Journal of South China University of Technology (Natural Science Edition) ›› 2011, Vol. 39 ›› Issue (7): 26-31.doi: 10.3969/j.issn.1000-565X.2011.07.005

• Electronics, Communication & Automation Technology • Previous Articles     Next Articles

Design of a Novel Tri-Band Rat Race Coupler

Lin Feng  Chu Qing-xin   

  1. School of Electronic and Information Engineering,South China University of Technology,Guangzhou 510640,Guangdong,China
  • Received:2011-01-29 Revised:2011-04-02 Online:2011-07-25 Published:2011-06-03
  • Contact: 林峰(1986-) ，男，博生生，主要从事多频以及超宽带功分器、耦合器研究． E-mail:feng.linf@mail.scut.edu.cn
  • About author:林峰(1986-) ，男，博生生，主要从事多频以及超宽带功分器、耦合器研究．
  • Supported by:

    NSFC-广东省自然科学联合基金资助项目( U0635004) ; 国家自然科学基金青年科学基金资助项目( 60801033) ;广东省自然科学基金重点项目( 07118061)

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Abstract:

As the conventional rat race coupler can only operate at the fundamental frequency and may cause odd harmonics,the design method of a novel tri-band rat race coupler is presented. In this method,the quarter-wavelength impedance transformers in the conventional rat race coupler are replaced by the Ⅱ-shaped stepped impedance ones ( ΠSITs) with four circuit topologies,which enables the proposed coupler to operate at two arbitrary frequencies and their center frequency. Then,by taking into consideration the practical realization range of transmission line impedance ( 20 ~150Ω) ,the ratio of the third operating frequency to the first one of the proposed coupler is selected from 1. 70 to 4. 10 and from 6. 60 to 12. 30. Moreover,the corresponding analytic design equations are deduced,and two microstrip 3-dB tri-band rat race couplers based on different ΠSIT circuit topologies,which respectively operate at 2. 0 /3. 9 /5. 8 GHz and 0. 9 /3. 5 /6. 1 GHz,are designed and fabricated. Simulated results accord well with the measured ones,meaning that the proposed design method is feasible.

Key words: coupler, tri-band coupler, rat race coupler, Ⅱ-shaped stepped impedance transformer