Based on Robert Sweetman's essay in Radical Orthodoxy and the Reformed T radition. His larger target is the claim that nominalism created the Reformation (and hence ruined Christian Europe). I think he ably rebuts that thesis, but his essay does a good job in showing what the analogia entis really is.
“Being” covers the most humble individual to the most general genera. Being functions as a genus, but it is not a genus itself. It does not have anything more universal in which it can participate. Because being is not definable, it is not univocal.
Because we have to predicate “being” over everything, this points to some sameness between everything. And because there is a sameness, being cannot be equivocal. Thus, it is analogical.
Further, Thomas denies univocal knowledge (ST 1 Q. 13 a.5). When we predicate some finite thing, we predicate it in a divided way. When we predicate something of God, we are predicating it in an undivided way (since God has it immediately and simply).
Analogy is founded on the proportionality of one name to another where they participate in a common unity. The predicate of a term of both God and man is founded on some order of all creatures. In short, analogical predication posits a single essence as a middle term uniting God and creature (Sweetman 83). The dissimilarity is that the creature has a derived and diminished existence.