CN101826905B - Elastic wave through-the-earth signal diversity reception method - Google Patents
Elastic wave through-the-earth signal diversity reception method Download PDFInfo
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Abstract
The invention provides an elastic wave through-the-earth signal diversity reception method, and relates to diversity reception technology applied in the fields of exploration and through-the-earth communication. In the method, signals dispersed at each frequency point and in each transmission mode are organically fused together at an earth channel receiving end by adopting a way of multi-mode reception and multi-frequency point reception diversity, so the signal-to-noise (SNIR) of the receiving end is improved. When elastic waves are transmitted in an earth medium, the transmission mode of the elastic waves is changed, while frequency is shifted under the influence of the piezoelectric effect, waveguiding effect and resonant cavity effect of the earth medium. The method provided by the invention has the advantages of improving reception gain by collecting signal energy dispersed in each mode and at each frequency point, and suppressing the attenuation of the elastic waves in the earth medium by the diversity combination of multi-mode and multi-frequency information to finally fulfill the aim of improving the detection performance of a receiver.
Description
Technical field
The present invention relates to geological prospecting and through the earth communication technical field, particularly a kind of elastic wave is passed through the diversity receiving method of earth signal.
Background technology
In ground through communication system, adopt the single-frequency elastic wave as carrier wave, information is carried through the band spectrum modulation ripple, with earth coupling loudspeaker the form of modulated wave with the P ripple is coupled in the earth.At receiving terminal, it is closely related with the intensity that transmits that discovery receives signal than multifrequency point, simultaneously, receives in the signal and not only contain the P wave component identical with transmitting terminal, also has and transmission closely-related S ripple of signal and R ripple signal.Consult the correlation theory of seimic wave propagation and the correlation theory of geological prospecting, find also to have in the part document description of this phenomenon.Though the mechanism of frequency migration and mode switch is not clear, transmission characteristic influence in the earth is tangible to the elastic wave signal for it.
Elastic wave has good transmission characteristic in isotropic elastic fluid, still, actual the earth channel is complicated and changeable.Exist non-continuous face in the medium; And structure is quite complicated; The propagation velocity of elastic wave in medium changes violent, has velocity gradient at multilayer dielectricity, bending and tilted interface and in the critical refraction layer, thereby causes transmitting information frequency and the isoparametric change of phase place.
In the earth medium, except the isotropic elasticity medium of minority, the medium that also has anisotropic elastic medium, non-homogeneous isotropic elasticity medium, The viscoelastic medium and contain the fluid hole.For those by itself being exactly the rock solid that anisotropic crystal or the isotropism mineral grain with certain orientations form; The level that combines by the isotropic thin interbed of difference or the sedimentary rock of inclination; And exist directed stress and align vertical or rock solid that the inclination crack is constituted; When their characteristic length during much smaller than the elastic wave wavelength, the elastic wave of in this rocks, propagating just can show as anisotropy.Simultaneously, the piezoelectric effect of part earth medium is obvious, and the waveguiding effect of part thin strate is obvious, and part special geology structure has the elastic wave resonance characteristic.The piezoelectric effect of channel, waveguiding effect resonant cavity effect are the exclusive characteristics of this channel according to one's analysis bigly, are that common wireless communications is not available, also are to make elastic wave produce the main cause of frequency migration and transport mode translations.
The diversity technique of using in the GSM is one of effective measures of anti fading.Its utilize to receive signal structurally with statistical property on different characteristics distinguish, and according to certain rules gather with merge handle realize anti-fading.Wherein, the signal that frequency diversity (in-band diversity) is utilized different frequency range in statistical uncorrelated characteristic, is realized the anti fading function after fading channel.During realization, information to be sent is modulated at respectively on the carrier wave of different frequency of space and launches.Geological prospecting and the employed low-frequency elastic ripple of ground through communication system based on spread spectrum technic are just meeting this condition.Use the reception technique of rake, can utilize the mutual irrelevance of multipath signal, divide set and each footpath information, thereby suppress the multipath fading of the earth channel, finally reach the purpose of the detection performance that improves receiver.
Short wave communication and microwave relay research field adopt the space diversity mode, utilize the same emission source signal of a plurality of antenna element diversity receptions, and the signal that a plurality of antennas are received synthesizes the lifting that obtains the signal total received power.The propagation characteristic that this diversity receiving method can resist atmospheric medium effectively changes the decline that causes.
