Research On Chipless RFID Sensor Design

Radio Frequency Identification(RFID)is a non-contact automatic identification technology that automatically identifies target objects through backscatter signals to obtain data.Although the sensor tag based on RFID technology has a short working distance,thanks to the adoption of backscatter modulation technology,the 'circuit structure is simple and the power consumption is low,and can work in a passive state.Its integration with Internet technology and sensor technology can be widely used in industrial automation,commercial automation and other areas of wireless sensor online monitoring.Clipless RFID tags do not contain microchip and on-chip power supply,thus have strong anti-interference ability and reliability.In recent years,chip-based RFID technology are gradually becoming a research hot spot because of its simple structure and low cost features.This article first discusses the basic theory of radio frequency identification.By analyzing frequency domain and time-domain features of backscatter signals,several chipless RFID sensor tags are designed by coating sensitive material and load sensitive resistors.1.Designed a slot-type resonant cell structure,through the slotted etching technology in the copper-clad substrate to obtain slit diffuser structure.The tag structure is divided into two units:the coding unit stores the ID information by means of slit combinations of different lengths;and the sensing unit is formed by coating the surface of the slit with the nanowire precipitating layer to sense the change of the humidity.When the humidity in the outside world changes,the backscatter signal is used to indicate that the frequency domain feature of the ID does not change,and the frequency domain feature used to express the humidity has a corresponding frequency offset,and then the reading device obtains the tag ID and External humidity information.2.A monopole UWB antenna with delay line is designed.The time-domain characteristics of the tag backscatter signal can be divided into the structure mode and the antenna mode.With different delay lines,different delay antenna modes can be obtained In order to obtain a different encoding ID.The environment information is obtained by loading the environment-sensitive resistor at the end of the delay line to change the amplitude ratio of the antenna mode and the structure mode.The temperature sensor tag is obtained by loading the thermistor and the actual test is carried out under different ambient temperatures.3.A V-type resonant structure with a load sensitive resistor is designed.By testing the horizontal and vertical electric field strength of the backscattered signal,the ID information of the tag and the resistance of the loading resistor are obtained,and the environmental information is obtained.By introducing the included angle information of the V-shaped structure,different 4-digit tag IDs are encoded under the same frequency,which increases the encoding capacity of the tag in the entire frequency spectrum and makes the tag structure more compact.