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Principle, description of AIS work
Principle, description of AIS work
28.05.2015
GNSS Receiver The
equipment can be equipped with different models of GNSS receivers. The most preferred models are the combined GLONASS / GPS / Galileo 3K-641 receiver. Full documentation for receivers can be obtained from manufacturers.
The signals from the satellites go to the active antenna, the power supply for which comes from the GNSS receiver through the radio frequency cable. The nominal supply voltage of the active antenna is + 3.3 V. The radio path provides reception, amplification, frequency filtering of satellite radio signals coming from an external antenna and the generation of output level-quantized signals necessary for subsequent processing. The built-in microprocessor provides calculation of the radio navigation parameters measured in each receiver-measuring channel, collection, transformation and storage of service information, solution of the navigation task. The GNSS receiver contains electrically reprogrammable read-only memory, some of which is reserved for storing important operational data (non-volatile memory). From the controller
UAIS transponder receive commands to control the operation of the GNSS receiver via the RS-232C channel. On the same port, the navigation information in the RTCM SC-104.3 format is sent to the controller. The second RS-232C exchange channel serves to transfer the values of differential corrections from external sources.
Transceiver board
The transmitter of the system carries out frequency modulation with subcarriers and amplification of the radio signal through the AIS channels, for which the transmitter synthesizer frequency is preset.
The low-frequency subcarrier of the UAIS channels from the output of the digital-to-analog converter filter located in the controller is fed to the modulation input of the voltage-controlled oscillator at the output of which a modulated radio signal with a center frequency of 28.000 MHz is formed. Further modulated radio signal through the key goes to the signal input of the mixer, the oscillator of which is the frequency synthesizer. The frequency of the synthesizer is set by the AIS controller in such a way that at the output of the mixer the useful components of the radio signal spectrum are in the given frequency channel.
Then, the product formed in the mixer is filtered by a surfactant filter to suppress the side components, and then the filtered radio signal enters the gain path. In it, the radio signal is pre-amplified, after which it enters another SAW filter for additional filtering and, after this, on the pre-term gain cascade. Then the signal is fed to the terminal amplifying module, which provides the required transmitter power level, which is set from the controller by changing the level of one of the supply voltages of this module. The by-products of the terminal module are filtered in the harmonic filter. The harmonic filter is synthesized, as an elliptic filter of the 7th order. The radio signal of the given power from the final amplifying module is fed to the directional coupler and the antenna switch. Directional coupler with two-channel
detector and amplifier is used to measure the standing wave ratio (SWR). The circuit detects and scales the response signals of the incident and reflected waves. The signals generated in this way are fed to the ADC in the AIS controller for subsequent evaluation of the SWR. Antenna switch on the PIN-diodes serves for electronic switching of the radio signal from the transmitter to the antenna and from the antenna to the receiver.
In the reception mode, the received radio signal is transmitted via the antenna switch to the SAW filter, where a preliminary frequency selection of the UAIS frequency band (156.025 ÷ 162.025 MHz) occurs. The filtered signal is then fed to a radio frequency (RF) amplifier, in which the required amplification necessary for the proper functioning of the further nodes of the circuit is carried out. The amplified radio signal after the URF is fed to a three-channel splitter. From the output of the splitter, each of the received signals goes to the input of the corresponding receive channel, two TDMA receivers and one DSC.
The TDMA receiver module amplifies, filters and demodulates the modulated radio signals on two TDMA channels. From the output of the splitter, the received radio signal is further filtered by the SAW filter and fed to the mixer of the first intermediate frequency. As the heterodyne oscillations of the radio frequency mixers, the synthesizer outputs are output, which are reconstructed according to the commands of the controller. The frequencies of the synthesizers are set in such a way as to provide a useful frequency response at the output of the mixers at a central frequency of 21.4 MHz. The built-in software of the controller forms a range of tuning of frequency synthesizers in such a way as to ensure reception of signals in the frequency bands156,0125 ÷ 158,0125 MHz and160,6125 ÷ 162,0375 MHz, by default the signal reception is performed at frequencies of161.975 MHz and 162.025 MHz. Further, the signal of the first intermediate frequency of each of the reception channels is directed to the quartz filters, which ensure the preliminary selectivity of the receivers over the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. which provide preliminary selectivity of receivers on the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. which provide preliminary selectivity of receivers on the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. limitations and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. limitations and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller.
The DSC receiver module receives the signal from the output of the splitter and is processed in the same circuit nodes as in the TDMA channels.
Class A transceivers .
They are intended for installation on merchant ships, such as cargo ships and large passenger ships. Class A transceivers transmit data with a higher VHF signal power than Class B transceivers, so these signals can be received at more remote vessels. In addition, these signals are relayed more often. The presence of Class A transceivers is mandatory on all ships with a displacement of more than 300 tonnes gross on international flights and on certain types of passenger ships operating under the mandate of SOLAS.
AIS stations for inland navigation. Similar to Class A transceivers, but have additional functions for use on inland waterways. Class B transceivers are in many respects similar to Class A transceivers, but they tend to have a lower cost due to less stringent performance requirements. Class B transceivers transmit data with lower signal power and with a lower data rate than Class A transceivers. On some devices, it is possible to disable the display of different AIS classes. you can disable, for example, coast stations, class B or AIS, which does not change position more than some time.
equipment can be equipped with different models of GNSS receivers. The most preferred models are the combined GLONASS / GPS / Galileo 3K-641 receiver. Full documentation for receivers can be obtained from manufacturers.
