A new technique for improving performance of conventional CRLH resonators using IDC/UISs with enhanced harmonic suppression in balanced dual-band BPFs

Abstract

The design of balanced filters based on composite right/left hand (CRLH) structure is well developed. Among those, few designs exist which although they provide some good responses, suffer from narrow stopbands and interdependent passbands. This paper proposes a new technique for improving the characteristics of dual-band balanced bandpass filters (B-BPFs) based on planar CRLH. Using unequal inductive stubs (UISs) attached to the interdigital capacitor (IDC) unit cell, we were able to achieve outstanding harmonic suppression and passband controllability. This structure offers higher degrees of freedom compared to conventional designs and provides better control over the filter specifications. Mathematical modeling, analysis, simulation, fabrication, and performance measurement of the proposed technique in a dual-band B-BPF are also provided. Our work resulted in an independent and controllable dual-band B-BPF with ultra-wide upper differential-mode (DM) stopband of 5.9f 1 and common-mode (CM) suppression of 40.4 and 32.6 dB for the first and second bands, respectively.