Terminator3
Advanced Member level 3
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Complex matching is usually done using 50 ohm microstrip lines, open and closed stubs. But is it optimal? Real impedance is matched using quarterwave transformers (sqrt(z1*z2)). But if we have complex impedance which is far from 50 ohm, is it right to match it using 50 ohm stubs? But some designs do use microstrip lines with different characteristic impedance for matching. But which impedance must be chosen? The one which allows to get in desired location on Smith chart or something else?
For example, i design two matching circuit to put some complex impedance at the center of Smith Chart (50 Ohm). I can do this two ways: using 50 ohm lines, and using some N ohm lines (each line with different impedance). Will final design perform the same (i mean reflection). I think not. How to choose optimal impedance of matching stubs and phasing lines? The same resulting point on a Smith Chart can be obtained many ways, and now one more variable in this equation - characteristic impedance of matching lines...
For example, i design two matching circuit to put some complex impedance at the center of Smith Chart (50 Ohm). I can do this two ways: using 50 ohm lines, and using some N ohm lines (each line with different impedance). Will final design perform the same (i mean reflection). I think not. How to choose optimal impedance of matching stubs and phasing lines? The same resulting point on a Smith Chart can be obtained many ways, and now one more variable in this equation - characteristic impedance of matching lines...