J4 ›› 2009, Vol. 36 ›› Issue (3): 448-467.

• Original Articles • Previous Articles     Next Articles

Band-edge optimization design of the quasi-elliptic filter

ZHU Yong-zhong1,2;XIE Yong-jun1;XIE Wen-xuan3;LI Ya-feng1
  

  1. (1. Key Lab. of Antennas and Microwave Technology, Xidian Univ., Xi'an  710071, China;
    2. School of Information Eng., Chang'an Univ., Xi'an  710064, China;
    3. The National Research Inst. of Radio Spectrum Management, Xi'an  710061, China)
  • Received:2008-01-24 Revised:2008-05-18 Online:2009-06-20 Published:2009-07-04
  • Contact: ZHU Yong-zhong E-mail:bsos1980@tom.com

Abstract:

A new technique is presented for maximizing the band-edge selectivity of elliptic filters, and then the equal ripple parameter of the quasi-elliptic function can be calculated when the band-edge selectivities of the elliptic function and quasi-elliptic function are the same. The quasi-elliptic function based on the method not only keeps the bandwidth invariable, but effectively narrows the transition band. Finally, a novel quasi-elliptic microstrip filter composed of four spiral stepped-impedance resonators (SIR) is designed. Measured results show that the filter acquires 15% size reduction and 20 MHz transition band reduction, but can also effectively inhibit the second and third harmonics.

Key words: quasi-elliptic function, cross-coupling, transmission zero, band-edge characteristics, band-edge characteristics

CLC Number: 

  • TN713. 5