Analysis of lumped-distributed coupled lines

Couplers are of fundamental importance in many RF signal processing systems. Extensive analysis has been performed to study the effects of adding lumped capacitors and resistors to the conventional microstrip coupler. The values of these lumped components were adjusted to study their effects on circuit performances. the results have yielded some highly desirable characteristics: a dramatic reduction of physical size (up to 70%), much higher coupling levels that distributed couplers, and a 180 degree phase difference between the output ports.