A comprehensive explanation on the high quality characteristics of symmetrical octagonal spiral inductor

Conventional non-symmetrical spiral inductor, which is commonly used in GaAs technology, has limited achievable quality factor when used in silicon LC tanks circuit. As a result, the research of symmetrical, arbitrarily-shaped spiral inductor for silicon technology becomes very important and challenging. However, the detailed mechanism of how the symmetrical, arbitrarily-shaped spiral inductor can achieve a high quality factor is still a mystery. In this paper, we attempt to give a detailed explanation on how the symmetrical, arbitrarily-shaped spiral inductor helps to improve the overall quality factor over that of a traditional, non-symmetrical arbitrarily-shaped spiral inductor. Experimental results are presented to verify our theory. It is hope with this new understanding, alternate forms of symmetrical spiral inductor of high quality factor can be derived.