Hello

I have been struggling since friday evening to understand the Formula given in a lecture-manuscript to calculate the length of a piece of Microstrip that is part of a filter.

One of the Formula in question is this one:

I have managed to find the real world counterparts of all the Variables, except

From digging through wikipedia-articles and other sources, the small Omega-Letter with a small c could be the cutoff-frequency, or the circular frequency, but using those values does not yield 11,04mm of length.

Could you guys tell me what this variable is and does in the circuit, or where my error lies? I'm rather new to this particular field of electronics and do this only as a hobby.

btw. This is the presentation where the slide is from:

http://ntuemc.tw/upload/file/20110321102525847f2.pdf