Research On Radio Frequency Identification And Sensing Technology Based On Backscattering

In order to satisfy people’s pursuit of using low cost,low complexity and energy-saving radio frequency identification positioning system,the Radio Frequency Identifica-tion(RFID)scheme based on backscattering is being widely studied.This scheme is easier to design and manufacture than traditional active chip tags,and tags system are wireless and passive,which can be fixed in indoor scenes and used with base station antenna for a long time without replacing.Based on the above advantages,thesis study the require-ment for chipless tag of indoor positioning system.With different types of chipless tag design as the research direction,three kinds of chipless tag are designed,and tag indoor measurement test and positioning algorithm are studied.The specific work is as follows:(1)Designed a regular triangle slot chipless tag,which is essentially a band-stop filter.Due to its good structure character,the tag will not produce too large Radar Cross Section(RCS)shift for planar waves of any polarization and pitch angle changing.Five tags are coded within 20 MHz frequency domain bandwidth.It also improves the quality factor of the tag by reducing the surface metal area,choosing the dielectric substrate,etc.It also makes a regular triangle array of the tag,which improves the recognition ability of the tag while maintaining the angle stability.However,the tag array will change its resonance pattern in the face of environmental interference.(2)Two annular tags based on hybrid coding of polarization and frequency domain are implemented.The tag unit is designed to respond differently to mutually perpendicu-larly polarized plane waves,and the relationship between the number of resonance points and the harmonic frequencies of the tag in the 50 MHz band is judged.Both tags are es-sentially resonant absorbing metasurfaces.Metal coating on the back of the dielectric substrate improves the anti-interference ability of the tag,makes the tag usable in the en-vironment,and performs array processing on the tag.In the course of measurement,the problems of raster lobe,processing accuracy and inconsistency of the array,and dielectric constant calibration of the dielectric substrate are found and solved.The results of full-wave simulation of the tag array are consistent with the actual processing measurements.It makes the design of chipless tags more accurate,with more commercial prospects and application value.(3)A frequency domain identification method is developed.By dual-band detection of backscattered signals from tags,the recognition success rate of tags in the frequency domain is more than 90%.On this basis,two different indoor test scenarios are built and validated.Time-domain signals sent and received by the vector network and horn antenna are processed through time windows,and single tag recognition and distance calculation in the scene are completed.The correctness of time-domain method and the feasibility of multi-label joint positioning are verified by comparison.