CN114050954A - Metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication - Google Patents

Metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication Download PDF

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CN114050954A
CN114050954A CN202111401624.0A CN202111401624A CN114050954A CN 114050954 A CN114050954 A CN 114050954A CN 202111401624 A CN202111401624 A CN 202111401624A CN 114050954 A CN114050954 A CN 114050954A
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temperature
data
signals
storage tank
oil storage
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CN114050954B (en
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魏东兴
夏守天
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Dalian University of Technology
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Dalian University of Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D90/00—Component parts, details or accessories for large containers
    • B65D90/48—Arrangements of indicating or measuring devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K13/00—Thermometers specially adapted for specific purposes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/709—Correlator structure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B11/00—Transmission systems employing sonic, ultrasonic or infrasonic waves
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B2001/6916—Related theory

Abstract

The invention discloses a metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication, which comprises the following steps: the temperature measuring circuit acquires temperature data in the closed metal oil storage tank at the current moment, modulates the temperature data and converts the modulated signals into ultrasonic signals, and the ultrasonic signals are transmitted out of the closed metal oil storage tank by taking the wall of the closed metal oil storage tank as a transmission medium; converting the received ultrasonic signals into electric signals and demodulating the electric signals to obtain temperature data in the closed metal oil storage tank, and displaying the temperature data through a display device; after the temperature data is obtained, adjustments, such as increasing, decreasing, or temperature, may be required. The temperature adjustment information is used as input information to be modulated and converted into ultrasonic signals, the wall of the closed metal oil storage tank is used as a transmission medium and is transmitted into the closed metal tank to be converted into electric signals, and the electric signals are demodulated, so that temperature control information can be obtained and temperature adjustment can be carried out.

Description

Metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication
Technical Field
The invention relates to an ultrasonic communication method, in particular to a metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication.
Background
The temperature of the oil storage tank is an important parameter for oil preservation, and excessive temperature can cause the edible oil to become acidic, deteriorate and the like. At present, the temperature measurement of oil storage tank mostly adopts temperature measurement optic fibre mode, and this kind of mode need reserve the cable position on sealing the oil storage tank, will influence the leakproofness of oil storage tank, adopts the ultrasonic wave as communication carrier transmission temperature information can not need reserve the cable position on the oil storage tank, can also avoid the electromagnetic wave electrostatic shielding's that the metal oil storage tank produced phenomenon.
In addition, in the conventional pi/4-QPSK modulation method, the phase differences corresponding to two paths of baseband signals I, Q are pi/4, 3 pi/4, 5 pi/4 and 7 pi/4, respectively, and the initial phase is 0, so that there are 8 phases of the differentially encoded pi/4-QPSK signals, which are 0, pi/4, pi/2, 3 pi/4, pi, 5 pi/4, 3 pi/2 and 7 pi/4, five amplitudes of '± 1', '± 0.707' and '0' are generated corresponding to the two paths of differential signals, and when correlation operations are performed under the condition of different amplitudes, the synchronization and the correlation cannot be determined, so that a result of wrong synchronization is generated when a spread spectrum communication receiving end performs the despreading correlation operations, and a demodulation result is wrong.
Disclosure of Invention
According to the problems in the prior art, the invention discloses a metal oil storage tank temperature detection method based on pi/4-QPSK spread spectrum ultrasonic communication, which comprises the following specific steps:
s1: acquiring temperature data in the closed metal oil storage tank at the current moment by using a temperature measuring circuit, and sending the temperature data to a modulator;
s2: the modulator modulates the temperature data acquired by the temperature measuring circuit and sends the modulated signals to the ultrasonic transducer;
s3: the ultrasonic transducer converts the modulated data signal into an ultrasonic signal, and the ultrasonic signal is transmitted to a second ultrasonic transducer outside the sealed metal tank by adopting the wall of the sealed metal oil storage tank as a transmission medium;
s4: the second ultrasonic transducer converts the received ultrasonic signals into electric signals convenient to process and transmits the electric signals to the demodulator;
s5: the demodulator demodulates the obtained electric signal to obtain and display temperature data in the closed metal oil storage tank;
s6: regulating and controlling the temperature in the closed metal oil storage tank based on the temperature in the closed metal oil storage tank and recording the temperature regulation and control data;
s7: transmitting the temperature regulation and control data to a modulator for modulation processing, and transmitting a modulated signal to a second ultrasonic transducer outside the metal oil storage tank;
s8: the second ultrasonic transducer outside the metal oil storage tank converts the modulated data signal into an ultrasonic signal, the wall of the sealed metal oil storage tank is used as a transmission medium, and the ultrasonic signal is transmitted to the ultrasonic transducer inside the sealed metal tank;
s9: the ultrasonic transducer in the closed metal tank converts the received ultrasonic signals into electric signals convenient for processing and sends the electric signals to the demodulator;
s10: the demodulator demodulates the obtained electric signal to obtain control information of the temperature in the closed metal oil storage tank, and the control information is transmitted to the temperature control device for temperature adjustment.
