CN111555796A - Satellite load system integrating AIS (automatic identification System) and ADS-B (automatic dependent Surveillance-broadcast) message receiving functions - Google Patents

Abstract

The embodiment of the invention provides a satellite load system integrating AIS and ADS-B message receiving functions, wherein a power supply module is used for filtering and converting a primary power supply and providing electric energy; the interface module completes the communication between the load and the star and the transmission of the instruction and the data; the baseband processing module responds to the satellite command, completes code modulation and DA conversion of a signal to be transmitted, and transmits the signal to the channel processing module; completing AD conversion and demodulation decoding of signals from a channel receiving channel of the channel processing module, and storing or forwarding analyzed data according to an instruction; the channel processing module is responsible for carrying out frequency conversion, filtering and amplification on the transmitting signal and sending the amplified signal to the antenna module; filtering, amplifying and down-converting the received signal from the antenna module, and sending the processed signal to the baseband processing module through a cable for further processing; the antenna module completes electromagnetic conversion of the AIS signal and the ADS-B signal.

Description

Satellite load system integrating AIS (automatic identification System) and ADS-B (automatic dependent Surveillance-broadcast) message receiving functions

Technical Field

The invention belongs to the technical field of satellite communication, and particularly relates to a satellite load system integrating AIS and ADS-B message receiving functions.

Background

The universal Automatic Identification System (AIS) for ship is a new type of ship collision avoidance system. The shipborne AIS transceiver is a signal transceiver equipped on a ship, and the device broadcasts dynamic and static information of the ship collected by a sensor and manually placed outwards in real time on one hand and captures dynamic and static information of other ships around on the other hand, so that the ship can master the surrounding marine environment in real time. The satellite-borne AIS signal reconnaissance system can receive AIS signals of ships in hundreds of or thousands of oceans through low-orbit satellite assembly and can transmit the AIS signals to a ground station receiving system, and ship information tracking of national peripheral sea areas and even global sea areas can be achieved [1 ].

The broadcast type automatic correlation monitoring ADS-B technology is the core of the new generation of civil aviation monitoring technology, the attributes, the current longitude and latitude, the altitude, the navigational speed and the like of an airplane are continuously broadcast through a special wireless data link, the satellite-borne ADS-B receiver is carried on a satellite, the function of the satellite-borne ADS-B receiver is equivalent to a ground base station, as long as the airplane is in the coverage area of a corresponding satellite, the satellite carrying the ADS-B receiver can receive the real-time state information of the airplane broadcast, and the information is transmitted back to a ground control system through a data link, so that the real-time forwarding in the environment and the storage and forwarding outside the country are realized [2 ].

The load in the document [3] integrates the functions and characteristics of four types of data acquisition loads, namely ADS-B, AIS and GNSS-R, DCS, solves the hardware problem of receiving the same load of signals of different frequency bands and different systems through a Software Defined Radio (SDR) and a different-plane configuration antenna, realizes the software module mounting of different load functions through a flexible hardware architecture, and realizes the multi-load integrated design.

Document [4] designs a new miniaturized satellite borne Automatic Identification System (AIS) antenna of M configuration. The antenna has the advantages of small size, light weight, convenience in star body installation and the like, and the overall dimension of the antenna is only 324mm multiplied by 60mm multiplied by 263.2 mm. CST MICROWAVE STUDIO electromagnetic software is adopted to carry out simulation design, and real object single machine test and radiation model star (RM) test are carried out in a spherical near field.

In the literature [5], aiming at the technical problems of multi-network signal collision, doppler shift, spatial link attenuation and the like caused by the development of a traditional ground automatic identification system to a satellite-borne automatic identification system, a Tiantu one satellite-borne automatic identification system is designed, and comprises system composition, receiver indexes and functions, antenna and microwave switch design, link level of the satellite-borne automatic identification system is estimated, a space application performance test and an environment test scheme of an automatic identification system receiver are mainly introduced, and an on-orbit application condition of the Tiantu one satellite-borne automatic identification system is introduced.

The AIS signal reception based on low earth orbit satellite is proposed for the first time by the USCG of the United states since 2002, the feasibility analysis of satellite-borne AIS is carried out successively in the countries of the United states, Norway, Canada, Germany and the like, the technical details are deeply researched make internal disorder or usurp, and satellite-borne AIS satellites are successively transmitted for the commercial expansion of satellite-borne AIS.