Above-mentioned diversity receiving technology all do not consider multi-mode signal and many migration carrier signals, and the present invention is just in order to solve elastic wave multimode multifrequency diversity reception problem.
Summary of the invention
The object of the present invention is to provide a kind of elastic wave to pass through the diversity receiving method of earth signal, this method of reseptance effectively suppresses the multimode decline and the frequency migration decline of the earth channel through dividing set and multimode signal and many migration carrier signals.
The present invention is for realizing above-mentioned purpose, and the technical solution of employing is:
A kind of elastic wave is passed through the diversity receiving method of earth signal, comprises channel detection step and message transmission step;
The channel detection step comprises:
(1) selected frequency and sequence code, with detectable signal based on this sequence code and frequency band spectrum modulation to a certain carrier wave, and carrier signal amplified;
(2) carrier signal after amplifying according to step (1) is converted into elasticity P ripple by loud speaker (elastic wave transmitting antenna) and is coupled to the earth channel and transmits;
(3) according to the signal behind step (2) the process the earth dissemination channel, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
(4) four kinds of signals of telecommunication that obtain according to step (3); By the mode of migration Frequency point scan module through the change local frequency; Search for each peak power point, and judge that each peak power point and step (1) carrier signal are closely related, thereby judge the migration Frequency point of local domain the earth channel; The migration Frequency point of P ripple, SH ripple, SV ripple and R ripple is corresponding with step (1) carrier signal frequency, be recorded in the local domain channel parameter storehouse as channel parameter;
(5) repeating step (1) to (4) obtains the migration Frequency point of P ripple, SH ripple, SV ripple and R ripple under the various frequency carrier signals, has set up local domain channel parameter storehouse;
The message transmission step comprises:
1. selected sequence code, with information to be transmitted based on this sequence code band spectrum modulation to a certain carrier wave, and the modulated carrier signal amplified;
2. the carrier signal after 1. amplifying according to step is converted into elasticity P ripple by loud speaker (elastic wave transmitting antenna) and is coupled to the earth channel and transmits;
3. 2. pass through the signal behind the earth dissemination channel according to step, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
4. the signal of telecommunication that 3. obtains according to step is carried out sending into demodulation and time domain equalization module after frequency-selective filtering amplifies according to channel parameter in the local domain channel parameter storehouse by frequency selective amplifier;
5. demodulation and time domain equalization module are carried out demodulation process and equilibrium treatment according to the selected local frequency of channel parameter in the local domain channel parameter storehouse; Synthesize and relevant despreading module by energy; The signal energy that collection is dispersed on each frequency of P ripple, SH ripple, SV ripple, R ripple is synthetic again, and detects to the received signal, and the signal energy of diffusion is separated, handles, merged; Carry out despreading decoding according to the 1. selected sequence code of step afterwards, reduction transmission information.
Noun of the present invention:
Transmission mode: when elastic wave is propagated in the earth; Will be with the form transmission of compressional wave (P ripple), shear wave (S ripple) and R ripple, we call transmission mode to these circulation ways, and wherein shear wave (S ripple) is divided into SH ripple and SV ripple; The SH ripple is the shear wave perpendicular to ground, and the SV ripple is the shear wave that is parallel to ground.
Frequency migration: after the elastic wave of single-frequency is propagated in the earth; Can receive a plurality of frequency signals at receiving terminal; That is to say that the elasticity wave frequency changes, we claim that this phenomenon is the frequency migration, is called the migration frequency with tranmitting frequency different received signal frequency.
Effective carrier wave: meeting frequency of occurrences transport phenomena when propagating in the earth because of elastic wave, those Frequency points that can be detected and carry useful information are effective carrier wave in receiving signal.
Elastic wave multimode multifrequency diversity receiving method of the present invention is accomplished by the pick-up and the diversity receiver of 4 different modes; Pick-up is positioned on the stratum of the earth channel receiving terminal one side or the stratum; The elastic wave signal converts the signal of telecommunication to after being received by pick-up; Receiver is a capital equipment of the present invention, and in order to accomplish communication or geological prospecting task, the spread spectrum elastic wave transmitter with the present invention's coupling is indispensable.
