Volume inspection of composite structures in aircraft radomes with FMCW terahertz radar at 100 and 150 GHz

We present a terahertz imaging system for aircraft radome inspection based on a dual-frequency FMCW radar working at center frequencies of 100 and 150 GHz and with 40 and 60 GHz bandwidth, respectively. The imaging sensor combines two all-electronic multiplier chains at the respective frequencies and is integrated in the production environment of radomes built of glass fiber-reinforced composite structures. While images acquired at the two distinct working frequencies can yield different information of possible structural defects, at the same time, a data fusion algorithm is applied combining the signals of both terahertz sensors for enhanced depth resolution by a total FMCW bandwidth of 100 GHz.