1. About RFID
RFID is an English abbreviation of radio frequency identification. It is a non-contact automatic identification technology that automatically identifies target objects and acquires related data, identifying high-speed sports objects and can identify high-speed sports objects through RF signals. Also identify multiple labels.
The basic RFID system consists of a reader, an electronic tag (TAG), is a transponder and antenna (antenna). Its working principle is that reader transmits a specific frequency radio wave energy to Transponder, which is used to drive the Transponder circuit to send the internal data. At this time, the Reader receives the interpretation data sequentially, and the application is sent to the application. There are two coupling types of radio frequency signals between Reader and Transponder.
(1) inductor coupling. The transformer model is coupled by a high-frequency alternating magnetic field in space, which is based on electromagnetic induction. The inductor coupling method is generally suitable for the close range of radio frequency identification systems for low frequency operation. Typical operating frequencies are: 125kHz, 225kHz and 13.56MHz. The identification is less than 1m, and the typical distance is 10 ~ 20CRA.
(2) Electromagnetic reverse scattering coupling: radar principle model, emission electromagnetic wave, encounter back reflection, while carrying back to target information, based on the space propagation law of electromagnetic waves. The electromagnetic reverse scattering coupling method is generally suitable for a long-range radio frequency identification system for high frequency and microwave operation. Typical operating frequencies are: 433 MHz, 915MHz, 2.45GHz, 5.8 GHz. The identification distance is greater than 1m, and the typical distance is 3-l0m.
The reader can be read or read / write devices depending on the structure and technology used, and is the RFID system information control and processing center. The reader is usually composed of a coupling module, a transceiver module, a control module, and an interface unit. The reader and the label generally use half-duplex communication methods for information exchange, while the reader provides energy and timing to the passive transponder. In practical applications, management functions such as acquisition, processing, and remote transmission of object identification information can be further implemented by ethernet or WLAN or the like.
2. Connection example
Examples use Shandong Shen Si Electronics to verify the machine, you need to measure the working frequency of the card reader and the transmit power. Since the card reader is unbroken space to transmit RF, the signal of the card reader can be directly measured using the spectrometer and the normal RF antenna. In order to avoid the impact of spatial inglysis, a ring close field antenna can be used.
Connect the annular antenna to the spectrometer RF input (Figure 1), then receive the annular antenna to the reader induction area (as shown in Figure 2), which constitutes a simple set of RFID card reader test systems.
figure 1
figure 2
3. Signal capture and measurement
Setting the GSP-830 center measurement frequency is 13.56MHz, SPAN 5MHz, reference level 20dBm, RBW automatic (30kHz), cursor 1 opens, Trace B is updated in real time, the limit line is closed.
When the second-generation card (card reader is not read) is not placed on the card reader, the card reader continuously transmits 13.56 MHz, the power 15dBm RF signal, as shown in the red curve of Figure 3. The RF signal can also be observed with an oscilloscope, as shown in Figure 4.
image 3
Figure 4
When the second-generation card (TAG) is placed in the card reader induction zone, the TAG senses the electromagnetic field of the card reader RF transmit signal, and the payload is returned to the reader in the chip with the energy obtained by the sensing current, and the return signal is one Carrier 13.56MHz bilateral band modulation signal. After reading the information and decoding the card reader, send it to the central information system for data processing, the read speed is per second.
The GSP-830 spectrometer can also measure the return signal of TAG. The antenna coupling method is shown in Figures 1 and 2. The spectrometer center frequency is 13.56MHz, SPAN 5MHz, reference level 20dBm, RBW automatic (30 kHz), and TRACE A peak remains. The captured TAG return signal is shown in the green curve of Figure 3, and the frequency of the two sidebands is 12.7 MHz and 14.4 MHz, respectively.
4. Conclusion
The application examples of the RFID card reader are also used as a general detection scheme, which can be widely used in the RFID card reader and the active electronic tag research and development process.
Since RFID itself has a very broad field of use, such as logistics and supply management, manufacturing and assembly, air-luggage processing, email / express package processing, commercial POS machine, document tracking / library management, animal identity, exercise, Control / electronic tickets, road automatic fees, etc., so the application prospect of this set of test solutions is also very considerable.
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Source: Wiku Electronic Market Network
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