無線射頻辨識（Radio Frequency Identification，簡稱RFID）技術，是一種無線通訊技術，可通過無線電訊號識別特定目標並讀寫相關數據，因非接觸式且不易受干擾等優點，並運用在物流、醫療監控、移動識別、倉管、門禁管理、貨品標籤、與感測器結合之監測等各種識別相關應用。 本論文開發2.45GHz表面聲波式無線射頻標籤，在128°Y-X cut鈮酸鋰壓電基板上，透過電子束微影技術(E-beam lithography)圖案化400奈米寬之指叉電極與反射器。當指叉電極上施加電壓訊號時，壓電基板表面上激發出表面聲波，再由反射器把表面聲波反彈回指叉電極，分析反射訊號的延遲時間與相位來編碼，來開發擁有獨一識別碼之表面聲波無線射頻標籤。以低干擾、耐高溫等優點，可以替代電子式標籤，可增加更多應用範圍。 Currently, surface acoustic radio frequency identification (SAW RFID) tag received increasing attention because of several advantages such as large reliable reading range, low power consumptions, able to operate high temperature range from -40C to 400C and able to be used in harsh environment. One pair of metallic interdigital transducers (IDT) and several reflectors are on the surface of SAW tags. When an electrical signal is applied to IDT, a mechanical acoustic wave will be triggered and transferred to reflector. The time-dependent reflection waves return to IDT, and mechanical waves retransform to AC signals through direct piezoelectric effect. When different patterns of AC signals are measured and recorded, different individual tags will be identified. For SAW RFID tags, the central frequency and number of possible codes are two of most important parameters. In this study, SAW RFID device were operated in high harmonic modes at 2.45GHz. Moreover, encoding scheme was studied to increase the information capacity of SAW tags.
In this thesis, the 2.45GHz center frequency of Surface Acoustic Waves Radio Frequency Identification (SAW RFID) tag was developed. The substrate of SAW RFID was 128�Y-X cut Lithium Niobate (LiNbO3) piezoelectric substrate. The width of the IDT and reflectors were designed as 400nm to achieve center frequency of SAW tag as 2.45 GHz. The time position encoding and phase encoding were used to enhance the information capacity of SAW tags. The IDT and reflectors were deposited on the LiNbO3 piezoelectric substrate successfully by E-beam lithography and lift-off technique.