On the Definition of Return Loss [Measurements Corner]

In a relatively recent paper, Bird reviewed the definitions of the term “return loss,” briefly outlined the history of the term, and gave some examples of current misuse [1]. Usually, return loss is defined in the context of the problem of characterizing the mismatch existing at the end of a transmission line loaded with a complex impedance. Other definitions are introduced as a measure of the dissimilarity between two impedances, the relation between them not being too clear.