A Broadband 3 dB Tandem Coupler Utilizing Right/Left Handed Transmission Line Sections

A new type of broadband 3 dB tandem coupler has been proposed featuring frequency characteristics of the resulting coupling similar to those of a classic 3 dB two-section asymmetric coupled-line directional coupler. The coupler is composed of two loosely coupled-line sections having electrical lengths close to quarter-wavelength connected by right-handed and left-handed transmission line sections. Theoretical analysis and design equations have been presented with an exemplary realization. Measurements of the manufactured tandem coupler operating at f
₀
= 1 GHz having wide operational bandwidth have been shown to validate the presented analysis.