KR19980041639A - High Precision Vision Synchronizer Using Ground Position Measurement System (GPS) - Google Patents

Abstract

The present invention relates to a high-precision time synchronization device using a ground position measuring system for outputting the 1PPS received from a GPS satellite and the main clock output from the system itself in a high performance microprocessor unit.

To this end, an antenna for receiving a 1PPS visual signal radiated from a GPS satellite, and connected to the antenna to output 1PPS, and outputs data about the 1PPS reception signal, a back-up voltage detection signal, and year, month and day. It is connected between the GPS receiver and the output terminal of the GPS receiver to control the system by a predetermined program and to count and correct the main clocks during the 1PPS of the GPS receiver, and to synchronize and output the main clock, and to the input and output terminals of the main controller. Precise time oscillation circuit that generates 10MHz main clock constantly, connected to the output terminal of main controller, initializes the system and displays 1PPS reception, 1PPS and 10MHz output from GPS satellite, and generates an alarm when a system error occurs. It is connected to the reset and display unit, the output terminal of the main control unit outputs the synchronized frequency of 1PPS and 10MHz, It is composed of an output drive for communication with other devices, a frequency synthesizer connected to the 10MHz output terminal of the main control unit to output any frequency desired by the user in synchronization with 10MHz.

Description

High Precision Vision Synchronizer Using Ground Position Measurement System (GPS)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-precision time synchronization device using a GPS (Global Positioning System) (GPS). In particular, 1PPS received from a GPS satellite and a predetermined frequency output from a precision visual oscillation circuit are used. The present invention relates to a high-precision time synchronizer using a ground position measuring system that allows the processor unit (MPU) to programmatically and accurately synchronize the output.

The high-precision visual synchronization device described in the present invention has a wide range of applications, and is applicable to the mobile communication field, power system, metrology, distributed processing system, and optical communication network. The technical scope of the system field is as follows.

First, it is installed in a base station of code division multiple access (CDMA) used in PCS (Personal Communications Service), which is currently expected to be used in Korea, and mobile communication using code division multiple access. In this case, high-precision visual synchronization is essential.

For example, if a user moves from one place to another during communication, if the system is not synchronized between the two base stations, it may cause a fatal error such as disconnection, as well as code division multiple access communication. The number of users of wireless mobile communication is increasing exponentially every year, so the importance is very high.

Therefore, in Korea, standards are not set for each mobile communication as a matter of protocol. Therefore, it is necessary to prepare a separate base station according to the communication method, so it is necessary to prepare for this. Most high-precision time synchronizers include time division including code division multiple access. Developments are being made for the telecommunication markets such as Time Division Multiple Access (TDMA) and Paging.

Second, precision vision synchronizers can be installed in power-related systems, and the most common one can be used to synchronize the tagging / logging subsystems for each system and time of accident.

That is, the interconnected wires of the unexpected situation occurs, these errors are detected quickly and can FT IU of each system to cope with unless such disconnection (FTIU: Fault transient lnterface Unit) is a time logging in a precisely synchronized state (Time Tagging) This requires a time synchronizer with a relatively high precision, and can also aid in the processing of sequential control and management data.

In addition, the power system is applied to various fields such as RTU (Remote Terminal Unit) of SCADA (Supervisory Control And Data Acquisition) system and stable control of power system.

Therefore, the high-precision time synchronizer applied to the above fields requires a reference time in Universal Time Coordinated (UTC), and the reference time signal is received from a GPS satellite.

That is, a 1PPS (Pulse Per Second) time signal transmitted from a GPS satellite is transmitted based on the time of the US Standard World Coordinated Time through two cesium atomic clocks and two rubidium atomic clocks mounted in the satellite itself.

Looking at the precise time synchronization device using the 1PPS transmitted from the conventional GPS satellites as follows.

<Prior Art 1>

Figure 1 (a) is composed of a time synchronization device using Hewlett Packard's SmartClock technology, processing a low-cost oscillator as a reference signal and combines the GPS satellite 1PPS as an external signal, high precision and low price At the same time, in the case of Holdover mode, in which the external reference signal 1PPS is incapable of receiving, the error tolerance is provided to a value already predicted in a normal state, and the operation method is the external of the oscillator and the 1PPS. The microprocessor compares the reference signal and returns the error value to the oscillator to improve the accuracy by adjusting the oscillator frequency.

