Directional coupler for gigahertz frequencies, based on the coupling properties of two planar comb transmission lines

The principles of operation are given for a directional coupler based on the coupling properties of two interleaved planar comb transmission lines. It is shown that this arrangement leads to a departure from a contradirectional coupling mechanism. Results are given for an X band ?3 dB coupler, and the performance and manufacturing methods are compared with those of other high-frequency coupler designs.