The American Iridium satellite company as a system provider for constructing ADS-B satellite constellations by first global families has transmitted two batches of 20 second-generation satellites carrying ADS-B receivers in total by 6 months in 2017, and will fully deploy and put into operation the total amount of 75 (66+9) second-generation satellite constellations before 2018 years, and fully provide satellite ADS-B data services [2] globally. Certain research is also carried out on satellite-borne ADS-B in Europe, including research on satellite-borne ADS-B load, on-orbit demonstration and verification of ADS-B satellite and the like.

Document [1] Yan, Majinxin. AIS general vessel automatic identification system introduction, digital technology and application, 9.2018, 9.9, 36 th volume, 9 th volume.

Document [2] Wangrundon, Panwei, aircraft tracking and monitoring development profiles and trends based on satellite-borne ADS-B design and research, 2018, phase 1, general phase 254, p15-17.

The file [3] wu xiandan, zhangcheng, liu wei liang, tao yulong, a research of global data acquisition and load exchange technology, space electronic technology, first phase of 2018, p97-104.

The design and application of a novel satellite-borne miniaturized AIS antenna are disclosed in [4] Liu Ming, Yang Xiao Yong, the Proc of terahertz science and electronic information, 6 months in 2018, 16 th volume, third phase, p470-474.

Document [5] chenlihu, chenyiqian, zhao, chenyun, tiantuo 1 star-based automatic identification system design and on-orbit application, university of defense science and technology, 2015, 2 month, 37, first phase, p65-69.

Disclosure of Invention

The invention aims to provide a satellite load system integrating AIS and ADS-B message receiving functions, which is characterized by comprising a power module, an interface module, a baseband processing module, a channel processing module and an antenna module, wherein the power module is used for filtering and converting a primary power supply and supplying electric energy to other modules of a load; the interface module is respectively connected with the satellite affair and the baseband processing module to complete the communication between the load and the satellite affair and the transmission of instructions and data; the baseband processing module responds to the satellite command, completes code modulation and DA conversion of a signal to be transmitted, and transmits the signal to the channel processing module; on the other hand, AD conversion, demodulation and decoding are carried out on the signals from the channel processing module receiving channel, and the analyzed data are stored or forwarded according to the instruction; the channel processing module is responsible for carrying out frequency conversion, filtering and amplification on the transmitting signal and sending the amplified signal to the antenna module; filtering, amplifying and down-converting the received signal from the antenna module, and sending the processed signal to the baseband processing module through a cable for further processing; the antenna module completes electromagnetic conversion of the AIS signal and the ADS-B signal.

Preferably, the baseband processing module includes an input unit, an output unit, a processing unit, and a power supply unit.

Preferably, the input unit adopts an AD9258 to receive and process two paths of signals, namely an ADS-B signal and an AIS signal; wherein, the ADS-B signal is 70MHz, and the AIS signal is 10.7 MHz; the SNR of AD9258 is 77.6dB, and the spurious free dynamic range SFDR is 88dBc (70MHz, 125 MSPS).

Preferably, the FPGA of the processing unit employs XC6SLX150T in the xilinx spartan6 series; the monitoring FPGA is an antifuse FPGA-A54 SX32 from Actel.

Preferably, the output unit selects an LSF0108 level conversion chip and a CAN interface chip to deal with instruction and data interaction; the CAN bus interface uses TCAN337G of TI, the working temperature is-40-125 degrees, the power consumption is low, and the EMC protection level is high; the level conversion chip uses LSF010X series, the highest voltage conversion rate of 100MHz is supported, arbitrary voltage conversion between 1V and 5V is realized, and the working temperature is-40 to 125 degrees.

Preferably, after the power supply unit is connected to the baseband through the power supply module 5V and passes through the DC-DC isolation module, the power supply unit outputs 3.3V and 1.0V through the two LM20123, and one LP38853 outputs 1.8V.

Preferably, the GMSK demodulation method for the AIS signal is: firstly, AD sampling and quantizing signals, respectively mixing the signals with quantized signals through carrier signals generated by NCO, then passing through a low-pass filter after mixing, then obtaining baseband signals through a differential demodulation formula, then performing matched filtering through a Gaussian filter, and finally obtaining original binary signals through bit synchronization. And the demodulated signal is subjected to frame decoding through a specified frame format to obtain the AIS original message.

