the reception signal based on the reflected wave R received by a respective one of the reception antennas  31 . The LNA  32  may be a low-noise amplifier and amplifies, with low noise, the reception signal supplied from a respective one of the reception antennas  31 . The reception signal amplified by the LNA  32  is supplied to the mixer  33 . 
     The mixer  33  mixes (multiplies) the reception signal having a radio frequency (RF) supplied from the LNA  32  and the transmission signal supplied from the synthesizer  22  to generate a beat signal. The beat signal obtained by the mixer  33  through mixing is supplied to the IF unit  34 . 
     The IF unit  34  performs frequency conversion on the beat signal supplied from the mixer  33  to reduce the frequency of the beat signal to an intermediate frequency (IF). The beat signal whose frequency has been reduced by the IF unit  34  is supplied to the AD conversion unit  35 . 
     The AD conversion unit  35  digitizes the analog beat signal supplied from the IF unit  34 . The AD conversion unit  35  may be constituted by any analog-to-digital conversion circuit (Analog to Digital Converter (ADC)). The digitized beat signal obtained by the AD conversion unit  35  is supplied to the distance FFT processing unit  11  of the control unit  10 . In the case where there are the plurality of reception units  30 , the beat signals each digitized by a respective one of the plurality of AD conversion units  35  may be supplied to the distance FFT processing unit  11 . 
     The distance FFT processing unit  11  estimates a distance between the mobility device  100  equipped with the electronic device  1  and the object  200  on the basis of the beat signals supplied from the respective AD conversion units  35 . The distance FFT processing unit  11  may include a processing unit that performs fast Fourier transform, for example. In this case, the distance FFT processing unit  11  may be configured as any circuit, any chip, or the like that performs fast Fourier transform (FFT). 
     The distance FFT processing unit  11  performs FFT processing (hereinafter, appropriately referred to as “distance FFT processing”) on the beat signal that has been digitized by each of the AD conversion units  35 . For example, the distance FFT processing unit  11  may perform the FFT processing on a complex signal supplied from each of the AD conversion units  35 . The beat signal that has been digitized by each of the AD conversion units  35  can be represented as a temporal change in signal intensity (power). The distance FFT processing unit  11  performs FFT processing on such a beat signal, so that the beat signal can be represented as a signal intensity (power) for each frequency. If a peak in a result obtained by the distance FFT processing is equal to or greater than a predetermined threshold, the distance FFT processing unit.  11  may determine that the predetermined object  200  is located at the distance corresponding to the peak. For example, there is known a method for determining that an object (reflecting object) that reflects a transmission wave is present when a peak value that is equal to or greater than a threshold is detected from the average power or amplitude of a disturbance signal as in constant false alarm rate (CFAR)-based detection processing. 
     As described above, the electronic device  1  according to the one embodiment can detect, as the target, the object  200  that reflects the transmission wave T, based on the transmission signal transmitted as the transmission wave T and the reception signal received as the reflected wave R. 
     The distance FF 1  processing unit  11  can estimate a distance to the predetermined object on the basis of one chirp signal (for example, cl illustrated in  FIG. 3 ). That the electronic device  1  can measure (estimate) the distance L illustrated in  FIG. 1  by performing the distance FF 1  processing. Since a technique for measuring (estimating) a distance to a predetermined object by performing FFT processing on a beat signal is known, more detailed description is appropriately simplified or omitted. Results (for example, distance information) of the distance FFT processing performed by the distance FFT processing unit  11  may be supplied to the distance detection determining unit  12 . The results of the distance FFT processing performed by the distance FFT processing unit  11  may also be supplied to the velocity FFT processing unit  13  and/or the object detecting unit  16 , etc. 
     The distance detection determining unit  12  performs determination processing for a distance on the basis of the results of the distance FFT processing performed by the distance FFT processing unit  11 . For example, specifically, the distance detection determining unit  12  may determine that an object is present at the distance if a peak in the results of the distance FFT processing performed by the distance FFT processing unit  11  is greater than or equal to a predetermined threshold. As described above, the distance detection determining unit  12  determines whether the target is detected at a predetermined distance. The distance detection determining unit  12  is further described below. 
