The paper presents a complete direct design method for highpass ladder wave digital filters. The
approximation process starts by extracting the properties of the scattering matrix of the reference
highpass ladder structures. Accordingly, the transmission function is formulated in the reference
frequency domain. Then, it is designed through constructing its squared-absolute. The approximation
problem is solved by applying iterative interpolation technique such that equiripple characteristics are
obtained in the two bands. The synthesis of the resulting transmission function is carried out by
successive partial extraction of the poles at zero, corresponding to transmission zero at dc frequency from
the original impedance and successive remainder impedance functions, followed by full extraction of the
non-zero poles corresponding to transmission zeros at finite non-zero frequencies from the successive
remainder admittance functions. After obtaining the reference structure, the wave digital realization is
reached by applying three-port parallel and series adaptors. The method is applied through illustrative
examples.