A Capacitive-Gap Coupled Terahertz Planar-Goubau-Line Power Divider

The planar Goubau line is a single-conductor waveguide with a low attenuation constant at terahertz frequencies compared with other planar waveguides. However, its single-conductor nature complicates the design of circuit elements compared to multiconductor waveguides, especially when impedance transformation is needed, like in the case of power dividers. In this article, we present a power divider for a planar Goubau line based on capacitive-gap coupled lines, providing a matched input port. A 900-GHz equal power divider was fabricated on a suspended silicon membrane and was characterized with a vector network analyzer and terahertz probes between 0.5 and 1.1 THz. Simulations and measurements are in good agreement, the measured input return loss is lower than 15 dB at the design frequency, and the average coupler loss is estimated to be lower than 1 dB when de-embedding the feeding lines.