A Comparison Between Two Monolithic C-Band 64-QAM Demodulators for Digital Radio Links

A comparison is done between two different realizations of fully monolithic 64 QAM demodulators working over the 5.9GHz - 8.5GHz range. These circuits include amplitude and phase trimming circuits, two single balanced mixers, couplers, and a quadrature phase comparator. One of the design is such that the same chip can be used either as a direct 64 QAM demodulator or a modulator. The second design comprises an active coupler at the RF port and it exhibits less conversion losses and higher RF to IF isolation. The small chip dimensions are 2.7 mm × 3.65 mm.