KR100676940B1 - Pseudo-time reference signal generating method and apparatus of automatic identification system - Google Patents

Abstract

The present invention provides a method and apparatus for generating a similar time reference signal of an automatic vessel identification system for receiving vessel information and transmitting information of own ships even when a GPS receiver malfunctions in the vessel automatic identification system. A method for generating a similar time reference signal of an automatic ship identification system includes computing a received signal transmitted from another ship to obtain a correlation value, and when the correlation value is greater than a preset signal reference point threshold, forming a first waveform; Obtaining an RSSI output value corresponding to the received electric field strength of the received signal and forming a second waveform when the RSSI output value is larger than a preset RSSI threshold value; Synthesizing the first waveform and the second waveform and outputting a third waveform; Compensating the time delay value of the first waveform and the propagation delay value of the second waveform through clock time delay compensation, and rotating the phase of the third waveform forward to form a pseudo time reference signal.

Description

Method and device for generating similar time reference signal of ship automatic identification system {PSEUDO-TIME REFERENCE SIGNAL GENERATING METHOD AND APPARATUS OF AUTOMATIC IDENTIFICATION SYSTEM}

1 is a block diagram illustrating a ship automatic identification system to which the method and apparatus for generating a similar time reference signal according to the present invention are applied;

2 is a block diagram illustrating a pseudo time reference signal generator according to a preferred embodiment of the present invention;

3 is a flowchart for explaining a method for generating a similar time reference signal according to a preferred embodiment of the present invention;

4 is a view for explaining an example of a table corresponding to an RSSI output value for an RSSI size in a method for generating a pseudo-time reference signal according to the present invention;

5 is a timing diagram for explaining the shape of the waveform formed using the method and apparatus for generating a pseudo-time reference signal according to the present invention.

Explanation of symbols on the main parts of the drawings

10: Ship automatic identification system 20: RF module

22: GMSK demodulator 24: HDLC processor

26: (main) processor 28: GPS receiver

30: pseudo-time reference signal generator 32: switch

34: correlator 36: first comparator

38: RSSI Converter 40: Second Comparator

42: waveform synthesizer 44: clock time delay compensator

46: compensation signal generator 48: determination unit

The present invention relates to a method and apparatus for generating a similar time reference signal of an automatic vessel identification system. More specifically, the vessel automatic identification system can receive information of other ships and transmit own vessel information even when a GPS receiver malfunctions. The present invention relates to a method and apparatus for generating a similar time reference signal of a ship automatic identification system.

The Automatic Identification System (AIS) of the ship transmits the navigational information of the ship at regular intervals and receives the navigational information of other ships to prevent collision with other ships through the location information of the ship and provide them for safe navigation. do.

As disclosed in Korean Patent Application Laid-Open No. 2001-0104897 "A device for transmitting and receiving data for automatic identification system and method thereof" and 2002-0033064 "shipboard unit for automatic identification system", the automatic identification system for ships Ship-to-ship and ship-to-shore center-to-shore (Ship to Shore) information on the ship's specifications, location, course, speed, etc. It is a system to contribute to the operation.

Meanwhile, the International Ship and Port Facility Security (ISPS) Convention, which entered into force on 1 July 2004, mandates the installation of an automatic ship identification system on ships of 500 tons or more.

Such automatic vessel identification system is to transmit the navigation information of the own ship and receive the navigation information of other ships by the Self-Organized Time Division Multiple Access (SOTDMA) method. At this time, the time reference signal required for communication between ships is defined in the International Telecommunication Union (ITU) (Rec. ITU-R M.1371-1; Technical characteristics for a universal shipborne automatic identification system using time division multiple access in According to the VHF maritime mobile band, 1PPS (Pulse Per Second) signal of GPS (Global Positioning System) receiver embedded in ship automatic identification system is used.

However, this rule provides a countermeasure for the case where it is impossible to generate a time reference signal that can transmit and receive navigation information between ships due to a malfunction of the GPS receiver. By making the identification system operate stably, it is required to receive information of other ships and to transmit information of own ships.

Therefore, the present invention satisfies such a regulation, and is easily applied to a conventional ship automatic identification system, so that the ship's automatic identification can be used to receive other ship's information and transmit own ship's information even when the GPS receiver malfunctions. It is an object of the present invention to provide a method and apparatus for generating a pseudo-time reference signal of a system.

