JPH0461314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wireless telemetry seismic survey data transmission method in seismic survey aimed at investigating underground structures.

[Prior art] In earthquake surveys aimed at investigating underground structures, many seismometers are arranged in a plane or in a straight line to detect seismic waves generated by artificial seismic devices such as dynamite, air guns, vibrators, etc. and analyze reflected waves and refracted waves contained in seismic wave signals. Seismometers are installed at over several hundred locations, and the analog signals of seismic waves detected by each seismometer are usually digitized by measurement equipment placed near the seismometer installation location, and centrally collected using wired or wireless communication means. transmit to the device. The central acquisition unit is mounted on a vehicle for land exploration or on board a ship for maritime exploration.

When transmitting signals by wire, the cable must be placed to avoid obstacles such as swamps, and when conducting seismic surveys while changing the position of the seismograph, it is necessary to rearrange the cable, which is an inconvenience. Wireless communication means are used to avoid this. However, when seismic data is transmitted by radio, interference and disturbance due to other radio communication signals or noise is large, multipath fading occurs, and the S/N of the signal received at the central acquisition device is reduced.
A problem arises in that the ratio deteriorates.

In seismic exploration, it is necessary to determine the installation position of each seismometer, and conventionally it has been necessary to measure the position of the seismometer using a seismic data transmission means and a separate system, such as a laser position measurement system.

[Object of the invention] The present invention enables highly reliable data transmission in wireless transmission of seismic wave signals in seismic exploration,
Another object of the present invention is to provide a wireless telemetry seismic survey data transmission method that can measure the position of a seismograph while transmitting data.

[Summary of the Invention] In the present invention, each measurement device converts a detected analog seismic wave signal into a digital signal, primary modulates a carrier wave with the signal, and further encodes a spreading code sequence for each measurement device. The seismic wave signal is transmitted as a second-order modulated and spectrum-spread signal, which is received by the acquisition device and despreaded to take correlation.Then, the first-order modulated signal is demodulated and the seismic wave signals sent from each measurement device are reproduced and recorded. .

In the spread spectrum communication system, a spreading code sequence with large autocorrelation and small cross-correlation is used, and as such a code sequence, for example, a Gold code sequence is used. In the present invention, in each measuring device,
Encoding is performed using such a code sequence with high autocorrelation and low cross-correlation, and correlation is detected in the signal received by the acquisition device and despreading is performed. In the acquisition device, the S/N of the received signal is low because the code sequence of the received signal has high autocorrelation and low cross-correlation.
Even if the ratio is poor, the original signal can be regenerated with high reliability. Since the received signal is encoded for each device, the recording device can classify and record signals sent simultaneously from each measuring device for each measuring device. In the conventional narrowband communication method that uses only primary modulation, if you try to transmit signals from each measurement device at the same time, you have to allocate a carrier signal with a different frequency to each measurement device, and the frequency allocation of the carrier signal is limited. However, according to the present invention, simultaneous transmission from each measuring device is possible.

According to the present invention, since the acquisition device can identify the received signal for each measurement device, by measuring the time from when the data transmission start signal is sent until the synchronization preamble code sent by each measurement device arrives. , the distance between the acquisition device and each measurement device can be measured. Therefore, seismic data reception and acquisition devices are placed at two or more different known locations, the data transmission start signal sent by one of the acquisition devices is identified by the other acquisition devices, and each measurement is performed after sending the data transmission start signal. The position of each measuring device can be determined by identifying the synchronization preamble signal sent by the device in each collecting device and measuring the distance between each collecting device and the measuring device.

When trying to transmit seismic data using the spread spectrum method, the measurement devices are distributed over a wide area and the distance between each measurement device and the acquisition device varies greatly, resulting in differences in the signal levels received by the acquisition device. This poses a problem in that it becomes difficult to distinguish signals from each measuring device based on autocorrelation. In addition, the acquisition device must synchronize and detect the correlation of each signal from each measurement device among the received signals, which are a mixture of signals from each measurement device, and the bit length of the spreading code is generally long. Therefore, if the arrival time of a signal from each measuring device cannot be predicted in advance, it will take a considerable amount of time to achieve synchronization, and there may be cases where some data from the measuring device is missing.

