CN102611662A - Underwater acoustic modem with low cost and low power consumption - Google Patents
Underwater acoustic modem with low cost and low power consumption Download PDFInfo
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- CN102611662A CN102611662A CN2012100320886A CN201210032088A CN102611662A CN 102611662 A CN102611662 A CN 102611662A CN 2012100320886 A CN2012100320886 A CN 2012100320886A CN 201210032088 A CN201210032088 A CN 201210032088A CN 102611662 A CN102611662 A CN 102611662A
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Abstract
The invention discloses an underwater acoustic modem with low cost and low power consumption, aiming at realizing effective underwater communication in a certain distance range, wherein a single chip MSP430F149 with ultra-low power consumption is taken as the processing core, and an RS-232 interface is used to communicate with a computer; a 3.3 V battery is adopted to supply power by a complete machine, a transceiving integrated transducer for underwater ranging, which is cheap and can be in volume production in the market is used as an ultrasonic transmitting and receiving device, the design scheme of low power consumption and a 2ASK modulation and demodulation way are adopted to all hardware. The maxim power consumption of the complete machine is 90 mW, the transmission rate of the data is 2kbps, the longest and effective communication distance is 22 m; the underwater acoustic modem can be connected with various kinds of digital sensors and has the characteristics of low cost and low power consumption, so that the underwater acoustic modem is suitable to be used as a sensing node of an underwater acoustic sensor network. The underwater acoustic modem can continuously work underwater for more than half a year and can perform reliable underwater communication operation for a long time.
Description
Technical field
The invention belongs to the water sound communication technique field, relate to a kind of underwater sound modulator-demodulator of low-cost low-power consumption.
Background technology
Traditional underwater sound modulator-demodulator volume is big, involve great expense, power consumption is higher; Communication distance can reach several kilometers even tens kilometers; But in recent years, people have proposed the notion of underwater sound sensing net, and traditional underwater sound modulator-demodulator does not accommodate the instructions for use of underwater sound sensing net; Underwater sound sensing net is set up by many sensing nodes and is formed; Have intensive, the sweeping characteristics of node,, be necessary very much to develop and a kind ofly have that volume is little, low-cost, the efficient underwater sound modulator-demodulator of low-power consumption for whole cost, the assurance sensing net that reduces underwater sound sensing net carries out reliably for a long time that underwater information is collected and transmit.Recent years; There has been research institution to develop low-power consumption, underwater sound modulator-demodulator cheaply; But the data transmission bauds of these modulator-demodulators is very slow; Can not supporting dielectric MAC layer (Medium Access Control:MAC) when communicating by letter under water and the agreement of route layer carry out transfer of data, so can not be as the node of underwater sensing net.Under the low power consumption of trying one's best, realize the information transmitting range of trying one's best far away, just require underwater sound modulator-demodulator to have very high efficient.
Factors such as the underwater acoustic channel of marine environment is one when extremely complicated, sky, becomes multi-path channel at random frequently, and high ambient noise, narrow bandwidth, low carrier frequency, transmission delay be big have simultaneously restricted the speed of transfer of data.Realize the application of underwater sound transmission, need to solve following problem.At first, sound wave can weaken (amplitude fading) gradually in transport process, and it is suddenly big or suddenly small promptly to receive signal, and this is different relevant formation of phase place when arriving receiver owing to the signal along each approach.Be transmitted in certain frequency interval according to the underwater sound, the correlation of its decline is the characteristic of remarkable attenuating, can take to reduce transmission frequency and the method that adopts frequency diversity to handle, but its cost is to have lost band resource.Next is the intersymbol interference problem.Because the velocity of sound of seawater has only 1500m/s, the reception signal of prosign is distributed in pectinate texture on the time shaft of broad, and the relative time delay difference is bigger between each footpath.If what propagate is pulse train very close to each other, it is overlapping that multipath will cause the reception signal that different code elements take place, and brings difficulty to judgement.The method that solves is in pulse train, adds the time synchronized pulse, under its guiding, representes with different frequencies with the pulse of emission constantly, makes different reception signal frequencies constantly confirm.Like this, even if the interference code that has some multipaths to form mixes repeatedly with it, also having with the frequency is the method that criterion is extracted signal, and promptly the frequency hopping anti-multipath disturbs.Take the frequency hopping mode in the spread spectrum in the underwater sound communication, according to lock-out pulse, step-by-step comes detection signal according to given frequency, can solve multipath effectively and disturb the intersymbol interference that causes.Another problem is that underwater sound message transmission rate is lower; Improve transmission rate; Mainly solve through the research acoustic modem; Common way is to adopt modes such as 16 system frequency shift keyings (MFSK), double frequency diversity and spread-spectrum, and domestic research has in this respect obtained bigger progress.In view of the design principle of low-power consumption, the modulation demodulation system of 2ASK is compared other modes has lower power consumption.
