A wireless telecommunication system for an equipment in an underground structure is disclosed. The system comprises a metal cover fitting in an opening of the underground structure while being supported by a shoulder. A porthole is formed in the cover. The porthole has a lens in plastic material letting radio waves pass. A cradle hangs across the opening. An antenna arrangement is mounted on the cradle and extends near and in alignment with the lens. A radio transceiver connects to the antenna arrangement and to the equipment in the underground structure to establish a wireless telecommunication with the equipment via the antenna arrangement and the lens.

According to the present disclosure there is provided a multiple-input-multiple-output (MIMO) transmitter for transmitting wireless communication signals over a communication channel to a receiver, the transmitter including a digital signal processor configured to perform pre-coding on a plurality N.sub.s of data streams; a plurality N.sub.RF of radio-frequency (RF) chains each configured to pass a pre-coded data stream from the digital signal processor to generate a signal representing that data stream; a lens antenna array comprising an array of N.sub.T antenna elements; and a selecting unit coupled between the plurality N.sub.RF of RF chains and the lens antenna array, the selecting unit including a plurality of separate coupling units each configured to couple a respective RF chain to a selective sub-array of N.sub.T.sup.B.sup.RF antenna elements concurrently for transmitting the signal representing the data stream passed through that RF chain.

A terahertz wave lens includes a substrate having a surface provided with an uneven structure that changes a phase of the terahertz wave. The uneven structure includes a plurality of holes that are periodically arranged. The uneven structure includes a plurality of regions where the plurality of holes are arranged. A height of the hole in a thickness direction of the substrate and a width of the pillar differ for each of the regions. Outer end portions of the uneven structure in the thickness direction are located on the same plane.

According to various embodiments, an array of elements forms an artificially-structured material. The artificially-structured material can also include an array of tuning mechanisms included as part of the array of elements that are configured to change material properties of the artificially-structured material on a per-element basis. The tuning mechanisms can change the material properties of the artificially-structured material by changing operational properties of the elements in the array of elements on a per-element basis based on one or a combination of stimuli detected by sensors included in the array of tuning mechanisms, programmable circuit modules included as part of the array of tuning mechanisms, data stored at individual data stores included as part of the array of tuning mechanisms, and communications transmitted through interconnects included as part of the array of elements.

According to various embodiments, an array of elements forms an artificially-structured material. The artificially-structured material can also include an array of tuning mechanisms included as part of the array of elements that are configured to change material properties of the artificially-structured material on a per-element basis. The tuning mechanisms can change the material properties of the artificially-structured material by changing operational properties of the elements in the array of elements on a per-element basis based on one or a combination of stimuli detected by sensors included in the array of tuning mechanisms, programmable circuit modules included as part of the array of tuning mechanisms, data stored at individual data stores included as part of the array of tuning mechanisms, and communications transmitted through interconnects included as part of the array of elements.

Provided is an antenna which includes a plurality of radiating portions which are formed on a substrate and a plurality of dielectric lenses for respectively converting a spherical wave radiated from each radiating portion into a plane wave, wherein the shape of a cross section of each dielectric lens perpendicular to a radiation direction of a beam is formed in a shape which radiates a beam which is narrower in a second direction than in a first direction orthogonal to the second direction, and the plurality of dielectric lenses are arranged side by side in the second direction so that beams radiated from the respective dielectric lenses are synthesized.

A radar apparatus that detects an object using radiated waves includes: an antenna surface that includes an element unit that emits a radiated wave for a radar; and a cover member that covers the antenna surface to protect the element unit. The cover member includes an inner refractive surface that is an inner side surface of the cover member on which an undesired wave is incident and is formed into a shape that refracts the undesired wave incident on the inner refractive surface so as to advance towards antenna rear. The antenna rear is a side opposite an antenna front that is a side on which the radiated wave is emitted, with the antenna surface as a boundary. Undesired waves are radiated waves that are emitted outside a range of a predetermined solid angle relative to a normal direction of the antenna surface from a center of the antenna surface from which the radiated waves are emitted.

A radar apparatus that detects an object using radiated waves includes: an antenna surface that includes an element unit that emits a radiated wave for a radar; and a cover member that covers the antenna surface to protect the element unit. The cover member includes an inner refractive surface that is an inner side surface of the cover member on which an undesired wave is incident and is formed into a shape that refracts the undesired wave incident on the inner refractive surface so as to advance towards antenna rear. The antenna rear is a side opposite an antenna front that is a side on which the radiated wave is emitted, with the antenna surface as a boundary. Undesired waves are radiated waves that are emitted outside a range of a predetermined solid angle relative to a normal direction of the antenna surface from a center of the antenna surface from which the radiated waves are emitted.

The present disclosure provides a production method for a Luneburg lens, which can manufacture a Luneburg lens with stable indexes and high performance under the conditions of room temperature, normal pressure, and low cost. The production method includes the following steps: bonding first granular materials into a sphere by a bonding agent, so as to obtain a sphere core; spraying the bonding agent on the surface of the sphere core, placing the sphere core in a container containing second granular materials, and rolling the sphere core, so that the surface of the whole sphere core is bonded with the second granular materials until the thickness of the second granular particles reaches a preset range, and thus forming a dielectric layer coating the sphere core; and by analogy, preparing a predetermined number of dielectric layers, so as to obtain a target finished Luneburg lens.

The present disclosure provides a production method for a Luneburg lens, which can manufacture a Luneburg lens with stable indexes and high performance under the conditions of room temperature, normal pressure, and low cost. The production method includes the following steps: bonding first granular materials into a sphere by a bonding agent, so as to obtain a sphere core; spraying the bonding agent on the surface of the sphere core, placing the sphere core in a container containing second granular materials, and rolling the sphere core, so that the surface of the whole sphere core is bonded with the second granular materials until the thickness of the second granular particles reaches a preset range, and thus forming a dielectric layer coating the sphere core; and by analogy, preparing a predetermined number of dielectric layers, so as to obtain a target finished Luneburg lens.