RF Antenna Research Articles

Dynamic frequency analysis of stress–strain-dependent reversibly deformable broadband RF antenna over unevenly made elastomeric substrate

This paper presents the design and development of stretchable and deformable broadband antenna using low-cost silicone rubber-based dielectric substrate. A slot is introduced in the substrate to improve the stretchable behaviour. The dielectric properties of the substrate are measured using suspended ring resonator method. The proposed antenna uses silver elastomeric Lycra fabric as the conductive medium. The resistivity of the conducting Ag fabric is 1 $$\Omega $$ per sq. mm. The conducting patch and ground plane are attached with the substrate using silicone-based adhesive. The fabricated antenna is tested for its resonant characteristics using the vector network analyser.

RF ANTENNA DESIGN FOR BUTTON-TYPE BEAM POSITION MONITORS USING BIO-INSPIRED OPTIMIZATION METHODS

Accelerator based facilities are in a leading position for crafting many scientific and technical innovations for a wide range of application from aviation to medicine. Beam Position Monitors (BPMs) are critical diagnostics tools for such facilities. This study presents bio-inspired methods known as Particle Swarm Optimization and Evolutionary Algorithms in order to design RF antennas for button-type BPMs. Our results show that the antenna parameters obtained using this multiple objective approaches present suitable SNR and linearity values for signal processing. It is found that using an antenna radius of 5.5 mm and beam-pipe radius of 17.5 mm, we can obtain SNR values around 40 dB which can be electronically processed.

Angular reconstruction of high energy air showers using the radio signal spectrum

The Hellenic Open University extensive air shower array (also known as Astroneu array) is a small scale hybrid detection system operating in an area with high levels of electromagnetic noise from anthropogenic activity. In the present study we report the latest results of the data analysis concerning the estimation of the shower direction using the spectrum of the RF system. In a recent layout of the array, 4 RF antennas were operating receiving a common trigger from an autonomous detection station of 3 particle detectors. The directions estimated with the RF system are in very good agreement with the corresponding estimations using the particle detectors demonstrating that a single antenna has the potential for reconstructing the shower axis angular direction.

Percolation threshold of multiwall carbon nanotube-PVDF composite for electromagnetic wave propagation

Advanced physical properties of conductive polymers fibre composites have attracted the attention of material scientists. Here, we produced a polymer fibre composite with aligned multiwall carbon nanotube (MWCNT) of different weight fractions, ranging from 0.25 wt% to 1.5 wt%. At 1.5 wt% additive, a conductor-non-conductor transition occurs that is percolation threshold. This effect enhances the electrical conductivity of polymer composite from 0.050 S m−1 to 326.250 S m−1. Electrically conductor polymer composite will be highly preferred to fabricate radio frequency antennas, due to their unique physical and mechanical properties. We evaluated the performance of the polymer composite antenna and observed the percolation effect in electromagnetic wave propagation of the composite antenna. Far-field radiation of 1.5 wt% MWCNT-polymer antenna was 0.728 V m−1, whereas the maximum far-field result of the antennas made by lower MWCNT concentrations was 0.102 V m−1. Adopting the mechanical properties of PVDF composite, the composite-based RF antenna can be used in robust environments, such as high pressure high temperature oil reservoirs.

A low cost hybrid detection system of high energy air showers

We report on the design and the expected performance of a low cost hybrid air shower detection system suitable for operation as an autonomous unit in strong electromagnetic noise environments. The system consists of three particle detectors (scintillator modules) and one or more RF antennas. The particle detector units are used to detect air showers and to supply the trigger to the RF Data acquisition electronics. The hardware of the detector as well as the expected performance in detecting and reconstructing the angular direction for the shower axis is presented. Calibration data are used to trim the simulation parameters and to investigate the response to high energy (E > 1015 eV) extensive air showers.

