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##### Newbie level 3

**what input impedance do i need**

This may look like a basic homework problem, but I am just learning... I have a lossless transmission line (characteristic impedance = 70 Ohm, 1.5 cm long) connected to a load of 50 Ohm. How do I calculate the input impedance of this combination? I think Zin should be dependent on the RF frequency due to the impedance mismatch; something looks like:

but I need a formula for it. Where may I find some instructional material online which I can follow to calculate the input impedance for my setup? Thank you very much.