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The report deals with corrugated waveguides and horns. A review of the propagation and radiation properties is given, and the design of two horns for the Onsala 20 m radio telescope is reported.
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Electromagnetic fields inside a circular, axially tuned corrugated waveguide,also called a hard surface waveguide are considered. The waveguide is filled with uniaxial anisotropic material. The eigenfields in this kind of waveguid...
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Electromagnetic fields inside a circular, axially tuned corrugated waveguide,also called a hard surface waveguide are considered. The waveguide is filled with uniaxial anisotropic material. The eigenfields in this kind of waveguide are TE and TM fields which are propagating with different propagation factors. Polarization properties of reflected and transmitted fields are studied. This kind of waveguide component can be used for changing handedness, as a polarization transformer, and a mode filter element for hard surface waveguides.
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For health monitoring of structures with periodic geometry a good understanding of the elastic wave propagation through such periodic structures is necessary. Although a number of research papers on the wave propagation through pe...
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For health monitoring of structures with periodic geometry a good understanding of the elastic wave propagation through such periodic structures is necessary. Although a number of research papers on the wave propagation through periodic structures are available in the literature hardly anyone investigated experimentally the guided wave propagation through plates with periodic plate boundaries and compared the experimental data with theoretical predictions. In this paper the elastic wave propagation in three different plates with different degrees of corrugation is experimentally studied. The experimental results clearly show that elastic waves can propagate through the corrugated plate (waveguide) for certain frequencies called pass bands and find it difficult to propagate for some other frequencies called stop bands. Stop bands are found to increase with the degree of corrugation. Experimental results for non-sinusoidal periodic plates are compared with the theoretical predictions for sinusoidal corrugated plates and good matching is observed for plates with small degree of corrugation indicating that for small corrugation depths only two parameters - the depth of corrugation and the wavelength of the periodicity - are enough for modeling the elastic wave propagation through the corrugated plate.
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A circular waveguide horn coated with a lossy material in its interior wall can be used as an alternative to a corrugated waveguide for radiating a circularly polarized (CP) field. To achieve good CP radiation, the diameter of the...
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A circular waveguide horn coated with a lossy material in its interior wall can be used as an alternative to a corrugated waveguide for radiating a circularly polarized (CP) field. To achieve good CP radiation, the diameter of the structure must be larger than the free-space wavelength, and the coating material must be sufficiently lossy and magnetic. This device is cheaper and lighter in weight than the corrugated one.
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Homogeneous waveguides with both isotropic and anisotropic impedance boundaries were considered. Asymptotic high frequency mode properties were derived systematically. Several expressions showing the orthogonality properties of th...
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Homogeneous waveguides with both isotropic and anisotropic impedance boundaries were considered. Asymptotic high frequency mode properties were derived systematically. Several expressions showing the orthogonality properties of the asymptotic high frequency fields were deduced and duality transformations satisfying certain requirements were considered. Self-dual solutions corresponding to the two duality transformations are demonstrated and stationary functionals are constructed. An explicit formula for the calculation of the asymptotic attenuation coefficient for the general waveguide is given, isotropic and anisotropic boundaries being considered separately. Attenuation properties of a corrugated waveguide are used as an example.
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Upcoming experiments aim to produce high fidelity polarization maps of the cosmic microwave background. To achieve the required sensitivity, we are developing monolithic, feedhorn-coupled transition edge sensor polarimeter arrays ...
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Upcoming experiments aim to produce high fidelity polarization maps of the cosmic microwave background. To achieve the required sensitivity, we are developing monolithic, feedhorn-coupled transition edge sensor polarimeter arrays operating at 150 GHz. We describe this focal plane architecture and the current status of this technology, focusing on single-pixel polarimeters being deployed on the Atacama B-mode Search (ABS) and an 84-pixel demonstration feedhorn array backed by four 10-pixel polarimeter arrays. The feedhorn array exhibits symmetric beams, cross-polar response less than -23 dB and excellent uniformity across the array. Monolithic polarimeter arrays, including arrays of silicon feedhorns, will be used in the Atacama Cosmology Telescope Polarimeter (ACTPol) and the South Pole Telescope Polarimeter (SPTpol) and have been proposed for upcoming balloon-borne instruments.
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Metamaterials are artificially constructed materials. When electromagnetic waves propagate through metamaterials they display properties different from those found in natural materials. These different properties can include negat...
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Metamaterials are artificially constructed materials. When electromagnetic waves propagate through metamaterials they display properties different from those found in natural materials. These different properties can include negative refraction (light is bent in the opposite direction from that expected from general laws of physics), flat lens focusing, and subwavelength imaging. The use of meta-materials to direct electromagnetic beams is a highly promising approach to overcome current limitations of conformal antennas by improving the radiation characteristics of antenna elements, especially those at the edge of phased array antennas.
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