Dedicated 70 MHz RF systems for hyperthermia of challenging tumor locations

AbstractHyperthermia (i.e. heating of tumor tissue to 40–43°C) is used in clinical oncology to enhance the therapeutic effect of chemotherapy and radiotherapy. Many tumor sites are heated either by a single RF or MW antenna positioned on the tumor location, or by a phased array positioned around the patient. Superficial tumors are generally heated with MW antennas (434–2450 MHz) and deep-seated tumors with RF antennas (70–150 MHz). These devices cover the major, more common tumor sites, but more rare locations require more dedicated applicators. We discuss dedicated RF systems aiming for heating semi-deep-seated tumors in the leg, breast, and upper thorax. Clinical results show that adequate heating is possible with these systems, with achieved temperatures in the therapeutic range.

Experimental and theoretical study of bumped characteristics obtained with cylindrical Langmuir probe in magnetized helium plasma

Cylindrical Langmuir probe measurements in a helium plasma were performed and analysed in the presence of a magnetic field. The plasma is generated in the ALINE device, a cylindrical vessel 1 m long and 30 cm in diameter using a direct coupled RF antenna (νRF = 25 MHz). The density and temperature are of the order of 1016 m−3 and 1.5 eV, respectively, for 1.2 Pa helium pressure and 200 W RF power. The axial magnetic field can be set from 0 up to 0.1 T, and the plasma diagnostic is a RF compensated Langmuir probe, which can be tilted with respect to the magnetic field lines. In the presence of a magnetic field, I(V) characteristics look like asymmetrical double probe ones (tanh-shape), which is due to the trapping of charged particles inside a flux tube connected to the probe on one side and to the wall on the other side. At low tilting angle, high magnetic field amplitude, power magnitude and low He pressure, which are the parameters scanned in our study, a bump can appear on the I(V) in the plasma potential range. We then compare different models for deducing plasma parameters from such unusual bumped curves. Finally, using a fluid model, the bump rising on the characteristics can be explained, assuming a density depletion in the flux tube, and emphasizing the role of the perpendicular transport of ions.

A Review of RF Antenna Integrated with Solar Array for Spacecraft Application

A Review of RF Antenna Integrated with Solar Array for Spacecraft Application

Fast and Automatic Control of a Frequency-Tuned Radiofrequency Plasma Source

A frequency-tuned radiofrequency (rf) plasma source is automatically controlled to minimize the rf power reflection and to maintain the constant net rf power corresponding to the forward power minus the reflected power. The experiment is performed with a power amplifier operational for the frequency of 37 - 43 MHz and a compact helicon source consisting of a loop antenna, a solenoid, and an insulator tube. The rf power is supplied to the rf antenna via an impedance matching circuit consisting of only fixed small ceramic capacitors. It is demonstrated that the reflection coefficient of the rf power is minimized within ~10 msec and the net power is successfully maintained at constant.

Developing the First mmWave Fully-Connected Hybrid Beamformer With a Large Antenna Array

Millimeter wave (mmWave) systems with effective beamforming capability play a key role in fulfilling the high data-rate demands of current and future wireless technologies. Hybrid analog-to-digital beamformers have been identified as a cost-effective and energy-efficient solution towards deploying such systems. Most of the existing hybrid beamforming architectures rely on a subconnected phase shifter network with a large number of antennas. Such approaches, however, cannot fully exploit the advantages of large arrays. On the other hand, the current fully-connected beamformers accommodate only a small number of antennas, which substantially limits their beamforming capabilities. In this article, we present a mmWave hybrid beamformer testbed with a fully-connected network of phase shifters and adjustable attenuators and a large number of antenna elements. To our knowledge, this is the first platform that connects two RF inputs from the baseband to a $16\times 8$ antenna array, and it operates at 26 GHz with a 2 GHz bandwidth. It provides a wide scanning range of 60°, and the flexibility to control both the phase and the amplitude of the signals between each of the RF chains and antennas. This beamforming platform can be used in both short and long-range communications with linear equivalent isotropically radiated power (EIRP) variation between 10 dBm and 60 dBm. In this article, we present the design, calibration procedures and evaluations of such a complex system as well as discussions on the critical factors to consider for their practical implementation.

