A novel design of miniaturized power divider and branch coupler using interdigital circuit

This paper presents a novel design to reduce the size of both power dividers and branch couplers using interdigital circuit. The disadvantage of planar dividers and couplers working at low frequency is their large size. To overcome it, a design method by using interdigital circuit is proposed, which consists of two interdigital capacitors and a high characteristic impedance line. The design theory is explained using an equivalent circuit model, and the equation of the theory is presented in details. One 2.4GHz Wilkinson divider based on FR4 substrate and one 1.4GHz branch coupler based on RO4003C substrate using the interdigital circuit are simulated, fabricated and measured. The results show that a size reduction of about 40% is achieved with good performance.