Formulation of passband width for open-circuited interdigital couplers with asymmetrical cross-section

摘要

A formulation of passband width for open-circuited interdigital couplers with asymmetrical cross-section is derived utilizing a coupled line theory on c and pi modes and matching condition for a coupled quarter wavelength long. This formulation is expressed as coefficient of line capacitances per unit length, which give the transmission characteristics of couplers with axial uniformity. In this report, the relation between terminated impedances or coupling capacitance and fractional bandwidth is made clear using derived formulation.