Walsh threshold matched-filtering based anti-collision for surface acoustic wave tags

Surface acoustic wave (SAW) tags are truly passive devices and do not contain any intelligence, so the question of multiple read in the reading range comes up. The paper suggests a Walsh matched-filtering method in Walsh field to distinguish the collision tags with a threshold. In advance, the code states with special sequency are selected from large possible states and the sequency variables of these tags are saved in a database. When a few tags are read simultaneously in read range, the received signal is filtered by the known sequency of single tag in database, and then these tags can be distinguished by the filtered result. Proper threshold selection improves operation speed. Experiment proves that this method is useful and reliable.     

APPLICATION OF FRACTAL THEORY IN TRANSIENT CHAOTIC SIGNAL DETECTION

Introduction　　 It is recently declared that heart period signal( HPS) is one sort of chaotic signal[1,2 ] . HPS istime variant,it changes seriously with the changeof time. So HPS is one typical sort of transientchaotic signal. In general,the signal detectedthrough electrocardiograph( ECG) is the combina-tion of heart period signal ( HPS) and noise ( NS) .For noise,the cause and background are hard toexplain,and sometimes it also changes seriouslywith the change of time.So such a prob…     

A Genetic Algorithm-Based Smart Antenna Technique for Anti-Collision of Multiple SAW ID-Tags

In the radio frequency identification (RFID) system based on surface acoustic wave (SAW) technique, some tags often locate in the field of a transceiver at the same time. These tags produce simultaneous echo signals which "collide" when they arrive back at the transceiver, which leads to difficult identification. In this paper, smart antenna technique is presented to implement anti-collision in SAW RFID system. The direction of arrivals (DOAs) are used to denote the locations of tags, and genetic algorithm (GA) is suggested to find the optimal estimates of the DOAs in complex multimodal search spaces. Once the DOAs are obtained, the array weights are formed and the signals of tags are recovered to implement decoding. The experimental results show that the GA-based smart antenna technique works well in some occasions.