Ultra-wideband cork substrate-integrated-waveguide cavity-backed slot antenna

An ultra-wideband (UWB) substrate-integrated-waveguide (SIW) cavity-backed slot antenna covering the lower part of the 3.1-10.6 GHz block allocated to UWB transmission systems, being 3.1-3.6 GHz, is designed, constructed and validated. Owing to its planar topology, low profile and the use of cork substrate material, the proposed antenna may be integrated unobtrusively in any cork surface. Prior to the antenna design, the cork substrate material was characterized in the frequency band of interest. The design is conducted based on the average properties, while maintaining some impedance bandwidth margins to allow for varying cork material properties. A prototype is validated in free space conditions, confirming the high performance observed in simulation. An impedance bandwidth of 700 MHz (20.9%) is measured. At the center frequency 3.35 GHz, a radiation efficiency of 78%, a front-to-back ratio of 17.2 dB, and a maximum gain of 4.9 dBi are obtained. The maximum gain varies only by 1.4 dB within the frequency band of interest. The other far-field properties also vary only negligibly, which is the most important requirement to UWB antennas

SIW cavity-backed slot (multi-)antenna systems for the next generation IoT applications

Substrate integrated waveguide (SIW) cavity-backed slot antenna topologies are promising candidates to adress the specific design challenges posed by the Internet of Things (IoT). In this contribution, we demonstrate their potential by discussing two designs on two different, application-specific, innovative substrate materials. First, a compact, ultra-wideband three-element array with very low mutual coupling is presented for integration into furniture. In the second design, the half-mode SIW technique is applied to obtain a miniaturized ultra-wideband design, enabling invisible integration into cork floor and wall tiles. The compactness, integrability, and stable, high performance of both designs in different operating conditions, make them ideal candidates for IoT applications

SIW antennas as hybrid energy harvesting and power management platforms for the internet of things

A novel antenna-harvester co-design paradigm is presented for wireless nodes operating in an Internet of Things context. The strategy leads to compact and highly-integrated units, which are able to set up a reliable and energy-efficient wireless communication link, and to simultaneously harvest energy from up to three different sources, including thermal body energy, solar, and artificial light. The core of the unit consists of a substrate-integrated-waveguide (SIW) antenna. Its surface serves as a platform for the flexible energy-harvesting hardware, which also comprises the power management system. To demonstrate the approach, two different SIW cavity-backed slot antennas and a novel compact dual linearly polarized SIW antenna are presented. These topologies facilitate the integration of additional hardware without degrading performance. In the meantime, they enable comfortable integration into garments or unobtrusive embedding into floors or walls. Measurements on prototypes validate the integration procedure by verifying that the integrated hardware has a negligible influence on the performance of all discussed SIW antennas. Finally, measurements in four well-chosen indoor scenarios demonstrate that a hybrid energy-harvesting approach is necessary to obtain a more continuous flow and a higher amount of scavenged energy, leading to a higher system autonomy and/or reduced battery size

Half-mode substrate-integrated-waveguide cavity-backed slot antenna on cork substrate

A wideband half-mode substrate-integrated-waveguide cavity-backed slot antenna covering all Unlicensed National Information Infrastructure (U-NII) radio bands (5.15-5.85 GHz) is designed, fabricated, and validated. By a half-mode implementation of a multimoded cavity with nonresonant slot, a compact ultrawideband antenna is obtained with very stable radiation characteristics, owing to the excellent antenna/platform isolation. Cork material is applied as antenna substrate, making the proposed antenna suitable for integration into floors or walls. In free-space conditions, an impedance bandwidth of 1.30 GHz (23.7%), a radiation efficiency of 85%, a front-to-back ratio of 15.0 dB, and a maximum gain of 4.3 dBi at 5.50 GHz are measured. Performance is also validated when the antenna is deployed on various dielectric or conducting platforms and underneath different dielectric superstrates. Only the latter slightly detunes the antenna's impedance bandwidth. Yet, the complete frequency band of interest remains covered, owing to additional design margins incorporated in the requirements. Its compactness, unobtrusive integration potential, and stable high performance in different environments make this antenna topology an ideal candidate for Internet of Things applications

Distributed multi-user MIMO transmission using real-time sigma-delta-over-fiber for next generation fronthaul interface

