Design of switched-capacitor and wave digital filters with linear phase and high amplitude selectivity

Abstract

A design technique, and the associated algorithm, are presented for selective linear-phase low-pass and high-pass sampled data filters. The resulting filter transfer functions are particularly suitable for realization as leap-frog lossless discrete integrator (LDI) switched-capacitor structures and also in wave digital form. Due to the specific form of the transfer function, the filters generally have no lumped-element counterparts. The technique leads to an optimum compromise between amplitude selectively and passband phase linearity under the restriction of a prescribed form of the transfer function, and allows the use of finite j omega -axis zeros of transmission for achieving high amplitude selectivity. The transfer functions presented are also capable of realization as distributed microwave filters, but these require the use of coupled-wire networks in the form of distributed Brune sections, if j omega -axis zeros of transmission are introduced. >