Differential‐to‐single‐ended crossover based on dumbbell‐shaped defected ground resonators for dual‐band applications

Abstract

This article presents a novel differential-to-single-ended (DS) crossover by using two rings included of controllable frequency ratio of composite right- and left-handed (CRLH) transmission lines for dual-band applications. To reject the out-of-band differential-mode transmission coefficient, two dumbbell-shaped defected ground resonators (DGRs) are utilized over the differential transmission lines. Theoretical analysis proves that the frequency ratio can be controlled by choosing the number of designing CRLH cells and the parameter values appropriately. Also, desired electrical lengths and impedances of DGRs were obtained at the bandstop notch of differential-mode transmission coefficient by conducting common- and differential-mode analysis of lumped element equivalent circuit. To validate the proposed structure, two fabricated prototypes including the DS crossover designing at 1.8 and 4.2 GHz and separate differential lines with embedded DGRs were fabricated and measured. Measurement mixed-mode results exhibit that the fabricated crossover has great results at both frequency bands and has a good out-of-band differential insertion loss rejection.