The modulation processing method of the modulator in S2 is the same as that of the modulator in S7, and the modulation processing of the modulator on the data is specifically as follows:
the data to be transmitted is converted in a serial-parallel mode, namely an original group of serial data D (t) is converted into two groups of parallel data I (t), Q (t), wherein after the parallel data are converted, the duration of each code element is twice that of the input code element;
and carrying out differential encoding on the two groups of parallel data. The differential encoding process comprises the following steps: matching the phase difference corresponding to the input data at the current moment according to the value of the input data at the current moment, obtaining the phase value corresponding to the previous output data according to the value of the output data at the previous moment, calculating to obtain the value of the current phase, finding the current output data corresponding to the current phase according to the current phase, and outputting the data. The procedure is as follows:
X(t)＝X(t-Ts)×cos(Δθt)-Y(t-Ts)×sin(Δθt)
Y(t)＝X(t-Ts)×cos(Δθt)+Y(t-Ts)×sin(Δθt)
in the formula,. DELTA.theta.tThe phase difference, T, corresponding to the values of the input signals I (T), Q (T)sFor symbol duration, X (T), Y (T) output differential signals for the current symbol time, X (T-T)s)、Y(t-Ts) Outputting a differential signal for a previous symbol time;
and carrying out pi/4-QPSK spread spectrum modulation on the two groups of parallel data after differential coding. The modulation process is as follows: firstly, two paths of currently input differential signals X (t), Y (t) respectively use different PN sequences to carry out spread spectrum modulation, a carrier generator generates a cosine function, orthogonal carriers are generated through pi/2 phase shift and are respectively multiplied with two paths of spread spectrum signals passing through spread spectrum, and then pi/4-QPSK spread spectrum modulation signals are generated through superposition to finish modulation. The process is as follows:
S(t)＝Re[(X(t)×PN1(t)+jY(t)×PN2(t))×ejωt]
the method adopted by the demodulator in S5 and S10 to despread and demodulate the data is the same, and the method for despreading and demodulating the data by the demodulator is as follows:
the demodulator first performs spread spectrum chip synchronization processing on the obtained signal. The synchronous processing process of the spread spectrum chips comprises the following steps: and sequentially delaying the received pi/4-QPSK spread signals by half chip time. Multiplying each signal after sequential time delay with a local carrier cos (ω t) and a PN sequence respectively, and performing integral summation on the signals obtained after multiplication in a code element time range, wherein the process is as follows:
Figure BDA0003365351040000031
in the formula TcExpressed as the duration of a PN sequence chip, i is expressed as the ith time delay, and the value range of i is
Figure BDA0003365351040000032
Taking absolute value of H (i) and comparing the values to obtain the largest group of data H (i)0) And recording the time delay times i ═ i0The corresponding time-delayed original data is
Figure BDA0003365351040000033
I.e. the time instant synchronized with the local carrier and the PN sequence.
