Design of wideband CPW bandpass filters using phase comparison method and oblique air bridges

ABSTRACT

This work presents two wideband coplanar-waveguide bandpass filters using open-circuited stubs (Design 1) and short-circuited stubs (Design 2), respectively. The electrical lengths of stubs were accurately determined by a phase comparison method. In Design 1, a spurious resonance was found at the high band edge of the passband. The problem was solved by introducing oblique air bridges to ruin the undesired resonance path for the suppression of the spurious resonance. Design 1 achieves bandwidth of 38.1% and low insertion loss of 0.7 dB. Another CPW filter, Design 2, was constructed with short-circuited stubs for compact size, which can achieve a very wide bandwidth of 70.8% and insertion loss of 0.9 dB.

KEYWORDS:

• Coplanar-waveguide (CPW) filter
• oblique air bridges
• phase comparison method
• stub-type filter
• wideband bandpass filter

Acknowledgement

This study was partially supported by the Ministry of Science and Technology, under project MOST 109-2221-E-182-047 and Chang Gung University (BMRP 903), Taiwan, R.O.C.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Huayan Jin

Huayan Jin is with the Key Laboratory of RF Circuits & System of Ministry of Education, Hangzhou Dianzi University, Hangzhou, 310018, China.

Chiao-Yi Chien

Chiao-Yi Chien is with the Department of Electronic Engineering, Chang Gung University, Tao-yuan 333, Taiwan.

Eric S. Li

Eric S. Li is with the Department of Electronic Engineering, National Taipei University of Technology, Taipei, Taiwan.

Chung-Yi Li

Chung-Yi Li is with the Department of Electronic Engineering, Chang Gung University, Tao-yuan 333, Taiwan.

Kuo-Sheng Chin

Kuo-Sheng Chin is with the Department of Electronic Engineering, Chang Gung University, Tao-yuan 333, Taiwan.