Theoretical and Experimental Results of Substrate Effects on Microstrip Power Divider Designs

The effects of substrate materials on the design of microstrip power divider are investigated theoretically and experimentally. Three dielectric substrate materials, Duroid 3003, G10/FR4 epoxy Glass, and Duroid 3010, are chosen to be studied. A three-way two-stage power divider is designed at S-band frequency of 2.25？GHz and etched on each studied substrate separately. The substrate effects on the characteristics and performance of the microsrip circuits are studied taking into consideration the large difference in dielectric constant and the dissipation factor. The circuit designs presented here are analyzed using the Genesys CAD program and implemented and tested experimentally. The simulated and measured results are compared and discussed, and they indicate that significant changes in the characteristics of the microstrip power divider are observed. 1. Introduction The power divider technology has undergone a substantial change over the past decade, due to smaller size, lighter weight, potentially lower cost, high reliability, broad bandwidth capability, and function reproducibility [1, 2]. When selecting a suitable substrate material, factors to be considered in the designs of the microstrip power dividers are cost, availability, ease of machining, and etching. There are a whole range of mechanical, electrical, thermal, and chemical criteria to be taken into account [3, 4]. Most of these criteria are mechanical stability with high and low storage temperature, thermal expansion similar to that of metals, good electrical properties (homogeneity of and high electric insulation strength), chemical resistance and easy workablity with low cost [3]. There is no substrate material that simultaneously fulfils all the above requirements. The best compromise must be found for all applications [5]. The materials commonly used for microwave substrate have dielectric constants typically range from 2.0 to 10.0. Microstrip circuits designed to be fabricated on such dielectric materials will be most compact or pressed because of the wave-slowing action of the electric signal. Usually, this is an advantage, but such small size makes it difficult to fit any conventional discrete parts into microstrip layout. There are Teflon/ceramic mixture with lower dielectric constants, such as 6.0, which produce physical layer microstrip layout; this helps to alleviate the components mounting problem [6]. The present study investigates the effects of the dielectric substrate materials on the design of microstrip power dividers on which they are etched. Duroid 3003, G10/FR4 epoxy