A miniature coupled-line-based 3-dB directional coupler using GaAs PHEMT process

A novel complementary-conducting-strip (CCS) coupled-line (CL) design is proposed to achieve compact size by applying two-dimensional layout and standard gallium-arsenide (GaAs) thin-film technology. To obtain high coupling and satisfy the design rules of GaAs process, mixed-couple mechanism with edge and broadside coupling are also used. A CCS CL-based Ka-band 3-dB directional coupler is fabricated using WIN 0.15-μm GaAs pseudomorphic high electron mobility transistor technology. Experimental results show that the proposed directional coupler can cover the entire Ka-band (26–40 GHz) with through and coupling of approximately 3.7 ± 0.25 dB, and isolation of better than 13 dB. In addition, the phase difference between the two output ports is approximately 90° ± 5°. The occupied area of the prototype (without I/O networks) is only 220 × 220 μm². © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:21–26, 2016.