After the synchronous time of the PN sequence is obtained, the signal is processed
Figure BDA0003365351040000034
And performing despreading processing. The despreading processing process comprises the following steps: will signal
Figure BDA0003365351040000035
And performing despreading operation, multiplying the despread signals by local orthogonal carriers respectively, multiplying the multiplied signals by a PN sequence corresponding to the modulation process respectively, and integrating the multiplied results within a code element duration time respectively, wherein the process is as follows:
Figure BDA0003365351040000036
Figure BDA0003365351040000037
in the formula, m is the mth code element, and I (m) and Q (m) are output values after two paths of signals are de-spread respectively;
after despreading, demodulating the obtained I (m) and Q (m) which are two paths of signals respectively. The demodulation process is as follows: symbol extraction is performed on I (m), Q (m) by using a symbol function, so that the output values of I (m), Q (m) are '+ 1' or '-1', and the subsequent demodulation calculation is performed. The process is as follows:
X(m)＝I(m)×I(m-1)+Q(m)×Q(m-1)
Y(m)＝I(m-1)×Q(m)-I(m)×Q(m-1)
Figure BDA0003365351040000038
Figure BDA0003365351040000039
when in use
Figure BDA00033653510400000310
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000311
the output value is '1'; when in use
Figure BDA00033653510400000312
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000313
the output value is '1';
when in use
Figure BDA0003365351040000041
When the temperature of the water is higher than the set temperature,
Figure BDA0003365351040000042
the output value is '1'; when in use
Figure BDA0003365351040000043
When the temperature of the water is higher than the set temperature,
Figure BDA0003365351040000044
the output takes the value of '-1'.
Due to the adoption of the technical scheme, the invention provides a pi/4-QPSK-based spread spectrum super-widebandThe method for detecting the temperature of the metal oil storage tank through sound wave communication redefines the phase difference delta theta corresponding to two original data signals I (t), Q (t)tThe amplitude of the two differential signals after the difference is only +/-1', which is beneficial to the correlation operation of the de-spread part in the spread spectrum communication, is convenient for the differential demodulation of the spread spectrum communication and achieves the aim of improving the accuracy of the ultrasonic communication system.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flow chart of an ultrasonic communication system according to an embodiment of the present invention;
FIG. 2 is a schematic block diagram of a π/4-QPSK modulator according to an embodiment of the present invention;
FIG. 3 is a chip synchronization process according to an embodiment of the present invention;
fig. 4 is a schematic block diagram of a pi/4-QPSK demodulator according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely with reference to the drawings in the embodiments of the present invention:
fig. 1 is a flowchart of an ultrasonic communication system according to an embodiment of the present invention, which specifically includes the following steps:
s1: acquiring temperature data in the closed metal oil storage tank at the current moment by using a temperature measuring circuit, and sending the temperature data to a modulator;
s2: the modulator modulates the temperature data acquired by the temperature measuring circuit and sends the modulated signals to the ultrasonic transducer;
s3: the ultrasonic transducer converts the modulated data signal into an ultrasonic signal, and the ultrasonic signal is transmitted to a second ultrasonic transducer outside the sealed metal tank by adopting the wall of the sealed metal oil storage tank as a transmission medium;
s4: the second ultrasonic transducer converts the received ultrasonic signals into electric signals convenient to process and transmits the electric signals to the demodulator;
s5: the demodulator demodulates the obtained electric signal to obtain and display temperature data in the closed metal oil storage tank;
s6: regulating and controlling the temperature in the closed metal oil storage tank based on the temperature in the closed metal oil storage tank and recording the temperature regulation and control data;
s7: transmitting the temperature regulation and control data to a modulator for modulation processing, and transmitting a modulated signal to a second ultrasonic transducer outside the metal oil storage tank;
s8: the second ultrasonic transducer outside the metal oil storage tank converts the modulated data signal into an ultrasonic signal, the wall of the sealed metal oil storage tank is used as a transmission medium, and the ultrasonic signal is transmitted to the ultrasonic transducer inside the sealed metal tank;
s9: the ultrasonic transducer in the closed metal tank converts the received ultrasonic signals into electric signals convenient for processing and sends the electric signals to the demodulator;
s10: the demodulator demodulates the obtained electric signal to obtain control information of the temperature in the closed metal oil storage tank, and the control information is transmitted to the temperature control device for temperature adjustment.
