Hello.
I posted a similar question before but I couldn't get answers from here. So, I re-describe my question for better understanding and post the updated version here
This is a simplified diagram of a complex circuit. I think we can always divide the whole circuit into two sub-circuits as A (signal emitter) and B (signal receiver) here. Sub-circuits A and B are connected by a red line and there are two individual electrical components (it could be a resistor, capacitor, inductor, transistor, some chip or whatever component) a and b in A and B respectively. a and b directly connect to the very ends of the red line. and a signal transfers from A to B. The sub-circuit A can be thought as an ideal voltage source (with zero internal impedance) with some output impedance in series connection to the source, according to Thevenin's theorem. Let's call this impedance as ZA. Similarly, individual impedances a and b are denoted as Za and Zb respectively. An equivalent impedance of B is ZB. I divide my question into two cases.
(1) The red line is rather short or a signal frequency is low so that we don't need to consider the line impedance (The circuit is treated as a lumped network). If Za ≠ Zb but ZA = ZB, then is there a signal reflection (so it is impedance mismatching) when the signal transfers from A to B ? I asked the same question to other and got an answer that a difference between ZA and ZB matters rather than impedances of individual components directly attached to the line in an impedance matching problem. I would like to confirm this one more time to make it sure to be right.
(2) The red line is long or a signal frequency is high so that we have to consider a characteristic impedance of the line Z0 (the line should be treated as a transmission line). If ZA ≠ Z0 ≠ ZB but Zin, which is a Thevenin equivalent series impedance for a circuit consisted of A and the line, is same to ZB (Zin = ZB), then is there a signal reflection (impedance mismatching) at the interface of the line and B ?
Essentially I'm asking about an importance of equivalent or total impedances in the impedance matching problem. I guess in (2), there is a signal reflection at the interface of the line and B as the line is long enough for the signal so that the signal doesn't "feel" the impedance of "far away" circuit A. I think there should be some criteria to determine an area of subcircuit which equivalent impedance have to be calculated in the matching problem.
Please clarify my confusion.
I posted a similar question before but I couldn't get answers from here. So, I re-describe my question for better understanding and post the updated version here
This is a simplified diagram of a complex circuit. I think we can always divide the whole circuit into two sub-circuits as A (signal emitter) and B (signal receiver) here. Sub-circuits A and B are connected by a red line and there are two individual electrical components (it could be a resistor, capacitor, inductor, transistor, some chip or whatever component) a and b in A and B respectively. a and b directly connect to the very ends of the red line. and a signal transfers from A to B. The sub-circuit A can be thought as an ideal voltage source (with zero internal impedance) with some output impedance in series connection to the source, according to Thevenin's theorem. Let's call this impedance as ZA. Similarly, individual impedances a and b are denoted as Za and Zb respectively. An equivalent impedance of B is ZB. I divide my question into two cases.
(1) The red line is rather short or a signal frequency is low so that we don't need to consider the line impedance (The circuit is treated as a lumped network). If Za ≠ Zb but ZA = ZB, then is there a signal reflection (so it is impedance mismatching) when the signal transfers from A to B ? I asked the same question to other and got an answer that a difference between ZA and ZB matters rather than impedances of individual components directly attached to the line in an impedance matching problem. I would like to confirm this one more time to make it sure to be right.
(2) The red line is long or a signal frequency is high so that we have to consider a characteristic impedance of the line Z0 (the line should be treated as a transmission line). If ZA ≠ Z0 ≠ ZB but Zin, which is a Thevenin equivalent series impedance for a circuit consisted of A and the line, is same to ZB (Zin = ZB), then is there a signal reflection (impedance mismatching) at the interface of the line and B ?
Essentially I'm asking about an importance of equivalent or total impedances in the impedance matching problem. I guess in (2), there is a signal reflection at the interface of the line and B as the line is long enough for the signal so that the signal doesn't "feel" the impedance of "far away" circuit A. I think there should be some criteria to determine an area of subcircuit which equivalent impedance have to be calculated in the matching problem.
Please clarify my confusion.