According to a feature of the present invention for achieving the above object, the present invention is a similar time of the automatic vessel identification system for receiving the information of other ships and transmitting the information of own ship even in the malfunction of the GPS receiver in the vessel automatic identification system A reference signal generation method, comprising: obtaining a correlation value by calculating a received signal transmitted from another line and forming a first waveform when the correlation value is larger than a preset signal reference point threshold value; Obtaining a RSSI output value corresponding to a received electric field strength of the received signal, and forming a second waveform when the RSSI output value is larger than a preset RSSI threshold value; Synthesizing the first waveform and the second waveform and outputting a third waveform; And compensating for the time delay value of the first waveform and the propagation delay value of the second waveform through clock time delay compensation to form a pseudo time reference signal by turning the phase of the third waveform forward.

In the method of generating a similar time reference signal of the automatic vessel identification system according to the present invention, the time reference waveform for backup is generated by combining the RTC clock signal and the 1PPS signal with the pseudo time reference signal formed by compensating the third waveform clock time delay. And synthesizing with each other to form a final pseudo-time reference signal.

In the method of generating a similar time reference signal of the automatic vessel identification system according to the present invention, the forming of the first waveform and the second waveform may be output by shifting each waveform to "1".

According to another aspect of the present invention for achieving the above object, the present invention is similar to the automatic vessel identification system for receiving the information of other ships and transmitting the information of own ship even when the GPS receiver malfunctions in the vessel automatic identification system A method of generating a time reference signal, the method comprising: generating a similar time reference signal generation control signal when a 1PPS interrupt signal of the GPS receiver is not detected by a processor to operate a similar time reference signal generator; Outputting the first waveform by translating the waveform to "1" when the signal transmitted from the other line is inputted to the correlator to be input to the correlator, and then being processed by a first comparator; Wow; After measuring the RSSI size from the RF signal transmitted from other lines and converting it through the RSSI converter, the second waveform is outputted by shifting the waveform to "1" when it is larger than the RSSI threshold already set in the processor through the second comparator. Steps; Synthesizing the first waveform and the second waveform through a waveform synthesizer and outputting a third waveform; Compensating for the time delay value of the first waveform and the propagation delay value of the second waveform through a clock time delay compensator to rotate the phase of the third waveform forward to form a pseudo time reference signal.

The method for generating a similar time reference signal of the automatic vessel identification system according to the present invention uses the RTC clock signal and the 1PPS signal of the GPS receiver when the 1PPS interrupt signal of the GPS receiver is detected by the processor. Occurring; The method may further include synthesizing the third waveform of the clock time delay compensation through the clock time delay compensator with the backup time reference waveform to form a final pseudo time reference signal.

According to another feature of the present invention for achieving the above object, the present invention provides an automatic vessel identification system for receiving the information of other ships and transmitting the information of own ships even when the GPS receiver malfunctions in the vessel automatic identification system. In the pseudo-time reference signal generator, a control signal for generating a pseudo-time reference signal when a 1PPS interrupt signal of the GPS receiver is not detected, and a portion corresponding to a preamble in a predetermined data format of a received signal transmitted from another line A processor for acquiring and transmitting a signal reference point threshold value for specifying a reference point of the received signal, and transmitting an RSSI threshold value for specifying a propagation distance of the received signal transmitted from another line; The operation for generating a similar time reference signal is started by a control signal generated by the processor, and the similar time reference signal is processed by processing a received signal transmitted from another line using the signal reference point threshold value and the RSSI threshold value transmitted from the processor. It includes a pseudo-time reference signal generator for generating by forming a.

In the apparatus for generating a similar time reference signal of the automatic vessel identification system according to the present invention, the similar time reference signal generator includes a correlator for calculating a correlation value by processing a received signal transmitted from another ship; A first comparator for comparing a signal reference point threshold input from the processor with a correlation value of the correlator to form a first waveform when the correlation value is greater than the signal reference point threshold; An RSSI converter for obtaining an RSSI output value corresponding to a received electric field strength of the received signal; A second comparator for comparing a RSSI threshold value input from the processor with an RSSI output value of the RSSI converter to form a second waveform when the RSSI output value is larger than the RSSI threshold value; A waveform synthesizer for synthesizing the first waveform and the second waveform and outputting a third waveform; And a clock time delay compensator for compensating the time delay value of the first waveform and the propagation delay value of the second waveform.

