Second-generation distress beacon generation device and method of global satellite search and rescue system

Abstract

The invention relates to a second-generation distress beacon generation device and method of a global satellite search and rescue system, belongs to the technical field of circuits and signal processing, and solves the problem of how to apply search and rescue signals of second-generation distress beacons to the global satellite search and rescue system. According to the device, a digital information coding module generates digital messages conforming to second-generation distress beacons of a global satellite search and rescue system and divides the digital messages into IQ digital messages according to parity; the spreading code generation module generates an odd-path spreading code and a even-path spreading code which meet standard requirements of a second-generation distress beacon of a global satellite search and rescue system; the baseband data generation module generates baseband IQ two-path data based on the IQ two-path digital messages and the IQ two-path spreading codes; and the software radio transmitting module controls the software radio hardware platform, so that the software radio hardware platform generates a search and rescue signal meeting the standard requirement of the second-generation distress beacon of the global satellite search and rescue system based on the baseband IQ two-path data. Search and rescue signals suitable for a global satellite search and rescue system can be generated.

Description

Technical Field

[0001] The present invention relates to the technical field of circuits and signal processing, and in particular to a second-generation distress beacon generating device and method for a global satellite search and rescue system. Background Art

[0002] The Global Satellite Search and Rescue System is an information service system designed to conduct global search and rescue using satellites. The system uses low-altitude satellites to provide distress alarm and positioning services at sea, on land and in the air around the world, including in the polar regions, so that people in distress can receive timely and effective assistance. In the search and rescue activities over the past 20 years, the system has helped more than 17,000 people in distress to escape safely.

[0003] The global satellite search and rescue system consists of three parts: satellite space segment, distress beacon and ground processing subsystem. The function of the ground processing subsystem is mainly to process downlink signals, locate and correct the orbit parameters of its tracking satellite in real time. The main task of the satellite space segment is to receive search and rescue signals transmitted by ground user beacons. The distress beacon is equivalent to an independent small dedicated transmitter, which can manually or automatically transmit search and rescue signals when the carrier is in danger.

[0004] At present, the global satellite search and rescue system has gone through two iterations of the design of the distress beacon search and rescue signal form: the first generation beacon and the second generation beacon. The first generation beacon has the following basic characteristics:

[0005] 1. Use BPSK modulation;

[0006] 2. The format of the modulated message can be divided into short message format and long message format according to the actual needs of the user. The number of information bits in the short message format is 112 bits, and the number of bits in the long message format is 144 bits; the transmission rate is 400bps. The transmitted signal is a burst signal, and the duration of each short message burst is 440±1ms, and the duration of each long message burst is 520±1ms;

[0007] 3. Longitude and latitude are expressed in degrees, minutes and seconds. Depending on the different coding protocols used, the resolution of the longitude and latitude data encoded in the beacon is divided into 4' and 4".

[0008] Compared with the first-generation beacons, the second-generation beacons have the following basic characteristics:

[0009] 1. Use DSSS-OQPSK modulation;

[0010] 2. The information bit number of the modulated message is 300 bits, and the transmission rate is 300bps. The transmitted signal is a burst signal, and the duration of each burst is 1000±1ms;

[0011] 3. The latitude and longitude are expressed as integer and decimal parts of the degree. The decimal part is represented by 15-bit binary data with a resolution of 0.00003°.

[0012] It can be seen that compared with the first-generation beacons, the search and rescue signal data bits of the second-generation beacons are more, the resolution is higher, and the application range is wider. At present, the application of the first-generation beacons in the international arena is very mature, and it has become an essential rescue equipment for ships and aircraft. At present, the distress beacons in actual application are mainly based on the first-generation distress beacon standards stipulated by the global satellite search and rescue system. The research and application of the second-generation distress beacons of the global satellite search and rescue system are being actively promoted. Therefore, how to apply the search and rescue signals of the second-generation distress beacons to the global satellite search and rescue system is a technical problem that needs to be solved urgently. Summary of the invention

[0013] In view of the above analysis, an embodiment of the present invention aims to provide a second-generation distress beacon generating device for a global satellite search and rescue system, so as to solve the problem of how to apply the search and rescue signal of the second-generation distress beacon to the global satellite search and rescue system.

[0014] On the one hand, an embodiment of the present invention provides a second-generation distress beacon generating device for a global satellite search and rescue system, including: a digital information encoding module, used to generate the encoding of the second-generation distress beacon digital message of the global satellite search and rescue system and divide it into IQ two-way digital messages according to parity; a spread spectrum code generating module, used to generate an odd and even two-way spread spectrum code that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system; a baseband data generating module, used to generate baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code; and a software radio transmitting module, used to control a software radio hardware platform so that the software radio hardware platform generates a search and rescue signal that meets the standard requirements of the distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data.

[0015] The beneficial effects of the above technical solution are as follows: the baseband IQ two-way data is generated based on the IQ two-way digital message and the IQ two-way spread spectrum code through the baseband data generation module, and the baseband IQ two-way data is the baseband data that meets the requirements of the second-generation distress beacon standard and the requirements of the subsequent software radio transmission module. The software radio transmission module uses software radio technology to transmit and realize the search and rescue signal that meets the requirements of the 406MHz second-generation distress beacon standard file of the global satellite search and rescue system. Generating baseband data that meets the requirements of the second-generation distress beacon based on the requirements of the second-generation beacon standard file has important theoretical and practical significance for generating search and rescue signals that meet the requirements of the second-generation distress beacon standard of the global satellite search and rescue system and for my country's Beidou international search and rescue system to carry out search and rescue services based on the second-generation distress beacon.

