I have been trying to figure out how to apply the mathematical functions for a passive filter so that I can get component values out of it, however, I have hit a roadblock and do not understand how they are calculated.
I understand the basic concept of reactance (1/2pifC & 2pifL) and how they chance impedance as the frequencies changes, and from my reading the formulas are based upon impedance and not really values themselves right?
For my application I chose the Butterworth band pass type because it has a more linear response. It really doesn't matter though as I chose this to be educational. (146MHz, 50Ohm, 4 pole)
If I grab the formula I found 2*sin(((2*1-6283)*pi)/(2*4)) where it is a 4 pole filter, 6283 is 1Khz -> rad/s and the "1" term is the component position. I thought these were the values I should be using based upon a paper i read on it that uses 1 rad/s and so forth to generate the values in Farads and Henries, however, as soon as I change the frequency it starts outputting negative numbers.
I have checked out books such as Electronic Filter Design Handbook, ARRL handbook, Analog and digital filter design, and countless whitepaper and videos such as the MIT one.
I am at a complete loss here, and am in way over my head. I'm looking to calculate the value of the components by hand to understand the actual math behind it, not just design the filter as I am aware of countless calculators available to do the calculations. Can anyone explain how to apply the formula to get component values, or point me in the right direction? I have seen plenty of plots of the function, but again cannot figure out how to connect the math to real world component values.
Thanks!