In the apparatus for generating a similar time reference signal of the automatic vessel identification system according to the present invention, the pseudo time reference signal generator is a RTC clock signal used by the processor and the GPS when a 1PPS interrupt signal of the GPS receiver is detected by the processor. A compensation signal generator for synthesizing a 1PPS signal of a receiver to generate a backup time reference waveform, and generating the backup time reference waveform when a control signal for generating a similar time reference signal is generated in the processor; The apparatus may further include a determiner configured to generate a final pseudo time reference signal by synthesizing the pseudo time reference signal output from the clock time delay compensator and the backup time reference waveform generated by the compensation signal generator.

The method of generating a similar time reference signal of the automatic vessel identification system according to the present invention basically compensates the error according to time and distance of the signal received from other ship (including the ground transmitting station) to the maximum by 1PPS through the GPS receiver. Generate a pseudo-time reference signal that matches the signal.

To this end, the method for generating a pseudo-time reference signal according to the present invention designates a signal reference point threshold (Cref) of a specific size in order to accurately find the reference point of the received signal, and compares it with the correlation value of the signal received from other lines. If large, the waveform of the received signal is obtained to form a pseudo-time reference signal. Also, in order to minimize the error required for setting the time reference according to the distance of the received signal, a RSSI (Received Signal Strength Indication) threshold value (Rref) of a specific size is specified, and the RSSI size (measurement value) of the RF signal received from another line and By converting to the corresponding RSSI converted value, if the RSSI converted value is larger than the RSSI threshold, the waveform of the received signal is obtained for the pseudo-time reference signal. In the method for generating a similar time reference signal according to the present invention, the two waveforms thus obtained are synthesized and compensated for processing time delay and distance delay and used as the similar time reference signal.

On the other hand, the method for generating a pseudo-time reference signal according to the present invention combines the output waveform of the clock time delay compensation as described above with the backup control waveform in order to further increase the accuracy of the pseudo-time reference signal to form a final pseudo-time reference signal. In other words, the pseudo-time reference signal formed as described above is accurate, but synthesized with a waveform obtained by synthesizing the 1PPS signal and the RTC clock signal of the GPS destination before the problem occurs (just before the generation of the pseudo-time reference signal). Through the verification process to form a more accurate similar time reference signal.

1 is a block diagram illustrating a ship automatic identification system to which the method and apparatus for generating a similar time reference signal according to the present invention are applied.

Referring to FIG. 1, the vessel automatic identification system 10 to which a method and apparatus for generating a similar time reference signal according to the present invention is applied is an RF module 20 constituting a conventional vessel automatic identification system and a GMSK (Gaussian Minimum Shift Keying). A demodulator 22, a modem, a high-level data link control (HDLC) processor 24, a (main) processor 26, and a GPS receiver 28. In addition, the similar time reference signal generator 30 is electrically connected to such a component, and constitutes a ship automatic identification system 10 having a function of generating a similar time reference signal in an emergency.

The similar time reference signal generator of the automatic vessel identification system 10 is provided with a (main) process 26 and a similar time reference signal generator 30 specially designed to achieve the object of the present invention. At this time, the process 26 generates a control signal for generating a similar time reference signal when the 1PPS interrupt signal of the GPS receiver is not detected, and the part corresponding to the preamble in the predetermined data format of the received signal transmitted from the other line. Acquire and transmit a signal reference point threshold (Cref) for specifying the reference point of the received signal, and RSSI threshold value (Rref) for specifying the propagation distance of the received signal transmitted from the other line to the pseudo-time reference signal generator 30 to provide. In addition, the pseudo-time reference signal generator 30 starts an operation for generating a pseudo-time reference signal by a control signal generated by the processor 26, and the signal reference point threshold Cref and the RSSI threshold transmitted from the processor 26. By using the value Rref, the received signal transmitted from other line is processed to form a similar time reference signal and send it to the required terminal.

According to the method and apparatus for generating a similar time reference signal of the automatic vessel identification system according to the present invention, a more accurate similar time reference signal using information automatically received from the outside and clock information used inside the vessel automatic identification system is provided. Since it is possible to transmit the information of own ship even when time-reference signal cannot be generated due to malfunction of GPS receiver embedded in ship automatic identification system, it is possible to prevent collision of information transmission of other ships. As a result, the 4S (Ship-to-Ship, Ship-to-Shore) of the ship automatic identification system can be smoothly communicated, thus satisfying the international regulations on the ship automatic identification system.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. On the other hand, in each drawing, the conventions and regulations for the standard of the ship automatic identification system, the city and the detailed description of the technical contents that can be easily applied from the configuration and operation of the conventional general vessel automatic identification system can be easily understood by those in this field. Since parts are to be understood, they are briefly or omitted, and are shown in terms of parts related to the present invention.

