Double Loop Antenna Research Articles

RFID Double-Loop Tags with Novel Meandering Lines Design for Health Monitoring Application

In this paper, we propose a design of two compact and miniaturized RFID epidermal tags in the UHF band for health monitoring applications. The two conceptions of meandered double-loop antennas with T-match configuration, namely, a double-loop antenna with meandered line in the horizontal direction and a double-loop antenna with meandered lines in two directions, are placed at very close distance from the human body. The proposed tags are composed of bio-silicone substrate, to protect the human skin from the electromagnetic waves, and a copper conductor loaded by T-match configuration, to suit the complex impedance of the antenna to that of the chip. We have performed numerical simulations of these conceptions of two tags using the HFSS and CST solvers. Our results show two optimal sizes with a high communication performance, good matching features, and a large read range. We placed afterwards these two optimized tags in an elliptical environment to test their flexibility and examine their performance on different parts of the human body.

Type of active impulse noise suppressing method based on double‐loop antennas in very low frequency/ultra‐low frequency coupling communications

Very low frequency/ultra-low frequency coupling communication systems suffer from severe disturbance from non-Gaussian impulsive noises which producing significant long tails. Considering the significant in-band parts of the impulse, traditional noise-suppression methods are not adequate in improving the signal-to-noise ratio (SNR), and the performance of existing dipole–loop double antennas active noise suppression systems are limited to a low level due to the different directionality of the antennas. A new double-loop antennas active noise suppressing system was proposed, in which one multi-turn loop antenna was employed to receive the useful signals, and one single-turn loop was employed as the noise reference antenna. A mathematical morphology processor and a time-switch filter were employed to extract the impulsive noise, and the digital equivalent model of the multi-turn loop antenna was established filtering the extracted impulsive noise to obtain a duplicate transient, which is highly correlated with the transients received from the multi-turn loop antenna. The system SNR was improved by subtracting the transient duplicate from the received signals. Simulations were carried out with Monte Carlo method, showing that the SNR can be improved with the gain of about 18 dB with communication error rate extremely reduced by orders of magnitude. Experiment system was also designed and established to verify the feasibility and efficiency, and a 50 m communication experiment in an industrial environment showed that the error rate can be decreased from 0.2 to 0.06% while employing the proposed noise suppression method.

Human Body Shadowing Effect on Dynamic UWB On-Body Radio Channels

This letter reports the shadowing effects of a human body on dynamic ultrawideband on-body radio links. A vector network analyzer is used to sweep the 3–5-GHz frequency band in an anechoic chamber. The sweep time is set fast enough to fulfill the channel coherence time requirements. This enables the data analysis to be performed in time domain by examining the corresponding channel impulse responses. Five on-body locations are examined: right wrist (RW), left wrist with an antenna on the palm (LWA) or back side of the hand, left arm, and left ankle (LA). Two antenna types are applied: dipole and double loop. The path loss (PL) lies between 35.9 and 85.8 dB depending on the case. The double loop has, on the average, higher PL than the dipole. The LWA–RW and RW–LA links have the lowest and highest PLs, respectively. The amplitudes of the first arriving paths follow the inverse Gaussian distribution. The level crossing rate (LCR) and the average fade duration (AFD) show weaker performance for the double loop antennas compared to the dipoles. In general, the LWA–LA is the poorest link with respect to the LCR and the AFD.

CATEGORIZED UWB ON-BODY RADIO CHANNEL MODELING FOR WBANS

A categorized radio channel modeling for wireless ultra-wideband on-body body area networks is discussed. Measurements in an anechoic chamber at fourteen antenna locations are conducted in a 2{8 GHz band. The dipole and double loop antenna types are used. Six link classes are formed based on the antenna spots on the torso, head or limb. The limb-limb and the head-limb links have the lowest and highest path losses, respectively. The head-limb links have the shortest channel impulse responses (CIRs) and limb-limb links the longest ones. The CIR amplitudes follow the inverse Gaussian distribution. The tap indexes and the total excess delays are modeled with the negative binomial distribution. In most cases, the CIRs decay faster for the dipole. Otherwise no major differences exist between the antennas.

A Low-Profile Unidirectional Printed Antenna for Millimeter-Wave Applications

By combining a printed reflector-backed one-wave-length bowtie antenna and a printed double loop antenna, a new wideband high-gain antenna element is demonstrated. Due to its low-profile structure of ~ 0.05λ0, it is attractive to be used in an array environment. Experimentally, a series of antenna arrays operated at 60 GHz are designed and fabricated. They achieve wide impedance bandwidths covering the 57-64 GHz unlicensed frequency band. Over this band, the measured antenna gains are ranged from 14.5-15.5 dBi, 18.3-20.1 dBi and 22.5-25.2 dBi for 4-element, 14-element and 50-element antenna arrays, respectively. The measured radiation pattern has low cross-polarization level and low back radiation. The proposed low-profile antenna and arrays are low-cost in fabrication as they are simply made on a single-layer printed circuit board.