In the present invention, when each measurement device receives a transmission start signal, the level of the signal transmitted from the measurement device is automatically adjusted according to the signal level, and the transmission output of the measurement device far from the acquisition device is large. The output of the measurement device close to the acquisition device is kept low so that the signal levels received by the acquisition device are approximately equal. This allows the acquisition device to discriminate the signals of each measurement device based on autocorrelation.

In the seismic exploration system according to the present invention including two or more acquisition devices, the transmission output of each measurement device is adjusted so that the acquisition device obtains a signal at a constant level,
In addition, since it is possible to control each transmission output to a low level, interference to other wireless stations other than this system can be reduced, and one of the acquisition devices can be used as the main device and the other one can be used as the slave device. , when a measuring device that cannot receive data or that generates erroneous data is detected on the main device side, communicates between the main device and the slave device,
By collecting data from the measuring device using the slave device, it becomes possible to collect all earthquake data without error.

In the present invention, furthermore, planned placement information indicating the positional relationship between the acquisition device and each measurement device is stored in the acquisition device in advance, and the arrival time of the signal from each measurement device is determined by the acquisition device after receiving an instruction to start data transmission. By predicting and starting the synchronization operation for each measuring device, the synchronization operation can be performed smoothly, and as a result, the synchronization operation can be completed in a short time. Synchronous storage is performed by the acquisition device storing the elapsed time from sending the data transmission start command to receiving the signals sent by each measuring device.

[Example] An example of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an acquisition device 1 in an embodiment of a wireless telemetry seismic exploration device to which the present invention is applied.
2 and the arrangement of the measuring device 3-14 are shown.
Although the figure shows measuring devices #1 to #200, there may be more measuring devices. Acquisition device 1 is assumed to be a main acquisition device, and acquisition device 2 is assumed to be a sub-acquisition device. In seismic exploration, usually after testing each measuring device according to instructions from the acquisition device 1, the acquisition device 1 transmits an earthquake data transmission start signal to instruct an artificial epicenter (not shown) to generate an earthquake. Each measuring device starts transmitting earthquake data upon receiving the seismic data transmission start signal, transmits a signal of a synchronization preamble code encoded for each measuring device, and then transmits an earthquake data signal.
Here, the measuring device converts the analog seismic wave signal sent from the epicenter into a digital signal, performs spread spectrum modulation, and transmits the signal. The acquisition device 2 receives the data transmission start instruction signal from the acquisition device 1 and identifies the start of data transmission. The acquisition devices 1 and 2 correlate and despread the signals sent from each measurement device, identify the synchronization preamble code from each measurement value, and identify the arrival of the signal for each measurement device. The recording device 1 further performs despreading of the earthquake data and demodulation of the primary modulation, and reproduces and records the earthquake data.

FIG. 2 shows the configuration of the recording device 1. Acquisition device 2
The configuration is the same as that of the acquisition device 1. CRT
The terminal 15 having a display function is used by the operator to transmit signals to the measuring device and other acquisition devices, to display data received from other acquisition devices, and to control the inside of the acquisition device by the operator. The disk drive 16 holds data for synchronization operations.
The memory 17 is used to store earthquake data sent from each measuring device. Magnetic tape device 18, 19
is used for storing earthquake data and other data stored in the memory 17. central processing unit (CPU)
Reference numeral 20 performs data analysis and control of data flow between each component device within the acquisition apparatus. The transmission control interface 21 receives a data transmission start instruction sent from the acquisition device to each measuring device or a message for communicating with the acquisition device 2, stores it, and controls the transmission device 22. The information stored in the control interface 21 modulates a radio carrier signal and transmits it via the antenna 23. The receiving device 24 is a device that receives signals transmitted from the acquisition device 2, and the reception control interface 25 is a device that temporarily stores information received by the receiving device 24 and causes the CPU 20 to perform reception processing.

