Compensated 3-dB lange directional coupler in suspended microstrip technique

An investigation on the design of Lange couplers in suspended microstrip technique is presented. The chosen realization technique allows for minimization of total losses in the coupler. The theoretical analysis shows that the Lange couplers can be compensated with the proper selection of dielectric stratification of the substrate, and by the proposed compensation both isolation and impedance match of the coupler can be enhanced. The presented theoretical investigation has been supported by measurements of a 3-dB directional coupler exhibiting good electrical properties and low total losses.