RF standards for short-range

摘要

The term "short-range device" (SRD) refers to a device capable of wireless communications over a relatively short distance-from just a few centimeters up to a few kilometers. Several wireless standards defining the communications processes for such devices exist, with new standards continuing to evolve. Constraints Governments impose restrictions on the use of the frequency spectrum. Figure 1 shows the UHF (300-MHz to 3-GHz) ISM unlicensed frequency bands available in different parts of the world. As the figure shows, no common unlicensed ISM band is available below 2.4 GHz, although some RF transceivers will support operation across several of these sub-1-GHz bands. The Analog Devices ADF7020/-1, for example, supports operation from 135 to 950 MHz. Many designs use proprietary communications protocols in this frequency range.