# How do I calculate an input impedance?

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#### isend

##### 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.

#### tyassin input impedance calculation

Hi

you will find plenty...like Wikipedia

regards

#### dhavalelectron

##### Junior Member level 1 how do i calculate 70% of 1.50%

Zin = Zo (ZL + Zo tan (βl))/(Zo+Zl tan(βl))

#### linaweku

##### Junior Member level 1 calculating input impedance

how is it? can you get the answer?

#### RFCMOS

##### Full Member level 2 equation to calculate the input impedance

Hi

You have already been given the formula to compute this impedance by dhavalelectron...

regards,

#### isend

##### Newbie level 3 find the input impedance calculate

Thank you dhavalelectron! I also found the formula in Wikipedia following tyassin's instruction. Thank you everyone!

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