When I come across RF circuit design books there is term know as simultaneous conjugate match but I can't understand what it is ? This was the statement I interpret with

** Optimum power gain is obtained from a transistor when yi and yo are conjugately matched to YS and YL, respectively. As was discussed in Chapter 5, however, the reverse-transfer admittance (yr) associated with each transistor tends to reflect any impedance changes made a tone port back toward the other port, causing a change in that port's impedance characteristics. This makes it very difficult to design good matching networks for a transistor while using only its input and output admittances and totally ignoring the contribution that yr makes to the transistor's impedance characteristics.Even though YL affects the input admittance of the transistor and Ys affects it's output admittance, it is still possible to provide the transistor with a simultaneous conjugate match for maximum power transfer (from source to


load) by using the following design equations: But this was the statement given in the book RF circuit design by Christopher Bowick


1 Answer 1


When driving an antenna, it might present a complex impedance such as R-jX. I.e. There is a capacitive element in the impedance. This can be cancelled by a driving impedance that includes +jX. This is called the conjugate impedance and, due to series tuning (resonance), the capacitive and added inductive reactances cancel to zero.

Hopefully, this is what you meant.

  • \$\begingroup\$ The explanation for the conjugate match is good but what about "simultaneous" \$\endgroup\$ Commented Mar 6, 2017 at 4:21
  • \$\begingroup\$ Well, if you can produce the source for the quote I'd be happy to look into it more. \$\endgroup\$
    – Andy aka
    Commented Mar 6, 2017 at 8:15
  • \$\begingroup\$ I have edited the question \$\endgroup\$ Commented Mar 6, 2017 at 14:06
  • \$\begingroup\$ Where I included the statement \$\endgroup\$ Commented Mar 6, 2017 at 14:07
  • \$\begingroup\$ @BalaSubramanian I'm a bit late on this one but i believe that the term simultaneous applies to matching the input and the output of an amplifier stage. See this document: google.com/… \$\endgroup\$
    – Andy aka
    Commented Mar 16, 2018 at 18:16

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