Times Semi-Passive RFID Tags with Double Loop Antennas Arranged as a Shifted Gate Stability Optimization

In this article, Very Crucial subject discussed in Semi-Passive RFID TAGs system stability. Semi-Passive TAGs with double loop antennas arranged as a shifted gate system stability optimization under delayed electromagnetic interferences. The double loop antenna is employed due to the fact that this antenna consists of two parallel loops; i.e., primary and secondary loops. We define Vi1(t) and Vi2(t) as the voltages in time on double loop antennas. Vi1(t) is the voltage in time on the primary loop and Vi2(t) is the voltage in time on the secondary loop. The index (i) stand for the first gate (i=1) and second gate (i=2). Due to electromagnetic interferences there are different in time delays respect to gate antenna's first and second loop voltages and voltages derivatives. The delayed voltages are Vi1(t-τ1) and Vi2(t-τ2) respectively (τ1≠ τ2) and delayed voltages derivatives are dVi1(t-Δ1)/dt, dVi2(t-Δ2)/dt respectively.

이중 루프의 중첩 빔을 이용한 재구성 빔 조향 안테나

본 논문에서는 이중 루프(double loops)를 이용한 새로운 재구성(reconfigurable) 빔 조향 (beam steering) 안테나를 제안하였다. 이중 루프 안테나는 내부 루프(inner loop)에 의한 동상(in-phase)의 빔과 외부 루프(outer loop)에 의한 이상(out-of-phase)의 빔이 중첩된 빔(superposed beam)을 가진다. 또한, 이중 루프 안테나는 내부 루프와 외부 루프를 연결하는 두 개의 가상 스위치(artificial switch)를 사용하여, 가상 스위치 동작(on/off)에 따라 동일한 안테나에서 서로 다른 세 가지 경우(Case 1, Case 2, Case 3)의 빔 방향(beam direction)을 가진다. 안테나의 동작 주파수는 14.5 GHz이며, Case 1에서의 최대 빔 방향은 <TEX>${\phi}_{max}=0^{\circ}$</TEX>, <TEX>${\theta}_{max}=0^{\circ}$</TEX>이고, Case 2와 Case 3에서의 최대 빔 방향은 각각 <TEX>${\phi}_{max}=230^{\circ}$</TEX>, <TEX>${\theta}_{max}=40^{\circ}$</TEX>와 <TEX>${\phi}_{max}=130^{\circ}$</TEX>, <TEX>${\theta}_{max}=40^{\circ}$</TEX>이다. 각 경우의 최대 이득(peak gain)은 6.5 dBi(Case 1), 7.6 dBi(Case 2), 7.8 dBi(Case 3) 값을 가지며, 각각의 반전력 빔 폭(HPBW)은 <TEX>$86{\sim}104^{\circ}$</TEX>이며, 3가지 빔에 의한 전체반전력 빔 폭(HPBW)은 <TEX>$160^{\circ}$</TEX>이다. A novel reconfigurable beam steering antenna using double loops is proposed. The double loop antenna has a superposed beam which is produced by combining the in-phase beam in the inner loop with the out-of-phase beam in the outer loop. Also, the doble loop antenna uses two artificial switches to connect between inner loop and outer loop, and has the beam directions of three separate cases(Case 1, Case 2, Case 3) by changing ON/OFF states of switches. The operation frequency of the antenna is 14.5 GHz, and three maximum beam directions of the antenna are <TEX>${\phi}_{max}=0^{\circ}$</TEX>, <TEX>${\theta}_{max}=0^{\circ}$</TEX>(Case 1), <TEX>${\phi}_{max}=230^{\circ}$</TEX>, <TEX>${\theta}_{max}=40^{\circ}$</TEX>(Case 2) and <TEX>${\phi}_{max}=130^{\circ}$</TEX>, <TEX>${\theta}_{max}=40^{\circ}$</TEX> (Case 3). The peak gains of each case are 6.5 dBi(Case 1), 7.6 dBi(Case 2) and 7.8 dBi(Case 3). The half power beam width(HPBW) of each case is <TEX>$86{\sim}104^{\circ}$</TEX>, and the overall HPBW is <TEX>$160^{\circ}$</TEX>.