Table 1 shows a differential encoding phase mapping table according to an embodiment of the present invention, which is applied in steps S2, S5, S7, and S10, and specifically includes the following steps:
Figure BDA0003365351040000051
the table defines the values of the input signals I (t), Q (t) at the current time and the corresponding phase difference Delta thetatThe mapping relationship between them. Combining the values of the input signals I (t), Q (t) at the current moment, looking up the table to find the corresponding valuesCorresponding phase difference Delta thetatAnd the output signal X (T-T) at the previous symbol times)、Y(t-Ts) To determine the values of the output signals X (t), Y (t) at the current time.
Fig. 2 is a schematic block diagram of a pi/4-QPSK modulator according to an embodiment of the present invention, which mainly includes a serial-to-parallel converter, an encoder, and pi/4-QPSK spread spectrum modulation, and is applied to steps S2 and S7, and specifically includes the following steps:
the data to be transmitted is firstly converted in a serial-parallel way, namely an original group of serial data D (t) is converted into two groups of parallel data I (t), Q (t), wherein after the parallel data are converted, the duration of each code element is twice of the duration of an input code element;
and carrying out differential encoding on the two groups of parallel data. The differential encoding process comprises the following steps: according to the phase mapping relation in table 1, the phase difference corresponding to the input data at the current time is matched according to the value of the input data at the current time, the phase value corresponding to the previous output data is obtained according to the value of the output data at the previous time, the value of the current phase is calculated, the current output data corresponding to the current phase is found according to the current phase, and the data is output. The encoding process is as follows:
X(t)＝X(t-Ts)×cos(Δθt)-Y(t-Ts)×sin(Δθt)
Y(t)＝X(t-Ts)×cos(Δθt)+Y(t-Ts)×sin(Δθt)
in the formula,. DELTA.theta.tThe phase difference, T, corresponding to the values of the input signals I (T), Q (T)sFor the duration of a single symbol, X (T), Y (T) are represented as the output differential signal at the current symbol time, X (T-T)s)、Y(t-Ts) Outputting a differential signal for a previous symbol time;
and carrying out pi/4-QPSK spread spectrum modulation on the two groups of parallel data after differential coding. The modulation process is as follows: firstly, two paths of currently input differential signals X (t), Y (t) respectively use different PN sequences to carry out spread spectrum modulation, a carrier generator generates a cosine function, orthogonal carriers are generated through pi/2 phase shift and are respectively multiplied with two paths of spread spectrum signals passing through spread spectrum, and then pi/4-QPSK spread spectrum modulation signals are generated through superposition to complete the modulation process. The process is as follows:
S(t)＝Re[(X(t)×PN1(t)+jY(t)×PN2(t))×ejωt]
fig. 3 shows a chip synchronization procedure according to an embodiment of the present invention, which is applied to steps S5 and S10, and specifically includes the following steps:
and sequentially delaying the received pi/4-QPSK spread signals by half chip time. Multiplying each signal after sequential time delay with a local carrier cos (ω t) and a PN sequence respectively, and performing integral summation on the signals obtained after multiplication in a code element time range, wherein the process is as follows:
Figure BDA0003365351040000061
in the formula tcExpressed as the duration of a PN sequence chip, i is expressed as the ith time delay, and the value range of i is
Figure BDA0003365351040000062
Taking absolute value of H (i) and comparing the values to obtain the largest group of data H (i)0) And recording the time delay times i ═ i0The corresponding time-delayed original data is
Figure BDA0003365351040000063
I.e. the time instant synchronized with the local carrier and the PN sequence.
