Wideband RFID communication device with customized protocol

Abstract

The invention discloses a broadband RFID (Radio Frequency Identification) communication device with a custom protocol, and belongs to the field of radio frequency identification. The device is designed on a circuit board, comprises two transmitting signal chains, two receiving signal chains and four low-dropout voltage-stabilized power supplies, covers a frequency band of 0-3 GHz, and comprises four mainstream RFID working frequency bands of low frequency, high frequency, ultrahigh frequency and microwave. The transmitting chain adopts a discrete device to carry out switching frequency mixing, and the carrier frequency, the data transmission rate and the coding mode can be modified through a controller to support a user-defined communication protocol; the receiving chain obtains data through envelope detection, a level threshold value of a comparator circuit can be set for waveform shaping, and received data are decoded through a controller or transmitted to an upper computer. The RFID reader-writer is a novel RFID tag receiving and transmitting communication device oriented to a user-defined communication protocol, is different from an RFID reader-writer designed based on a standard RFID protocol radio frequency chip, and has great engineering value.

Description

Technical Field

[0001] The present invention relates to the field of RFID communication, and in particular to a wide-band RFID communication device with a custom protocol. Background Art

[0002] Radio Frequency Identification (RFID) is a contactless automatic identification technology that uses the transmission characteristics of wireless electromagnetic signals and the principle of spatial coupling to automatically identify target objects. It is one of the important Internet of Things technologies. Based on RFID technology, logistics information management can be strengthened through object identification; through information integration, intelligent information mining can be formed, so it is widely used in fields such as material management.

[0003] A closed-loop RFID system includes at least two parts: an RFID tag and an RFID reader. Currently, most RFID readers on the market are designed with integrated radio frequency chips and can only exchange data with RFID tags that support standard protocols (such as ISO / IEC18000-6C). Based on this, the present invention provides a wide-band RFID communication device with a customizable protocol, which has great engineering significance for the testing and application of new RFID tags with customizable communication protocols. Summary of the invention

[0004] The purpose of the present invention is to provide a broadband transceiver communication device for a new type of RFID tag with a custom communication protocol, which is different from a reader / writer based on a standard RFID protocol radio frequency chip.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A wide-band RFID communication device with a custom protocol includes two transmitting signal chains, two receiving signal chains and four low-dropout regulated power supplies, covering a frequency band of 0-3 GHz, wherein the two transmitting signal chains are a high-frequency transmitting signal chain and a low-frequency transmitting signal chain, and the two receiving signal chains are a high-frequency receiving signal chain and a low-frequency receiving signal chain, wherein the transmitting signal chain uses discrete devices for switch mixing, and the carrier frequency, data transmission rate and encoding method can be modified by a controller to support a custom communication protocol; the receiving signal chain uses envelope detection to acquire data, and waveform shaping is performed by setting the level threshold of a comparator circuit, and the received data is decoded by the controller or transmitted to a host computer.

[0006] In the above technical solution, the high-frequency transmitting signal chain includes a controller, a frequency synthesizer, a high-frequency mixing circuit, a gain control circuit, and a high-frequency power amplifier circuit, and the signal is transmitted to the high-frequency transmitting antenna; the low-frequency transmitting signal chain includes a controller, a low-frequency mixing circuit, and a low-frequency power amplifier circuit, and the signal is transmitted to the low-frequency transmitting antenna; the low-frequency receiving signal chain includes a low-frequency power amplifier circuit, a low-frequency detection circuit, and a controller, and its signal originates from the low-frequency receiving antenna; the high-frequency receiving signal chain includes a high-frequency power amplifier circuit, a bandpass filter, a gain control circuit, a high-frequency detection circuit, and a controller, and its signal originates from the high-frequency receiving antenna.

[0007] Furthermore, the device's transmit signal chain, receive signal chain and low-dropout regulated power supply are designed on the same circuit board, without the need for module assembly, and the four signal chains on the board can all run individually or simultaneously. The device is connected to the external RFID antenna through an SMA connector and exchanges data with external devices through the USB interface and UART interface.