     The velocity FFT processing unit  13  estimates a relative velocity between the mobility device  100  equipped with the electronic device  1  and the object  200  on the basis of the beat signals on which the distance FFT processing has been performed by the distance FFT processing unit  11 . The velocity FFT processing unit  13  may include a processing unit that performs fast Fourier transform, for example. In this case, the velocity FFT processing unit  13  may be configured by any circuit, any chip, or the like that preforms fast Fourier transform (FFT) processing. 
     The velocity FFT processing unit  13  further performs FFT processing (hereinafter, appropriately referred to as “velocity FFT processing”) on each beat signal on which the distance FFT processing has been performed by the distance FFT processing unit  11 . For example, the velocity FFT processing unit  13  may perform the FFT processing on each complex signal supplied from the distance FFT processing unit  11 . The velocity FFT processing unit  13  can estimate a relative velocity to the predetermined object on the basis of a subframe (for example, the subframe  1  illustrated in  FIG. 3 ) including chirp signals. When the distance FFT processing is performed on the beat signal in the above-described manner, a plurality of vectors can be generated. The velocity FFT processing unit  13  can estimate a relative velocity to the predetermined object by determining a phase of a peak in a result of the velocity FFT processing performed on the plurality of vectors. That is, the electronic device  1  can measure (estimate) a relative velocity between the mobility device  100  and the predetermined object  200  illustrated in  FIG. 1  by performing the velocity FFT processing. Since a technique for measuring (estimating) a relative velocity to a predetermined object by performing velocity FFT processing on a result of distance FFT processing is known, more detailed description is appropriately simplified or omitted. Results (for example, velocity information) of the velocity FFT processing performed by the velocity FFT processing unit  13  may be supplied to the velocity detection determining unit  14 . The results of the velocity FFT processing performed by the velocity FFT processing unit  13  may also be supplied to the angle-of-arrival estimating unit  15  and/or the object detecting unit  16 , etc. 
     The velocity detection determining unit  14  performs determination processing for a velocity on the basis of the results of the velocity FFT processing performed by the velocity FFT processing unit  13 . For example, specifically, the velocity detection determining unit  14  may determine that an object is present at the velocity if a peak in the results of the velocity FFT processing performed by the velocity FFT processing unit  13  is greater than or equal to a predetermined threshold. As described above, the velocity detection determining unit  14  determines whether the target is detected at a predetermined velocity. The velocity detection determining unit  12  is further described below. 
     The angle-of-arrival estimating unit  15  estimates a direction from which the reflected wave R arrives from the predetermined object  200  on the basis of the result of the velocity FFT processing performed by the velocity FFT processing unit  13 . The electronic device  1  can estimate the direction from which the reflected wave R arrives by receiving the reflected wave R from the plurality of reception antennas  31 . For example, the plurality of reception antennas  31  are arranged at a predetermined interval. In this case, the transmission wave T transmitted from each of the transmission antennas  25  is reflected off the predetermined object  200  to become the reflected wave R. Each of the plurality of reception antennas  31  arranged at the predetermined interval receives the reflected wave R. The angle-of-arrival estimating unit  15  can estimate the direction from which the reflected wave R arrives at each of the plurality of reception antennas  31  on the basis of the phase of the reflected wave R received by the reception antenna  31  and a difference in path of the reflected wave R. That is, the electronic device  1  can measure (estimate) the angle of arrival θ illustrated in  FIG. 1  on the basis of the results of the velocity FFT processing. 
     Various techniques for estimating a direction from which the reflected wave R arrives on the basis of a result of velocity FFT processing have been proposed. For example, MUSIC (Multiple Signal Classification), ESPRIT (Estimation of Signal. Parameters via Rotational Invariance Technique), and the like are known as known arriving direction estimation algorithms. Thus, more detailed description of the known techniques is appropriately simplified or omitted. Information (angle information) on the angle of arrival θ estimated by the angle-of-arrival estimating unit  15  may be supplied to the object detecting unit.  16 . 
     The object detecting unit  16  detects an object located in a range in which the transmission wave T is transmitted, on the basis of the information supplied from at least any of the distance FFT processing unit  11 , the velocity FFT processing unit  13 , and the angle-of-arrival estimating unit  15 . The object detecting unit  16  may perform detection of an object by performing, for example, clustering processing on. the basis of the supplied distance information, velocity information, and angle information. For example, DBSCAN (Density-based spatial clustering of applications with noise) or the like is known as an algorithm used in clustering of data. In the clustering processing, for example, average power of points constituting the detected object may be calculated. The distance information, the velocity information, the angle information, and power information of the object detected by the object detecting unit  16  may be supplied to a detection range determining unit  15 . The distance information, the velocity information, the angle information, and the power information of the object detected by the object detecting unit  16  may be supplied to the ECU  50 . In this case, when the mobility device  100  is an automobile, communication may be performed using a communication interface such as a CAN (Controller Area Network), for example. 
