Antenna Architecture Research Articles

A Broadside Scanning Substrate Integrated Waveguide Periodic Phase-Reversal Leaky-Wave Antenna

A broadside-scanning half-mode substrate integrated waveguide periodic leaky-wave antenna architecture with antipodal tapered slots is presented. The antenna builds upon a previously proposed architecture by introducing a periodic phase-reversal of radiating elements. This enables the antenna to operate with a comparatively low substrate permittivity while maintaining grating-lobe-free scanning from reverse to forward endfire.

A Frequency-Reconfigurable Antenna Architecture Using Dielectric Fluids

A new frequency-reconfigurable antenna architecture is presented, in which a dielectric fluid is pumped into a cavity behind the antenna to change its resonant frequency. The continuous tuning provided by the changing fluid volume allows the resonant frequency to be adjusted to any value within the tunable range. This tuning method does not affect the power handling capability of the antenna and does not consume power while the resonant frequency is kept constant. This method of tuning also stands out in its class by offering a wide tuning range, high efficiency, and very good electrical isolation between the antenna and the control circuitry. The antenna was designed and optimized using Ansys HFSS software and several prototypes were built and tested. Measured results of the input response, radiation pattern, and efficiency are presented. Castor oil ( $\varepsilon_{r}=\text{2.7}$ ) and ethyl acetate ( $\varepsilon_{r}=\text{6}$ ) were used in physical tests as the tuning fluids to verify the simulated results. Good agreement between simulated and measured results was observed which is also in line with the behavior suggested by theory and earlier investigations.

Classification and characteristics of heat tolerance in Ageratina adenophora populations using fast chlorophyll a fluorescence rise O-J-I-P

Croftonweed originated from Mexico is a worldwide notorious invasive weed. The objectives of this study were to screen heat tolerance in different croftonweed populations, determine the effect of heat stress on two photosystems and probe the mechanism of acquired heat tolerance. According to conventional tests of plant injury and fast chlorophyll fluorescence rise kinetics, four different croftonweed populations collected from South China were successfully classified into three categories by exposing whole plants to heat treatment at 40°C: sensitive, intermediate, tolerant. Evidence from the JIP-test indicated that inhibition of the oxygen evolution complexes (OEC) and inactivation of PSII reaction centers (RCs) were the primary cause of heat damage. In mild heat stress (<40°C), slightly damaged the OEC without creating a visible K-step in the fluorescence rise OJIP curve. In moderate heat stress or stronger (≥40°C), a pronounced K-step due to irreversible severe damage on the OEC occurred. Additionally, inactivation of PSII RCs, down-regulation of energetic connectivity of PSII units, destruction of PSII antenna architecture, losing overall photosynthetic activity of PSII, increase of PSI activity also took place. Furthermore, the tolerant population had lesser damage degree on photosynthetic capacity relative to intermediate and sensitive populations. Finally, a reliable model, based on the most sensitive parameter PIABS and VK as a characteristic parameter for heat stress, is presented for ranking and identifying heat tolerance in different croftonweed populations. The heat sensitivity index (HSI) is also introduced as an indicator of plant heat sensitivity. The smaller the HSI value is, the higher the level of tolerance to heat stress is. We also found that the tolerance degree of four croftonweed populations to heat stress is significantly correlated to the extreme high temperature. This indicates that acquired heat tolerance in croftonweed populations results from plant adaptation to ambient high temperatures. Acquirement of heat tolerance confers a possible risk for croftonweed to spread further to currently hotter areas.

System scheme of radiofrequency radar detection for short-range targets using a self-rotating antenna architecture at millimeter wave

A new scheme of a pulse-Doppler radar for the effective detection of metal objects in a short range of millimeter waves is presented. An omnidirectional transmitting antenna (TXA) is used to provide full angular coverage while a directional receiving antenna (RXA) collects the coded signals for the determination of range and angle of the arriving signal. A Doppler shift is created by making RXA horizontally rotate along the axis of TXA, which creates a relative velocity between the RXA and the target under detection. It is shown that the system may detect targets as small as 0.2 m 2 with a high resolution.

SIW Pillbox Antenna for Monopulse Radar Applications

A multibeam pillbox antenna system incorporating monopulse phase comparison technique is proposed in the 24-GHz band. This low-profile antenna architecture combines the scanning capabilities of pillbox configurations and enhanced resolution of two-quadrant monopulse technique; this approach avoids mechanical orientation of the antenna system for tracking applications. The radiating panel consists of two subarrays of 23 slotted waveguides, with 8 slots per waveguide. The beam is scanned in E-plane over a field of view of $\pm {\bf 40}^\circ $ , and sum/difference patterns are generated in H-plane. Around the design frequency, ${\bf f} = {\bf 24}.{\bf 15}\,{\bf GHz}$ , the antenna gain varies between 25 and 21.5 dBi for the central and extreme beams, respectively. The measured null depth is better than $- {\bf 16}\;\text{dB}$ for all difference beam patterns. The antenna bandwidth for ${\bf VSWR} ( ${\textbf{S}_{\textbf{ii}}} ) and isolation better than ${\bf 10}\;{\bf dB}$ ( ${\textbf{S}_{\textbf{ij}}} ) is equal to 4.5%.

