Tri-band microstrip bandpass filter using input/output cross coupling

Abstract

A compact tri-band bandpass filter using input/output cross coupling is proposed. Three passbands can be adjusted by changing the characteristic impedance of the T-shaped structure with a shorted stub. The three passbands are designed to operate at 1.85, 3.5 and 5.2 GHz based on the T-shaped structure. Four transmission zeros are used to realise high selectivity for the passbands. Good agreement can be observed between the measured and simulated results.

Keywords:

• tri-band
• bandpass filter
• T-shaped
• characteristic impedance
• transmission zero

Acknowledgements

This work is supported by the National Natural Science Foundation of China (60971013) and the 2010 Innovative Projects for Graduates of Jiangsu Province (CX10B_125Z).