SAW RFID with enhanced penetration depth
Some methods to enhance penetration depth further are proposed and demonstrated. A second harmonics SPUDT, new criterion of matching and high reflectivity reflector are utilized to reduce the losses of SAW tag. The enhancement of reading system including high signal processing gain and compensate the center frequency mismatch between reader and SAW tag are achieved. Furthermore, the effect of decreasing working frequency to penetration capability is demonstrated. Mediums such as dry sandy, dry soil and water are compared in the experiments in order to get the achievable penetration depth. In conclusion, the practical penetration depth is superior to the ground penetrating radar with the same center frequency range.
Programmable reflectors for SAW-ID-tags
Surface acoustic wave devices for identification systems (SAW-ID-tags or SAW wireless labels) have a large potential for future applications. We concentrate in this paper on reflective SAW-ID-tags with amplitude modulation. We use splitfinger interdigital transducers as reflecting structures. If the transducers are short circuited or capacitively loaded the reflection disappears almost entirely. On the other hand, if an open circuit or inductive load is used, the IDTs reflect incoming SAWs. The coding of the reflectors ran therefore be done once and for all by a, e.g., photolithographic process or, alternatively, programmable by external circuitry. This new possibility of dynamic programming can be used to transmit time dependent data. The present basic considerations on the design and measurements of prototypes of SAW-ID-tags on YZ-LiNbO3 at 285 MHz and 2.45 GHz
PASSIVE AND LOW-ENERGY RESEARCH AND PRACTICES-DEHUMIDIFICATION
Methods of achieving acceptable indoor conditions in overheated, temperate, and underheated humid climates are discussed and compared. Desiccants and desiccant systems utilizing solid and liquid sorbents and various low-energy mechanical systems are described and evaluated.