Apparatus and methods are provided for using a retroflected target for calibrating environmental geometric sensing systems. In particular, apparatus and methods are provided for unstructured calibrations using a plurality of spatial sensing data acquisitions and the data correlations thereof. In various implementations, a combined LiDAR-RADAR detector is used to associate one with the other. According to one aspect of the present disclosure, a predetermined LiDAR detector is used as a reference frame for RADAR segmentation. Specifically, a LiDAR point-of-interest is conveyed to RADAR system for unstructured calibration. To that end, RADAR and LiDAR can be calibrated with one another without the need for absolute positioning.

A radio frequency antenna array uses lenses and RF elements, to provide ground-based coverage for cellular communication. The antenna array can include a spherical lens, where each spherical lens has at least two associated RF elements. Each of the RF elements associated with a given lens produces an output beam with an output area. The antenna includes a control mechanism configured to enable a user to move the RF elements along their respective tracks, and automatically phase compensate the output beams produced by the RF elements based on the relative distance between the RF elements.

A radio frequency antenna array uses lenses and RF elements, to provide ground-based coverage for cellular communication. The antenna array can include two spherical lenses, where each spherical lens has at least two associated RF elements. Each of the RF elements associated with a given lens produces an output beam with an output area. Each lens is positioned with the other lenses in a staggered arrangement. The antenna includes a control mechanism configured to enable a user to move the RF elements along their respective tracks, and automatically phase compensate the output beams produced by the RF elements based on the relative distance between the RF elements.

An extrinsic-calibration system includes at least one target and a computer. Each target includes three flat surfaces that are mutually nonparallel and a corner at which the three surfaces intersect. The computer is programmed to estimate a first set of relative positions of the corner in a first coordinate frame from a first sensor, the first set of relative positions corresponding one-to-one to a set of absolute positions of the at least one target; estimate a second set of relative positions of the corner in a second coordinate frame from a second sensor, the second set of relative positions corresponding one-to-one to the set of absolute positions; and estimate a rigid transformation between the first coordinate frame and the second coordinate frame based on the first set of relative positions and the second set of relative positions.

An extrinsic-calibration system includes at least one target and a computer. Each target includes three flat surfaces that are mutually nonparallel and a corner at which the three surfaces intersect. The computer is programmed to estimate a first set of relative positions of the corner in a first coordinate frame from a first sensor, the first set of relative positions corresponding one-to-one to a set of absolute positions of the at least one target; estimate a second set of relative positions of the corner in a second coordinate frame from a second sensor, the second set of relative positions corresponding one-to-one to the set of absolute positions; and estimate a rigid transformation between the first coordinate frame and the second coordinate frame based on the first set of relative positions and the second set of relative positions.

A dual band printed antenna that includes a substrate including a first and a second surfaces opposite to each other and conductive holes, a first and a second drivers, a first and a second reflectors and a transmission line is provided. The first driver is disposed on the first surface to generate a radiation pattern of a first frequency band. The first reflector is disposed on the first surface and apart from the first driver. The second driver is disposed on the second surface to generate a radiation pattern of a second frequency band and electrically coupled to the first driver through the conductive holes. The reflector is disposed on the second surface, corresponding to a position of the first driver and apart from the second driver. The transmission line is disposed on the first surface and coupled to a feeding point and a ground point of the first driver.

A dual band printed antenna that includes a substrate including a first and a second surfaces opposite to each other and conductive holes, a first and a second drivers, a first and a second reflectors and a transmission line is provided. The first driver is disposed on the first surface to generate a radiation pattern of a first frequency band. The first reflector is disposed on the first surface and apart from the first driver. The second driver is disposed on the second surface to generate a radiation pattern of a second frequency band and electrically coupled to the first driver through the conductive holes. The reflector is disposed on the second surface, corresponding to a position of the first driver and apart from the second driver. The transmission line is disposed on the first surface and coupled to a feeding point and a ground point of the first driver.

A radio frequency antenna array uses lenses and RF elements, to provide ground-based coverage for cellular communication. The antenna array can include two spherical lenses, where each spherical lens has at least two associated RF elements. Each of the RF elements associated with a given lens produces an output beam with an output area. Each lens is positioned with the other lenses in a staggered arrangement. The antenna includes a control mechanism configured to enable a user to move the RF elements along their respective tracks, and automatically phase compensate the output beams produced by the RF elements based on the relative distance between the RF elements.

A system comprises a first sensor on a first end of a vehicle and an on-board controller coupled to the first sensor. The first sensor is configured to detect a radio frequency (RF) signature of a marker along a guideway. The first sensor is a radar detection device. The on-board controller is configured to determine a first position of the vehicle on the guideway or a first distance from the position of the vehicle to a stopping location along the guideway based on at least the RF signature received from the first sensor. The marker is a metasurface plate comprising a first diffused element, a first retroreflector element, a first absorbing element and a second diffused element between the first retroreflector element and the first absorbing element.

A multisegment array-fed reflector antenna includes a feed array consisting of a number of subarrays and a multisegment reflector to reflect multiple beams of the feed array into a number of elevation angles. A support structure couples the multisegment reflector to the feed array. The multisegment reflector includes two or more ring-focus parabolic segments, and each ring-focus parabolic segment is a parabolic surface extending along a circle around the support structure.