1、中文 2933 字 英文原文 RFID Frequency Ranges Used Because RFID systems generate and radiate electromagnetic waves, they are legally classified as radio systems. The function of other radio services must under no circumstances be disrupted or impaired by the operation of RFID systems. It is particularly impo
2、rtant to ensure that RFID systems do not interfere with nearby radio and television, mobile radio services (police, security services, industry), marine and aeronautical radio services and mobile telephones. The need to exercise care with regard to other radio services significantly restricts the ra
3、nge of suitable operating frequencies available to an RFID system (Figure 1-1). For this reason, it is usually only possible to use frequency ranges that have been reserved specifically for industrial, scientific or medical applications. These are the frequencies classified worldwide as ISM frequenc
4、y ranges (IndustrialScientificMedical), and they can also be used for RFID applications. In addition to ISM frequencies, the entire frequency range below 135 kHz (in North And South America and Japan:400 kHz) is also suitable, because it is possible to work with high magnetic field strengths in this
5、 range, particularly when operating inductively coupled RFID systems. The most important frequency ranges for RFID systems are therefore 0135 kHz,and the ISM frequencies around 6.78 (not yet available in Germany), 13.56 MHz,27.125 MHz, 40.68 MHz, 433.92 MHz, 869.0 MHz, 915.0 MHz (not in Europe),2.45
6、 GHz, 5.8 GHz and 24.125 GHz.An overview of the estimated distribution of RFID transponders at the various frequencies is shown in Figure 1-2. AVAILABLE & PRACTICAL RFID FREQUENCIES Figure1-1 The frequency ranges used for RFID systems range. The frequency ranges used for RFID systems range from the
7、myriametric range below 135 kHz, through short wave and ultrashort wave to the microwave range, with the highest frequency being 24 GHz. In the frequency range above 135 kHz the ISM bands available worldwide are preferred. Figure1-2 The estimated distribution of the global market for transponders ov
8、er the various frequency ranges in million transponder units (Krebs, n.d.) 1 Frequency range 9135 kHz The range below 135 kHz is heavily used by other radio services because it has not been reserved as an ISM frequency range. The propagation conditions in this long wave frequency range permit the ra
9、dio services that occupy this range to reach areas within a radius of over 1000 km continuously at a low technical cost. Typical radio services in this frequency range are aeronautical and marine navigational radio services (LORANC, OMEGA, DECCA), time signal services, and standard frequency service
10、s, plus military radio services. Thus, in central Europe the time signal transmitter DCF 77 in Mainflingen can be found at around the frequency 77.5 kHz. An RFID system operating at this frequency would therefore cause the failure of all radio clocks within a radius of several hundred metres around
11、a reader. In order to prevent such collisions, the future Licensing Act for Inductive Radio Systems in Europe, 220 ZV 122, will define a protected zone of between 70 and119 kHz, which will no longer be allocated to RFID systems. The radio services permitted to operate within this frequency range in
12、Germany(source: BAPT 1997) are shown in Table 1-1. Wire-bound carrier systems also operate at the frequencies 100 kHz, 115 kHz and 130 kHz. These include, for example, intercom systems that use the 220 V supply main as a transmission medium. German radio services in the frequency range 9135 kHz. The actual occupation of frequencies, particularly within the range 119135 kHz has fallen sharply. For example, the German weather service (DWD) changed the frequency of its weather fax transmissions to134.2 kHz as early as mid-1996.
