log spiral and archimedean spiral design

Hi there I am new to the site and in need of some advice. I am designing a log spiral antenna and a Archimedean spiral antenna. My upper frequency is 1GHz and my lower frequency is 300MHz. I have looked at the design equations of the log spiral or equiangular spiral but I am really confused as to what ? should be in the first equation i.e what does it start at. A lot of books and websites keep talking about polar coordiantes. Can someone please explain what phi is In the first equation ?

r1 = Roea?

r2 = Roea (?-δ)

r3 = Roea (?-π)

r4 = Roea (?-π-δ)