Spiral Radiator Research Articles

Optimization of novel flat serial single-phase radiators for spacecraft thermal control

Space thermal radiators play a significant role in the thermal management of spacecraft. With the increase in heat dissipation requirement, the heat pipe radiators are being replaced by mechanically pumped fluid loop radiators. In recent years, authors proved that optimum serpentine serial radiators are advantageous over conventional optimum parallel radiators in terms of the mass and pressure drop. The spiral radiators, inspired by spiral plate heat exchangers, are proposed and analyzed as a replacement for the serpentine serial radiators. Performance analysis of radiators is carried out using conjugate heat transfer analysis. Conjugate heat transfer results are validated with the experimental results obtained from the literature. The performance analysis indicated that the circular spiral radiator performs better than the other two types due to their lower mass and pressure drop. Optimization of radiators is carried out using Taguchi Signal to Noise ratio analysis. Analysis of Variance is conducted to determine the percentage contribution of each variable to the performance of the radiator. When lower pressure drop requirement is prominent, the contribution of the diameter of the tube is 79.3%, whereas the contribution of fin thickness and pitch of the tubes are only 6.1% and 8.2%, respectively. The contribution of the fin thickness is 57.39%, the diameter of the tube is 37.71%, and the pitch of the tubes is 1.89% when the lower mass of the radiator is the prime requirement. The high-performance spiral radiators may find their application in the thermal management of human space flights and high-power GEO satellites.

USE OF MULTILAYER DIELECTRIC FOR SLOT PHASED ARRAY ANTENNAS

It is of interest to study slot spiral radiators as part of a phased array with structural elements in the form of multi-layer dielectrics that make up a multilayer substrate and a spiral cover, which, by changing the parameters of a multilayer dielectric, can significantly change the frequency properties of the radiator and its overall dimensions. The purpose of the work is to develop a mathematical model for a phased array in the form of a periodic structure with slotted spiral radiators using multilayer dielectrics in the design, and its numerical analysis with the study of its frequency properties when choosing the topology of the spiral, the parameters of the dielectric layered medium, followed by determining the design dimensions of the spiral as an element of the phased antenna arrays. A mathematical model of a phased array is presented in the form of a periodic structure with slotted radiators using multi-layer dielectrics in the design. The method is based on the conversion of the electrodynamic problem of excitation to an integral equation with its subsequent transformation to a one-dimensional Fredholm integral equation of the first kind. The directional and polarization characteristics of the phased antenna arrays element are determined, and a numerical analysis of its frequency properties is carried out.

Multilayer Archimedean spiral antenna design for dual-band intra-arm implantable biotelemetric smart health care monitoring system covering MICS and ISM bands

Abstract In this paper, a novel multilayer microstrip implant antenna (MIA) design based on the Archimedean spiral (AS) radiator element is presented for dual-band biotelemetric health care monitoring system. The proposed AS-MIA design has a layered structure consists of the spiral antenna elements and superstrate, namely layer #1 , layer #2 and layer #3 , respectively. While achieving the dual-band multi-layer implantable antenna design, firstly, each of the radiating elements in the respective layers is designed to cover separately in the desired bands, that is, layer#1 and layer#2 operate in the ISM (Industrial, Scientific, and Medical 2.4–2.48 GHz) and MICS (Medical Implant Communication Services 402–405 MHz) bands, respectively. Subsequently the ultimate multilayered AS-MIA design is formed by combining the individually designed layers. The compact implantable antenna has a dimension of r = 5 mm radius and h = 3.81 mm height, owning the electrically size of 0.067 λ 0 and h = 0.051 λ 0, respectively, where λ 0 is free space wavelength at 402 MHz in MICS band. Since the AS-MIA is intended to be used in an intra-arm smart health system, the simulated radiation performances of the antenna in a created numerical arm phantom are presented in the article. Also note that numerical analysis of the implant antenna was carried out using CST MW studio simulator based on finite integral method. The prototype of the implantable antenna was fabricated using Rogers 3210 substrate with electrical permittivity of ε r = 10.2. In-vitro return loss measurements were realized in skin mimicking gels, suggested in the literature. It was observed that in vitro measurement and simulation results were quite compatible with each other, except for some discrepancies due to the manufacturing and material tolerances during the preparation of the prototype antenna and skin mimicking gels. The proposed AS-MIA offers a dual-band operation with 15 and 16% S 11 bandwidth at each band of 402 MHz and 2.4 GHz respectively where |S 11| ≤ 10 dB criterion along with 50-Ω system is considered. Also the proposed design can be a good candidate to be used in dual-band medical implant communication systems with its miniature size and reasonable radiation characteristics.