〈Private Technology 2〉

Figure 1 (b) is a form of independent isochronous maintenance block for improving the isochronism between each frequency in the improved technique of Hewlett-Packard's company, unlike the prior art 1, this method is within 1 × 10 ^-10 within at least one day Because the frequency can be adjusted up to, combining GPS clock with rubidium or high-quality crystal oscillator can achieve stability enough to approach cesium's performance, and the part of the isochronous maintenance block is the frequency repeater.

<Prior Art 3>

Figure 1 (c) of another prior art DATUM (PRS: Primary Reference Systems) relates to the network market, such as ATM (Asynchronous Transfer Mode) than the conventional mobile communication market and It is a product for wired or wireless communication network, and is similar to Hewlett-Packard's HP55300A.

In other words, DATUM's PRS (PRS) uses the main clock oscillator portion not only rubidium but also a crystal oscillator, and uses GPS as an external reference reception signal.

Such a conventional time synchronizer shown in FIGS. 1A to 1D mainly relies on hardware to maintain time synchronization and isochronousness, which not only complicates the system itself but also increases the volume of the product itself. It becomes very large and also maintains a high price in terms of price. Therefore, it is not universalized, and there is a problem of deterioration in reliability as a visual synchronizer by having a large variation in precision.

The present invention is to solve the problems of the above, it is to be output in synchronization with the 1PPS transmitted from the GPS satellite 10MHz main clock generated in the precision time oscillation circuit by a program set in a high precision microprocessor unit Thus, when applied to the mobile communication it is an object of the present invention to precisely synchronize the time of each base station to prevent the disconnection of the mobile terminal in the call state.

Another object of the present invention is to maintain the main clock synchronization through the prediction value of the timeout (Overtime) according to environmental factors in the microprocessor unit in the case of a holdover state in which 1PPS is not received from the GPS receiver. By doing so, the time of each base station can be synchronized even when a fatal error of the GPS receiver occurs.

Another object of the present invention is to send a correction data value to the precision time oscillator circuit when the 10 MHz main clock is not exactly synchronized with 1 PPS transmitted from the GPS satellite so that the 10 MHz main clock is constantly output. 1PPS is to be able to synchronize exactly.

Still another object of the present invention is to provide a frequency synthesizer so as to obtain a predetermined frequency other than the 1PPS and 10MHz output desired by the user, and to display the operation mode and state of the current system through the display device, Its purpose is to reduce the size of the product due to its simple configuration and to supply it at low cost.

In order to achieve the above object, the present invention provides an antenna for receiving a visual signal of 1PPS radiated from a GPS satellite, and connected to the antenna to output 1PPS, and whether the 1PPS is received, a back-up voltage detection signal, and a year. GPS receiver for outputting data about the month and day, the main control unit connected to the output terminal of the GPS receiver to control the system by a predetermined program and to count and correct the main clock during 1PPS of the GPS receiver to synchronize and output each other, Precision time oscillation circuit connected between the input and output terminals of the main control unit to generate a constant 10MHz main clock, connected to the output terminal of the main control unit initializes the system and receives 1PPS from the GPS satellites, 1PPS and 10MHz output 1PPS and 10MH, which are synchronized with the reset and display unit which displays and generates an alarm when a system error occurs, and is connected to the output terminal of the main control unit. An output drive for outputting a frequency of z, and to communicate with other external devices, and a frequency synthesis unit connected to the 10MHz output terminal of the main control unit to output any frequency desired by the user in synchronization with 10MHz.

1A to 1C are schematic diagrams of a conventional time synchronizer.

2 is an overall block diagram of a time synchronizer according to the present invention.

3 is a detailed circuit diagram of a main control unit which is a time synchronization device according to the present invention;

4 is a detailed view of a precise time oscillation circuit as a time synchronization device according to the present invention;

5 is a detailed view of a reset and display unit which is a time synchronizer according to the present invention.

6 is a detailed view of an output drive circuit as a time synchronizer according to the present invention.

Figure 7 is a detailed view of the frequency synthesizing unit which is a visual synchronization device according to the present invention.

