Propagation Characteristics and Modeling of Meshed Ground Coplanar Waveguide

Additive manufacturing (AM) is increasingly being used for the realization of microwave circuits. In this method of fabrication, conductive patterns can be printed directly without the need of a mask or subtractive techniques such as etching a metalized substrate surface. For most AM processes, the materials used for the conductive layer are the most expensive ones; hence, there is value in minimizing the conductor surface area used in a circuit. In this paper, the approach of meshed ground coplanar waveguide (MGCPW) is analyzed by simulating, fabricating, and measuring a broad set of MG geometry sizes. Furthermore, a physical-mathematical model is presented, which predicts the characteristic impedance and the capacitance per unit length of MGCPW with less than 5.4% error compared with simulated data. A set of filters is designed and fabricated in order to demonstrate the approach. The main parameter affected by meshing the ground plane is the attenuation constant of the waveguide. It is shown that 50% mesh density in the ground plane of an MGCPW line can be used with less than 25% increase in the loss. In contrast, the loss of finite ground coplanar waveguide can increase by as much as 108% when the ground size is reduced by the same factor (50%). Both 3-D printing (microdispensing) and traditional printed circuit board manufacturing are used in this paper, and most of the propagation characterization is performed at 4 GHz.