Fast Radix-32 Approximate DFTs for 1024-Beam Digital RF Beamforming

The discrete Fourier transform (DFT) is widely employed for multi-beam digital beamforming. The DFT can be efficiently implemented through the use of fast Fourier transform (FFT) algorithms, thus reducing chip area, power consumption, processing time, and consumption of other hardware resources. This paper proposes three new hybrid DFT 1024-point DFT approximations and their respective fast algorithms. These approximate DFT (ADFT) algorithms have significantly reduced circuit complexity and power consumption compared to traditional FFT approaches while trading off a subtle loss in computational precision which is acceptable for digital beamforming applications in RF antenna implementations. ADFT algorithms have not been introduced for beamforming beyond $N = 32$, but this paper anticipates the need for massively large adaptive arrays for future 5G and 6G systems. Digital CMOS circuit designs for the ADFTs show the resulting improvements in both circuit complexity and power consumption metrics. Simulation results show similar or lower critical path delay with up to 48.5% lower chip area compared to a standard Cooley-Tukey FFT. The time-area and dynamic power metrics are reduced up to 66.0%. The 1024-point ADFT beamformers produce signal-to-noise ratio (SNR) gains between 29.2--30.1 dB, which is a loss of $\le$ 0.9 dB SNR gain compared to exact 1024-point DFT beamformers (worst case) realizable at using an FFT.

Electronic applications of multi-walled carbon nanotubes in polymers: A short review

In today’s nano scale regime, a smart electronic device is attractive and has a primary role for majority of the world’s research community, particularly scientific and engineering community. Quasi one-dimensional carbon materials are an ideal material for flexible and wearable electronic applications. Significant progress has been made in developing electronics using carbon-based polymer composites. The incorporation of micro-materials and carbon nanomaterials in polymer has been attempted since the 1990 s and has shown a number of improved properties. In this review, the performance of the polymer composite with nanophase carbon materials is explored and their applications are discussed. In recent years, a wide range of carbon nanomaterials are used to transmit electrical signals for potential applications such as electronics, chemical sensors, mechanical sensors/actuators, and smart materials. Moreover, we have also discussed carbon-based materials, especially multi-walled carbon nanotubes, that are applied on a substrate using some printing technology for flexible electronics, and the progress of CNT-based RF antenna, textile, electromagnetic and interference shielding, and sensor applications has been reported.

Fully-/Partially-Connected Hybrid Beamforming Architectures for mmWave MU-MIMO

Hybrid digital analog (HDA) beamforming has attracted considerable attention in practical implementation of millimeter wave (mmWave) multiuser multiple-input multiple-output (MU-MIMO) systems due to the low power consumption with respect to its fully digital baseband counterpart. The implementation cost, performance, and power efficiency of HDA beamforming depends on the level of connectivity and reconfigurability of the analog beamforming network. In this paper, we investigate the performance of two typical architectures that can be regarded as extreme cases, namely, the fully-connected (FC) and the one-stream-per-subarray (OSPS) architectures. In the FC architecture each RF antenna port is connected to all antenna elements of the array, while in the OSPS architecture the RF antenna ports are connected to disjoint subarrays. We jointly consider the initial beam acquisition and data communication phases, such that the latter takes place by using the beam direction information obtained by the former. We use the state-of-the-art beam alignment (BA) scheme previously proposed by the authors and consider a family of MU-MIMO precoding schemes well adapted to the beam information extracted from the BA phase. We also evaluate the power efficiency of the two HDA architectures taking into account the power dissipation at different hardware components as well as the power backoff under typical power amplifier constraints. Numerical results show that the two architectures achieve similar sum spectral efficiency, while the OSPS architecture is advantageous with respect to the FC case in terms of hardware complexity and power efficiency, at the sole cost of a slightly longer BA time-to-acquisition due to its reduced beam angle resolution.

