This article from Itchen Valley Amateur Radio Club describes an interesting technique called "Norton's transform":
This results in a negative capacitor, but in a circuit where there are other parallel capacitors which can be combined, the result can be positive and thus realizable. My particular interest is in filters.
Unfortunately I can't find any other information on "Norton's transform". Of course there's Norton's theorem of which I have a simple understanding, and while I wouldn't be surprised if the two are related, it's not immediately obvious to me how.
Is there a simple explanation of how this works? And can it be generalized to provide a similar impedance transformation in other circumstances, such as with inductors, or shunt components?