     The ECU  50  included in the electronic device  1  according to the one embodiment is capable of controlling the functional units of the mobility device  100  and also controlling operations of the entire mobility device  100 . To provide control and processing capabilities for executing various functions, the ECU  50  may include at least one processor, for example, a CPU (Central Processing Unit). The ECU  50  may be collectively implemented by one processor, may be implemented by some processors, or may be implemented discrete individual processors. The processor may be implemented as one integrated circuit. The integrated circuit is also referred to as an IC. The processor may be implemented as a plurality of integrated circuits and discrete circuits connected to be able to perform communication. The processor may be implemented on the basis of various other known technologies. In the one embodiment, the ECU  50  may be configured as, for example, a CPU and a program executed by the CPU. The ECU  50  may appropriately include a memory required for operations of the ECU  50 . At least part of the functions of the control unit  10  may be functions of the ECU  50 , or at least part of the functions of the ECU  50  may be functions of the control unit  10 . 
     The electronic device  1  illustrated in  FIG. 2  includes the two transmission antennas  25  and the four reception antennas  31 . However, the electronic device  1  according to the one embodiment may include any number of transmission antennas  25  and any number of reception antennas  31 . For example, by including the two transmission antennas  25  and the four reception antennas  31 , the electronic device  1  can be regarded to include a virtual antenna array that is virtually constituted by eight antennas. As described above, the electronic device  1  may receive the reflected wave R of  16  subframes illustrated in  FIG. 3  by using, for example, the eight virtual antennas. 
     Target detection processing performed by the electronic device  1  according to the one embodiment is described next. 
     As described above, the electronic device  1  according to the one embodiment transmits transmission waves from the transmission antennas and receives, from the reception antennas, reflected waves that are the transmission waves fleeted off an object serving as a target and/or clutter. 
     The electronic device  1  according to the one embodiment may detect, as the target, the object that reflects the transmission waves, on the basis of the transmission signal and/or the reception signal. 
     In a common FM-CW radar technology, whether a target is present can be determined on the basis of a result of fast Fourier transform processing or the like performed on a beat frequency extracted from a reception signal. The result of the fast Fourier transform processing or the like performed on the beat frequency extracted from the reception signal includes a noise component due to clutter (extraneous reflection component) or the like. Thus, processing for removing the noise component from the processing result of the reception signal and extracting a target signal alone may be performed. 
     As a technique for determining whether the target is present, there is a scheme (threshold detection scheme) for setting a threshold for output of the reception signal and assumes that the target is present if the intensity of a fleeted signal exceeds the threshold. When this scheme is employed, the target is determined also when the signal intensity or clutter exceeds the threshold. Consequently, a so-called “false alarm” is issued. Whether the signal intensity of this clutter exceeds the threshold is a matter of a probability. The probability of the signal intensity of this clutter exceeding the threshold is called “a probability of false alarm”. As a technique for suppressing this probability of false alarm to be low and constant, the constant false alarm rate can be used. 
     Hereinafter, the constant false alarm rate is also simply referred to as CFAR. CFAR employs an assumption that the signal intensity (amplitude) of noise conforms to a Rayleigh distribution. Based on this assumption, if a weight for use in calculation of a threshold for use in determining whether a target is detected is fixed, an error rate in detection of the target becomes theoretically constant regardless of the amplitude of noise. 
     As CFAR in the common radar technology, a scheme called Cell-Averaging CFAR (hereinafter, also referred to as CA-CFAR) is known. In CA-CFAR, a signal intensity value (for example, an amplitude value) of the reception signal having undergone predetermined processing may be sequentially input to a shift register at a constant sampling frequency. This shift register has a cell under test at the center and has a plurality of reference cells on both sides of the cell under test. Every time the signal intensity value is input to the shift register, each signal intensity value input previously is moved from a cell on one end side (for example, a left end side) to a cell on the other end side (for example, a right end side) of the shift register by one. In synchronization with the input timing, the values in the reference cells are averaged. The average value thus obtained is multiplied by a prescribed weight, and the result is calculated as a threshold. If the value in the cell under test is greater than the threshold thus calculated, the value in the cell under test is output. On the other hand, if the value in the cell under test is not greater than the calculated threshold, a value of  0  is output. As described above, in CA-CFAR, the threshold is calculated from the average of the values in the reference cells and whether a target is present is determined. In this manner, a detection result can be obtained. 