FIG. 2 is a block diagram illustrating a pseudo time reference signal generator according to a preferred embodiment of the present invention. FIG. 3 is a flowchart illustrating a method of generating a similar time reference signal according to a preferred embodiment of the present invention. 4 is a view for explaining an example of a table corresponding to the RSSI output value for the RSSI size in the pseudo-time reference signal generation method according to the present invention.

1 and 2, a pseudo-time reference signal generator 30 according to a preferred embodiment of the present invention may include a switch 32, a correlator 34, a first comparator 36, and an RSSI converter 38. And a second comparator 40, a waveform synthesizer 42, a clock time delay compensator 44, a compensation signal generator 46, and a determination unit 48.

Such a configuration is preferably designed with pure digital hardware. The RSSI converter 38 may be separately installed and connected as necessary. In case of designing with pure digital hardware, an input terminal for inputting a signal from the processor 26 to the switch 32, the first comparator 36, the RSSI converter 38, the second comparator 40, and the compensation signal generator 46 is provided. Is configured, and the determination unit 48 is configured with an output terminal. At this time, the control signal is input from the processor 26 through the input terminal to the switch 32 and the compensation signal generator 46, and the signal reference point threshold Cref from the processor 26 through the input terminal to the first comparator 36. ), The RSSI threshold Rref is input from the processor 26 to the second comparator 46, and the received signal input to the correlator 34 through the input terminal of the switch 32 is a GMSK demodulator 22. The signal is transmitted by the other line provided from the output terminal of the C-type input signal, and the RSSI converter 38 receives an intensity value (RSSI measurement value) of the received signal measured by the RF (radio frequency) module 20 through an input terminal. The RSSI conversion value by the corresponding transformation as shown in FIG. 3 is provided to the second comparator 40. The compensation signal generator 46 receives an absolute time reference clock provided by the GPS receiver 28 and a clock used by the processor 26 through an input terminal during normal operation of the GPS receiver 28.

Referring back to FIGS. 1 and 2, the switch 32 is opened and closed by the control signal 1 generated by the processor 26. The processor 40 monitors the 1PPS interrupt signal of the GPS receiver 28 and generates a control signal if the interrupt signal is not generated for a certain period of time, and this switch 32 is generated by the control signal of the processor 40. Is activated to activate the pseudo-time reference signal generator 30. When the switch 32 is connected, the demodulated data through the GMSK demodulator 22 is input to the correlator 34.

The correlator 34 functions as a matched filter to find 110011001100110011001100, which is an input data pattern (Preamble) specified in the international regulation (Rec. ITU-R M.1371-1). The correlator 34 generates a maximum output value when the same data pattern is input. When the received signal has no error, a maximum of 24 correlation values are output. The first comparator 36 compares the output value Co of the correlator 34 with the designed signal reference point threshold Cref and generates an output waveform as "1" when the condition of (Co-Cref)> 0 is satisfied. The shape of such a waveform is the same as the waveform of FIG. The RSSI converter 38 receives the strength (RSSI measurement value) of the received signal through the RF module 20, extracts and digitally processes the RSSI size and the RSSI converted value from a table configured as shown in FIG. The converted value Ro is transmitted to the second comparator 40. The second comparator 40 receives the RSSI threshold value Rref from the processor 26 and generates a waveform of “1” when the condition of (Ro − Rref)> 0 is satisfied. Here, the RSSI converted value Ro is calculated by taking a moving average for 24 bits.

The waveform synthesizer 42 receives the output waveforms of the first comparator 36 and the second comparator 40, serves as an AND logic circuit, and synthesizes the two waveforms. In addition, the clock time delay compensator 44 inverts the waveform signal (waveform (a) in FIG. 5) generated to find the transmission start time of the signal transmitted from the nearest position, and time delayed by the correlator 34 (t1). And compensation for the propagation delay time (t2). The waveform output from the clock time delay compensator 44 is the same as the waveform (d) in FIG. 5.

