This paper describes and validates for the first time the dynamic modelling of Liquid Crystal (LC)-based planar multi-resonant cells, as well as its use as bias signals synthesis tool to improve their reconfigurability time. The dynamic LC director equation is solved in the longitudinal direction through the finite elements method, which provides the z-and time-dependent inhomogeneous permittivity tensor used in an electromagnetic simulator to evaluate the cells behaviour. The proposed model has been experimentally validated using reflective cells for phase control (reflectarray) and measuring the transient phase, both in excitation and relaxation regimes. It is shown how a very reduced number of stratified layers are needed to model the material inhomogeneity, and that even an homogeneous effective tensor can be used in most of the cases, which allows a model simplification suitable for design procedures without losing accuracy. Consequently, a novel bias signal design tool is proposed to significantly reduce the transition times of LC cells, and hence, of electrically large antennas composed of them. These tools, similar to those used in optical displays, are experimentally validated for the first time at mm-and sub-mm wave frequencies in this work, obtaining an improvement of orders of magnitude.

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We report on the design and characterization of a novel backside-radiating antenna-coupled direct terahertz detector fabricated in 65 nm CMOS technology. The novelty of the design lies in the low-metal coverage of the biquad antenna geometry, which adapts well to the particular challenging conditions of on-chip antenna integration in silicon and allows optimization for a versatility of operation conditions. The biquad antenna was modified here to achieve wideband radiation and matching to a gate-coupled single-finger fieldeffect transistor with AC open condition at the drain terminal. The successful detector performance was the result of a careful treatment of transistor, antenna and optics from a co-design perspective since the beginning of the design. This included the frequency-dependent complex impedance for optimum matching, the technology restrictions to ensure proper chip fabrication, and the overall detection efficiency after backing the device with a silicon lens. Calibrated detector measurements for 7777 Hz modulation frequency yielded minimum optical noise-equivalentpower (NEP) of 25 pW/»Hz at 1 THz, with NEP values below 50 pW/»Hz in the 0.84 -1.29 THz frequency range. These figures achieve state-of-the-art of wideband CMOS-based detectors and are only a factor of ∼2 inferior to the best reported narrowband devices close to 1 THz. Index Terms-CMOS integrated circuit, on-chip antenna, TeraFET, terahertz power detector, wideband terahertz sensor. I. INTRODUCTIONE MERGING applications in the field of optoelectronic terahertz (THz) equipment are pushing the demand for compact, high-performing, cost-effective technology solutions for room-temperature operation in the THz range [1]-[3].

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