Patent Publication Number: US-9892581-B2

Title: Vehicle door control system and operating method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 2016-0029027, filed on Mar. 10, 2016, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a vehicle door control technique, and more particularly, to a vehicle door control system configured to control a vehicle door using a portable terminal and an operating method thereof. 
     2. Discussion of Related Art 
     Recently, a vehicle smart key system is tending to be widely used, and a smart key is typically called “FOB key.” 
     A smart key system refers to a system installed in a vehicle to detect an action taken while a user is carrying the smart key and then control an operation of the vehicle. 
     A smart key system includes a smart key and a smart key electronic control unit (hereinafter referred to as SMK ECU) of a vehicle. Here, the smart phone and the SMK ECU communicate through respective built-in communication modules. 
     According to a conventional smart key system, when a user intends to control locking and unlocking of a vehicle door, the user should approach the vehicle while carrying a smartphone and control a passive switch located at a door handle. 
     In more detail, for a conventional door control system using a smart key, when a driver carrying a smart key pushes a passive switch placed at a door, an LF signal is transmitted to the smart key through an LF antenna placed at a door handle. When the smart key receives the LF signal and then transmits a response signal to an SMK ECU via radio frequency (RF), the SMK ECU controls a vehicle door to be locked or unlocked. 
     As described above, in the field of the vehicle door control, the smart key system provides the vehicle door control. 
     Accordingly, since the smart key system provides a vehicle door control function through authentication of a smart key carried by a driver, there is an inconvenience that the driver must carry a smart key to utilize the conventional smart key system. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing a vehicle door control system configured to control a vehicle door using a portable terminal and an operating method thereof. 
     According to an aspect of the present invention, there is provided an vehicle door control system including a communication unit configured to wirelessly communicate with a smart key or a portable terminal located around a vehicle; a controller configured to communicate with the smart key or the portable terminal using the communication unit, perform authentication on the smart key or the portable terminal based on a received signal, and output a door control signal for controlling a vehicle door when the authentication is successful; and a motor driver configured to lock or unlock the vehicle door according to the door control signal. 
     The communication unit may include a first communication unit configured to perform low frequency (LF) communication with the smart key; a second communication unit configured to perform radio frequency (RF) communication with the smart key; and a third communication unit configured to perform near field communication (NFC) communication with the portable terminal. 
     The controller may control the first communication unit to transmit an LF discovery signal for discovering the smart key at every first interval and may control the third communication unit to transmit an NFC discovery signal for discovering the portable terminal at every second interval. 
     The controller may control the third communication unit to transmit the NFC discovery signal a predetermined number of times and may control the first communication unit to transmit the LF discovery signal when the portable terminal is discovered during transmission of the NFC discovery signal. 
     The first interval and the second interval may be set different from each other, and the second interval may be set shorter than the first interval. 
     The controller may determine whether an ID included in a response signal transmitted from the portable terminal discovered by the NFC discovery signal matches a preset ID and may output the door control signal when the two IDs match. 
     A first antenna connected to the first communication unit and a third antenna connected to the third communication unit may be produced in one body to form an antenna module. 
     The antenna module may be installed at a door handle of the vehicle. 
     The antenna module may be formed to have a first antenna coil wound on a ferrite core in one direction and a third antenna coil wound on the ferrite core in another direction. 
     The antenna module may be formed to have the third antenna coil wound on the ferrite core on which the first antenna coil has already been wound. 
     The antenna module may be formed to have the first antenna coil wound on the ferrite core on which the third antenna coil has already been wound. 
     According to another aspect of the present invention, there is provided a method of operating a vehicle door control system, the method including transmitting an NFC discovery signal for discovering a portable terminal at every first interval; counting the number of transmissions of the NFC discovery signal when the NFC discovery signal is transmitted; determining whether the portable terminal has been discovered; and controlling a vehicle door when it is determined that the portable terminal has been discovered, based on a result of authentication of the discovered portable terminal. 
     The determining of whether the portable terminal has been discovered may be performed based on whether a response signal transmitted by the portable terminal that has received the NFC discovery signal is received. 
     The controlling of a vehicle door may include performing authentication on the discovered portable terminal; determining whether the authentication is successful from the authentication result; and controlling the vehicle door when it is determined that the authentication is successful. 
     The performing of authentication on the discovered portable terminal may include comparing an ID included in the response signal transmitted from the portable terminal that has received the NFC discovery signal with a preset ID. 
