An inverted coplanar coupler with integral microstrip interfaces and bias crossover

An inverted coplanar 3 dB quadrature coupler was developed for application in hybrid power amplifiers. The structure was realized on an alumina substrate using conventional thick-film construction. It includes direct microstrip interfaces and a bias crossover, both of which support compact integration of power amplifier circuits. Designs for the PCS and UMTS communications bands achieved 0.2 dB insertion loss and directivities and return losses of nominally 25 dB.