ASK modulator for RFID system using a novel variable DGS resonator

In this paper, an ASK (amplitude shift keying) modulator with DGS (defected ground structure) is proposed for 900-MHz RFID (radio frequency identification) system. Proposed variable DGS resonator with a varactor diode will be able to adjust the resonance frequency to achieve the ASK modulation. The variable resonance characteristics can be obtained by controlling capacitance of varactor diode, placed on the defected ground. In order to clarify corresponding method, we manufactured RFID system board using variable DGS resonator and measured corresponding performance. As almost 93% of extracted data from modulation index characteristic is satisfied with both EPC class-1 Gen2 Type-B and Type-C standard protocols, we obtained stable tag response of RFID system.