Independent Antennas Research Articles

A single-sided meandered-dual-antenna structure for UHF RFID tags

A meandered-dual-antenna structure is proposed for UHF radiofrequency identification (RFID) tag. It is composed of two independent antennas printed on the one side of the substrate board. One of the antennas is exclusively used for receiving and harvesting sufficient energy to the tag chip having the complex conjugate impedance of the receiving antenna. The other is for backscatter to enhance maximum differential radar cross-section with purely real input impedance, to enhancement the read range. The receiving antenna is formed by a rectangular loop and a parasitic meandered line. The rectangular loop is used as a feeding element for the meandered line. The backscattering antenna is made using a meandered dipole along with a thin rectangular strip. The input impedance of the receiving antenna is designed to be conjugate matched to the chip impedance (13.5-j110 Ω), whereas the input impedance of backscattering antenna alternatively switched to open and short circuit for modulating the backscattered field. The input impedance of receiving and backscattering antennas is measured using differential probe technique. The simulated and measured results are found in good agreement. It is also demonstrated that the read range of UHF RFID system increased considerably by using the dual-antenna structure.

Control of randomly scattered surface plasmon polaritons for multiple-input and multiple-output plasmonic switching devices

Merging multiple microprocessors with high-speed optical networks has been considered a promising strategy for the improvement of overall computation power. However, the loss of the optical communication bandwidth is inevitable when interfacing between optical and electronic components. Here we present an on-chip plasmonic switching device consisting of a two-dimensional (2D) disordered array of nanoholes on a thin metal film that can provide multiple-input and multiple-output channels for transferring information from a photonic to an electronic platform. In this device, the surface plasmon polaritons (SPPs) generated at individual nanoholes become uncorrelated on their way to the detection channel due to random multiple scattering. We exploit this decorrelation effect to use individual nanoholes as independent antennas, and demonstrated that more than 40 far-field incident channels can be delivered simultaneously to the SPP channels, an order of magnitude improvement over conventional 2D patterned devices.

Wideband Double Monopole for Mobile, WLAN, and C2C Services in Vehicular Applications

In this letter, a three-dimensional antenna solution for automotive applications is presented. The proposed solution is formed by two independent antennas, perpendicularly placed inside a plastic cover with a shark-fin shape. The antennas, designed with low-cost materials, exhibit omnidirectional radiation patterns in the azimuthal plane. The first antenna is a double-shorted monopole that provides service from 698 to 960 MHz (in the LTE700, GSM850, and GSM900 bands), whereas the second antenna is a drop-shaped monopole that operates from 1.7 to 2.7 GHz (in the DCS1800, PCS1900, WCDMA2100, WLAN2400, LTE2600, WiMAX2350, and Wi-Fi at 2.4-GHz bands), and from 5.1 to 6 GHz (in the Wi-Fi at 5 GHz and C2C bands). Results show a good matching and radiation efficiency at all bands.

Dual‐band antenna with combination of printed dipole and aperture coupled rectangular patch antenna

ABSTRACTIn this letter, a novel simple structure of dual band microstrip antenna is presented. The antenna configuration is composed of two antennas that one of these antennas is printed dipole antenna and the other one is 1 × 2 aperture coupled rectangular patch antenna array. The parameter design of each antenna, which resonating as independent antennas, is designed based on their resonating frequency. The prototype of this antenna is fabricated and measured. The measured results show a good S‐parameter, reasonable gain, and stable omni‐like radiation patterns in two working frequency bands. According to measured results, the proposed dual‐ band antenna can cover 2.03–2.90 GHz, and 4.80–5.09 GHz, which are allocated for wireless applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:186–188, 2017

Multidirectional Receiving System for RF to dc Conversion Signal: Application to home automation devices

In this article, we present an original solution for radio frequency (RF) to dc conversion with multiple antennas. The presented device operates at 2.45 GHz. It combines passive parasitic element antennas (PEAs) and RF to dc converters. The proposed device collects the RF energy with six independent antennas and realizes the conversion and summation of the dc voltages. The objective is to perform uniform coverage of a room with a gain superior to a single and omnidirectional antenna. The typical application can be energy harvesting or detection for the command unit in home automation. This last application is our goal, and interest in the solution has been demonstrated through an application that aims at reducing standby mode consumption of electronic devices. The article focuses on the critical points to realize an efficient summation. The whole system has been designed and manufactured to work in rooms from 3 m to 15 m wide. The measured performances have been validated.