The receiving device 26 is a device that receives signals from each measuring device via an antenna 27. In this embodiment, each measuring device performs phase modulation using 2-phase PSK, and therefore the acquisition device receives the 2-phase PSK modulated signal. It has a demodulation function. The decoder devices 28, 29, and 30 are devices that correlate and despread the signals received by the receiver 26, and demodulate the primary modulation, and are respectively assigned to each measuring device. Decoder devices #1 to #N are provided, and the value of N is set to be 200 or more, which is the number of measuring devices shown in FIG. A mixture of code sequences from each measuring device received by the receiving device 26 is sent to each decoder device, and the code from the measuring device corresponding to the decoder device is determined from the code of the measuring device included in the code sequence. The sequence is identified and the original digital signal is reproduced from the code sequence. For each decoder device, the corresponding measuring device can be changed arbitrarily by the operator's operation. The decoder control interface 31 is a device to which decoder control information, such as change of compatible measuring device, is sent from the terminal 15 through operator operation, and control data with an address is sent to each decoder device in accordance with the information. Batsufua Gate 32,
33 and 34 are devices that receive demodulated data and status information from the decoder devices 28, 29, and 30 and gate these information to the bus interface 35. The status information indicates whether synchronization is currently achieved in the decoder device, whether data can be used, etc. The bus interface 35 performs predetermined signal conversion and the like in data transmission and reception between the buffer gates 32, 33, 34 and the bus 36. The data demodulated by the decoder device is
It is stored in the memory 17 under the control of the CPU 20.

FIG. 3 shows the configuration of the measuring device 3. Measuring device 4
The configuration of -14 is the same as the configuration of measuring device 3.
The receiving device 37 receives the radio signal from the recording device 1 via the antenna 38, demodulates it, reproduces the original signal, and outputs it. The control device 39 is a device that receives an instruction signal from the recording device that is reproduced by the receiving device 37, and controls the operation of each device in the measuring device in accordance with the instruction signal. The level detector 40 is a device that detects the level of the received signal, and the transmission output control device 41
is a device that controls the level of the transmission output according to the level of the received signal detected by the level detector 40, so that the signals sent from each measurement device to the acquisition device 1 have a substantially constant level. Control device 39
is equipped with a means for latching instruction information from the receiving device 37, and when an instruction to start a test or data transmission is sent from the acquisition device 1, the spreading code generator 42
and sends an operation start signal to the signal processing device 43. The control device 39 sends to the spreading code generator 42 a channel number representing the number of the measuring device. The spreading code generator 42 is a device that generates a spreading code for performing spectrum spreading. As the spreading code, a code such as a Gold code that has a large autocorrelation and a small cross-correlation is generated. Further, the synchronous preamble code of this code series includes a channel number representing the number of the measuring device.

The signal processing device 43 is connected to a known seismometer (not shown), and analog signals representing seismic waves from the seismograph are sent to the signal processing device 43. The signal processing device 43 has a function of amplifying an analog signal, removing noise with a filter, converting it into a digital signal, and outputting the digital signal. The signal processing device 43 can switch between a normal mode for reading seismic data, a test mode for digitizing and outputting a predetermined signal as a test, and switching a sample plate for conversion to a digital signal. These switching operations are performed under the control of the control device 39 in accordance with instructions from the acquisition device.
The modulator 44 and the power amplifier 45 constitute a transmitting device, and the modulator 44 performs primary modulation with the digital signal from the signal processing device 43, and further performs secondary modulation with the signal from the spreading code generator 41.
Outputs PSK2 phase spread spectrum signal.
The control device 39 gives a channel number representing the number of the measuring device to the spreading code generator 42,
The spreading code generated by the spreading code generator 42 includes number information of the measuring device. Power amplifier 45 amplifies the signal from modulator 44 to a predetermined level according to the output of transmission output control device 41 and transmits it via antenna 46.

Next, seismic survey data transmission will be explained with reference to FIGS. 2 and 3. Normally, before conducting seismic exploration, each measurement device is tested based on instructions from the acquisition device. In the acquisition device 1, the operator operates the terminal 15 and sends a test start instruction to each measurement device via the transmission control interface 21 and the transmission device 22. Each measuring device receives a test start instruction signal,
This signal is sent to the control device 39. The control device 39 latches the test start instruction and sends the test start instruction signal to the signal processing device 43 and the spreading code generator 42. The test start instruction signal received by the receiving device 37 is sent to the level detector 40, where the received signal level is detected and the detection result is sent to the transmission output control device. The operation mode of the signal processing device 43 is switched to a test mode, and a digital signal representing predetermined test data is firstly modulated by a modulator 44 and code sequenced using a code from a spreading code generator 42 to spread the spectrum. The output signal is sent to a power amplifier 45,
It is sent to the acquisition device 1 via the antenna 46. The acquisition device 1 analyzes and records test data.
Encoding of the test data signal in each measurement device and demodulation in the acquisition device are performed in the same manner as the encoding and demodulation of the seismic data signal, which will be described later. At the end of the test, the mode of the signal processing device 43 is switched to the normal mode under the control of the control device 39 based on a termination instruction from the operator.