From the relatively more relevant 2ASK demodulation of angle of the error rate and the performance of incoherent 2ASK demodulation.The average energy of each is:
The amplitude of A expression signal in the formula, T
bRepresent the time that each is lasting.Therefore, for relevant 2ASK demodulation mode, each probability of errors P
E-coFor:
D in the formula
MinRepresent minimum character spacing, σ representes standard deviation, N
0Expression interchannel noise density, Q (z) expression Q function.
For incoherent 2ASK demodulation mode, each probability of errors P
E-coFor:
Can find out under identical signal to noise ratio condition that by (2) formula and (3) formula relevant 2ASK demodulation has the lower error rate than incoherent 2ASK demodulation.
Summary of the invention
For solve in the prior art underwater sound modulator-demodulator volume big, involve great expense, power consumption is higher; Error rate problem of higher the invention provides a kind of underwater sound modulator-demodulator of low-cost low-power consumption, and this underwater sound modulator-demodulator cost is low, power consumption is little; Efficient is high; The sensing node that is suitable as underwater sound sensing net uses, and more than continuous operation half a year, carries out reliable subsurface communication operation for a long time under water.
In order to address the above problem, the technical scheme that the present invention taked is:
A kind of underwater sound modulator-demodulator of low-cost low-power consumption is characterized in that: comprising:
One is used to launch hyperacoustic transmitting transducer,
One is used to receive the ultrasonic reception transducer,
Be used for the voltage amplification of modulated signal and connect the first signal amplification appliance of transmitting transducer,
The secondary signal amplification appliance that links to each other with receiving transducer and the signal that receives is carried out voltage amplification,
Be used for stablizing the secondary signal amplification appliance and receive the phase place of signal and the phase-locked loop circuit that carries out coherent demodulation,
The microprocessor that is connected with the first signal amplification appliance with phase-locked loop circuit,
Be used to connect the serial communication interface of microprocessor and outer computer.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: the centre frequency of said transmitting transducer is 40kHz, and the centre frequency of said receiving transducer is 40kHz.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: the said first signal amplification appliance adopts the MAX3232 chip that the modulated signal of telecommunication is carried out voltage amplification, to drive transmitting transducer emission ultrasonic wave.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: the said first signal amplification appliance adopts the OP07 chip, links to each other with receiving transducer, and the signal that receives is carried out voltage amplification.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: said phase-locked loop circuit adopts the LMC568 chip, is used for stable reception signal and carries out coherent demodulation.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: said microprocessor adopts the MSP430F149 single-chip microcomputer, data are encoded, are decoded, and carry out Frame packing, unpack.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: said MSP430F149 single-chip microcomputer adopts the 2ASK modulation demodulation system.
The underwater sound modulator-demodulator of aforesaid a kind of low-cost low-power consumption is characterized in that: said serial communication interface adopts the serial line interface of rs-232 standard, is used for MSP430F149 single-chip microcomputer and compunication, carries out exchanges data.
The invention has the beneficial effects as follows: system of the present invention has farthest reduced the usage quantity of hardware in global design, aspect modulation-demodulation technique, has accomplished " hard with soft generation ", and transducer is selected the small-sized waterproof transceiver transducer on the market for use.Whole modem system is encapsulated in the plastic casing that waterproof is good, seal is strong, guarantees system's reliable and stable long-time running.
Description of drawings
Fig. 1 is the underwater sound modem structure sketch map of the low-cost low-power consumption of the present invention.
Embodiment
Below in conjunction with accompanying drawing the present invention is further described.
At first underwater sound modulator-demodulator 1 is put into water, and link to each other through serial ports 8 with computer.As shown in Figure 1, underwater sound modulator-demodulator 1 places under water fully, and is connected with computer through serial ports 8.Computer passes through serial ports to sending data with underwater sound modulator-demodulator 1; Data are sent in the microprocessor 7 through serial ports 8; Microprocessor 7 reason devices deposit data in buffering area earlier, again it are carried out the packing data framing, encode then; Again 0,1 data are expressed as the form of the signal of telecommunication, after promptly modulating.The treated device of the signal of telecommunication after the modulation produces, and is sent to signal amplifier 4, and signal amplifier 4 amplifies voltage of signals, drives coupled transmitting transducer 2, and transmitting transducer 2 is converted into ultrasonic wave with signal and in water, launches.After the receiving transducer 3 of underwater sound modulator-demodulator 1 receives the ultrasonic wave in the water, acoustic signals is converted into the faint signal of telecommunication, the signal of telecommunication is sent into the signal amplifier 5 that is attached thereto; Signal is sent into phase-locked loop circuit 6 after amplifying, make that the signal phase that receives is stable; And the 2ASK demodulation that is concerned with, the signal after the demodulation is sent in the microprocessor 7, and microprocessor 7 is with data decode; The restoring data frame; Carry out Frame and unpack, the reduction of data of transmitting terminal emission the most at last, and data are sent into computer through serial ports 8.Arrive this, computer has been accomplished communication process one time through the underwater sound modulator-demodulator of this low-cost low-power consumption.The communication mode of modulator-demodulator is full-duplex communication.