A Performance Comparison of Spatial Multiplexing MIMO Detectors

Many techniques are used in MIMO for various purposes, such as SM (spatial multiplexing), SD (spatial diversity) and antenna beam forming. Among them spatial multiplexing is used in MIMO for accommodating high data-rates applications. In, SM, independent information sequences called as layers are simultaneously transmitted from independent antennas. So, the overall bit-rate compared to single antenna system is thus largely enhanced without requiring extra bandwidth or extra transmission power. However during transmission through channel, individual layers are overlying with each other and MSI (multi stream interference) will occurs at the receiver. So, it is very difficult to obtain intended symbol from the bunch of streams. To solve out this problem of MSI various approaches have been proposed, which provides efficient approximate solution of the detection problem at receiver. Such as zero forcing (ZF), minimum mean square error (MMSE), successive interference cancellation (SIC), Ordered successive interference cancellation (OSIC). In this paper error performance of these SM detection schemes are investigated. They are compared on the basis of their BER performance. General Terms Spatial Multiplexing, MIMO Detectors

Current state of the art of regional hyperthermia treatment planning: a review.

Locoregional hyperthermia, i.e. increasing the tumor temperature to 40–45 °C using an external heating device, is a very effective radio and chemosensitizer, which significantly improves clinical outcome. There is a clear thermal dose-effect relation, but the pursued optimal thermal dose of 43 °C for 1 h can often not be realized due to treatment limiting hot spots in normal tissue. Modern heating devices have a large number of independent antennas, which provides flexible power steering to optimize tumor heating and minimize hot spots, but manual selection of optimal settings is difficult. Treatment planning is a very valuable tool to improve locoregional heating. This paper reviews the developments in treatment planning software for tissue segmentation, electromagnetic field calculations, thermal modeling and optimization techniques. Over the last decade, simulation tools have become more advanced. On-line use has become possible by implementing algorithms on the graphical processing unit, which allows real-time computations. The number of applications using treatment planning is increasing rapidly and moving on from retrospective analyses towards assisting prospective clinical treatment strategies. Some clinically relevant applications will be discussed.

Achieving Antenna and Multipath Diversities in GLRT-Based Burst Packet Detection

Robust detection of the arrival of a packet is challenging in burst wireless communications, because the detection performance is vulnerable to channel fading. In this paper, we study strategies to achieve diversity to combat with channel fading in the detection regime. The contributions of this paper are twofold. (i) The cyclic-delay diversity (CDD) combined with multiple-antenna generalized-likelihood-ratio-test (GLRT) detection is proposed to achieve both antenna and multipath diversities in the detection regime, in both time domain (TD) and frequency domain (FD), where the multipath diversity is obtained by CDD. (ii) GLRT detectors with multiple antennas under frequency-selective multipath fading channel in TD and FD, i.e., TD-GLRT and FD-GLRT, are derived. Miss-detection probability (MDP) and false-alarm probability (FAP) of TD-GLRT and FD-GLRT are analyzed, based on which, the diversity gains of both detectors are obtained. Results show that full diversity, offered by both independent antennas and multipath components, is achieved with the proposed approach for both TD-GLRT and FD-GLRT, no matter whether the assisted sequence has a perfect autocorrelation property or not. In addition, for TD-GLRT, assisted sequences with a non-perfect autocorrelation property may lead to a significant SNR loss due to multipath, while for FD-GLRT, the SNR loss is insignificant.

SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS

SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150-MHz all-sky map of Landecker & Wielebinski (1970):subtracting an offset of 21.4 K and scaling by factor 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range -2.3 to -2.45 in the 110 to 175 MHz band and indicates that the region towards the Galactic bulge has a relatively flatter index.

