Compact Filtering Antenna Design Combining Field and Circuit Analysis

This is the authors' abstract. We don't add key points for this paper.

A compact filtering antenna with high selectivity is proposed for wireless terminal devices. Based on the inverted-F antenna (IFA) structure, newly introduced electromagnetic couplings are elaborately utilized to produce new coupling topologies for filtering property. Therefore, two radiation nulls are realized at the lower and upper stopbands. Then, a net reactance circuit based on the equivalent circuit of IFA is designed to generate two additional radiation nulls to further improve the out-of-band suppression level. By combining the above field and circuit design techniques, a filtering antenna with four controllable radiation nulls is designed, while maintaining a compact size of 0.18λ0× 0.05λ0× 0.01λ0(whereλ0represents the wavelength in free space at 2.35 GHz). The impedance bandwidth ranges from 2.2 GHz to 2.5 GHz. The efficiency in both stopbands covering 1.9 GHz to 2.1 GHz and 2.6 GHz to 2.8 GHz is below −17 dB. In addition, the design of filtering structures has less impact on the efficiency within the working band.