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Active integrated antennas (AIAs) are used in low-noise receivers for their good noise performance compared with their nonintegrated counterparts. However, it is challenging to accurately determine one of these antennas' most important characteristics: the noise figure (NF). To overcome the dependencies of the existing methods, we show a new method that can estimate the NF of a wireless system over-the-air (OTA), using a reverberation chamber (RC). Using the RC, we could create a consistent and repeatable measurement environment. Since this method characterizes the NF of the total system, it also includes factors such as noise matching. An extensive uncertainty analysis shows that the NF can be determined within only 0.7 dB expanded uncertainty in the frequency range from 21 to 29 GHz.

The transition to higher frequency bands, e.g.,millimeter-wave (mmWave) and terahertz (THz), will be capitalizedon the long term for future wireless communications.One of challenges relates to rapid establishment of mmWave/THzlinks with low beam training overhead due to highly directionaltransmission. A promising solution is to take advantage of thecoexistence of sub-6 GHz, mmWave, and THz wireless networksand to use out-of-band spatial information for enabling fastbeam search. The success depends on the spatial similarityof radio channels across different frequency bands. In thisarticle we promote a feasibility study of low-frequency spatialchannel information assisted high-frequency beam search froma radio channel point of view. We develop multi-band channelsimilarity measure of desired beam directions extracted fromradio channels, which are obtained via filtering propagation pathsby different beampatterns at different frequencies. Measurementandray-tracing-based evaluations across multiple frequenciesand environments are performed, which prove the usability ofout-of-band information aided beam search strategy in line-ofsight(LOS) dominated scenario and even in non-LOS scenario.Finally, we discuss the challenges associated with exploitingspatial channel similarity.

ispartof: IEEE Sensors Letters vol:6 issue:1 status: accepted

Few examples of individual polymer-based 3-D printed quasi-optical component types have been previously demonstrated above ca. 100 GHz. This paper presents the characterization of polymer-based 3-D printed components and complete subsystems for quasi-optical applications operating at G-band (140 to 220 GHz). Two low-cost consumer-level 3-D printing technologies (vat polymerization and fused deposition modeling) are employed, normally associated with microwave frequencies and longer wavelength applications. Here, five different quasi-optical component types are investigated; rectangular horn antennas, 90° off-axis parabolic mirrors, radiation absorbent material (RAM), grid polarizers and dielectric lenses. As an alternative to conventional electroplating, gold-leaf gilding is used for the polarizer. A detailed investigation is undertaken to compare the performance of our 3-D printed antennas, mirrors and RAM with their commercial equivalents. In addition, a fully 3-D printed, RAM-lined housing with central two-axis rotational platform is constructed for performing two-port measurements of a quasi-optical horn-mirror-polarizer-mirror-horn subsystem. Measured results generally show excellent performances, although the grid polarizer is limited by the minimum strip width, separation distance and metallization thickness. The ultra-low cost, `plug and play' housing is designed to give a fast measurement setup, while minimizing misaligning losses. Its RAM lining is designed to suppress reflections due to diffraction from components under test that may cause adverse multi-path interference. Our work investigates each component type at G-band and integrates them within subsystem assemblies; operating at frequencies well above those normally associated with low-cost consumer-level 3-D printing technologies. This opens-up new opportunities for rapid prototyping of complete low-cost front-end quasi-optical upper-millimeter-wave subsystems.

An enhanced spatial resolution brightness temperature product is proposed for future conical scan microwave radiometers. The technique is developed for Copernicus Imaging Microwave Radiometer (CIMR) measurements that are simulated using the CIMR antenna pattern at the L-band and the measurement geometry proposed in the Phase A study led by Airbus. An inverse antenna pattern reconstruction method is proposed. Reconstructions are obtained using two CIMR configurations, namely, using measurements collected at L-band by the forward (FWD) scans only, and combining forward and backward (FWD+BWD) scans. Two spatial grids are adopted, namely, 3km × 3 km and 36km × 36km. Simulation results, referred to synthetic and realistic reference brightness fields, demonstrate the soundness of the proposed scheme that provides brightness temperature fields reconstructed at a spatial resolution up to ~1.9 times finer than the measured field when using the FWD+BWD combination., This work has been produced for the European Space Agency (ESA) in the frame of the Copernicus programme as a partnership between ESA and the European Commission.

