Compact Bandpass Filter with Wide Stopband and Low Radiation Using Fully-Packaged Substrate Integrated Defected Ground Structure

In this paper, a compact bandpass filter (BPF) with wide stopband and low radiation is proposed based on fully-packaged substrate integrated defected ground structure (SIDGS) resonant cell. Such resonant cell is composed of stepped-impedance defected ground structure (DGS) with top and bottom ground planes. It can not only introduce the fundamental resonance with wide stopband response, but can also suppress the radiation. To verify the mechanism, a compact BPF operating at 5.2 GHz is designed and fabricated. The measured upper-stopband is up to 16.7 GHz with a 34.7 dB rejection level. Meanwhile, the core size of the proposed filter is 9.8 mm $\times4.6$ mm (i.e., $0.32 \lambda_{g}\, \times 0.15 \lambda_{g}$, where $\lambda_{g}$ is the guided wavelength of the center frequency).