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Finding worst case for given part value tolerances

Question asked by CeeKay on Feb 17, 2011
Hello everybody,

I'am new to Genesys, so of course I'am runnig into some difficulties. What I want to use Genesys for is to match a SAW-Filter via some type of RLC-Network to my stripline impedance and make a worst case analysis over the given tolerances for the used components. So far I reached the first goal and used Genesys to find the optimal values for my RLC Network. For that I used a optimization on the VSWR ratio of my input and output ports. Of course Genesys didn't use only standard values to reach the goal, and since I haven't found a way to limit Genesys on standard values, I corrected them manually afterwards.

Now the hard part, the worst case consideration. I want to know what happens to my impedance matching within the given tolerances of my new found optimal part values. For example the Cap has a Value of 10pF and 5% tolerance, the Resistor 1k and 1% and the inductor 4.7mH and 5%. So my first guess was to use another optimization and setting the tuneable components limits to the tolerance borders. C from 9.5 to 10.5 pF R from 990 to 1010 Ohm and L from 4,465 to 4,975 mH. And after that I'am lost. My idea was to find the maximum VSWR for my circuit using the optimization, but I just don't know how to achieve my goal. Optimization only works if you know what value you're trying to reach, but what else can I use to find the worst possible matching for my used parts?

Greetings from Germany,