[0016] Based on further improvements of the above-mentioned device, the baseband data generation module includes an I-channel data expansion module, a first XOR operation module, a first mapping module and a first signal shaping filter, wherein the I-channel data expansion module is used to expand each digital message in the 150-bit I-channel digital message in the distress beacon digital message into 256 bits to generate an extended I-channel digital information; the first XOR operation module is used to perform an XOR operation on the extended I-channel digital information and the I-channel spread spectrum code; the first mapping module is used to map the code element obtained after the XOR operation into a signal level, wherein code element 0 is mapped to a signal level 1, and code element 1 is mapped to a signal level -1; and the first signal shaping filter is used to perform waveform shaping on the mapped signal level.

[0017] Based on further improvements of the above-mentioned device, the baseband data generation module includes a Q-path data expansion module, a second XOR operation module, a delay module, a second mapping module and a second signal shaping filter, wherein the Q-path data expansion module is used to expand each digital message in the 150-bit Q-path digital message in the distress beacon digital message into 256 bits to generate expanded Q-path digital information; the second XOR operation module is used to perform an XOR operation on the expanded Q-path digital information and the Q-path spread spectrum code to generate a Q-path code element; the second mapping module is used to map the Q-path code element into a Q-path signal level, wherein the Q-path code element 0 is mapped into a signal level 1, and the Q-path code element 1 is mapped into a signal level -1; the delay module is used to delay the Q-path signal level by 1 / 2 code chip; and the second signal shaping filter is used to perform waveform shaping on the delayed Q-path signal level.

[0018] Based on further improvements of the above-mentioned device, the first signal shaping filter and the second signal shaping filter both include: an upsampling submodule, a parameter setting submodule and a filtering submodule, wherein the upsampling submodule is used to upsample the I-path signal level or the Q-path signal level after waveform shaping; the parameter setting submodule is used to select a root raised cosine filter and set a suitable roll-off coefficient for the root raised cosine filter; and the filtering submodule is used to filter the upsampled I-path signal level or the Q-path signal level using the root raised cosine filter with the suitable roll-off coefficient to normalize the amplitude of the I-path signal level or the Q-path signal level to between 0 and 1 and limit the baseband data spectrum.

[0019] Based on the further improvement of the above-mentioned device, the distress beacon digital message includes a preamble code, a main data segment, a rotating data segment and a BCH error correction code, wherein the digital information encoding module includes a preamble code generation module, a main data segment generation module, a rotating data segment generation module and a BCH error correction code generation module, wherein the preamble code generation module is used to set the preamble code to 0; the main data segment generation module is used to set the value of the main data segment, wherein the main data segment includes the beacon's serial number, type, country code, location data and idle bits; the rotating data segment generation module is used to set the value of the rotating data segment, wherein the rotating data segment includes a flag bit and a beacon activation mode; and the BCH error correction code generation module is used to calculate the error correction code based on the main data segment and the rotating data segment.

[0020] Based on further improvements of the above-mentioned device, the serial number of the beacon is encoded as 14 bits in the main data segment; the type of the beacon is encoded as 3 bits in the main data segment; the country code of the beacon is encoded as 10 bits in the main data segment, and the country code of the beacon is based on the International Telecommunication Union Maritime Identification Digital Country Code; the position data is encoded as 47 bits in the main data segment, and the position data includes a latitude flag, an integer part of the latitude data, a decimal part of the dimension data, a longitude flag, an integer part of the longitude data and a decimal part of the precision data; and the idle bit is encoded as the 14th bit in the main data segment and is set to 1.

[0021] Based on the further improvement of the above device, the BCH error correction code generation module includes: an expansion submodule, which is used to add 0 before and after the digital message generated by the front main data segment generation module and the rotation data segment generation module to generate an expanded 255-bit data; a data extraction submodule, which is used to find the position of the first non-zero element from the expanded 255-bit data, mark the position of the first non-zero element and extract 48 bits to form 49-bit data; an XOR submodule, which is used to XOR the 49-bit data with the given 49-bit data generating polynomial coefficient, wherein the given 49-bit data is the same in each cycle; a repeated data extraction submodule, which is used to find the position of the first non-zero element in the obtained value, eliminate all the leading zero elements, and add the corresponding digital message thereafter to re-form the 49-bit digital message; and a loop submodule, which is used to repeat the XOR operation and re-extract data processing until the 255-bit digital message is extracted, and the last 48 bits of the 49-bit data obtained for the last time are taken as the final BCH error correction code.

[0022] Based on the further improvement of the above device, the spread spectrum code generation module includes: an initial value generation module, which is used to set different initial values ​​of 23 linear feedback shift registers according to different IQ branches, wherein the 23 linear feedback shift registers are numbered 0-22; an output module, which is used to output the value of the 0th linear feedback shift register; an operation module, which is used to perform an XOR operation on the value of the 0th linear feedback shift register and the value of the 18th linear feedback shift register, and use the XOR operation result as the value of the 22nd linear feedback shift register at the next moment; a right shift module, which is used to right shift the value of the 22nd to 1st linear feedback shift register at the previous moment as the value of the 21st to 0th linear feedback shift register at the next moment; a chip generation module, which is used to take the 0th register value as the output, repeat the XOR operation and right shift processing until 2 is generated. 23 -1 chip; and a spreading code generation module for generating 2 23 -1 code chip is truncated into 38400, which are used as the spreading codes for I and Q channel outputs respectively.

[0023] Based on further improvements of the above-mentioned device, the software radio transmission module includes a zero intermediate frequency architecture orthogonal up-conversion framework, a parameter setting module and a search and rescue signal transmission module, wherein the zero intermediate frequency architecture orthogonal up-conversion framework is used to initialize the software radio hardware platform based on the zero intermediate frequency architecture; the parameter setting module is used to control key parameters using software radio technology, wherein the key parameters include the clock frequency, RF channel and center frequency and gain of the transmitted signal of the software radio hardware platform; and the search and rescue signal transmission module is used to call the data transmission interface to transmit the generated baseband data.