Small Wideband Double-Loop Antennas Using Lumped Inductors and Coupling Capacitors

Miniature footprint double-loop antennas, loaded with lumped inductors and coupling capacitors, are introduced. Through band diagram analysis, it is shown that frequency separation between the two radiating modes can be controlled to achieve wider bandwidth. For verification, three wideband antennas are designed by adjusting the inductive and capacitive loadings to create resonances at two closely spaced frequencies around 2.45 GHz. The first antenna is fabricated on a 125-mil-thick Rogers TMM10i substrate and has 2.1% |S11| ;1.2 dB gain using a λ0/9.8 × λ0/9.8 × λ0/39.4 footprint. It is shown that the antenna has 49% smaller footprint area than a standard patch and exhibits the same bandwidth performance at the expense of lower gain. The second antenna is fabricated on a reduced-size substrate comparable to its footprint size. This antenna still exhibits the same bandwidth performance as the standard patch. The third antenna is on a 250-mil-thick substrate and exhibits 14.7% bandwidth and 4.34 dB gain with λ0/9.8 × λ0/9.8 × λ0/19.7 footprint.

Intensity of electric field radiating from high-power pulsed electromagnetic wave generator for use in biological applications

Cancer treatment is one of several new applications which use nanosecond and subnanosecond high-voltage pulses. This study focuses on the design of a compact highpower pulsed electromagnetic wave generator using a nanosecond pulsed power generator to apply a high-intensity electric field for the treatment of cancer; the pulses cause apoptosis in cancer cells. We applied an L-C inversion circuit to the pulsed power generator to obtain a voltage waveform with a single frequency, which is applied to an antenna. A water gap switch and water capacitors were used in the L-C inversion circuit to obtain a pulsed voltage with a frequency element of 250 MHz. In this experiment, an electromagnetic wave was radiated underwater by a loop antenna. A measuring double loop antenna placed 0.15 m and 0.3 m from the radiating antenna detected electric field intensities of 112 kV/m and 49 kV/m, respectively. A focusing bowl was attached to the radiating antenna to obtain a higher electric field. The electric field intensity of the radiating antenna with the focusing bowl, 300 kV/m, was 6 times higher than that without the focusing bowl. The intensity distribution of the electric field focused by the focusing bowl was measured. A measuring small loop antenna detected peak electric field intensity of 11.3 kV/cm at a focal point. Areas with electric field intensity greater than 10.8 kV/cm were approximately 5 mm square and 3 mm wide in the x-z plane and y-axis, respectively.

Ion Cyclotron Resonance Heating System on EAST

Ion cyclotron resonance heating (ICRH) system which will provide at least than 10 MW heating power, with a frequency range from 25 MHz to 100 MHz, is being built up for the EAST. The system includes high-power and wide-frequency radio amplifier, transmission line as well as resonant double loop (RDL) antenna. As a part of this system a sub-ICRH system unit with a ultimate output power of 2.5 MW was set up and employed for heating experiment. The maximum of the launched power reached 200 kW in 2008.

On the detection of RF breakdowns in ICRH Resonant Double Loop antennas

A voltage breakdown in an ion cyclotron resonance heating (ICRH) system is usually detected as an abrupt change in the module of the reflection coefficient | Γ in| at the power source output. The same effect can be due to a large load variation. This paper presents the study of some new concept for detecting voltage breakdowns in ICRH Resonant Double Loop (RDL) systems, to be used in conjunction with the one identifying an arc by the detection of an excessive standing wave ratio (SWR), either at the operating frequency or within the band below the operating frequency. The method should be able to help discriminating fast load variations from voltage breakdowns in any of the in-vessel components under the torus vacuum, and therefore selecting the proper corrective action.

Double-loop antenna for wireless tyre pressure monitoring

The design of a double-loop antenna operating at two distinct frequencies is presented for wireless tyre pressure monitoring systems. The radiation properties of the printed antenna, placed inside the wheel and with the tyre rubber, are discussed as well as the performance in terms of gain and power handling.

A Double Square Loop Antenna with 45° Step Beam Steering

A novel form of Double Square Loop (DSL) antenna for beam adaptive applications is presented and analysed. The double square loop antenna consists of two identical square loops with a common centre placed at 45° to each other. The antenna is fed either at the eight external corners or at the eight mid-points of the inner track, which when excited one at a time steer the beam through 360° in steps of 45°. Also, the antenna can operate in four separate frequencies in UWB region with at least 500 MHz bandwidth, thus offering wideband multichannel operation which is useful to several communication standards.

