Circuit Diagram

If I have two circuits like the one shown above (Rx antenna -> block1 -> block2 -> Tx antenna), where all should I add matching networks. How should I look at the impedance while doing the matching network? Let's say, if I am adding a matching network in front of Block1, do I have to find the impedance of block1+block2+antenna looking toward the output side or do I have to find the impedance of just block1?

  • \$\begingroup\$ I'm no antenna or RF guy, but why would you need to impedance match the signal between blocks? Your diagram seems to imply the receiving antenna passes a signal straight through to the transmitting antenna (though I could be wrong, remember not an RF or antenna guy). \$\endgroup\$
    – DKNguyen
    Commented Jan 29, 2020 at 19:20
  • \$\begingroup\$ If you have two circuits like the one shown above? Do you really mean the above circuit is repeated? \$\endgroup\$
    – Andy aka
    Commented Jan 29, 2020 at 19:24
  • \$\begingroup\$ No, they are circuits that do different functions. \$\endgroup\$
    – Explorer
    Commented Feb 1, 2020 at 14:36

1 Answer 1


You need to match impedance between each block and between the antennas and blocks (every connection in the diagram). As long as you do that, the impedance of block1+block2+antenna will be equal to the nominal terminal impedance of block1 itself. In this case, you can design matching networks for each connection based on the nominal impedances. However, if you omit one of the matching networks, the effective terminal impedance of block1 will no longer be equal to the nominal impedance because of reflections from block2 and antenna, and indeed it will be difficult to calculate. So matching at each connection is the universal practice of RF engineers.

  • \$\begingroup\$ In which direction should they be matched? Looking toward the output or looking toward the input? \$\endgroup\$
    – Explorer
    Commented Feb 1, 2020 at 14:37
  • \$\begingroup\$ In the direction of desired signal flow. The input impedance vs output impedance distinction is not very helpful in this domain. \$\endgroup\$ Commented Feb 4, 2020 at 1:00

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