Question
What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is shorted at the far end?
Answer Options
- A) Very high impedance
- B) Very low impedance
- C) The same as the characteristic impedance of the transmission line
- D) The same as the generator output impedance
Correct Answer: A
Explanation
The Quarter-Wave Transformer principle states that a ¼-wavelength section of transmission line acts as an impedance inverter, transforming a low load impedance into a high input impedance, and vice versa. This property is crucial for matching or for creating resonant tank circuits from shorted or open lines (stubs).
When a ¼-wavelength line is shorted at the far end (Z_L \approx 0), the line inverts this short circuit, transforming it into a Very high impedance (theoretically infinite, or an open circuit) at the input end. This shorted quarter-wave stub acts as a parallel-resonant circuit.
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