阅读说明：本技术 具有集成ais编解码能力的pdt对讲机 (PDT interphone with integrated AIS coding and decoding capability ) 是由 秦嗣波 展晓洁 张海超 汪轩 向浩威 雷志芳 于 2021-11-03 设计创作，主要内容包括：本发明公开了一种具有集成AIS编解码能力的PDT对讲机,该对讲机包括天线、信道机单元、基带单元和显示单元,AIS为GMSK调制方式,PDT为4FSK调制方式,信道机单元具备高速AD采样能力,基带单元存储有高速采样下AIS模式消息和PDT模式消息的调制和同步字的波形特征,该对讲机含有接收和发射流程。使用同一套信道机和基带单元兼容PDT和AIS模式,极大提高了设备的便携性,有效提升待机时间,海事作业人员可方便的携带设备与PDT互通或者使用AIS消息进行求助。使用同一信道机单元和基带单元自动识别信号模式,用户不需要手动切换即可接收两个模式的业务,使其可以更专注于现场作业,更简易的发起求助。(The invention discloses a PDT interphone with integrated AIS coding and decoding capability, which comprises an antenna, a channel unit, a baseband unit and a display unit, wherein the AIS is a GMSK modulation mode, the PDT is a 4FSK modulation mode, the channel unit has high-speed AD sampling capability, the baseband unit stores modulation and waveform characteristics of synchronous words of AIS mode messages and PDT mode messages under high-speed sampling, and the interphone comprises a receiving and transmitting process. The same channel machine and the same baseband unit are used for being compatible with the PDT and AIS modes, so that the portability of the equipment is greatly improved, the standby time is effectively prolonged, and maritime workers can conveniently carry the equipment and communicate with the PDT or use AIS messages for help. The same channel machine unit and the baseband unit are used for automatically identifying the signal mode, and a user can receive services in two modes without manually switching, so that the user can be more concentrated on field operation and can more easily initiate help seeking.)

1. The PDT interphone with the integrated AIS coding and decoding capability is characterized by comprising an antenna, a channel unit, a baseband unit and a display unit, wherein the baseband unit adopts an integrated multiply-add unit and a DSP (digital signal processor) with a high-speed SSI (Small scale integration) communication interface as a core processing device and stores modulation of AIS mode messages and PDT mode messages under high-speed sampling and waveform characteristics of synchronous words, the AIS is in a GMSK (Gaussian shift keying) modulation mode, and the PDT is in a 4FSK (frequency Shift keying) modulation mode; the channel machine unit has high-speed AD sampling capability, the baseband unit comprises a receiving unit and a transmitting unit, and the receiving unit executes the following operations:

firstly, an interphone channel unit receives wireless signals sent by other equipment in the air, converts the wireless signals into IQ signals sampled at a high speed and sends the IQ signals to a baseband unit;

secondly, the baseband unit extracts the characteristics of the wireless signals by using a digital signal processing method, compares the extracted information with the pre-stored waveform characteristics and judges the waveform mode;

if the PDT synchronous word is acquired through the synchronous word autocorrelation algorithm, the baseband unit processes and resamples the signal by using a PDT narrow-band parameter digital filter;

fourthly, the baseband unit analyzes the signal according to the PDT mode protocol format and analyzes the service information;

fifthly, if the AIS synchronous word is captured through the synchronous word autocorrelation algorithm, the baseband unit processes and resamples the signal by using a 25KHz bandwidth parameter digital filter;

sixthly, the baseband unit analyzes the signal according to the AIS mode protocol format and analyzes the service information;

displaying the service information through a display interface by the display unit;

the transmitting unit performs the following operations:

firstly, a user initiates voice, short message or help seeking service through a display unit, or equipment automatically initiates help seeking service information;

secondly, the base band unit judges whether the transmitting mode is a PDT mode or an AIS mode according to the setting and the service content;

if the PDT mode is adopted, the information is coded, processed and framed according to a PDT protocol;

fourthly, 4FSK high-speed rate modulation is carried out; then entering the seventh step;

fifthly, if the mode is the AIS mode, generating AIS information; processing and framing the generated information according to an AIS protocol;

sixthly, GMSK high-rate modulation is carried out;

seventhly, performing predistortion according to the amplitude-frequency characteristic of the channel;

eighthly, converting the signal into a high-speed modulation signal with a 120KHz sampling rate, and sending the signal to a two-point modulation control port of the channel machine;

and ninthly, the channel machine is controlled by the baseband unit, modulates the high-speed modulation signal to a carrier wave with a specified frequency and transmits the modulated signal.