To achieve the massive device connectivity and high data rate demanded by 5G, wireless transmission with wider signal bandwidths and higher-order multiple-input multiple-output (MIMO) is inevitable. This work demonstrates a possible function split option for the next generation fronthaul interface (NGFI). The proof-of-concept downlink architecture consists of real-time sigma-delta modulated signal over fiber (SDoF) links in combination with distributed multi-user (MU) MIMO transmission. The setup is fully implemented using off-the-shelf and in-house developed components. A single SDoF link achieves an error vector magnitude (EVM) of 3.14% for a 163.84 MHz-bandwidth 256-QAM OFDM signal (958.64 Mbps) with a carrier frequency around 3.5 GHz transmitted over 100 m OM4 multi-mode fiber at 850 nm using a commercial QSFP module. The centralized architecture of the proposed setup introduces no frequency asynchronism among remote radio units. For most cases, the 2 x 2 MU-MIMO transmission has little performance degradation compared to SISO, 0.8 dB EVM degradation for 40.96 MHz-bandwidth signals and 1.4 dB for 163.84 MHz-bandwidth on average, implying that the wireless spectral efficiency almost doubles by exploiting spatial multiplexing. A 1.4 Gbps data rate (720 Mbps per user, 163.84 MHz-bandwidth, 64-QAM) is reached with an average EVM of 6.66%. The performance shows that this approach is feasible for the high-capacity hot-spot scenario

A combination of transmission line models as design instruments for electromagnetically coupled microstrip patch antennas in the 2.45 GHz ISM band

This communication presents an analytical framework that combines transmission line models for the design of electromagnetically coupled microstrip patch antennas for the 2.45 GHz industrial, scientific, and medical band. It provides initial values for all dimensions of the antenna, with measured resonance frequency errors below 6%. The initial design is optimized in two subsequent phases to center the resonance frequency and to increase the impedance bandwidth (BW), obtaining measured resonance frequency errors below 0.6% and BW enhancements of more than 1.2 times the original ones, respectively. The model has been validated with antenna prototypes based on rigid and textile materials, exhibiting excellent free-space measured BW of 4% and 5.12%, maximal measured gains of 4.28 and 7.33 dBi, and radiation efficiencies of 63.4% and 71.8%, respectively. Moreover, very stable on-body performance is obtained, with minimal frequency detuning when deploying the textile antenna on the human body. The measured maximum on-body gain for the textile antenna equals 5.5 dBi, with a simulated specific absorption rate of 0.323 W/kg at 2.45 GHz

Self-interference cancellation enabling high-throughput short-reach wireless full-duplex communication

In-band full-duplex (FD) wireless communication allows the simultaneous transmission and reception of data at the same frequency band, effectively doubling the spectral efficiency and data rate while reducing the latency. Previously published designs mostly target the self-interference (SI) cancellation in conventional wireless systems. In this paper, we focus on real-time SI cancellation for short-reach wireless FD systems. The superior signal quality of a point-to-point short-reach wireless system, allows the utilization of wideband communications to achieve a high throughput. Besides, in such wireless systems, the impacts of phase noise and nonlinear distortions are largely reduced, easing the SI cancellation. Moreover, the degradation of signal reception quality due to FD operation is experimentally evaluated in different environments. Experimental results of a prototype implementation show that a combination of antenna isolation and digital cancellation can already achieve an overall SI cancellation performance of 72.5 dB over a bandwidth of 123 MHz. This prototype can support a high-data-rate FD communication link of close to 1 Gbps up to 300 cm with an error vector magnitude lower than -26 dB in a typical indoor environment

Biodegradable dual semicircular patch antenna tile for smart floors

A dual semicircular microstrip patch antenna implemented on a biodegradable substrate is presented for operation in the [863-873] MHz and [2.4-2.5] GHz frequency bands. To cover these frequency bands, two semicircular patches are compactly integrated onto a biodegradable cork tile, commonly found as support in laminate flooring, serving as a substrate. Thereby, the antenna tile may be seamlessly embedded as a sublayer of the floor structure. A higher-order mode is generated by applying via pins in the antenna topology to produce a conical radiation pattern with a null at broadside and sectoral coverage in the vertical plane. As such, the concealed floor antenna covers all azimuth angles of arrival in smart houses. The antenna performance is fully validated, also when the tile is covered by different polyvinyl chloride sheets. Owing to the supplementary design margins, the antenna impedance bandwidth remains covered. Moreover, the radiation patterns are measured in various elevation planes. Under standalone conditions, a radiation efficiency and a maximum gain of 74.3% and 5.8 dBi at 2.45 GHz and 48.1% and 2 dBi at 868 MHz are, respectively, obtained. Its omnidirectional coverage in the horizontal plane, stable performance on the inhomogeneous and biocompatible cork substrate and for various inhomogeneous superstrates, and its low-profile integration make the proposed antenna an excellent candidate for smart floors and smart houses