Abstract: In a system for measuring pressure and/or temperature of a tire, reflectivity of reflectors is significantly enhanced and manufacture is significantly easier, since the system is provided with a board, an antenna provided to the board in order to send/receive a micro-wave to/from an external device, an IDT (inter-digital transducer) provided to the board and transducing the micro-wave into SAW (Surface Acoustic Wave), a waveguide part forming at least one looped channel of a polygonal shape on the board, the polygonal shape comprising a comer located at the IDT, and a plurality of reflectors provided to the at least one looped channel at comers different from the comer located at the IDT.