Analysis of Coupled Microstrip Lines for Quad-band Equal Power Dividers/combiners

This paper presents a novel quad-band power divider with equal power division ratio. The proposed power divider is realized using two cascaded sections of dual-band transformers based on coupled microstrip lines. Limitations of using dual-band quarterwavelength transformers based on coupled lines are studied through parametric analysis to obtain useful design guidelines related to available fabrication facilities. General closed-form expressions are deduced to calculate design parameters. To verify analysis and design methodologies, a prototype of quad-band equal power divider is proposed. Compared to conventional quad-band power dividers using sections of transmission line transformers, the proposed power divider records a size reduction of about 20% and reduced parasitic effects at higher frequencies according to the usage of only two resistors instead of four with much smaller ohmic values. In addition, a quad-band power divider is proposed, fabricated and measured for 3G and 4G applications at 2.1, 2.5, 3.5, and 3.8GHz frequencies. Measured and simulated data are in very good agreement which validates the novel design.