Filter for 22.1 and 44.2MHz

We needed a filter for the 22.1MHz and 44.2MHz signals, and for this purpose we designed a top-coupled doublet filter.

Frequency	Cs	Cp	Lt	Rp	Cc
44.2MHz (ideal component values)	15.02pF	54.78pF	180nH	4K	2.86pF
44.2MHz (closest real component values)	15pF	56pF	180nH	4.02K	2.7pF
22.1MHz (ideal component values)	42.43pF	236.86pF	180nH	2K	11.45pF
22.1MHz (closest real component values)	43pF	240pF	180nH	2K	12pF

Nb: These values are optimised for 50R characteristic impedance.

Simulated performance

(click to zoom in)

Evidently, there is only very subtle difference between optimal valued components and those commercially available.