  This paper presents a new procedure for phase detector measurements that
allows the use of generators that share a 10 MHz reference oscillator but do
not synchronize in phase, in other words, quasi-synchronized RF generators. The
objectives are taking advantage of the benefits of using two generators but
recovering lower-cost generators that have worse synchronization performance
and opening the door to the possibility of using a very simple control element
based in Arduino Uno and cheaper instruments. The new procedure is
characterized by continuously alternating calibration and measurement sequences
to make up for the phase drift of quasisynchronized generators and guarantee a
maximum phase error specification (+-1 grade in this paper). Data acquisition
has been divided in two stages: measurement of detector curves without phase
reference (in-phase and phase-shifted) and measurement of reference data. All
the data is later combined to obtain correctly referenced in-phase detector
curves. The technique can be reproduced with other equivalent instrumentation.
The novel procedure that allows compensation for errors (amplitude, phase
shift, mismatching, etc.) is detailed, and its relation to the required
measurement accuracy is amply discussed. The proposed technique is applied to
characterize a phase detector based on in-phase and phase-shifted
multiplication from 3 to 8 GHz with 1 GHz step. Measurements have a final
maximum error of +-2 grade for both frequency and calibrated input power,
according to the accuracy specifications of the VNA used to calibrate the
signal distribution network, added to the +-1 grade specified in this new
procedure.
