Matching rf amplifier: Smith chart matching
linSmith with PI matching circuit

linSmith with PI matching circuit

I have to match 7.799 Ω+1.3158j to 50 Ω load with PI filter at 430 MHz. My advisor's advice - use pen and paper and Smith chart. But since I'm determined not to do maths on paper ever again (we have computing machines available now) then I started to search other ways out. So I read a tutorial on Impedance Matching and The Yin-Yang of Matching, really great stuff.

Then I found program called linSmith. Runs natively on linux, but requires compiling. User interface is quite good and no user manual is needed. I just typed in working frequency and starting complex impedance. Next I put in PI filter components with approximate values. It started showing all values on Smith chart. Little bit of playing around with sliders to adjust values. After couple of minutes I had values for my filter that matched impedance well and was made out of readily available components.

Next step is testing the calculated values on real circuit board. Real board and components have parasitic elements. The final values will be determined by trial and error, but the calculators give very good starting point.

Posted on 2013-11-12, 13:03 By
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