Active frequency identification label, system and identification method

Abstract

The invention relates to an active frequency identification label, a system and an identification method. In the method, the active frequency identification label periodically and actively receives monitor signals transmitted by an active frequency identification reader writer and can detect the intensity / or the quality of the received monitor signals to judge the position distance between the active frequency identification label and the active frequency identification reader writer. The active frequency identification label has four working states. The method controls the active frequency identification label to be converted in the working states by the position distance between the active frequency identification label and the active frequency identification reader writer, so that the method realizes dynamic power management and has the advantages of long-range communication and low power consumption.

Description

technical field [0001] The invention relates to an active radio frequency identification tag, system and implementation method, in particular to an active radio frequency identification tag, system and identification method with long-distance communication and ultra-low power consumption. Background technique [0002] Radio Frequency Identification (RFID) is a non-contact automatic identification technology, which automatically identifies target objects and obtains relevant data through radio frequency signals. Writer (RFID reader, hereinafter referred to as reader), in order to achieve a long communication distance, the existing radio frequency identification system usually works in the ultra-high frequency UHF (Ultra High Frequency) frequency band such as 902MHz to 928MHz, or works in industry, science and Medical (ISM: Industrial, Scientific and Medical) 2.4GHz frequency band such as 2400MHz to 2483.5MHz frequency band, or work in a higher 5.8GHz microwave frequency band....

AI Technical Summary

Problems solved by technology

The current radio frequency identification technology usually has three schemes. The first scheme is passive radio frequency identification (passive RFID). In this scheme, the radio frequency identification tag is passive and does not contain a battery itself. When it is outside, the radio frequency tag is in a passive state. When it is within the reading and writing range of the reader, the radio frequency tag extracts the power required for its work from the radio frequency energy emitted by the reader. The data transmission from the radio frequency tag to the reader It is necessary to use the carrier wave emitted by the reader, and the reflection technology of load modulation is generally used to modulate the data of the radio frequency tag onto the carrier wave emitted by the reader and reflect it back to the reader. The disadvantage is that the communication distance is relatively short, and passive radio frequency identification can achieve The maximum communication distance is usually less than 5 meters

The second scheme is semi-passive radio frequency identification (semi-passive RFID). In this scheme, the radio frequency tag is semi-passive, it contains a battery, and the radio frequency tag does not need to extract the energy required for its work from the radio frequency energy emitted by the reader. However, the data transmission from the RF tag to the reader still needs the carrier wave emitted by the reader. The semi-passive RF tag still uses the load-modulated reflection technology to modulate the RF tag data to the reader just like the passive RF tag. The transmitted carrier wave is reflected back to the reader. Compared with the first solution, the maximum communication distance that the second solution can work has been improved, usually up to 10 meters to 15 meters, but it is still difficult to meet the requirements of 20 meters to 50 meters. Requirements for communication distance of meters or more

The third solution is active radio frequency identification (active RFID). In this solution, the radio frequency tag is active and contains a battery. The radio frequency tag does not need to extract the power required for its work from the radio frequency energy emitted by the reader. The data transmission from the tag to the reader does not need the carrier wave transmitted by the reader. The active radio frequency tag can generate the carrier wave and modulate the tag data to the carrier wave, and then transmit it to the reader through the transmitter. The transmitter is an active transmitter, so the transmitter can work at a large transmission power, and usually can reach a communication distance of 20 meters to 50 meters or more, which can fully meet the requirements of long-distance communication, but its disadvantage is that it needs battery power. High power consumption and short service life

In order to solve the problem of large power consumption of active radio frequency tags, one method in the prior art is to make active radio frequency tags work in a sleep state at ordinary times, and the active radio frequency tags receive the radio frequency signal emitted by the reader and convert it into a DC signal To judge whether to enter the coverage area of ​​the reader and wake up the radio frequency tag to enter the working state and start transmitting the tag ID information. This is mentioned in the invention patent with the application number 200710119625.x. The disadvantage of this wake-up method is that there is an external radio frequency interference signal Caused by false wake-up, if there is always an interference signal in the industrial, scientific and medical frequency band (ISM: Industrial, Scientific and Medical frequency band), the radio frequency tag will judge that it is always in the coverage area of ​​the reader and will always be in the state of false transmission, resulting in The power consumption is very large, and the battery of the tag will be exhausted quickly. In addition, the RFID tag must detect a large enough DC signal to be woken up, which requires that the RFID tag must receive a large enough RF signal from the reader. The maximum transmission signal of the reader is limited by international standards. For example, in the UHF 902MHz to 928MHz frequency band, the maximum transmission power of the reader is 4 watts, which further limits the maximum read and write distance of active radio frequency tags. less than 20 meters

Another method in the existing technology is to let the active radio frequency tag work in the periodic transmission or reception state, and the active radio frequency tag wakes up from the sleep state to transmit or receive once at a certain periodic interval and check whether it has received the read or write The response signal returned by the reader, the RF tag judges whether it has entered the coverage area of ​​the reader according to whether it has received the response signal from the reader. The working cycle will cause active radio frequency tags to frequently check whether they enter the coverage area of ​​the reader, resulting in too much power consumption, and the radio frequency tags have to use high-capacity batteries to achieve several years or longer use time

If the radio frequency tag adopts a very long working cycle, the average power consumption will become lower, but when the radio frequency tag does not receive a response signal from the reader in the previous cycle, the radio frequency tag must wait for one cycle before it can perform the next check and work The longer the period, the longer the waiting time for the RFID tag to perform the next inspection, causing the reader to read and write the RFID tag too slowly, if the RFID tag moves out of the reader coverage area before starting the next inspection , the RF tag will be missed

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