[0024] On the other hand, an embodiment of the present invention provides a method for generating a second-generation distress beacon of a global satellite search and rescue system, including: generating a code for a distress beacon digital message of the global satellite search and rescue system and dividing it into IQ two-way digital messages according to parity; generating an odd and even two-way spread spectrum code that meets the standard requirements of the distress beacon of the global satellite search and rescue system; generating baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code; and controlling a software radio hardware platform so that the software radio hardware platform generates a search and rescue signal that meets the standard requirements of the distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] 1. The baseband data generation module generates baseband IQ two-way data based on IQ two-way digital messages and IQ two-way spread spectrum codes. The baseband IQ two-way data meets the requirements of the second-generation distress beacon standard and the requirements of the subsequent software radio transmission module. The software radio transmission module uses software radio technology to transmit and realize the search and rescue signal that meets the requirements of the global satellite search and rescue system 406MHz second-generation distress beacon standard file;

[0027] 2. Generating baseband data that complies with the second-generation distress beacon based on the requirements of the second-generation beacon standard document has important theoretical and practical significance for generating search and rescue signals that comply with the second-generation distress beacon standard requirements of the global satellite search and rescue system and for my country's Beidou international search and rescue system to carry out search and rescue services based on the second-generation distress beacon.

[0028] 3. Meet the requirements of the second-generation distress beacon standards of the global satellite search and rescue system, and provide support for beacon generation and optimized design for the search and rescue business of my country's Beidou international search and rescue system based on the second-generation distress beacon;

[0029] 4. Make full use of the advantages of software radio technology. The software radio-based method is based on a universal, standard, modular hardware platform. It realizes various functions required through baseband data software programming and can effectively control information. Computer control and digital baseband technology are used to achieve flexible and precise control of the working parameters of the radio frequency signal. The modulated data message meets the full set of protocols of the 406MHz second-generation distress beacon of the global satellite search and rescue system. Various working parameters of the search and rescue beacon signal can be flexibly controlled. It has good flexibility.

[0030] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0032] Figure 1 is a block diagram of a second-generation distress beacon generating device for a global satellite search and rescue system according to an embodiment of the present invention;

[0033] Figure 2 2 is an overall module structure diagram of a second-generation distress beacon generating device for a global satellite search and rescue system according to an embodiment of the present invention;

[0034] Figure 3 A flowchart of generating an IQ two-way digital message by a digital message encoding module according to an embodiment of the present invention;

[0035] Figure 4 is a flow chart of calculating a 48-bit BCH error correction code in a digital message according to an embodiment of the present invention;

[0036] Figure 5 A flow chart of the steps of generating a spread spectrum code according to an embodiment of the present invention;

[0037] Figure 6 A time domain diagram of a second-generation distress beacon search and rescue signal generated according to an embodiment of the present invention;

[0038] Figure 7 A spectrum diagram of a second-generation distress beacon search and rescue signal generated according to an embodiment of the present invention;

[0039] Figure 8 The present invention is a flowchart of a method for generating a second-generation distress beacon of a global satellite search and rescue system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0041] refer to Figure 1 A specific embodiment of the present invention discloses a second-generation distress beacon generating device for a global satellite search and rescue system, including: a digital information encoding module 101, a spread spectrum code generating module 102, a baseband data generating module 103 and a software radio transmitting module 104.

[0042] The digital information encoding module 101 is used to generate the encoding of the second-generation distress beacon digital message of the global satellite search and rescue system and divide it into two digital messages, IQ, according to the odd and even numbers. Specifically, the distress beacon digital message includes a preamble, a main data segment, a rotated data segment and a BCH error correction code, wherein the digital information encoding module includes a preamble generation module, a main data segment generation module, a rotated data segment generation module and a BCH error correction code generation module. The preamble generation module is used to set the preamble to 0. The main data segment generation module is used to set the value of the main data segment, wherein the main data segment includes the serial number, type, country code, location data and idle bits of the beacon. Specifically, the serial number of the beacon is encoded as 14 bits in the main data segment, for example, encoded in bits 17 to 30 or other 14 bits of the main data segment; the type of the beacon is encoded as 3 bits in the main data segment, for example, encoded in bits 138 to 140 or other 3 bits of the main data segment; the country code of the beacon is encoded as 10 bits in the main data segment, for example, encoded in bits 31 to 40 or other 10 bits of the main data segment, and the country code of the beacon is based on the International Telecommunication Union Maritime Identification Digital Country Code; the position data is encoded as 47 bits in the main data segment, for example, encoded in bits 44 to 90 or other 47 bits of the main data segment, and the position data includes a latitude flag, an integer part of the latitude data, a decimal part of the dimension data, a longitude flag, an integer part of the longitude data, and a decimal part of the precision data; and the idle bit is encoded as the 14th bit in the main data segment, for example, encoded in bits 144 to 154 or other 14 bits of the main data segment and set to 1. The rotation data segment generation module is used to set the value of the rotation data segment, wherein the rotation data segment includes a flag bit and a beacon activation mode. The BCH error correction code generation module is used to calculate the error correction code according to the main data segment and the rotation data segment.

[0043] The BCH error correction code generation module includes: an expansion submodule, which is used to add 0 before and after the digital message generated by the main data segment generation module and the rotation data segment generation module to generate an expanded 255-bit data; a data acquisition submodule, which is used to find the position of the first non-zero element from the expanded 255-bit data, mark the position of the first non-zero element and take 48 bits to form 49-bit data; an XOR submodule, which is used to XOR the 49-bit data with the given 49-bit data generating polynomial coefficient, wherein the given 49-bit data is the same in each cycle; a repeated data acquisition submodule, which is used to find the position of the first non-zero element in the obtained value, eliminate all the preceding zero elements, and add the corresponding digital message thereafter to re-form the 49-bit digital message; and a loop submodule, which is used to repeat the XOR operation and re-acquisition of data until the 255-bit digital message is completely acquired, and the last 48 bits of the 49-bit data obtained for the last time are taken as the final BCH error correction code.

