Information modulation method of amplitude pulse width combination coding in laser signal energy transmission

Abstract

The present invention discloses an information modulation method for amplitude pulse width combination coding in laser signal energy simultaneous transmission, and belongs to the field of electrical communication technology. The method: determine the number of coded data according to the modulation resolution, and then determine the number of bits of binary data code and check code according to the number of coded data; binary encode N groups of square wave signals with different amplitudes and the same pulse width of high-frequency modulated current signals to obtain data codes and check codes that complement each other; use the code corresponding to the square wave signal with positive amplitude and pulse width of 0.5T as the start code, and the code corresponding to the square wave signal with negative amplitude and pulse width of 0.5T as the stop code, and package every continuous (2N+2)nbits of data once to form data to be sent in frames. The present invention increases the number of binary codes per unit time, increases the system communication rate, achieves output power balance, and reduces the capacity of the energy storage capacitor in the laser power supply.

Description

Technical Field

[0001] The invention discloses an information modulation method of amplitude pulse width combination coding in laser signal energy simultaneous transmission, relates to laser wireless energy transmission technology, and belongs to the technical field of electrical communication. Background Art

[0002] Laser wireless energy transfer (LPT) has the advantages of long transmission distance, good directionality, and high energy density. It has broad application prospects in power supply occasions for mobile devices such as drones. However, many mobile devices also have remote control and communication needs in addition to power supply. Laser information and energy simultaneous transmission (SWIPT) technology uses a set of equipment based on LPT technology to simultaneously perform energy transmission and information communication. Laser SWIPT technology can make up for the shortcomings of the original LPT system, promote the development of equipment integration and miniaturization, and make equipment more flexible and convenient to use.

[0003] The laser wireless energy transmission system mainly consists of three parts: the laser transmitter, free space, and the laser receiver. The laser transmitter realizes electro-optical conversion through the laser, converts electrical energy into light energy and transmits it to free space, and then uses the photoelectric effect of the photovoltaic cell at the receiving end to convert light energy into electrical energy and transmit it to the load or battery. Thanks to the excellent directionality and monochromaticity of the laser, the biggest advantage of LPT technology is that it can provide fixed-point energy to space targets with considerable power. Laser information and energy synchronous transmission technology currently has two technical routes: communication as the main and energy transmission as the auxiliary, and energy transmission as the main and communication as the auxiliary. At present, the laser of the laser information and energy synchronous transmission technology with energy transmission as the main and communication as the auxiliary outputs a straight current to transmit energy, and at the same time outputs a high-frequency AC modulated current to transmit information. The transmission power can reach 10W and the communication rate can reach 4kb / s, while the laser information and energy synchronous transmission technology with communication as the main and energy transmission as the auxiliary can increase the communication rate to 34.2Mb / s. Although there is a mutually restrictive relationship between the transmission power and communication rate of the laser information and energy simultaneous transmission system due to the physical characteristics of the laser photovoltaic cells, there is still room for improvement in the communication rate of the laser information and energy simultaneous transmission technology that focuses on energy transmission and supplements communication.

[0004] The optical power of the laser can be changed by changing the input current of the laser. At present, the laser power supply of the laser wireless energy transmission system, which mainly transmits energy and supplements communication, outputs a straight current to transmit energy, and outputs a high-frequency AC modulated current to transmit information. When the optical power received by the photovoltaic cell at the receiving end changes with the input current of the laser, the information coupled in the light beam can be demodulated by detecting the current output on the photovoltaic cell, that is, when the output current of the photovoltaic cell is greater than the mean, the time slot can be considered as "1", and the time slot less than the mean can be considered as "0". However, this modulation and demodulation method does not fully utilize the large degree of freedom of high-frequency modulation current, so the communication rate of this scheme still has room for further improvement.

[0005] On the other hand, in the modulation and demodulation design of laser signal transmission technology with energy transmission as the main function and communication as the auxiliary function, nbits of data code are usually sent first, and then nbits of check code are sent to maintain power balance. This information modulation and demodulation method has the extreme situation that multiple consecutive nbits of data codes correspond to the same level of high-frequency modulation current. The capacity of the energy storage capacitor of the bidirectional converter in the laser power supply also needs to be designed according to the above extreme situation. Usually, the capacity of the energy storage capacitor is increased to cope with the occurrence of extreme situations, which increases the size of the laser power supply.

