Dispersive Delay Structure Based on Interdigital Capacitors With Noncommensurate Fingers

Abstract

Interdigital capacitors are key components in many RF and microwave designs such as oscillators, filters, and dispersive delay structures (DDSs). A conventional interdigital capacitor has equal length fingers and has a straight shaped figure. In this letter, we introduce an interdigital capacitor with noncommensurate fingers with a curved shape and propose a modified approach for analyzing this kind of capacitors based on N noncommensurate coupled-lines network. Moreover, this capacitor is used as unit cells to create a novel DDS for analog signal processing (ASP) applications. The proposed DDS creates extremely high group delay difference of 30 ns between 1.25 and 1.75 GHz and has a compact size of $0.6 \times 0.6 \lambda ^{\mathbf {2}}$ and low insertion loss.