Amplitude and Phase Imbalance Calibration for Space-Based Precision Direction Finding System

Abstract

Modern space systems rely heavily on the Radio Frequency Direction Finder (RF DF) for various

applications, where multichannel receivers are used to determine signal arrival angles. Accurate

angle estimation requires precise front-end and signal processing. However, high-frequency elec

tronics are susceptible to variations in electronic components due to manufacturing processes,

temperature fluctuations, and voltage fluctuations, leading to errors. To mitigate these errors,

amplitude and phase calibration of the multichannel front-end are crucial. This work presents

and implements, using a Software Defined Radio (SDR), a simplified calibration technique for a

dual-channel X-band RF front-end designed for space-based DF. The method involves applying a

calibration signal to the front-end and measuring the amplitude and phase errors in the baseband

signals using an SDR system. These measurements are used to create an error vector that is then

applied in the software domain to compensate for system imbalances. Experimental validation

was conducted within the 8.5 to 9.5 GHz X-band range, employing a modular dual-channel RF

front-end connected to a dual-channel SDR, considering two scenarios of calibration in the soft

ware domain for the entire bandwidth.