[0006] In summary, the present invention aims to propose an information modulation method of amplitude pulse width combination coding in laser signal energy simultaneous transmission to overcome the defects of the existing laser signal energy simultaneous transmission technology which mainly transmits energy and supplements communication. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned background technology and propose an information modulation method for amplitude-pulse-width combination coding in laser information and energy synchronous transmission, encode a group of square wave signals with opposite amplitudes but the same pulse width in the high-frequency modulated current generated by the laser into complementary data codes and check codes, increase the number of coding combinations per unit time, and thus increase the communication rate, avoid the extreme situation that the high-frequency modulated current represented by multiple consecutive data codes has the same amplitude, reduce the capacity of the energy storage capacitor of the bidirectional converter in the laser power supply, reduce the volume of the laser power supply, and solve the technical problems that the communication rate of the existing laser information and energy synchronous transmission technology with energy transmission as the main and communication as the auxiliary needs to be improved and the energy storage capacitor capacity in the laser power supply is large.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned invention object:

[0009] A method for information modulation in laser signal energy simultaneous transmission includes the following five steps:

[0010] Step 1: Determine the number m of high-frequency modulation current pulse widths according to the modulation resolution of the demodulation circuit. The number of high-frequency modulation current pulse widths multiplied by the number of high-frequency modulation current amplitudes is the number M of coded data, M=2*m. Then determine the number n of binary data codes and binary check codes according to the number M of coded data, M=2. n , m is a non-zero natural number;

[0011] Step 2, dividing the high-frequency modulated current signal into m groups of square wave signals with opposite amplitudes but the same pulse width, encoding each group of square wave signals into two n-bits binary codes, and the two n-bits binary codes are complementary;

[0012] Step 3, using the nbits binary code corresponding to the square wave signal with a positive amplitude of the high-frequency modulated current signal and a pulse width of 0.5T as the start code, and using the nbits code corresponding to the square wave signal with a negative amplitude of the high-frequency modulated current signal and a pulse width of 0.5T as the stop code;

[0013] Step 4, for N groups of square wave signals with opposite amplitudes but the same pulse width between the square wave signal with a positive amplitude and a pulse width of 0.5T and the square wave signal with a negative amplitude and a pulse width of 0.5T of the high-frequency modulated current signal, the two nbits binary codes corresponding to each group of square wave signals are used as data codes and check codes in sequence, where N is a non-zero natural number;

[0014] Step 5. Within a coding cycle T, the (2N+2)nbits encoding corresponding to the start code, stop code, and the data code and check code between the start code and the stop code are packaged into a frame of data to be sent. The data code of the data to be sent in each frame is freely sent according to the communication signal. Each data code is followed by a check code that is complementary to it. The check code is followed by a group of freely sent data codes and check codes, and the data codes and check codes appear alternately.

[0015] Furthermore, in a method for modulating information in laser energy simultaneous transmission, when the amplitude of the square wave signal represented by the next group of data codes is the same as the amplitude of the square wave signal represented by the previous group of check codes, the pulse width of the square wave signal represented by the previous group of data codes is subtracted from the total pulse width of the square wave signals with the same amplitude to obtain the pulse width of the square wave signal represented by the next group of data codes; when the total pulse width of the square wave signals with the same amplitude is less than the pulse width of the square wave signal represented by the previous group of data codes, it is determined that a bit error has occurred; when the pulse width of the square wave signal represented by the data code corresponding to a group of square wave signals is different from the pulse width of the square wave signal represented by the check code, it is determined that a bit error has occurred.

[0016] Furthermore, in the demodulation circuit of the receiving end of the LPT system, a decoupling capacitor is connected in parallel to the back side of the photovoltaic panel. The decoupling capacitor is used to separate the DC current and the AC current, and the time signal reflecting the pulse width is converted into a voltage signal on the decoupling capacitor. The voltage across the decoupling capacitor is sampled in real time, and the amplitude and pulse width of the modulated current are demodulated according to the rate of change of the voltage signal on the decoupling capacitor and the voltage value, and finally a frame of data for signal transmission is obtained.

[0017] The present invention adopts the above technical solution and has the following beneficial effects:

[0018] (1) Performance advantages: Compared with the traditional laser signal transmission modulation and demodulation method, this method introduces the pulse width of the high-frequency modulated current as the signal source, and uses the amplitude and pulse width of the high-frequency modulated current as the information source. The amplitude and pulse width of the high-frequency modulated current are combined and encoded, which increases the number of binary codes per unit time, thereby increasing the system communication rate. The communication rate is effectively improved by increasing the number of pulse widths that can be demodulated.

