Development of compact and wideband coupler on planar microstrip

Abstract

This project describes the development of compact and wideband coupler on planar microstrip using CST Studio Suite 2010 design tool. This project operates within 4 GHz to 8 GHz frequency band. Two designs are proposed in this project which are basic branch line coupler and branch line coupler with parallel line feeding technique. These designs use 4 ports simulation are investigated in microstrip form by using CST Studio Suite 2010 design tool. The coupler is designed using Rogers R04003 C substrate with a thickness of 0.508mm, tangent loss of 0.0027 and dielectric constant of 3.38. The results of both designs are compared in terms of return loss (S1,1), coupling (S2,1 and S3,1) and isolation (S4,1). The return loss and isolation should less than - 10dB and the coupling is -3dB±1.5dB. The measured results for branch line coupler with parallel line using VNA is not good compared to simulated results due to the fabrication error such as imperfect connector, printing the layout and etching errors.