Comments on “Complex Impedance Transformers Consisting of Only Transmission-Line Sections”

Summary form only given. In the above-named work [ibid., vol. 60, no. 7, pp. 2073,2084, Jul. 2012], the problem of impedance matching using one transmission line of characteristic impedance Z
_c
and electrical length θ, inserted between two impedances, Z
_L
= R
_L
+ jX
_L
and Z
_S
= R
_S
+ jX
_S
, is analyzed. In the same paper, the allowed regions for impedances Z
_L
which may be transformed into real impedance Z is a complex impedance, an analysis on a few numerical results is presented, but the allowed regions for Z
_L
are not specified on the Smith chart. In this Letter, based on the analysis of the condition to obtain a real number for Z
_c
, it is shown that the allowed regions for Z
_L
when Z
_S
is a complex impedance may be displayed on the Smith chart, too.