[0044] The spread spectrum code generation module 102 is used to generate an odd-even two-way spread spectrum code that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system. Specifically, the spread spectrum code generation module includes: an initial value generation module is used to set different initial values ​​of 23 linear feedback shift registers according to different IQ branches, wherein the 23 linear feedback shift registers are numbered 0-22; an output module is used to take the value of the 0th linear feedback shift register as output; an operation module is used to perform an XOR operation on the value of the 0th linear feedback shift register and the value of the 18th linear feedback shift register, and use the XOR operation result as the value of the 22nd linear feedback shift register at the next moment; a right shift module is used to right shift the value of the 22nd to 1st linear feedback shift register at the previous moment as the value of the 21st to 0th linear feedback shift register at the next moment; a chip generation module is used to take the 0th register value as output, repeat the XOR operation and right shift processing until 223-1 chips are generated; and a spread spectrum code generation module is used to generate 2 23 -1 code chip is truncated into 38400, which are used as the spreading codes for I and Q outputs respectively.

[0045] The baseband data generation module 103 is used to generate baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code. The baseband data generation module 103 includes an I-way data expansion module, a first XOR operation module, a first mapping module and a first signal shaping filter. The I-way data expansion module is used to expand each digital message in the 150-bit I-way digital message in the distress beacon digital message into 256 bits to generate an expanded I-way digital information. The first XOR operation module is used to perform an XOR operation on the expanded I-way digital information and the I-way spread spectrum code. The first mapping module is used to map the code element obtained after the XOR operation into a signal level, wherein code element 0 is mapped to a signal level 1, and code element 1 is mapped to a signal level -1. The first signal shaping filter is used to perform waveform shaping on the mapped signal level. Specifically, the first signal shaping filter includes: an upsampling submodule, a parameter setting submodule and a filtering submodule. The upsampling submodule is used to upsample the I-way signal level or the Q-way signal level after waveform shaping. The parameter setting submodule is used to select a root raised cosine filter and set a suitable roll-off coefficient for the root raised cosine filter, that is, to set the basic parameters of the root raised cosine filter. The filtering submodule is used to filter the upsampled I-channel signal level or Q-channel signal level using a root raised cosine filter with a suitable roll-off coefficient, so as to normalize the amplitude of the I-channel signal level or the Q-channel signal level to between 0 and 1 and limit the baseband data spectrum.

[0046] The baseband data generation module 103 also includes a Q-path data expansion module, a second XOR operation module, a delay module, a second mapping module and a second signal shaping filter. The Q-path data expansion module is used to expand each digital message in the 150-bit Q-path digital message in the distress beacon digital message into 256 bits to generate expanded Q-path digital information. The second XOR operation module is used to perform an XOR operation on the expanded Q-path digital information and the Q-path spread spectrum code to generate a Q-path code element. The second mapping module is used to map the Q-path code element to the Q-path signal level, wherein the Q-path code element 0 is mapped to the signal level 1, and the Q-path code element 1 is mapped to the signal level -1. The delay module is used to delay the Q-path signal level by 1 / 2 code chip. The second signal shaping filter is used to perform waveform shaping on the delayed Q-path signal level. Specifically, the second signal shaping filter includes: an upsampling submodule, a parameter setting submodule and a filtering submodule. The upsampling submodule is used to upsample the I-path signal level or the Q-path signal level after waveform shaping. The parameter setting submodule is used to select a root raised cosine filter and set a suitable roll-off coefficient for the root raised cosine filter. The filtering submodule is used to filter the upsampled I-channel signal level or Q-channel signal level using a root raised cosine filter with a suitable roll-off coefficient to normalize the amplitude of the I-channel signal level or Q-channel signal level to between 0 and 1 and limit the baseband data spectrum.

[0047] The software radio transmitting module 104 is used to control the software radio hardware platform so that the software radio hardware platform generates a search and rescue signal that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data. The software radio transmitting module includes a zero intermediate frequency architecture orthogonal up-conversion framework, a parameter setting module and a search and rescue signal transmitting module, wherein the zero intermediate frequency architecture orthogonal up-conversion framework is used to initialize the software radio hardware platform based on the zero intermediate frequency architecture; the parameter setting module is used to control key parameters using software radio technology, wherein the key parameters include the clock frequency, radio frequency channel and the center frequency and gain of the transmitted signal of the software radio hardware platform; and the search and rescue signal transmitting module is used to call the data transmission interface to transmit the generated baseband data.

[0048] Compared with the prior art, the second-generation distress beacon generating device of the global satellite search and rescue system provided in this embodiment generates baseband IQ two-way data based on IQ two-way digital messages and IQ two-way spread spectrum codes through a baseband data generating module, and the baseband IQ two-way data is baseband data that meets the requirements of the second-generation distress beacon standard and the requirements of the subsequent software radio transmitting module. The software radio transmitting module uses software radio technology to transmit and realize the rescue signal that meets the requirements of the 406MHz second-generation distress beacon standard file of the global satellite search and rescue system.

[0049] refer to Figure 8Another specific embodiment of the present invention discloses a method for generating a second-generation distress beacon of a global satellite search and rescue system, comprising: in step S801, generating a code of a second-generation distress beacon digital message of the global satellite search and rescue system and dividing it into IQ two-way digital messages according to parity, specifically, the distress beacon digital message includes a preamble code, a main data segment, a rotated data segment and a BCH error correction code; in step S802, generating an even-odd two-way spread spectrum code that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system; in step S803, generating baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code; and in step S804, controlling a software radio hardware platform so that the software radio hardware platform generates a rescue signal that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data.

