Synthesizing Microstrip Dual-Band Bandpass Filters Using Frequency Transformation and Circuit Conversion Technique

Xuehui GUAN  Zhewang MA  Peng CAI  Yoshio KOBAYASHI  Tetsuo ANADA  Gen HAGIWARA  

IEICE TRANSACTIONS on Electronics   Vol.E89-C   No.4   pp.495-502
Publication Date: 2006/04/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.4.495
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Advanced RF Technologies for Compact Wireless Equipment and Mobile Phones)
admittance inverter,  dual-band filter,  frequency transformation,  microstrip line,  

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A novel method is proposed to synthesize dual-band bandpass filters (BPFs) from a prototype lowpass filter. By implementing successive frequency transformations and circuit conversions, a new filter topology is obtained which consists of only admittance inverters and series or shunt resonators, and is thereby easy to be realized by using conventional distributed elements. A microstrip dual-band BPF with central frequencies of 1.8 GHz and 2.4 GHz is designed and fabricated using microstrip lines and stubs. The simulated and measured results show a good agreement and validate thereby the proposed theory.