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This study addressed the problem of localization in an ultrawide-band (UWB) network, where the positions of both the access points and the tags needed to be estimated. We considered a fully wireless UWB localization system, comprising both software and hardware, featuring easy plug-and-play usability for the consumer, primarily targeting sport and leisure applications. Anchor self-localization was addressed by two-way ranging, also embedding a Gauss–Newton algorithm for the estimation and compensation of antenna delays, and a modified isolation forest algorithm working with low-dimensional set of measurements for outlier identification and removal. This approach avoids time-consuming calibration procedures, and it enables accurate tag localization by the multilateration of time difference of arrival measurements. For the assessment of performance and the comparison of different algorithms, we considered an experimental campaign with data gathered by a proprietary UWB localization system.

Ultra-wideband (UWB) networks are gaining wide acceptance in short- to medium-range wireless sensing and positioning applications in indoor environments due to their capability of providing high-ranging accuracy. However, the performance is highly related to the accuracy of measured position and antenna delay of anchor nodes, which form a reference positioning system of fixed infrastructure nodes. Usually, the position and antenna delay of the anchor nodes are measured separately as a standard initial procedure. Such separate measurement procedures require relatively more time and manual interventions. This paper presents a system that simultaneously measures the position and antenna delay of the anchor nodes. It provides comprehensive mathematical modeling, design, and implementation of the proposed system. An experimental evaluation in a line-of-sight (LOS) environment shows the effectiveness of the anchor nodes, whose position and antenna delay values are measured by the proposed system, in localizing a mobile node.

The ultra-wideband (UWB)-based real-time localization system (RTLS) is a promising technology for locating and tracking assets and personnel in real-time within a defined indoor environment since it provides high-ranging accuracy. However, its performance can be affected by the underlying antenna delays of UWB nodes, which act as a source of error during range estimations. Usually, measurement of the antenna delays is performed separately as a dedicated standalone procedure. Such an additional measurement procedure makes the UWB-based RTLS more tedious with manual interventions. Moreover, the air-time occupancy during the transmission and reception of signaling messages for range estimations between UWB node pairs also limits the serviceable capability of these networks. In this regard, we present a novel simultaneous ranging scheme that requires limited air-time occupancy during range estimations between UWB node pairs and also compensates for the error from the antenna delays. This paper provides a detailed mathematical modeling, system design, and implementation procedure of the proposed scheme. The effectiveness of the proposed scheme for locating a mobile node in an indoor environment is validated through experimental analysis. The results show that, compared to the state-of-the-art two-way ranging (TWR) method, the proposed scheme eliminates the requirement of dedicated standalone antenna delay measurement procedures of the nodes, increases air efficiency through the provision of simultaneous ranging, and provides relative root-mean-square errors (RMSEs) improvement for range and position estimations of approximately 54.52% and 39.96%, respectively.

Beam forming processing of adaptive antenna introduces distortions of group delay. For high-precision GNSS applications, the distortions cannot be ignored. In order to solve the problem, an evaluating method of adaptive array group delay based on availability beam is proposed. This method consists of three steps: firstly, setting the available beamwidth of the antenna; secondly, configuring different interference scenarios and calculating the group delay variation within the available beamwidth for each scenario; finally, averaging group delay variations obtained across different scenarios to derive the mean group delay variation. This method is applied to evaluate the group delay performance of four typical planar arrays under interference conditions. Experimental results indicate that the uniform circular array is the optimal high-precision adaptive antenna configuration under interference conditions. Additionally, by setting an appropriate available beam threshold, the stability of the average group delay of the adaptive antenna can be improved. The method can quickly and effectively evaluate the group delay of the adaptive antenna, and the evaluation results can serve as a reference for the performance assessment of high-precision GNSS adaptive antennas.

A compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) monopole antenna with extra Bluetooth band for various wireless applications is presented. The proposed antenna is composed of a modified ACS-fed structure and a staircase-shaped patch for covering the UWB band (3.1–10.6 GHz), which occupies a very compact size of 32.5 × 10 mm2. By etching a snake-shaped slot in the staircase-shaped patch, an additional band can be realised covering the Bluetooth band (2.4–2.484 GHz). Furthermore, the proposed antenna has been fabricated and measured, and good results obtained. The proposed antenna shows nearly omnidirectional radiation characteristics, relatively consistent group delays and stable gains in the operating bands. The simple feeding structure, compact size and uniplanar design make it easy to be integrated within portable devices for wireless communication.

Future satellite platforms and 5G millimeter wave systems require Electronically Steerable Antennas (ESAs), which can be enabled by Microwave Liquid Crystal (MLC) technology. This paper reviews some fundamentals and the progress of microwave LCs concerning its performance metric, and it also reviews the MLC technology to deploy phase shifters in different topologies, starting from well-known toward innovative concepts with the newest results. Two of these phase shifter topologies are dedicated for implementation in array antennas: (1) wideband, high-performance metallic waveguide phase shifters to plug into a waveguide horn array for a relay satellite in geostationary orbit to track low Earth orbit satellites with maximum phase change rates of 5.1°/s to 45.4°/s, depending on the applied voltages, and (2) low-profile planar delay-line phase shifter stacks with very thin integrated MLC varactors for fast tuning, which are assembled into a multi-stack, flat-panel, beam-steering phased array, being able to scan the beam from −60° to +60° in about 10 ms. The loaded-line phase shifters have an insertion loss of about 3 dB at 30 GHz for a 400° differential phase shift and a figure-of-merit (FoM) > 120°/dB over a bandwidth of about 2.5 GHz. The critical switch-off response time to change the orientation of the microwave LCs from parallel to perpendicular with respect to the RF field (worst case), which corresponds to the time for 90 to 10% decay in the differential phase shift, is in the range of 30 ms for a LC layer height of about 4 µm. These MLC phase shifter stacks are fabricated in a standard Liquid Crystal Display (LCD) process for manufacturing low-cost large-scale ESAs, featuring single- and multiple-beam steering with very low power consumption, high linearity, and high power-handling capability. With a modular concept and hybrid analog/digital architecture, these smart antennas are flexible in size to meet the specific requirements for operating in satellite ground and user terminals, but also in 5G mm-wave systems.

