Design and Measurement Method for a Ka-Band Phased-Array Radiometer Front-End

This paper presents the design of a Ka-band phased-array radiometer front-end for passive millimeter-wave imaging systems, and proposes a series of measurement methods suitable for such a highly integrated multi-channel module. The front-end integrates self-developed multifunctional active MMICs, passive multi-layer PCB circuits and mechanical horn antennas through a multichip module technology. Since multiple channels and components are integrated inside the module and cannot be separated, the measurement of some specific indicators has become difficult. In this study, by utilizing the reverse radiation and phase-shifting characteristics of the phased-array radiometer, measurement and estimation methods are proposed for return loss of antenna port and channel isolation. Finally, according to the above methods, it is found that the return loss of the antenna port is about -15$\sim$19 dB and the isolation is greater than 22 dB. The required hardware and calculation method are simple and practical. It provides an effective means for measuring the return loss of the antenna port and channel isolation of the highly integrated module.