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.
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).