     In CA-CFAR, for example, when a plurality of targets are present in the vicinity to each other, the threshold calculated in the vicinity of the targets increases because of the nature of the algorithm. Thus, a target may not be detected regardless of the sufficient signal intensity. Likewise, when there is a clutter step, the calculated threshold increases also in the vicinity of the clutter step. Also in this case, a small target located in the vicinity of the clutter step may not be detected. 
     In relation to CA-CFAR described above, there is a technique called Order Statistic CFAR (hereinafter, also referred to as OS-CFAR) as a technique for obtaining a threshold from the median of the values in the reference cells or from a value at a prescribed place in order of the values in the reference cells sorted in ascending order. CFER is a technique for setting a threshold on the basis of ordered statistics and determining that a target is present if the signal intensity exceeds the threshold. This OS-CFAR can cope with the above-described issues in CA-CFAR. OS-CFAR can be implemented by performing processing that is partially different from that of CA-CFAR. 
     An example in which the electronic device  1  according to the one embodiment performs OS-CFAR processing is further described below. 
     In the electronic device  1  according to the one embodiment, for example, the distance detection determining unit  12  and/or the velocity detection determining unit  14  of the control unit  10  illustrated in  FIG. 2  -, may perform the 
     OS-CFAR processing. An example in which the distance detection determining unit  12  performs the OS-CFAR processing is described below with reference to  FIG. 4 . The velocity detection determining unit  14  may perform the OS-CFAR processing in the same and/or similar manner. 
     As described in  FIG. 2 , in the electronic device  1  according to the one embodiment, the frequency of the chirp signal generated by the signal generating unit  21  is increased by the synthesizer  22  to the frequency in the selected frequency band. The frequency-increased chirp signal is transmitted from the transmission antennas  25  through the phase control units  23  and the amplifiers  24 . The chirp signal reflected off a reflecting object passes through the reception antenna  31  and the DNA  32  and  1  multiplied by the transmission signal in the mixer  33 , and is received by the AD conversion unit  35  through the IF unit  34 . The distance FFT processing unit  11  performs the distance FFT processing on the complex signal received by the AD conversion unit  35 . 
     In the one embodiment, the distance detection determining unit  12  may perform the OS-CFAR processing on the signal on which the distance FFT processing has been performed by the distance FFT processing unit  11 .  FIG. 4  is a block diagram for describing processing performed by the control unit  10  of the electronic device  1  according to the one embodiment. More specifically,  FIG. 4  is a diagram for describing an example of a logic of circuitry that performs the OS-CFAR processing in the distance detection determining unit  12  of the control unit  10 . To perform the OS-CFAR processing, the distance detection determining unit  12  may include a shift register  121 , a sorting unit  122 , a data selecting unit  123 , a threshold calculating unit  124 , a weight setting unit  125 , and a detection determining unit  126  as illustrated in  FIG. 4 . 
     In OS-CFAR, as in the case of CA-CFAR, the signal intensity value of the reception signal having undergone predetermined processing may be sequentially input to the shift register  121  at a constant sampling frequency. Every time the signal intensity value is input to the shift register  121 , each signal intensity value input previously is moved from a cell on one end side (for example, a left end side) to a cell on the other end side (for example, a right end side) of the shift register  121  by one. As described above, in the one embodiment, the shift register  121  (of the distance detection determining unit  12 ) may shift the signal intensity based on the reception signal input from one end at a predetermined sampling frequency toward the other end in a first-in first-out mariner. 
     As illustrated in  FIG. 4 , the shift register  121  may have a cell under test T in a test region at the center. Hereinafter, a region in which the cell under test T is arranged may also be referred to as a “test region”. The shift register  121  may also have guard cells G in guard regions on both sides of the cell under test T.  FIG. 4  illustrates the guard cells G as two contiguous cells. 