Preferably, the processing method of the ADS-B signal is as follows: firstly, performing AD sampling on input after radio frequency detection, filtering clutter interference of the sampled signal through a low-pass filter, then performing correlation detection on 8us fixed headers, and if a peak value exists and is greater than a certain number N, respectively adding amplitudes of sampling points in each bit to obtain a chip0_ a and a chip1_ a; on one hand, calculating the difference value chip _ a _ dif between each bit chip0_ a and chip1_ a, sorting the chip _ dif corresponding to 112 bits from small to large, wherein the minimum 5 bits are 5 low confidence degrees, and on the other hand, comparing that chip0_ a is larger than chip1_ a? If so, taking 1 as the bit, otherwise, taking 0 to obtain 112 initial messages adsb _ code; and (3) bit negating 5 low-confidence bits in the adsb _ code in a permutation and combination mode, then checking whether CRC (cyclic redundancy check) passes, and if so, finishing the decoding of the message to obtain the ADS-B original message.

Preferably, the antenna module includes an AIS receive antenna unit and an ADS-B receive antenna unit.

Preferably, the AIS receiving antenna unit is installed in a split mode and comprises 4 VHF antennas, 4 in-phase high-frequency cables and a feed network, the 4 VHF antennas in the satellite are installed on a + Z axis, namely, the single antenna is installed in a mode of inclining 30 degrees to the ground, and the task of the feed network is to provide phases of 0 degrees, 90 degrees, 180 degrees and 270 degrees for each antenna respectively so as to realize circular polarization;

the ADS-B receiving antenna unit adopts two L-wave antennas, is installed in an inclined horizontal mode for 30 degrees, works to form two independent beams respectively, and achieves that the gain of the antenna is larger than 5dB in the range from-45 degrees to +45 degrees in the one-dimensional direction through the two beams.

Drawings

FIG. 1 is a block diagram of a satellite AIS/ADS-B loading system according to an embodiment of the present invention;

FIG. 2 is a digital baseband functional block diagram of an embodiment of the present invention;

FIG. 3 is a block diagram of hardware components of the digital baseband according to the embodiment of the present invention;

fig. 4 is a flowchart of a GMSK demodulation method according to an embodiment of the present invention;

FIG. 5 is a decoding flow chart of ADS-B message according to the embodiment of the present invention;

FIG. 6 is an AIS antenna schematic diagram of an embodiment of the present invention;

FIG. 7 is a schematic diagram of a VHF antenna according to an embodiment of the present invention;

FIG. 8 is a diagram of an ADS-B receiving antenna according to an embodiment of the present invention;

fig. 9 is an antenna mounting diagram according to an embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The system provided by the invention is modularized as a whole, and is divided into five parts, namely a power supply module, an interface module, a baseband processing module, a channel processing module and an antenna module, according to the function and application requirements. Each module is spatially isolated by a cavity.

The power supply module of the satellite load system mainly completes the filtering and conversion of a primary power supply, and meets the requirement of normal power supply of other modules of the load; the interface module mainly completes the communication between the load and the satellite affairs and completes the transmission of instructions and data; the baseband processing module completes the response to the satellite command, completes the code modulation and DA conversion of the signal to be transmitted on one hand, and transmits the signal to the channel processing module. On the other hand, AD conversion, demodulation and decoding are carried out on signals from a channel receiving module, and analyzed data are stored or forwarded and the like according to the instructions; the channel processing module is responsible for carrying out frequency conversion, filtering and amplification on the transmitted signal and sending the amplified signal to the antenna; filtering, amplifying and down-converting the received signals from the antenna, and sending the processed signals to a baseband processing module through a cable for further processing; the antenna module mainly completes electromagnetic conversion of AIS signals and ADS-B signals. The system block diagram is shown in fig. 1.

The satellite AIS/ADS-B load can receive VHF frequency band uplink signals sent by a ship, demodulate AIS information and send the AIS information to a satellite computer; and the system can also receive an L-band uplink signal sent by an aircraft, demodulate an ADS-B message and send the ADS-B message to a satellite computer.

According to one embodiment of the present invention, the baseband processing module includes input/output, storage, processing, and power supply units. Referring to fig. 2 and fig. 3, 2 signals, namely 70MHz of ADS-B and 10.7MHz of AIS, are processed by the baseband input part baseband. SNR of AD9258 was 77.6dB, Spurious Free Dynamic Range (SFDR): 88dBc (70MHz, 125MSPS), can meet the requirements. And the baseband hardware module completes AD conversion, demodulation and decoding of the signals of the receiving channel, and stores or forwards the analyzed data according to the instruction.

