Coherent (I/Q) Detector Performance Under Extended Drive Signal Conditions

Procedures are needed for accurate and efficient testing of large quantities of microwave amplifier/digital phase shifter devices under a wide variety of signal and environment conditions. Pulsed conditions, in particular, preclude the use of conventional automatic network analyzers. A method is investigated for applying direct detection (no local oscillator) I/Q detectors to obtain accurate phase measurements without the need for leveling input signals. The investigation focuses on identifying the minimum amount of measured calibration data required to reduce uncertainties in measured phase to less than 1°. A mathematical model of the device is developed that contains parameters that can be defined from a limited amount of calibration data. Once defined, the model then can be used to determine the device error for a wide range of signal amplitudes and phases. Data obtained with an Anaren phase discriminator is presented as an illustration of the method.