Circularly polarised filtering monopole antenna based on miniaturised coupled filter.

This Letter proposes a circularly polarised (CP) monopole antenna with filtering function, which is achieved by integrating a miniaturised coupled filter based on the bent-loop resonators. The circular-polarisation is obtained by using the falcate-shaped patch as the radiation part, and the existence of the coupled filter in the feeding line would not affect the CP radiation performances. Both numerical simulation and experimental demonstration are performed for the designed CP filtering antenna, and good agreements are obtained. The designed antenna with dimension of 70 × 75 mm² exhibits good frequency selective performances for the return loss, gain and axial ratio at 2.45 GHz with measured impedance matching bandwidth (|S11| < 10 dB) of 0.23 GHz. Such CP filtering antenna is a good candidate for the emerging application area, e.g. wearable biotelemetric devices. [ABSTRACT FROM AUTHOR]