Fig. 4 is a schematic block diagram of a pi/4-QPSK demodulator according to an embodiment of the present invention, which is specifically applied to S5 and S10, and specifically follows:
after the synchronous time of the PN sequence is obtained, the signal is processed
Figure BDA0003365351040000071
And performing despreading processing. The despreading processing process comprises the following steps: will signal
Figure BDA0003365351040000072
The de-spread operation is carried out and,respectively multiplying the local orthogonal carrier wave and then respectively multiplying the local orthogonal carrier wave and the PN sequence corresponding to the modulation process, and then respectively integrating the result obtained after multiplication in a code element duration, wherein the specific process is as follows:
Figure BDA0003365351040000073
Figure BDA0003365351040000074
in the formula, m is the mth code element, and I (m) and Q (m) are output values after two paths of signals are de-spread respectively;
after despreading, demodulating the obtained I (m) and Q (m) which are two paths of signals respectively. The demodulation process is as follows: symbol extraction is performed on I (m), Q (m) by using a symbol function, so that the output values of I (m), Q (m) are '+ 1' or '-1', and the subsequent demodulation calculation is performed. The calculation process is as follows:
X(m)＝I(m)×I(m-1)+Q(m)×Q(m-1)
Y(m)＝I(m-1)×Q(m)-I(m)×Q(m-1)
Figure BDA0003365351040000075
Figure BDA0003365351040000076
according to the corresponding relationship between two paths of the original signal I, Q and Δ θ in table 1, it can be known that: when i (t) takes on the value '1',
Figure BDA0003365351040000077
when I (t) takes the value of '-1',
Figure BDA0003365351040000078
when q (t) takes on the value '1',
Figure BDA0003365351040000079
when Q (t) takes the value '-1',
Figure BDA00033653510400000710
so when
Figure BDA00033653510400000711
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000712
the output value is '1'; when in use
Figure BDA00033653510400000713
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000714
the output value of (a) is-1'; when in use
Figure BDA00033653510400000715
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000716
the output value is '1'; when in use
Figure BDA00033653510400000717
When the temperature of the water is higher than the set temperature,
Figure BDA00033653510400000718
the output value of (d) is-1'.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (3)

1. A temperature detection method for a metal oil storage tank based on pi/4-QPSK spread spectrum ultrasonic communication is characterized by comprising the following steps:
s1: acquiring temperature data in the closed metal oil storage tank at the current moment by using a temperature measuring circuit, and sending the temperature data to a modulator;
s2: the modulator modulates the temperature data acquired by the temperature measuring circuit and sends the modulated signals to the ultrasonic transducer;
s3: the ultrasonic transducer converts the modulated data signal into an ultrasonic signal, and the ultrasonic signal is transmitted to a second ultrasonic transducer outside the sealed metal tank by adopting the wall of the sealed metal oil storage tank as a transmission medium;
s4: the second ultrasonic transducer converts the received ultrasonic signals into electric signals convenient to process and transmits the electric signals to the demodulator;
s5: the demodulator demodulates the obtained electric signal to obtain and display temperature data in the closed metal oil storage tank;
s6: regulating and controlling the temperature in the closed metal oil storage tank based on the temperature in the closed metal oil storage tank and recording the temperature regulation and control data;
s7: transmitting the temperature regulation and control data to a modulator for modulation processing, and transmitting a modulated signal to a second ultrasonic transducer outside the metal oil storage tank;
s8: the second ultrasonic transducer outside the metal oil storage tank converts the modulated data signal into an ultrasonic signal, the wall of the sealed metal oil storage tank is used as a transmission medium, and the ultrasonic signal is transmitted to the ultrasonic transducer inside the sealed metal tank;
s9: the ultrasonic transducer in the closed metal tank converts the received ultrasonic signals into electric signals convenient for processing and sends the electric signals to the demodulator;
s10: the demodulator demodulates the obtained electric signal to obtain control information of the temperature in the closed metal oil storage tank, and the control information is transmitted to the temperature control device for temperature adjustment.
