CN103901771A - System and method for extracting time information of Beidou satellite based on FPGA - Google Patents

Abstract

The invention discloses a system and method for extracting Beidou satellite time information based on FPGA, comprising the following steps: Step 1, the FPGA processing unit receives the satellite information output by the Beidou receiver; Step 2, extracts the time of the received satellite information, extracts Step 3, converting the extracted world standard time information into national standard time, the present invention realizes the purpose of extracting the Beidou satellite time information and then using the Beidou satellite for time service.

Description

A system and method for extracting Beidou satellite time information based on FPGA

technical field

The invention relates to a method and device for extracting satellite information, in particular to a system and method for extracting Beidou satellite time information based on FPGA.

Background technique

China's BeiDou Navigation Satellite System (BDS) is a global satellite positioning and communication system independently developed by my country. satellite navigation system. The system consists of a space terminal, a ground terminal and a user terminal. It can provide all kinds of users with high-precision, high-reliability positioning, navigation, and timing services all-weather and all-weather around the world, and has the ability to communicate with short messages. Regional navigation, positioning and timing capabilities, the positioning accuracy is better than 20m, and the timing accuracy is better than 100ns.

At present, in terms of economy and stability, GPS satellite timing is generally used to obtain the world standard time, and the current displayed time is adjusted through the world standard time to achieve synchronization with the world standard time. But the time service that the GPS satellite timing device utilizes the GPS satellite system to carry out is real-time time service, and the power consumption is relatively large, and the GPS satellite system is a satellite system owned by foreign countries, and its safety and reliability are relatively poor. Therefore, it is necessary to propose a technical means, By extracting the time information of Beidou satellites, it is possible to use Beidou satellites for timing.

Contents of the invention

In order to overcome the deficiencies in the above-mentioned prior art, one object of the present invention is to provide a system and method for extracting Beidou satellite time information based on FPGA, which receives the satellite information output by the Beidou receiver through the FPGA serial port, and uses the received satellite information The time information is extracted through the time information extraction module, and finally the extracted time information is converted into standard time and then synchronized with other clock systems, realizing the extraction of Beidou satellite time information and then using the Beidou satellite for time service.

In order to achieve the above and other purposes, the present invention proposes a system for extracting Beidou satellite time information based on FPGA, at least including:

The Beidou receiver receives the navigation message transmitted by the Beidou satellite, and decodes the received navigation message to obtain satellite information;

The FPGA processing unit receives the satellite information output by the Beidou receiver, extracts the time of the obtained satellite information and converts it into the national standard time.

Further, the FPGA processing unit includes:

Dual-port RAM for real-time data buffering of received satellite information;

The time extraction module extracts the time of the satellite information according to the preset data format, and extracts the universal time;

The time conversion module converts the extracted world standard time to national standard time.

Further, the FPGA processing unit uses the UART port to receive the satellite information output by the Beidou receiver.

Further, the baud rate of the serial port of the FPGA processing unit for receiving satellite information is consistent with the baud rate of the serial port of the Beidou receiver for outputting satellite information.

Further, the satellite information includes time information, position coordinates, speed, elevation angle, azimuth angle, and signal-to-noise ratio.

Further, the FPGA processing unit is composed of logic gates and flip-flops, and the command execution mode is parallel execution.

In order to achieve the above object, the present invention also provides a method for extracting Beidou satellite time information based on FPGA, comprising the steps of:

Step 1, the FPGA processing unit receives the satellite information output by the Beidou receiver;

Step 2, time extraction is performed on the received satellite information to extract the universal time;

Step 3, converting the extracted world standard time information into national standard time.

Further, the FPGA processing unit receives satellite information of the Beidou receiver through the UART port, and the baud rate of the serial port of the FPGA receiving satellite information is consistent with the baud rate of the serial port of the Beidou receiver outputting satellite information.

Further, the satellite information includes time information, position coordinates, speed, elevation angle, azimuth angle, and signal-to-noise ratio.

Further, in step 2, the extracted time information includes year, month, day, hour, minute, and second, and is accurate to three decimal places of the second.

Compared with the prior art, a system and method for extracting Beidou satellite time information based on FPGA of the present invention receives satellite information output by Beidou receiver through the FPGA serial port, and extracts the time information through the time information extraction module of the received satellite information Finally, the extracted time information is converted into standard time and then synchronized with other clock systems, realizing the purpose of extracting time information from Beidou satellites and then using Beidou satellites for time service

Description of drawings

Fig. 1 is a system architecture diagram of a system for extracting Beidou satellite time information based on FPGA of the present invention;

Fig. 2 is a kind of step flowchart of the method for extracting Beidou satellite time information based on FPGA of the present invention;

FIG. 3 is a flow chart of time information extraction in a preferred embodiment of the present invention.

Detailed ways

The implementation of the present invention is described below through specific examples and in conjunction with the accompanying drawings, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and various modifications and changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

FIG. 1 is a system architecture diagram of a system for extracting Beidou satellite time information based on FPGA in the present invention. As shown in FIG. 1 , a system for extracting Beidou satellite time information based on FPGA in the present invention includes at least: Beidou receiver 101 and FPGA processing unit 102 .

