Title :
High-Selectivity Low-Pass Filters With Ultrawide Stopband Based on Defected Ground Structures
Author :
Fu-Chang Chen ; Hao-Tao Hu ; Jie-Ming Qiu ; Qing-Xin Chu
Author_Institution :
Sch. of Electron. & Inf. Eng., South China Univ. of Technol., Guangzhou, China
Abstract :
Compact microstrip low-pass filters (LPFs) with ultrawide stopband based on a defected ground structure (DGS) and their design procedures are presented in this paper. A key merit of the filter configuration is that the selectivity of the LPFs can be conveniently controlled, whereas the bandwidth is fixed. The LPFs are realized using open-circuited uniform impedance stubs and stepped-impedance stubs (SISs). The position of the transmission zeros can be freely controlled by tuning the impedance ratio of the SISs. To expand the stopband, the dumbbell DGS is used to suppress the spurious passbands of the LPFs. Two demonstration filters with a cutoff frequency at 1 GHz have been designed, fabricated, and measured. The measured results indicate good performance: broad stopband (>15 fc or 20 fc) low passband insertion loss (<;0.3 dB), compact size, and sharp skirt characteristic.
Keywords :
band-stop filters; defected ground structures; low-pass filters; microstrip filters; poles and zeros; compact microstrip low-pass filters; defected ground structures; filter configuration; frequency 1 GHz; high-selectivity low-pass filters; impedance ratio; open-circuited uniform impedance stubs; sharp skirt characteristic; spurious passbands; stepped-impedance stubs; transmission zeros; ultrawide stopband; Cutoff frequency; Filtering theory; Impedance; Insertion loss; Loss measurement; Microstrip; Passband; Defected ground structure (DGS); low-pass filter (LPF); microstrip; selectivity; transmission zero; transmission zero.;
Journal_Title :
Components, Packaging and Manufacturing Technology, IEEE Transactions on
DOI :
10.1109/TCPMT.2015.2461663