1. [1] R. Mongia, I. Bahl, and P. Bhartia, RF and Microwave Coupled-Line Circuits, pp.243-304, Artech House, Norwood, MA, 1999.
2. [2] N. Kinayman and M.I. Askin, Modern Microwave Circuits, pp.357-376, Artech House, Norwood, MA, 2005.
3. [3] H.-R. Ahn and B. Kim, “Toward integrated circuit size reduction,” IEEE Microw. Mag., vol.9, no.1, pp.65-75, Feb. 2008.
4. Reduced-size branch-line and rat-race hybrids for uniplanar MMIC's
5. [5] I. Toyoda, T. Hirota, T. Hiraoka, and T. Tokumitsu, “Multilayer MMIC branch-line coupler and broad-side coupler,” 1992 IEEE Microw. and Millimeter-wave Monolithic Circuits Sympo. Dig., pp.79-82, 1992.