     However, the number of guard cells G may be any number. Hereinafter, a region in which the guard cell G is arranged may also be referred to as a “guard region”. The shift register  121  further has a plurality of reference cells R in reference regions on the respective outer sides of the guard cells G.  FIG. 4  illustrates the reference cells R as four contiguous cells. However, the number of reference cells R may be any number. Hereinafter, a region in which the reference cell R is arranged may also be referred to as a “reference region”. As described above, in the one embodiment, the control unit  10  (the shift register  121  of the distance detection determining unit.  12 ) may establish the guard region between the test region and the reference region. As described above, in the one embodiment, the shift register  121  may include the cell under test T in the test region and the reference cell R in the reference region. 
     The sorting unit  122  sorts values output from the respective reference cells R in ascending order. The sorting unit  122  may be constituted by, for example, any sorting circuit or the like. The sorting unit  122  may sort the values in the reference cells R in ascending order, synchronization with a timing at which the signal intensity is input to the shift register  121 . As described above, in the one embodiment, the control unit  10  (the distance detection determining unit  12 ) may include the sorting unit  122  that sorts, in ascending order, signal intensities output from the reference cells R of the shift register  121 . 
     The data selecting unit  123  may select and extract a value at a prescribed position (for example, at a predetermined place in order from the smallest) from among the values sorted by the sorting unit  122 . As described above, in the one embodiment, the control unit  10  (the distance detection determining unit  12 ) may include the data selecting unit  123  that selects a signal intensity at a predetermined place in order from among the signal intensities sorted by the sorting unit  122 . 
     The threshold calculating unit.  124  may calculate a threshold Th by multiplying the value selected by the data selecting unit  123  by a prescribed weight. In this case, the weight setting unit  125  may calculate the threshold Th by multiplying the value selected by the data selecting unit  123  by, for example, a prescribed weight M. As described above, in the one embodiment, the control unit  10  (the distance detection determining unit  12 ) may include the threshold calculating unit  124  that sets a threshold for use in detection of the target, based on the signal intensity selected by the data selecting unit  123 . 
     The detection determining unit  126  compares a magnitude of a signal intensity value A in the cell under test T with the threshold Th calculated by the threshold calculating unit  124 . If the signal intensity value A in the cell under test T is greater than the threshold Th, the detection determining unit  126  outputs, as a detection result, the signal intensity value A in the cell under test T. On the other hand, if the signal intensity value A in the cell under test T is not greater than the threshold Th, the detection determining unit  126  outputs zero as the detection result. As described above, in the one embodiment, the control unit  10  (the detection determining unit  126  of the distance detection determining unit  12 ) may determine whether a target is present, based on the signal intensity A in the cell under test T in the test region and the threshold Th. 
     In OS-CFAR, the threshold is calculated from the value at a prescribed position (for example, at a predetermined place in order from the smallest) among the sorted signal intensities. Thus, an influence of a signal based on a reflected wave on calculation of the threshold may be suppressed. Therefore, with OS-CFAR, an increase in the threshold may be suppressed in the vicinity of the targets. 
     In addition, with OS-CFAR, an increase in the threshold may be suppressed in the vicinity of the clutter step. 
     In the electronic device  1  according to the one embodiment, the distance FFT processing unit  11  performs distance FFT processing on the beat signal digitized by the AD conversion unit  35 . Consequently, a distribution of the signal intensities (powers) in the distance direction is obtained. In this case, as illustrated in  FIG. 5 , the right side in the shift register  121  may correspond to a distance far from the sensor  5  of the electronic device  1 . In addition, the left side in the shift register  121  may correspond to a distance near the sensor  5  of the electronic device  1 .  FIG. 5  is a diagram for describing an example in which the electronic device  1  according to the one embodiment performs the OS-CFER processing. In  FIG. 5 , the cell under test T, the guard cells C, and the reference cells R are arranged in the same manner as in the example illustrated in  FIG. 4 . 
     By using OS-CFAR described above, the electronic device according to the one embodiment can determine detection of a distance. That is, the control unit.  10  of the electronic device  1  according to the one embodiment calculates a distance threshold Th on the basis of a value at predetermined place in order (for example, K-th) from the lowest among signal intensities (powers) in the reference cells R. The control unit  10  of the electronic device  1  according to the one embodiment can determine that the target is present in the test region if the signal intensity value A in the cell under test. T is greater than the distance threshold Th. 
