What Is Performance Indicators Of RFID Systems?

What Is Performance Indicators Of RFID Systems?

 

Performance Indicators of RFID Systems

 

The performance indicators of a readable and writable RFID system include the storage capacity of the radio frequency tag, working mode, data transmission speed, read/write distance, multi-tag identification capability, radio frequency carrier frequency between the radio frequency tag and antenna, connectivity of the RFID system, data carrier, state mode, and energy supply. For enterprises seeking reliable access control and asset-tracking solutions, RFID key fob suppliers and custom RFID keychain manufacturers offer durable, high-performance tags that meet industrial-grade requirements.

 

 

Storage Capacity of Radio Frequency Tags

 

There is a basic rule for systems based on memory: the storage capacity is always insufficient. Expanding the system storage capacity naturally expands the application field, which also requires more storage capacity. The storage capacity of read-only radio frequency tags is 20B, and active tags have a storage capacity of 8B to 64KB, meaning that in readable and writable radio frequency tags, it is sufficient to store several pages of text, enough to hold item lists and test data, and allow system expansion. The storage capacity of passive read/write radio frequency tags is 48 to 736B, possessing many characteristics that many active read/write systems do not have. In enterprise applications such as office buildings and parking lots, LF/HF RFID key fob wholesale suppliers provide cost-effective options with sufficient capacity for employee ID, time attendance, and vehicle access data.

 

The data volume of radio frequency tags is usually from a few bytes to several thousand bytes, but there is one exception: the 1-bit radio frequency tag, which only requires 1 bit of data storage. This type of tag enables the reader to make the following two state judgments: there is a radio frequency tag in the electromagnetic field or there is no radio frequency tag in the electromagnetic field. This requirement is completely sufficient for achieving simple monitoring or signal transmission functions. Since 1-bit radio frequency tags do not require electronic chips, the cost of the radio frequency tag can be made very low. For this reason, a large number of 1-bit radio frequency tags are used in department stores and shops for merchandise anti-theft systems. When leaving a department store with unpaid goods, the reader installed at the exit can identify the state of a radio frequency tag in the electromagnetic field and trigger the corresponding alarm. For goods that have been properly paid for, the 1-bit radio frequency tag is removed or deactivated at the checkout.

 

In RFID systems, there are two different data storage situations. In the first case, the tag can store very little data, and the accessed electronic device only prompts some basic information about the identified item. This type of data is called a unique signature (electronic tags with this type of data are very cheap and have limited uses). In the other case, the tag can store more data information, and the reader can directly obtain information from the tag without referring to a central database. This type of tag is more expensive but has a wider range of applications. This type of tag does not require as strong central processing capability as a unique signature and takes less time to work. Many enterprises now choose 125kHz/13.56MHz RFID key fob factory direct solutions to balance cost and functionality for large-scale deployment.

 

Working Mode

 

The basic working modes of radio frequency identification systems are divided into full-duplex and half-duplex systems and time-sequencing systems. In full-duplex and half-duplex systems, the response of the radio frequency tag is sent under the condition that the reader emits an electromagnetic field or electromagnetic wave. Compared with the signal of the reader itself, the signal of the radio frequency tag is very weak on the receiving antenna, so appropriate transmission methods must be adopted to distinguish the signal of the radio frequency tag from the signal of the reader. In practical applications, load modulation or backscatter modulation technology is generally used for load transmission from the radio frequency tag to the reader, loading the radio frequency tag data onto the reflected echo (especially for passive radio frequency tag systems). These reliable modulation methods are widely adopted by enterprise-grade RFID key fob manufacturers to ensure stable performance in high-traffic access control environments.

The time-sequencing system is the opposite. The reader periodically interrupts the electromagnetic field generated by radio frequency for a short time. These intervals are recognized by the radio frequency tag and used for load transmission from the radio frequency tag to the reader. In fact, this is a typical radar working mode. The disadvantage of the time-sequencing system is that when the reader sends intermittently, the energy supply of the radio frequency tag is interrupted, which must be compensated by installing a sufficiently large auxiliary capacitor or auxiliary battery.

 

 

Data Transmission Speed

 

For most data acquisition systems, speed is a very important factor. As the production cycle of today's products continues to shorten, the time required to read and update radio frequency tags is becoming shorter and shorter. Microwave systems can work at high speed, but the complexity of microwave technology itself greatly increases the construction cost of microwave systems. Data transmission speed is divided into three types: read-only speed, passive read/write speed, and active read/write speed. For commercial buildings requiring fast employee verification, high-speed RFID key fob bulk suppliers offer optimized 13.56MHz solutions that achieve sub-second identification even during peak hours.

 

1) Read-only Speed

The database transmission speed of an RFID read-only system depends on factors such as code length, radio frequency tag data transmission speed, read/write distance, carrier frequency between the radio frequency tag and antenna, and data transmission modulation technology. The transmission rate varies with the types of products in actual applications.

2) Passive Read/Write Speed

The determining factors of the data transmission speed of a passive read/write RFID system are the same as those of a read-only system, except that in addition to considering reading data from the radio frequency tag, writing data to the radio frequency tag must also be considered. The transmission speed varies with the types of products in the application.

3) Active Read/Write Speed

The determining factors of the data transmission speed of an active read/write RFID system are the same as those of a passive read/write RFID system. The difference is that passive systems require charging the capacitor on the radio frequency tag for communication. What is important is that the working speed of a typical low-frequency read/write system is only 100B/s or 200B/s. In this way, since hundreds of bytes of data may need to be transmitted at one site, the data transmission time may take several seconds, which may be longer than the time to operate the entire machine.

