Wideband Gap-Waveguide Phase Shifter Based on a Glide-Symmetric Ridge

This paper presents a gap-waveguide phase shifter based on ridged unit cell with glide-symmetric configuration. The proposed unit cell design provides higher phase shift compared with a conventional ridged unit cell whose ridge height and waveguide width are tuned to achieve a stable phase shift. Through the insertion of glide-symmetric holes with semi-circle base in the ridged waveguide, a stable phase shift in a wide frequency range is achieved. Depending on the radii of the holes, the stable phase shift can be covered the desired frequency range. A 90^o phase shifter in millimeter-wave range is designed in order to validate the analysis. The impedance bandwidth of the phase shifter is from 32 GHz to 42.5 GHz (28.18%) providing a phase shift of 90^o+- 2^o in the entire frequency range.

Wideband Gap-Waveguide Phase Shifter Based on a Glide-Symmetric Ridge

This paper presents a gap-waveguide phase shifter based on ridged unit cell with glide-symmetric configuration. The proposed unit cell design provides higher phase shift compared with a conventional ridged unit cell whose ridge height and waveguide width are tuned to achieve a stable phase shift. Through the insertion of glide-symmetric holes with semi-circle base in the ridged waveguide, a stable phase shift in a wide frequency range is achieved. Depending on the radii of the holes, the stable phase shift can be covered the desired frequency range. A 90^o phase shifter in millimeter-wave range is designed in order to validate the analysis. The impedance bandwidth of the phase shifter is from 32 GHz to 42.5 GHz (28.18%) providing a phase shift of 90^o+- 2^o in the entire frequency range.

Some Contributions for Antenna 3D Far Field Characterization at Terahertz

The three-dimensional (3D) characterization of antenna far field patterns at terahertz frequencies is addressed. This task is challenging, because the phase of the electric field is difficult to measure accurately and reliably. From the sub-millimeter wave range, the small wavelength indeed significantly increases the impact of mechanical and electrical errors. Models and procedures to estimate these errors are proposed to mitigate their effects. The 3D far field patterns of a circularly polarized horn measured at 300 GHz and a multibeam pillbox antenna at 270 GHz are shown. The agreement between the 3D measurements and the two-dimensional (2D) patterns of reference as well as the radiated pattern before and after correction demonstrates the interest of the proposed approach and experimentally validate the proposed error estimation procedures. The methodology can be applied to direct far field measurement facilities as well as compact antenna test ranges.

Microwave synthesis of Bessel, Bessel–Gauss, and Gaussian beams: a fully vectorial electromagnetic approach

Bessel, Bessel-Gauss, and Gaussian beams have widely been investigated in optics in the paraxial approximation, under the frame of a scalar wave theory. Such approximations can hardly be applied in the microwave/millimeter-wave range, where the vectorial nature of the electromagnetic fields cannot be neglected, and experimental realizations for some of these beams appeared only recently. In this work, we discuss the generation of Bessel, Bessel-Gauss, and Gaussian beams through a fully vectorial electromagnetic approach. The field derivation of all these beams is first illustrated and numerical evaluations are then reported to compare their different propagation and diffractive behaviors. Finally, an innovative approach for realizing such solutions with planar microwave devices exploiting leaky waves is demonstrated through accurate numerical simulations.

Dielectric Permittivity Model for Polymer–Filler Composite Materials by the Example of Ni- and Graphite-Filled Composites for High-Frequency Absorbing Coatings

The suppression of unnecessary radio-electronic noise and the protection of electronic devices from electromagnetic interference by the use of pliable highly microwave radiation absorbing composite materials based on polymers or rubbers filled with conductive and magnetic fillers have been proposed. Since the working frequency bands of electronic devices and systems are rapidly expanding up to the millimeter wave range, the capabilities of absorbing and shielding composites should be evaluated for increasing operating frequency. The point is that the absorption capacity of conductive and magnetic fillers essentially decreases as the frequency increases. Therefore, this paper is devoted to the absorbing capabilities of composites filled with high-loss dielectric fillers, in which absorption significantly increases as frequency rises, and it is possible to achieve the maximum frequency selective of absorption due to electromagnetic and electromechanical resonances.

Исследование потерь пропускания в поликристаллическом CVD-алмазе в миллиметровом диапазоне длин волн методом свободного пространства

Radio transparency of polycrystalline CVD-diamond disks with diameter up to 75 mm in millimeter-wave range was measured by free-space method. The structure of the disks was characterized by Raman spectroscopy and scanning electron microscopy. Dielectric loss tangent tan δ of the samples in the frequency range of 50 – 67 GHz was found to be in the range of 7.5·10−3 − 2.8·10−2, increasing with frequency. The transmission loss due to the radiation absorption is about 1%.

Low-Profile Metamaterial-Based Adaptative Beamforming Techniques

In this chapter, we will review recent research advances on beamforming and spatial multiplexing techniques using reconfigurable metamaterials (MTMs) and metasurfaces. This chapter starts by discussing basic principles and practical applications of transmission line-based metamaterials and planar metasurfaces, followed by their active versions that enable novel smart antennas with beam steering and beamshaping functions. We include detailed descriptions of their practical realizations and the integration with circuits and the radio-frequency (RF) frontend, which are used to adaptively and dynamically manipulate electromagnetic radiation. We summarize the state-of-the-art MTM/metasurface-based beamforming techniques and provide a critical comparison for their uses in the RF-to-millimeter-wave range in terms of cost, reconfigurability, system integratability and radiation properties. These techniques are expected to pave the way for the massive deployment of communication, radar, remote sensing and medical and security imaging systems.