     The method may further include determining whether a count value is equal to or greater than a predetermined value with respect to the number of transmissions of the NFC discovery signal when it is determined that the portable terminal has not been discovered; and transmitting the NFC discovery signal at every first interval when it is determined that the count value is less than the predetermined value. 
     The method may further include transmitting an LF discovery signal for discovering a smart key at every second interval when it is determined that the count value is equal to or greater than the predetermined value; initializing the count value with respect to the number of transmissions of the NFC discovery signal; determining whether the smart key has been discovered; and controlling the vehicle door when it is determined that the smart key has been discovered, based on a result of authentication of the discovered smart key. 
     The method may further include transmitting the NFC discovery signal at every first interval when it is determined that the smart key has not been discovered. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram showing a configuration of a vehicle door control system according to an embodiment of the present invention; 
         FIG. 2  is a diagram showing an example of an antenna module of a vehicle door control system according to an embodiment of the present invention; 
         FIG. 3  is a diagram showing transmission intervals of an NFC discovery signal and an LF discovery signal that are transmitted from a vehicle door control system according to an embodiment of the present invention; 
         FIG. 4  is a diagram for describing a process in which a vehicle door control system according to an embodiment of the present invention controls a vehicle door using LF communication and RF communication; 
         FIG. 5  is a diagram for describing a process in which a vehicle door control system according to an embodiment of the present invention controls a vehicle door using NFC communication; and 
         FIGS. 6 and 7  are flowcharts showing sequences of a vehicle door control operation of a vehicle door control system according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     In the following description, when the detailed description of the relevant known functions or configurations is determined to unnecessarily obscure the important point of the present invention, the detailed description will be omitted. Also, terms used herein are defined in consideration of the functions of the present disclosure and may be changed depending on a user, the intent of an operator, or a custom. Accordingly, the terms must be defined based on the following overall description of this specification. 
     Hereinafter, a vehicle door control system and an operating method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a block diagram showing a configuration of a vehicle door control system according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a vehicle door control system  1  according to an embodiment of the present invention is configured to control locking and unlocking of a vehicle door through authentication of a smart key  2  or a portable terminal  3  placed around a vehicle. 
     To this end, the vehicle door control system  1  may include at least one or more processor for performing functions and a memory for storing information needed to perform the functions or a result of the performance. 
     In particular, the vehicle door control system  1  performs low-frequency (LF) communication and radio-frequency (RF) communication with the smart key and performs near-field communication (NFC) communication with the portable terminal  3 . 
     To this end, the smart key  2  includes an LF communication unit and an RF communication unit and stores its own identity (ID), and the portable terminal  3  includes an NFC communication unit and stores its own ID. 
     In this case, the portable terminal  3  may be, for example, a smartphone, but may also include a notebook computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), an e-book terminal, etc. 
     Also, the vehicle door control system  1  includes an LF communication unit and an RF communication unit for communicating with the smart key  2  and an NFC communication unit for communicating with the portable terminal  3  and stores the ID of the smart key  2  and the ID of the portable terminal  3 . 
     The vehicle door control system  1  according to an embodiment of the present invention will be described below in detail. The vehicle door control system  1  may include a first communication unit  11 , a second communication unit  12 , a third communication unit  13 , a switch  14 , a controller  15 , and a motor driver  16 . The configuration shown in  FIG. 1  is an example of the vehicle door control system  1  according to an embodiment of the present invention. Thus, the configuration of the vehicle door control system  1  is not limited to that shown in  FIG. 1  and may further include elements other than the aforementioned elements. 
     In this case, signal transmission or reception between the elements of the vehicle door control system  1  may be performed based on Control Area Network (CAN) communication. 
     The first, second, and third communication units  11 ,  12 , and  13  communicate with the smart key  2  or the portable terminal  3  using at least one of wireless communication technologies such as a radio frequency (RF), low frequency (LF), and near field communication (NFC) in order to check the presence (search and authentication) of the smart key  2  or the portable terminal  3 . 
     The first, second, and third communication units  11 ,  12 , and  13  transmit signals to the smart key  2  or the portable terminal  3  according to functions of the communication units or receive a signal transmitted from the smart key  2  or the portable terminal  3  and then deliver the received signal to the controller  15 . 