8 is an overall operation flow diagram of the time synchronizer according to the present invention.

9 is a timing diagram of each stage of the time synchronizer according to the present invention.

〈Description of the symbols for the main parts of the drawings〉

10: antenna 20: GPS receiver

30: reset and display unit 31: reset switch

32: reset circuit 33: drive circuit

34: display unit 40: precision time oscillation circuit

41: D / A converter 42: variable voltage oscillator (VCO)

50: main controller 51: microprocessor unit (MPU)

52, 53: 1st, 2nd ROM (ROM) 54, 55: 1st, 2nd RAM

56: chip selector 60: frequency synthesis unit

61: phase locked loop (PLL) 62: low frequency smoothing circuit

63: voltage controlled oscillator (VCO) 70: output drive

71, 72: first and second output unit 73: communication interface

100: GPS satellites

2 is a block diagram of a high-precision time synchronization device using a ground position measuring system according to the present invention, one side of the antenna 10 receiving the time signal emitted from the GPS satellite 100, one received time signal per second The GPS receiver 20 is connected to output a pulse of 1PPS, and to output whether or not the 1PPS is received, back-up voltage detection, and data on year, month, and day.

In addition, on the output side of the GPS receiver 20, the entire system is controlled by a predetermined program, and the outputs of the precision time oscillation circuit 40 and the GPS receiver 20 are combined and counted and corrected to precisely synchronize 10 MHz to 1 PPS. An output main controller 50 is connected.

In addition, one output terminal of the main controller 50 initializes the entire system and displays whether or not a time signal is received from the GPS and whether 1PPS is normally output by lighting a lamp, and resets to generate an alarm when a system abnormality occurs. And a display unit 30 are connected.

In addition, the other output terminal of the main control unit 50 outputs 1PPS and a frequency of 10MHz synchronized with each other and is provided with at least one communication port is connected to the output drive 70 that can communicate with other external devices, the main control unit One input terminal of 50 is connected with a precision time oscillation circuit 40 for constantly outputting a main clock of 10 MHz.

3 is a detailed circuit diagram of the main controller 50, which is a high-precision visual synchronization device using GPS according to the present invention, which controls the entire system and combines the outputs of the precision visual oscillation circuit 40 and the GPS receiver 20. A microprocessor unit (hereinafter referred to as MPU) 51 for correcting and accurately synchronizing and outputting 1PPS and 10MHz of the main clock is provided, and on one side of the MPU 51, the first and the first stores the entire control program of the system. 2 roms 52 and 53 are connected.

The other end of the MPU 51 is connected with first and second RAMs 54 and 55 for storing and reading data required during system operation, and the first and second ends of the MPU 51 are connected to one end of the MPU 51. The chip selectors 56 for enabling the two ROMs 52 and 53 and the first and second RAMs 54 and 55 are connected to each other.

4 is a detailed view of the precision time oscillation circuit 40 which is a time synchronization device according to the present invention, and a variable voltage oscillator 42 having a variable frequency output according to an applied voltage is connected to one input terminal of the MPU 51. Between the input terminal of the variable voltage oscillator 42 and the output terminal of the MPU 51, the correction data value transmitted from the MPU 51 is converted to analog so that the main clock output from the variable voltage oscillator 42 is 10 MHz. The D / A converter 41 applied to the voltage oscillator 42 is connected and comprised.

5 is a detailed circuit diagram of the reset and display unit 30, which is a high-precision time synchronization device using GPS according to the present invention, wherein an input terminal of one side of the MPU 51 initializes the entire system in accordance with the connection of the switch 31 ( 32) is connected, and the output terminal of the MPU 51 is composed of a plurality of LEDs and alarms through the drive circuit 33, whether or not to receive the visual signal from the GPS satellite 100, the normal output of 1PPS, alarm when a system error occurs The display part 34 which generate | occur | produces this is connected and comprised.

FIG. 6 is a detailed circuit diagram of an output drive circuit 70, which is a high-precision time synchronization device using GPS according to the present invention, wherein the first and second output units 71 output 1PPS and 10MHz to an output terminal of the MPU 51, respectively. 72 is connected and one or more communication interfaces 73 capable of various types of communication with the outside are connected.

