I have a board with this differential PI filter:
Say it's designed to pass signals with frequency X and bandwidth B1, and now I want to redesign the filter so that it stays with the same configuration but change it's values so that it will pass signals with frequency Y and bandwidth B2.
Luckily, I have a program that allows me to input the desired filter type (lowpass, highpass, bandpass), configuration (PI, T), frequency, and impedance. It provides me the values of the inductor and capacitors. Unfortunately, it provides me the filter as a single ended PI filter, like this:
- How do I change the values of the inductors and Capacitors that are given to me on a single ended basis (if at all), to transform the filter to a differential one?
- How do I make sure my new differential filter has the same impedance I want it to have (the single ended filter has that impedance, not the new differential filter).
- If I am limited in my choice of inductors (say I don't have the value I need L1, but I have L1+150 or L1-200), is there a way to compensate for it, for example by changing the values of the capacitors? (I can't put inductors in parallel or series).
Bonus question - how do I measure the impedance of the filter, using either ADS (advanced system design) or LTspice?