Whether data can be written to a radio frequency tag is another factor that distinguishes radio frequency identification systems. For simple radio frequency systems, the data of the radio frequency tag is mostly a simple number, which can be integrated during chip processing and cannot be modified by anyone. In contrast, writable radio frequency tags require a reader or a special programming device to write data.

The data writing of radio frequency tags is generally divided into two forms: unnumbered writing and numbered writing. In the current application examples in railway systems, freight car radio frequency tags all adopt the numbered writing working mode.

 

Read/Write Distance

 

The read/write range of existing read/write systems is 2.54 to 73.66 cm, and the read/write distance of read/write systems using a frequency of 13.56 MHz can reach 243.84 cm. Generally, in RFID applications, selecting an appropriate antenna can meet the needs of long-distance reading and writing.

The read/write distance of radio frequency tags varies greatly. For all kinds of tags, the greater the required distance, the more expensive the tag. RFID with a distance of a few millimeters can be embedded in paper tickets and certificates for high-speed sorting and authentication; but for the logistics industry, a distance of 3 m or more is usually required, along with the ability to quickly identify many tags. Other applications even require identification at distances of several hundred meters.

 

 

Multi-Tag Identification Capability

 

Due to the increase in identification distance, in practical applications, it is possible for multiple radio frequency tags to appear in an area at the same time, thus putting forward the requirement for simultaneous reading of multiple tags, which in turn has developed into a trend. At present, advanced radio frequency identification systems regard this multi-tag identification problem as an important feature of the system.

By properly configuring the radio frequency tags and antennas, the reader can be used to read and write multiple radio frequency tags. For example, in postal system applications, radio frequency tags are placed inside envelopes, and then thousands of letter bags with tags are stacked. When the mail bag passes through the tunnel antenna, data can be read from or written to all radio frequency tags at the same time.

 

Radio Frequency Carrier Frequency Between Radio Frequency Tag and Antenna

 

Another important feature of a radio frequency identification system is the operating frequency of the system and the reading distance. The operating frequency is closely related to the reading distance and is determined by the propagation characteristics of electromagnetic waves. Generally, the operating frequency of a radio frequency identification system is defined as the frequency of the radio frequency signal sent by the reader when identifying the tag. In most cases, it is called the reader transmission frequency (load modulation, backscatter). In any case, the transmission power of the radio frequency tag is much lower than that of the reader.

 

When selecting an RFID system, a very important consideration is the carrier frequency used for data transmission between the radio frequency tag and the antenna. The frequencies sent by radio frequency identification system readers are basically divided into four ranges: low frequency (30 to 300 kHz), high frequency (3 to 30 MHz), ultra-high frequency (300 MHz), and microwave (above 2.5 GHz). According to the range of action, the operating frequency of the radio frequency identification system is selected in a fairly wide range, with inductive coupling (0 to 1 m) and long-distance systems (1 to 10 m).

 

Connectivity of RFID Systems

 

As a branch of knowledge systems, RFID must be able to integrate existing and developing automation technologies. What is important is that the RFID system can be directly connected to a personal computer (Personal Computer, PC), programmable logic controller (Programmable Logic Controller, PLC) or industrial network interface module, thereby reducing installation costs.

RFID uses radio frequency to realize data exchange between a movable storage device and a computer or PLC. A typical RFID system includes a radio frequency tag (i.e., data storage), an antenna that communicates with the radio frequency tag, and a controller that processes communication between the antenna and the PC (or PLC) (when the antenna and controller are integrated, it is called a reader).

 

Data Carrier

 

In order to store data, three methods are mainly used: electrically erasable programmable read-only memory (EEPROM), ferroelectric random access memory (FRAM), and static random access memory (SRAM). General radio frequency identification systems mainly use electrically erasable programmable read-only memory (EEPROM). However, the disadvantage of using EEPROM is that the power consumption during the writing process is very high, and the service life is generally 100,000 writes. Recently, some manufacturers have also used ferroelectric random access memory (FRAM). Compared with electrically erasable programmable read-only memory, the write power consumption of ferroelectric random access memory is 1/100 and the write time is 1/1000. However, ferroelectric random access memory has not been widely used due to immature production processes.

For microwave systems, static random access memory (SRAM) can also be used, and the memory writes data very quickly. In order to permanently save data, an auxiliary battery is required for uninterrupted power supply.

 

State Mode

 

For programmable radio frequency tags, the internal logic of the data carrier must control the read and write operations of the reader and the request for read and write authorization. In the simplest case, it can be completed by a state machine. Using a state machine, many complex processes can be completed. However, the disadvantage of a state machine is the lack of flexibility in the functions of final programming, which means that a new chip needs to be designed. Since these changes require modification of the circuit on the chip, the cost of design change implementation is high.

The use of microprocessors has significantly improved this situation. During chip production, the database for managing applications is integrated into the microprocessor as a unified mask, and this modification cost is low. In addition, there are radio frequency tags that store data using various physical effects, including read-only surface acoustic wave radio frequency tags and 1-bit radio frequency tags that can usually be deactivated and rarely reactivated.

 

 

Energy Supply

 

An important feature of a radio frequency identification system is the power supply of the radio frequency tag. Passive radio frequency tags have no power supply of their own, so the energy required for the operation of passive radio frequency tags must be obtained from the electromagnetic field emitted by the reader. In contrast, active radio frequency tags contain batteries that provide all or part of the energy for the operation of the microchip.