[0050] In view of the above-mentioned current global satellite search and rescue system 406MHz second-generation distress beacon standard specifications and the construction requirements of my country's Beidou international search and rescue system, it is necessary to provide a method and device that can effectively realize the global satellite search and rescue system 406MHz second-generation distress beacon. The method and device can generate search and rescue signals that meet the requirements of the global satellite search and rescue system 406MHz second-generation distress beacon standard, and provide a basis for my country's Beidou international search and rescue system to carry out search and rescue services based on second-generation distress beacons.

[0051] The method for generating a second-generation distress beacon of a global satellite search and rescue system according to an embodiment of the present invention mainly includes:

[0052] 1. Digital information coding module: According to the provisions of the global satellite search and rescue system 406MHz second-generation distress beacon standard document, a digital message that meets the standard is generated, with a total of 300 bits. This includes a 50-bit preamble, a 154-bit main data segment, a 48-bit rotation data segment, and a 48-bit BCH error correction code. The digital message is then divided into two paths, IQ, according to the odd and even numbers, with a total of 150 bits of data in each path.

[0053] 2. Spread spectrum code generation module: According to the provisions of the global satellite search and rescue system 406MHz second-generation distress beacon standard document, the generating polynomials of the linear feedback shift registers of the IQ two channels are the same, but the initial values ​​of the linear feedback shift registers of the IQ two channels are different, and different spread spectrum codes are generated accordingly. The spread spectrum code rate is 38400 chips / s.

[0054] 3. Baseband data generation module: According to the DSSS-OQPSK system of the rescue signal specified in the standard document of the second-generation distress beacon of the global satellite search and rescue system 406MHz, the corresponding baseband data is generated. Specifically, the 150-bit digital message of each of the IQ channels is XORed with the spread spectrum code, where 1 bit of the digital message corresponds to a spread spectrum code of 256 chips, and then the spread spectrum code of the Q channel is delayed by 1 / 2 chip, and then the baseband code element is mapped into the signal level, and a signal shaping filter (root-raised cosine filter) is used for waveform shaping, and finally the IQ baseband data is formed.

[0055] As the main part of the baseband, the baseband data generation module has the main function of generating the corresponding baseband IQ data based on the generated spread spectrum code and digital message. It mainly includes four steps: XOR operation of data message and spread spectrum code, delay of 1 / 2 chip for Q channel data, mapping of code element to signal level, and filtering using signal shaping filter. Through this module, baseband data that meets the requirements of the second-generation distress beacon standard and the requirements of the subsequent software radio transmission module is generated. The specific steps of this module are as follows:

[0056] (1) First, the data message obtained by the digital information encoding module and the spread spectrum code generation module is XORed with the spread spectrum code. The 150-bit message in each of the two IQ channels generated by the digital message encoding module is XORed with the spread spectrum code of 38,400 chips in each of the two IQ channels generated by the spread spectrum code generation module, where one digital message corresponds to a spread spectrum code of 256 chips. Specifically, if the digital message is 0, the corresponding 256-bit spread spectrum code remains unchanged; if the digital message is 1, the corresponding 256-bit spread spectrum code is flipped.

[0057] (2) The Q path is then delayed by 1 / 2 chip. Specifically, each code element is copied by a certain sampling multiple L (even multiple), and then L / 2 zeros are added before the Q path spread spectrum code and L / 2 zeros are added after the I path spread spectrum code. In this way, a 1 / 2 chip delay of the Q path code element is achieved to ensure that only one code element of the IQ path changes at any moment.

[0058] (3) After that, the code element is mapped to the signal level. According to the Global Satellite Search and Rescue System Second Generation Distress Beacon Standard, the code element "0" is mapped to the signal level "1"; the code element "1" is mapped to the signal level "-1".

[0059] Finally, the data obtained in the previous step is sent to the signal shaping filter for waveform shaping. First, the data generated in the previous step is upsampled, and then a root raised cosine filter is selected, and the appropriate roll-off coefficient and other parameters are set for this filter, and the upsampled data is sent to the root raised cosine filter. On the one hand, the amplitude of the output IQ two-way baseband data is normalized to between 0 and 1 to meet the requirements of the software radio hardware platform; on the other hand, the baseband data spectrum is reasonably restricted to meet the requirements of the second-generation distress beacon standard of the global satellite search and rescue system.

[0060] 4. Software radio transmission module: Utilizing software radio technology, based on software radio equipment that adopts zero intermediate frequency architecture and orthogonal up-conversion transmission framework, set the corresponding center frequency, clock frequency and other key parameters to transmit search and rescue signals that meet the requirements of the global satellite search and rescue system 406MHz second-generation distress beacon standard document.

[0061] The main function of the software radio transmission module is to control the software radio hardware platform through the program to generate the corresponding search and rescue signal that meets the requirements of the second-generation distress beacon standard of the global satellite search and rescue system. In this module, the software radio technology is used to control the clock frequency, RF channel, center frequency, gain and other key parameters of the hardware platform to flexibly implement the search and rescue signal that meets the requirements of the second-generation distress beacon standard of the global satellite search and rescue system 406MHz. The specific implementation steps of this module are as follows:

[0062] (1) First, initialize the software radio hardware platform based on the zero-IF architecture and set appropriate parameters such as clock frequency, gain, and center frequency.

[0063] (2) Then the data transmission interface is called to transmit the generated baseband data.

[0064] (3) After a burst ends, wait for the next transmission until it ends.

[0065] In the following, reference Figures 2 to 7 The second-generation distress beacon generating device or method of the global satellite search and rescue system according to an embodiment of the present invention is described in detail by way of specific examples.

[0066] like Figure 2 As shown, the second-generation distress beacon generating device of the global satellite search and rescue system according to an embodiment of the present invention includes a digital information encoding module, a spread spectrum code generating module, a baseband data generating module, and a software radio transmitting module.