Comprise channel detection and message transmission two parts, channel detection is a process indispensable before communication link is set up.Because being a parameter, the earth channel changes very slow channel (being constant-parameter channel); And the region is different; There is very large difference again in channel parameter; Before communication link is set up, carry out channel detection and not only can reduce the channel estimating complexity of receiving terminal greatly, and be convenient to the selected subchannel that is fit to local domain, reduce the energy loss of elastic wave in transmission course as much as possible.
Because the particularity of earth medium has determined; Elastic wave receives the influence of Resonant cavity oscillation Effect of waveguiding effect and special geology structure on piezoelectric effect, the part stratum of part medium when in the earth, propagating; Its transmission mode can change, and under the excitation of a certain frequency, can produce and the closely-related new frequency signal of focus.The task of channel detection is exactly through detection process that the situation " generaI investigation " of the mode switch situation of local domain and the migration of each radio-frequency component occurrence frequency is clear, for the selected and model selection of system works frequency lays the foundation.
Message transmission is the key component of geological prospecting or through the earth communication, and its process and channel detection are very similar, and just purpose is different.The present invention collects the signal energy that is dispersed in a plurality of transmission modes and a plurality of migration Frequency points as much as possible, improves receiving sensitivity.
No matter channel detection or message transmission dispose a spread spectrum transmitter at transmitting terminal, and according to the needs of multiple access and communication quality demand, transmitting terminal is selected identical frequency expansion sequence sign indicating number for use with receiving terminal.
At receiving terminal, pick-up connects low noise amplifier and frequency-selecting filter, and low noise amplifier is connected multimode multifrequency diversity receiver with frequency-selecting filter, exports recovering signal after the separation of signal process receiver, processing, the merging.
Above-mentioned pick-up is embedded in the stratum of the earth channel receiving terminal one side.Receive through a plurality of pick-ups through the elastic wave signal of the earth propagation, and be converted into the signal of telecommunication to the weak vibration signal that obtains according to the different mode setting with each strata interface reflection back different mode.
The signal of telecommunication of pick-up output amplifies through low noise and frequency-selective filtering is removed noise and interference.Then, adopt the multimode multifrequency receiver to carry out coherent detection to the received signal, the signal energy of diffusion is separated, handles, merged, and effectively utilize, improve antijamming capability, overcome fade-out, increase received power.
A plurality of data demodulators in the receiver carry out data demodulates, the despreading of PN sign indicating number and multiple correlation computing to the strongest a plurality of frequencies that searched; And, send into frequency with the pattern combiner merges with result output, promptly carry out branch and gather also; Decipher again, generate recovering signal.
And, also have a sub-cells in each data demodulator, be used for tracking loop pattern and frequency phase place are carried out demodulation.
Beneficial effect of the present invention:
A kind of multimode multifrequency diversity receiving method that the present invention proposes; It adopts correlated frequency to divide the mode of collection; The mutual separate signal that will be dispersed in each pattern and the frequency at the earth channel receiving terminal organically combines, thereby has improved the Signal to Interference plus Noise Ratio (SNIR) of receiving terminal.
A kind of multimode multifrequency diversity receiving method that the present invention proposes; Correlation theory according to wideband spread-spectrum signal; Design the spread-spectrum signal and the signal processing mode that corresponding multimode multifrequency receives of suitable spreading ratio, at signal receiving end all son migration carrier signals of all receiving modes are carried out diversity reception, to improve receiving gain; And through dividing set and multipath information; Thereby the multipath fading that suppresses the earth channel separates the signal energy of actual dispersion in the earth channel, handle, merge, and effectively utilizes; Solved in geological prospecting and the ground through communication system since the reflected signal that causes complicated and changeable of earth formation faint with the problem that receives difficulty, improved the detection performance of receiver.
Description of drawings
Fig. 1 is a diversity receiving method channel detection theory diagram.
Fig. 2 is a diversity receiving method message transmission theory diagram.