The processing unit adopts XC6SLX150T with 14 ten thousand resources in xilinx spartan6 series. To meet rate and resource requirements. The core operating voltage of the device is 1.0V, and the I/O operating voltage is 1.8V. Through resource budget analysis, the requirement of satellite load can be met. The monitoring FPGA is an anti-fuse FPGA of Actel company, namely A54SX32, and the chip mainly has the functions of system state monitoring and management, XC6SLX150T program loading control, fault diagnosis and the like. Therefore, the device must be most reliable. Generally, because of its special technology (not based on SRAM), an FPGA with antifuse has a much smaller probability of generating SEU than an FPGA based on SRAM structure, which also makes it particularly suitable for aerospace with certain radiation. Devices of this type are currently widely used in the aerospace field. The periphery of the FPGA also comprises a 66MHz crystal oscillator as an external clock source. And clock requirements are provided for each module of the system through internal frequency division and multiplication. Since the bandwidth of the system is 100KHz at most, the sampling clock is designed to be 2M, and the clock is obtained by FPGA through internal frequency division.

And an LSF0108 level conversion chip and a CAN interface chip are selected as an output part to deal with instruction and data interaction. The CAN bus interface uses TI's TCAN337G, operating temperature-40 ° to 125 °, low power consumption and high EMC protection level. The level conversion chip uses LSF010X series, the highest voltage conversion rate of 100MHz is supported, arbitrary voltage conversion between 1V and 5V can be realized, and the working temperature is-40 degrees to 125 degrees.

The power supply part is connected to a baseband through a power supply module 5V, and outputs 3.3V and 1.0V through two LM20123 and outputs 1.8V through one LP38853 after passing through a DC-DC isolation module (MORNUN WRB 0505S-3W).

As shown in fig. 4, it is a GMSK demodulation process method for AIS signals. The GMSK demodulation process of the AIS signal comprises the steps of firstly carrying out AD sampling quantification on the signal, generating carrier signals through NCO, respectively carrying out frequency mixing with the quantified signal, then carrying out low-pass filter after frequency mixing, then obtaining a baseband signal through a differential demodulation formula, then carrying out matched filtering through a Gaussian filter, and finally obtaining an original binary signal through bit synchronization. And the demodulated signal is subjected to frame decoding through a specified frame format to obtain the AIS original message.

FIG. 5 shows a signal processing method of ADS-B. The signal processing process of ADS-B is that firstly, AD sampling is carried out by input after radio frequency detection, clutter interference of the sampled signals is filtered through a low-pass filter, then correlation detection is carried out on 8us fixed headers, if a peak value exists and is larger than a certain number N, amplitude values of sampling points in each bit are respectively added to obtain a chip0_ a and a chip1_ a, on one hand, the difference chip _ a _ dif between each bit chip0_ a and chip1_ a is calculated, chip _ dif corresponding to 112 bits is sorted from small to large, and the minimum 5 bits are 5 low confidence coefficients. On the other hand, is the comparison chip0_ a greater than chip1_ a? If so, the bit is 1, otherwise, 0 is selected, and 112 bits of initial message adsb _ code are obtained. And (3) bit negating 5 low-confidence bits in the adsb _ code in a permutation and combination mode, then checking whether CRC (cyclic redundancy check) passes, and if so, finishing the decoding of the message to obtain the ADS-B original message.

The AIS original message and the ADS-B original message CAN be obtained through the processing of the method and are transmitted to the house service computer through a 422 serial port or a CAN bus.

As shown in fig. 6, is a schematic diagram of an AIS antenna product. The VHF antenna schematic is shown in fig. 7. The AIS receiving antenna is designed as follows, in the satellite flight scanning process, gain in the range of-45 degrees to +45 degrees is larger than 0dB in the one-dimensional direction, and the AIS receiving antenna has a circular polarization characteristic, and because a single antenna can not meet the condition, a right-hand circular polarization wave beam is formed by the four antenna array, and the gain of the antenna in the range of-45 degrees to +45 degrees is larger than 0dB in the one-dimensional direction, so that the normal communication of the satellite is smoothly realized.

The antenna subsystem is installed in a split mode and comprises 4 VHF antennas, 4 in-phase high-frequency cables and a feed network, wherein the 4 VHF antennas in the satellite are installed on a + Z-axis (to the ground), the single antenna is installed in a tilted mode by 30 degrees, and the task of the feed network is to provide phases of 0 degrees, 90 degrees, 180 degrees and 270 degrees for each antenna respectively so as to achieve circular polarization.