The compensation signal generator 46 generates a backup time reference waveform by synthesizing the 1PPS signal with the RTC CLK used by the processor 40 when the GPS receiver 28 operates normally. The backup reference time waveform generated from the upper point to the previous point is output to the determination unit 48. The pulse width of the backup time reference is 312us at the maximum. The determination unit 48 generates a pseudo time reference signal by combining the output of the clock time delay compensator 44 and the backup time reference waveform output from the compensation signal generator 46. At this time, the characteristics of the time-based waveform for backup can be used as a criterion because it can have an allowable range of frequency drift, which is a long-term frequency flow phenomenon. And the output signal is sent to the terminal necessary to use as time reference to transmit the navigation information of own ship in UTC-Indirect Mode.

5 is a timing diagram for explaining the shape of the waveform formed using the method and apparatus for generating a pseudo-time reference signal according to the present invention.

1 to 5, when the GPS receiver 28 operates normally to generate a 1 PPS signal that is UTC (Universal Time Co-ordinated), the processor 26 may generate an RTC clock signal and a 1PPS signal of the GPS receiver 28. Synthesizing to generate a time reference waveform for the backup (S510). In addition, when the 1PPS signal which is UTC (Universal Time Co-ordinated) is not generated due to a malfunction of the GPS receiver 28, the processor 26 which always detects this (S500) does not have a 1PPS interrupt signal and thus provides a pseudo-time reference signal. A control signal for generating is generated (S520).

When the control signal is generated in the processor 26, the switch 32 transitions to the "ON" state, which is in the conduction state, so that the pseudo-time reference signal generator 30 can receive external information. At this time, a signal transmitted and demodulated from the GMSK demodulator 22 on another line is input to the correlator 34, and a calculation process for obtaining a correlation value is performed (S560). The correlation value obtained by the correlator 34 is an element for generating a similar time reference signal by finding a part corresponding to the preamble in a data format determined according to international regulations. Since the signal input to the correlator 34 is continuously received in bit units, the output of the correlator 34 outputs up to 24 output values of the correlator 34 only when the '110011001100110011001100' signal, which is an input data pattern to be searched, is input. do. Of course, the value may vary depending on whether there is an error in the reception signal of another line. The correlation value output through the correlator 34 to accurately find the reference point of the signal is input to the first comparator 36 and compared with the signal reference point threshold Cref of a given specific magnitude so that the correlation value Cv is large. The output of the first comparator 36 is maintained at a state of "1" (S570 and S580). The waveform generated when this condition is met will have the form as shown in FIG. If it is, the waveform as shown in (a) of FIG. 3 (Timing Table) may be generated.

Meanwhile, the RSSI size measured by the RF module 20 through the RSSI converter 38 is input to the second comparator 40 as an RSSI converted value Ro, which is obtained to correspond to the RSSI size as shown in FIG. 4 (S530). . From the moment the radio wave is radiated through the antenna, the intensity of the radio wave is attenuated, which is inversely proportional to the exponential power of the distance. In general, when the magnitude of the RF signal of the receiving antenna is measured, the propagation distance can be inferred. The processor 26 sets an RSSI threshold value Rref for specifying a propagation distance. The signal size of the RSSI conversion value Ro is determined by comparing the measured RSSI converted value Ro and the RSSI threshold value Rref. If larger than the RSSI threshold value (Rref) (S540), it can be determined that the magnitude of the propagation delay is short, it is possible to minimize the error required for setting the time reference. Accordingly, when the output of the second comparator 40 satisfies the above condition, the output waveform transitions to "1" (S550). In this case, the signal reference point threshold Cref and the RSSI threshold Rref are values set by the processor 26.

After the process is completed, the waveform synthesizer 42 maintains the state of "1" only when the first comparator 36 and the second comparator 40 satisfy the same condition (S590). The same waveform as in FIG. 5A is generated. The clock time delay compensator 44 is a waveform of FIG. 5 to compensate for a clock time delay for compensating a time delay value generated during correlation operation in the correlator 34 and a propagation delay value of the second comparator 40. As shown in FIG. 6, the phase of the signal output from the waveform synthesizer 42 is returned.

The signal obtained through the clock time delay compensator 44 may be used as a similar time reference signal. However, in the present invention, the RTC CLK signal and 1PPS used in the processor 26 to increase the accuracy of the time reference point selection are used in the present invention. The signal is used to generate a backup time reference waveform (same as waveform (c) in FIG. 5) at a normal operation point when the control signal is not generated (S510). In this state, the compensation signal generator 46 applies the backup time reference waveform to the determination unit 48 from the time when the control signal is applied from the processor 26. The determination unit 48 combines the output of the clock time delay compensator 44 and the signal applied from the output of the compensation signal generator 46 to generate the final pseudo-time reference signal {waveform of FIG. It can be used to transmit the information of the own ship.