Characterizing the Impact of Feedback Delays on Wideband Rate Adaptation

In contemporary orthogonal frequency division multiplexing (OFDM) systems, such as Long Term Evolution (LTE), LTE-Advanced, and WiMAX, a codeword is transmitted over a group of subcarriers. Since different subcarriers see different channel gains in frequency-selective channels, the modulation and coding scheme (MCS) of the codeword must be selected based on the vector of signal-to-noise-ratios (SNRs) of these subcarriers. Exponential effective SNR mapping (EESM) maps the vector of SNRs into an equivalent flat-fading SNR, and is widely used to simplify this problem. We develop a new analytical framework to characterize the throughput of EESM-based rate adaptation in such wideband channels in the presence of feedback delays. We derive a novel accurate approximation for the throughput as a function of feedback delay. We also propose a novel bivariate gamma distribution to model the time evolution of EESM between the times of estimation and data transmission, which facilitates the analysis. These are then generalized to a multi-cell, multi-user scenario with various frequency-domain schedulers. Unlike prior work, most of which is simulation-based, our framework encompasses both correlated and independent subcarriers and various multiple antenna diversity modes; it is accurate over a wide range of delays.

A Fluidic Loading Mechanism in a Polarization Reconfigurable Antenna With a Comparison to Solid State Approaches

This work proposes a polarization-reconfigurable antenna composed of two independent, co-located, and orthogonal (“crossed”) narrow microstrip patch antennas with a novel pressure-driven fluidic loading network. Repeating and alternating high-low dielectric constant fluids in the network excite the two patches independently through capacitive coupling. A second iteration of this design with RF PIN diodes allows for a comparison between the fluidic reconfiguration mechanism and current state-of-the-art approaches. Circuit models for the antenna with each reconfiguration mechanism are developed to better understand the impacts on antenna performance. Furthermore, these models show good agreement with full-wave simulations and measured results taken from the two fabricated prototype antennas. Pattern data shows good linear polarization switching with both designs. The two mechanisms are compared based on the impact to electrical size, radiation patterns, efficiency, and switching speed.

Propagating spectroscopy of backward volume spin waves in a metallic FeNi film

We report a propagating spin wave spectroscopy for a magnetostatic backward volume spin wave in a metallic Fe19Ni81 film. We show that the mutual-inductance between two independent antennas detects a small but clear propagation signal of backward volume spin waves. All experimental data are consistent with the time-domain propagating spin-wave spectroscopy. The control of propagating backward spin wave enables to realize the miniaturize spin-wave circuit.

Design of Planar Trapezoidal Toothed Log Periodic Antenna using HFSS

Log Periodic Antenna is required to provide wide band width, high gain and broad beam width. This antenna has smaller dimension than other antenna types. This antenna is a type of frequency independent antenna. It is observed from the study that antenna on Teflon substrate provides widest bandwidth among all the substrate antennas. Further, the performance of antenna on Teflon substrate is better than conventional antennas.

Detecting cosmic rays with the LOFAR radio telescope

The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first $\sim 2\,\mathrm{years}$ of observing, 405 cosmic-ray events in the energy range of $10^{16} - 10^{18}\,\mathrm{eV}$ have been detected in the band from $30 - 80\,\mathrm{MHz}$. Each of these air showers is registered with up to $\sim1000$ independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.

Analysis of Improved Cyclostationary Detector with Multiple Antennas over Fading Channels

A comprehensive performance analysis of the multi-cycle cyclostationary (MC) detection-based spectrum sensing over fading channels with multiple independent and correlated antennas is developed. We first proposed an improved MC detector, aiming to reduce the computational complexity of the conventional one. Compared with conventional MC detector, the proposed method is low-computational complexity and high-accuracy on sensing performance. Based on the proposed MC detector, for the multiple independent antennas case, the average detection probability by employing square-law combining (SLC) is derived for several fading channels such as Nakagami, Rayleigh and Rician by using the moment generation function (MGF) approach. For multiple correlated antenna case, with Nakagami fading and SLC scheme, expressions of detection probability are derived by the same approach as it in the independent antennas case. Special cases of a linear array of 2 and 4 arbitrarily correlated antennas are treated. Finally, illustrative and analytical results show that the reliability of our proposed MC detector and the degradation of sensing performance over correlation and fading.

