Disk-gap discontinuity in a coaxial transmission line

Some filter realizations require a series capacitance that is difficult to implement when using coaxial cable technology. The difficulty in using this topology for a series capacitor stems from the fact that small internal radii produce small series capacitances, unless a very small gap size is used. The sensitivity of the series capacitance to errors in gap size increases with smaller gaps and makes this topology useless in this respect. To alleviate this problem a topology is proposed which consists of two additional disks added to the gap, thus providing a new parameter to adjust, the disk radius, that together with the gap size permits a better (less sensitive) method to synthesize a given series capacitance