The design of a terahertz short-slot coupler with curved waveguide is proposed. A traditional short-slot coupler uses a step-like structure in order to suppress higher order modes and improve bandwidth. It becomes difficult to control the fabrication of tiny steps with the incensement of frequency especially in terahertz band. The designed coupler is composed of two curved waveguides overlapping in the middle to realize a specific coupling coefficient. Then the step-like structure can be replaced with a curved structure which is much easier to fabricate. The coupling coefficient of the coupler is 3 dB, and the variation is less than 1dB around the center frequency. The phase difference between two output ports is 90°. The isolation is greater than 10 dB in the whole working band. Measured results show high agreement with simulation predictions. The designed coupler can be widely used as feed networks of horn antenna array.
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