     At the distance at which the target is determined to be present in this manner, the velocity FFT processing unit  13  of the control unit  10  may perform velocity FF 1  processing on the plurality of chirp signals. Similarly to the distance detection determining unit  12  described above, the velocity detect ion determining unit  14  may determine detection of a velocity. In this case, as illustrated in  FIG. 6 , the lower side in the shift register  121  may correspond to a region where the relative velocity between the sensor  5  of the electronic device  1  and the target is fast. In addition, as illustrated in  FIG. 6 , the upper side in the shift register  121  may correspond to a region where the relative velocity between the sensor  5  of the electronic device  1  and the target is slow.  FIG. 6  is a diagram for describing the example in which the electronic device  1  according to the one embodiment performs the OS-CFER processing. The cell under test  1 , the guard cells G, and the reference cells R are arranged also in  FIG. 6 . The arrangement illustrated in  FIG. 6  is an example. As described above, the electronic device  1  according to the one embodiment can determine detection of a velocity by using the constant false alarm rate in the velocity direction. 
     In the shift register  121  illustrated in  FIG. 5 , the plurality of reference cells R are arranged contiguously in the distance direction. In OS-CFAR, if the reference cells R. are arranged in the shift register  121  as illustrated in  FIG. 5 , it is anticipated that the target is not correctly detected depending on the circumstances. 
     For example, suppose that, in a circumstance in which a vehicle of interest equipped with an on-vehicle radar is about to change the lane from a cruising lane to a fast lane, another vehicle or the like located behind the vehicle of interest is to be detected by using the on-vehicle radar. Suppose that a relatively long vehicle such as a truck is traveling behind the vehicle of interest. In this case, the signal intensity based on a reflected wave from the large (long) interfering object (truck) is continuously detected in the distance direction in the reference regions (reference cells R) of the shift register  121 . Thus, the on-vehicle radar is expectedly able to detect the truck as the target. However, suppose that, for example, another small vehicle or the like is traveling adjacently to the truck in a lane adjacent to the lane in which the track is traveling. 
     In such a case, even if an attempt to detect, as the target, the small vehicle or the like traveling adjacently to the truck is made, the reference regions in which the reference cells R are arranged become regions corresponding to the signal intensities based on the reflected wave from the truck. In such a circumstance, the signal intensity value A in the cell under test T in the test region no longer exceeds the threshold Th because of increased noise power. Thus, the on-vehicle radar expectedly fails to detect the small vehicle as the target. 
     In addition, the signal intensity (power) based on the reflected wave tends to increase as the distance from the radar decreases. Thus, if the near side with respect to the target is referred to, the signal intensity value A in the cell under test T in the test region no longer exceeds the threshold Th because of increased noise power. Also in such a case, the on-vehicle radar expectedly fails to detect the object as the target. 
     To cope with such a circumstance, the electronic device  1  according to the one embodiment changes the arrangement of the reference regions (reference cells R) in the shift register  121 . The following description is given on the assumption that the electronic device  1  according to the one embodiment detects the target by using the constant false alarm rate. 
       FIG. 7  is a diagram illustrating an example of the arrangement of the reference regions (reference cells R) in. the shift register  121  of the electronic device  1  according to the one embodiment. The cell under test T, the guard cells G, and the reference cells R are arranged also in  FIG. 7 . The arrangement illustrated in  FIG. 7  is an example. As in.  FIG. 5 , in  FIG. 7 , the right side in the shift register  121  corresponds to the distance far from the sensor  5  of the electronic device  1  and the left side in the shift register  121  corresponds to the distance near the sensor  5  of the electronic device  1 . 
     As illustrated in  FIG. 7 , in the shift register  121  of the electronic device  1  according to the one embodiment, the reference regions (reference cells R) are arranged on the far side with respect to the test region (cell under test T) in term of the distance. That is, in the shift register  121  of the electronic device  1  according to the one embodiment, the reference regions need not be arranged on the near side with respect to the test region in terms of the distance. In the shift register  121  illustrated in  FIG. 7 , no reference regions are arranged in regions corresponding to the near distance, and the reference regions are arranged in regions corresponding to the far distance. The electronic device according to the present disclosure may arrange the reference regions on the near side with respect to the test region in terms of the distance. 