Here, the first and second output units 71 and 72 are formed of first and second NOR gates NOR1 and NOR2, respectively, 1PPS at one end of the first NOR gate NOR1, and 10 MHz The NOR2 is applied to each of the two NOR gates, and an enable signal is applied from the MPU 51 to the other ends of the first and second NOR gates NOR1 and NOR2.

7 is a detailed circuit diagram of the frequency synthesizing unit 60, which is a high-precision time synchronizing device using GPS according to the present invention, wherein an output terminal of the MPU 51 converts a frequency of 10 MHz into a predetermined frequency and outputs the phase synchronizing loop 61. ) Is connected, and a low frequency smoothing circuit 62 for passing only a frequency of a predetermined band is connected to the output side of the phase synchronization loop 61.

In addition, a variable voltage oscillator 63 is connected to an output terminal of the low frequency smoothing circuit 62 to output a frequency proportional to the applied voltage, and a feedback circuit 64 is connected to an output terminal of the variable voltage oscillator 63. It is configured to be connected to the frequency input terminal of the phase synchronization loop (61).

8 is an overall operation flowchart of the high precision time synchronizer using GPS according to the present invention, and FIG. 9 is an input / output timing diagram of the high precision time synchronizer using GPS according to the present invention.

Looking at the operation of the present invention made as described above are as follows.

First, the overall operation of the present invention will be described with reference to FIG. 2, the 1PPS time signal of the GPS satellite 100 provides the time of the US Standard World Coordinated Time through two cesium atomic clocks and two rubidium atomic clocks mounted in the satellite itself. It is sent out as a standard.

Therefore, the time signal transmitted from the GPS satellite 100 is transmitted to the GPS receiver 20 through the antenna 10, thereby outputting 1PPS and receiving or not receiving the time signal transmitted from the GPS satellite 100. Each data relating to the detection and the year, month, and day is outputted to the main controller 50, while the main clock of 10 MHz is output from the precision time oscillator circuit 40 to be transmitted to the main controller 50.

On the other hand, the main controller 50 performs a series of programs according to the input state of the 1PPS transmitted from the GPS receiver 20 and the 10MHz main clock transmitted from the precision visual oscillation circuit 40 to sequentially control At the same time, by combining, counting, and calibrating, 1PPS and 10MHz are accurately synchronized, and then 1PPS and 10MHz are output.

Therefore, 10 MHz is accurately synchronized with 1 PPS at the main controller 50, and the frequency of each of the synchronized 1 PPS and 10 MHz is output through the output drive 70, while at the main controller 50, the signals of 1 PPS and 10 MHz are output. When is normally output is reset and sends a control signal to the display unit 30 to turn on the corresponding LED and at the same time, when receiving a visual signal from the GPS satellite 100, the corresponding LED light and an alarm when a system error occurs.

Therefore, when 1PPS and 10MHz, which are accurately synchronized by the main controller 50, are provided to the base station of the mobile communication of the code division multiple access (CDMA), time synchronization occurs for each base station, and the call is moved from the base station to another base station. The disconnection of the terminal during communication is eliminated.

The operation of the high-precision time synchronizer using GPS according to the present invention operated as outlined above will be described in more detail with reference to FIGS. 2 to 8 as follows.

First, when power is supplied to the system, the main controller 50 initializes the system in the MPU 51 (S1), and then executes a self-diagnosis mode (S2) to test whether there is an abnormality of the system.

At this time, if it is determined that there is no abnormality in the system (S3), the ready state for generating 1PPS using 10MHz, the main clock output from the precision time oscillation circuit 40 until the time signal 1PPS is received from the GPS satellite 100. On the other hand, when it is determined that there is an error in the system after executing the self-diagnosis mode, the control signal is sent to the drive circuit 33 of the reset and display unit 30 shown in FIG. 5 to the display unit 34. The system initial procedure (L1) for transmitting the built-in alarm is performed.

In this state, as described above, two cesium atomic clocks and two rubidium atomic clocks mounted in the GPS satellite 100 itself are transmitted based on the Universal Time Coordinated Universal Time (UTC). The antenna 10 is transmitted to the GPS receiver 20.

