The Horn Antenna as Gaussian Source in the mm-Wave Domain

Kazemipour, Alireza; Hudlička, Martin; Dickhoff, R.; Salhi, Mohammed; Kleine‐Ostmann, Thomas; Schräder, Thorsten

doi:10.1007/s10762-014-0077-9

Cited by 23 publications

(10 citation statements)

References 7 publications

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“…and the system calibration. The study of the setup and its optimization is mainly based on theoretical and experimental works of [19,20]. This paper is focused on extraction methods, only, whereas both the VNA calibration and the associated frequency extender optimization are performed to minimize the uncertainties of the input parameters (S 21 , amplitude, and phase).…”

Section: Introductionmentioning

confidence: 99%

Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies

Kazemipour

Wollensack

Hoffmann

et al. 2020

J Infrared Milli Terahz Waves

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Material parameter extraction algorithms are studied and simplified both for transmission-reflection and transmission-only methods. The simplified relations, which are closed-form in some cases, are analyzed to establish the uncertainty sensitivity coefficients and therefore, to clarify the main uncertainty contributions and reduce the systematic and random errors. Simple closed-form expressions presented in this paper show the sensitivity of the extracted permittivity to each input parameter such as S21 (phase and amplitude), frequency, and the material thickness. Results are presented for several material slabs for three waveguide frequency ranges 75–110 GHz, 140–220 GHz, and 500–750 GHz using VNA-based free-space technique in the THz domain. Comparison of results (and the associated uncertainties) between different algorithms can help to choose the optimal one suitable for lossy or low-loss materials, and thin or thicker slabs. This can explain why the same set of S-parameters data usually gives different final results (permittivity and permeability) with different algorithms and verify the reliability of the calibration and extraction process.

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Section: Introductionmentioning

confidence: 99%

Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies

Kazemipour

Wollensack

Hoffmann

et al. 2020

J Infrared Milli Terahz Waves

Self Cite

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“…A reference analytical model is used to evaluate how accurately each camera captures H-and E-field plane beam cross section intensity distributions, in terms of overall shape, using statistical R-squared analysis. The analytical model assumes that the pyramidal horn antenna acts as a perfect Gaussian source, with a Gaussian approximation for beam intensity given by [19]:…”

Section: A Diverging Beammentioning

confidence: 99%

Benchmarking a Commercial (Sub-)THz Focal Plane Array Against a Custom-Built Millimeter-Wave Single-Pixel Camera

Shin

Lucyszyn

2020

IEEE Access

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For the first time, the characteristics of an evolving commercial camera technology that can operate at millimeter-wave frequencies has been independently investigated. In this work, we benchmark the TeraSense camera against a custom-built single-pixel camera at W-band, for image quality and aperture reflectance. It is found that the Tera-1024 TeraSense camera exhibits limited image resolution and fidelity, with significant levels of systematic spatial noise. In a poor signal-to-noise ratio scenario, the addition of random noise exacerbates these problems. Possible causes of both beam and image distortion have been identified in quasi-optical applications, which gives important insight into the best use of (sub-)THz cameras and interpretation of their images. Inherent standing waves caused by the significant power reflectance of the camera aperture is investigated in detail. A simple W-band one-port quasi-optical scalar network analyzer is developed, to determine the levels of reflectance for both cameras, with its bespoke calibration routine derived from first principlesproviding a low-cost solution for many non-destructive testing applications. It is found that the TeraSense camera (with additional RAM) and single-pixel camera (having default RAM) have measured reflectance values of 27% and 3%, respectively, over a corresponding aperture area ratio of approximately 714:1. While our single-pixel camera provides excellent image resolution and fidelity, it inherently suffers from very slow raster-scanning speeds and operational bandwidth limitations. For this reason, the TeraSense camera technology is excellent for performing qualitative measurements in real time, with the caveats outlined in this paper.

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“…The implementation of the CM principle is obtained by positioning the first focus of the ellipsoid at the phase center of precisely manufactured horn antennas with efficient modeto-mode conversion from the fundamental waveguide mode (TE 10 ) to the free-space fundamental Gaussian mode (TEM 00 ). The inverse conversion takes place in the detector's horn antenna [25]. This scheme also provides polarization selectivity, which concurs to reject scattered radiation and to increase the CM resolution [29].…”

Section: A Microscopementioning

confidence: 99%

“…Single-wavelength imaging allows for the introduction of advanced in-depth optical microscopy concepts taken from the visible range such as confocal imaging [23] and super-resolution imaging [24]. In confocal microscopy (CM), a full image of the sample can be obtained at different depth levels by using the spatial pinhole concept, which in the THz range can be implemented by employing microelectronic point emitters and detectors in a quasi-optical scheme [25]. According to Abbe's theory of diffraction and the subsequent developments of confocal laser microscopy theory [26], the confocal scheme with coherent illumination provides diffraction-limited lateral resolution given by:…”

mentioning

confidence: 99%

Confocal Imaging at 0.3 THz With Depth Resolution of a Painted Wood Artwork for the Identification of Buried Thin Metal Foils

Ciano

Flammini

Giliberti

et al. 2018

IEEE Trans. THz Sci. Technol.

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A compact confocal terahertz microscope working at 0.30 THz based on all-solid state components is used to locate buried thin metal foils in a painted wood artwork. Metal foils are used for decoration and their precise localization under the pictorial layer is relevant information for conservation scientists and restorers, which cannot be obtained neither by X-ray radiography nor by spectroscopic imaging in the infrared, as we directly show here. The confocal microscopy principle based on the spatial pinhole concept is here implemented by positioning the first focus of an ellipsoidal reflector at the phase center of horn antennas coupled to Schottky diode detector and emitter mounted in rectangular waveguide blocks, together with an optical beamsplitter. The second focus of the reflector is mechanically scanned inside the sample in three dimensions. The predictions of diffraction theory for a confocal microscope at an imaging wavelength of 1.00 mm with numerical aperture of 0.53 are verified experimentally (1.2 mm and 2.8 mm for the lateral and the axial resolution respectively). These values of resolution allow a precise determination of the position of buried metal foils in ancient piece of art hence making restoration interventions possible.

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The Horn Antenna as Gaussian Source in the mm-Wave Domain

Cited by 23 publications

References 7 publications

Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies

Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies

Benchmarking a Commercial (Sub-)THz Focal Plane Array Against a Custom-Built Millimeter-Wave Single-Pixel Camera

Confocal Imaging at 0.3 THz With Depth Resolution of a Painted Wood Artwork for the Identification of Buried Thin Metal Foils

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