The ADS-B receiving antenna is designed as shown in figure 8, the gain of the ADS-B receiving antenna is larger than 5dB in the range from minus 45 degrees to plus 45 degrees in the one-dimensional direction in the satellite flight scanning process, and because a single antenna cannot meet the condition, two antennas (which are installed in a tilted horizontal 30 degrees and are shown in figure 9 in detail) are recommended to work respectively to form two independent beams, and the gain of the antenna is achieved by the two beams together to achieve that the gain of the antenna is larger than 5dB in the range from minus 45 degrees to plus 45 degrees in the one-dimensional direction, so that the normal communication of the satellite is smoothly achieved.

The VHF antenna adopts a tape measure antenna (monopole antenna) type, and the structure is simple. The VHF tape antenna is unfolded after being in orbit, and the size before the orbit is far lower than that of the existing VHF antenna at home and abroad. The whole satellite envelope is effectively reduced, the rocket can carry more loads, the launching cost is effectively reduced, and the using efficiency of the rocket is improved. The tape antenna is arranged on the surface of the Z-axis star body and adopts a bottom feed mode. The working frequency of the ADS-B antenna is 1090MHz, and the ADS-B antenna belongs to an L wave band. And a single-arm spiral antenna type is adopted, so that the structure is simple. The single-arm helical antenna adopts a bottom feed mode, and has the advantages of simple structure, simple feed and good circular polarization effect.

The antenna design is an important part of the whole load design and is also a main part influencing the load performance. According to the installation position and normal phase of the antenna of the ship and the aircraft, a loading antenna is designed, the loading antenna consists of a VHF antenna and an L-band antenna, and the beam coverage range of the loading antenna is +/-45 degrees. The antennas of both ships and aircraft are linearly polarized. The circularly polarized antennas are adopted for both the satellite load antennas, and although the polarization loss is 3dB, the missing detection probability can be reduced by the polarization mode.

The satellite AIS/ADS-B load comprises a VHF satellite-shore ship link data exchange system and an L-frequency satellite aircraft information acquisition system, integrates AIS and ADS-B functions, and realizes data communication between an offshore ship and a shore station and an information collection function of an aircraft provided with the ADS-B system through a satellite-ground communication physical link defined by ITU, so that the invention can realize the following functions: and the system supports ITU-R M.1371-5, ITU-R M.2092-0, IEC61162-1 and IEC61162-450 standards. The DO-260B protocol standard is supported; integrating 1090ES data information acquisition function; integrating automatic identification system functions; the VHF frequency band-based ship information collection function between the satellites and the ships is supported; supporting the navigation information collection function based on the S mode between the star and the aircraft; the system has a self-checking function, and can respond to a self-checking instruction and output a fault code; framing the data message again and sending the data message to a satellite computer; the data storage is not less than 4 Gbit; support satellite applications with orbit altitudes of 1100km and below.

Meanwhile, the invention has the following technical effects:

1. the satellite AIS/ADS-B load can receive the VHF frequency band uplink signal sent by the ship, demodulate AIS information and send the AIS information to the satellite computer; and the system can also receive an L-band uplink signal sent by an aircraft, demodulate an ADS-B message and send the ADS-B message to a satellite computer.

2. The VHF antenna adopts a tape measure antenna (monopole antenna) type, and the structure is simple. The VHF tape antenna is unfolded after being in orbit, and the size before the orbit is far lower than that of the existing VHF antenna at home and abroad. The whole satellite envelope is effectively reduced, the rocket can carry more loads, the launching cost is effectively reduced, and the using efficiency of the rocket is improved. The tape antenna is arranged on the surface of the Z-axis star body and adopts a bottom feed mode. The working frequency of the ADS-B antenna is 1090MHz, and the ADS-B antenna belongs to an L wave band. And a single-arm spiral antenna type is adopted, so that the structure is simple. The single-arm helical antenna adopts a bottom feed mode, and has the advantages of simple structure, simple feed and good circular polarization effect.

3. And the baseband hardware module completes AD conversion, demodulation and decoding of the signals of the receiving channel, and stores or forwards the analyzed data according to the instruction.

4. The AIS original message and the ADS-B original message CAN be obtained through the baseband software processing, and are transmitted to the housekeeping computer through a 422 serial port or a CAN bus.

