| With the development of the information and communication technology, information network will develop to ubiquitous network. Ubiquitousness will become an important feature of the information society. As an important carrier and infrastructure in the future information society, ubiquitous network has attracted the international widespread attention, and many countries have promoted the ubiquitous network construction to national informatization strategy.In this thesis, a terminal system named semi-UWB Ultra-high frequency radio frequency identification (SUUR) is presented based on the introduction of ubiquitous network. The research and design is organized as follow:from the system analysis to cell block circuits design and finally to the whole RF analog front-end circuit simulation and verification. Firstly, the system structure and the operating principle are discussed, and the relevant protocols are analyzed. Secondly, the system architecture of the passive SUUR tag IC is analyzed and designed. The specifications of the SUUR tag IC are presented. Furthermore, the system architectures of the radio frequency analog front end (RF AFE) for the passive SUUR tag are studied and designed with low-power design techniques. The RF AFE circuit includes adaptive impedance matching network, RF receiver and IR-UWB pulse generator, and so on.To realize power transfer maximization, an impedance matching network which is used to transform the tag microchip impedance to the complex conjugate of the antenna impedance is usually designed. Usually, there is a certain deviation between the real and simulation values of chip impedance, in practical applications, a network analyzer should be used to test the chip impedance and according to the test results, adjust the antenna impedance again and again, and ultimately achieve the best energy transfer. Actually, the impedance of the microchip may also vary with the received power on the chip. Therefore, if a fixed impedance matching network is used, serious mismatching may be still exist and thus create a "dead-zone" where the tag is non-responsive even the tag is deployed in the reading range (especially closed to the reader). To simplify the design of the tag antenna (50ohms can be used if the capacitance tuning range is large enough), to improve the reading area, and to eliminate "dead zones" phenomenon, in this thesis, an adaptive impedance matching network is designed to realize real-time and automatic impedance matching between the tag and antenna thus realize the maximum power transfer and the best link quality. The adaptive impedance matching network consists of two independent loops. The first loop realizes real-time measurement and automatic correction of resistance by controlling a parallel LC tuning network, whereas the second loop achieves automatic reactance compensation by controlling a series LC tuning network. In both loops, MOS varactors which are compatible with standard CMOS processing were applied as tunable elements to realize monolithic and sequential tuning. For the first loop, besides the intermediate resistance, the sign of the intermediate reactance was also detected as the second control criterion to enforce operation into a stable region. In addition, the key circuits of the matching system are designed. For different chip impedance, the adaptive impedance matching system was simulated at frequency of915MHz, and the results showed that:all the chips impedance can be quickly corrected to the target impedance. In addition, the analysis are carried out on the non-ideal characteristics of the tuning network and the tuning range of capacitance, it is indicated that the insertion loss is less than1.5dB and the system gain can be as high as2.7dB.One of the important design intentions of UWB is sharing spectrum with exiting narrow band communication systems. In order to ensure that the UWB will not interfere the narrowband communication systems, an effective way is to limit the transmit power spectral density. However, it is not enough to completely solve this problem. In this thesis, a composite pulse was generated by combining two n-th derivative Gaussian pulses with delay time of At. This pulse satisfies the characteristic of the IR-UWB pulse, and its power spectral density is the product of the power spectral density of n-th derivative Gaussian pulse with cosine function. So notch frequencies will be generated at some certain frequencies and inversely proportional to the delay time. In addition, there are one or more notch frequencies in the UWB band for a certain delay time. Therefore, it is flexible to suppress interferences on one or more narrow-band communication systems.An overall design and simulation are conducted for the RF AFE of passive SUUR tag IC based Chartered0.18μm two-poly four-metal (2P4M) CMOS process with Schottky diodes and EEPROM. The results show that the chip’s reading range is more than10m at the915MHz ISM band. The tag IC meets the requirements of the design specifications. |
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