Module Integrated Antenna With Circular Polarization for Mobile UHF RFID Reader

A module integrated antenna with circular polarization for a mobile UHF radio frequency identification reader is presented. In the proposed design, a reader module using a hybrid assemble technique is directly integrated inside the antenna. In order to compensate the degraded radiation efficiency of the reader antenna due to the module integration, a quadruple inverted-f antenna (QIFA), a type of four-port antenna like QIFA, is used. For the compact four-port antenna, we analyze the optimum matching method considering both the reflection coefficient at each port and the mutual coupling among ports simultaneously to improve the performance of the proposed module integrated antenna. Experimental results show that the proposed module integrated antenna of size 80 × 80 × 11.2 mm³ with the shielded module is well matched, and has the peak gain of 3.3 dBic and the axial ratio under 2.5 dB.