2. A PDT interphone with integrated AIS codec capability as recited in claim 1, wherein the processing of the signal by the baseband unit using PDT narrowband parametric digital filters performs the following operations: judging the similarity of the current received signal and the stored synchronous words of the GMSK mode message and the PDT mode message, analyzing the waveform characteristics of the received signal, and respectively calculating the judgment probabilities of the PDT mode and the AIS mode; a normalized receiving probability threshold is arranged in the baseband unit, and if the decision probability of the PDT mode and the AIS mode is lower than the normalized receiving probability threshold, the state returns to a waiting state; if the PDT mode judgment probability is calculated to be higher than the normalized receiving probability threshold and higher than the AIS mode judgment probability, judging that the signal is in the PDT mode; and if the AIS mode judgment probability is calculated to be higher than the normalized receiving probability threshold and higher than the PDT mode judgment probability, judging that the signal is the AIS mode.

3. A PDT interphone with integrated AIS codec capability as claimed in claim 2, characterized in that after determining the signal mode, the baseband unit will perform the following operations: adjusting self parameters according to a channel machine and a modulation mode of a current code element, when a received signal is in a PDT mode, carrying out narrowband filtering on the received signal again, carrying out resampling and incoherent demodulation, extracting frame synchronization and bit synchronization information from a synchronization word, and carrying out subsequent PDT protocol processing; when the received signal is in an AIS mode, the received signal is subjected to double synchronization, a synchronization word is used for carrying out correlation peak operation to obtain an optimal sampling point 1, an integral code word is used for carrying out bit synchronization estimation to obtain an optimal sampling point 2, the optimal sampling point 1 is corrected by comparing the position difference of the two sampling points and referring to the optimal sampling point 2 to obtain an optimal sampling solution, and resampling, level judgment, demodulation and AIS protocol processing at a reduced rate are carried out according to the sampling point indicated by the optimal solution.

Technical Field

The invention relates to a digital interphone and an Automatic Identification System (AIS), in particular to a PDT interphone with integrated AIS coding and decoding capability, and particularly relates to a PDT interphone terminal at sea.

Background

In the field of offshore communication at present, AIS and interphone are common devices, AIS has extremely high use frequency in the aspects of offshore collision prevention, positioning, information communication and the like, and is generally used for discovery, interaction, management and help seeking between ships and land. Especially if people and articles falling into the water have AIS help seeking capability, the rescue probability can be greatly improved. The PDT interphone is a device which is used for near-distance communication of ships and fleets and has the characteristics of frequent use and convenience in carrying. PDT intercom and AIS use the frequency point to be close, but channel bandwidth, modulation mode, frame structure etc. have great difference, in the former equipment, often use a plurality of baseband even multichannel machine to reach the effect that same equipment possesses two functions, all have great disadvantages in the aspect of volume, power consumption, portability.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a PDT interphone with integrated AIS coding and decoding capabilities.

The technical scheme adopted by the invention is as follows: the PDT interphone with the integrated AIS coding and decoding capability is characterized by comprising an antenna, a channel unit, a baseband unit and a display unit, wherein the baseband unit adopts an integrated multiply-add unit and a DSP (digital signal processor) with a high-speed SSI (Small scale integration) communication interface as a core processing device and stores modulation of AIS mode messages and PDT mode messages under high-speed sampling and waveform characteristics of synchronous words, the AIS is in a GMSK (Gaussian shift keying) modulation mode, and the PDT is in a 4FSK (frequency Shift keying) modulation mode; the channel machine unit has high-speed AD sampling capability, the baseband unit comprises a receiving unit and a transmitting unit, and the receiving unit executes the following operations:

firstly, the interphone channel unit receives wireless signals sent by other equipment in the air, converts the wireless signals into IQ signals sampled at a high speed and sends the IQ signals to the baseband unit.

And secondly, the baseband unit extracts the characteristics of the wireless signals by using a digital signal processing method, compares the extracted information with the pre-stored waveform characteristics and judges the waveform mode.

And thirdly, if the PDT synchronous word is acquired through the synchronous word autocorrelation algorithm, the baseband unit processes and resamples the signal by using a PDT narrow-band parameter digital filter.

And fourthly, the baseband unit analyzes the signal according to the PDT mode protocol format and analyzes the service information.