     As illustrated in  7 , in the shift register  121  of the electronic device  1  according to the one embodiment, the reference regions (reference cells R) may be arranged non-contiguously. That is, in the shift register  121  of the electronic device  1  according to the one embodiment, the reference cells R may be arranged in a non-contiguous manner. In the shift register  121  illustrated in  FIG. 7 , the reference cells R are arranged non-contiguously without succession. In the example illustrated in  FIG. 7 , seven reference cells R are arranged non-contiguously. However, the number of arranged reference cells R may be any number depending on the manner of detecting the target or the required accuracy, for example. In the example illustrated in  FIG. 7 , the reference cells R are arranged on every other line. However, the intervals at which the reference cells R are arranged non-contiguously may be any intervals depending on the manner of detecting the target or the required accuracy, for example. The intervals at which the reference cells R are arranged may be any intervals, and the intervals at which the reference cells R arranged may be equal intervals or intervals different for the respective reference cells. 
     As illustrated in  FIG. 7 , as in the case of  FIG. 5 , the shift register  121  may have the guard cells G in the respective guard regions on both sides of the cell under test T. As described above, a guard region (guard cell G) may be established between the test region (cell under test T) and the reference region (reference cell R) in. (the shift register  121  of the distance detection determining unit  12 ) the control unit  10 . In the one embodiment, a guard region (guard cell G) may be established on a near side in the distance direction with respect to the test region (cell under test T) to be adjacent to the test region (cell under test T) in (the shift register  121  of the distance detection determining unit  12 ) the control unit  10 . 
     After the electronic device  1  according to the one embodiment arranges the reference regions in the above-described manner, the electronic device  1  according to the one embodiment can determine detection of a distance by using OS-CFAR described above. That is, the control unit  10  of the electronic device  1  according to the one embodiment calculates a distance threshold Th on the basis of a value at a predetermined place in order (for example, K-th) from the lowest among signal intensities (powers) in the reference cells R. The control unit  10  of the electronic device  1  according to the one embodiment can determine that the target is present in the test region if the signal intensity value A in the cell under test T is greater than the distance threshold Th. 
     As described above, at the distance at which the target is determined to be present in this manner, the velocity FFT processing unit  13  of the control unit  10  may perform velocity FFT processing on the plurality of chirp signals. Similarly to the distance detection determining  12  described above, the velocity detection determining  13  may also determine detection of a velocity. In this manner, the electronic device  1  according to the one embodiment can determine detection of a velocity by using the constant false alarm rate in the velocity direction. 
     Further, in the electronic device  1  according to the one embodiment, the angle-of-arrival estimating unit  15  may estimate a direction from which the reflected wave arrives on the basis of complex signals received by the plurality of reception antennas  31 , at the velocity at which the target is determined to be present. As described above, the electronic device  1  according to the one embodiment can estimate an angle for the direction in which the target is present. 
     In the electronic device  1  according to the one embodiment, the object detecting unit  16  determines whether an object is detected (for example, by clustering) as the target on the basis of the information on the direction (angle) in which the reflected wave arrives, the information on the relative velocity to the target, and/or the information on the distance to the target. The information on the direction (angle) in which the reflected wave arrives may be acquired from the angle-of-arrival estimating unit  15 . The information on the relative velocity to the target may be acquired from the velocity FFT processing unit  13  or the velocity detection determining unit  14 . The information on the distance to the target may be acquired from the distance FFT processing unit  11  or the distance detection determining unit  12 . In this case, the object detecting unit  16  may calculate average power at points constituting the object detected as the target. 
     As described above, in the electronic device  1  according to the one embodiment, the control unit  10  detects the target by using the constant false alarm rate, based on the transmission signal transmitted as the transmission wave and the reception signal received as the reflected wave. In this case, the control unit  10  establishes reference regions (reference cells R) on the far side in the distance direction with respect to the test region in the distribution of signal intensities based on the reception signal in the distance direction. The control unit  10  also sets the threshold Th for use in detection of the target, based on an order statistic among the signal intensities in the reference regions (reference cells R). The control unit  10  may also arrange the plurality of reference cells R non-contiguously in the reference regions and set the threshold Th for use in detection of the target, based on an order statistic among the signal intensities in the plurality of reference cells R. 
     As described above, the electronic device  1  according to the one embodiment arranges the reference regions (reference cells R) of noise to be far from the test region (T) of the target object in the distance direction. In the one embodiment, the reference regions (reference cells R) are arranged non-contiguously. Consequently, even if the electronic device  1  according to the one embodiment receives a reflected wave from a relatively large (long) interfering object, for example, the electronic device  1  can detect noise power so that the interfering object is removed. Thus, the electronic device  1  according to the one embodiment can. improve the target detection accuracy. 
