Phase Compensated QPSK Demodulator with a C-Band I.F. for VSAT System Applications

A microstrip hybrid based QPSK demodulator operating with a 4GHz I.F., for simplified VSAT receive terminals, is presented. The design features independent inphase and quadrature RF arm phase trimming. Implementation is based on varactor tuned phase shifters and single balanced mixers, contained within a substrate dimension of 50 × 55mm. The approach demonstrates that accurate constellation responses can be achieved with a low tolerance assembly, constructed in a conventional microstrip form.