Among them, the Beidou receiver 101 receives the navigation message transmitted by the Beidou satellite, and decodes the received navigation message to obtain satellite information. According to the working principle of the Beidou second-generation satellite navigation system, the Beidou receiver 101 needs to receive 4 Beidou satellites to perform Three-dimensional positioning, receiving three satellites for two-dimensional positioning. After the Beidou receiver 101 position is determined and does not change, the receiver only needs to receive one of the Beidou satellites 103 or 104 to perform accurate time transfer. Satellite information can be obtained after decoding the navigation message, which includes time information, position coordinates, speed, elevation angle, azimuth angle, signal-to-noise ratio, etc. It should be noted that the received Beidou satellite information follows the UNICORE+NMEA protocol The FPGA processing unit 102 receives the satellite information output by the Beidou receiver 101 through serial port communication, extracts the obtained satellite information and converts it to the national standard time after time, it should be noted that the FPGA processing unit 102 receives the satellite information through the serial port The baud rate of the Beidou receiver 101 should be consistent with the baud rate of the serial port that outputs the satellite information. Only in this way can the satellite information be received. In a preferred embodiment of the present invention, the FPGA processing unit 102 is based on logic gates and flip-flops. Parallel execution structure, therefore has fast data processing speed, and it comprises dual-port RAM105, time extraction module 106 and time conversion module 107, and dual-port RAM105 is used for carrying out the cache memory of real-time data, is about to deposit the satellite information that FPGA processing unit 102 receives In the dual-port RAM 105, when the dual-port RAM 105 is full of data, the notification time extraction module 106 extracts time information according to the UNICORE protocol. The UNICORE protocol specifies message formats for different applications, such as BDRMC, BDGGA, BDGSV, and BDVTG and so on, and what each message format contains is different. The time information extraction program designed by the present invention distinguishes and only extracts satellite information in one message format, such as extracting time information in the BDRMC message format. Specifically, the time extraction module 106 continuously detects the received satellite information, and when it detects that the message format is "$BDRMC", the information is sent to the time information extraction program to extract the time information, "$ In "BDRMC", the time information that needs to be extracted is immediately after the head frame $BDRMC, followed by the effective identification of the position, and the latitude and other information; based on the $BDRMC message format, the time information extraction program only needs to extract the 10 digits after the head frame $BDRMC One byte of information, that is, UTC time (hhmmss, sss), can be extracted to complete the extraction of UTC time. The time extraction module 106 selects the appropriate data format according to the user's needs to achieve the best results, and the time extracted by the time extraction module cannot be used immediately in the clock system (as shown in the figure A clock system 108 or B clock system 109) Synchronization, because the extracted time is Universal Time Coordinated (UTC), also known as Universal Standard Time, it is the basis for broadcasting the time numbers of various countries in the world at present. Convert, UTC time is converted into national standard time, for example, in China, then time conversion module 107 converts it to Beijing time, Beijing time and UTC time differ eight hours, and the time after conversion can be used for synchronizing other each clock system, the synchronized A clock system and B clock system will have a unified clock, which makes the comparison of the time of each clock system meaningful.

Fig. 2 is a flow chart of steps of a method for extracting Beidou satellite time information based on FPGA in the present invention. As shown in Figure 2, a kind of method of extracting Beidou satellite time information based on FPGA of the present invention comprises the following steps:

Step 201, the FPGA processing unit receives the satellite information output by the Beidou receiver, where the satellite information includes time information, position coordinates, speed, elevation angle, azimuth angle, signal-to-noise ratio and other information. In a preferred embodiment of the present invention, the FPGA processing unit receives the satellite information of the Beidou receiver through the UART port (serial interface), and the baud rate of the serial port of the FPGA receiving satellite information must be the same as the baud rate of the serial port of the Beidou receiver outputting satellite information. Only in this way can the satellite information be received. The Beidou receiver receives the satellite information transmitted by the Beidou second-generation satellite navigation system.

Step 202, time extraction is performed on the received satellite information. It should be noted that the time information extracted here is Universal Time Coordinated (UTC), also known as Universal Time, which is the basis for broadcasting time numbers of various countries in the world. . Here, the extracted time information includes year, month, day, hour, minute, and second, and is accurate to three decimal places of the second. In the present invention, the time information extracting program discriminatively only extracts satellite information in one message format, such as extracting time information in the BDRMC message format. Specifically, the FPGA processing unit continuously detects the received satellite information. When it detects that the message format is "$BDRMC", it sends the information to the time information extraction program to extract the time information. "$BDRMC" Among them, the time information that needs to be extracted is immediately after the head frame $BDRMC, followed by the effective location identification, and the latitude and other information. Therefore, based on the $BDRMC message format, the time information extraction program only needs to extract the 10 digits after the head frame $BDRMC One byte of information, that is, UTC time (hhmmss, sss), can be extracted to complete the extraction of UTC time.

