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How would you plot a resistor on a Smith Chart? - RF Cafe Forums
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mmaassel
Post subject: How would you plot a resistor on a Smith
Chart? Posted: Wed Aug 08, 2007 10:32 am
Colonel
Joined: Mon Apr 10, 2006 12:43 pm
Posts: 25
Good day. I am having
a brain freeze today.
How would you plot a resistor (an ideal
100 ohm resistor) on a Smith Chart?
Thank you for your time
and help.
Michael
Top
IR
Post subject:
Posted: Wed Aug 08, 2007 11:08 am
Site Admin
Joined:
Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello
Michael,
You should plot the resistance on the horizontal axis,
at the point where the circle of normalized resistance R=2 intersects
the horizontal axis. This gives the impedance of Zo=100+j0 - pure 100
ohm resistor.
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mmaassel
Post subject: How
would you plot a resistor on a Smith Chart?Posted: Thu Aug 09, 2007
11:51 am
Colonel
Joined: Mon Apr 10, 2006 12:43 pm
Posts: 25
Good morning. IR - Thank you for your response. In reading
your answer (and my question) I realized that I did not ask the correct
question. So let me try again.
1) I have a network that gives
me a complex impedance.
2) I now add a series (or parallel) resistor
to the network
3) How does the series/parallel resistor move the
complex impedance on the Smith Chart? Assume that the resistor is ideal.
Thank you for your time and help.
Michael
Top
IR
Post subject: Posted: Thu Aug 09, 2007 12:45
pm
Site Admin
Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello Michael,
In general
if you add a resistance you move along the arcs of the Smith Chart,
since the reacetnace remains constanct. If you have a series resistor
it will move your complex impedance along the corresponding arc towards
infinity (If your increase your resistance), i.e. on the Smith Chart
you will move towards the right side, vice versa if you decrease your
series resistor value.
For Parallel resistance it is better
to use the Smith Chart for admittances, which is a mirror view of the
''regular'' Smith Chart for Impedances. In this Smith Chart the infinity
is located at the left side of the chart. Therefore, if you increase
the parallel resistance value you will move to the left side of the
Chart on the corresponding arc.
Posted 11/12/2012
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