[0067] The main function of the digital message encoding module is to realize the encoding of the digital information of the second generation distress beacon of the global satellite search and rescue system. In the 1s duration of each burst signal, the total digital message transmitted is 300 bits. The specific implementation steps of this module are as follows Figure 3 As shown:

[0068] First, the 50-bit leading code is set to 0 according to the requirements; secondly, the value of the 154-bit main data segment is set according to the protocol requirements and actual conditions. The message encoded in this main data segment includes the beacon's serial number, type, country code, location data and idle bits, etc.

[0069] According to the Global Satellite Search and Rescue System Second Generation Distress Beacon Standard, the beacon serial number is represented by a 14-bit binary code and is encoded in bits 17-30 of the main data segment;

[0070] The type of beacon is represented by a 3-bit binary number, which is encoded in bits 138-140 of the main data segment. For example, "000" indicates that the beacon type is ELT, "001" indicates that the beacon type is EPIPB, and "010" indicates that the beacon type is PLB, etc.

[0071] The country code is represented by a 10-bit binary number and is encoded in the 31st to 40th bits of the main data segment. The country code is based on the International Telecommunication Union (ITU) Maritime Identification Number (MID) country code, which can be found on the ITU website. For example, the country code for my country is 412, 413, 414, which can be converted into a 10-bit binary number.

[0072] The position data is represented by a 47-bit binary number and is encoded in bits 44-90 of the main data segment, where bit 44 is the latitude flag (0 indicates north latitude and 1 indicates south latitude); bits 45-51 are the integer part of the latitude data (0-90°), and bits 52-66 are the decimal part of the latitude data, represented by 15 bits of binary data with a resolution of 0.00003°; bit 67 is the longitude flag (0 indicates east longitude and 1 indicates west longitude); bits 68-75 are the integer part of the longitude data (0-180°), and bits 76-90 are the decimal part of the longitude data, also represented by 15 bits of binary data with a resolution of 0.00003°.

[0073] The spare bits are 14 bits of binary data, which are encoded in bits 141-154 of the main data segment. In general, these bits are set to 1. The above description shows that each bit of data in the digital message is generated according to the second-generation distress beacon standard, and the message represented by each bit of data and the corresponding position are in compliance with the second-generation distress beacon specification.

[0074] Then, the value of the 48-bit main data segment is set according to the protocol requirements and the actual situation. This rotated data segment includes the flag bit, beacon activation method, etc.; then the 48-bit BCH error correction code is calculated. This step calculates the 48-bit BCH error correction code based on the 202-bit digital message (154-bit main data segment and 48-bit rotated data segment) generated in the first two steps. The calculation process in this step is as follows Figure 4 As shown:

[0075] (1) First, expand the 202-bit digital message generated in the first two steps to 255 bits, that is, add 5 "0"s before the 202-bit data and add 48 "0"s after it for subsequent calculations;

[0076] (2) Find the position of the first non-zero element in the expanded data, mark it, and then take 48 bits to form 49 bits of data;

[0077] (3) XOR the above 49-bit data with the given 49-bit generator polynomial coefficient. The XOR operation is to XOR two 49-bit data, one of which represents the coefficient of the generator polynomial. According to the principle of BCH error correction code, the given generator polynomial coefficient is the same in each cycle.

[0078] (4) Find the position of the first non-zero element in the obtained value, remove all the leading zero elements, and add the corresponding digital message after it to re-form a 49-digit digital message;

[0079] (5) Repeat steps 3 and 4 until the 255-bit digital message is completely obtained, and take the last 48 bits of the last 49 bits of data (i.e., the 49 bits of data obtained after the XOR operation) as the final BCH error correction code.

[0080] Finally, the obtained 300-bit digital message is divided into two paths, IQ, according to parity, with each path containing 150 bits, in preparation for use in subsequent modules.

[0081] The main function of the spread spectrum code generation module is to generate spread spectrum codes that meet the requirements of the 406MHz second-generation distress beacon standard of the global satellite search and rescue system. In this module, 23 linear feedback shift registers (numbered 0-22) are used to generate spread spectrum codes. According to the requirements of the standard, the generating polynomial of the linear feedback shift register is always the same, but the initial values ​​of different data branches are different, so the generated spread spectrum codes are also different. The specific steps for generating spread spectrum codes in this module are as follows: Figure 5 As shown:

[0082] (1) According to different branches (I path, Q path), different initial values ​​of 23 linear feedback shift registers (numbered 0-22) are set;

[0083] (2) The value of register 0 is used as output;

[0084] (3) Perform an XOR operation on the value of the 0th register and the value of the 18th register, and use the resulting value as the value of the 22nd register at the next moment;

[0085] (4) Shift the values ​​of the 22nd to 1st registers at the previous moment rightward as the values ​​of the 21st to 0th registers at the next moment;

[0086] (5) Take the 0th register value as the output and repeat steps 3 and 4 until 223-1 chips are generated;

[0087] (6) The generated code chips are truncated into 38400 and used as the spreading codes for I and Q outputs respectively.

[0088] As the main part of the baseband, the baseband data generation module has the main function of generating the corresponding baseband IQ data based on the generated spread spectrum code and digital message. It mainly includes four steps: XOR operation of data message and spread spectrum code, delay of 1 / 2 chip for Q channel data, mapping of code element to signal level, and filtering using signal shaping filter. Through this module, baseband data that meets the requirements of the second-generation distress beacon standard and the requirements of the subsequent software radio transmission module is generated. The specific steps of this module are as follows:

[0089] 1. First, perform an XOR operation on the data message obtained by the digital information encoding module and the spread spectrum code generation module and the spread spectrum code. Perform an XOR operation on the 150-bit message of each of the two IQ channels generated by the digital message encoding module and the spread spectrum code of each of the two IQ channels generated by the spread spectrum code generation module, where one digital message corresponds to a spread spectrum code of 256 chips. Specifically, if the digital message is 0, the corresponding 256-bit spread spectrum code remains unchanged; if the digital message is 1, the corresponding 256-bit spread spectrum code is flipped.

