This paper presents the design of a wideband pyramidal inverted glass resonator antenna (PIGRA) for sub-terahertz applications. The proposed glass antenna concept is demonstrated through two implementations: (i) a single radiator integrated on a single-layer glass Printed Circuit Board (PCB) based on a glass-on-glass architecture, and (ii) a $4\times4$ planar square PIGRA array implemented on a two-layer Rogers CLTE substrate. The single-radiator implementation achieves an impedance bandwidth exceeding $42\,\mathrm{\%}$, covering the entire D-band ($110$–$170\,\mathrm{GHz}$), with a peak realized gain of $5.8\,\mathrm{dBi}$. The $4\times4$ array achieves a $38\,\mathrm{\%}$ impedance bandwidth in D-band, and a peak realized gain of $15\,\mathrm{dBi}$. The proposed antenna is fabricated using laser-induced deep etching (LIDE®) technology from LPKF® on Schott® BF33 borosilicate glass, demonstrating for the first time the feasibility of 2.5D glass micromachining for antenna structures operating at frequencies above $100\,\mathrm{GHz}$. The glass PCB of the single-radiator implementation is metallized through physical vapor deposition, followed by an electroplating process. The design methodology, fabrication process, assembly approach, and measured performance are presented and compared with full-wave electromagnetic simulation results obtained using CST Microwave Studio. The measured results are in good agreement with the simulations and validate the proposed glass-based PIGRA architecture for D-band and beyond wireless communication and sensing applications.

Terahertz near-field imaging enables high-resolution biomedical and material characterization by combining the non-ionizing nature of terahertz radiation with sub-wavelength spatial resolution. However, the scalability of existing solid-state near-field imagers is fundamentally limited by shared illumination schemes and laterally arranged imaging components, restricting pixel miniaturization and array density. This work overcomes these limitations by introducing a novel pixel architecture that vertically integrates the illumination source, near-field sensing element, and power detector within each pixel, replacing conventional lateral implementations. The proposed architecture reduces the pixel footprint while enabling every pixel to operate as an independent terahertz near-field sensor. Based on this concept, a fully monolithic 32 × 32 (1024-pixel) near-field imager was implemented in a 130-nm SiGe BiCMOS HBT technology. The sensor operates in rolling-shutter mode and achieves real-time imaging at up to 40 fps. The chip consumes 280 mW, corresponding to 273 μW per pixel, and achieves a pixel density of 200 pixels/mm2, the highest reported for monolithically integrated terahertz near-field imaging systems above 100 GHz. The paper presents the scalable architecture together with the design, characterization, and performance analysis of the individual imaging components and discusses the trade-offs introduced by vertical integration.

The radome of weather radars can be covered with a layer of water, degrading the quality of the radar products. Considering a simplified setup with a planar replica of the Swiss weather radars’ radome, we measure and model analytically its scattering parameters, with and without water. The measured reflectance of the dry radome replica agrees well with the one modeled according to the manufacturer specifications. Water forms droplets on the hydrophobic surface, but water films thicker than 1 mm can be created. Meteorologically more realistic thinner water films are expected on old radomes that have become hydrophilic with aging. Using hygroscopic silk and cotton tissues, we empirically imitate water films as thin as less than 0.1 mm. The measurements align with the simple analytical model of uniform plane wave incidence on the radome and water film but could be further improved by taking refraction and bending of the radome replica into account. Simulations with the General Reflector Antenna Software Package (GRASP) from TICRA complement the study for a representative setup with a spherical radome.

Polyaniline (PANI)–PbTiO3 composites were prepared by using different inorganic and organic acids by in situ polymerization technique using sodium dodecyl benzene sulfonic acid as a surfactant. The structural analysis was studied by using x-ray diffraction, and it was found that PANI is amorphous in nature. The scanning electron microscopy studies reveal that they are agglomerated and irregular, and size of these grains increase by increasing the amount of PANI with different organic and inorganic acids. The real part of complex permittivity (εʹ) and imaginary part of complex permittivity (εʹʹ) and the real part of the permeability (μ′) are studied at X-band frequency where (εʹ) and (εʹʹ) decreas with increase in frequencies, whereas μ′ increases with increase in X-band frequency and exhibits a maximum value of 0.87 at the resonance frequency of 9–11 GHz of 30 wt% PbTiO3 in PANI matrix. Reflection loss peak of 30 wt% of PANI–PbTiO3 composites is 28.6 dB at 10.8 GHz, which may be attributed to the maximum reflection of the microwave power for the particular doping concentration.

This paper explores the characterization of dielectric and conductive properties of carbon nanotube (CNT) networks. This is carried out by building planar transmission lines where conventional metallic traces are replaced by CNT networks. The proposed transmission lines with CNT networks are presented. Experimental realization and repeated two-port microwave measurements of proposed transmission lines enable the accurate extractions of their fundamental parameters showing percolation effects due to presence of CNT networks. The frequency-dependent phase velocity characteristics show a dramatic reduction compared to the speed of light in vacuum. The large magnitude of extracted complex permittivity for CNT networks also exhibits its percolation performance. The effects of CNTs' bulk density on measured and calculated parameters are explained. The results presented in this paper demonstrate the feasibility and the potential of building transmission lines and radio-frequency (RF) circuits elements using CNT networks.

This paper discusses on the miniaturization of radiofrequency (RF) front-end components such as half-wavelength resonators based on new magneto-dielectric heterostructures combining high permeability (µ = 150–250) and high permittivity (ε = 18–150). Size reduction is evaluated by means of 2-cm-long coplanar waveguides realized with silicon technology and having a resonance frequency of about 3 GHz. The experimental results show a physical length reduction of 11.2% due to the dielectric contribution (ε = 18) and 14.8% by cumulating dielectric and magnetic effects (ε = 18 and µ = 150). These results are significant with respect to the moderate thickness of the preliminary material used here (only 150 nm). In a second part, a predictive model is proposed with µ and ε as variables. When adjusting the material properties in a realistic way (µ = 250 and ε = 150), the model predicts size reduction of ~50% for the same thickness. Larger values can be expected with increasing the film thickness.