[0019] (2) System volume and cost advantages: Since the present invention encodes a group of square wave signals with opposite amplitudes and the same pulse width in the high-frequency current signal into complementary data codes and check codes, it can not only realize the demodulation of the high-frequency superimposed current by the signal demodulation circuit, but also achieve output power balance, reduce the requirements for the energy storage capacitor in the bidirectional converter, reduce the capacitance of the energy storage capacitor, and reduce the volume of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the block diagram of the laser signal simultaneous transmission system.

[0021] Figure 2(a) shows the straight current diagram, modulated current diagram, superimposed current diagram, and energy storage capacitor voltage diagram of the transmitting end during the transmission of one frame of data. Figure 2(b) shows the photovoltaic panel output current diagram, decoupling capacitor current diagram, decoupling capacitor demodulated voltage diagram, decoupling capacitor voltage diagram, and encoding diagram of the receiving end during the transmission of one frame of data.

[0022] Figure 3 The figure is a flow chart of the information modulation method of the present invention. DETAILED DESCRIPTION

[0023] The high communication rate laser signal energy simultaneous information modulation and demodulation method proposed in the present invention is to make the purpose, technical scheme and effect of the present invention clearer and more specific, and further explain the present invention in detail with reference to the accompanying drawings.

[0024] 1. Laser power parallel structure

[0025] Figure 1In the laser power supply, two converters with different functions are connected in parallel. Their control loops are independent of each other and each performs closed-loop control on the circuit. The two converters have their own functions. The unidirectional converter is responsible for outputting a straight current i for transmitting energy. DC Its main function is to provide constant current drive for the laser, and the bidirectional converter is responsible for outputting the modulation current i of the transmission information. pulse Its main function is to control the output power of the laser by controlling the input current, thereby realizing the transmission of communication signals. The two complement each other and realize the simultaneous transmission of energy and information using laser as the carrier. Figure 1 The bidirectional converter uses capacitors as energy storage elements. From the perspective of the driving power supply, when the required pulse current is higher than the straight current provided by the unidirectional converter, the capacitor provides energy and discharges the capacitor through the output current of the bidirectional converter. Conversely, the capacitor is charged through the output current of the bidirectional converter and the energy is stored in the capacitor.

[0026] 2. Introducing high-frequency modulation current encoding method of pulse width

[0027] Here is the bit rate formula:

[0028]

[0029] In formula (1), M is the number of coding combinations in binary coding, and T is the period of one coding. In order to improve the signal transmission speed of the laser signal transmission system, the large degree of freedom of high-frequency modulation current can be used to increase the number of codes per unit time. Therefore, the pulse width is introduced as the source of high-frequency modulation current signal transmission. First, the average period T of the modulation current is obtained according to the average frequency of the output modulation current of the bidirectional converter, and then according to the demodulation accuracy of the demodulation circuit, different pulse widths can be demodulated, such as pulse widths T1, T2, T3, and T4. In order to enable the demodulation circuit to demodulate different pulse widths, the modulation current is set to consist of several groups of square wave signals with opposite amplitudes and the same pulse widths, that is, a square wave signal with a random amplitude and a random pulse width is emitted (a data code after demodulation), followed by a square wave signal with an opposite amplitude and the same pulse width (a check code after demodulation), and the binary codes corresponding to a group of square wave signals with opposite amplitudes and the same pulse width are required to be complementary codes. Assume that the number of pulse widths that can be demodulated is m, and the number of bits of data code and check code is n. When pulse width is not introduced as a signal source, the number of binary codes M is 2. After pulse width is introduced as a signal source, the number of binary codes M is 2m. Substituting M into the bit rate formula, it can be seen that the communication rate can be increased by (1+log2 m) times. And square wave signals with opposite amplitudes and the same pulse width are encoded as a group, which reduces Figure 1 The capacity of the decoupling capacitor in the bidirectional converter can further reduce the size of the system, and when a failure occurs in the coding, modulation and demodulation, the coding method in which the check code is followed by the data code can detect the problem in time.

[0030] Taking the demodulated pulse widths of 0.2T, 0.5T, 0.6T, and 0.7T as an example, Figure 3 The information modulation method of amplitude-pulse-width combination coding shown encodes the high-frequency modulated current, and specifically includes the following five steps.

[0031] Step 1: Determine the number of high-frequency modulated current signal pulse widths m according to the modulation resolution of the demodulation circuit, m=4, the number of coded data M, M=2*4=8, the number of bits of the binary data code and the number of bits of the binary check code n, n is determined according to M=2 n OK, n=3.