A Millimeter-Wave Wideband Circularly Polarized Planar Spiral Antenna Array with Unequal Amplitude Feeding Network

A 2 × 2 wideband circularly polarized (CP) antenna array operating at millimeter wave (mmWave) band is presented. The array element is a wideband CP Archimedean spiral radiator with special-shaped ring slot. The elements are fed by an unequal amplitude (UA) feeding network based on a microstrip line (MSL) power divider. The side lobe level is improved by this UA feeding network. In addition, a cross slot is employed to isolate the elements for decoupling. A prototype is fabricated, and the measured results show that the proposed array achieves an impedance bandwidth (IBW) of 6.31 GHz (22.5% referring to 28 GHz) and an axial ratio bandwidth (ARBW) of 7.32 GHz (26.1% referring to 28 GHz). The peak gain of the proposed array is 11.3 dBic, and the gain is greater than 9.3 dBic within the whole desired band (from 25 GHz to 31 GHz). The proposed array consists of only one substrate layer and can be built by the conventional printed circuit board technology. Attributed to the characteristics of wide bandwidth, simple structure, low profile, and low cost, the proposed antenna array has a great potential in mmWave wireless communications.

A Compact Triple-Band Antenna With a Broadside Radiation Characteristic for Head-Implantable Wireless Communications

This letter presents a compact triple-band antenna composed of a spiral radiator with an open-ended slot at the ground for human head-implantable wireless communications. It operates simultaneously at a Medical Implant Communications Service (MICS) band (402-405 MHz), a Wireless Medical Telemetry Service (WMTS) band (1427-1432 MHz), and an Industrial, Scientific, and Medical (ISM) band (2400-2480 MHz). The proposed antenna has a thin profile of 0.5 mm with a volume of 197 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Semisolid phantoms are used for the design and experimental validation, and detailed parameter studies are carried out to determine the working principles of the antenna. Based on simulations and measurements, it was found that the proposed antenna covers all the desired frequency bands with comparably high boresight gains given its compact dimensions.

Modelling of Automobile Radiator by Varying Structure and Materials

Radiators used in the automotive application are a class of heat exchangers whose main purpose is to cool the coolant coming from the internal combustion engines. These coolants flow through tubes covered with fins that facilitate a faster way of heat transfer to the surrounding more efficiently. With the increase in efficiency of the engine cooling system it directly helps in the longevity of the engine in other words, the life of the internal combustion engine increases multifold times. Upon investigating we found different shapes that can be used to optimize the radiators efficiency. There are several other ways to improve the efficiency of a radiator. And these can be achieved by improving the surface area of the radiator, improving airflow through it, improving coolant property which flows through these tubes covered with fin all around and at last using alternate materials that prove to be more efficient than the present ones that are being used. The demand of the current times of climate change and energy crisis have paved way for improved heat transfer rates and designing radiators in smaller dimensions and sizes at the same time being more efficient than the previous generation of radiators. With the above conditions in mind, it has been found out that with a simple modification of changing the existing rectangular-shaped radiators into spiral-shaped ones thereby improving efficiency to improved levels, which finds its use in the current generation of vehicles which are benefitting from the improved rate of heat transfer taking place. The spiral radiator of copper tube used here is wound in two coils connected centrally. Spiral tubes of the radiator have circumferential fins. In this type of configuration, heat transfer rate will increase because of having a circumferential fin across the length of the spiral tube through which water flows. These design considerations have been done keeping in mind the major aims to achieve for this type of design and they are improving heat transfer rate and achieving compactness of shape of radiator. We also did Computational Fluid Dynamics or CFD Analysis to test the material properties for the application of heat transfer and how it fares against old materials.