And fifthly, if the AIS synchronous word is acquired through the synchronous word autocorrelation algorithm, the baseband unit processes and resamples the signal by using a 25KHz bandwidth parameter digital filter.

And sixthly, the baseband unit analyzes the signal according to the AIS mode protocol format and analyzes the service information.

And seventhly, the display unit presents the service information through a display interface.

The transmitting unit performs the following operations:

firstly, a user initiates voice, short message or help seeking service through a display unit, or equipment automatically initiates help seeking service information.

And secondly, the baseband unit judges whether the transmitting mode is a PDT mode or an AIS mode according to the setting and the service content.

And thirdly, if the PDT mode is adopted, the information is coded, processed according to the PDT protocol and framed.

Fourthly, 4FSK high-speed rate modulation is carried out; and then entering the seventh step.

Fifthly, if the mode is the AIS mode, generating AIS information; and processing and framing the generated information according to the AIS protocol.

And sixthly, carrying out GMSK high-rate modulation.

And seventhly, performing predistortion according to the amplitude-frequency characteristic of the channel.

Eighthly, converting the signal into a high-speed modulation signal with a 120KHz sampling rate, and sending the signal to a two-point modulation control port of the channel machine.

And ninthly, the channel machine is controlled by the baseband unit, modulates the high-speed modulation signal to a carrier wave with a specified frequency and transmits the modulated signal.

The baseband unit processes the signal by using a PDT narrow-band parameter digital filter to execute the following operations:

judging the similarity of the current received signal and the stored synchronous words of the GMSK mode message and the PDT mode message, analyzing the waveform characteristics of the received signal, and respectively calculating the judgment probabilities of the PDT mode and the AIS mode; a normalized receiving probability threshold is arranged in the baseband unit, and if the decision probability of the PDT mode and the AIS mode is lower than the normalized receiving probability threshold, the state returns to a waiting state; if the PDT mode judgment probability is calculated to be higher than the normalized receiving probability threshold and higher than the AIS mode judgment probability, judging that the signal is in the PDT mode; and if the AIS mode judgment probability is calculated to be higher than the normalized receiving probability threshold and higher than the PDT mode judgment probability, judging that the signal is the AIS mode.

After determining the signal mode, the baseband unit will perform the following operations: adjusting self parameters according to a channel machine and a modulation mode of a current code element, when a received signal is in a PDT mode, carrying out narrowband filtering on the received signal again, carrying out resampling and incoherent demodulation, extracting frame synchronization and bit synchronization information from a synchronization word, and carrying out subsequent PDT protocol processing; when the received signal is in an AIS mode, the received signal is subjected to double synchronization, a synchronization word is used for carrying out correlation peak operation to obtain an optimal sampling point 1, an integral code word is used for carrying out bit synchronization estimation to obtain an optimal sampling point 2, the optimal sampling point 1 is corrected by comparing the position difference of the two sampling points and referring to the optimal sampling point 2 to obtain an optimal sampling solution, and resampling, level judgment, demodulation and AIS protocol processing at a reduced rate are carried out according to the sampling point indicated by the optimal solution.

The beneficial effects produced by the invention are as follows: the interphone can use the same channel machine and the base band unit to be compatible with the PDT and AIS modes, portability of equipment with two systems is greatly improved, standby time is effectively prolonged, and maritime work personnel can conveniently carry equipment to communicate with the PDT or use AIS messages to call for help.

The invention uses the same channel machine unit and the baseband unit to automatically identify the signal mode, and the user can receive the services of the two modes without manual switching, thereby greatly liberating the two hands of the user, leading the user to be more concentrated on the field operation and more simply initiating help seeking.

Drawings

FIG. 1 is a block diagram of the hardware components of the present invention;

FIG. 2 is a software composition block diagram of the present invention;

FIG. 3 is a communication schematic of the present invention;

FIG. 4 is a flow chart of the device reception operation of the present invention;

fig. 5 is a transmission workflow diagram of the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples.

