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<td>
[[File:RF160.png|thumb|500pxleft|550px|The basic transmission line circuit with three voltage probe markers.]]
</td>
</tr>
<tr>
<td>
[[File:RF161A.png|thumb|left|750px720px|The graph of the source, input and output voltages for a sinusoidal waveform with f<sub>0</sub> = 2GHz when RL = 50Ω.]]</td></tr></table> <table><tr><td>[[File:RFTUT2 5.png|thumb|left|640px|Changing the waveform in the property dialog of the voltage source.]]
</td>
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</table>
[[File:RFTUT2 5.png|thumb|500px|Changing the waveform in the property dialog of the voltage source.]]
Next, you will try out a rectangular pulse waveform as your voltage source. Open the property dialog of VS and change the waveform type to "Pulse". Set the waveform parameters as specified below:
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<td>
[[File:RFTUT2_4.png|thumb|left|750px720px|The graph of the source, input and output voltages for a pulse waveform with a period of T = 500ps when RL = 50Ω.]]
</td>
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<td>
[[File:RFTUT2 7.png|thumb|left|750px720px|The graph of the source, input and output voltages for a sinusoidal waveform with f<sub>0</sub> = 2GHz when RL = 100Ω.]]
</td>
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<td>
[[File:RFTUT2 6.png|thumb|left|750px720px|The graph of the source, input and output voltages for a pulse waveform with a period of T = 500ps when RL = 100Ω.]]
</td>
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==Analyzing a Quarter-Wave Impedance Transformer ==
[[File:RF167.png|thumb|500px|The quarter-wave impedance transformer circuit designed for 2GHz operation.]]
In RF Tutorial lesson 1, you designed a quarter-wave impedance transform to match an arbitrary resistive load to a 50Ω source. Set the length of the T-Line segment to L = λ<sub>0</sub>/4 = 37.5mm for an operating frequency of 2GHz. Also, set the characteristic impedance of the T-line to Z<sub>0</sub> = √(100.50) = 70.71Ω. Run a new transient test with the same settings as before for both cases of sinusoidal and pulse waveforms:
| v(source), v(in), v(out)
|}
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[[File:RF167.png|thumb|left|550px|The quarter-wave impedance transformer circuit designed for 2GHz operation.]]
</td>
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</table>
The results are shown and compared in the figures below:
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[[File:RFTUT2 8.png|thumb|750pxleft|720px|The graph of the source, input and output voltages for a sinusoidal waveform with f<sub>0</sub> = 2GHz when the T-Line segment acts as a quarter-wave transformer.]]</td>
</tr>
<tr>
<td>
[[File:RFTUT2 9.png|thumb|750pxleft|720px|The graph of the source, input and output voltages for a pulse waveform with a period of T = 500ps when the T-Line segment acts as a quarter-wave transformer.]]
</td>
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[[File:RFTUT2 10.png|thumb|750pxleft|720px|The spectral contents of the source voltage v(source) with a pulse waveform.]]
</td>
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[[File:RFTUT2 11.png|thumb|750pxleft|720px|The spectral contents of the input voltage v(in) with a pulse waveform.]]
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== Investigating the Effect of a Capacitive Load ==
[[File:RFTUT2_12.png|thumb|500px|The quarter-wave impedance transformer circuit with a parallel capacitor at the load.]]
In the last part of this tutorial lesson, you add a 0.1pF shunt capacitor called "CL" to the load and see its effect in the case of pulse train signal. The modified circuit is shown in the opposite figure. The impedance of the shunt capacitor at the <I>n</I>th harmonic of the source's 2GHz fundamental frequency is given by:
It can be seen that at the fundamental frequency, the capacitor has very negligible effect, but at higher harmonics, its impedance becomes comparable to the 100Ω resistive loads.
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[[File:RFTUT2_12.png|thumb|left|550px|The quarter-wave impedance transformer circuit with a parallel capacitor at the load.]]
</td>
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Run a transient test of your modified circuit with the same settings as before only for the case of pulse waveform:
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[[File:RFTUT2_13.png|thumb|750pxleft|720px|The graph of the source, input and output voltages in the quarter-wave transformer circuit with a series short stub before the load.]]
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[[File:RFTUT2_14.png|thumb|750pxleft|720px|The graph of the source, input and output voltages in the quarter-wave transformer circuit with a shunt open stub before the load.]]
</td>
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</table>
<p> </p>
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