The signals from the satellites go to the active antenna, the power supply for which comes from the GNSS receiver through the radio frequency cable. The nominal supply voltage of the active antenna is + 3.3 V. The radio path provides reception, amplification, frequency filtering of satellite radio signals coming from an external antenna and the generation of output level-quantized signals necessary for subsequent processing. The built-in microprocessor provides calculation of the radio navigation parameters measured in each receiver-measuring channel, collection, transformation and storage of service information, solution of the navigation task. The GNSS receiver contains electrically reprogrammable read-only memory, some of which is reserved for storing important operational data (non-volatile memory). From the controller
UAIS transponder receive commands to control the operation of the GNSS receiver via the RS-232C channel. On the same port, the navigation information in the RTCM SC-104.3 format is sent to the controller. The second RS-232C exchange channel serves to transfer the values of differential corrections from external sources.
Transceiver board
The transmitter of the system carries out frequency modulation with subcarriers and amplification of the radio signal through the AIS channels, for which the transmitter synthesizer frequency is preset.
The low-frequency subcarrier of the UAIS channels from the output of the digital-to-analog converter filter located in the controller is fed to the modulation input of the voltage-controlled oscillator at the output of which a modulated radio signal with a center frequency of 28.000 MHz is formed. Further modulated radio signal through the key goes to the signal input of the mixer, the oscillator of which is the frequency synthesizer. The frequency of the synthesizer is set by the AIS controller in such a way that at the output of the mixer the useful components of the radio signal spectrum are in the given frequency channel.
Then, the product formed in the mixer is filtered by a surfactant filter to suppress the side components, and then the filtered radio signal enters the gain path. In it, the radio signal is pre-amplified, after which it enters another SAW filter for additional filtering and, after this, on the pre-term gain cascade. Then the signal is fed to the terminal amplifying module, which provides the required transmitter power level, which is set from the controller by changing the level of one of the supply voltages of this module. The by-products of the terminal module are filtered in the harmonic filter. The harmonic filter is synthesized, as an elliptic filter of the 7th order. The radio signal of the given power from the final amplifying module is fed to the directional coupler and the antenna switch. Directional coupler with two-channel
detector and amplifier is used to measure the standing wave ratio (SWR). The circuit detects and scales the response signals of the incident and reflected waves. The signals generated in this way are fed to the ADC in the AIS controller for subsequent evaluation of the SWR. Antenna switch on the PIN-diodes serves for electronic switching of the radio signal from the transmitter to the antenna and from the antenna to the receiver.
In the reception mode, the received radio signal is transmitted via the antenna switch to the SAW filter, where a preliminary frequency selection of the UAIS frequency band (156.025 ÷ 162.025 MHz) occurs. The filtered signal is then fed to a radio frequency (RF) amplifier, in which the required amplification necessary for the proper functioning of the further nodes of the circuit is carried out. The amplified radio signal after the URF is fed to a three-channel splitter. From the output of the splitter, each of the received signals goes to the input of the corresponding receive channel, two TDMA receivers and one DSC.
The TDMA receiver module amplifies, filters and demodulates the modulated radio signals on two TDMA channels. From the output of the splitter, the received radio signal is further filtered by the SAW filter and fed to the mixer of the first intermediate frequency. As the heterodyne oscillations of the radio frequency mixers, the synthesizer outputs are output, which are reconstructed according to the commands of the controller. The frequencies of the synthesizers are set in such a way as to provide a useful frequency response at the output of the mixers at a central frequency of 21.4 MHz. The built-in software of the controller forms a range of tuning of frequency synthesizers in such a way as to ensure reception of signals in the frequency bands156,0125 ÷ 158,0125 MHz and160,6125 ÷ 162,0375 MHz, by default the signal reception is performed at frequencies of161.975 MHz and 162.025 MHz. Further, the signal of the first intermediate frequency of each of the reception channels is directed to the quartz filters, which ensure the preliminary selectivity of the receivers over the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. which provide preliminary selectivity of receivers on the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. which provide preliminary selectivity of receivers on the "25 kHz" channel. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. After the quartz filters, the signal of the first intermediate frequency is fed to the input of the integrated conversion chip, which performs the functions of conversion to the second intermediate frequency of 455 kHz, limitation and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. limitations and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller. limitations and demodulation. The external ceramic filters connected to the chip provide selectivity for the adjacent channel. From the output of the demodulator, the signal is scaled by an operational amplifier, after which the signal acquires the required offset and amplitude. In addition to frequency demodulation of the received radio signal, the microcircuit of the mixer-demodulator provides an estimate of its power, over which an appropriate digital sample is generated in the controller.
The DSC receiver module receives the signal from the output of the splitter and is processed in the same circuit nodes as in the TDMA channels.
Class A transceivers .
They are intended for installation on merchant ships, such as cargo ships and large passenger ships. Class A transceivers transmit data with a higher VHF signal power than Class B transceivers, so these signals can be received at more remote vessels. In addition, these signals are relayed more often. The presence of Class A transceivers is mandatory on all ships with a displacement of more than 300 tonnes gross on international flights and on certain types of passenger ships operating under the mandate of SOLAS.
AIS stations for inland navigation. Similar to Class A transceivers, but have additional functions for use on inland waterways. Class B transceivers are in many respects similar to Class A transceivers, but they tend to have a lower cost due to less stringent performance requirements. Class B transceivers transmit data with lower signal power and with a lower data rate than Class A transceivers. On some devices, it is possible to disable the display of different AIS classes. you can disable, for example, coast stations, class B or AIS, which does not change position more than some time.