@inproceedings{hsu_chang_kuo_2007, 
  title={Design of Dual-Band Microstrip Rat Race Coupler with Circuit Miniaturization}, 
  DOI={10.1109/mwsym.2007.380319}, 
  publisher={IEEE}, 
  author={Hsu and Chang and Kuo}, 
  year={2007}
  }