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment

Negative ions are characterized in the helicon plasma source resonant antenna ion device (RAID) at the Swiss plasma center by means of cavity ring-down spectroscopy (CRDS) and Langmuir probe (LP)-assisted laser photodetachment. A high density and axially homogeneous plasma column is produced via a RF antenna able to sustain the propagation of helicon waves in a steady state regime. An electron density in plasma at 0.3 Pa and 3 kW of input power is measured in the center of the plasma column by LP and microwave interferometry. The electron temperature profile is peaked on axis reaching and decreasing to 1.5 eV at . Thus, a hot core region forms where molecules are rovibrationally excited (), and a cold edge, where low energy electrons can attach to and produce ions by dissociative attachment. In this work we use LP-assisted laser photodetachment and CRDS diagnostics to measure and radial density profiles and how they depend on source parameters. We show that negative ions are distributed on a shell of 0.06 m radius with a peak value of ∼ in plasma. These results suggest that, although substantial technical development is needed, helicon plasmas could be considered as a possible candidate as sources of negative ions for future NBIs.

Design of a Flexible PET Based Yagi Dipole Antenna

In the proposed paper, a flexible Yagi Dipole Antenna based on PET Substrate is designed for the RF system-on-package (RF SOP) applications. RF antenna as a smart sensor is designed on a Flexible substrate Polyethylene Terephtalate (PET). It is the more popular and universally accepted thermoplastic polymer belonging to the family of the polyester. It is generally employed in textiles, thermoforming packaging along with glass fibers. In the proposed design Coplanar Strip line (CPS) is used as a feeder and the RF antenna is a Yagi dipole Antenna with a single driven element i.e. director, and a single reflecting element i.e. reflector. It is a linearly polarized antenna which means it radiates in a single direction. The antenna is designed at a resonating frequency of 5 GHz with a return loss of -23 dB. Simulations of the flexible PET based Yagi Dipole Antenna is carried out by using CST Studio Suite software for Return loss, Radiation plot with varied curvatures. The results for designed flexible Yagi Dipole Antenna imprinted with a PET substrate for portable wireless electronics are analyzed.

Phase-resolved profiles of electron energy deposition in inductively coupled radio-frequency plasmas driven under confronting divergent magnetic fields

Electron motion in a cylindrical chamber under RF electric field and confronting divergent magnetic fields was simulated to evaluate the phase-resolved profiles of power deposition to electrons in a low-pressure inductively coupled magnetized plasma. There were three primary regions where the power deposition was high; a region near the RF antenna, a region near the sidewall, and a region of the partial resonance. The phase-resolved profiles of the electron energy gain G(t) and azimuthal electron velocity vθ(t) were obtained in every section defined in the chamber, and were fitted by functions with sinusoidal terms. The characteristics of G(t) and vθ(t), e.g. their asymmetry and directionality, particular to the position were discussed by comparisons between different regions with the fitting parameters and their factors, such as the amplitude of electric field, that of the azimuthal velocity, the power factor, and the phase differences from the RF electric field.

Coherent showers in decays of colored resonances

We present a new approach to coherent parton showers in the decays of coloured resonances, based on the notion of "resonance-final" (RF) QCD antennae. A full set of mass- and helicity-dependent $2\to 3$ antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in $2\to N$ hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorisations are different. The consequent radiation patterns respect QCD coherence (at leading colour) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorisation is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the VINCIA antenna-shower plug-in to the PYTHIA 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using POWHEG, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.

Wideband Reconfigurable Antenna With Simple Biasing Circuit and Tri-Polarization Diversity

This letter presents a wideband reconfigurable antenna with tri-polarization diversity. The proposed antenna has several exclusive features including: wide operating bandwidth (BW); removal of biasing wires to avoid their effects on the antenna's RF performance; and simple reconfigurability using only two p-i-n diodes and one switchable voltage. A microstrip patch is chosen as a primary polarization-reconfigurable source of the designed antenna. Next, a metasurface (MS) is employed to accomplish a significantly increased circularly polarized (CP) BW and the realization of linearly polarized (LP) operation. An antenna prototype is fabricated and experimentally tested to authenticate the simulated results. The measurements confirm that the proposed design exhibits wide overlapped BW of 12.4% and broadside gain of better than 5.8 dBi for dual-sense CP and LP states.