As shown in fig. 1, the device hardware is composed of an antenna, a channel unit, a baseband unit and a display unit; the antenna is used for receiving and transmitting radio frequency signals, the channel machine has high-speed sampling capacity and processes the radio frequency signals into baseband signals, the baseband units store waveform characteristics of synchronous words of AIS mode messages and PDT mode messages under high-speed sampling and a predistortion algorithm aiming at the channel machine, and the same channel machine can receive and transmit GMSK modulation messages in the AIS mode and 4FSK modulation messages in the PDT mode; typically, an IQ signal with a sampling rate of 96KHz, is also responsible for modulating the baseband signal of the transmit path to a carrier, generating a radio frequency signal. The baseband unit is used for signal processing and protocol processing. The display unit is used for playing audio and displaying short messages and other services to the client, and the user can configure equipment parameters, such as a current frequency point and the like, through the display unit. The display unit comprises a liquid crystal, a key, a loudspeaker and a microphone, a user can operate the display unit to initiate or reply a service, and the display unit internally comprises a water immersion sensor and can automatically identify and send distress information after people fall into water. The accessories such as the battery contained in the device are omitted from figure 1.

As shown in fig. 2, the device software consists of waveform decision, IQ demodulation, PDT protocol stack (receive and transmit), AIS protocol stack (receive and transmit), display interface. The PDT protocol stack receiving part comprises 4FSK demodulation, synchronization, channel decoding and PDT protocol processing; the AIS protocol stack receiving part comprises GMSK demodulation, channel decoding and AIS protocol processing; the PDT protocol stack transmitting part comprises 4FSK modulation, channel coding and PDT protocol processing; the AIS protocol stack transmitting part comprises GMSK modulation, channel coding and AIS protocol processing. The waveform decision provides basis for IQ demodulation mainly according to the waveform decision mode. IQ demodulation receives a judgment result transmitted by waveform judgment, 4FSK or GMSK signal demodulation is carried out on IQ signals, specific work comprises baseband signal extraction, sampling rate conversion and judgment, and a PDT mode protocol stack is responsible for transmitting and receiving signals according to a PDT protocol; the AIS mode protocol stack is responsible for receiving and transmitting signals according to an AIS protocol. And the display interface is used for receiving the service and displaying the service to the user. The user may also operate the display interface to configure current channel information and for initiating a service.

As shown in fig. 3, the device may set the operating frequency point. Can carry out pronunciation and SMS communication with the PDT intercom of having the frequency point on the frequency point of work, also can receive the AIS message that AIS berth and AIS bank transmitted on the frequency point of work, after personnel emergence emergency, the equipment can transmit PDT mode distress message or pronunciation contact this on-board personnel to seek help, also can transmit AIS message, seeks help to the berth or the AIS bank of other boats and ships installation.

The invention comprises four key points: the first key point is that the same channel machine obtains an air interface signal waveform through high-speed sampling; the second key point is that the baseband unit compares data obtained by high-speed sampling with the synchronous feature code to obtain a mode decision result, and re-samples signals according to the decision result and selects different protocol stack flows for processing; the third key point is that the same display interface is used for presenting the user, so that the consistency of the user operation is ensured; the fourth key point is that signals of different modes of a baseband form a uniform modulation signal waveform format through high-speed modulation and predistortion, and are modulated and transmitted through a channel machine.

The specific working scene and flow of the equipment are as follows:

1. the equipment is internally preset with a channel frequency point and an AIS default frequency point participating in calling, wherein the AIS default frequency point is only used for AIS mode help-seeking emission, and a working mode can be preset for manual AIS help-seeking or automatic help-seeking in water.

2. After the device is turned on, the device waits at the frequency point of the channel participating in the call, monitors signals sent by other interphones or AIS devices, and enters the receiving process shown in FIG. 4 if the signals are received. When other PDT interphones transmit voice, the equipment receives and analyzes the signal, a PDT synchronous word similar waveform is detected in the signal, the modulation air interface characteristic is a 30ms period, the transmission width is 27.5ms, the bandwidth is 12.5k Hz, the modulation waveform is positioned in the middle of a power burst window, four judgment points can be detected outside a synchronous autocorrelation area by the modulation waveform, after the characteristics are weighted and calculated, the judgment probability of a PDT mode is higher than a normalized receiving probability threshold and higher than an AIS judgment probability, the waveform is judged to be PDT service, after resampling, the PDT protocol stack is used for analyzing and decoding, and voice is played to a client; when other PDT interphones transmit short messages, the equipment receives and analyzes the short messages, and displays the short messages to users through liquid crystal through the same judgment process and protocol processing process. When other equipment transmits AIS information, the equipment judges that the signal and AIS synchronous word autocorrelation exceeds a threshold after receiving and analyzing, the synchronous word is positioned at the front end of a power burst window, the transmitting window of the synchronous word is less than 27ms or more than 50ms, the bandwidth is 25K Hz, two judgment points are detected outside a synchronous area, after the weighted calculation of the characteristics, the AIS mode judgment probability is higher than a normalized receiving probability threshold and higher than a PDT judgment probability, the AIS information is judged according to a rule, and the AIS position information is buffered by a display unit. When the user presses a key to inquire, the information can be seen. When the AIS or PDT help-seeking message is received, the interphone gives out a sound alarm to prompt a customer to pay attention.

