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The paper deals with the study of optically transparent and active square loop coplanar antennas in X-band. Frequency tunability of such antennas is provided by a surface mounted beam-lead varactor with micrometric dimensions, thus non-visible to the naked eye. The influence of the mesh dimensions on sheet resistance (from 0.05 Ω/sq to 0.50 Ω/sq), optical transparency (from 66% to 89%) and microwave...
The performance of a hybrid monopole antenna with solid and liquid materials is investigated. Sea water, distilled water and oil are injected into a dielectric structure, respectively. The influence of the feeding location, the distribution of the liquid, the length of the probe and other relevant factors are studied. The simulation results demonstrate that this antenna has a very good performance...
This paper presents the recent developments of gap waveguide technology and random-LOS OTA test technology. The applications on beam-steerable massive MIMO antennas and the characterization with random-LOS are emphasized.
A novel quasi-optical beamformer based on a continuous delay lens was designed, manufactured and tested. The wide band and wide scanning capability is demonstrated at Ku band, as well as low return loss at all input ports and low mutual coupling. The agreement between measurements and simulations is outstanding, for both the S parameters and the radiation patterns.
We report the design, fabrication and measurement of a dual-band polarization-independent terahertz reflectarray surface integrated on a silicon reflective substrate. The proposed device opens an important avenue for the integration of tunable elements in terahertz reflectarrays.
For THz communication systems, highly directive antennas are required to overcome the high free space path losses. For this reason, electrical beam steering is one of the key challenges for future applications. In this paper, a design for a first electrically steerable antenna operating at around 300 GHz is presented. The design is based on a phased array which consists of four horn antenna elements...
A review of some flat multi-beam antennas developed at IETR during the last 5 years (2010–2015) is reported. These antennas are based on quasi-optical and circuit-based beam forming networks (BFNs). The enhanced scanning capabilities of the proposed solutions will be shown. In addition, some antennas integrate antenna functions like monopulse techniques to enhance the angular resolution for tracking...
The inverse source technique is an accurate post processing and diagnostics method for antenna measurements [1-3]. Indeed, this technique has proven useful to suppress and filter disturbances in measurement scenarios such as presence of the feeding cable and mounting support [4-6]. Performing accurate measurements of on-chip antennas at millimeter wave frequencies is difficult in particular due to...
This paper describes a modular active antenna for satellite communications in the K/Ka band. The application is thought for mobile satellite communications and internet links, mainly for commercial airplanes. The impossibility to build full active antennas, including amplifiers in all the elements, leads to a modular semi active antenna. Here the module is a small subarray with complete phase control...
On-body propagation and on-body antennas for body-centric wireless communications are presented. The on-body communications rely on creeping waves launched and received by the antennas, respectively. Path gain and band-width at 2.4 GHz for different types of body-worn antennas for head-centric communications are presented. Further, an on-body channel model, to be used to find the optimal radiation...
Antenna current optimization is used to determine optimal currents in the antenna design region. The currents provide understanding, physical bounds, and figures of merits for antenna designs. The problem is formulated as a convex optimization problem expressed in the currents on the antenna structure. These convex optimization problems are solved with a computational cost comparable to a Method of...
The feasibility of measuring water vapor from the propagation delay of digital terrestrial broadcasting waves is under investigation. A real-time delay measurement system with software-defined radio technique is developed. In this paper, experimental results with this system using reflected waves are reported. We have succeeded in observing the propagation delay between the observing point and the...
In order to estimate the site diversity effect more accurately, we analyzed directional dependence of the site diversity using rain radar data measured in Japan. The expression of site diversity gain written in ITU-R P.618 says that diversity gain depends on the direction. However, we found that directional dependence cannot always be seen.
We statistically compared wind data at lower troposphere based on wind profiler radars with precipitation distribution data based on C-band weather radar in order to investigate the effects of interaction between terrain and lower wind on precipitation patterns in the Fukui plain. The results show detailed precipitation patterns in the Fukui plain are classified by wind at altitude lower than 1 km...
Characterization of convective rain at tropical station Kolkata, located near the land-ocean boundary, in the eastern part of India, has been made using observations from multi-frequency radiometer, micro rain radar, disdrometer and electric field monitor. Features of convective rain in respect of liquid water content, rain rate profile, and electric field variation have been identified. Multi-frequency...
A design of compact MIMO antenna achieving the band of LTE 700 for fourth generation (4G) technology is proposed and studied. A very compact meandered monopole using the spaces on the front side and back side of the substrate is adopted for the design. The overall size of the design is 60 × 35 × 0.8 mm3, and the antenna portion of the antenna is 20 × 35 × 0.8 mm3, implemented on the FR4 substrate...
A simple wave-traps multi-input multi-output (MIMO) antenna design is presented for wireless local area network (WLAN) operation. The measured −10 dB bandwidths for return loss are covering the WLAN2.4 and Wlan5.2/5.8 bands. The antenna structure is uncomplicated; it's composition by two symmetrically antennas and places on the clear-area which is at upper substrate. The proposed MIMO antenna system...
An improved version of effective diversity gain (EDG) evaluation system is proposed for multiple-input multiple output (MIMO) and diversity antennas. By enhancing the sensitivity of the RF power detection module and increasing rejection of background noises, measurements can now be conducted in actual propagation environments. The control computer is replaced with a laptop to improve system mobility...
Recently, the technology of MIMO (Multiple-Input Multiple-Output) using multiple antennas and CA (Carrier Aggregation) using multiple frequency bands are introduced in a mobile terminal. If plural MIMO antennas are installed closely, mutual coupling between the antennas must be reduced to suppress deterioration of radiation efficiency and increase of the correlation coefficient. In previous studies,...
In this paper, we discuss the inter-array decoupling technique suitable for MIMO full-duplex, which uses a combination of the end-fire antenna arrangement and eigen-beamforming. An experimental evaluation clarifies that the end-fire antenna arrangement contributes to the reduction of the inter-array coupling by 18.7 dB compared with the facing antenna arrangement, and that the small antenna aperture...
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