A Low-Profile Broadband Circularly Polarized mmWave Antenna With Special-Shaped Ring Slot

A single-feed broadband circularly polarized microstrip antenna operating in millimeter-wave band is proposed. An Archimedean spiral radiator is used to realize circular polarization. By adding a special-shaped ring-slot structure with two stubs connecting the inner patch to the outer ground, the radiating direction, bandwidth, and axial ratio (AR) of the proposed antenna can be significantly improved. The antenna prototype is fabricated, and its performance is evaluated. Measured results show that its impedance bandwidth is 13 GHz from 21.1 to 34.1 GHz (46.43% referring to 28 GHz). The axial-ratio bandwidth is 8.35 GHz from 23.85 to 32.2 GHz (29.82% referring to 28 GHz). The gain at 28 GHz is 6.49 dBi.

Parallel fabrication of spiral surface structures by interference pattern of circularly polarized beams

Mass migration of photo-isomeric azo-polymers occurs according to the light intensity gradient, and the morphological surface structure can be fabricated by the artificial distribution of light by applying the interference properties of coherent laser light. Recently, the optical radiation force has played an important role in the morphology for dielectric targets, and chiral structures have been fabricated according to the spirally gathering force distribution that arises due to the electric susceptibility. On the contrary, interference laser processing has been applied to process the surface or interior of the material, and nano- or micro-structures in the lattice have been fabricated in a single exposure to the interference pattern. The unit structures are mostly axisymmetric nanowhiskers, nanodrops and nanobumps, among others. In this experiment, interference laser processing of an azo-polymer dielectric target using a circularly polarised continuous-wave (CW) laser was examined, and a spiral structure was successfully fabricated. From the viewpoint of laser processing method, an optical spiral radiation force was introduced in interference laser processing for the first time.

Atmospheric Pressure Plasma-Mediated Synthesis of Platinum Nanoparticles Stabilized by Poly(vinylpyrrolidone) with Application in Heat Management Systems for Internal Combustion Chambers.

Poly(vinylpyrrolidone)-stabilized Pt nanoparticles (PVP-PtNPs) were produced in a continuous-flow reaction-discharge system by application of direct current atmospheric pressure glow discharge (dc-APGD) operated between the surface of a flowing liquid anode (FLA) and a pin-type tungsten cathode. Synthesized PVP-PtNPs exhibited absorption across the entire UV/Vis region. The morphology and elemental composition of PVP-PtNPs were determined with transmission electron microscopy (TEM) and energy dispersive X-ray scattering (EDX), respectively. As assessed by TEM, PVP-PtNPs were approximately spherical in shape, with an average size of 2.9 ± 0.6 nm. EDX proved the presence of Pt, C, and O. Dynamic light scattering (DLS) and attenuated total reflectance Fourier transform-infrared spectroscopy (ATR FT-IR) confirmed PtNPs functionalization with PVP. As determined by DLS, the average size of PtNPs stabilized by PVP was 111.4 ± 22.6 nm. A fluid containing resultant PVP-PtNPs was used as a heat conductive layer for a spiral radiator managing heat generated by a simulated internal combustion chamber. As compared to water, the use of PVP-PtNPs enhanced efficiency of the system, increasing the rate of heat transfer by 80% and 30% during heating and cooling, respectively.

A broadband circularly polarized cavity-backed Archimedean spiral array antenna for C-band applications

In this letter, a new configuration of sequentially rotated circularly polarized (CP) array antenna with a modified gain is investigated. In order to realize the presented antenna, four Archimedean spiral radiators are applied on a substrate, backed by a circularly slotted ground plane. Also a combination of 180° rat-race coupler and 90° branch-line couplers prepare the employed feeding network in this study. Furthermore, cavity-backed structure is utilized to enhance the antenna gain and achieve a directional radiation pattern over the operating frequency band. This configuration also extends the return loss (RL) and the axial ratio (AR) bandwidths, simultaneously. According to the experimental results, the 2×2 CP array antenna has RL bandwidth of 64.28%, AR bandwidth of 54.28%, and peak gain of 10.84dBic. The close correspondence between the measured and the simulated results validates the proposed design.

