A new 6-18 GHz, -3 dB multisection hybrid coupler using asymmetric broadside, and edge coupled lines

The author presents an asymmetric broadside coupler which could potentially replace the Lange coupler and is shown to have superior performance. An asymmetric broadside-coupled line is used as the middle section of a three-section coupler, the two outside sections being realized by symmetric edge-coupled lines. This configuration utilizes a thin polyimide layer separating the two broadside-coupled lines which offers additional design freedom and requires no tuning or bonding, thus providing higher yield and lower manufacturing cost. The performance of two couplers, one using a Lange section and another using the asymmetric broadside section are presented and compared. An accurate numerical model for the asymmetric broadside-coupled section was developed and used to design the present coupler. Calculated and measured results which exhibit excellent agreement are presented.<>