. Vì lý do này, trong cuốn sách này xung hệ thống - cho sự khác biệt từ các thủ tục khác, và không giống như văn học RFID nhất (!) - Được gọi là hệ thống thứ tự (SEQ).cho việc chuyển giao dữ liệu từ bộ thu để lựa chọn Một độc giả cho tải hệ thống điều chế RFID hoặc | This document was created by an unregistered ChmMagic please go to http to register it. Thanks Figure Principal structure of an interdigital transducer. Left arrangement of the finger-shaped electrodes of an interdigital transducer right the creation of an electric field between electrodes of different polarity reproduced by permission of Siemens AG ZT KM Munich The distance between two fingers of the same polarity is termed the electrical period q of the interdigital transducer. The maximum electroacoustic interaction is obtained at the frequency f0 the mid-frequency of the transducer. At this frequency the wavelength À0 of the surface acoustic wave precisely corresponds with the electrical period q of the interdigital transducer so that all wave trains are superimposed in-phase and transmission is maximized Reindl and Mágori 1995 . V 7- - - q 0 The relationship between the electrical and mechanical power density of a surface wave is described by the material-dependent piezoelectric coupling coefficient k2. Around k 2 overlaps of the transducer are required to convert the entire electrical power applied to the interdigital transducer into the acoustic power of a surface wave. The bandwidth B of a transducer can be influenced by the length of the converter and is . v 1111 1 1 .-I IIS Reflection of a surface wave If a surface wave meets a mechanical or electrical discontinuity on the surface a small part of the surface wave is reflected. The transition between free and metallised surface represents such a discontinuity therefore a periodic arrangement of N reflector strips can be used as a reflector. If the reflector period p see Figure is equal to half a wavelength À0 then all reflections are superimposed in-phase. The degree of reflection thus reaches its maximum value for the associated frequency the so-called Bragg frequency fe See Figure . Figure Scanning electron microscope photograph of several surface .