A compact printed antenna with three rejected bands has been examined and presented in this manuscript. This antenna is fed by a coplanar waveguide and operates over a wide range of frequencies. An arc-shaped, rectangular strip like and split-ring slot have been etched from the designed radiating patch to generate the rejection peaks at Wi-MAX, WLAN and X-band satellite communication. Primarily, the rectangular patch has been considered and further this patch is modified to acquire the UWB frequency spectrum from 3.1 to 10.6 GHz. The overall size of designed antenna is 27 × 27 × 1.6 mm 3 which comprises of novel structure of radiating patch and 50Ω CPW feed. After modification the final geometry of radiating patch, proposed antenna divulges the VSWR bandwidth of 11.88 GHz (2.12–14.0 GHz). Further, by introducing different types of slots in the final structure of radiating patch antenna exhibits Wi-MAX (3.16–3.76 GHz), WLAN (5.26–5.87 GHz) and X-band satellite communication (7.30–7.68 GHz) rejected bands. Furthermore, designed UWB antenna embellishes the gain of −7.64 dBi, −4.80 dBi and −4.92 dBi at rejected bands, whereas, the gain of antenna at other frequencies varies between 3.65 and 8.19 dBi. Proposed UWB antenna exemplifies the radiation efficiency variation in 77–98% except notched frequency bands. The radiation pattern and group delay of antenna is also at the acceptable level for existing UWB applications. Lastly, final optimized geometry of antenna with three band notched characteristics is being fabricated and verified for the validation of simulated results. Both the results are related and are found in good agreement with each other and also divulged that proposed antenna is eligible candidate for UWB applications with band rejection characteristics.

This study proposes a high-isolation four-port wideband MIMO antenna array designed for sub-6 GHz 5G, IoT, and radar applications. The array is fabricated on a polycarbonate substrate with overall dimensions of 500 × 500 mm2 (εr = 2.8, h = 1 mm). Four orthogonally arranged modified circular patches with triangular ground planes and optimized inter-element spacing (D1 = 90 mm) are employed in the antenna’s design to achieve an impedance bandwidth of 0.7–7.0 GHz (Fractional Bandwidth (FBW) > 163.63%) with |Sii| < −10 dB across all ports. The measurement results indicate that the inter-port isolation is better than 15 dB (worst-case) across the 0.7–7 GHz band, exceeding 25 dB over 63.5% of the bandwidth (with a peak of approximately 50 dB); the envelope correlation coefficient (ECC) is ultra-low (<0.008); the total active reflection coefficient (TARC) is less than −10 dB for primary multi-port excitations; the mean effective gain (MEG) is balanced (≈−3 dB); and the group delay is consistent (~0.5 ns). With a maximum realized gain of 10 dBi, the antenna exhibits omnidirectional radiation patterns, showing a significant correlation between the simulation (CST Microwave Studio) and measurement results. The proposed antenna is particularly well-suited for use in high-throughput sub-6 GHz 5G base stations and wideband wireless systems, offering superior port isolation through multi-mode resonance without the need for metamaterials and outperforming existing four-port designs.

Equal-arm detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set the overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers), the laser noise experiences different delays in the two arms and will hence not directly cancel at the photo detector. To solve this problem, a technique involving heterodyne interferometry with unequal arm lengths and independent phase-difference readouts has been proposed. It relies on properly time-shifting and linearly combining independent Doppler measurements, and for this reason it has been called time-delay interferometry (TDI). This article provides an overview of the theory, mathematical foundations, and experimental aspects associated with the implementation of TDI. Although emphasis on the application of TDI to the Laser Interferometer Space Antenna mission appears throughout this article, TDI can be incorporated into the design of any future space-based mission aiming to search for gravitational waves via interferometric measurements. We have purposely left out all theoretical aspects that data analysts will need to account for when analyzing the TDI data combinations.

In this work, two elements (with two versions) compat UWB MIMO antennas are designed and fabaricted. CST software is used in the simulation process. The two elements MIMO antenna have a size of 29.5 × 60 mm2. Measured S parameters show that the MIMO antennas work well from 3 GHz up to 20 GHz (representing the maximum working frequency of the measurent instrumnts). Mesurement results show that the isolation between the antenna elemnts is higher than 23 dB for the first version of the two elements UWB MIMO antenna. In addition, mesurement results show that the isolation between the antenna elemnts is higher than 30 dB for the second version of the two elements UWB MIMO antenna. Measurements show a channel capacity loss lower than 0.4 bps/Hz and a low group delay variation.