Artificial Left-handed Transmission Lines for Small Size Microwave Components: Application to Power Dividers

Abstract

In this work, the authors demonstrate that artificial transmission lines based on complementary split rings resonators (CSRRs) are useful for the design of microwave circuits with reduced size as compared to conventional implementations. The structures consist on microstrip line sections with CSRRs etched in the ground plane, underneath the conductor strip, and series capacitive gaps. By these means, a dispersive transmission medium supporting backward (or left handed) wave propagation within a certain frequency band around the CSRRs' resonance, is obtained. Key factors to achieve size reduction in functional devices are the small electrical size of the CSRRs and the possibility to control the electrical length and the image impedance of the lines over wide margins with a single cell. To illustrate the potentiality of the approach two CSRR-based power dividers were designed and fabricated. Reduced size by a factor of two is demonstrated, whilst performance is good for narrow band applications