Embodiment
A kind of elastic wave is passed through the diversity receiving method of earth signal, comprises channel detection step and message transmission step;
The channel detection step comprises:
(1) selected frequency and sequence code, with detectable signal based on this sequence code and frequency band spectrum modulation to a certain carrier wave, and carrier signal amplified;
(2) carrier signal after amplifying according to step (1) is converted into elasticity P ripple by loud speaker (elastic wave transmitting antenna) and is coupled to the earth channel and transmits;
(3) according to the signal behind step (2) the process the earth dissemination channel, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
(4) four kinds of signals of telecommunication that obtain according to step (3); By the mode of migration Frequency point scan module through the change local frequency; Search for each peak power point, and judge that each peak power point and step (1) carrier signal are closely related, thereby judge the migration Frequency point of local domain the earth channel; The migration Frequency point of P ripple, SH ripple, SV ripple and R ripple is corresponding with step (1) carrier signal frequency, be recorded in the local domain channel parameter storehouse as channel parameter;
(5) repeating step (1) to (4) obtains the migration Frequency point of P ripple, SH ripple, SV ripple and R ripple under the various frequency carrier signals, has set up local domain channel parameter storehouse;
The message transmission step comprises:
1. selected sequence code, with information to be transmitted based on this sequence code band spectrum modulation to a certain carrier wave, and the modulated carrier signal amplified;
2. the carrier signal after 1. amplifying according to step is converted into elasticity P ripple by loud speaker (elastic wave transmitting antenna) and is coupled to the earth channel and transmits;
3. 2. pass through the signal behind the earth dissemination channel according to step, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
4. the signal of telecommunication that 3. obtains according to step is carried out sending into demodulation and time domain equalization module after frequency-selective filtering amplifies according to channel parameter in the local domain channel parameter storehouse by frequency selective amplifier;
5. demodulation and time domain equalization module are carried out demodulation process and equilibrium treatment according to the selected local frequency of channel parameter in the local domain channel parameter storehouse; Synthesize and relevant despreading module by energy; The signal energy that collection is dispersed on each frequency of P ripple, SH ripple, SV ripple, R ripple is synthetic again, and detects to the received signal, and the signal energy of diffusion is separated, handles, merged; Carry out despreading decoding according to the 1. selected sequence code of step afterwards, reduction transmission information.
Cooperate hardware to specify the application of diversity receiving method of the present invention in conjunction with accompanying drawing.
As shown in Figure 1, hardware system is made up of spread spectrum transmitter, P ripple loud speaker, P ripple pick-up, SH ripple pick-up, SV ripple pick-up, R ripple pick-up, low noise amplifier, migration frequency scanning module, each pattern effective mobility frequency identification module and channel detection controller.The channel detection process is under the coordination control of channel detection controller, to accomplish.Frequency that the transmitting terminal utilization is selected and random sequence sign indicating number are coupled in the earth through P ripple loud speaker after detectable signal is modulated.Each pick-up is converted into the signal of telecommunication to the weak vibration signal that receives, and through low noise amplifier, removes noise and interference.Each pattern effective mobility frequency identification module scans all frequencies in the frequency range through the adjustment local frequency, searches for each peak power point.Through signal processing links such as detection, LPF and correlation filterings, according to decision rule judge each peak power point whether with transmit closely related, thereby judge the effective mobility frequency of local domain the earth channel.These frequencies are corresponding with the frequency that transmits with pattern, be recorded in the database as channel parameter.
As shown in Figure 2, hardware system is synthesized with relevant despreading module with time domain equalization module and each frequency energy by spread spectrum transmitter, P ripple loud speaker, P ripple pick-up, SH ripple pick-up, SV ripple pick-up, R ripple pick-up, frequency selective amplifier, demodulation and forms.The signal to be transmitted of spread spectrum transmitter emission is through behind the earth channel, and energy is distributed on a plurality of transmission modes and a plurality of frequency.Each pick-up becomes the signal of telecommunication with the elastic wave conversion of signals; Frequency selective amplifier carries out frequency-selective filtering according to the frequency that channel parameter in the local domain channel parameter storehouse provides, and send demodulation and time domain equalization module after the amplification; Demodulation and time domain equalization module are carried out demodulation process according to the selected local frequency of channel parameter in the local domain channel parameter storehouse, and carry out equilibrium treatment according to the classical communication theory; Synthesize and relevant despreading module at energy; It is synthetic again with the signal energy on each frequency to be dispersed in each pattern, and the multimode multifrequency point signal that receives is carried out coherent detection, and the signal energy of diffusion is separated, handles, merged; The row decoding of going forward side by side, reduction transmission information.