[0008] Furthermore, the high-frequency transmission signal chain and the high-frequency reception signal chain are designed to cover a frequency band of 50 MHz-3GHz, and the carrier is generated by a frequency synthesizer, supporting a 0.01 MHz step resolution; the modulated signal can be manually adjusted for gain using a potentiometer, or automatic gain control can be achieved using a program. The low-frequency transmission signal chain and the low-frequency reception signal chain operate in the 0-50 MHz frequency band, and the carrier is generated by a timer inside the controller.

[0009] Furthermore, the mixing circuit in the transmitting signal chain uses discrete devices for switch mixing, where the carrier frequency, data transmission rate, and encoding method can be modified by the controller to support custom communication protocols, supporting a maximum transmission rate of 2Mbps; the modulation depth can be modified by replacing resistors, supporting a maximum modulation depth of 99.6%. The mixing circuit in the high-frequency transmitting signal chain uses an RF switch for channel control, which can realize the switching or shutting down of two independent mixing channels, and supports time division multiplexing of the transmitting signal chain.

[0010] Furthermore, the receiving signal chain uses envelope detection to acquire data, and uses a comparator circuit for waveform shaping, and sets the data level threshold through program control of the digital-to-analog converter. The high-frequency receiving signal chain can use a potentiometer to manually set the data level threshold, and its detection circuit can output the RMS value of the received signal power, which is sampled by the ADC inside the controller, and the RGB-LED color tone is adjusted using the sampled value to achieve the received signal strength indication. The power amplifier circuit in the low-frequency transmitting signal chain adopts a cascade structure of a pre-stage power amplifier + a post-stage power amplifier, in which the pre-stage power amplifier is used for the carrier signal and the post-stage power amplifier is used for the modulation signal.

[0011] Furthermore, the receiving signal chain supports frequency conversion and frequency hopping RFID signal reception and is not limited by same-frequency reception.

[0012] Compared with the existing equipment, the beneficial effects of the present invention are: In the present invention, the transmitting and receiving signal chains and the power supply are designed on the same circuit board, and there is no need for module assembly. The four signal chains can run separately or simultaneously, realizing the rapid construction of the RFID test platform and the discrete testing of transmitting and receiving. Discrete devices are used for switch mixing, wherein the carrier frequency, data transmission rate, and encoding method can be modified by the controller to support custom communication protocols, which is different from the reader / writer using an integrated standard RFID protocol radio frequency chip, and is suitable for the testing and application of new RFID tags with custom communication protocols. The operating frequency of the equipment can be switched among four types of RFID operating frequency bands: low frequency, high frequency, ultra-high frequency, and microwave. The operating frequency can also be customized within the wide frequency band range of 0-3 GHz, and the receiving signal chain supports frequency conversion and frequency hopping RFID signal reception, and is not limited by the same frequency reception. The above three features provide a great degree of freedom for the application of the present invention in the field of RFID communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a complete working diagram of the RFID system; Figure 2 It is a hardware block diagram of a wide-band RFID communication device with a custom protocol of the present invention; Figure 3 It is a test software block diagram of a wide-band RFID communication device with a custom protocol of the present invention; Figure 4 It is a circuit board design line drawing of a specific example of a wide-band RFID communication device with a custom protocol of the present invention; Figure 5 It is a working measured waveform diagram of a specific example of a frequency band RFID communication device of the custom protocol of the present invention. DETAILED DESCRIPTION

[0014] In order to facilitate those skilled in the art to better understand the technical solution of the present invention, the present invention is now further described in conjunction with the accompanying drawings and specific implementation methods. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0015] Figure 1 The figure shows a complete RFID system working diagram, including a host computer, an RFID reader / writer, an antenna, and an RFID tag. The wide-band RFID communication device with a custom protocol provided by the present invention belongs to an RFID reader / writer, which interacts with the host computer through a wired connection and interacts with the RFID tag wirelessly through an independent transmitting antenna and receiving antenna. The arrows in the figure point to the direction of data flow.

