Low-Dimensional Materials for Disruptive Microwave Antennas Design

This chapter is devoted to a complete analysis of remarkable electromagnetic properties of nanomaterials suitable for antenna design miniaturization. After a review of state of the art mesoscopic scale modeling tools and characterization techniques in microwave domain, new approaches based on wideband material parameters identification (complex permittivity and conductivity) will be described from impedance equivalence formulation achievement by de-embedding techniques applicable in integrated technology or in free space. A focus on performances of 1D materials such as vertically aligned multi-wall carbon nanotube (VA-MWCNT) bundles, from theory to technology, will be presented as a disruptive demonstration for defense and civil applications as in radar systems

Experimental Microwave Complex Conductivity Extraction of Vertically Aligned MWCNT Bundles for Microwave Subwavelength Antenna Design

This paper reports the extraction of electrical impedance at microwave frequencies of vertically aligned multi-wall carbon nanotubes (VA MWCNT) bundles/forests grown on a silicon substrate. Dedicated resonating devices were designed for antenna application, operating around 10 GHz and benefiting from natural inductive/capacitive behavior or complex conductivity in the microwave domain. As obtained from S-parameters measurements, the capacitive and inductive behaviors of VA MWCNT bundles were deduced from device frequency resonance shift

Millimeter-Wave Permittivity Variations of an HR Silicon Substrate from the Photoconductive Effect

The photoinduced microwave complex permittivity of a highly resistive single-crystal silicon wafer was extracted from a bistatic free-space characterization test bench operating in the 26.5–40 GHz frequency band under CW optical illumination at wavelengths of 806 and 971 nm. Significant variations in the real and imaginary parts of the substrate’s permittivity induced by direct photoconductivity are reported, with an optical power density dependence, in agreement with the theoretical predictions. These experimental results open the route to ultrafast system reconfiguration of microwave devices in integrated technology by an external EMI-protected and contactless control with unprecedented performance

Commande optique de circuits micro-ondes (application à la modulation et à l'échantillonnage)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Design of a Wideband 6-Anode Frequency Tripler at 300 GHz with Optimum Balance

We report on the design methodology of a fix-tuned split-block waveguide balanced frequency tripler working nominally at 300 GHz. It features six GaAs Schottky planar diodes in a balanced configuration. The circuit will be fabricated with JPL membrane technology in order to minimize dielectric loading and insure an accurate and uniform thickness of the substrate. The multiplier power handling is limited by the breakdown voltage of the diodes that depends on the doping level of the active layer. With six diodes, the current choice for the doping level leads to medium power handling capabilities of about 50 mW. Increasing the number of diodes to eight would be an option but would lead to increased difficulties in design and fabrication

Dispositif de commutation de signaux hyperfréquences notamment de dimensions nanométriques, et composant éléctronique incorporant un tel dispositif

n° de priorité : FR20120003563 2012122

Design of a Wideband 900 GHz Balanced Frequency Tripler for Radioastronomy

We report on the design of a fix-tuned split-block waveguide balanced frequency tripler working nominally at 900GHz. It uses a GaAs Schottky planar diode pair in a balanced configuration. The circuit will be fabricated with JPL membrane technology in order to minimize dielectric loading. The multiplier is bias-less to dramatically ease the mounting and the operating procedure. At room temperature, the expected output power is 50- 130 (micro)W in the band 800-970 GHz when the tripler is pumped with 4mW. By modifying the waveguide input and output matching circuit, the multiplier can be tuned to operate at lower frequencies

Characterization of Optically-Reconfigurable Metasurfaces by a Free Space Microwave Bistatic Technique

Microwave performance extraction of optically-controlled squared frequency-selective surface (FSS) structures printed on highly resistive (HR) silicon substrate are presented, from a innovative bistatic microwave photonic characterization technique operating in the 40 to 60 GHz frequency range, commonly used for radar cross section (RCS) measurements. According to typical physical photon absorption phenomenon occurring in photoconductive materials, these structures demonstrate experimentally a bandpass filtering frequency response cancellation through reflection coefficient measurements, under specific incident collective illumination in the Near-infrared region (NIR). This behaviour is attributed to their microwave surface impedance modification accordingly to the incident optical power, allowing ultrafast reconfigurability of such devices by optic

Nano photoconductive switches for microwave applications

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