Passive Wireless Devices Using Extremely Low to High Frequency Load Modulation

Abstract

Whereas passive wireless communication in the Ultra High Frequency (UHF) domain features long ranges of several meters in free space, systems utilizing lower frequencies in the ELF (Extremely Low Frequency) to HF (High Frequency) domain can be advantageous in environments with conductive materials or where large antennas are not prohibitive. Additionally, the operation range is well defined and can be practically restricted to several centimeters like in Near Field Communication (NFC) Standard ECMA-340 Near Field Communication Interface and Protocol (NFCIP-2) (2003), although this does not necessarily mean that communication is secure Hancke (2008). In this chapter we investigate passive wireless devices in the frequency range from almost DC to tens of Megahertz, i.e. from the ELF to the HF domain. Common abbreviations for the ITU frequency ranges are summarized in Table 1. The most common Radio Frequency Identification (RFID) systems use the LF (@125 kHz) and the HF (@13.56 MHz) bands. This chapter also considers lower frequencies.