Miniaturized Parallel Coupled-Line Filter-Antenna With Spurious Response Suppression

In this letter, a novel miniaturized integrated filter-antenna (IFA) module with dual-band filtering response is proposed. By controlling the open stub of the bandpass filter (BPF) over the antenna slot, its intrinsic band-gap characteristic helps suppressing the high-order spurious. A prototype IFA is designed and experimentally characterized. The dual-band BPF of the proposed IFA is arranged in an arc structure and is operated at 870 MHz and 2.42 GHz with fractional bandwidth 10.3% and 3.9%, respectively, leading to 62.3% size reduction compared to the conventional structure. The impedance bandwidth of the slot antenna is 3.9% with center frequency of 4.06 GHz. The antenna slot provides a good suppression of the spurious passband at 3.57 GHz around 17.3 dB.