     To this end, the first, second, and third communication units  11 ,  12 , and  13  are connected with first, second, and third antennas  17 ,  18 , and  19 , respectively. The first, second, third communication units  11 ,  12 , and  13 , and the first, second, and third antennas  17 ,  18 , and  19  will be described in detail later. 
     Meanwhile, the switch  14  generates a signal (press signal) according to external manipulation (a switch press) and sends the generated signal to the controller  15 . As an example, the switch  14  may be a passive switch installed at a door handle. 
     Also, the controller  15  authenticates the smart key  2  or the portable terminal  3  on the basis of the signal sent from the switch  14  and the signal received through the communication units  11 ,  12 , and  13  and outputs a door control signal. 
     Also, the controller  15  may control the first and third communication units on the basis of transmission intervals of discovery signals of the first and third communication units  11  and  13 . 
     As an example, the controller  15  may authenticate the portable terminal  3  on the basis of a signal received through the third communication unit  13  or may authenticate the smart key  2  on the basis of signals received through the first communication unit  11 , the second communication unit  12 , and the switch  14 . A detailed operation of the controller  15  will be described later. 
     The motor driver  16  locks or unlocks a door under control of the controller  15 . 
     A configuration of the vehicle door control system according to an embodiment of the present invention has been described above. The communication units constituting the vehicle door control system according to an embodiment of the present invention will be described below in detail. 
       FIG. 2  is a diagram showing an example of an antenna module of a vehicle door control system according to an embodiment of the present invention, and  FIG. 3  is a diagram showing transmission intervals of an NFC discovery signal and an LF discovery signal that are transmitted from a vehicle door control system according to an embodiment of the present invention. 
     As described above, a vehicle door control system  1  according to an embodiment of the present invention includes three communication units that perform different types of wireless communication, that is, first, second, and third communication units  11 ,  12 , and  13 . 
     An example in which the first communication unit  11  performs LF communication, the second communication unit  12  performs RF communication, and the third communication unit  13  performs NFC communication will be described below. 
     In this case, the first, second, and third communication units  11 ,  12 , and  13  are connected with the first, second, and third antennas  17 ,  18 , and  19 , respectively, in order to perform communication. The first communication unit  11  is connected with an LF antenna, which is the first antenna  17 . The second communication unit  12  is connected with an RF antenna, which is the second antenna  18 . The third communication unit  13  is connected with an NFC antenna, which is the third antenna  19 . 
     In particular, according to the present invention, the first and third antennas  17  and  19  are produced in one body to form an antenna module  20 . As an example, as shown in  FIG. 2 , the antenna module  20  may be formed to have a first antenna coil  22  wound on a ferrite core  21  in one direction (i.e., a longitudinal direction) and a third antenna coil  23  wound on the ferrite core  21  in a direction perpendicular to the one direction (i.e., a lateral direction). 
     An end  22   a  of the first antenna coil  22  is connected with the first communication unit  11 , and an end  23   a  of the third antenna coil  23  is connected with the third communication unit  13 . 
     In this case, the antenna module  20  may be formed to have the third antenna coil  23  wound on the ferrite core  21  on which the first antenna coil  22  has already been wound. Also, the antenna module  20  may be formed to have the first antenna coil  22  wound on the ferrite core  21  on which the third antenna coil  23  has already been wound. 
     Also, since the antenna module  20  has a structure in which the first and third antennas  17  and  19  are formed in one body, the antenna module  20  may be installed at a door handle in which a conventional LF antenna has been installed. Thus, there is no need for additional space for installing the third antenna  19 . 
     The first communication unit  11  transmits an LF signal for discovering a smart key  2  that is located around the vehicle and authenticated (i.e., an LF discovery signal) through the first antenna  17  at certain intervals. The transmission interval of the LF discovery signal refers to an “LF transmission interval.” 
     Also, as a response to the LF discovery signal, the first communication unit  11  receives a response signal from the smart key  2  through the first antenna  17  and delivers the received response signal to the controller  15 . According to a request from the controller  15 , the first communication unit  11  transmits an authentication request signal to the smart key  2  through the first antenna  17 . 
     The second communication unit  12  receives an RF signal from the smart key  2  through the second antenna  18  and delivers the received RF signal to the controller  15 . 
     The third communication unit  13  transmits an NFC signal for discovering a portable terminal  3  that is positioned around the vehicle and authenticated (i.e., an NFC discovery signal) through the third antenna  19  at certain intervals. The transmission interval of the NFC discovery signal refers to an “NFC transmission interval.” 
