RFID reader pad using free access transmission line

Abstract

In this paper, we propose a RFID reader pad using free access transmission line. Free access transmission line using microstrip bandpass filter has wideband transmission characteristic and stable coupling with the receiving antenna in fixed direction. To obtain a stable coupling in any antenna direction, we propose the diamond shaped transmission line and circularly polarized antenna. The proposed line and antenna are effective as two-dimensional RFID reader and tag.