It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. A satellite load system integrating AIS and ADS-B message receiving functions is characterized by comprising a power supply module, an interface module, a baseband processing module, a channel processing module and an antenna module, wherein the power supply module is used for filtering and converting a primary power supply and supplying electric energy to other modules of a load; the interface module is respectively connected with the satellite affair and the baseband processing module to complete the communication between the load and the satellite affair and the transmission of instructions and data; the baseband processing module responds to the satellite command, completes code modulation and DA conversion of a signal to be transmitted, and transmits the signal to the channel processing module; on the other hand, AD conversion, demodulation and decoding are carried out on the signals from the channel processing module receiving channel, and the analyzed data are stored or forwarded according to the instruction; the channel processing module is responsible for carrying out frequency conversion, filtering and amplification on the transmitting signal and sending the amplified signal to the antenna module; filtering, amplifying and down-converting the received signal from the antenna module, and sending the processed signal to the baseband processing module through a cable for further processing; the antenna module completes electromagnetic conversion of the AIS signal and the ADS-B signal.

2. The satellite loading system of claim 1, wherein the baseband processing module comprises an input unit, an output unit, a processing unit, and a power supply unit.

3. The satellite loading system of claim 2, wherein the input unit receives and processes two signals, an ADs-B signal and an AIS signal, using an AD 9258; wherein, the ADS-B signal is 70MHz, and the AIS signal is 10.7 MHz; the SNR of AD9258 is 77.6dB, and the spurious free dynamic range SFDR is 88dBc (70MHz, 125 MSPS).

4. The satellite loading system of claim 2, wherein the FPGA of the processing unit employs XC6SLX150T in the xilinxspartan6 series; the monitoring FPGA is an antifuse FPGA-A54 SX32 from Actel.

5. The satellite loading system of claim 2, wherein the output unit selects an LSF0108 level conversion chip and a CAN interface chip for command and data interaction; the CAN bus interface uses TCAN337G of TI, the working temperature is-40-125 degrees, the power consumption is low, and the EMC protection level is high; the level conversion chip uses LSF010X series, the highest voltage conversion rate of 100MHz is supported, arbitrary voltage conversion between 1V and 5V is realized, and the working temperature is-40 to 125 degrees.

6. The satellite loading system of claim 2, wherein the power supply unit is connected to the baseband via a power supply module at 5V, and outputs 3.3V and 1.0V via two LM20123 and outputs 1.8V via one LP38853 after passing through the DC-DC isolation module.

7. The satellite loading system of claim 1 wherein the method for GMSK demodulation of the AIS signals comprises:

firstly, AD sampling and quantizing signals, generating carrier signals through NCO, respectively mixing the carrier signals with the quantized signals, and then passing through a low-pass filter after mixing;

then, a baseband signal is obtained through a differential demodulation formula, and matched filtering is carried out through a Gaussian filter;

finally, obtaining an original binary signal through bit synchronization; and the demodulated signal is subjected to frame decoding through a specified frame format to obtain the AIS original message.

8. The satellite loading system of claim 1, wherein the processing method of the ADS-B signal comprises:

firstly, performing AD sampling by input after radio frequency detection, and filtering clutter interference of a sampled signal by a low-pass filter;

then, carrying out correlation detection on the 8us fixed headers, and if a peak value exists and is greater than a certain number N, respectively adding amplitudes of sampling points in each bit to obtain a chip0_ a and a chip1_ a;

on one hand, the difference value chip _ a _ dif between each bit chip0_ a and chip1_ a is calculated, the chip _ difs corresponding to 112 bits are sorted from small to large, and the minimum 5 bits are 5 low confidence coefficients; on the other hand, whether chip0_ a is larger than chip1_ a is compared, if so, the bit is 1, otherwise, 0 is selected, and 112 initial messages adsb _ code are obtained; negating 5 low confidence bits in the adsb _ code bit by bit in a permutation and combination mode;

and then checking whether the CRC passes, if so, finishing the decoding of the message to obtain the ADS-B original message.

9. The satellite loading system of claim 1, wherein the antenna modules comprise an AIS receive antenna unit and an ADS-B receive antenna unit.

10. A satellite loading system according to claim 9 wherein the AIS receive antenna unit is of split mounting and comprises 4 VHF antennas, 4 in-phase high frequency cables and a feed network, the 4 VHF antennas of the satellite being mounted on the + Z axis, i.e. to ground, with the single antenna being mounted at an inclination of 30 °, and wherein the feed network is tasked to provide each antenna with a phase of 0 °, 90 °, 180 ° and 270 ° respectively for circular polarisation;

the ADS-B receiving antenna unit adopts two L-wave antennas, is installed in an inclined horizontal mode for 30 degrees, works to form two independent beams respectively, and achieves that the gain of the antenna is larger than 5dB in the range from-45 degrees to +45 degrees in the one-dimensional direction through the two beams.

Images