If the test is conducted before an earthquake occurs, after the test is completed,
The operator instructs the artificial earthquake source device to perform an artificial earthquake using known means, operates the terminal 15, and sends an instruction to start data transmission to each measurement device via the transmission control interface 21 and the transmission device 22. Each of the measuring devices receives a data transmission start instruction signal at the receiving device 37 and sends this signal to the control device 39 .
The control device 39 latches the data transmission start instruction,
An operation start instruction signal is sent to the signal processing device 43 and the spreading code generator 42. The data transmission start instruction signal received by the receiving device 37 is also sent to the level detector 40, where the received signal level is detected and the detection result is sent to the transmission output control device 41.

The data transmission start instruction signal from the acquisition device 1 is also received by the reception device 24 of the acquisition device 2 and transmitted via the reception control interface 25.
It is stored in the memory 17 under the control of the CPU 20.
Also, based on the known distance between the acquisition devices 1 and 2,
The CPU 20 calculates the data transmission start instruction signal transmission time and also stores this in the memory 17.

An analog signal representing a seismic wave from a seismometer is amplified by a signal processing device 43 of the measuring device, converted into a digital signal, and sent to a modulator 44 . The modulator 44 performs primary modulation using a digital signal from the signal processing device 43, performs secondary modulation using a spreading code such as a Gold code from the spreading code generator 42, and is a code sequence that includes a channel number in a synchronization preamble section. Two-phase with spread spectrum
A PSK signal is generated and sent to the power amplifier 45.
The power amplifier 45 receives the modulated signal from the modulator 44,
According to the control signal from the transmission output control device 41, when the signal is received by the recording device 1, it is amplified to a predetermined level and sent to the recording device via the antenna 46.

In the acquisition device 1, a signal from the measuring device is received by the receiving device 26 via the antenna 27 and sent to decoder devices 28, 29, and 30. Based on the data representing the approximate distance between the acquisition device 1 and each measurement device stored in the floppy disk device 16, the CPU 20
A signal indicating the time at which the signal from the corresponding measuring device is expected to arrive is sent to each decoder device, and each decoder device starts synchronization operations from this time. When a signal arrives from a compatible measuring device, synchronization is established and despreading is performed, and the arrival of a signal from a compatible measuring device is immediately identified by the channel number included in the received code sequence. Decoder devices 28, 29, 3
0 further performs primary modulation demodulation on the despread signal and sends it to the bus interface 35 via buffer gates 32, 33, and 34.

The CPU 20 detects the status from each decoder device by scanning and stores it in the memory 17, and
Display on CRT display terminal 15.

Similarly, the acquisition device 2 identifies the arrival of signals from each measuring device and stores and displays them.
Each of the acquisition devices 1 and 2 measures the time from the transmission of the data transmission start instruction signal to the arrival of the signal from each measurement device, and the acquisition device 1 measures the time from the signal propagation time between the acquisition device 1 and each measurement device. The distance between the device 1 and each measurement device is calculated, and in the acquisition device 2, the signal propagation time from the acquisition device 1 to each measurement device and from the measurement device to the acquisition device 2 and the known distance between the acquisition devices 1 and 2 are calculated. The distance between the acquisition device 2 and each measurement device is calculated from the distance. Calculation is based on each acquisition device.
Performed by CPU. The position of each measuring device can be determined from these distances.

In the acquisition device 1, the decoder devices 28, 2
The data from each measuring device demodulated in steps 9 and 30 is stored in the memory 17 via buffer gates 32, 33, and 34 and a bus interface 35.

Each decoder device demodulates the spread spectrum modulated signal, and uses a spreading code sequence with large autocorrelation and small cross-correlation, so even if the S/N ratio of the received signal is poor, the original signal can be faithfully reproduced. be able to. In addition, since the level of the transmission output of each measurement device is controlled and the level of the signal from each measurement device received by the acquisition device is kept almost constant, the signal from the predetermined measurement device is mixed with the signal from each measurement device. signals can be discriminated based on autocorrelation.