Electrodynamic analysis of helical radiators located on an elliptical surface

On the basis of integral representations of the electromagnetic field, mathematical models of the spiral radiators located on the surface of an ellipsoid are constructed. The internal electrodynamic problem is reduced to the set of linear algebraic equations written with respect to unknown values of current on radiating elements. In the band of normalized frequencies, the input resistance of antennas and the distribution of currents over the branches of spirals are calculated. Analysis of the frequency dependences of the input resistance makes it possible to reveal the phenomena of the parallel and serial macroresonance caused by the shape of the surface containing branches of spirals.

Compact Spiral Element for Wideband Beam-Steering Arrays

In this letter, a compact spiral element is proposed for wideband beam-steering arrays. The extremely limited element spacing and size to prevent the occurrence of grating lobes at high frequency range are the most critical issues in designing wideband phased arrays. Two miniaturization techniques are simultaneously applied to an Archimedean spiral radiator to reduce the area of the proposed spiral. This spiral radiator is designed with a reflector plane instead of an absorber and cavity to realize low-profile characteristics and achieve unidirectional pattern without power loss. A wideband balun that operates simultaneously as a wideband impedance transformer is also miniaturized to be integrated between the radiator and reflector plane. The proposed element consists of these three components, and its size is 0.25 λ $_{L}$ × 0.25 λ $_{L}$ × 0.13 λ $_{L}$ , where λ $_{L}$ is the wavelength at 2 GHz, the lowest frequency of interest. This compact spiral element with a simple structure and design procedure can achieve wideband beam steering without grating lobes and be employed in numerous applications, such as conformal arrays.

Radiation of Logarithmic Spiral Antennas in the Presence of Dense Dielectric Lenses

In this paper, the performance of logarithmic spiral antennas as feeds of dense dielectric lens are investigated in detail. The performances are evaluated in terms of clean symmetric radiation patterns, high polarization purity, antenna efficiency, and radiation dispersivity. A logarithmic spiral antenna placed in the dielectric-air interface can provide high aperture efficiencies over large bandwidths if coupled to a synthesized elliptical lens. The use of an air gap increases the directivity of the spiral radiation inside the dielectric allowing for lens directive patterns without sidelobes and reducing the dispersivity of the radiated pulse. The directivity enhancement of the fields inside the dielectric is validated by the measurement of a prototype. The highest frequency at which these antennas can be fed by a planar microstrip line is limited by the thickness of the microstrip substrate.

Magnetic Nanoparticle-Assisted Microwave Hyperthermia Using an Active Integrated Heat Applicator

Magnetic nanoparticle (MNP)-assisted microwave hyperthermia using an active integrated heat applicator is presented in this paper. The effect of MNPs on microwave hyperthermia has been analyzed by coupled electromagnetic–thermal analysis considering the frequency- and temperature-dependent properties of biological tissues. For enhanced heating efficiency and material sensitivity, the optimum microwave frequency for hyperthermia has been identified using the presented analysis and confirmed with experiments. In order to demonstrate MNP-assisted hyperthermia, an active integrated applicator is developed. A microwave signal generation module, which has a voltage-controlled oscillator and a power amplifier, has been fabricated in monolithic microwave integrated circuits and integrated on the microwave heat applicator based on a spiral radiator. A dual-channel logarithmic power detector and a directional coupler have been also employed to monitor power levels during hyperthermia, which allows understanding of the heating mechanism. In vitro heating experiments on phantoms, pork muscles, and tumors with and without MNPs show a large difference in temperature rises, which demonstrates the effectiveness of MNPs for low-power and material-specific hyperthermia. Combined with MNP targeting on the cancer cells, MNP-assisted microwave hyperthermia can be a promising method for a low-power and cancer-specific treatment with minimal collateral damage.

Gravitational Lensing of Spiral Vortex Solar Radiation by Venus

Instrumental observations of the Venus transit on June 6, 2012 were performed using two similar torsinds—a special kind of ultralight torsion balances on a silk suspension. A clear response of both devices to this phenomenon was registered. The observations have verified a theoretical assumption on existence of the Spiral Vortex Solar Radiation (SVSR). The direct measurements of a space velocity of the SVSR determined on the track Venus-Earth, gave a value of 1990 km/s which coincided almost exactly with the previously theoretical calculations. Given the insensitivity of the torsind to gravitational and electromagnetic influences a hypothesis is suggested that the observation manifests a new fundamental interaction.