Though the earth channel inhomogeneities is very strong, Different Strata medium lithology difference is very big, and the transmission characteristic of certain zone in different time is highly stable again.Diversity receiving method of the present invention receives sub-carrier signal at signal receiving end to all and carries out diversity reception; To improve receiving gain; And through dividing set and multimode and multifrequency point information; Suppress the multimode and the multifrequency decline of the earth channel, the signal energy of actual dispersion is separated, handles, merged, and effectively utilize.Through recovering original signal fully after data processing and the decoding; Solved in geological prospecting and the ground through communication system because the reflected signal that causes complicated and changeable of earth formation is faint, multimode declines, move the frequency decline and receive difficult problem more; Improve the detection performance of receiver, further improved the validity and the reliability of geological prospecting and ground through communication system.
Certainly, above-mentioned explanation is not to be limitation of the present invention, and the present invention also is not limited in above-mentioned giving an example, and variation, remodeling, interpolation or replacement that the technical staff in present technique field is made in essential scope of the present invention also should belong to protection scope of the present invention.
Claims (1)
1. an elastic wave is passed through the diversity receiving method of earth signal, and it is characterized in that: said diversity receiving method comprises channel detection step and message transmission step;
The channel detection step comprises:
(1) selected frequency and sequence code, with detectable signal based on this sequence code and frequency band spectrum modulation to a certain carrier wave, and carrier signal amplified;
(2) carrier signal after amplifying according to step (1) is converted into elasticity P ripple by loud speaker and is coupled to the earth channel and transmits;
(3) according to the signal behind step (2) the process the earth dissemination channel, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
(4) four kinds of signals of telecommunication that obtain according to step (3); By the mode of migration Frequency point scan module through the change local frequency; Search for each peak power point, and judge that each peak power point and step (1) carrier signal are closely related, thereby judge the migration Frequency point of local domain the earth channel; The migration Frequency point of P ripple, SH ripple, SV ripple and R ripple is corresponding with step (1) carrier signal frequency, be recorded in the local domain channel parameter storehouse as channel parameter;
(5) repeating step (1) to (4) obtains the migration Frequency point of P ripple, SH ripple, SV ripple and R ripple under the various frequency carrier signals, has set up local domain channel parameter storehouse;
The message transmission step comprises:
1. selected sequence code, with information to be transmitted based on this sequence code band spectrum modulation to a certain carrier wave, and the modulated carrier signal amplified;
2. the carrier signal after 1. amplifying according to step is converted into elasticity P ripple by loud speaker and is coupled to the earth channel and transmits;
3. 2. pass through the signal behind the earth dissemination channel according to step, receive with P ripple pick-up, SH ripple pick-up, SV ripple pick-up and R ripple pick-up respectively, the faint elastic wave signal that obtains each pick-up is converted into the signal of telecommunication;
4. the signal of telecommunication that 3. obtains according to step is carried out sending into demodulation and time domain equalization module after frequency-selective filtering amplifies according to channel parameter in the local domain channel parameter storehouse by frequency selective amplifier;
5. demodulation and time domain equalization module are carried out demodulation process and equilibrium treatment according to the selected local frequency of channel parameter in the local domain channel parameter storehouse; Synthesize and relevant despreading module by energy; The signal energy that collection is dispersed on each frequency of P ripple, SH ripple, SV ripple, R ripple is synthetic again, and detects to the received signal, and the signal energy of diffusion is separated, handles, merged; Carry out despreading decoding according to the 1. selected sequence code of step afterwards, reduction transmission information.
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| WO2015161360A1 (en) * | 2014-04-25 | 2015-10-29 | Vital Alert Communication Inc. | Through-the-earth emergency radio system |
| CN105005075B (en) * | 2015-06-25 | 2017-04-12 | 中国石油集团川庆钻探工程有限公司地球物理勘探公司 | Multi-wave matching method based on seismic frequency information |
| CN107276683B (en) * | 2017-05-15 | 2020-04-21 | 深圳市朗信浩通科技有限公司 | Decoding method, sending method and device of underwater sound signal |
| CN109633736B (en) * | 2018-12-24 | 2022-01-25 | 山东科技大学 | Elastic wave phase-controlled transmitting inverse synthesis receiving method |
| CN112859158B (en) * | 2021-01-29 | 2022-04-29 | 中南大学 | Through-the-earth communication method and system based on active seismic source wave carrying |
| CN114499695B (en) * | 2022-01-05 | 2023-06-06 | 鹏城实验室 | Device, equipment and method for excitation of through-the-earth communication |
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| US20090140852A1 (en) * | 2007-11-29 | 2009-06-04 | Stolarczyk Larry G | Underground radio communications and personnel tracking system |
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