This work proposes and evaluates a hybrid Bayesian-based localization method to estimate the position of a target node using received signal strength and time of flight measurements. In our investigations, we consider these measurements are acquired through a distributed antenna system which is connected to a common master anchor node. The baseline non-hybrid scenarios use only received signal strength measurements to estimate the position of interest, while the hybrid implementation combines time of arrival measurements as well. Both Bayesian-based (non) hierarchical approaches approximates the posterior distribution of the target’s location coordinates using Markov Chain Monte Carlo methods. The hierarchical method introduces conditional interdependencies to the model parameters, resulting in less model variance. Herein, the root mean square error is used to evaluate the performance of the indoor test scenarios. Our results show that both hybrid and hierarchical approaches outperform the baseline Bayesian model, while the former significantly increase the accuracy the target position estimate.

[EN] In this letter, the dependence of the specular multipath components (SMC) and dense multipath components (DMC) to the interuser spatial correlation and sum-rate capacity of a massive multiuser multiple-input--multiple-output (MU-MIMO) setup is evaluated from measurements conducted inside an underground subway wagon at the 25-40 GHz candidate frequency bands for 5G systems. The radio channel consists in a 7 7 uniform rectangular array (URA) acting as access point for eight users uniformly distributed in the wagon. The DMC power ratio is observed to be distance- and frequency-dependent as the SMC and DMC exhibit different propagation mechanisms. Remarkably, it is reported that the interuser spatial correlation computed with DMC offers the best favorable propagation for a massive MIMO setup, whereas SMC contribute to the users correlation. Hence, correlation is found to be strongly dependent on the DMC ratio frequency characteristics. In addition, better interuser correlation and sum-rate capacity values are obtained as the frequency is increased. These results highlight the need to include DMC in 5G massive MIMO channel models and emulators to improve their accuracy at the system level., This work was supported in part by MINECO, Spain, under the National Projects TEC2016-78028-C3-2-P and TEC2017-86779-C2-2-R and in part by the ELSAT2020 OS4 SMARTIES program co-financed by the European Union with the European Regional Development Fund, the French state, and the Hauts de France Region Council.

BIANCHA (BIstatic ANechoic CHAmber) is a singular facility located at the premises of the National Institute for Aerospace Technology (INTA), Spain. It was devised to enable both monostatic and bistatic automatic positioning and, therefore, permits to perform a wide variety of electromagnetic tests. In this regard, it is worth noting that in the last years, a renewed interest has arisen in bistatic radar. Some of the main reasons behind this renaissance are the recent advances in passive radar systems added to the advantages that bistatic radar can offer to detect stealth platforms. On the other hand, with the aim of developing new aeronautic materials with desired specifications, research on the electromagnetic properties of materials has also attracted much attention, demanding engineers and scientists to assess how these materials behave in the presence of electromagnetic fields. Consequently, this paper introduces BIANCHA and demonstrates its applicability for these purposes by presenting results of tests for two different applications: a bistatic scattering analysis of scaled aircraft targets and the extraction of the electromagnetic properties of composite materials utilized in an actual aeronautical platform. This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO) within the project UAVEMI (TEC2013-48414-C3-2-R) and also partially funded by the North Atlantic Treaty Organization (NATO) Collaboration Support Office (CSO) within the works conducted in the NATO-STO SET-200 research group. Preprint

This correspondence discusses over-the-air (OTA) testing for multiple-input multiple-output (MIMO) capable terminals, with an emphasis on test zone size characterization for multi-probe anechoic chamber (MPAC) OTA configurations. For an MPAC setup, it is important to understand the test zone size that can be supported by its design. Further, it is desirable that the test zone size should be determined in terms of measured throughput deviation. However, such works have not been reported in the literature yet, due to challenges in practical MPAC setups. In this correspondence, we propose to simulate the MPAC OTA configuration and MS design in a channel emulator and perform MIMO throughput measurements in a conductive setup. With the proposed scheme, we can investigate how large a test zone can be supported for the synthetic MPAC configuration in terms of throughput deviation. This scheme is attractive, since various MS antenna designs and MPAC configurations can be flexibly selected and test zone size in terms of measured MIMO throughput deviation can be achieved. Measurement results show that with a high antenna correlation at the base station (BS) side, measured throughput results would be low, irrelevant to MPAC OTA designs and antenna designs at the MS side. Therefore, the antenna correlation at BS side should be set uncorrelated to ensure that true MS performance can be measured. Further, spatial correlation accuracy at the MS side becomes critical for throughput accuracy only when correlation values are in the high region (e.g., $\rho > 0.5$ ).

Interference between neighboring antennas operating in nearby frequency ranges can lead to damage of the front-end electronics. This letter presents the design of a frequency-selective surface (FSS) aimed at preventing the saturation of the low noise amplifiers of a phased-array radar antenna due to the carrier of a satellite communication antenna located in its proximity. A fast design was possible thanks to the integral equation method for the derivation of multimode equivalent networks (IEMEN) and was then validated by reflection and transmission measurements of a hardware demonstrator.

