CN202772879U - Multiband DS-MFSK modem - Google Patents
Multiband DS-MFSK modem Download PDFInfo
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- CN202772879U CN202772879U CN 201220455280 CN201220455280U CN202772879U CN 202772879 U CN202772879 U CN 202772879U CN 201220455280 CN201220455280 CN 201220455280 CN 201220455280 U CN201220455280 U CN 201220455280U CN 202772879 U CN202772879 U CN 202772879U
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Abstract
Disclosed is a multiband DS-MFSK modem, belonging to the underwater acoustic technology field. To be specific, the utility model discloses an underwater acoustic communication modem that realizes multi-user communication by adopting direct sequence spread spectrum scrambling based on MFSK modulation and demodulation. The multiband DS-MFSK modem is characterized in that the modulation terminal divides the system frequency band into a plurality of sub-bands, with each sub-band adopting MFSK modulation to utilize different pseudo random sequence to carry out scrambling transmission of the communication signals, thus to realize multi-user address distribution. After realizing signal synchronization, the demodulation terminal utilizes its own pseudo random sequence code for descrambling and then utilizes the FFT method to realize the rapid demodulation of the information. The validity and stability of the structure can be verified by processing the experiment data. Meanwhile, in terms of realization difficulty, cost, and other factors, the structure can be effectively applicable to engineering realization.
Description
Technical field
The utility model relates to the underwater sound communication field, or rather, relate to a kind of underwater sound communication modulator-demodulator based on multiband DS-MFSK, be applicable in traffic rate is higher, robustness the is stronger underwater sound communication environment.
Background technology
In recent years along with the increase of human Activities of Ocean, the fields such as exploration of ocean resources, underwater operation, marine environmental monitoring all to transfer of data with communicate by letter very strong demand, and be to rely on underwater sound communication without the cable information interaction under water, so water sound communication technique becomes study hotspot gradually.In different application scenarios, the researcher has proposed the various communication technologys.
Multicarrier frequency shift keying (MFSK) is a kind of incoherent modulation technique, and it is modulated at parallel transmission the behind the different carrier with parallel information, but the traffic rate of Effective Raise system.Than the coherent modulation/demodulation technology, the MFSK modulator-demodulator does not need to carry out carrier synchronization at receiving terminal, when communicating by letter in the stronger underwater acoustic channel of time variation, can avoid the difficult problem of carrier synchronization difficulty.Simultaneously the MFSK modulation-demodulation technique belongs to the wide-band modulation demodulation techniques, when transmitting in frequency domain is the many ways of the underwater sound channels of comb filter, can resist multi-path effect from frequency domain.Adopt the MFSK modulation-demodulation technique can greatly simplify the complexity of communication control processor.
Direct sequence spread spectrum skill utilizes the correlation properties of pseudo random sequence, can effectively reduce noise effect and other users and disturb, so direct sequence spread spectrum communication system has stronger antijamming capability, can steadily and surely work under low signal-to-noise ratio.Can realize code division multiple access based on pseudo random sequence in addition, in radio communication, have widely and use.
The utility model based on the MFSK modulation technique in conjunction with direct sequence spread spectrum skill, with the two combination proposed a kind of can the low-cost convenient multiband DS MFSK underwater sound communication modulator-demodulator of realizing.
Summary of the invention
Given this, the utility model discloses a kind of multiband DS-MFSK modulator-demodulator, wherein modulator is comprised of the channel encoder (101), deserializer (102), sub-band frequency mapper (103,104,105), code element former (106), signal frame former (108) and the radiating circuit (109) that link to each other successively, and code element former (106) also links to each other with pseudo-random sequence generator (107) simultaneously; Demodulator is comprised of signal receiving circuit (110), frame synchronizer (111), code element interceptor (112), PN code descrambling and the decision device (113), FFT converter (114), frequency spectrum soft decision information demodulator (115), parallel-to-serial converter (116), the channel decoder (117) that link to each other successively.
