Design of Parasitic-Element Loaded Wideband Filtering Antenna with Very Flat Gain in 30% Frequency Bandwidth

In this paper, we propose a new structure of wideband filtering antenna that realizes a very flat in-band gain in fractional bandwidth of 30%. In conventional wideband filtering antenna, a fractional bandwidth of over 20% is difficult to realize because a single patch has a lower limit of radiation Q factor. To solve the problem, we propose a new wideband filtering antenna loading a parasitic element. As an example, we design a fifth-order filtering antenna with center frequency of 4.0 GHz and fractional bandwidth of 30%. The effectiveness of the proposed filtering antenna is verified by comparing the reflection and radiation characteristics between the measured results and the EM simulated ones.