A 2 GHz Quadrature Mixer Realized as One-Sided MIC on FR-4 Substrate

A 2 GHz quadrature mixer is described, realized in true microstrip technique on a cheap FR-4 substrate. Phase and amplitude errors are less than 5° and 1 dB and LO-RF isolation better than 30 dB in a 400 MHz bandwidth. The mixer can e.g. be used as a QPSK modulator and demodulator.