[0090] 2. Then delay the Q path by 1 / 2 code chip. The specific method is to copy each code element by a certain sampling multiple L (even multiple), and then add L / 2 zeros before the Q path spread spectrum code and add L / 2 zeros after the I path spread spectrum code. In this way, a 1 / 2 code chip delay of the Q path code chip is achieved to ensure that only one code element of the IQ path changes at each moment.

[0091] 3. Then, the code element is mapped to the signal level. According to the second generation distress beacon standard of the global satellite search and rescue system, the code element "0" is mapped to the signal level "1"; the code element "1" is mapped to the signal level "-1".

[0092] 4. Finally, the data obtained in the previous step is sent to the signal shaping filter for waveform shaping. First, the data generated in the previous step is upsampled, and then a root raised cosine filter is selected. The appropriate roll-off coefficient and other parameters are set for this filter, and the upsampled data is sent to the root raised cosine filter. On the one hand, the amplitude of the output IQ two-way baseband data is normalized to between 0 and 1 to meet the requirements of the software radio hardware platform; on the other hand, the baseband data spectrum is reasonably restricted to meet the requirements of the second-generation distress beacon standard of the global satellite search and rescue system. At this point, the baseband data is ready, providing a basis for subsequent transmission using the software radio transmission module.

[0093] After the baseband data is prepared, it is sent to the software radio transmission module and transmitted using the software radio equipment. Specifically, the baseband data generated by the baseband data generation module already meets the requirements of the software radio transmission module for the data format. Subsequently, by initializing the software radio equipment and then calling the data transmission interface, the corresponding signal can be transmitted. Since the signal implemented is in accordance with the requirements of the second-generation distress beacon standard of the global satellite search and rescue system, only the implementation method is different, the receiving device can receive it according to the second-generation search and rescue signal standard, and no special requirements are required for the receiving device.

[0094] The main function of the software radio transmission module is to control the software radio hardware platform through the program to generate the corresponding search and rescue signal that meets the requirements of the second-generation distress beacon standard of the global satellite search and rescue system. In this module, the software radio technology is used to control the clock frequency, RF channel, center frequency, gain and other key parameters of the hardware platform to flexibly implement the search and rescue signal that meets the requirements of the second-generation distress beacon standard of the global satellite search and rescue system 406MHz. The specific implementation steps of this module are as follows:

[0095] 1. First, initialize the software radio hardware platform based on the zero-IF architecture and set appropriate parameters such as clock frequency, gain, center frequency, etc.

[0096] 2. Then call the data transmission interface to transmit the generated baseband data;

[0097] 3. After a burst ends, wait for the next launch until it ends.

[0098] Through the progressive and mutual combination of the above four modules, the final signal meets the requirements of the second-generation distress beacon standard of the global satellite search and rescue system. The time domain diagram and spectrum diagram of the measured signal are shown in the figure below. Figure 6 and Figure 7 shown.

[0099] Beneficial Effects

[0100] The implementation method of the 406MHz second-generation distress beacon of the global satellite search and rescue system based on the zero intermediate frequency architecture mentioned in the embodiment of the present invention is based on the protocol standard of the second-generation distress beacon made by the global satellite search and rescue system, and proposes to use software radio technology to implement the search and rescue signal that meets the requirements of the second-generation distress beacon. Its advantages are as follows:

[0101] First: meet the requirements of the second-generation distress beacon standards of the global satellite search and rescue system, and provide support for beacon generation and optimized design for the search and rescue services of my country's Beidou international search and rescue system based on the second-generation distress beacons.

[0102] Second: Make full use of the advantages of software radio technology. The software radio-based method is based on a universal, standard, modular hardware platform, and can effectively control information by implementing various functions required through baseband data software programming. Computer control and digital baseband technology are used to achieve flexible and precise control of the working parameters of the RF signal. The modulated data message meets the full set of protocols of the 406MHz second-generation distress beacon of the global satellite search and rescue system. Various working parameters of the search and rescue beacon signal can be flexibly controlled. It has good flexibility.

[0103] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0104] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A second generation distress beacon generating device for a global satellite search and rescue system, characterized in that: include: A digital information coding module is used to generate the coding of the second-generation distress beacon digital message of the global satellite search and rescue system and divide it into two digital messages IQ according to odd and even numbers; A spread spectrum code generation module, used to generate an even-odd two-way spread spectrum code that meets the standard requirements of the second generation distress beacon of the global satellite search and rescue system; A baseband data generation module, used to generate baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code; as well as The software radio transmitting module is used to control the software radio hardware platform so that the software radio hardware platform generates a search and rescue signal that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data.

2. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 1, characterized in that: The baseband data generation module includes an I-channel data expansion module, a first XOR operation module, a first mapping module and a first signal shaping filter, wherein: The I-channel data expansion module is used to expand each digital message in the 150-bit I-channel digital message in the distress beacon digital message into 256 bits to generate an expanded I-channel digital information; The first XOR operation module is used to perform an XOR operation on the expanded I-channel digital information and I-channel spread spectrum code; The first mapping module is used to map the code elements obtained after the XOR operation into signal levels, wherein code element 0 is mapped into signal level 1, and code element 1 is mapped into signal level -1; and The first signal shaping filter is used to perform waveform shaping on the mapped signal level.

3. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 2, characterized in that: The baseband data generation module includes a Q-path data expansion module, a second XOR operation module, a delay module, a second mapping module and a second signal shaping filter, wherein: The Q-channel data expansion module is used to expand each digital message in the 150-bit Q-channel digital message in the distress beacon digital message into 256 bits to generate expanded Q-channel digital information; The second XOR operation module is used to perform an XOR operation on the extended Q-channel digital information and the Q-channel spread spectrum code to generate a Q-channel code element; The second mapping module is used to map the Q-path code elements into Q-path signal levels, wherein the Q-path code element 0 is mapped into a signal level 1, and the Q-path code element 1 is mapped into a signal level -1; The delay module is used to delay the Q channel signal level by 1 / 2 chip; and The second signal shaping filter is used to perform waveform shaping on the delayed Q-path signal level.

4. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 3, characterized in that: The first signal shaping filter and the second signal shaping filter both include: an upsampling submodule, a parameter setting submodule and a filtering submodule, wherein: The up-sampling submodule is used to up-sample the I-channel signal level or the Q-channel signal level after waveform shaping; The parameter setting submodule is used to select a root raised cosine filter and set a suitable roll-off coefficient for the root raised cosine filter; and The filtering submodule is used to filter the upsampled I-channel signal level or Q-channel signal level using a root raised cosine filter with the appropriate roll-off coefficient to normalize the amplitude of the I-channel signal level or the Q-channel signal level to between 0 and 1 and limit the baseband data spectrum.

5. The second generation distress beacon generating device of the global satellite search and rescue system according to any one of claims 1 to 4, characterized in that: The distress beacon digital message includes a preamble, a main data segment, a rotated data segment and a BCH error correction code, wherein the digital information encoding module includes a preamble generation module, a main data segment generation module, a rotated data segment generation module and a BCH error correction code generation module, wherein, The preamble code generation module is used to set all preamble codes to 0; The main data segment generation module is used to set the value of the main data segment, wherein the main data segment includes the serial number, type, country code, location data and spare bits of the beacon; The rotation data segment generating module is used to set the value of the rotation data segment, wherein the rotation data segment includes a flag bit and a beacon activation mode; and The BCH error correction code generation module is used to calculate the error correction code according to the main data segment and the rotated data segment.

6. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 5, characterized in that: The serial number of the beacon, encoded as 14 bits in the main data segment; The type of the beacon, encoded as 3 bits in the main data segment; The country code of the beacon, encoded as 10 bits in the main data segment, the country code of the beacon is based on the International Telecommunication Union Maritime Identification Number Country Code; The position data, encoded as 47 bits in the main data segment, includes a latitude flag, an integer portion of the latitude data, a fractional portion of the dimension data, a longitude flag, an integer portion of the longitude data, and a fractional portion of the precision data; and The spare bit is encoded as the 14th bit in the main data segment and is set to 1.

7. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 5, characterized in that: The BCH error correction code generation module includes: An expansion submodule, used for adding 0 before and after the digital message generated by the front main data segment generation module and the rotation data segment generation module to generate an expanded 255-bit data; A data fetching submodule is used to find the position of the first non-zero element from the expanded 255-bit data, mark the position of the first non-zero element and fetch 48 bits thereafter to form 49 bits of data; An XOR submodule, used for performing an XOR operation on the 49-bit data and a given 49-bit data generator polynomial coefficient, wherein the given 49-bit data is the same in each cycle; The repeated data fetching submodule is used to find the position of the first non-zero element in the obtained value, remove all the leading zero elements, and add the corresponding digital message after it to re-form the 49-digit digital message; and The loop submodule is used to repeatedly perform XOR operations and re-take data processing until the 255-bit digital message is taken, and the last 48 bits of the last 49-bit data obtained are taken as the final BCH error correction code.

8. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 5, characterized in that: The spread spectrum code generation module comprises: An initial value generation module, used for setting different initial values ​​of 23 linear feedback shift registers according to different IQ branches, wherein the 23 linear feedback shift registers are numbered 0-22; An output module, used for outputting the value of the 0th linear feedback shift register; An operation module, used for performing an XOR operation on the value of the 0th linear feedback shift register and the value of the 18th linear feedback shift register, and using the XOR operation result as the value of the 22nd linear feedback shift register at the next moment; A right shift module, used for right shifting the value of the linear feedback shift register from the 22nd to the 1st at the previous moment as the value of the linear feedback shift register from the 21st to the 0th at the next moment; The chip generation module is used to take the 0th register value as the output, repeat the XOR operation and right shift processing until 2 23 - 1 chip; and The spread spectrum code generation module is used to generate 2 23 -1 code chip is truncated into 38400, which are used as the spreading codes for I and Q channel outputs respectively.

9. The second generation distress beacon generating device of the global satellite search and rescue system according to claim 4, characterized in that: The software radio transmission module includes a zero intermediate frequency architecture orthogonal up-conversion framework, a parameter setting module and a search and rescue signal transmission module, wherein: The zero intermediate frequency architecture orthogonal up-conversion framework is used to initialize the software radio hardware platform based on the zero intermediate frequency architecture; The parameter setting module is used to control key parameters using software radio technology, wherein the key parameters include the clock frequency, radio frequency channel, and center frequency and gain of the transmission signal of the software radio hardware platform; and The search and rescue signal transmitting module is used to call the data transmitting interface to transmit the generated baseband data.

10. A method for generating a second generation distress beacon for a global satellite search and rescue system, characterized in that: include: Generate the code of the second-generation distress beacon digital message of the global satellite search and rescue system and divide it into two digital messages IQ according to odd and even numbers; generating an even-odd two-way spread spectrum code that meets the standard requirements of the second generation distress beacon of the global satellite search and rescue system; Generate baseband IQ two-way data based on the IQ two-way digital message and the IQ two-way spread spectrum code; as well as The software radio hardware platform is controlled so that the software radio hardware platform generates a search and rescue signal that meets the standard requirements of the second-generation distress beacon of the global satellite search and rescue system based on the baseband IQ two-way data.

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