     The first and third communication units  11  and  13  may be configured to transmit the LF discovery signal and the NFC discovery signal under control of the controller  15 . 
     In this case, the controller  15  controls the first and third communication units  11  and  13  such that the LF discovery signal and the NFC discovery signal are transmitted at different intervals. 
     In particular, the controller  15  transmits the NFC discovery signal through the third communication unit  13  a predetermined number of times. When the portable terminal  3  is not discovered while the NFC discovery signal is transmitted a predetermined number of times, the controller  15  transmits the LF discovery signal through the first communication unit  11 . 
     Since the first and third antennas  17  and  19  according to the present invention are formed on one ferrite core, distortion occurs between two signals when the two signals are simultaneously output from the first and third antennas  17  and  19 . 
     As shown in  FIG. 3 , the NFC transmission interval T 1  is set different from the LF transmission interval T 2 . Preferably, the NFC transmission interval T 1  is set shorter than the LF transmission interval T 2 . 
     The reason the NFC transmission interval T 1  is set shorter than the LF transmission interval T 2  is because the NFC discovery signal and the LF discovery signal have different characteristics and different output purposes. 
     That is, the LF communication is made within about 2 m from a vehicle. Outputting the LF discovery signal by periods is for a welcome light function. A vehicle door control is made based on an input corresponding to a manipulation of the switch  14 . 
     On the other hand, the NFC communication is made within 10 cm. Outputting the NFC discovery signal by periods is for a vehicle door control function. Since the NFC communication is made when a user accesses the vehicle and then immediately tries to control the door, a fast response is required. 
     The elements and their functions of the vehicle door control system according to an embodiment of the present invention have been described above. An operation of the vehicle door control system according to an embodiment of the present invention will be described below in detail with reference to the accompanying drawings. 
     First, a process in which the vehicle door control system  1  according to an embodiment of the present invention controls a vehicle door using LF communication and RF communication will be described. 
       FIG. 4  is a diagram for describing a process in which the vehicle door control system  1  according to an embodiment of the present invention controls a vehicle door using LF communication and RF communication. 
     In an embodiment of the present invention, it is assumed that a user intends to unlock a vehicle door that was initially locked. 
     Among the elements of the vehicle door control system  1 , the first, second, and third communication units  11 ,  12 , and  13  and the controller  15  are collectively referred to as one control module  4 . 
     Referring to  FIG. 4 , the control module  4  periodically transmits the LF discovery signal on the basis of the LF transmission interval in order to check whether a smart key  2  is present around the vehicle. In detail, the LF communication unit  11  periodically transmits the LF discovery signal through the LF antenna  17 . 
     When the smart key  2  is located within a communicable distance from the control module  4  to receive the LF discovery signal, the smart key  2  transmits a first response signal including an ID through an LF communication unit in response to the received LF discovery signal. In detail, the first response signal is received by the LF communication unit  11  through the LF antenna  17 , and the LF communication unit delivers the first response signal to the controller  15 . 
     The control module  4  receives the first response signal and compares the ID included in the first response signal with a preset ID to perform primary authentication on the smart key  2 . In detail, a process of performing primary authentication on the smart key  2  may be performed by the controller  15 . 
     When the primary authentication is successful, the control module  4  lights a lamp, for example, one of a puddle lamp of a side mirror and a pocket lamp of a door handle in order to perform a welcome light function. When the primary authentication fails, the control module  4  transmits the LF discovery signal in order to rediscover the smart key  2 . 
     When the primary authentication is successful and a press signal is sent from the switch  14 , the control module  4  transmits an authentication request signal to the smart key  2  in order to perform a secondary authentication process for controlling a vehicle door. 
     In detail, when the press signal is received from the switch  14 , the controller  15  instructs the LF communication unit  11  to transmit an authentication request signal, and the LF communication unit  11  transmits the authentication request signal to the smart key  2  through the LF antenna  17 . 
     When the authentication request signal is received, the smart key  2  transmits a second response signal including an ID to the control module  4  through an RF communication unit in response to the authentication request signal. In detail, the second response signal is transmitted to the RF communication unit  12  through the RF antenna  18 , and the RF communication unit  12  delivers the second response signal to the controller  15 . 