[0016] Figure 2The figure shows the hardware block diagram of the signal chain part of the wide-band RFID communication device of the custom protocol of the present invention, including two transmission signal chains and two reception signal chains, and the data flow is shown by the arrows in the figure. The two transmission signal chains are a high-frequency transmission signal chain and a low-frequency transmission signal chain, and the two reception signal chains are a high-frequency reception signal chain and a low-frequency reception signal chain, wherein: The high-frequency transmission signal chain consists of a controller, a frequency synthesizer, a high-frequency mixing circuit, a gain control circuit, and a high-frequency power amplifier circuit. The microcontroller (MCU) controls the frequency synthesizer to generate a specified frequency carrier, which is mixed with the encoded data generated by the MCU through the I / O port, and the signal gain is controlled by manually adjusting the potentiometer or the MCU's built-in digital-to-analog converter (DAC). Finally, the power is amplified by the high-frequency power amplifier circuit and the signal is loaded on the transmitting antenna.

[0017] The low-frequency transmission signal chain consists of a controller, a low-frequency mixing circuit, and a low-frequency power amplifier circuit; its carrier and data are generated by the MCU, and no gain control is performed. The signal after mixing and power amplification is directly loaded onto the transmitting antenna.

[0018] The high-frequency receiving signal chain consists of a high-frequency power amplifier circuit, a bandpass filter, a gain control circuit, a high-frequency detection circuit, and a controller. The signal is received through the antenna, amplified, and then filtered through a bandpass filter. The signal gain is then controlled by manually adjusting the potentiometer or the DAC built into the MCU, and input into the high-frequency detection circuit for envelope detection and root mean square (RMS) detection. The high-frequency detection circuit includes a waveform shaping circuit based on a comparator. The MCU controls the external DAC to set the level threshold of the waveform shaping. Finally, the shaping data is input into the MCU for timer capture and decoding, and transmitted to the host computer. The RMS value is used by the MCU to control the RGB-LED color tone for receiving signal indication.

[0019] The low-frequency receiving signal chain is composed of a low-frequency power amplifier circuit, a low-frequency detection circuit, and a controller; it does not perform bandpass filtering and gain control, and the signal after power amplification and detection shaping is directly input into the MCU for capture, decoding, and transmission.

[0020] Figure 3 The test software block diagram of the wide-band RFID communication device of the custom protocol of the present invention is shown. The device is powered on to start the controller initialization and signal chain initialization. The signal chain initialization includes the carrier frequency setting, mixing channel setting, gain setting and other related configurations. The universal asynchronous receiver and transmitter (UART) interrupt is turned on, and the while main loop is entered to continuously run the RFID encoding transmission, receiving decoding and data uploading tasks. When receiving UART data, the MCU interrupts the current task and executes the UART interrupt callback function instead. The signal chain is configured according to the valid instruction, and the original task is restored after the execution is completed.

[0021] Figure 4 The figure shows a specific embodiment of the present invention, in which the circuit board (PCB) design line drawing of the RFID communication device is a 4-layer board design with a size of 50 mm × 100 mm. The device is connected to the external RFID antenna through the SMA connector on the right, which are: high-frequency receiving antenna port, low-frequency receiving antenna port, low-frequency transmitting antenna port, and high-frequency transmitting antenna port from top to bottom; data is exchanged with the host computer through the USB interface and UART interface on the left.

[0022] Figure 5 Shown Figure 4 The measured working waveform of the device is as follows: the test point is connected to the high-frequency transmitting antenna port, the carrier frequency is set to 900 MHz, the data transmission rate is set to 100 kbps, and the encoding method adopts non-return-to-zero encoding.