As described above, the method and apparatus for generating a similar time reference signal of the automatic vessel identification system according to the preferred embodiment of the present invention are shown in accordance with the above description and drawings, but this is merely an example and the technical spirit of the present invention. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the scope of the invention.

According to the method and apparatus for generating a similar time reference signal of an automatic vessel identification system according to the present invention, since a more accurate similar time reference signal is generated using information automatically received from the outside and clock information used inside the vessel automatic identification system. In addition, it is possible to transmit the information of own ship even when time-reference signal cannot be generated due to malfunction of GPS receiver embedded in ship automatic identification system, so that the collision of other ship's information can be prevented. 4S (Ship-to-Ship, Ship-to-Shore) of the identification system can be facilitated to meet the international regulations on ship automatic identification system.

Claims (8)

In the method of generating a similar time reference signal of the ship automatic identification system for receiving the information of other ships and transmitting the information of own ship even when the GPS receiver malfunctions in the ship automatic identification system, Generating a pseudo-time reference signal generation control signal when the 1PPS interrupt signal of the GPS receiver is not detected by the processor to operate the pseudo-time reference signal generator; Outputting the first waveform by translating the waveform to "1" when the signal transmitted from the other line is inputted to the correlator to be input to the correlator, and then being processed by a first comparator; Wow; After measuring the RSSI size from the RF signal transmitted from other lines and converting it through the RSSI converter, the second waveform is outputted by shifting the waveform to "1" when it is larger than the RSSI threshold already set in the processor through the second comparator. Steps; Synthesizing the first waveform and the second waveform through a waveform synthesizer and outputting a third waveform; Compensating the time delay value of the first waveform and the propagation delay value of the second waveform through a clock time delay compensator to rotate the phase of the third waveform forward to form a similar time reference signal A method for generating a similar time reference signal of an automatic identification system. The method of claim 1, Generating a backup time reference waveform using an RTC clock signal and a 1PPS signal of the GPS receiver when the processor detects a 1PPS interrupt signal of the GPS receiver; And synthesizing the third waveform compensated for the clock time delay through the clock time delay compensator with the backup time reference waveform to form a final pseudo time reference signal. Method of generating a similar time reference signal. In the ship automatic identification system similar time reference signal generator of the ship automatic identification system for receiving the information of other ships and transmitting the information of own ship even when the GPS receiver malfunctions, When the 1PPS interrupt signal of the GPS receiver is not detected, a control signal for generating a similar time reference signal is generated, and a reference point of the received signal is specified by acquiring a portion corresponding to the preamble in a predetermined data format of the received signal transmitted from another line. A processor for transmitting a signal reference point threshold for transmitting an RSSI threshold for specifying a propagation distance of a received signal transmitted from another line; The operation for generating a similar time reference signal is started by a control signal generated by the processor, and the similar time reference signal is processed by processing a received signal transmitted from another line using the signal reference point threshold value and the RSSI threshold value transmitted from the processor. It includes a similar time reference signal generator for generating by forming; The quasi-time reference signal generator includes a correlator for processing a received signal transmitted from another line to obtain a correlation value; A first comparator for comparing a signal reference point threshold input from the processor with a correlation value of the correlator to form a first waveform when the correlation value is greater than the signal reference point threshold value; An RSSI converter for obtaining an RSSI output value corresponding to a received electric field strength of the received signal; A second comparator for comparing a RSSI threshold value input from the processor with an RSSI output value of the RSSI converter to form a second waveform when the RSSI output value is larger than the RSSI threshold value; A waveform synthesizer for synthesizing the first waveform and the second waveform and outputting a third waveform; And a clock time delay compensator for compensating the time delay value of the first waveform and the propagation delay value of the second waveform. The method of claim 3, wherein The pseudo-time reference signal generator generates a backup time reference waveform by synthesizing the 1PPS signal of the GPS receiver and the RTC clock signal used in the processor when the processor detects the 1PPS interrupt signal of the GPS receiver. A compensation signal generator for generating the backup time reference waveform when a control signal for generating a similar time reference signal is generated; And a determination unit for generating a final similar time reference signal by synthesizing the similar time reference signal output from the clock time delay compensator and the backup time reference waveform generated by the compensation signal generator. Similar time reference signal generator. delete delete delete delete

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