     When the second response signal is received, the control module  4  compares the ID included in the second response signal with a preset ID to perform secondary authentication on the smart key  2 . In detail, a process of performing secondary authentication on the smart key  2  may be performed by the controller  15 . 
     In this case, when the secondary authentication is successful, the control module  4  transmits a door control signal to the motor driver  16  to unlock the vehicle door. In detail, the controller  15  transmits the door control signal to the motor driver  16  through CAN communication. 
     On the other hand, when the secondary authentication fails, the control module  4  may transmit an authentication request signal to the smart key  2  again in order to perform re-authentication on the secondary authentication. Also, the control module  4  may transmit an LF discovery signal for discovering another smart key  2 . 
     Next, a process in which the vehicle door control system  1  according to an embodiment of the present invention controls a vehicle door using NFC communication will be described. 
       FIG. 5  is a diagram for describing a process in which the vehicle door control system according to an embodiment of the present invention controls a vehicle door using NFC communication. 
     In an embodiment of the present invention, it is assumed that a user intends to unlock a vehicle door that was initially locked. 
     Among the elements of the vehicle door control system  1 , the first, second, and third communication units  11 ,  12 , and  13  and the controller  15  are collectively referred to as one control module  5 . 
     Referring to  FIG. 5 , the control module  5  periodically transmits the NFC discovery signal on the basis of the NFC transmission interval in order to check whether a portable terminal  3  is present around the vehicle. In detail, the NFC communication unit  13  periodically transmits the NFC discovery signal through the NFC antenna  19 . 
     When the portable terminal  3  is located within a communicable distance from the control module  5  to receive the NFC discovery signal, the portable terminal  3  transmits a response signal including an ID through an NFC communication unit in response to the received NFC discovery signal. In detail, the response signal is transmitted to the NFC communication unit  13  through the NFC antenna  19 , and the NFC communication unit  13  delivers the response signal to the controller  15 . 
     When the response signal is received, the control module  5  compares the ID included in the response signal with a preset ID to perform authentication on the portable terminal  3 . In detail, a process of performing authentication on the portable terminal  3  may be performed by the controller  15 . 
     When the authentication of the portable terminal  3  is successful, the control module  5  transmits a door control signal to the motor driver  16  to unlock the vehicle door. In detail, the controller  15  transmits the door control signal to the motor driver  16  through CAN communication. 
     On the other hand, when the authentication of the portable terminal  3  fails, the control module  5  may transmit the NFC discovery signal to the smart key  2  again in order to perform re-authentication. 
     The vehicle door control process of the vehicle door control system according to an embodiment of the present invention has been described above on the basis of an authentication target. The entire operation of the vehicle door control system according to an embodiment of the present invention will be described below. 
       FIGS. 6 and 7  are flowcharts showing a sequence of a vehicle door control operation of a vehicle door control system according to an embodiment of the present invention. 
     In an embodiment of the present invention, it is assumed that a user intends to unlock a vehicle door that was initially locked. 
     Referring to  FIG. 6 , when the vehicle door control system  1  starts to operate, the system  1  transmits an NFC discovery signal through NFC communication according to a predetermined NFC transmission interval and counts the number of transmissions of the NFC discovery signal (S 600 ). 
     After S 600 , the system  1  determines whether a portable terminal  3  has been discovered (S 610 ). In this case, the system  1  may determine whether the portable terminal  3  has been discovered on the basis of whether a response signal is received from the portable terminal  3  as a response to the NFC discovery signal. 
     When it is determined in S 610  that the portable terminal  3  has been discovered (yes in S 610 ), the system  1  controls a vehicle door on the basis of a result of authentication of the discovered portable terminal  3  (S 620 ). 
     In detail, the system  1  performs authentication on the discovered portable terminal  3  (S 621 ), determines whether the authentication is successful (S 622 ), controls the vehicle door (S 623 ) when, from the authentication result, it is determined that the authentication is successful (yes in S 622 ), and feeds back to S 600  to output an NFC signal when the authentication has failed (no in S 622 ). 
     In this case, the system  1  performs authentication on the portable terminal  3  through an operation of comparing an ID included in a response signal transmitted from the portable terminal  3  with a preset ID, determines that the authentication is successful when the two IDs match each other, and determines that the authentication has failed when the two IDs do not match. 
     On the other hand, when it is determined in S 610  that the portable terminal  3  has not been discovered (no in S 610 ), the system  1  determines whether a value counted in S 600  (a count value) is equal to or greater than a predetermined value (S 630 ). 
