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A phase retrieval technique for multifrequency scattered field acquisition is presented in this paper. The proposed setup is based on indirect holography schemes so that it combines the desired signal with a known reference signal. The setup is used together with a twodimensional frequency scanning (FS) antenna and, therefore, the positions of scatterers can be retrieved without the need of moving either the antenna or the objects.

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In this work, the nonlinear electromagnetic response of a few-layer graphene sheet is experimentally analyzed. The few-layer graphene sheet is obtained through mechanical exfoliation from highly ordered pyrolytic graphite and embedded in a rectangular waveguide structure which is used to guide the exciting and the output signals. The nonlinear electromagnetic response of the graphene sheet is exploited to implement a frequency multiplier in which the output signal, in the 330-500 GHz frequency band, will be obtained as a high-order harmonic component of the input signal, in the 26-40 GHz frequency band. Due to the particular selection of the input and output frequency ranges, the behavior of several harmonic components, from order 9 to 17, can be characterized. The analysis will be focused on the frequency response of the graphene sheet, the influence of the input power on the output signal and the differences between the even-and odd-order harmonic components. Finally, it will be shown that the developed assembly can be used as THz signal source based on high-order frequency multiplication.

In this work, a waveguide slotted antenna array working in the sub-millimeter wave band is presented. The antenna performs beam tilting from 68 to 89 degrees in the H-plane while sweeping the frequency from 240 GHz to 310 GHz. Sixteen rectangular slots have been cut in the wide surface of a standard WR-3 brass metal rectangular waveguide to obtain the desired behavior. The antenna has been fabricated combining laser and mechanical prototyping machinery. Experimental results showing the main waveguide slotted antenna array characteristics are also presented.

In this work, a millimetre/submillimetre wave imaging system for the analysis, characterisation and detection of hidden elements in artwork is presented. The practical implementation of the system relies on a novel generation of purpose developed frequency multiplier and mixer topologies, based on graphene non-linear devices. The proposed set-up will be experimentally validated by scanning a model painting, in order to practically illustrate the imaging capabilities of the system.

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