Gain and Phase Meter

A simple way of measuring the amplitude and phase difference between two high-frequency signals is provided by the AD8302 from Analog Devices (www.analog.com).The two input signals A and B are terminated with 50 ? and fed to the internal logarithmic demodulators. Taking the difference of the outputs leads to a voltage which represents the amplitude difference in decibels (dB); by multiplying the internal signals an output voltage proportional to the phase difference between A and B is produced.