2. The pi/4-QPSK spread spectrum ultrasonic communication-based metal oil storage tank temperature detection method according to claim 1, characterized in that: the method for modulating and processing the data by the modulator in S2 and S7 is the same, and specifically adopts the following method:
the data to be transmitted is converted in a serial-parallel mode, an original group of serial data D (t) is converted into two groups of parallel data I (t), Q (t), and after the serial data are converted into the parallel data, the duration time of each code element is twice that of the input code element;
carrying out differential encoding on the two groups of parallel data, wherein the differential encoding process comprises the following steps: matching the phase difference corresponding to the input data at the current moment according to the value of the input data at the current moment, obtaining the phase value corresponding to the previous output data according to the value of the output data at the previous moment, calculating to obtain the value of the current phase, and finding the current output data corresponding to the current phase according to the current phase, wherein the process is represented as follows:
X(t)＝X(t-Ts)×cos(Δθt)-Y(t-Ts)×sin(Δθt)
Y(t)＝X(t-Ts)×cos(Δθt)+Y(t-Ts)×sin(Δθt)
in the formula,. DELTA.theta.tThe phase difference, T, corresponding to the values of the input signals I (T), Q (T)sFor symbol duration, X (T), Y (T) output differential signals for the current symbol time, X (T-T)s)、Y(t-Ts) Outputting a differential signal for a previous symbol time;
carrying out pi/4-QPSK spread spectrum modulation on the two groups of parallel data after differential coding, wherein the modulation process comprises the following steps: firstly, respectively using different PN sequences to carry out spread spectrum modulation on two paths of currently input differential signals X (t), Y (t), a carrier generator generates a cosine function, orthogonal carriers are generated through pi/2 phase shift and are respectively multiplied with two paths of spread spectrum signals passing through spread spectrum, and then pi/4-QPSK spread spectrum modulation signals are generated through superposition to complete modulation, and the process is as follows:
S(t)＝Re[(X(t)×PN1(t)+jY(t)×PN2(t))×ejωt]。
3. the pi/4-QPSK spread spectrum ultrasonic communication-based metal oil storage tank temperature detection method according to claim 1, characterized in that: the methods for despreading and demodulating the data by the demodulator in S5 and S10 are the same, and specifically adopt the following modes:
the demodulator firstly carries out spread spectrum chip synchronization processing on the obtained signal, and the spread spectrum chip synchronization processing process comprises the following steps: sequentially delaying the received pi/4-QPSK spread spectrum signals for half chip time, multiplying each sequentially delayed signal by a local carrier cos (ω t) and a PN sequence respectively, and performing integration and summation on the signals obtained after multiplication in a code element time range, wherein the process is as follows:
Figure FDA0003365351030000021
in the formula TcExpressed as the duration of a PN sequence chip, i is expressed as the ith time delay, and the value range of i is
Figure FDA0003365351030000022
Taking absolute value of H (i) and comparing the values to obtain the largest group of data H (i)0) And recording the time delay times i ═ i0The corresponding time-delayed original data is
Figure FDA0003365351030000023
Namely the time synchronous with the local carrier and the PN sequence;
after the synchronous time of the PN sequence is obtained, the signal is processed
Figure FDA0003365351030000031
And performing despreading processing, wherein the despreading processing process comprises the following steps: will signal
Figure FDA0003365351030000032
And performing despreading operation, multiplying the despread signals by local orthogonal carriers respectively, multiplying the multiplied signals by a PN sequence corresponding to the modulation process respectively, and integrating the multiplied results within a code element duration time respectively, wherein the process is as follows:
Figure FDA0003365351030000033
Figure FDA0003365351030000034
in the formula, m is the mth code element, and I (m) and Q (m) are output values after two paths of signals are de-spread respectively;
after despreading, demodulating the obtained I (m) and Q (m) which are respectively two paths of signals, wherein the demodulation process comprises the following steps: using a sign function to perform sign extraction on I (m), Q (m) to make the output values of I (m), Q (m) be +1 or-1 for the subsequent demodulation calculation, the following process is performed:
X(m)＝I(m)×I(m-1)+Q(m)×Q(m-1)
Y(m)＝I(m-1)×Q(m)-I(m)×Q(m-1)
Figure FDA0003365351030000035
Figure FDA0003365351030000036
when in use
Figure FDA0003365351030000037
When the temperature of the water is higher than the set temperature,
Figure FDA0003365351030000038
the output value is '1'; when in use
Figure FDA0003365351030000039
When the temperature of the water is higher than the set temperature,
Figure FDA00033653510300000310
the output value is '1'; when in use
Figure FDA00033653510300000311
When the temperature of the water is higher than the set temperature,
Figure FDA00033653510300000312
the output value is '1'; when in use
Figure FDA00033653510300000313
When the temperature of the water is higher than the set temperature,
Figure FDA00033653510300000314
the output takes the value of '-1'.
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