Development of UAS Design Based on Wideband Antenna Architecture

An Unmanned Aerial System (UAS) has been developed which is based on an aerodynamically functionalized planar wideband antenna. The antenna utilizes a planar circular dipole metallization scheme. The aerodynamic structure implements a planform similar to the Nutball flier, a hobbyist flight architecture. The resulting codesign achieved a large impedance bandwidth defined by a voltage standing wave ratio (VSWR) less than 2 from 100 MHz to over 2 GHz and omnidirectional dipole-like radiation patterns at the lower frequency region and more directional patterns at higher frequencies.

A Transportable Reflectarray Antenna for Satellite Ku-band Emergency Communications

The design of a Ku-band reconfigurable reflectarray antenna for emergency satellite communications is presented. Bidirectional high data rate satellite links are needed in emergency conditions where other telecommunication infrastructures are not available. In order to operate in this type of scenario, an antenna should be deployable, transportable, and easily repointable. The need of an automatic and fast satellite location and pointing system leads to a completely electronic reconfigurable antenna. The operative bandwidth is from 10.7 to 12.5 GHz for reception and from 14 up to 14.5 GHz for transmission (30% of relative bandwidth). The selected antenna architecture is based on a dual reflectarray system comprising a passive subreflectarray and an active main reflectarray made of reconfigurable 1-bit elementary cells based on PIN diodes.

On the behaviour of a compact antenna system with non-resonant elements in the presence of the human head

A novel handset antenna technique to solve the increasing demand of mobile bands, the loading effects (mismatching and efficiency losses) and the power absorption introduced by the head is analysed in terms of bandwidth, efficiency and SAR (specific absorption rate). The technique proposed integrates non-resonant elements and its results are compared with those obtained by a planar inverted-F antenna. The main antenna parameters (bandwidth, efficiency in free-space, efficiency regarding the human head presence and SAR) are compared in terms of electromagnetic simulation and measurements. The study concludes that the novel antenna architecture achieves multiband operation from 824–960 MHz and 1710–2170 MHz and become robust to human loading while occupying a reduced volume of just 250 mm3 in a typical handset phone.

Correction to “A Connected Array of Slots Supporting Broadband Leaky Waves” and “Wideband Dielectric Lens Antenna With Stable Radiation Patterns Fed by Coherent Array of Connected Leaky Slots” [Apr 13 1986-1994 and Apr 14 1895-1902

The authors acknowledge that the work described in their recent papers (ibid., vol. 61, no. 4, pp. 1986-1994, Apr. 2013 and ibid., vol. 62, no. 4, pp. 1895-1902, Apr. 2014) was supported by ERC Starting Grant ERC-2011-StG Grant "Advanced Antenna Architectures for THz Sensing Instruments (AAATSI)," No. 278794.

Performance Analysis of the Multiple Antenna Asynchronous Cognitive MAC Protocol in Cognitive Radio Network for IT Convergence

Multiple antenna technology for wireless communications is becoming mature and wide ranging in the wireless broadband network. Many spectrum usage measurement reports have shown that inaccurate spectrum sensing will waste spectrum resources. A Multiple Antenna Asynchronous Cognitive MAC (MAAC-MAC) protocol is proposed through introducing a multiple antenna architecture and power control mechanism into the hardware-constrained cognitive MAC (MHC-MAC) protocol with Asynchronous-Assembly Line Mode in cognitive radio network. In the spectrum sensing stage, the protocol makes use of multiple antennas to perform spectrum sensing and positioning, aimed at improving spectrum sensing and detection performance. During the negotiation phase, the CU (Cognitive User) access power control mechanism fully utilizes the licensed band without interfering PU (Primary User) and also increases the transmission rate and system throughput. It may be used for improved positioning and location-based services both indoors and outd...