The present invention is from the choosing of underwater acoustic transducer, design that hardware and software has carried out low-cost low-power consumption.Underwater sound modulator-demodulator is made up of three parts, transmitting section, receiving unit and underwater acoustic transducer.For the validity of checking underwater sound modulator-demodulator, must build a rational and effective platform, platform comprises PC (Personal Computer:PC), sensing node and underwater sound modulator-demodulator.Information sends modulator-demodulator by PC to through the RS-232 serial ports; The inner MCU of modulator-demodulator is through binary system amplitude shift keying (the Binary Amplitude Shift Keying:2ASK) signal of telecommunication of coding back output 40kHz; The signal of telecommunication inserts transducer behind signal amplification circuit, transducer resonance produces ultrasonic wave at water transmission; At receiving terminal, transducer receives ultrasonic signal and is converted into the signal of telecommunication, and the signal of telecommunication is sent back to little through amplification and phase-locked loop
Control unit(Micro Control Unit:MCU), data are decoded in MCU, and PC is passed to through serial ports in the reduction back.
Be to realize the purpose of low-power consumption, whole modem system adopts direct current 3.3V power supply, therefore on the selection of chip and scheme determination, must can satisfy the requirement that 3.3V supplies power, underwater sound modulation scheme comprise amplitude shift keying 2ASK and
Phase shift keying(phase shift keying:PSK) mode; According to existing experimental result, the modulation system of 2ASK is compared the PSK mode can practice thrift a part of electric energy, secondly; The PSK mode often needs higher driving voltage, uses the 2ASK mode can simplify the complete machine power source design.
Underwater sound modulator-demodulator of the present invention is relatively stricter to the requirement of power consumption, and the power consumption of microprocessor 7 is maximum in whole system, and therefore selecting suitable low-power consumption microprocessor 7 for use is vital for reducing Overall Power Consumption.The MSP430 series monolithic is the U.S.
Texas InstrumentThe super low power consuming single chip processor that company produces, what the supply voltage of MSP430 series monolithic adopted is 1.8-3.6V voltage.Two different clock systems are arranged: fundamental clock system, FLL (FLL and FLL+) clock system and DCO digital oscillator clock system in MSP430 series.Can only use a crystal oscillator (32768Hz), also can use two crystal oscillators.Produce central processing unit (Central by the system clock system
Processing Unit: CPU) with the required clock of each function.And a little clocks can open and close under the control of instruction, thereby realize the control to overall power consumption.Because the functional module of opening during system's operation is different, promptly adopts the different working pattern, the power consumption of chip has significant difference.Total a kind of activity pattern (AM) and five kinds of low-power consumption modes (LPM0-LPM4) in system.Under the real-time clock pattern, can reach 2.5 μ A, under RAM maintenance pattern, the minimum 0.1 μ A that reaches.
The 40kHz signal voltage that is gone out by single-chip simulation is 3.3V; And the I/O mouth driving force of MSP430 single-chip microcomputer is very low; Therefore can not directly drive underwater acoustic transducer, must adopt signal amplification circuit in the system, but integrated in the market signal amplification IC does not adopt the 3.3V power supply.Consider that the principle that can use level conversion improves driving force; System adopts the MAX3232 of 3.3V power supply as amplifying chip; MAX3232 adopts proprietary low pressure differential transmitter output stage, utilizes dual charge pump when 3.0V to 5.5V power supply is supplied power, can realize real RS-232 performance.Device only needs the outside small size charge pump electric capacity of four 0.1 μ F.MAX3232 guarantees under the 120kbps data rate, to keep the RS-232 output level.Can guarantee the data rate of 250kbps under the normal mode of operation, chip can drive transducer for the high voltage signal of+12V and-12V with the 3.3V conversion of signals, thereby reaches the purpose that signal amplifies.
