LTCC Back-scattered Polarization Duplexing Chipless RFID for Nearfield Interrogation

Chipless RFID tags can be integrated into elec-tronic circuit carriers as easily and cost-effectively as barcodes, DMC (data matrix codes) or QR-codes. The eponymous chipless-ness not only avoids assembly work and component costs, but also makes the marking of the assembly available very early in the manufacturing process. The concept presented here operates at microwave frequencies and is realized in LTCC multilayer technology. The ceramic substrate further extends the operating temperature range. Reading the tag in the near field reduces ambiguities and interference in practical use. In the presented concept, the information is encoded in the frequency domain, where the presence or absence of a null at a distinct frequency corresponds to a binary digit. By employing a wideband dual polarized antenna, the impinging RF signal is received by the tag, processed by a set of resonators used to encode the bits, and finally retransmitted with a 90° polarization rotation. For im-proving the sensitivity and precision of the code reading, a refer-ence structure can be efficiently applied. The paper presents the concept and realization of the tag, including an analysis and comparison between the numerical and measured results.