A Quad-Band Antenna for Public Safety Applications

The design, fabrication, and characterization of a frequency-reconfigurable antenna for the United States Public Safety (PS) wireless communication applications are presented. This antenna is quad-band operating in the PS bands-220, 470, 800, and 4960 MHz. It is an electrically small antenna with calculated ka similar to 0.55 at 220 MHz. The antenna has two reconfigurable modes of operations. In mode 1, 220-, 470-, and 4960-MHz bands are excited. Mode 2 provides operation over 800- and 4960-MHz bands. This dynamic frequency reconfiguration is accomplished by two radio frequency microelectromechanical systems switches strategically located within the antenna architecture. The measured and simulated results for impedance and radiation characteristics agree well, where similar to 3%, 4%, 21%, and 17% fractional bandwidths have been measured in the four bands, respectively, while maintaining integrity of radiation pattern.

Wideband Radar Cross Section Reduction of Slot Antennas Arrays

A comprehensive analysis aimed at reducing the radar cross section (RCS) of array antennas, preserving at the same time their radiating performance, is presented. A microstrip slot array is considered as a test case to illustrate the proposed strategy for radar cross section reduction (RCSR). It is shown that a remarkable reduction of the radar signature can be accomplished over a frequency band as wide as two octaves by employing an array of periodic resistive elements in front of the radiating apertures. The monostatic and bistatic RCS of the proposed structures are investigated both for normal and oblique incidence. Different arrangements and geometries of the periodic resistive pattern are thoroughly analyzed showing the benefits and the drawbacks in terms of antenna gain and level of the scattered fields. Furthermore, the use of metallic parasitic elements for enhancing the antenna gain is considered, and the scattering phenomena caused by their presence are addressed, taking into account the appearance of grating lobes. The antenna designs are also analyzed by resorting to a bidimensional color plot presenting the variation of the reradiated field both in frequency and spatial domain. The guidelines illustrated by the proposed examples can be easily applied to other antenna architectures.

ON THE SCANNING PROPERTIES OF IMAGING ANTENNAS BASED ON DUAL CONFOCAL PARABOLOIDAL REFLECTORS

In this paper the scanning properties of dual re∞ector antenna systems constituted by two confocal paraboloidal re∞ectors fed by a planar array are investigated. This antenna architecture combines the interesting features of re∞ectors and array antennas. Because of the ofiset conflguration the radiation pattern exhibits an anomalous deviation in the beam pointing when the beam is scanned out of the boresight direction. Heuristic equations, representing an extension of the linear equations available in the literature, are derived, which permit predicting the pointing direction of the overall system as a function of the pointing direction of the feeding array in a signiflcant fleld of view.

Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review

Advances in reflectarrays and array lenses with electronic beam-forming capabilities are enabling a host of new possibilities for these high-performance, low-cost antenna architectures. This paper reviews enabling technologies and topologies of reconfigurable reflectarray and array lens designs, and surveys a range of experimental implementations and achievements that have been made in this area in recent years. The paper describes the fundamental design approaches employed in realizing reconfigurable designs, and explores advanced capabilities of these nascent architectures, such as multi-band operation, polarization manipulation, frequency agility, and amplification. Finally, the paper concludes by discussing future challenges and possibilities for these antennas.

Advanced Strategy for Large Antenna Array Design With Subarray-Only Amplitude and Phase Control

An advanced version of the Contiguous Partition Method (CPM) aimed at designing subarrayed antenna arrays with control of the excitation amplitudes and phases only at the subarray level is presented. Starting from the quantized distribution of the amplitude weights yielded through the optimal excitation matching procedure based on the CPM, a successive phase-clustering of the array elements belonging to each CPM amplitude aggregation is carried out to further simplify the antenna architecture still keeping the wide angular sector steering property of the array. A set of representative results is reported and discussed to assess the features and potentialities of the proposed technique.

Reconfigurable Thinning for the Adaptive Control of Linear Arrays

Dealing with the adaptive nulling of the array radiation pattern, two reconfigurable thinning strategies are presented and assessed. An easily-reconfigurable and low-complexity antenna architecture is considered where a set of radio-frequency switches is exploited to either connect or disconnect the array elements for controlling the radiation pattern and generating deep nulls along the directions-of-arrival of the undesired signals. By defining through a genetic algorithm-based optimization the on/off status of the switches to maximize the signal-to-interference-plus-noise ratio at the antenna output, two different formulations are discussed. The first one does not constrain the number of active elements, while the other forces the solution to satisfy a fixed-directivity criterion also in correspondence with a time-varying interference scenario. The performances of the proposed approaches are assessed in both static and time-varying scenarios where single and multiple interfering signals impinge on the array from different angular directions.