     For example, even when a relatively long vehicle such as a truck is traveling behind the vehicle of interest as in the above-described assumed example, a distance corresponding to the reference cells R arranged non-contiguously is farther than that for the truck in the electronic device  1  according to the one embodiment. Thus, the electronic device  1  according to the one embodiment detects power of noise of part other than the truck. Consequently, the vehicle in the test region exceeds the threshold. Therefore, the electronic device  1  according to the one embodiment can improve the target detection accuracy. 
     While the present disclosure has been described on the basis of the various drawings and the embodiments, it should be noted that a person skilled in the art can easily make various variations or corrections on the basis of the present disclosure. Therefore, it should be noted that these variations or corrections are within the scope of the present disclosure. For example, functions and the like included in each functional unit can be rearranged without any logical contradiction. A plurality of functional units or the like may be combined into one or may be divided. The embodiments according to the present disclosure described above are not limited to strict implementation according to the respective embodiments described above, and may be implemented by appropriately combining the features or omitting part thereof. That is, a person skilled in the art can make various variations and corrections to the contents of the present disclosure on the basis of the present disclosure. Accordingly, these variations and corrections are within the scope of the present disclosure. For example, in each embodiment, each functional unit, each means, each step, or the like can be added to another embodiment or replaced with each functional unit, each means, each step, or the like in another embodiment without any logical contradiction. In each embodiment, a plurality of functional units, means, steps, or the like may be combined to one or may be divided. The embodiments according to the present disclosure described above are not limited to strict implementation according to the respective embodiments described above, and may be implemented by appropriately combining the features or omitting part thereof. 
     For example, in the embodiments described above, the description has been given of the configuration in which the object detection ranges are dynamically switched between by using the one sensor  5 . However, in one embodiment, detection of an object may be performed in the determined object detection ranges by using the plurality of sensors  5  In one embodiment, beamforming may be performed toward the determined object detection ranges by using the plurality of sensors  5 . 
     The embodiments described above are not limited to implementation as the electronic device  1 . For example, the embodiments described above may be implemented as a method for controlling a device such as the electronic device  1 . For example, the embodiments described above may be implemented as a program executed by a device such as the electronic device  1 . 
     The electronic device  1  according to one embodiment may include, as the minimum configuration, at least part of at least one of the sensor  5  or the control unit  10 , for example. On the other hand, the electronic device  1  according to one embodiment may appropriately include at least any of the signal generating unit  21 , the synthesizer  22 , the phase control units  23 , the amplifiers  24 , and the transmission antennas  25  as illustrated in  FIG. 2  in addition to the control unit  10 . The electronic device  1  according to the one embodiment may appropriately include at least any of the reception antennas  31 , the LNAs  32 , the mixers  33 , the IF units  34 , and the AD conversion units  35  instead of or along with the functional units described above. The electronic device  1  according to the one embodiment may include the storage unit  40 . As described above, the electronic device  1  according to the one embodiment can employ various configurations. When the electronic device  1  according to the one embodiment is mounted in the mobility device  100 , for example, at least any of the functional units described above may be installed at an appropriate place such as the inside of the mobility device  100 . On the other hand, in one embodiment, for example, at least any of the transmission antennas  25  and the reception antennas  31  may be installed outside the mobility device  100 . 
     REFERENCE SIGNS LIST 
       1  electronic device 
       5  sensor 
       10  control unit 
       11  distance FFT processing unit 
       12  distance detection determining unit 
       13  velocity FFT processing unit 
       14  velocity detection determining unit. 
       15  angle-of-arrival estimating unit 
       16  object detecting unit 
       20  transmission unit 
       21  signal generating unit 
       22  synthesizer 
       23  phase control unit 
       24  amplifier 
       25  transmission antenna 
       30  reception unit 
       31  reception antenna 
       32  LNA 
       33  mixer 
       34  IF unit 
       35  AD conversion unit 
       40  storage unit 
       50  ECU 
       100  mobility device 
       121  shift register 
       122  sorting unit 
       123  data selecting unit 
       124  threshold calculating unit 
       125  weight setting unit 
       126  detection determining unit 
       200  object