The course of work of its modulator of multiband DS-MFSK modulator-demodulator disclosed in the utility model is: gone here and there by deserializer (102) after the serial information that information source sends is encoded by channel encoder (101) again and change, and adopt the reflection method of tabling look-up that information is mapped on the different carrier in the sub-band by sub-band frequency mapper (103,104,105), and with the parallel stack of different frequency bands carrier wave, thereby after realizing the MFSK modulation of multiband, and the signal after will modulating is sent into code element former (106).Modulation intelligence and pseudo-random sequence generator (107) pseudo noise code that produce of code element former (106) after with a plurality of sub-band additions carried out modular two multiplication operation generated code metamessage, to realize multi-user communication.The signal of finishing the code element moulding is admitted to signal frame former (108) to form the final signal frame that is used for transmission; be separated by by certain time length protection interval (402) between the formed signal frame of signal frame former (108) (401); each signal frame (401) is comprised of protection interval (404) and a series of information code element (405) in synchronizing signal (403), the frame, and wherein information code element (405) is comprised of multiband modulation signal (406) and the protective redundancy (407) of the scrambled signals that superposeed.The final signal frame sends in the water by radiating circuit (109) and acoustic transducer.
The course of work of its demodulator of multiband DS-MFSK modulator-demodulator disclosed in the utility model is: the acoustic signals that modulator sends amplifies, is admitted to frame synchronizer (111) behind the filtering sampling by transducer and receiving circuit (110), frame synchronizer (111) adopt copy correlator or matched filter structure to the received signal the synchronizing signal in the frame carry out auto-correlation processing, and detect the moment that its relevant peaks decision signal arrives.The time reference that code element interceptor (112) provides according to frame synchronizer (111) is the intercepting message coded signal successively, and utilize PN code descrambling and decision device (113) that intercept signal is done scramble process, if the result behind the descrambling is effective output then to be admitted to next stage and to process, otherwise re-start definite operation of synchronizing signal.Useful signal behind the descrambling is admitted to FFT converter (114), FFT converter (114) carries out the FFT conversion to the useful signal behind the descrambling, and by frequency spectrum soft decision information demodulator (115) to FFT converter (114) operation result divide frequency band successively from low to high frequency band carry out soft-decision, realize demodulates information, information exchange after the demodulation recovers transmitting terminal information after crossing parallel-to-serial converter (116) and channel decoder (117).
Multiband DS-MFSK modulator-demodulator disclosed in the utility model have realize simple, robustness is high, can realize the advantage of higher speed underwater sound communication and multi-user communication, specifically:
The first, multiband DS-MFSK modulator-demodulator disclosed in the utility model utilizes look-up table to carry out the multiband frequency map, has realized simply and effectively the information modulation.
The second, multiband DS-MFSK modulator-demodulator disclosed in the utility model utilizes fft algorithm and minute frequency band soft-decision, can realize fast multiband MFSK demodulation.
The 3rd, multiband DS-MFSK modulator-demodulator disclosed in the utility model utilizes the pseudo random sequence correlation properties, realizes the multi-user communication function.
This shows, the utility model is novel in design, with high content of technology, be easy to realize and cost lower, the engineering that is very suitable for the fields such as exploration of ocean resources, underwater operation, marine environmental monitoring is used.
Description of drawings
Understand in order to make content of the present utility model be more conducive to the relevant speciality technical staff, the below carries out simple declaration to accompanying drawing.
Fig. 1 is multiband DS-MFSK modem structure block diagram described in the utility model.
Fig. 2 is the information frame structural representation of multiband DS-MFSK modulator-demodulator described in the utility model.
Fig. 3 is a kind of implementation block diagram of multiband DS-MFSK modulator-demodulator described in the utility model.
Fig. 4 is multiband DS-MFSK modulator-demodulator emission power amplifier schematic diagram described in the utility model.
Fig. 5 is multiband DS-MFSK modem frame synchronized copy correlator Output rusults described in the utility model.
Fig. 6 is multiband DS-MFSK modulator-demodulator soft-decision spectral window described in the utility model.
Specific embodiments
The utility model is described in further detail below in conjunction with accompanying drawing and a kind of better specific embodiment of the utility model.
