The effect of stub towards the coupling coefficient of 3-dB millimeterwave coupler

Investigation on the effect of stub towards coupling coefficient of 3-dB millimeterwave coupler operating at 5G band (28 GHz) has been presented in this paper. The investigation involves two different 3-dB millimeterwave coupler designs; 3-dB millimeterwave coupler with radial-shaped stub and 3-dB millimeterwave coupler with rectangular-shaped stub. Both designed coupler was accomplished using multilayer technique where the structure is formed by three layers of conductors interleaved with substrates between each conductor layer. Rogers RO4003C substrate with thickness of 0.508 mm and reflection coefficient of 3.38 was used as the substrate for designing both couplers. The results for both designed coupler then were being compared in terms of S-parameter and phase difference. The comparison shows that 3-dB millimeterwave coupler with radial-shaped stub performs better compared to 3-dB millimeterwave coupler with rectangular-shaped stub.