3-dB Branch-line coupler using coupled line radial stub with no restriction on coupling power

Abstract

Investigation on the design of coupled line radial stub towards 3-dB branch-line coupler (BLC) operating for fourth generation (4G) Long Term Evolution (LTE) at 3.5 GHz has been presented in this paper. The investigation involves different parameter value of the radius of radial stub and coupled line length at the series and shunt arm of 3-dB BLC designs specifically without restriction on the coupling power performance. The designed BLC was simulated using Rogers RO4003C substrate with thickness of 0.508 mm and dielectric constant of 3.38. The results for proposed radial stub BLC were being compared in terms of S-parameter and phase difference. The comparison shows that 3-dB BLC with radial shaped stub optimized to 79% reduction compared to conventional design without having to compromise the performance result especially with no restriction on the coupling power.