Heat Transfer Studies on Air Cooled Spiral Radiator with Circumferential Fins

Heat exchangers find use in several applications such as in automobiles, refrigeration, air conditioning, and water treatment plants. Radiators are a class of heat exchangers in which heat transfer occurs by means of air flowing across a series of finned tubes, eventually decreasing the temperature of the fluid to be cooled. The energy crises of recent times have necessitated improved heat transfer rates and at the same time the need for making heat exchangers smaller and more energy efficient. A simple modification has been carried out in the existing configuration of radiators, with a view to improve its efficiency and has resulted in the development of a compact spiral radiator against a standard air cooled fin and tube radiators used commonly especially in automobiles. In this configuration, water flows through spiral tubes, which are fitted with circumferential fins and air flows across the tubes for bringing about heat transfer.A numerical investigation has been carried out on the spiral radiator to study flow characteristics and thermal performance by means of local element by element analysis utilizing ɛ-NTU method. Experiments were performed and the results after comparison with the theoretical values were found to be promising. From the experimental data, a correlation among the important dimensionless numbers has been obtained using GARCH tool.

On the Constant Input Impedance of the Archimedean Spiral Antenna in Free-Space

This communication examines the relationship of metal width and arm spacing of a planar printed spiral antenna on its constant input impedance. Observations on the current and electric field distribution are made first to establish the physical mechanisms responsible for the impedance behavior. An analytical model is proposed to analyze the excited mode on the spiral antenna, which can be used to analytically obtain the constant input impedance in the spiral's radiation region. The expression in this work can be applied to evaluate the input impedance for a variety of non-self-complementary spiral structures.

Characterization, Design and Optimization of Low-Profile Cavities for UWB Spiral Antennas

In this paper, we present a methodology for developing very low profile, hybrid, cavity-backed UWB spiral antennas from a precision electromagnetic material characterization standpoint. Using our method, we have accurately characterized, designed and optimized the dimensions of a 2-18GHz, cavity-backed Archimedean spiral antenna. The si- mulation and measurement results show that the antenna demonstrates excellent axial ratio and gain-bandwidth perfor- mance while maintaining an absorptive cavity depth of only 0.625 inches. The procedure can be extended to the design and optimization of any low-profile spiral radiator required to operate over extremely broad frequencies.

Analytical Development of the Far-Zone Radiation Integral for an Arbitrary Planar Spiral Antenna

The planar spiral antenna's radiation integral is both conceptually and computationally complex. In the past, the far-field pattern has been found by either approximating the spiral's shape to make the computation tractable, or by using a numerical approximation. In this paper, the radiation integral for an arbitrary planar spiral antenna is now derived without approximating its shape, using a readily understandable differential-geometry analysis. This allows for physical insight into the radiation mechanisms and contributions from the various current components that are otherwise intractable using modern computational codes, and provides a significantly more efficient algorithm in cases when mutual coupling can be neglected. In addition, this analysis and physical insight leads to an effective spiral antenna design tool. Current numerical integration techniques are applied to find the far-zone electric field for an Archimedean spiral antenna using this development. The results are compared with a numerical solution of the electric-field integral-equation formulation to validate the analysis.

Design of a double-layered spiral antenna for radio frequency identification applications

In this study, the authors describe a novel circularly polarised (CP) double-layered spiral antenna (DLSA) consisting of two main spiral radiators printed on a thin substrate, a feed line and a folded ground plane for a ultra-high-frequency (UHF) band radio frequency identification (RFID) reader. The proposed antenna exhibits broad impedance and CP bandwidth characteristics. The fabricated prototype has an axial ratio of less than 3 dB, a return loss of less than –10 dB over an 860–960 MHz range and a gain of 6.7 dB in the operating frequency range. This performance confirms that the proposed antenna is appropriate for commercial RFID use in the UHF band.