This letter presents a dual-polarized dielectric resonator antenna (DRA) achieving more than 40% fractional bandwidth, thus the 5G bands n257 and n260 are covered with a single antenna. Hence, the system cost is considerably reduced, since only one antenna array system is required. The bandwidth could be reached thanks to the wideband monopoles and differential feeding enabling hybrid operation in monopole and DRA mode. The antenna uses a standard two metal layer printed-circuit-board (PCB) process and 3-D printing for the fabrication of the dielectric resonators, reducing the number of PCB layers and the overall production cost. The prototypes of a single element and 2 × 2 array show a maximal gain of 7.1 and 10.4 dBi, respectively.
This paper presents a review of radar applications in high-accuracy distance measurement of a target. The radars included in this review are frequency modulated continuous wave (FMCW) radar sensors operating in four different millimeter-wave frequency bands, namely 24 GHz, 61 GHz, 80 GHz and 122 GHz. The radar sensors are used to measure the distance of standard and complex targets in a short range of a few meters, thus indicating that the choice of target and the medium used for radar signal propagation also play a key role in determining the distance measurement accuracy of an FMCW radar. The standard target is a trihedral corner reflector in a laboratory-based free space measurement setup and the complex targets include a piston in an oil-filled hydraulic cylinder and a planar positioning stage used in micromachining. In each of these measurement scenarios, a distance measurement accuracy in micrometer range is achieved due to the use of a sophisticated signal processing algorithm that is based on a combined frequency and phase estimation method. The paper is concluded with a technical comparison of the accuracy achieved by the FMCW radars reviewed in this article with other related works.
To enlarge the range of wireless fronthaul and backhaul communication links operating close to the millimeterwave (mmW) region, this work presents a novel Line-of-Sight (LoS) Multiple-Input Multiple-Output (MIMO) relay system. The analog relay system consists of a simple 90°hybrid coupler to separate two uncorrelated transmit data streams realizing a lowcomplex and cheap system. The functional capability is proven within measurements of two independent 2 × 2 LoS MIMO links at 28 GHz connected by the relay system. A high decoupling of the two independent transmitted data streams of more than 27 dB after the 90°hybrid coupler and a high modulation error rate (MER) at the last receiver of around 22 dB could be reached for QPSK and 16-QAM modulated signals.
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