On the other hand, the GPS receiver 20 receives the time signal from the GPS satellite 100 and outputs 1PPS which generates one pulse per second as shown in FIG. 8A, and at the same time receives the time signal from the GPS satellite 100. Each data relating to whether or not, back-up voltage detection, and year, month, and day are transmitted to the main controller 50.

In addition, when power is supplied to the system, the MPU 51 sends a predetermined data value to the D / A converter 41 of the precision time oscillation circuit 40 shown in FIG. As a value is applied to the variable voltage oscillator 42, a main clock of 10 MHz is output, which is applied to the main controller 50 again.

Therefore, the main controller 50 determines whether a 1PPS visual signal is received from the GPS receiver 20 (S5). If it is determined that the 1PPS is normally received in the determination process, the main controller 50 recognizes the locked mode. By sending a control signal to the drive circuit 33 of the reset and display unit 30 of FIG. 5 to turn on (S6) the corresponding LED of the display unit 34 to inform that the normal state that the visual signal is received from the GPS satellite 100 do.

At this time, if it is determined that 1PPS is not received in the process of determining whether 1PPS is received from the GPS receiver 20 (S5), the MPU 51 clocks the previous data based on the holdover mode. GPS satellite signal receiving process (L2) to output the (S7) is performed.

On the other hand, if it is determined that the locked mode in which the 1PPS is received from the GPS receiver 20 in the GPS satellite signal reception process L2, the MPU 51 outputs the 10MHz main clock output from the precision time oscillation circuit 40 for 1PPS. If it is determined that the main clock is counted correctly 10 million times during 1PPS by counting (S8) as a built-in timer counter, it is recognized that 10MHz is correctly synchronized to 1PPS.

Accordingly, the display unit 34 outputs 1PPS shown in FIG. 8A and 10MHz shown in FIG. 8B, and sends control signals to the drive circuit 33, which is the reset and display unit 30 of FIG. By lighting the corresponding LED of (S10), it indicates that 10MHz is correctly synchronized with 1PPS.

However, if the main clock is not counted correctly 10 million times during 1PPS when the counting step S9 is performed in the MPU 51, it may be determined that the main clock output from the precision time oscillation circuit 40 is not exactly 10 MHz during 1PPS. As shown in 4, data for increasing or decreasing the output frequency of the variable voltage oscillator 42 is outputted to the D / A converter 41 (S11).

Therefore, the D / A converter 41 converts and outputs the digital signal output from the MPU 51 to the voltage value of the analog signal, and the converted voltage value is applied to the variable voltage oscillator 42 so as to be applied to the input voltage. The proportional output frequency is increased or decreased, and the increased or decreased output frequency is supplied to the MPU 51 to return to the counting step S8 of FIG. 7 which counts the main clock output from the variable voltage oscillator 42 for 1 PPS. By executing the synchronization and output process L3, the main clock of the variable voltage oscillator 42 can be maintained at a constant 10 MHz at all times.

In the first and second ROMs 52 and 53 in FIG. 3, a program capable of executing the above-described process is stored, and the MPU 51 stores the first and second ROMs 52 and 53. The program stored in the program is read sequentially so that 10MHz can be accurately synchronized and calibrated at 1PPS.

In addition, the first and second RAMs 54 and 55 are for temporarily storing data necessary during the above-described series of processes, and the chip selector 56 is required during program execution under the control of the MPU 51. In order to sequentially read data, the first and second ROMs 52 and 53 and the first and second RAMs 54 and 55 may be selectively enabled.

Next, referring to FIG. 6, a process in which 1PPS and 10MHz accurately synchronized in the MPU 51 are output through the output drive 70 is as follows.

First, after synchronizing 10 MHz to 1 PPS, 1 PPS output from the MPU 51 is transmitted to one end of the first NOR gate NOR1 of the first output unit 71, and 10 MHz is the second output unit 72. Is applied to the second NOR gate NOR2.

At this time, the enable signal is output from the MPU 51 to the first and second NOR gates NOR1 and NOR2 so that the clocks of 1PPS and 10 MHz synchronized with each other are the first and second NOR1 NOR1 NOR2. ) Output is made only when is enabled, so that it is possible to maintain isochronism by reducing the time error between 1PPS and 10MHz output signals, and to communicate with other external devices through one or more communication interfaces 73. .

