Non-destructive testing of foam insulation by holographic subsurface radar

This paper describes a radar system intended for non-destructive testing of foam insulation used on cryogenic fuel tanks in space industry. The radar system consists of a radar and a two-coordinate mechanical scanner which moves the sample in the vicinity of radar antennas to form a synthetic aperture. The radar is build around an Infineon integral transceiver with nominal frequency range from 24 to 24.25 GHz. The radar has a compact size and can be used in combination with other robotic manipulators for data acquisition. The radar and the scanner are driven by a microcontroller with dedicated firmware, which is responsible for forming real-time signals for the stepper motors of the scanner and other peripheral units, such as DAC and ADC boards. The radar system is controlled by a personal computer with the user software written in Python. The component-view of the radar system is given and explained in details, sample radar images are presented and compared with the radar images of the same sample obtained with a previously created setup that featured a vector network analyzer instead of the custom radar.