Nawaf Al-Moayed

Nano Ferrites Microwave Complex Permeability and Permittivity Measurements by T/R Technique in Waveguide

There is a huge demand to accurately determine the magnetoelectrical properties of particles in the nano-sized regime due to the modern IC technology revolution and biomedical applications. In this paper, we present a microwave waveguide measurement technique for measuring complex permeability and permittivity of expensive nano-sized magnetic powder materials. We used a vector network analyzer to provide a standard TRL calibration for free space inside waveguide measurements. In order to maintain the recommended insertion phase range, a very thin prepared sample was loaded inside the calibrated waveguide. The loaded materials magnetic and dielectric effects were also considered in the cutoff wavelength calculation of the propagation constant of the TE10 wave from the geometrical dimensions of the waveguides. These provisions make the permeability and permittivity measurements more reliable than those found by commonly used techniques. We used six different compounds of nano-sized ferrite powders (Fe3O4, CuFe2O4, CuFe2O4Zn, F12NiO3Zn, BaFe12O19, and SrFe12O19), in which the average diameter of nano particles is less than 40 nm, for measurement purposes. We measured the complex permeability and permittivity from 3.95 to 5.85 GHz. The results show that the dielectric permittivity of these materials is quite different from that of solid-state materials.

Broadband Dielectric Characterization of Tumorous and Nontumorous Breast Tissues

The broadband dielectric properties of tumorous and nontumorous tissues were analyzed at the millimeter-wave and terahertz frequencies. Ex-vivo measurements were obtained using the backward-wave oscillator-based free-space quasi-optical spectroscopy and dispersive Fourier transform spectroscopy methods. Both techniques were modified to yield the real and imaginary parts of permittivity, absorption coefficient, refractive index, and transmission data over an extended frequency range from 30 to 900 GHz. Results reveal characteristic signatures of breast tissues and display a significant difference in the electromagnetic response of tumorous and nontumorous tissues. The techniques employed in this study provide prospects for extending ex-vivo measurements to in-vivo breast cancer detection and diagnostics.

High Resolution Absorption Coefficient and Refractive Index Spectra of Carbon Monoxide Gas at Millimeter and Submillimeter Wavelengths

The use of dispersive Fourier transform techniques in interferometry allows the measurement of absorption coefficient and refractive index spectra with great precision. This paper presents the absorption coefficient and refractive index spectra of carbon monoxide gas at millimeter and submillimeter wavelengths. In order to assess rotational lines of carbon monoxide, the gas was measured at four different pressures, giving insight into the behavior of the spectral lines with varying parameters. Our measurements demonstrate that varying the pressure of the gas affects only the amplitude of the absorption lines and not their exact position. This is critical in air pollution studies when trying to single out a specific gas from a field sample with unknown constituents

High Frequency Dielectric Characteristics of Tumorous and Non-tumorous Breast Tissues

The broadband dielectric properties of tumorous and non-tumorous tissues were analyzed at the microwave, millimeter wave, and terahertz ranges. In-vitro measurements were obtained using the coaxial probe and dispersive Fourier transform spectroscopy. Both techniques were modified to yield the complex real and imaginary permittivity, absorption coefficient, and refractive index. The results reveal the characteristic signatures of breast tissues and display a significant difference in the electromagnetic response of tumorous and non-tumorous tissues.

Using Coaxial Probe for Broadband Microwave Characterization of Biological Tissues

A key advantage of using coaxial probe for microwave characterization of biological media is the non-invasive nature of the technique. It is being used extensively for the complex permittivity measurements of materials in the microwave region. Usually, coaxial probe measurements require electromagnetic full-wave analysis or a calibrated reflection coefficient, S11, of the material under test. In this paper, we present a new coaxial probe technique for the microwave characterization of biological tissues based on the calibrated reflection coefficient S11 of a know dielectric constant. This technique only needs the well known distilled water as a reference material for the broadband microwave characterization of biological tissues. The complex permittivities of normal tissues from animals and both normal and cancerous tissues from human bodies were measured over a broadband microwave region with this technique. The biological tissue measurements showed that the complex permittivities measured by this technique are in good agreement with other investigations. This is a cost effective, non invasive and easy to use technique which makes it very suitable for diagnostic and therapeutic applications of microwaves in biomedicine.

High-resolution absorption coefficient and refractive index spectra of common pollutant gases at millimeter and THz wavelengths

Dispersive Fourier Transform Spectroscopy (DFTS) provides us with a very precise method of measuring the absorption and refractive index spectra of common pollutant gases. This paper presents the rotational transition lines of Sulfur Dioxide and Carbon Monoxide gas as a function of varying pressure using DFTS for the very first time as a combined study. The relationship between the variation of the pressure and the change in the absorption spectrum is examined and discussed in detail. Sulfur Dioxide and Carbon Monoxide gases are highly toxic, pollutant gases that are major contributors to global pollution and can potentially be used as a chemical threat. The relationship between pressure and rotational transmission lines is discussed in detail in the frequency range of 0.3 THz - 0.9 THz. These findings are crucial in characterizing these gases as well as identifying them in a blind test.

High-Resolution Absorption Coefficient and Refractive Index Spectra of Pollutant Gases at Millimeter Wavelengths

This paper presents the absorption coefficient and refractive index spectra of pollutant gases at millimeter wavelengths as a function of pressure using the dispersive Fourier transform spectroscopy technique.

Direct broadband microwave characterization of biological tissues using the coaxial probe technique

A key advantage of using coaxial probe for microwave characterization of biological media is the non-invasive nature of the technique. The complex permittivities of normal tissues from animals and both normal and cancerous tissues from human bodies were measured over a broadband microwave region with this technique. The biological tissue measurements showed that the complex permittivities measured by this technique are in good agreement with other investigations. This is a cost effective, non invasive and easy to use technique which makes it very suitable for diagnostic and therapeutic applications of microwaves in biomedicine.

Wireless Sensor Using High Q Resonator of Single Walled Carbon Nanotube for Liquids

Carbon nanotubes are an interesting material, in which the single walled carbon nanotube (SWCNT) can have a high microwave dielectric permittivity and a high conductivity as well. The resonators of the SWCNT were reported as gas sensors in the past. In this paper, we present a wireless sensing property of SWCNT resonators for liquids such as water and alcohols. In the experiments, it was noted that the central resonances frequencies of those excited modes in the resonator of the SWCNT were slightly moved when seeing the water and alcohol, respectively.

Precision high resolution fourier transform spectroscopy of greenhouse gases at millimeter and submillimeter wavelengths

Dispersive Fourier transform spectroscopy (DFTS) provides us with a very effective technique for the measurement of absorption and refractive index spectra of environmentally hazardous gases. This paper presents the rotational transition lines and refractive index spectra of Nitrous Oxide gas as a function of varying pressure using DFTS for the very first time. The relationship between the variation of the pressure and the change in the absorption spectrum is examined and discussed in detail. Nitrous Oxide (NO2) gas is considered a harmful greenhouse gas and is the third largest contributor to overall global warming after Carbon Dioxide and Methane. This study demonstrates the ability of our setup to accurately identify and characterize NO2 gas at differing pressures over a broadband frequency spectrum. These findings presented from 300 GHz - 900 GHz are therefore of great importance in the ongoing struggle to battle global warming.