A Double Square Loop Antenna with Modified Minkowski Fractal Geometry for Multiband Operation

A double square loop antenna with fractal geometry that supports for multiband operation is proposed. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal loop antenna to operate at the first and second resonant frequencies, is inserted at each center side of a big square loop antenna. It also has a small square loop to operate at the third resonant frequency. The proposed antenna is implemented and shown to effectively support the global system for mobile communication (880-960 MHz), digital communication system (1710-1880MHz), personal communication system (1850-1990 MHz), universal mobile telecommunication system (1920-2170 MHz), and wireless local area network (2400-2483 MHz) bands. The radiation patterns of the proposed antenna are still similar to a bidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.

Analysis of the Tore Supra ICRF antenna with TOPICA

The Tore Supra (CEA) antenna for the ion cyclotron range of frequencies (ICRF) is a so-called resonant double loop antenna with internal matching capacitors. The required capacitance range is crucial for antenna and the tuning-and-matching network design. The capacitance value for a given discharge is also important for antenna operation. We discuss a method to accurately predict the tuning capacitance values in the presence of plasma operation and for efficiently accounting for the capacitors in the performance analysis. The presented method relies on the use of the TOPICA code, a numerical suite developed for prediction and analysis of modern ICRF antenna systems; it is able to handle antennas with a realistic 3D geometry and an accurate 1D plasma model. Very good agreement with the experimental capacitance values is found using TOPICA, providing further experimental validation of the computational algorithm and physics model.

Development of a strong field helicon plasma source

We developed a high-density helicon plasma source with a very strong field of up to 10kG. Using a double-loop antenna wound around a quartz tube, 9.5cm in inner diameter and 90cm in axial length, initial plasmas with a high density more than 1013cm−3 were successfully produced with a radio frequency power less than a few kilowatts, and with changing magnetic fields, fill pressures, and gas species.

First results of the Tore Supra ITER like ICRF antenna prototype

The project of an ITER-like (IL) ion cyclotron (IC) prototype antenna was initiated in mid 2002 in Cadarache, to assess the operational characteristics of the IL scheme in a Tore Supra (TS)-sized array. The prototype was developed by modifying an existing Tore Supra resonant double loop (RDL) antenna. This strategy, chosen to reduce cost and manufacturing time, allowed the completion of the array construction at the end of 2003. The array was installed on TS in January 2004, at the beginning of the new experimental campaign. After a few comments on the design, the paper reports results on low-power characterisation, high-power commissioning and preliminary tests on TS plasmas, prior to the array dis-assembly for inspection.

Tore supra ICRH antenna prototype for next step devices

ITER-like IC antennas, fulfilling or possibly exceeding ITER requirements and designed for long pulse operation (1000 s) are currently being developed at Cadarache. As part of these developments, a project of an IC antenna prototype obtained by modifying a tore supra (TS) resonant double loop (RDL) antenna is proposed, to assess in real working conditions the performance of this scheme. After a brief comparison between the new RF circuit version and the conventional RDL circuit, which has been tested in TS for 10 years, the paper focuses on the design and manufacturing aspects of the prototype.

Double‐loop antennas for a circularly polarized tilted beam

AbstractAn antenna consisting of two concentric loops is analyzed using the method of moments. The antenna radiates a circularly polarized (CP) beam tilted from the direction normal to the antenna plane (the axial direction). First, an antenna with two feeds is analyzed. The configuration parameters are optimized in such a way that the inner and outer loops radiate CP axial and conical beams, respectively. These two radiation beams are then combined to form a CP tilted beam. It is found that the tilt angle is 25°, where the axial ratio and gain are 0.6 and 10 dB, respectively. Next, the phase between the two feeds is varied. Calculations show that the beam azimuth direction varies in a range of 360°. Finally, an antenna with a single feed is analyzed. The antenna shows radiation characteristics comparable to those for the two feeds. Further calculation reveals that a VSWR of 1.0 is obtained for another single feed using electromagnetic coupling. The VSWR remains less than 2 in the frequency bandwidth (of 2.5%) for a 1‐dB gain‐drop criterion. Within this bandwidth, the axial ratio is less than 3 dB. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(12): 12–20, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10132

Tests of the ITER Prototype Ion Cyclotron Antenna

A prototype antenna for the ITER ion cyclotron system, based on a resonant double loop antenna design from the 1998 Engineering Design Activity, has been built and tested. Electrical properties of the antenna were measured and were in agreement with theoretical calculations. Results of high-power experiments in vacuum showed that the antenna could operate at voltages in excess of 60 kV for multisecond pulses. The stub tuning arrangement proposed for use on ITER was demonstrated to work. These results validate the original design concept of the ITER antenna.