阅读说明：本技术 一种可被rfid标签识别的可见光编码方式 (Visible light coding mode capable of being identified by RFID (radio frequency identification) tag ) 是由 韩鲁冰 王鸽 惠维 丁菡 于 2021-09-03 设计创作，主要内容包括：一种可被RFID标签识别的可见光编码方式,所述RFID标签为光敏标签,以频率为至少80Hz的开关控制可见光闪烁照射RFID标签及其天线,从而将可见光的闪烁信息编码附加在RFID标签的EPC之上,解码时通过分析通信过程中EPC信号的相位变化即可获得可见光编码信息。通过该方式将可见光的闪烁信息编码附加在RFID标签的EPC之上,解码时通过分析通信过程中EPC信号的相位变化即可获得可见光的编码数据。(A visible light coding mode capable of being identified by an RFID tag is characterized in that the RFID tag is a photosensitive tag, visible light is controlled to flicker and irradiate the RFID tag and an antenna thereof by a switch with the frequency of at least 80Hz, so that visible light flicker information codes are attached to an EPC of the RFID tag, and the visible light coding information can be obtained by analyzing the phase change of an EPC signal in the communication process during decoding. By means of the method, the flicker information code of the visible light is attached to the EPC of the RFID tag, and the coded data of the visible light can be obtained by analyzing the phase change of the EPC signal in the communication process during decoding.)

1. A visible light coding mode capable of being identified by an RFID tag is characterized in that the RFID tag is a photosensitive tag, visible light is controlled to flicker and irradiate the RFID tag and an antenna thereof by a switch with the frequency of at least 80Hz, so that visible light flicker information is coded and attached to an EPC of the RFID tag, and the visible light coding information can be obtained by analyzing the phase change of an EPC signal in the communication process during decoding.

2. The visible light code pattern recognizable by the RFID tag as claimed in claim 1, wherein the photosensitive tag is formed by adding a photosensitive element to the circuit of the RFID tag.

3. The visible light code pattern recognizable by an RFID tag of claim 1, wherein the photosensitive element is a photodiode or a photoresistor, and is connected in parallel or in series with the RFID chip.

4. The visible light encoding method recognizable by the RFID tag as claimed in claim 1, wherein the frequency of the visible light switch is at least 80Hz, the data information with two visible light modulation schemes is generated by a "single-reply-level" data encoding method, the encoding is implemented by using a 7-bit and 15-bit message encoding method and using a "Frequency Shift Keying (FSK)" and a "Phase Shift Keying (PSK)" method, and the source code information is further encoded by using a "hamming code" to guarantee the accuracy of the post-decoding.

5. The visible light encoding method recognizable by RFID tags as claimed in claim 4, wherein said data encoding method of "single reply level" achieves normal reading of tags by commercial readers by reducing the visible light data encoding frequency to be much lower than the reading rate (60-140 Hz) of commercial RFID tags, and the optical switching frequency range is about 10kHz to 33.33 kHz.

6. The visible light coding method capable of being identified by the RFID tag according to claim 1, wherein the LED lamp is driven by the visible light through a Darlington transistor (Darlington tube) using an external power source, the Darlington tube (Darlington tube) is connected to a Microcontroller (MCU), a general purpose input/output interface (GPIO) of the microcontroller outputs a coded high/low level, and the high/low level controls the Darlington transistor to enable the LED lamp to obtain a power voltage matched with the lamp set from the outside, thereby controlling the high frequency flicker of the LED.

7. The visible light coding method capable of being identified by an RFID tag of claim 6, wherein the Darlington tube is a composite tube, and two triodes are connected in series to form an equivalent new triode.

8. The visible light coding method capable of being identified by the RFID tag as claimed in claim 1, wherein the data-coded information of the visible light is generated by using a microcontroller, and the time delay error of the visible light-coded information needs to be controlled within microseconds.

9. The visible light encoding method identified by the RFID tag of claim 1, wherein the visible light encoded information is encoded by using a bipolar non-return-to-zero code, and each group of codes is added with a preamble, wherein "Frequency Shift Keying (FSK)" uses symbols with different frequency periods to distinguish data 0 from data 1, and "Phase Shift Keying (PSK)" uses symbols with different phases to distinguish data 0 from data 1.