     When it is determined in S 630  that the count value is less than the predetermined value (no in S 630 ), the system  1  feeds back to S 600  to output an NFC signal. 
     On the other hand, when it is determined in S 630  that the count value is equal to or greater than the predetermined value (yes in S 630 ), the system  1  transmits an LF discovery signal through LF communication according to a predetermined LF transmission interval and initializes the number of transmissions of the NFC discovery signal (S 640 ). 
     After S 640 , the system  1  determines whether a smart key  2  has been discovered (S 650 ). In this case, the system  1  may determine whether the smart key  2  has been discovered on the basis of whether a response signal is received from the smart key  2  as a response to the LF discovery signal. 
     When it is determined in S 650  that the smart key  2  has not been discovered (no in S 650 ), the system  1  feeds back to S 600  to transmit the NFC signal. 
     On the other hand, when it is determined in S 650  that the smart key  2  has been discovered (yes in S 650 ), the system  1  controls a vehicle door on the basis of a result of authentication of the discovered smart key  2  (S 660 ). 
     The step S 660  will be described in detail with reference to  FIG. 7 . The system  1  performs primary authentication on the discovered smart key  2  (S 661 ) and determine whether the authentication is successful (S 662 ). 
     In this case, the system  1  determines whether the ID included in the response signal transmitted from the smart key  2  matches a preset ID to perform primary authentication on the smart key  2 . 
     When it is determined in S 662  that the primary authentication is successful (yes in S 662 ), the system  1  performs a predetermined function, for example, a welcome light function (S 663 ). When it is determined that the primary authentication fails (no in S 662 ), the system  1  feeds back to a predetermined step, for example, S 600  to transmit an NFC discovery signal. 
     After S 663 , when the switch is pressed, the system  1  transmits an authentication request signal to the smart key  2  through LF communication in order to perform secondary authentication on the smart key  2  (S 664 ). 
     After S 664 , the system  1  receives a response signal from the smart key  2  through RF communication as a response to the authentication request signal, performs secondary authentication on the smart key  2  (S 665 ), and determines whether the secondary authentication is successful (S 666 ). 
     In this case, the system  1  determines whether the ID included in the response signal transmitted from the smart key  2  matches a preset ID to perform secondary authentication on the smart key  2 . 
     When it is determined in S 666  that the secondary authentication is successful (yes in S 666 ), the system  1  controls a vehicle door (S 667 ). When it is determined that the secondary authentication fails (no in S 666 ), the system  1  may feed back to a predetermined step, for example, S 600  to transmit an NFC discovery signal or may feed back to S 664  to transmit an authentication request signal. 
     The operations shown in  FIGS. 6 and 7  should be understood as showing various processes that can be performed by a computer or a processor, regardless of whether the operations can substantially be recorded in a computer-readable medium or a computer or processor has been clearly shown. 
     Also, the definite use of terms such as “processor,” “control” or the like is not to be construed exclusively using hardware that can execute software, and it should be understood as implicitly including, but is not limited thereto, digital signal processor (DSP) hardware and a read-only memory (ROM), a random access memory (RAM), and a nonvolatile memory for storing software, without limitation. It will be appreciated that other well-known hardware may be included. 
     So far, the vehicle door control system and the operating method thereof according to the present invention have been described according to embodiments. However, the present invention is not limited to an exemplary embodiment. It will be apparent to those skilled in the art that various alternatives, modifications, and variations can be made to the present invention without departing from its spirit and scope. 
     By using a vehicle door control technology according to an embodiment of the present invention, it is possible to control a vehicle door using NFC communication as well as the conventional LF communication and RF communication. 
     Accordingly, authentication can be performed using a portable terminal even though a user does not carry a smart key, thus improving user convenience. 
     Also, since an NFC antenna for the NFC communication and a conventional LF antenna are formed in one body, an antenna module composed of the NFC antenna and the LF antenna can be installed at a door handle, as in the related art. 
     Accordingly, it is also possible to provide a vehicle door control technology with enhanced performance, compared to the related art, without a space limitation for installing the NFC antenna. 
     Accordingly, the embodiments and the accompany drawings of the present invention are to be considered descriptive and not restrictive, and do not limit the technical scope of the present invention. The scope of the present invention should be to be construed by the appended claims, and all technical ideas within the scope of their equivalents should be construed as being included in the scope of the present invention.