Phase Shift and Amplitude Array Measurement System Based on 360° Switched Dual Multiplier Phase Detector

Abstract

This article presents an amplitude and 360° phase shift array measurement system. The basic cell of the measurement system uses a novel amplitude and phase detector based on switched dual multipliers. The phase shift measurement is characterized using an analog phase detector (mixer), detecting a maximum range of ±90°, and a double multiplication of the input signals, in phase and phase shifted. This method broadens the frequency and amplitude range beyond other solutions that require fulfilling the quadrature condition. This method broadens the frequency and amplitude beyond other solutions requiring fulfilling the quadrature condition or phase and amplitude balance. Thus, it enables to compensate significant phase imbalance in the 90° hybrid or use amplitudes out of the range that ensures the switching operation of mixer diodes. The circuit calibration that allows compensation for errors (amplitude, phase shift, mismatching, etc.) is detailed, and its relation to the required measurement accuracy is discussed. The design can be easily extrapolated to other frequency ranges because it uses commercial RF devices available in a wide frequency range and avoids the need of crossing lines or complex 90° hybrid. A prototype with $3 \times 3$ cells has been built to evaluate various test conditions on $1 \times 3$ cell configurations that show the advantages of the procedure. It should be highlighted that the cell prototype uses devices that will be operating outside the frequency and amplitude ranges recommended by their manufacturers. A calibration from 2.6 to 6 GHz and −15 to −3 dBm was performed to evaluate the measurement errors. An analysis of the isolation between cells and different calibration configurations is performed to analyze the measurement errors. Measurements show compensation of +30°/−25° phase imbalance and 13-dB power lower than mixer manufacturer recommendation.