10. The visible light coding method capable of being identified by the RFID tag according to claim 1, wherein the RFID tag comprises a PET medium substrate (1-1), the PET medium substrate (1-1) is provided with an aluminum antenna (1-2), an RFID chip (1-3) and a photodiode (1-4), the photodiode (1-4) is connected to the RFID chip (1-3) in parallel through a conductive material, the working frequency of the PET medium substrate (1-1) is 860 MHz-960 MHz, and EPC Class1Gen2 communication protocol is adopted.

Technical Field

The invention belongs to the technical field of wireless radio frequency and visible light communication, and particularly relates to a visible light coding mode capable of being identified by an RFID (radio frequency identification) label

Background

Radio Frequency IDentification (RFID) is a wireless communication technology that can identify a specific target and read and write related data by Radio signals. The RFID technology is composed of a reader and an RFID tag, where the reader modulates data to be transmitted into an electromagnetic wave of a specific frequency, the RFID tag transmits the data from the RFID tag attached to an article by backscattering the electromagnetic wave signal, and the reader processes the signal after receiving the backscattering signal, so that the article can be automatically identified and tracked. RFID tags are classified into passive and semi-passive types and active types according to whether they need to carry a power source, wherein the passive type tags can obtain energy in an electromagnetic field emitted from a reader when operating, and thus do not need an additional power source. Passive RFID tags are relatively inexpensive and inexpensive to deploy, and are therefore more widely used.

At present, most of visible light communication and RFID communication are combined in a mode of changing an on-chip antenna, the tag is complex to manufacture and high in cost, once a communication protocol is determined, the coding mode cannot be changed at will, and the application has certain limitation.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a visible light coding method capable of being identified by an RFID tag, through which a visible light flashing information Code is attached to an EPC Electronic Product Code (EPC Electronic Product Code) of the tag, and the visible light coding data can be obtained by analyzing the phase change of an EPC signal in the communication process during decoding.

In order to achieve the purpose, the invention adopts the technical scheme that:

a visible light coding mode capable of being identified by an RFID tag is characterized in that the RFID tag is a photosensitive tag, visible light is controlled to flicker and irradiate the RFID tag and an antenna thereof by a switch with the frequency of at least 80Hz, so that visible light flicker information codes are attached to an EPC of the RFID tag, and the visible light coding information can be obtained by analyzing the phase change of an EPC signal in the communication process during decoding.

The photosensitive label is formed by adding a photosensitive element into a circuit of the RFID label.

The photosensitive element is a photosensitive diode or a photosensitive resistor and is connected with the RFID chip in parallel or in series.

The frequency of the visible light switch is at least 80Hz, data information with two visible light modulation mechanisms is generated through a single-reply-level data coding mode, the coding modes of 7-bit and 15-bit messages are adopted, and the coding modes are realized through a Frequency Shift Keying (FSK) mode and a Phase Shift Keying (PSK) mode, and the source code information is further coded through a Hamming code, so that the accuracy of later decoding is guaranteed.

The data coding mode of the single reply level achieves normal reading of the label by a commercial reader by reducing the visible light data coding frequency to be far lower than the reading rate (60-140 Hz) of the commercial RFID label, and the optical switching frequency range is about 10kHz to 33.33 kHz.

The LED lamp is driven by visible light through the Darlington transistor by using an external power supply, the Darlington tube is connected with a Microcontroller (MCU), a general purpose input/output interface (GPIO) of the microcontroller outputs a coded high-low level, and the high-low level controls the Darlington transistor to enable the LED lamp to obtain a power supply voltage matched with a lamp group from the outside, so that the high-frequency flicker of the LED is controlled.

The Darlington tube is a composite tube, and two triodes are connected in series to form an equivalent new triode.

The data coding information of the visible light is generated by using a microcontroller, and the time delay error of the visible light coding information needs to be controlled within microsecond level.

In the visible light coded information, a bipolar non-return-to-zero code mode is adopted to code the optical information level, and a preamble is added in each group of codes, wherein the Frequency Shift Keying (FSK) uses symbols with different frequency periods to distinguish data 0 from data 1, and the Phase Shift Keying (PSK) uses symbols with different phases to distinguish data 0 from data 1.