A Single-FPGA Real-Time Dual Beam-Former With FX Correlation Capabilities: First Results at the Nançay Radio Telescope With the FAN Antenna Array

A full-time beam-former for two independent antenna groups, with visibility computation capabilities at a slower rate, has been formerly designed on a single FPGA for the BAO-radio instrument, a radio telescope demonstrator for the study of dark energy by the observation of Baryonic Acoustic Oscillations (BAO) spectrum with HI probing technique. On the same hardware platform, a firmware, dedicated for the Focal Array at Nançay (FAN) project, can provide a full-time dual beam-forming on a single antenna array. It can process an incoming data flow of twelve channels, each organized as complex spectrum (2 × 8 bits) of 4096 frequencies with a 4 GbPS effective rate. The dual-beam capability of the system has been successfully tested on the FAN array with transits on the radio sources CasA and 3C123, the beam-former being configured by complex coefficients computed from a previous off-line software correlation on CasA. Recently, another beam-forming on 3C123 has been done after a calibration on CasA performed by the beam-former itself, set in correlation mode, and a source-tracking.

On the Frequency-Independent Modes of a Four-Arm Modulated Arm Width Spiral

This paper shows that among frequency independent (FI) conformal antennas, the modulated arm width (MAW) spiral has the simplest architecture for measuring both polarization and angle-of-arrival (AOA) instantaneously if frequency is known. The theory, design and performance of equiangular four-arm MAW spiral antennas when utilizing both sum modes (± 1) and difference mode ( +2) for direction-finding applications are discussed. It is shown that simultaneous dual-polarization and multi-mode capability is not achievable in more commonly-used four-arm spiral and sinuous antennas. While the co-polarized modes 1, 2 and 3 are well-researched with single-polarized four-arm equiangular spirals, they have not been utilized or controlled on a four-arm MAW spiral. Effects of modulation period on cross-polarization, pattern symmetry, gain, and impedance for all three pattern modes are investigated. The studies are carried out using full-wave modeling and a prototype MAW geometry is built and evaluated with a beamformer to demonstrate its wideband, dual-polarized, multi-mode capability.

An Octave Bandwidth Frequency Independent Dipole Antenna

Precision measurements of the spectrum of the cosmic radio background require frequency independent antennas of small electrical dimensions. We describe the design of a wide-band fat-dipole antenna with a sinusoidal profile having a frequency independent performance over the octave band 87.5 to 175 MHz. The input return loss exceeds 15 dB and the radiation power pattern is frequency invariant and close to cosine square over the octave bandwidth. The structure has been optimized using electromagnetic modeling, and the design has been validated by constructing a prototype.

Spectrum Sensing under Correlated Antenna Array Using Generalized Detector in Cognitive Radio Systems

We derive the probability of false alarm and detection threshold under employment of the generalized detector (GD) in cognitive radio (CR) systems for two scenarios: firstly, the independent antenna array elements; the secondly, the correlated antenna array elements. The energy detector (ED) and GD spectrum sensing performances are compared under the same initial conditions. The simulation results show that implementation of the GD improves the spectrum sensing performance in CR systems both for independent and correlated antenna array elements.

Exploring the Dark Ages and Epoch of Reionization with the HI 21 cm signal

Observations of the HI 21 cm transition line promises to be an important probe into the cosmic Dark Ages and Epoch of Reionization. Detection of this redshifted 21 cm signal is one of the key science goal for several upcoming and future low frequency radio telescopes like Murchison Widefield Array (MWA), Precision Array to Probe Epoch of Reionization (PAPER), LOw Frequency ARray (LOFAR) and Square Kilometer Array (SKA). One of the challenges for the detection of this signal is the accuracy of the foreground source removal. Here, we investigate the level of accuracy for the calibration and bright source removal algorithms from the reionization data-sets. We also put forward constraints for the design of the cosmic reionization data reduction scheme for the upcoming low frequency arrays such as, MWA, PAPER, etc. We show that the efficient foreground source removal strategies can only tolerate a frequency independent antenna based mean residual calibration error of 0.2% in amplitude or 0.2 degrees in phase. In order to extract the spherically averaged HI signal power spectrum, bright foregrounds need to be removed with calibration accuracies of 0.05% in amplitude. We also demonstrate the advantages of probing the cosmic reionization with the two dimensional HI power spectrum.