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Additional remarks Some addtional remarks about single stub matching are set out below.
• We note that the procedure described above yields two separate solutions, of which
we have only developed one, for the matching problem. There is no simple rule for
preferring one solution to the other.
• One of the nice features of single stub matching is that the procedure always works,
because wherever on the Smith Chart the normalised load admittance yL lies, an
intersection with the g = 1 circle is guaranteed when we move from that normalised
admittance yL at constant radius around the chart. In fact two such interesections
• In the above illustration of single stub matching, we have assumed that the line to
the left of the reference plane D, the stub line of length s and the line of length l
connected to the load, all have the same charactreistic admittance Y0. In a more
general matching problem, the three lines jut mentioned can have different characteristic
admittances. Obvious adjustments to the procedure must then be made.
Principally, these adjustments consist of transforming un-normalised admittances to
normalised admittances or vice versa when one moves from a transmission line of one
characteristic impedance to a transmission line of another characteristic impedance,
because it is the un-normalised admittances which always add at a junction, but
the normalisd admittances only do so when the normalising admittances have a
• The fact that the procedure always works stands in contrast to the double stub
matching method to be discussed in the next section, which works, in its simplest
form, for some load admittances but not for others. As we will see, however, the
adoption of a more complex form of double stub matching provides a cure for that
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