The RFID tag comprises a PET medium substrate 1-1, an aluminum antenna 1-2, an RFID chip 1-3 and a photodiode 1-4 are arranged on the PET medium substrate 1-1, the photodiode 1-4 is connected to the RFID chip 1-3 in parallel through a conductive material, the working frequency of the PET medium substrate 1-1 is 860 MHz-960 MHz, and an EPC Class1Gen2 communication protocol is adopted.

The invention has the beneficial effects that:

the RFID label adopted by the invention is a photosensitive label obtained by modifying a photosensitive diode, and the label can present different impedance characteristics under the switching action of visible light, so that visible light codes can be identified by the RFID label, and the combination of visible light and the existing RFID communication is realized.

The invention is not only suitable for passive RFID label systems, but also suitable for semi-passive and active RFID label systems. The technology can be applied to the practical application fields of information tracing, information positioning and the like.

Drawings

Fig. 1 is a photodiode RFID tag of the present invention that can implement optical communication.

Fig. 2 is an equivalent circuit diagram of a photodiode RFID tag of the present invention.

Fig. 3(a) is a symbol encoding of visible light data 0/1 using FSK.

Fig. 3(b) is a visible light data 0/1 symbol encoding using PSK.

Fig. 4(a) shows the PSK visible light information encoded by the hamming code.

Fig. 4(b) is a hamming code encoded FSK visible light information.

Fig. 4(c) is a coded (PSK) level oscilloscope display diagram.

Fig. 4(d) is a schematic diagram of a coded (FSK) level oscilloscope display.

Fig. 5(a) is coded PSK visible light information.

Fig. 5(b) is encoded FSK visible light information.

Fig. 5(c) is a coded (PSK) level oscilloscope display diagram.

Fig. 5(d) is a schematic diagram of a coded (FSK) level oscilloscope display.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The RFID tag is adopted as the photosensitive tag, the photosensitive tag can present different impedance characteristics under the switching action of visible light, so that visible light codes can be identified by the RFID tag, the combination of the visible light and the existing RFID communication is realized, when an antenna of the RFID tag is irradiated by the visible light, the impedance of an RFID chip port can shift, and further mismatch with the impedance of the antenna of the RFID tag is realized, the phase change of a backscattering signal on an RFID reflection signal is shown, when the visible light flickering frequency reaches a certain frequency, the phase of an EPC signal backscattered by the RFID tag can change along with the high-speed flickering of the visible light, the flickering information codes of the visible light are added on the EPC of the RFID tag through the mode, and the phase change of the EPC signal in the communication process can be analyzed during decoding, so that the coded data of the visible light can be obtained.

Referring to fig. 1, a schematic diagram of a photodiode RFID tag capable of communicating with the present invention is shown: the RFID tag material process is a coated paper or Inlay structure, 1-1 is a PET material medium substrate, the working frequency is 860 MHz-960 MHz, an EPC Class1Gen2 communication protocol is adopted, 1-2 is an aluminum material antenna, 1-3 is an RFID chip, and 1-4 is a 0805 packaged photosensitive diode; the photosensitive diode is connected to the RFID chip 1-3 in parallel through a conductive material.

Fig. 2 is a diagram of the LED driving circuit architecture of the present invention, wherein the MCU is powered by TTL level (5V/3.3V), and the darlington tube receives a control signal from the GPIO of the MCU, which controls the on/off of the high voltage (24V) power supply connected to the darlington tube, and thus controls the flashing of the LED to communicate with the photodiode RFID tag.

Fig. 3(a) shows the encoding of data 0 and data 1 according to the present invention, where ON represents high (light can be turned ON) and OFF represents low (visible light is turned OFF). The period of a single symbol is 100 us. The time t0 in PSK is 25 us. To ensure that the lamp is not left in the "off" state for long periods of time due to the transmission of low level data, it is necessary to set a state reversal at each symbol boundary. The additional preamble is a square wave signal of 70us period 3 times.

Fig. 3(b) shows the encoding method of "Frequency Shift Keying (FSK)" data 0 and data 1 according to the present invention, wherein ON represents high level (visible light ON) and OFF represents low level (visible light OFF). The period of a single symbol is 100 us. In FSK, the time t0 is 30us, and the time t1 is 50 us. To ensure that the lamp is not left in the "off" state for long periods of time due to the transmission of low level data, it is necessary to set a state reversal at each symbol boundary. The additional preamble is a square wave signal of 70us period 3 times.

