RF-IPD directional coupler for mobile RFID handset applications

To offer RFID services on mobile phones, the RFID reader must be embedded on the handset as a chip. However, the directional coupler, a ceramic passive component used in conventional RFID readers with identical Tx/Rx carrier frequency, has been too large for cellular handset applications. A miniaturised directional coupler design for UHF RFID mobile readers using an IPD (integrated passive device) process is presented. Parallel-coupled line theory has been used for formulation of a T-type and a -type coupler. Couplers with dimensions of 1.74 1.6 mm and 1.32 1.4 mm were assembled using the IPD process.