[0032] Step 2: Divide the high-frequency modulated current signal into 4 groups of square wave signals with opposite amplitudes but the same pulse widths. Encode the square wave signal with a positive amplitude and a pulse width of 0.5T as a 3-bit start code 101; encode the square wave signal with a negative amplitude and a pulse width of 0.5T as a 3-bit stop code 010; encode the square wave signal with a positive amplitude and a pulse width of 0.2T as a 3-bit start code 100; and encode the square wave signal with a negative amplitude and a pulse width of 0.2T as a 3-bit stop code 010. its stop code 011, the square wave signal with a positive amplitude of the high-frequency modulated current signal and a pulse width of 0.6T is encoded as a 3-bit start code 110, the square wave signal with a negative amplitude of the high-frequency modulated current signal and a pulse width of 0.6T is encoded as a 3-bit stop code 001, the square wave signal with a positive amplitude of the high-frequency modulated current signal and a pulse width of 0.7T is encoded as a 3-bit start code 111, and the square wave signal with a negative amplitude of the high-frequency modulated current signal and a pulse width of 0.7T is encoded as a 3-bit stop code 000. The encoding combinations are shown in Table 1.

[0033] Step 3, use the 3-bit binary code 101 corresponding to the square wave signal with a positive high-frequency modulated current signal amplitude and a pulse width of 0.5T as the start code, and use the n-bit binary code 010 corresponding to the square wave signal with a negative high-frequency modulated current signal amplitude and a pulse width of 0.5T as the stop code.

[0034] Step 4. For two groups of square wave signals with opposite amplitudes but the same pulse width, namely, a square wave signal with a positive high-frequency modulated current signal amplitude and a pulse width of 0.5T and a square wave signal with a negative amplitude and a pulse width of 0.5T, the two nbits binary codes corresponding to each group of square wave signals are used as data codes and check codes in sequence. For example, a square wave signal with a negative high-frequency modulated current signal amplitude and a pulse width of 0.2T is used as the data code, and a square wave signal with a positive high-frequency modulated current signal amplitude and a pulse width of 0.2T is used as the check code. A square wave signal with a positive high-frequency modulated current signal amplitude and a pulse width of 0.6T is used as the data code, and a square wave signal with a negative high-frequency modulated current signal amplitude and a pulse width of 0.6T is used as the check code.

[0035] Step 5, within a coding cycle T, the (2*2+2)*3 bits coding consisting of the start code, stop code, data code between the start code and the stop code, and check code is packaged into a frame of data to be sent. Each frame of data to be sent contains 3 groups of data codes and check codes, and the data code is sent first and then the check code.

[0036] The level of the square wave signal represented by each data code in the same frame of data to be sent is random. When the level of the square wave signal represented by the next data code is opposite to the level of the square wave signal represented by the previous check code, the receiving end can demodulate. When the level of the square wave signal represented by the next data code is the same as the level of the square wave signal represented by the previous data code, it is necessary to subtract the pulse width to determine the pulse width of the square wave signal represented by the next data code.

[0037] Figure 2(a) and Figure 2(b) are the corresponding waveforms of the receiving and transmitting ends of the laser signal transmission system. It can be seen from the high-frequency modulation current diagram that the high-frequency modulation current signals are square wave signals with a positive pulse width of 0.5T, square wave signals with a positive pulse width of 0.6T, square wave signals with a negative pulse width of 0.6T, square wave signals with a negative pulse width of 0.2T, square wave signals with a positive pulse width of 0.2T, and square wave signals with a negative pulse width of 0.5T. The demodulated codes are start code 101, data code 110, check code 001, data code 011, check code 100, and stop code 010. When the transmitted square wave is a current signal with a positive amplitude of 1.1T, if there is a stop code before the square wave signal, when the square wave signal with a positive amplitude is greater than 0.5T, the first 0.5T is determined to be the start code, and the pulse width of the square wave signal corresponding to the first data code is 1.1T minus 0.5T, which is 0.6T. When the amplitude of the square wave signal corresponding to the first check code is the same as the amplitude of the square wave signal represented by the second data code, a square wave signal with a negative amplitude and a pulse width of 0.8T appears. According to the principle that the pulse width of the square wave signal corresponding to the first check code is the same as that of the first data code, if the total pulse width is greater than the pulse width of the square wave signal corresponding to the first data code, the total pulse width 0.8T is subtracted from the pulse width 0.6T of the square wave signal corresponding to the first data code, and the pulse width of the square wave signal corresponding to the second data code is 0.2T. If the total pulse width is less than the pulse width of the first data code, it is determined to be a bit error. Finally, the second check code is obtained from the square wave signal with a positive amplitude and a pulse width of 0.2T. If a group of data codes is different from the check code, it is determined to be a bit error. When the amplitude of the current signal represented by the last check code is the same as that of the termination code, according to the total number of check codes N designed previously, it is determined that the last square wave signal with a negative pulse width of 0.5T represents the termination code. The energy storage capacitor diagram in the bidirectional converter and the decoupling capacitor diagram in the demodulation circuit show the energy capacitor voltage and the decoupling capacitor voltage changes.

