Although straightforward in principle, the extension of existing designs for automatic network analyzers (ANA's) to the higher microwave frequencies is difficult in the current state of the art. What appears to be needed is a basically different approach to the microwave detection problem. One promising alternative is provided by the so-called “six-port” techniques, which eliminate the need for modulation or for frequency conversion, local oscillators, phase detectors, etc. Recent theoretical studies have provided new insights into the basic concept and lead to “five-port” configurations which require three instead of four amplitude detectors. Of particular interest is the projected measurement dynamic range of 50–60 dB corresponding to a dynamic range requirement in the amplitude detectors of a nominal 20 dB or less.