# microstrip transmission line

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#### kezambo

##### Member level 3 what is the value of impedance in ohm for microstrip transmission line that is considered as i) open circuit (infinity ohm) and ii) short circuit ( zero ohm)

in addition of previous question.. The impedance at frequency 2GHz, 4GHz, 8GHz, 12GHz and 20GHz.

#### biff44 Your question suggests that you do not understand transmission line theory. Suggest you search open circuited stubs and short circuited stubs. The answer involves the tangent function.

#### RealAEL

##### Full Member level 6 biff44 said:
The answer involves the tangent function.

That is if the transmission line is assumed to be lossless. If it is lossy then the answer involves the hyperbolic tangent function.

#### kezambo

##### Member level 3 I want to design a harmonic resonator that will become open circuit for a certain frequency(even harmonic) and short circuit at a certain frequency (odd harmonic).
From my design simulation, at the operating freq (2GHz), Zin=50ohm. at second harmonic freq ( 4GHz), Zin = 8ohm and at third harmonic freq (6GHz) Zin=10k ohm.
again at 4th harmonic (8GHz), Zin = 9ohm and 5th harmonic (10GHz), Zin = 8k ohm.
my question is, Can I consider Zin = 8ohm and 9ohm as short circuit and also Zin= 10k ohm and 8k ohm as open circuit?

#### yendori

##### Full Member level 2 Of course you will never get 0ohms or infinite ohms.

The question is how much rejection and/or inertion loss you need at your harmonics.

#### biff44 It depends on what you are trying to do. If you are expecting the 8 ohms to filter one of the harmonics, 8 ohms to ground is not going to give you very many dB's of rejection.

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