Coplanar strip analysis and component development

Abstract

Uniplanar circuits offer several important advantages over traditional microstrip implementations. Easy integration of passive and active components as well as eliminating the need for through substrate vias makes uniplanar architectures very attractive. Accurate transmission line characterization is needed in order to guarantee accurate designs. The finite difference method along with newly developed absorbing boundary conditions was used to characterize the coplanar strip (CPS) transmission line. The boundary conditions significantly reduce the size of the problem that must be solved in order to obtain satisfactory convergence. As transitions between the fundamental uniplanar transmission lines are frequently necessary, broad bandwidth baluns to transform the unbalanced coplanar waveguide (CPW) to the balanced CPS line have been developed. The baluns were then used to feed a printed dipole which was characterized by transformation to an equivalent cylindrical dipole with a dielectric coating. Measured results show excellent agreement with the design specifications. The flexibility of the antenna circuit was then demonstrated by the development of a dual frequency dipole antenna.