When the operator wants to stop the transmission of seismic data, the operator operates the terminal 15 to send a stop command to each measuring device via the transmitting interface 21 and transmitting device 22, and when each measuring device receives this command at the receiving device 37. This instruction signal is sent to the control device 39, the control device 39 releases the latch of the data transmission instruction, and the signal processing device 43 and the spreading code generator 4
4 to end the operation of these devices. This ends the operation of the measuring device.

For measurement devices that cannot be received by the acquisition device 1 or that receive many errors in received data, communication is made between the acquisition devices 1 and 2 via their respective transmitting devices, receiving devices, etc., and the acquisition device 1 The acquisition device 2 can be configured to acquire earthquake data according to the instruction. In this case, reception and acquisition of seismic data in the acquisition device 2 is performed in the same manner as in the acquisition device 1, except that it is performed for a specific measuring device.

〔Effect of the invention〕

According to the present invention, seismic data is transmitted from each measurement device to the acquisition device using a spread spectrum communication method, and by using a spread code sequence with high autocorrelation and low cross-correlation, the data is transmitted from each measurement device to the acquisition device. Even if the S/N ratio of the received signal is poor, the original signal can be faithfully reproduced by the acquisition device, and highly reliable data can be transmitted when transmitting seismic survey data wirelessly. In addition, by using a spreading code sequence encoded for each measuring device, it is possible to measure the distance between the collecting device and each measuring device from the time from when the data transmission instruction is given to the receiving of the signal from each measuring device in the collecting device. Since it is possible, 2
Using the above-described acquisition device, it is possible to determine the position of each measuring device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the arrangement of an acquisition device and a measurement device in an embodiment of wireless telemetry seismic survey data transmission according to the present invention, FIG. 2 is a diagram showing the configuration of the acquisition device, and FIG. 3 is a diagram showing the configuration of the measurement device. FIG. 3 is a diagram showing the configuration. 1, 2... Acquisition device, 3-14... Measuring device,
15...terminal, 16...floppy disk device, 17...memory, 18, 19...magnetic tape device, 20...CPU, 22...transmission device,
24, 26... Receiving device, 28, 29, 30...
Decoder device, 32, 33, 34... Buffer gate, 37... Receiving device, 39... Control device, 4
0... Level detector, 41... Transmission output control device, 42... Spreading code generator, 43... Signal processing device, 44... Modulator, 45... Power amplifier.

Claims (1)

[Claims of Claims] 1. A wireless system that converts analog seismic signals from a plurality of seismometers that detect seismic waves caused by artificial earthquakes into digital signals using a plurality of measuring devices connected to each seismometer, and wirelessly transmits the digital signals to a recording device. A traditional method for telemetry seismic survey data, which includes the steps of: arranging two or more acquisition devices at predetermined positions, and transmitting a data transmission start instruction signal from one acquisition device; Upon receiving the start instruction signal, converts the analog seismic signal from the seismograph into a digital signal, performs primary modulation with the signal, and encodes each measurement device for each measurement device.The autocorrelation is large and the cross-correlation is small. a step of transmitting a modulated signal that is secondarily modulated with a spreading code and spread spectrum; and a step of receiving and despreading the signals transmitted from each measuring device in the main acquisition device that transmitted the data transmission start instruction signal. , the distance between the main acquisition device and each measurement device is calculated by identifying the signals from each measurement device and identifying the elapsed time from the sending of the data transmission start instruction signal to the arrival of the signal from each measurement device. , and a step of demodulating the primary modulated signal in the despread signal to reproduce and store the digital signal; Receives a data transmission start instruction signal and calculates the transmission time of the signal, receives and despreads each signal transmitted from each measuring device, identifies the signal from each measuring device, and transmits the data. A wireless telemetry seismic survey data transmission method comprising: identifying the elapsed time from sending a transmission start instruction signal to the arrival of a signal from each measuring device and calculating the distance between a sub-acquisition device and each measuring device. 2. The seismic telemetry type seismic survey data transmission method according to claim 1, in which each measuring device receives a transmission start instruction signal from an acquisition device, detects the level of the received signal, and transmits data according to the detected level. A seismic telemetry type seismic survey data transmission method in which the level of the transmitted output signal is controlled so that the level of the signal received by the acquisition device from each measurement device is approximately equal. 3. The seismic telemetry type seismic survey data transmission method according to claim 1, wherein the sub-recording device records seismic signals transmitted from the measuring device according to instructions from the main recording device. Data transmission method.