The receiving unit of underwater sound modulator-demodulator is made up of four parts: signal amplifier, gain controller, phase-locked loop (phase-locked loop:PLL) and inverter.The circuit of these parts must all use the 3.3V power supply.Phase-locked loop by
Phase discriminator,
Loop filterWith
Voltage-controlled shaking Swing deviceForm.Phase discriminator is used for differentiating
Input signalUi with
The output signalBetween the Uo
Phase place Difference, and output error
VoltageUd.Among the Ud
NoiseWith
DisturbComposition is by the loop of low pass character
FilterFiltering, the control voltage U c of formation voltage controlled oscillator (VCO).The result that Uc acts on voltage controlled oscillator is vibrated its output
FrequencyFo pulls to loop input signal frequency f i, and when the two was equal, loop was locked, and was called into lock.The direct-current control voltage of keeping locking is provided by phase discriminator, so leaves certain phase difference between two input signals of phase discriminator.Behind small-signal process amplifier and the phase-locked loop, phase place obtains revising, and this moment, signal phase and input were opposite, and inversion signal has been reduced into primary signal through inverter circuit and has sent MCU to.In the entire circuit the most the difficulty be the design and use of PLL; Consider the low power capabilities of complete machine, final scheme confirms to use integrated phase lock chip LMC568, and this is a low-power consumption phase-locked loop IC; Comprised Voltage-Controlled oscillation circuit, LMCMOS phase discriminator and load detecting output.LMC568 uses the 3.3V power supply, can export restituted signal.Insert Voltage-Controlled oscillation circuit between 5 pin of LMC568 and 6 pin, its frequency of oscillation must be the twice of signal frequency.In the modulator-demodulator of these works, the frequency range of signal is 39kHz～41kHz, and the pressuring controlling oscillator frequency that therefore inserts is necessary for 78kHz～82kHz, for reaching this purpose, in circuit design, has used potentiometer to come regulating frequency.
Communication data between the underwater sound modulator-demodulator is to be accomplished by the transmission of packet, therefore must between reflector and receiver, set up communication protocol.This packet can be easily by the software editing that moves on the modulator-demodulator, thereby flexibility is provided for the test of each item index parameter.In this modulator-demodulator, packet consists of the following components, and comprises two signs, valid data head, valid data body and cyclic redundancy items.Wherein two signs are as the head of underwater sound communication data flow, and the valid data head is the beginning of mac-layer protocol in the underwater sound communication agreement, comprising the sequence number of the length of valid data, unnecessary data bit, acknowledge character and data.
In the design of protocol of underwater sound modulator-demodulator, Data Labels uses a string sequence of binary digits clocklike 11011011, indicates the beginning and end of entire stream with it.When demodulator detect the sign length is 1 byte, and the sign first bit digital be 1 o'clock, just learn and import demodulator into having a packet.So; This sign is to be used for letting between modulator and the demodulator synchronously, produces an interruption when making demodulator read packet information on the horizon, and the MCU that has no progeny in the entering carries out continuous data and reads; Behind the ending sign that detects packet, jump out interruption, carry out data processing.Valid data length is that unit deposits in the corresponding position of packet with the byte, and its size is directly determined by the size of the valid data that reality is packed.Unnecessary data bit is to be used for the ending of flag data stream, if the value of redundant data position is 1, the expression data flow does not finish, and modulator continues to send data, if reading the redundant data position becomes 1, modulator then stops to send.Acknowledge character is the data of 1 position, is used for distinguishing the beginning of valid data main body and packet.Data sequence number is that length is 6 data, the sequence of expression place packet in entire stream.Cyclic redundancy item in the packet is used for the detected transmission mistake, and in actual use, adopting length is the cyclic redundancy sequence of 2 bytes, and sequence is taken from the CRC16 table.
More than show and described basic principle of the present invention, principal character and advantage.The technical staff of the industry should understand; The present invention is not restricted to the described embodiments; That describes in the foregoing description and the specification just explains principle of the present invention; Under the prerequisite that does not break away from spirit and scope of the invention, the present invention also has various changes and modifications, and these variations and improvement all fall in the scope of the invention that requires protection.The present invention requires protection range to be defined by appending claims and equivalent thereof.
Claims (8)
1. the underwater sound modulator-demodulator of a low-cost low-power consumption is characterized in that: comprising:
One is used to launch hyperacoustic transmitting transducer,
One is used to receive the ultrasonic reception transducer,
Be used for the voltage amplification of modulated signal and connect the first signal amplification appliance of transmitting transducer,
The secondary signal amplification appliance that links to each other with receiving transducer and the signal that receives is carried out voltage amplification,
Be used for stablizing the secondary signal amplification appliance and receive the phase place of signal and the phase-locked loop circuit that carries out coherent demodulation,
The microprocessor that is connected with the first signal amplification appliance with phase-locked loop circuit,
Be used to connect the serial communication interface of microprocessor and outer computer.
2. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 1, it is characterized in that: the centre frequency of said transmitting transducer is 40kHz, the centre frequency of said receiving transducer is 40kHz.
3. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 2 is characterized in that: the said first signal amplification appliance adopts the MAX3232 chip that the modulated signal of telecommunication is carried out voltage amplification, to drive transmitting transducer emission ultrasonic wave.
4. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 2 is characterized in that: the said first signal amplification appliance adopts the OP07 chip, links to each other with receiving transducer, and the signal that receives is carried out voltage amplification.
5. according to the underwater sound modulator-demodulator of claim 3 or 4 described a kind of low-cost low-power consumption, it is characterized in that: said phase-locked loop circuit adopts the LMC568 chip, is used for stable reception signal and carries out coherent demodulation.
6. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 5 is characterized in that: said microprocessor adopts the MSP430F149 single-chip microcomputer, data are encoded, are decoded, and carry out Frame packing, unpack.
7. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 6 is characterized in that: said MSP430F149 single-chip microcomputer employing 2ASK modulation demodulation system.
8. the underwater sound modulator-demodulator of a kind of low-cost low-power consumption according to claim 7 is characterized in that: said serial communication interface adopts the serial line interface of rs-232 standard, is used for MSP430F149 single-chip microcomputer and compunication, carries out exchanges data.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102820933A (en) * | 2012-08-21 | 2012-12-12 | 河海大学常州校区 | Underwater sound MODEM (modulator-demodulator) for underwater interphone |
| CN102914798A (en) * | 2012-09-27 | 2013-02-06 | 中国科学院地质与地球物理研究所 | Real-time transmission multifunctional ocean bottom seismograph |
| CN103048330A (en) * | 2012-12-18 | 2013-04-17 | 河海大学常州校区 | Visual detecting device for surface crack of underwater structure |
| CN106506418A (en) * | 2016-10-13 | 2017-03-15 | 河海大学常州校区 | Wideband 2ASK signal generating circuits in cognitive underwater sound communication |
| CN107085933A (en) * | 2017-05-04 | 2017-08-22 | 中国石油集团渤海钻探工程有限公司 | A kind of low-power consumption pit shaft underwater sound wave communication control system and its control method |
| CN107645311A (en) * | 2017-09-26 | 2018-01-30 | 天津光电通信技术有限公司 | One kind is with underwater sound sensing multi-node system |
| CN111624609A (en) * | 2020-06-05 | 2020-09-04 | 南京英锐创电子科技有限公司 | Ultrasonic ranging method and device |
| CN113596968A (en) * | 2021-07-22 | 2021-11-02 | 浙江大学 | Control method for realizing low power consumption based on underwater sound modem working mode switching |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102820933A (en) * | 2012-08-21 | 2012-12-12 | 河海大学常州校区 | Underwater sound MODEM (modulator-demodulator) for underwater interphone |
| CN102914798A (en) * | 2012-09-27 | 2013-02-06 | 中国科学院地质与地球物理研究所 | Real-time transmission multifunctional ocean bottom seismograph |
| CN103048330A (en) * | 2012-12-18 | 2013-04-17 | 河海大学常州校区 | Visual detecting device for surface crack of underwater structure |
| CN103048330B (en) * | 2012-12-18 | 2015-12-23 | 河海大学常州校区 | The visual sniffer of a kind of surface crack of underwater structure |
| CN106506418A (en) * | 2016-10-13 | 2017-03-15 | 河海大学常州校区 | Wideband 2ASK signal generating circuits in cognitive underwater sound communication |
| CN107085933A (en) * | 2017-05-04 | 2017-08-22 | 中国石油集团渤海钻探工程有限公司 | A kind of low-power consumption pit shaft underwater sound wave communication control system and its control method |
| CN107085933B (en) * | 2017-05-04 | 2023-12-22 | 中国石油天然气集团有限公司 | Low-power-consumption wellbore water acoustic wave communication control system and control method thereof |
| CN107645311A (en) * | 2017-09-26 | 2018-01-30 | 天津光电通信技术有限公司 | One kind is with underwater sound sensing multi-node system |
| CN111624609A (en) * | 2020-06-05 | 2020-09-04 | 南京英锐创电子科技有限公司 | Ultrasonic ranging method and device |
| CN113596968A (en) * | 2021-07-22 | 2021-11-02 | 浙江大学 | Control method for realizing low power consumption based on underwater sound modem working mode switching |
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Application publication date: 20120725 |