Claims

1. A wide-band RFID communication device with a custom protocol, characterized in that: It includes two transmitting signal chains, two receiving signal chains and four low-voltage difference regulated power supplies, covering the frequency band of 0-3 GHz. The two transmitting signal chains are a high-frequency transmitting signal chain and a low-frequency transmitting signal chain, and the two receiving signal chains are a high-frequency receiving signal chain and a low-frequency receiving signal chain. The transmitting signal chain uses discrete devices for switch mixing, and the carrier frequency, data transmission rate, and encoding method can be modified by the controller to support custom communication protocols; the receiving signal chain uses envelope detection to obtain data, and waveform shaping is performed by setting the level threshold of the comparator circuit. The received data is decoded by the controller or transmitted to the host computer.

2. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: in: A high-frequency transmission signal chain includes a controller, a frequency synthesizer, a high-frequency mixing circuit, a gain control circuit, and a high-frequency power amplifier circuit; the signal is transmitted to a high-frequency transmission antenna; A low-frequency transmission signal chain includes a controller, a low-frequency mixing circuit, and a low-frequency power amplifier circuit; the signal is transmitted to a low-frequency transmission antenna; A low-frequency receiving signal chain includes a low-frequency power amplifier circuit, a low-frequency detection circuit, and a controller; the signal of the low-frequency receiving signal is derived from a low-frequency receiving antenna; A high-frequency receiving signal chain includes a high-frequency power amplifier circuit, a bandpass filter, a gain control circuit, a high-frequency detection circuit, and a controller; the signal of the high-frequency receiving signal is derived from a high-frequency receiving antenna; The four low voltage dropout regulated power supplies respectively supply power to the four signal chains.

3. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: The transmitting signal chain, receiving signal chain and low voltage dropout regulated power supply are designed on the same circuit board, without the need for module assembly, and the four signal chains support individual or simultaneous operation.

4. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: The transmitting signal chain and the receiving signal chain are connected to an external RFID antenna via an SMA connector, and data is exchanged with external devices via a USB interface and a UART interface.

5. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: The high-frequency transmission signal chain and the high-frequency reception signal chain cover a frequency band of 50 MHz-3 GHz and support a step resolution of 0.01 MHz; the low-frequency transmission signal chain and the low-frequency reception signal chain operate in a frequency band of 0-50 MHz.

6. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: The mixing circuit in the transmitting signal chain supports a maximum transmission rate of 2Mbps; the modulation depth is modified by replacing resistors, and supports a maximum modulation depth of 99.6%; the mixing circuit in the high-frequency transmitting signal chain uses an RF switch for channel control, which can realize switching or shutting down of two independent mixing channels, and supports time division multiplexing of the transmitting signal chain.

7. The wide-band RFID communication device with a custom protocol according to claim 2, characterized in that: The gain control circuits in the high-frequency transmitting signal chain and the high-frequency receiving signal chain use a potentiometer to perform manual gain adjustment, or use a program to implement automatic gain control.

8. The wide-band RFID communication device with a custom protocol according to claim 2, characterized in that: The receiving signal chain adopts envelope detection to acquire data, and uses a comparator circuit to perform waveform shaping, and sets the data level threshold by controlling the digital-to-analog converter; wherein the detection circuit of the high-frequency receiving signal chain can output the RMS value of the received signal power, which is sampled by the ADC inside the controller, and the sampling value is used to adjust the RGB-LED color tone to realize the received signal strength indication.

9. The wide-band RFID communication device with a custom protocol according to claim 2, characterized in that: The low-frequency power amplifier circuit in the low-frequency transmission signal chain adopts a cascade structure of a front-stage power amplifier and a rear-stage power amplifier, wherein the front-stage power amplifier is used for the carrier signal and the rear-stage power amplifier is used for the modulation signal.

10. The wide-band RFID communication device with a custom protocol according to claim 1, characterized in that: The receiving signal chain supports frequency conversion and frequency hopping RFID signal reception and is not limited by the same frequency reception.

Images