3-41
Figure 3-32.—Voltage, current, and impedance on open line.
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and the impedance is minimum. Thus, at all odd quarter-wave points, the open-ended transmission line
acts as a series-resonant circuit. The impedance is equivalent to a very low resistance, prevented from
being zero only by small circuit losses.
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minimum, and the impedance is maximum. Comparison of the line with an LC resonant circuit shows that
at an even number of quarter-wavelengths, an open line acts as a parallel-resonant circuit. The impedance
is therefore an extremely high resistance.
In addition, resonant open lines may also act as nearly pure capacitances or inductances. The
illustration shows that an open line less than a quarter-wavelength long acts as a capacitance. Also, it acts
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