The Research On Passive Low-power Tag Performance Enhancement And Single Antenna Localization For IoT

Passive Io T tags have the advantages of small size,low cost and independent of the power,which are suitable for warehousing and other scenarios that require intensive deployment.By attaching passive Io T tags to goods,it can achieve long-distance query and search for goods through the tag communication and localization,which can improve the efficiency and save labor costs compared with the traditional warehousing.However,the communication distance of the traditional radio frequency identification(RFID)tag is limited,which cannot be applied to a wide range of warehousing scenarios.The reasons are as follows.First,in the downlink,the low-power restrictions make the tag demodulation circuit less sensitive,resulting in demodulation failure when the signals are weak,especially for the long-distance deployment.Second,the amplitude modulation backscattering method used by RFID tags can cause interference between the reflected signal and the original carrier at the same frequency,so that the received reflected signal is affected by the carrier,reducing the reflection distance.Although RFID systems use expensive hardware to avoid this phenomenon,but still cannot eliminate the side effects completely.Therefore,this paper proposes a demodulation scheme based on logarithmic conversion.For the logarithmic form in d Bm,the small amplitude variations of weak signals are easier to be distinguished,and the power consumption of the logarithmic conversion hardware is much lower than that of the amplifier hardware.Thus,a demodulation detector circuit with lowpower consumption and high demodulation sensitivity can be achieved.Moreover,the scattered signal and the carrier signal are in different frequency bands by using the frequency-shifted backscattering modulation,which eliminates the self-interference of the same frequency completely.Most of the existing tag localization methods are targeted at RFID and are not applicable to frequency-shifted modulated tags.In addition,most of the localization methods require dedicated equipment,such as the broadband receivers or antenna arrays.To address this problem,this paper proposed an improved localization method,which realizes the angle estimation for frequency-shifted tags and are able to apply for the commercial equipment,such as a single antenna with a single device.Experiments demonstrate that our detection circuit design improves the signal-to-noise ratio of the demodulated signal by at least 3 d B with only 0.3 ?W higher for the static power consumption,which achieves a significant increase in the demodulation circuit sensitivity by only a small power consumption.Moreover,the proposed localization method has a localization error of only 7% at a horizontal and vertical distance of 50 meters(about 70.7meters in a straight line)under the condition of single device and single antenna.