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To unlock the full potential of composite materials, reliable measurement methods during and after their manufacturing are required. Established measuring methods are commonly based on ultrasound or thermographic imaging techniques and offer only a limited usability. A promising alternative to the aforementioned methods are millimeterwave-based systems. It has already been demonstrated that such systems can provide a tomographic representation of composite materials, enabling the detection, localization, and classification of critical defects within the component. The tomographic millimeter-wave imaging system presented here is operating in the W band and is packaged for the operation in a manufacturing environment. For this purpose, it is enclosed by a dustproof housing and can be mounted on an industrial robot, which enables the development of an automated measurement procedure during and after the manufacturing process of composite materials. The direct integration of the measurement system into the manufacturing process allows for early-stage fault detection and classification, which is essential for the production of high-quality, high-performance, and highly reliable composite materials.Index Terms-Microwave/millimeter wave sensors, composite materials, millimeter-wave (mmW) radar, nondestructive testing, radar imaging, robot programming.

The modeling, design and experimental evaluation of both a 400-GHz transmitter and receiver submillimeter-wave monolithic integrated circuit (S-MMIC) is presented in this paper. These S-MMICs are intended for a radar-based system in the aforementioned operating frequency. The transmitter occupies a total chip area of 750 × 2750 µm 2 . It consists of a multiplier-by-four, generating the fourth-harmonic of the WR-10 input signal, which drives the integrated WR-2.2 power amplifier. The latter has an output-gate width of 128 µm. The receiver S-MMIC, 750 × 2750 µm 2 , consists of a multiplier-by-two, providing the second harmonic of the WR-10 input signal for the local-oscillator port of the subsequent integrated sub-harmonic mixer. The radio-frequency port of the latter, connects via a Lange coupler to a WR-2.2 low-noise amplifier (LNA). All the components included, are processed on a 35-nm InAlAs/InGaAs metamorphic high-electron-mobility transistor integrated-circuit technology, utilizing two-finger transistors and thin-film microstrip lines (TFMSLs). The modeling approach of the amplifier cores and the respective design decisions taken are listed and elaborated-on in this work. Accompanying measurements and simulations of the transmitter and receiver are presented. The individual components of the aforementioned S-MMICs, are characterized and the results are included in the paper. The state-of-the-art, for S-MMIC based circuits operating in the WR-2.2 band, is set by the LNA, on one side, spanning an operational 3-dB bandwidth (BW) of 310 to 475 GHz, with a peak gain of 23 dB and, on the other side, by the final transmitter design, which covers an operating range of 335 to 425 GHz with a peak-output power of 9.0 dBm and accompanying transducer gain of 11 dB. The included transmitterand receiver-designs represent a first-time implementation in the mentioned technological process, utilizing solely TFMSLs, boasting the integration level, operating in the WR-2.2 frequency band, and setting the state of the art-to the authors' best knowledge-for all S-MMIC based solutions in the respective frequency band, in terms of output power and gain over the operating 3-dB BW.