As a kind of better example of executing of the present utility model, the working band of selective system is 20～40KHz, the whole system bandwidth is divided into 4 frequency bands, each frequency band adopts the 4FSK modulation system, then the frequency between the adjacent carrier is spaced apart 1250Hz, symbol duration guarantees that the FFT frequency-measurement accuracy is 0.5 times of frequency interval, has 1/T=625Hz this moment, corresponding T=1.6ms.[0023] as a kind of better example of executing of the present utility model, synchronizing signal adopts the linear FM signal LFM that often uses in the underwater sound communication, the temporal resolution power of LFM signal: 0.88/B, for improving as far as possible the temporal resolution of this signal, signal bandwidth B gets altogether 20kHz of 20-40kHz, and this moment, time sense was 0.044ms.Time-bandwidth product BT has represented the processing gain of broadband signal, and in order to satisfy the requirement of time-bandwidth product BT much larger than 100, choosing in this embodiment T is 20ms, and this moment, time-bandwidth product BT=400 can satisfy processing requirements.
As a kind of better example of executing of the present utility model, at practical communication receiver place, because the existence of the factors such as synchronous error, when carrying out the code element intercepting, the code element window can not intercept respective symbol fully accordingly, therefore a minute frequency band frequency map finish and through the pseudo random sequence spread processing after added code element moulding link, this link will be finished information code after mapping and the stack and add the blank redundancy of the preceding paragraph and offset the error of code element intercepting.Draft the blank redundant 0.4ms that is at this.
As a kind of better example of executing of the present utility model; because system adopts the form of frame structure; every frame signal sends first synchronous code, reserves afterwards one section blank redundant protection interval as synchronizing signal and follow-up code element, then sends the information code element of predetermined quantity.Mainly consider the protection gap length of every frame signal at this,, therefore draft the frame protection and be spaced apart 50ms generally tens of milliseconds magnitude for the channel maximum delay expansion of many ways, shallow sea.
As a kind of better example of executing of the present utility model, in actual applications, the adjustment that the symbolic number that every frame signal is carried is in good time according to the channel actual conditions, be 1s the coherence time of general shallow sea channel, drafts frame length in 1s.The duration of each code element is that symbol duration adds that the blank redundancy of 0.4ms is about 2ms.Calculate take frame length as 1s, every frame synchronizing signal 20ms, protection interval 50ms, the protection between the consecutive frame is spaced apart 50ms, and then the information code element duration is 880ms, and the number of symbols of carrying is 880/2=440.According to the structural representation of the complete signal frame of above-mentioned design as shown in Figure 2.
As a kind of better example of executing of the present utility model, at receiving terminal, at first utilize copy correlator (matched filter) to detect synchronizing signal, mainly be to utilize the good autocorrelation of synchronizing signal to detect the moment that its relevant peaks decision signal arrives, be illustrated in figure 5 as the result of copy correlator output.
As a kind of better example of executing of the present utility model, by signal initial time successively intercepting message code element, at first the code element of intercepting is carried out despreading and process, the signal after the despreading is done the FFT computing, obtain spectral window as shown in Figure 6.
Can find out from spectral window, each frequency peak value of each frequency band is obvious, can from low-frequency band begin to high frequency band one by one frequency band, frequency carries out soft-decision one by one, realizes the fast demodulation of information.At last the information of demodulation is delivered to the stay of two nights through parallel-serial conversion and channel-decoding and finish communication task.
As a kind of better example of executing of the present utility model, as shown in Figure 3, provided whole multiband DS-MFSK modem hardware implementation structure block diagram.The below describes the specific implementation of this structure in detail.
As a kind of better example of executing of the present utility model, interface module (301) is used for connecting information source or the stay of two nights, namely receives the information of information source after modulation intelligence or output demodulation to the stay of two nights.Microcontroller (302) links to each other with interface module (301), finish channel-decoding and the parallel-serial conversion operation of chnnel coding in the modulator and string and conversion operations and demodulator, consider cost and power consumption requirement, microcontroller is selected MSP430 series or STM32 series.Sub-band frequency mapper (103 in the modulator, 103,105), code element former (106), frame synchronizer (111) in signal frame former (108) and the demodulator, code element interceptor (112), PN code descrambling and decision device (113), FFT converter (114), frequency spectrum soft decision information demodulator (115) is all realized by the FPGA that links to each other with microcontroller (303), modulator radiating circuit (109) is comprised of drive circuit (304) and power amplifier (305), in the present embodiment power amplifier is designed to D class power amplifier as shown in Figure 4.The receiving circuit of demodulator (110) is comprised of filtering and amplifying circuit (308) and analog to digital converter (309), digital to analog converter (309) links to each other with FPGA (303), power amplifier (305) links to each other with acoustic transducer (307) by a transmitting-receiving change-over circuit (306) with filtering and amplifying circuit (308), thereby finishes above-mentioned modulation /demodulation function.
