I thought that the question just meant a six stage filter (due to the initial mention of coupled line filter).
But now on further searching, I am given to believe that it might mean something like the hexagonal meander loop filters like below:
Shao-Guo Mo; Zhi-Yuan Yu; Long Zhang; , "Miniature dual-mode bandpass filter using hexagonal meander loop resonator," Microwave Technology and Computational Electromagnetics, 2009. ICMTCE. International Conference on , vol., no., pp.261-263, 3-6 Nov. 2009
Xin-Kai Cheng; Jun Xu; Min Zhang; , "Miniature dual-mode bandpass filters using hexagonal open-loop resonators with E-shaped stubs loading," Signals Systems and Electronics (ISSSE), 2010 International Symposium on , vol.1, no., pp.1-3, 17-20 Sept. 2010