**Basic Characteristics of RFID**
The UHF RFID adaptive working method includes three self-learning processes. First, by placing the UHF RFID tag test board in a specific area of the antenna reading zone, the reader calculates the number of tags read at each frequency point along with the corresponding RSSI (Received Signal Strength Indicator) values. These frequency points are then filtered, and several optimal reading frequencies are selected as hopping points to improve reading efficiency. Second, by positioning the tag test board in the same area, the transmission power is adjusted and tested to determine the minimum transmit power that meets the reading requirements. This innovation helps address the challenges posed by varying application environments for fixed UHF RFID readers, resulting in better overall performance.
In an RFID system, the frequency band refers to the range of frequencies used by the reader to send, receive, and read signals from the tags via the antenna. The operating frequency of the RF tag is essentially the same as the system's operating frequency, which directly influences various aspects of system functionality. Similar to how we listen to FM radio, both the RFID tag and reader must be tuned to the same frequency to communicate effectively.
The operating frequency not only defines the working principle of the RFID system—whether it uses inductive or electromagnetic coupling—but also determines the reading distance and the complexity of implementing the tag and reader. RFID systems typically operate within the ISM (Industrial, Scientific, and Medical) bands. Common frequencies include 125 kHz, 133 kHz, 13.56 MHz, 27.12 MHz, 433 MHz, 902–928 MHz, 2.45 GHz, and 5.8 GHz.
RFID tags can be categorized based on their operating frequency: low frequency (LF), high frequency (HF), ultra-high frequency (UHF), and microwave. LF and HF tags usually operate through inductive coupling, while UHF and microwave tags use electromagnetic emission. Globally, the most widely used frequencies are 125 kHz (LF), 13.56 MHz (HF), 850–910 MHz (UHF), and 2.45 GHz (microwave). Each frequency has its own advantages and applications, so choosing the right one is crucial for effective implementation.
Low-frequency (LF) tags operate between 30 kHz and 300 kHz, with typical frequencies like 125 kHz and 133 kHz. They are passive, drawing energy from the reader’s near-field magnetic field. Their reading range is generally less than 1 meter. Applications include animal identification, tool tracking, and vehicle immobilization systems.
High-frequency (HF) tags, typically operating at 13.56 MHz, also use inductive coupling. They are often found in contactless smart cards, access control systems, and electronic tickets. Though similar to LF tags in operation, they are classified as high-frequency due to their higher bandwidth.
UHF and microwave tags operate in far-field regions, using electromagnetic waves for communication. They have longer reading ranges—up to 10 meters or more—and are ideal for logistics, inventory management, and vehicle tracking. UHF tags are especially popular in supply chain applications, such as container and rail car identification.
Microwave tags, including those at 2.45 GHz and 5.8 GHz, can be active or passive. Active tags have internal batteries and offer greater range, while passive ones rely on the reader’s signal. They are used in applications requiring long-distance and multi-tag reads, such as toll collection and medical device tracking.
Different frequency tags have unique characteristics. Low-frequency tags are cost-effective, energy-efficient, and work well in environments with water or metal. UHF tags offer fast data transfer but require careful placement to avoid interference. HF tags are ideal for short-range, mid-speed applications like ticketing and ID cards.
Currently, different countries use varying UHF frequencies. For example, Europe uses 868 MHz, while the U.S. uses 915 MHz. Japan has restrictions on UHF RFID technology. In practice, common frequencies include 13.56 MHz, 860–960 MHz, and 2.45 GHz. Short-range systems mainly use LF and HF bands, while long-range systems rely on UHF and microwave.
China has made significant progress in designing RFID chips for LF and HF bands, with HF technology close to global standards. Chips compliant with ISO 14443 Type A, Type B, and ISO 15693 have been developed and applied in projects like traffic cards and second-generation ID cards.
**UHF RFID Operating Frequency**
Understanding the operating frequency of UHF RFID is essential for optimizing system performance. The frequency determines the tag’s communication range, power consumption, and compatibility with the reader. Proper frequency selection ensures reliable and efficient identification in various applications.
Control Switches
The control switch is a special switch for process control of electrical control and thermal instrumentation. Specifically, there are positioning operation, self-resetting operation, positioning-self-resetting operation, blocking operation, positioning-blocking operation, self-resetting-positioning-locking operation and so on.
The types of control switches are:
ME Limit Switch
Micro Switch
QS5 Cam Switch
Universal Changeover Switch
Foot Switch
Proximity Switch (Sensors)
Switching Power Supply Unit
Float Switch
Weather Proof Isolating Switch
Isolating Switch and Changeover Switch
Control Switches,Float Switch,Proximity Switch,Cam Switch
Ningbo Bond Industrial Electric Co., Ltd. , https://www.bondelectro.com