A solid state sensor may be used to down-convert microwave signal into a low-frequency voltage or current signal, where its phase still carries the information of a measured continuous wave (CW) microwave phase. Two CW microwaves may be mixed and a solid state sensor used to rectify the mixed microwave into a direct voltage or current signal. The measurement system may include an input node for receiving a microwave signal from a source from which the output microwave is coherently split into two parts by a microwave power divider. Each part may travel in a separate path and couple at the solid state sensor. A lock-in amplifier coupled to the solid state sensor may be used to determine simultaneously a magnitude and phase of the microwave signals received from the microwave source.