Compact UWB Bandpass Filter With Improved Upper-Stopband Performance

• Published in: IEEE microwave and wireless components letters 2009-01, Vol.19 (1), p.27-29
• Main Authors: Binyan Yao, Binyan Yao, Yonggang Zhou, Yonggang Zhou, Qunsheng Cao, Qunsheng Cao, Yinchao Chen, Yinchao Chen
• Format: Article
• Language: English
• Subjects: Applied sciences; Band pass filters; Bandpass filter (BPF); Bandpass filters; Circuit properties; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency; Frequency filters; High impedance; Impedance; Insertion loss; interdigital couple line; Joining; Joining processes; Microstrip filters; Microstrip lines; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Microwaves; multiple-mode resonator (MMR); Noise levels; Oscillators, resonators, synthetizers; Passband; Performance enhancement; Resonator filters; Retarding; Ultra wideband technology; ultra-wideband (UWB); upper-stopband
• ISSN: 1531-1309; 2771-957X; 1558-1764; 2771-9588
• DOI: 10.1109/LMWC.2008.2008558

In this letter, a novel ultra-wideband (UWB) bandpass filter with compact size and improved upper-stopband performance has been studied and implemented using multiple-mode resonator (MMR). The MMR is formed by attaching three pairs of circular impedance-stepped stubs in shunt to a high impedance microstrip line. By simply adjusting the radius of the circles of the stubs, the resonant modes of the MMR can be roughly allocated within the 3.1-10.6 GHz UWB band while suppressing the spurious harmonics in the upper-stopband. In order to enhance the coupling degree, two interdigital coupled-lines are used in the input and output sides. Thus, a predicted UWB passband is realized. Meanwhile, the insertion loss is higher than 30.0 dB in the upper-stopband from 12.1 to 27.8 GHz. Finally, the filter is successfully designed and fabricated. The EM-simulated and the measured results are presented in this work where excellent agreement between them is obtained.