The paper presents the design and validation of a dual band feed system for the reflector antenna of the CoReH2O (Cold Regions Hydrology High-resolution Observatory) SAR instrument, investigated under ESA contract. The antenna is a dual linearly polarized single-offset reflector, illuminated by two side feed arrays operating in X and Ku band respectively. Each array comprises seven compact multimodal horns in quasi rectangular waveguide. The horns are sequentially excited, a couple at a time, for optimum antenna pattern synthesis and secondary beams overlap. Each horn is a multiple step rectangular waveguide structure that provides the proper modal content at aperture, very close to the benchmark patterns analytically synthesized by modal superimposition at feed apertures level. The RF design has been validated through a complete characterization by test of the feeding system, proceeding from the single feeding elements to a complete feeding system composed by 4+4 elements. The measured results showed very good agreement with predictions at each stage of the campaign. Measured pattern has been used as primary source in the antenna model and very good performance have been predicted on secondary beams.

A new indoor facility for electromagnetic measurements has been developed and built at the Detectability and Electronic Warfare Laboratory, INTA, Spain. The system was designed to extend the previous capabilities so that not only monostatic but also bistatic radar cross section (RCS) tests could be easily conducted. Due to limited space, far-field radar cross sections in the system are restricted to small targets, but this layout will allow the researchers to investigate ReS near-field-to-far-field transformations. The system was also conceived to be versatile enough to carry out other tests, such as near-field antenna measurements, material-absorption measurements, and electromagnetic characterization of materials. The paper describes the novel concept behind the facility, and presents some preliminary measurement results on different applications. The authors would like to acknowledge the contribution to this work of B. Priemer and M. Boumans from Orbit/FR, Germany, and of J. Valverde from Alava Ingenieros, Spain, and the helpful discussions maintained with them. Peerreview

Planar circularly symmetric (PCS) electromagnetic band-gap (EBG) substrates have recently been proposed to suppress surface waves (Llombart, N. et al., 2004). The application of PCS-EBG to reduce the surface waves excited by an antenna printed on a dielectric slab is discussed. The study starts from a reference microstrip-excited, slot-coupled dipole that presents a relatively large bandwidth (about 12%) and relatively low efficiency (about 40%-60%) due to surface wave losses. Some design considerations on how to enhance the performance of this antenna by surrounding it with a PCS-EBG are then presented. Finally the measured results are presented. These explicitly show the advantages of the proposed EBG substrate in terms of bandwidth and radiation pattern. A bandwidth of 20% is achieved without significant surface wave losses. The results also show radical improvements in the isolation between antennas printed on the same substrate.

[Abstract] As expressed in earlier works, if filled nulls are required in a power pattern generated by a Taylor line source, their corresponding roots must be complex. This leads to a multiplicity of solutions emerged from the fact that the power pattern keeps unaltered if the signs of the imaginary part of the roots are changed. In view of this attribute, the selection of the most favorable roots set, in terms of variability of amplitude excitation distribution, for example, is allowed. It is shown in this paper that, if the pattern is symmetric, a further consideration, never reported so far, can increase the number of available solutions.

[Abstract] C++ routines implementing the simple generalization of Simpson's rule to two dimensions for calculating antenna directivities compare well with methods currently available in common symbolic and numerical calculation packages.

[Abstract] Sidelobe-level and ripple behaviors of Ø-symmetric shaped patterns, generated by circular, real and complex, continuous Taylor distributions, is analyzed as a function of measurement distances. This paper reveals that real distributions suffer less-significant power pattern degradation than complex distributions at near-field distances.

[Abstract] We investigated variation in the bandwidths of ripple, sidelobe level, -3 dB beamwidth, and maximum element embedded (active) impedance (|Z/sup e/|/sub max/) among multiple collinear dipole arrays radiating a given flat-topped beam pattern. The main finding was that ripple and sidelobe level bandwidths are much greater than when the dipoles are parallel.

Summarization: In this paper a maximum likelihood estimator of the locations of passive RFID tags is presented, exploiting the Received Signal Strength Information (RSSI) collected at the reader. The reader-antenna is fixed on a moving cart and collects RFID data in the area of interest. Locations of the reader-antenna and of the target-objects are obtained by the RSSI of reference tags placed at known positions. The proposed method can be applied using commercial RFID equipment. Measurements were conducted in an office environment; mean error of 25cm with standard deviation equal to 12,4cm is recorded. Localization accuracy can be further improved by increasing the density of the reference tags and the number of reader antennas. Presented on