[0038]

[0039] Table 1

[0040] 3. Demodulation circuit

[0041] A decoupling capacitor is added at the receiving end of the laser wireless power transmission system to separate the AC current and DC current output by the photovoltaic cell, and the voltage on the decoupling capacitor is sampled according to the formula Convert the time signal representing the pulse width of the modulation current into a voltage signal on the decoupling capacitor. Assume that the modulation current with a positive amplitude and a pulse width of 0.5T charges the decoupling capacitor to U dc +U c1 , the voltage of the decoupling capacitor at the switching point of the modulation current with opposite amplitude and same pulse width is determined by the slope change of the decoupling capacitor, and the voltage at this point is compared to remove the DC quantity Udc Afterwards with U c1 The amplitude and pulse width of the modulated current are obtained by the size of the modulated current, thereby demodulating the data transmitted by the transmitting end of the laser wireless power transmission system.

[0042] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for modulating information using amplitude and pulse width combination coding in laser signal transmission, characterized in that: Determine the number m of high frequency modulated current signal pulse widths, the number M of coded data, the number n of binary data code bits and the number n of binary check code bits according to the modulation resolution of the demodulation circuit; Divide the high-frequency modulated current signal into m groups of square wave signals with opposite amplitudes but the same pulse width, and encode each group of square wave signals into two n-bits binary codes, wherein the two n-bits binary codes are complementary; The nbits binary code corresponding to the square wave signal with a positive amplitude and a pulse width of 0.5T of the high-frequency modulated current signal is used as the start code, and the nbits binary code corresponding to the square wave signal with a negative amplitude and a pulse width of 0.5T of the high-frequency modulated current signal is used as the stop code, and T is a coding cycle; For N groups of square wave signals with opposite amplitudes but the same pulse width between a square wave signal with a positive amplitude and a pulse width of 0.5T and a square wave signal with a negative amplitude and a pulse width of 0.5T of a high-frequency modulated current signal, the two nbits binary codes corresponding to each group of square wave signals are used as data codes and check codes in turn, and N is a non-zero natural number; In one coding cycle T, the (2N+2)nbits coding consisting of the start code, the stop code, the data code between the start code and the stop code, and the check code is packaged into a frame of data to be sent.

2. The information modulation method of amplitude pulse width combination coding in laser signal transmission according to claim 1 is characterized in that: The number M of the encoded data is the product of the number of high-frequency modulated current pulse widths and the number of high-frequency modulated current signal amplitudes, M=2*m.

3. The information modulation method of amplitude pulse width combination coding in laser signal transmission according to claim 1 is characterized in that: The number of bits n of the binary data code is based on M=2 n Sure.

4. The information modulation method of amplitude pulse width combination coding in laser signal transmission according to claim 1 is characterized in that: When the amplitude of the square wave signal corresponding to the data code in the next group of square wave signals is the same as the amplitude of the square wave signal corresponding to the check code in the current group of square wave signals, the pulse width of the square wave signal corresponding to the data code in the current group of square wave signals is subtracted from the total pulse width of the square wave signals with the same amplitude to obtain the pulse width of the square wave signal corresponding to the data code in the next group of square wave signals; when the total pulse width of the square wave signals with the same amplitude is less than the pulse width of the square wave signal corresponding to the data code in the current group of square wave signals, it is determined that a bit error has occurred; when the pulse width of the square wave signal corresponding to the data code in a group of square wave signals is different from the pulse width of the square wave signal corresponding to the check code, it is determined that a bit error has occurred.

5. A method for demodulating information encoded by a combination of amplitude and pulse width in laser signal transmission, characterized in that: When the receiving end of the LPT system receives a laser signal carrying the information to be sent obtained by the information modulation method of amplitude-pulse-width combination coding in laser signal transmission as described in any one of claims 1 to 4, the voltage signal of the decoupling capacitor in the demodulation circuit is sampled in real time, and the amplitude and pulse width of the high-frequency modulation current are demodulated according to the rate of change of the voltage signal on the decoupling capacitor and the voltage value.

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