The above only is a kind of better feasible example of executing of the present utility model; described embodiment limits scope of patent protection of the present utility model; therefore the equivalent structure done of every utilization specification of the present utility model and accompanying drawing content changes, and in like manner all should be included in the protection range of utility model.
Claims (8)
1. multiband DS-MFSK modulator-demodulator, it is characterized in that modulator is comprised of the channel encoder (101), deserializer (102), sub-band frequency mapper (103,104,105), code element former (106), signal frame former (108) and the radiating circuit (109) that link to each other successively, code element former (106) also links to each other with pseudo-random sequence generator (107) simultaneously; Demodulator is comprised of signal receiving circuit (110), frame synchronizer (111), code element interceptor (112), PN code descrambling and the decision device (113), FFT converter (114), frequency spectrum soft decision information demodulator (115), parallel-to-serial converter (116), the channel decoder (117) that link to each other successively.
2. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that modulator is divided into a plurality of sub-bands with communication bandwidth, and by after the MFSK modulation in sub-band frequency mapper (103,104,105) the realization sub-band, send into code element former (106) after the modulation intelligence addition with a plurality of sub-bands.
3. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that pseudo noise code that modulation signal after code element former (106) is with a plurality of sub-band additions and pseudo-random sequence generator (107) produce carries out the modular two multiplication operation and form symbol signal, to realize multi-user communication.
4. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that sub-band frequency mapper (103,104,105) adopts the reflection method of tabling look-up will be mapped to through the information of signal source and channel on the interior different carrier of sub-band, and with the parallel stack of different frequency bands carrier wave.
5. multiband DS MFSK modulator-demodulator as claimed in claim 1; it is characterized in that being separated by by certain time length protection interval (202) between the formed signal frame of signal frame former (108) (201); each signal frame (201) is comprised of protection interval (204) and a series of information code element (205) in synchronizing signal (203), the frame, and wherein information code element (205) is comprised of multiband modulation signal (206) and the protective redundancy (207) of the scrambled signals that superposeed.
6. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that frame synchronizer (111) adopts copy correlator or matched filter structure, the synchronizing signal of amplifying, filtering via receiving circuit (110) after sampling is copied relevant treatment, and detect the moment that its relevant peaks decision signal arrives.
7. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that successively intercepting message coded signal of time reference that code element interceptor (112) provides according to frame synchronizer (111), and utilize PN code descrambling and decision device (113) that intercept signal is done scramble process.
8. multiband DS-MFSK modulator-demodulator as claimed in claim 1, it is characterized in that FFT converter (114) carries out the FFT conversion to the useful signal behind the descrambling, and by frequency spectrum soft decision information demodulator (115) to FFT converter (114) operation result divide frequency band successively from low to high frequency band carry out soft-decision, realize demodulates information.
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| CN 201220455280 CN202772879U (en) | 2012-09-10 | 2012-09-10 | Multiband DS-MFSK modem |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832964A (en) * | 2012-09-10 | 2012-12-19 | 北京引创科技有限责任公司 | Multi-band DS-MFSK (Direct Sequence-Multi Frequency Shift Keying) modem |
| CN112953594A (en) * | 2021-04-23 | 2021-06-11 | 四川九洲电器集团有限责任公司 | Burst MSK direct sequence spread spectrum communication synchronous detection device and method |
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2012
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832964A (en) * | 2012-09-10 | 2012-12-19 | 北京引创科技有限责任公司 | Multi-band DS-MFSK (Direct Sequence-Multi Frequency Shift Keying) modem |
| CN112953594A (en) * | 2021-04-23 | 2021-06-11 | 四川九洲电器集团有限责任公司 | Burst MSK direct sequence spread spectrum communication synchronous detection device and method |
| CN112953594B (en) * | 2021-04-23 | 2022-02-15 | 四川九洲电器集团有限责任公司 | Burst MSK direct sequence spread spectrum communication synchronous detection device and method |
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