Step 203, convert the extracted time information into the national standard time. In a preferred embodiment of the present invention, the national standard time is Beijing time, and the difference between Beijing time and UTC time is eight hours.

FIG. 3 is a flow chart of time information extraction in a preferred embodiment of the present invention. First, the FPGA processing unit needs to receive the satellite information output by the Beidou receiver. According to the principle of serial port communication, the two serial ports can only communicate with each other when the baud rate is the same. The baud rate of the serial port of the machine is the same. When the satellite information is received, it is necessary to continuously detect whether there is data transmission in the serial port (step 301). When the falling edge of the data signal is detected, it means that there is data sent. The device generates a clock to receive data (step 302), if the falling edge of the data signal is not detected, it does not start, and continues to detect. Further, when the receiving baud rate generator is started, it will continue to receive the Beidou satellite information (step 303), and store the received satellite information into the dual-port RAM105, and the time extraction module will start from another dual-port RAM. The port performs time extraction, and judges the extracted information according to the preset extraction time format (such as BDRMC) before extraction, and judges whether the received time information format conforms to (step 304), that is, whether the header frame of the received satellite information is BDRMC, If it matches, extract the time information (step 305), if not, filter the information, because the extracted time information is UTC time, which needs to be converted to Beijing time before clock synchronization (step 306), according to the distribution of time zones in the world, China is in East Eighth District, so the time difference between Beijing time and UTC is eight hours, so you only need to add eight hours to UTC to get Beijing time. According to the above method for extracting time information, time information that can be used for synchronization of various clock systems can be extracted quickly and accurately.

It can be seen that a system and method for extracting Beidou satellite time information based on FPGA of the present invention utilizes the characteristics of FPGA fast data processing, and uses it as a data acquisition and processing unit for receiving and processing Beidou satellite information, and FPGA receives the Beidou receiver through the UART port. Satellite information, in order to achieve real-time and fast data reception and extraction, a dual-port RAM is designed in the FPGA to cache satellite information. When the FPGA receives satellite information in real time, the time information is extracted by the time extraction module. The extracted time The information is further converted into Beijing time to be used to synchronize other clock systems, realizing a unified "clock alignment" between the systems.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Any person skilled in the art can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be listed in the claims.

Claims (10)

1. A system for extracting Beidou satellite time information based on FPGA, at least comprising: The Beidou receiver receives the navigation message transmitted by the Beidou satellite, and decodes the received navigation message to obtain satellite information; The FPGA processing unit receives the satellite information output by the Beidou receiver, extracts the time of the obtained satellite information and converts it into the national standard time. 2. a kind of system that extracts Beidou satellite time information based on FPGA as claimed in claim 1, is characterized in that, this FPGA processing unit comprises: Dual-port RAM for real-time data buffering of received satellite information; The time extraction module extracts the time of the satellite information according to the data format preset by the user, and extracts the world standard time; The time conversion module converts the extracted world standard time to national standard time. 3. a kind of system that extracts Beidou satellite time information based on FPGA as claimed in claim 2 is characterized in that: this FPGA processing unit utilizes UART mouth to receive the satellite information that this Beidou receiver outputs. 4. a kind of system that extracts Beidou satellite time information based on FPGA as claimed in claim 3 is characterized in that: the baud rate of the serial port of the serial port that the FPGA processing unit receives the satellite information and the baud rate of the serial port of the output satellite information of the Beidou receiver rate is the same. 5. A kind of system that extracts Beidou satellite time information based on FPGA as claimed in claim 2 is characterized in that: the satellite information includes time information, position coordinates, speed, elevation angle, azimuth angle, signal-to-noise ratio. 6. A kind of system that extracts Beidou satellite time information based on FPGA as claimed in claim 2, is characterized in that: this FPGA processing unit is made up of logic gate and flip-flop, and order execution mode is parallel execution. 7. A method for extracting Beidou satellite time information based on FPGA, comprising the steps of: Step 1, the FPGA processing unit receives the satellite information output by the Beidou receiver; Step 2, time extraction is performed on the received satellite information to extract the universal time; Step 3, converting the extracted world standard time information into national standard time. 8. a kind of method extracting Beidou satellite time information based on FPGA as claimed in claim 7, is characterized in that: this FPGA processing unit receives the satellite information of this Beidou receiver by UART mouth, and this FPGA receives the wave of the serial port of satellite information The baud rate is consistent with the baud rate of the serial port that the Beidou receiver outputs satellite information. 9. A kind of method extracting Beidou satellite time information based on FPGA as claimed in claim 7, is characterized in that: this satellite information comprises time information, position coordinates, velocity, elevation angle, azimuth angle, signal-to-noise ratio. 10. A kind of method extracting Beidou satellite time information based on FPGA as claimed in claim 7, is characterized in that: in step 2, the time information extracted comprises year, month, day, hour, minute, second, and is accurate to Three decimal places of seconds.

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