Phase Measurement Techniques for Detecting the Defective Elements of an Array Antenna at 28GHz

In this paper, phase measurement techniques for an array antenna designed to work at 28GHz have been presented. One is the use of a rectangular waveguide antenna capable of detecting the electric fields of the array, which is superior to those by the conventional microstrip antennas, and having the constant antenna gain. The other is the use of an electro-optic (EO) probe, which radically reduces the interference between the array antenna and the probe and, in turn, enhances the measurement accuracy. To experimentally evaluate the techniques, patched array antennas with separate and corporate feedings are fabricated on FR4 substrates and their phase characteristics are investigated over the surface of the antenna. The result shows that the phase differences in the element of the array using a waveguide antenna are within 15 degree for two different feeding cases, which is sufficiently compatible to those obtained by EO probe. This type of study is helpful to detect the defective element of the array antenna during examining mmWave modules in the earliest stages of the development process.