In order to reduce the cost of the tag and increase the code capacity of the tag

a chipless radio frequency identification（RFID） tag based on 9-shaped microstrip resonators is designed

which will make the chipless RFID tag better applied to the Internet of things（IoT）.The tag adopts a designed transceiving quadrature ultra wide band（UWB） antenna.The chipless tag is constituted by some 9-shaped microstrip resonators of different lengths and a 50 Ω microstrip transmission line

and the test result show that 10 bits encoding capacity can be obtained in the 3.98～ 5.6 GHz frequency band and 30 bits encoding capacity can be get through mixed coding of amplitude and frequency position.The tags with 5 bit and 10 bit encoding capacity are produced for experimental testing

which shows that the resonant points can be accurately identified

the resonant characteristics are obvious

the expected encoding function is realized

and the encoding density is high.This tag can effectively reduce the cost of IoT applications and is suitable for IoT projects such as commodity identification and circulation.