Special issue on S‐band mobile satellite technologies

This special issue of the Wiley International Journal of Satellite Communications and Networking hosts a selection of papers related to S-band mobile satellite R&D activities recently completed in the frame of the European Space Agency ARTES programs. The S-band allocation to hybrid satellite and terrestrial services in Europe 2009 and in other parts of the world has attracted operator, industry, and research institution interest for its commercial exploitation. The aim is to illustrate the most recent technical achievements either to improve the S-band satellite system performance or to demonstrate with prototypes the feasibility of new technologies in the user terminal receivers. Dealing with mobile satellite communication services in S-band, the reference air interface for all these scientific papers is the Digital Video Broadcasting - Satellite services to Handhelds (DVB-SH) standard [1], designed to support high-quality broadcasting services over the harsh land mobile satellite (LMS) channel while at the same time able to exploit the presence of terrestrial gap fillers. DVB-SH represents a state-of-the-art air interface for hybrid satellite/terrestrial mobile broadcasting (interactive) networks [2]. In [3], the authors have summarized key findings of an in-depth analysis of the benefits provided by different system architectures and technologies for next generation S-band mobile satellite broadcasting network with interactivity. Along with advanced antenna and payload architectures, a promising way forward in this context is the migration from the conventional single polarization per beam to an advanced dual polarization per beam MIMO architecture for effective spectrum exploitation. In this context, system capacity simulations are showing potential improvements in a 60% to 90% range in terms of overall throughput. Two leading European antenna manufacturers present in [4] and [5] their user terminal antenna prototypes to primarily target professional automotive applications. The main aspects of antenna design are introduced, and the performance of switchable dual polarized vehicular transmit/receive antennas is validated. The form factor of the antenna design described is not only fully in line with typical automotive commercial requirements but also suitable for other markets such as the maritime or the machine-to-machine ones. The aim of [6] is to review the state-of-the-art techniques and architectures supporting beamforming in mobile satellite systems and to evaluate the potential benefits/drawbacks of on-ground beamforming compared to on-board beamforming approach. For this analysis, also some of the beamforming error sources, such as propagation effects at feeder link level, on-board degradations at payload level, differential atmospheric perturbations and Doppler shift effect have been investigated. Finally, a preliminary assessment of the potential advantages given by adopting adaptive beamforming and more advanced on-ground signal processing techniques in multi-spots mobile satellite systems is presented. Stimulated by the large capacity increase potential provided by the dual-polarized S-band satellite systems, the authors in [7] derive a comprehensive MIMO channel model. This paper describes the joint wideband and narrowband modeling approach, provides examples of the usage, and finally describes some evaluation results. This new MIMO model for a dual-polarized LMS-channel environment has been evaluated by comparing the simulated results with data gathered from an extensive field trials carried out within the duration of the project.

Next generation interactive S‐band mobile systems: challenges and solutions

ABSTRACTThis paper summarizes the outcome of an investigation activity aimed at analyzing the benefits of new possible system architectures and technologies for next generation S‐band mobile satellite interactive/broadcasting networks (Figure 1). The main purpose was to achieve a higher capacity, and the main efforts in this direction were devoted to the investigation on possible migration from the conventional single polarization per beam to an advanced dual polarization per beam architecture for effective spectrum exploitation. In addition, advanced antenna and payload architectures have been also investigated. The system capacity results highlight potential improvements in a 60% to 90% range in terms of system throughput. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Capacity of multiple beamformed spatial stream transmission in millimetre‐wave communication channels

This study deals with the study on the performance of the hybrid transmission scheme combining both beamforming and spatial multiplexing for multiple spatial streams. The capacity of the hybrid scheme is evaluated and compared with that of the beamforming scheme for a single spatial stream in both line-of-sight and multi-path channels. Two kinds of hybrid schemes are considered: the shared antenna architecture, where each antenna processes all spatial streams and the split antenna architecture, where each antenna processes only one spatial stream. The effects of the channel parameters, such as the antenna spacing, the existence of reflected paths etc. On the capacity and the optimal beams and powers are examined. The frequency-selective property of the capacity and optimal beams and powers are also investigated. In this study, a scenario is assumed, where the same analogue radio frequency (RF) beamforming vector (or matrix) is applied to all subcarriers whereas the digital baseband power allocation is executed individually at each subcarrier.

Reconfigurable sum–difference pattern by means of parasitic elements for forward‐looking monopulse radar

This study describes the design of forward-looking monopulse arrays able to reconfigure the radiation pattern from the sum mode to the difference one by electronically switching a set of parasitic dipoles placed in front of a driven array of radiating dipoles. The antenna architecture is synthesised by optimising the geometric parameters of the passive elements, namely their positions and lengths. The generation of the difference beam is yielded by imposing a phase displacement of π to the excitations of half active array and activating the parasitic array by turning-on the switches that partition their lengths. As for the sum pattern, the effect of the parasitic dipoles is made negligible by turning-off the switches. A set of representative results is reported and discussed to show the effectiveness of the proposed approach.