Development of Highly Constrained 1 m Ka-Band Mesh Deployable Offset Reflector Antenna for Next Generation CubeSat Radars

The emergence of CubeSats has opened up the possibilities of advanced space missions with lower costs and faster development times. A major factor that limits the functionality of CubeSats is the absence of high-gain antennas (HGAs) that can sustain a high data-rate link for communications or provide the required spatial resolution for remote sensing. In this work, we discuss the development of one of the largest apertures at Ka -band for CubeSats—a 1 m mesh deployable offset reflector antenna, with a stowed volume of 3U ( $10\times 10\times 30 \,\,\text {cm}^{3}$ )—to enable precipitation radars that can achieve the required spatial resolution while meeting the stringent mechanical constraints posed by the small CubeSat volume. We detail the critical aspects of this antenna design, including RF characterization, antenna fabrication, and measurement. We also describe a novel deployment mechanism that facilitates the packaging of such a large aperture in a small volume. The antenna demonstrated a measured efficiency of 60%, with a half-power beamwidth of 0.60° at 35.75 GHz. The cost reduction afforded by CubeSats makes launching a constellation of such radar based CubeSats practical, allowing higher temporal sampling rates, which is essential for the observation of weather processes with a short-time evolution.

1604P - Exposure to low energy amplitude modulated radiofrequency electromagnetic fields (EMF) is associated with rapid improvement in quality of life (QoL) status in patients with advanced hepatocellular carcinoma (HCC), using various analyses of EORTC-C30

BackgroundPatient-centered endpoints, overall survival (OS) and QoL (where the benefit is detectable by the patient as an improvement in symptoms or functional capacity), are considered valid “direct” endpoints by the FDA. While EORTC-C30 is an accepted indicator of QoL, there is no accepted standard for time to QoL status improvement, nor any accepted standard of analysis for EORTC-C30 data. MethodsA single-group, open-label, feasibility study was performed to assess QoL status in HCC patients exposed to modulated EMF at patient-specific frequencies. A 120-min outpatient EMF exposure procedure was performed every 30 days until significant QoL deterioration or death. An oral spoon-shaped RF antenna applicator was used to apply EMF while individuals were kept in supine position. EORTC-C30 v3.0 questionnaires were answered by individuals immediately prior to every EMF exposure. The 17 QoL parameters were divided into those measuring improvement (G+ functional scales and global health status/QOL) and those measuring deterioration (G- symptom scales). QoL index was calculated as (mean G+) – (mean G-). Different QoL index calculations were made using three groups of QoL parameters: all 17 QoL parameters, 15 QoL parameters (removing Functional scales and Symptom scales) and 3 QoL parameters (restricted to Functional scales, Symptom scales and Global health status/QOL). A change of +/-5% in QoL index was considered a clinically relevant improvement/deterioration in QoL status. Results42 HCC were exposed to 151 EMF procedures. 4,530 QoL data points were collected for analysis, with 0.1% missing data. QoL index was measured at baseline and 30 days after the baseline exposure procedure. Using the 3 QoL index calculation methods (17 QoL, 15 QoL and 3 QoL) measured 30 days from the baseline exposure, QoL status improved in 63%, 59% and 74% of HCC patients respectively. ConclusionsRapid and significant improvement in QoL status in HCC patients exposed to EMF was detected within 30 days of exposure regardless of the QoL index calculation methods used. Clinical trial identificationNCT 01686412. Editorial acknowledgementLuiz Fernando Reis PhD, Research Director Hospital Sírio Libanês, São Paulo, Brazil, Riad Younes MD and Bertram Wiedenmann PhD MD. Legal entity responsible for the studyHospital Sírio Libanês. FundingHas not received any funding. DisclosureF.P. Costa: Leadership role: Autem Medical. A. Iemma: Honoraria (institution): Autem Medical. F. Soares: Honoraria (institution): Autem Medical. J. Tuszynski: Advisory / Consultancy: Autem Medical. All other authors have declared no conflicts of interest.