Simple and adaptive UHF RFID modulator using defected ground structure and practical measurement on reader‐to‐tag communication

An extended work on DGS modulator, which was presented before on Microwave and Optical Technology Letters Society, shall be adaptive performance and practical implementation and measurement. A DGS modulator is motivated from three benefits that can be obtained from defected ground structure; an extensive resonance, size reduction, and excellent stopband characteristic. An extensive resonance via a microstrip ground plane configuration, which includes a varactor diode bridging microstrip transmission line with variable capacitance provision that can be controlled, gives on/off switching and its attenuation level (OOK is a 100%, and which less than 100% can be ASK) that plays the key role of the ASK and OOK modulation process. A varactor diode is under control of a micro control unit that can be controlled by user interface software; therefore, user can monitor communication states while each operational sequence of a varactor diode can be controlled. Sharper phase and more precise data modulation can be achieved after several tuning works and practical trials. A modulation index (about 90–93%) with stable tag responses over the target bands (860–960 MHz, centered 912 MHz) was verified through the practical measurements on the RFID reader communication using ASK. And when a modulation index was nearly 99% (∼98.8%), this is considered to be an OOK. Overall radio communications are with EPC class‐1 Gen2 Type‐B and Type‐C passive tags, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2646–2651, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23780