| In recent years, in order to realize the communication between person and person, person and ting, thing and thing, whenever and wherever possible, the Internet of things has become an emerging industry. However, in the Internet of things, no geographic information data is often meaningless, so the location problem of network becomes the focus of research. At present, as the support technologies of the Internet of things, the localization research of GPS, wireless sensor networks, ultra-wideband and radio frequency identification develops fast. The radio frequency identification technology, with the advantages of non-contact, non-line-of-sight, short time delay, high precision, large transmission range, low cost and easy to implement, has become a hot topic technology of positioning research of Internet of things.Linear frequency modulated (LFM) signal is an important class of non-stationary signal, is widely used in radar, sonar, communication etc. Because of the instantaneous frequency of the LFM signal with the propagation time linearly, the Doppler frequency shift interference ability is strong, and the two important parameters of the signal itself contains the position information of the target, so is very suitable for positioning, tracking the target position information. The fractional Fourier transform, as a generalized form of conventional Fourier transform, is essentially a unified time-frequency representation, which reflects the characteristics of a signal in time domain and frequency domain simultaneously, has definite physical meaning, unified description method, excellent mathematical property and efficient discrete algorithm, and is suitable for non-stationary signal processing.The key technologies of a good radio frequency identification and positioning system include positioning algorithm of high precision, high efficiency, easy implementation, for engineering application background; miniaturization, multi-band, reconfigurable reader and tag antenna; the hardware and software of embedded system design of reader and tag which is stable and reliable, low power consumption, low cost.Based on the fractional Fourier transform theory and the theory of microstrip antenna, the RFID localization algorithm based on the fractional Fourier transform, miniaturized multiband reconfigurable RFID antenna and aiming at the practical engineering application of portable algorithms for RFID technology in embedded system platform design and realization are studied, the main contributions and innovative achievements include the following:Presens an algorithm for detecting and locating a plurality of RFID tag target transmitting LFM signal by the mobile reader.The fractional Fourier transform theory is introduced into the RFID position, taking into account the uniformity of practice antenna array geometry to be inside the space equipment, array resources and correction technology limited, so combined with the practical background of non-uniform antenna array is analyzed, established the fractional Fourier domain antenna array data model, consider mobile reading writing device receives the signal Doppler frequency shift, construct spatial array rotation matrix, combined with conventional ESPRIT subspace algorithm for one-dimensional DOA multiple wideband LFM signal estimation, in the mobile reader position known conditions, according to the direction of arrival estimation, for positioning by simple geometry, simulation experiment is carried out.A multi-band monopole microstrip antenna is presented for the RFID system, but also suitable for Bluetooth, WLAN and WiMAX communication system. In the study of microstrip antenna theory, combined with the RFID antenna design requirements, this article innovates a shape of multi-band antenna with a defected ground structure. The antenna has small size, light weight, easy integration, multi-band, compact structure, easy to feed. Antenna design cycle and criterion, the simulation, the actual production and test are proposed, the test results show that the antenna meets the requirements of communication application of the RFID system, suitable for engineering application.A multi-band reconfigurable monopole microstrip antenna is presented for the RFID system, but also suitable for Bluetooth, WLAN and WiMAX communication system. In the study of microstrip antenna theory, combined with the RFID antenna design requirements, this article innovates a shape of reconfigurable antenna with a defected ground structure. The antenna has small size, light weight, easy integration, multi-band, compact structure, easy to feed. Antenna design cycle and criterion, the simulation, the actual production and test are proposed, the test results show that the antenna meets the requirements of communication application of the RFID system, suitable for engineering application.This paper puts forward one RFID embedded system platform working in high frequency range. The platform processor uses ARM Cortex-M3nuclear for STM32micro-controller, which can work in the13.56MHz frequency band, this paper designs independently and produces the hardware and software system, tests the key technologies of RFID based on this platform.This paper puts forward the other RFID embedded system platform working in ultra-high frequency and microwave frequency range. The platform processor also uses ARM Cortex-M3nuclear for STM32micro-controller, which can work in the433MHz/868MHZ/915MHz ultra-high frequency band and2.4GHz,5.8GHz microwave frequency band, this paper designs independently and produces the hardware and software system, test the key technologies of RFID based on this platform. The platform can realize the algorithm transplantation and use the antennas which are designed in this paper, so a foundation embedded platform is built for development and testing for other algorithms and antenna. |
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