3. When the user presses the key to initiate PDT voice or short message service, the voice service or short message service is initiated according to the flow in fig. 5.

4. When the user falls into the water or the ship loses the communication capability in danger, if the equipment is preset to automatically call for help when falling into the water, the equipment automatically initiates help according to the flow in the figure 5, the help can be preset to transmit PDT (portable data management) short messages or AIS (automatic identification system) emergency messages, the PDT short messages are transmitted to the channel frequency points participating in the call, and the AIS emergency messages are sequentially transmitted to the channel frequency points participating in the call and the AIS default frequency points. The user may also manually operate the device to transmit a help message.

As shown in fig. 4, the specific receiving flow of the device is as follows:

(1) the interphone channel unit receives wireless signals sent by other equipment in the air, converts the wireless signals into IQ signals sampled at a high speed and transmits the IQ signals to the baseband unit;

(2) the baseband unit judges the waveform mode;

(3) judging the signal characteristic to exceed and judge the threshold, have caught PDT synchronous word through the autocorrelation algorithm of synchronous word, what is received is PDT message;

(4) the baseband unit processes and resamples the signal by using a PDT narrow-band parameter digital filter;

(5) the baseband unit analyzes the signal according to the PDT mode service and analyzes service information;

(6) the display interface presents the service (short message or voice);

(7) the reception is completed.

If the baseband unit judges that the synchronization word autocorrelation algorithm captures the AIS synchronization word in the step (3) and the AIS message is received, the following processing is carried out:

(1) the baseband unit processes and resamples signals by using a 25KHz bandwidth parameter digital filter;

(2) the baseband unit analyzes the signal according to the GMSK protocol service format and analyzes the service information;

(3) the display interface presents the position information and the help-seeking prompt of the ship nearby or in the same team;

(4) and ending the service.

As shown in fig. 5, the specific transmission flow of the device is as follows:

(1) a user operates the display unit to initiate a service or equipment triggers automatic help seeking when falling into water;

(2) judging a use mode according to user operation and setting;

(3) judging whether the message is a PDT message;

(4) if the message is PDT message, the sound and message coding is carried out;

(5) framing and protocol processing according to a PDT protocol;

(6) 4FSK high-rate modulation is carried out;

(7) carrying out predistortion according to the characteristics of a channel machine;

(8) transmitting a 120K Hz signal to a channel machine for two-point modulation;

(9) the channel machine is controlled to modulate the 120KHz signal to the carrier and transmit.

If the AIS message is judged in the step (3), generating information according to operation or triggering conditions such as drowning, and performing the following processing:

(1) processing AIS protocol and framing;

(2) GMSK high-rate modulation is carried out on the message;

(3) carrying out predistortion according to the amplitude-frequency characteristics of a channel machine;

(4) transmitting a 120K Hz sampling rate signal to a channel machine for two-point modulation;

(5) the channel machine is controlled to modulate the 120KHz signal to the carrier and transmit.

The user configures the channel and working mode participating in the call through the display unit, and controls the channel machine to wait in the designated channel; after receiving the waveform of the air interface signal, the channel unit converts the waveform into an IQ signal through AD high-speed sampling with the rate of more than or equal to 96 KHz; the baseband unit obtains the similarity probability of the current message and the two modes by comparing the waveform characteristics under the condition of not distinguishing the modulation mode through a digital signal processing method, and judges the mode of receiving the radio frequency signal by comparing the waveform judgment probability; the baseband unit resamples signals according to a mode, adjusts filter parameters and demodulation processes through software, and calls a corresponding protocol stack to perform demodulation and channel decoding processing; the received services are displayed to the user through the display unit.

The equipment acquires more signal information through high-speed sampling without analyzing the specific content and format of the waveform of the air interface signal, extracts the symbol rate of the signal through a digital signal processing mode, and the characteristics of the waveform, the correlation degree, the period, the rate, the signal modulation order and the like of the synchronization signal, calculates the similarity of the built-in waveform, obtains the decision probability, judges the signal to be in a PDT mode or an AIS mode through comparing the probability with a normalized receiving probability threshold, and resamples the signal to an appropriate rate for processing.