On the other hand, when an abnormality occurs in a state in which the system is in operation or when the system is initialized as necessary, the reset circuit 32 is operated by transmitting the reset signal 32 to the MPU 51 when the switch 31 of FIG. 5 is turned on. As described above, the MPU 51 recognizes the reset signal and executes the step S1 of initializing the system of FIG. 7 to execute the above-described process again.

Next, a process of outputting a changed frequency when a frequency change of the user is required by the frequency synthesizer 60 shown in FIG. 7 will be described.

First, when a frequency of 10 MHz output from the MPU 51 is applied to the phase synchronization loop 61, a frequency signal of a predetermined level is output in comparison with the reference voltage Ref1, and the output signal is a low frequency smoothing circuit 62. The voltage is maintained at a stable voltage level through the variable voltage oscillator 63.

Accordingly, the variable voltage oscillator 63 outputs a frequency proportional to the voltage applied from the low frequency smoothing circuit 62 (in the present invention, 19 MHz), and at the same time, outputs the output frequency through the feedback circuit 64 again. As it returns to the frequency input terminal of 61, the self-correction is performed so that the output frequency of the variable voltage oscillator 63 is synchronized with 10 MHz, which is the main clock output from the MPU 51.

Therefore, when a plurality of frequency synthesizing section 60 consisting of a phase locked loop 61, a low frequency smoothing circuit 62, a variable voltage oscillator 63, and a feedback circuit 64 is connected, a desired frequency synchronized with 10 MHz can be obtained. will be.

As described above, the present invention allows the 10MHz of the main clock output from the precision time oscillation circuit to be accurately synchronized with the 1PPS output from the GPS receiver by a program set in the MPU of the main controller, and of course, 1PPS from the GPS receiver. If is not received, the MPU keeps the main clock synchronized through the prediction value of the timeout according to environmental factors, so that the time can be synchronized accurately within a certain allowable range even when a fatal error of the GPS receiver occurs.

In addition, it is possible to obtain a different predetermined frequency by a frequency synthesizer including a phase synchronization loop and a variable voltage oscillator, so that when the present invention is applied to mobile communication and other communication, the time of each base station is precisely synchronized at the same time. It is possible to prevent the disconnection of the mobile terminal in the state, it is possible to provide a small size and low cost of the product according to a simple configuration.

Claims (2)

An antenna 10 for receiving a time signal of 1PPS radiated from the GPS satellites 100, A GPS receiver 20 connected to the antenna 10 and outputting 1PPS and outputting data regarding a reception signal, a back-up voltage detection signal, and a year, month, and day of the 1PPS; A main control unit 50 connected to an output terminal of the GPS receiver 20 for controlling the system by a predetermined program and counting and correcting the main clock during 1PPS of the GPS receiver 20 and synchronizing with each other and outputting the same; A precision time oscillation circuit 40 connected between the input and output terminals of the main controller 50 to constantly generate a main clock of 10 MHz, The reset and display unit 30 is connected to the output terminal of the main control unit 50 to initialize the system and displays whether 1PPS is received from the GPS satellite 100, 1PPS and 10MHz output, and generates an alarm when a system error occurs. , An output drive 70 connected to an output terminal of the main controller 50 to output synchronized 1PPS and a frequency of 10 MHz, and to communicate with other external devices; A high precision time synchronization device using a ground position measuring system (GPS) consisting of a frequency synthesizer (60) connected to the 10 MHz output terminal of the main controller (50) to synchronize any frequency desired by the user to 10 MHz. The frequency synthesizing unit 60 of claim 1, A phase synchronization loop 61 connected to an output terminal of the MPU 51 to convert a frequency of 10 MHz into a predetermined signal and output the predetermined signal; A low frequency smoothing circuit 62 for outputting the output signal of the phase synchronization loop 61 at a stable voltage by passing only a frequency of a predetermined band; A voltage oscillator 63 connected to an output terminal of the low frequency smoothing circuit 62 and outputting an oscillation frequency proportional to an applied voltage; High-precision time synchronization device using a ground position measuring system (GPS), characterized in that consisting of a feedback circuit (64) for returning the output frequency of the variable voltage oscillator (63) to the phase synchronization loop (61).