Fig. 4(a), (b), (c), (d) are schematic diagrams of the actual encoding levels of 7-bit visible light information and oscilloscope displays, which are respectively encoded by using "Phase Shift Keying (PSK)" and "Frequency Shift Keying (FSK)" in the present invention and using hamming codes: "1100101", its source code is: "0101".

Fig. 5(a), (b), (c), and (d) are schematic diagrams of the actual encoding levels of 15-bit visible light information and oscilloscope displays, which are respectively encoded by "Phase Shift Keying (PSK)" and "Frequency Shift Keying (FSK)" according to the present invention and using hamming codes: "1110110101110", its source code bits: "11011001110".

Example (b):

the invention provides a coding mode and a visible light emitting hardware architecture which can communicate with an RFID tag with a photosensitive diode.

Visible light data coding mode:

in this scheme, the visible data encoding scheme needs to meet two requirements. First, the visible flicker is not noticeable to the human eye, and thus the frequency of the light switch is at least 80 Hz. Furthermore, the flickering of visible light should be compatible with commercial RFID systems, i.e. not interfere with conventional RFID communication. To meet the above requirement, the present embodiment proposes a "single reply level" data encoding method to generate data information with two visible light modulation mechanisms. In this embodiment, the encoding is implemented by using 7-bit and 15-bit message encoding methods and using "Frequency Shift Keying (FSK)" and "Phase Shift Keying (PSK)".

Visible light emission hardware architecture:

in this scheme, visible light emission hardware framework needs to accord with certain requirement, can see the light and need higher drive power, and MCU's GPIO driving capability can't provide the required power of LED banks, consequently needs to use drive circuit drive LED banks.

In order to meet the requirements, the scheme provides a mode of using a Darlington driving tube, which is also called a composite tube, and two triodes are connected in series to form an equivalent new triode. The amplification factor of the equivalent triode is the product of the two, so that the equivalent triode has the characteristic of very high amplification factor and is suitable for being used as a switching power supply.

The read frequency of the existing commercial RFID tags is approximately in the range of 60Hz to 140 Hz. And as the number of tags increases, the tag read rate decreases accordingly.

In the single-reply-level data encoding mode, normal reading of the tag by a commercial reader is achieved by reducing the visible light data encoding frequency to be far lower than the reading rate (60-140 Hz) of the commercial RFID tag, for example, the optical switching frequency range used in the scheme is about 10kHz to 33.33 kHz. By the mode, about 7-15 bits of optical coding information can be coded in the reply of the tag, and the original communication of the RFID is hardly interfered by the whole communication process.

The visible light encoded information is generated using a microcontroller. The delay error of the visible light coded information needs to be controlled within microsecond level. A common operation to generate microsecond level control is to use a delay function in the microcontroller, i.e. software timing. In order to improve timing accuracy, the scheme adopts a nop (noperation) instruction in an assembly language to control a precise microcontroller to wait in a specified clock period so as to realize more precise time delay control.

In the visible light coding information, in order to prevent the visible light from being in the off state all the time and being perceived by human eyes due to the continuous low level, the optical information level is coded by adopting a bipolar non-return-to-zero code mode, and a preamble code is added in each group of codes. Where "Frequency Shift Keying (FSK)" uses symbols of different frequency periods to distinguish data 0 from data 1, and "Phase Shift Keying (PSK)" uses symbols of different phases to distinguish data 0 from data 1. In addition, the scheme also adopts the Hamming code to further correct the errors.

In summary, the invention discloses a photodiode RFID tag. The tag changes the phase of a signal when the RFID tag backscatters when being irradiated by visible light coded by Frequency Shift Keying (FSK) or Phase Shift Keying (PSK) outside, so that visible light coded information is 'printed' on an EPC signal backscattered by the RFID on the premise of not influencing the normal RFID communication process, and the combination of the visible light and the RFID communication process is realized.

The photosensitive diode is used as a photosensitive component and connected in parallel at two ends of the RFID chip, so that the RFID communication process can be influenced by visible light, and the process of printing optical codes on the EPC of the RFID label is further realized.

The tag manufactured by the invention can attach the optical information to the radio frequency signal backscattered by the RFID tag only by connecting a photosensitive diode (or a photosensitive resistor) in parallel outside the chip of the existing commercial RFID tag and adopting a visible light coding mode within a certain rule range, thereby realizing the purpose of combining the visible light signal and the RFID signal.