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An ultrawideband stacked single-turn spiral antenna with an integrated feeding structure is presented in this communication. The proposed antenna consists of two stacked planar single-turn Archimedean spirals which are wound in orthogonal directions. By connecting these two stacked spirals through two vertical posts, the traveling-wave current path is lengthened and, hence, the operating frequency of Mode 1 is decreased. To reduce the feeding complexity, an integrated tapered microstrip line is used to feed the spiral, which also acts an impedance transformer. It is demonstrated that the proposed antenna can operate across 0.29–5 GHz with |S11| < −10 dB and 0.75–3.64 GHz with axial ratio (AR) < 3 dB. Compared with the single-turn Archimedean spiral with the same radius, the impedance and AR bandwidth of the proposed antenna are enhanced from 5:1 to 17:1 and from 1.6:1 to 4.9:1, respectively, showing that the proposed antenna can be a good candidate for ultrawideband applications.

High-power $V$ -band-to- $G$ -band (50–220 GHz) photonically driven electromagnetic emitters, composed of frequency-independent (FI) antennas and charge-compensated modified unitraveling carrier photodiodes (CC-MUTC PDs), are demonstrated in this article. The designed and fabricated PDs achieve a responsivity of 0.2 A/W and are able to provide up to 12-dBm output power. The impedances of the PD and the FI antennas (the sinuous antenna, the spiral antenna, and the log-periodic antenna) are characterized, showing that different antennas could be selected to provide either highest radiated power or widest bandwidth depending on applications. The measurement results indicate that the integrated emitter with the sinuous antenna and the 8- $\mu \mathrm {m}$ PD achieves a record-high broadside effective isotropic radiated power (EIRP) of 20 dBm with an optical-to-terahertz (THz) power conversion efficiency of 15.7% while maintaining EIRP greater than 0 dBm up through 115 GHz of bandwidth (50–165 GHz). The emitter with the spiral antenna and the 5- $\mu \mathrm {m}$ PD provides a wide 3-dB bandwidth of 34 GHz with a maximum EIRP of 8.8 dBm. These high-power wideband emitters can be used for wireless communications, millimeter-wave (mm-wave) and sub-THz imaging, and radar systems.

Corona discharge is a common phenomenon in power systems. If it occurs in overhead lines, then hidden dangers, such as poor contact between metal fittings of insulators and transmission lines, aging insulators, and strand breakage of lines, exist. These dangers may lead to further serious accidents. So, faults must be detected and removed in time. In this study, a novel miniaturized antenna is designed to detect electromagnetic waves produced by corona discharge in overhead lines. This antenna is called a rectangular spiral antenna with a Hilbert unit. The main structure of this antenna is the rectangular spiral curve, whereas the partial structure is the Hilbert fractal curve. The designed antenna is airborne and can be mounted on an unmanned aerial vehicle for close-range detection. The final size of this antenna is 100 mm $\times100$ mm $\times1.6$ mm, and the weight is 35g. Finally, the performance of the designed antenna is verified using an experiment platform of corona discharge.

This paper presents a conformal spiral antenna that is miniaturized and with dual-resonant for the wireless implantable capsule system. The spiral antenna conforms to a swallowable capsule with a radius of 3 mm and a length of 26 mm without occupying the internal space of the capsule. The compact antenna adopts two spiral arms to extend the effective current path for miniaturization. Biocompatible flexible polyimide was used as the dielectric substrate and capsule shell, achieving conformal properties of the antenna as well as compatibility with human tissue. The antenna has been simulated in different environmental models. The bandwidth of the antenna can reach 39.16 % (1.82 GHz-2.76 GHz) and 12.06 % (5.36 GHz-6.06 GHz) at 2.4 GHz and 5.8 GHz. The maximum gains of −35.2 dBi and −28.1 dBi can be achieved at 2.4 GHz and 5.8 GHz, respectively. In addition, the transmission characteristics of the antenna were experimentally verified in the minced pork and pig intestine. By analyzing the communication link, the communication distance between transceivers at 2.4 GHz and 5.8 GHz can meet 14 m and 5 m. These results show that the proposed antenna is suitable for wireless implantable capsule systems.

A travelling-wave-fed slot spiral antenna with wide axial-ratio (AR) bandwidth and beamwidth for GNSS applications is proposed in this paper. The evolution procedure of the proposed antenna can be classified into three steps. Firstly, 12 identical spiral slots are arranged concentrically in a compact area, and AR roundness in low elevation plane is improved by virtue of good rotational symmetry of slot radiators. Secondly, a two-turn travelling-wave feed line is sequentially coupled to the slots, and wideband response of desired magnitude ratio and phase difference of $E_{\theta }$ and $E_{\varphi }$ is obtained by optimizing the number and growth rate of microstrip turns. Thirdly, by supporting the antenna with a modified metallic cavity, the CP radiation performance in low elevation plane is well improved, and thus a widened AR beamwidth is obtained. Finally, the proposed antenna with satisfactory performance is realized in a diameter of $0.56\lambda _{0}$ and height of $0.12\lambda _{0}$ , where $\lambda _{0}$ is the free-space wavelength at center frequency 1.4 GHz. Measured bandwidth of $|S_{11}|$ fully covers the entire GNSS bands, and the 3-dB AR bandwidth ranges from 1.14 to 1.67 GHz (37.7%). Moreover, the 3-dB AR beamwidth exceeds 140° at 1.4 GHz.

A wideband, monostatic simultaneous transmit and receive cocircularly-polarized spiral antenna with improved isolation is discussed. The topology with four arms is configured such that the opposite pairs of arms are used for transmit (TX) and receive (RX). Focused design for robust fabrication that ensures geometrical symmetry with low component imbalances for applied excitations of the two spirals has led to a strong rejection of the coupled voltages and, therefore, high TX/RX isolation. More than 14 dB higher minimum isolation is achieved, when compared to previous spirals from the same STAR family. To ensure reasonable performance in terms of axial ratio and efficiency over 0.5–2.5 GHz, the antenna is restively terminated, cavity backed, and lens loaded. The fabricated prototype is stout and achieves > 50 dB self-interference cancelation over the bandwidth. The copolarized TX and RX modes have VSWR < 2, axial ratio < 4 dB, and symmetric patterns.

This study describes a light-weight wideband spiral antenna that radiates a unidirectional beam. To realise a light-weight antenna, a one-layer thick high-impedance surface reflector (HISR) for a reference spiral antenna is replaced by a two-layer circular HISR (TL-CirHISR). The TL-CirHISR is made of fan-shaped patches printed on a dielectric substrate. It is revealed that a voltage standing wave ratio (VSWR) of

A low-profile spiral antenna backed by a circular high-impedance surface (HIS) reflector composed of homogeneous (CirHISRhomo) fan-shaped patch elements is investigated. The total antenna height from the bottom of the CirHISRhomo to the spiral antenna is very small: 0.09 wavelength at a lowest design frequency of 3 GHz. It is revealed that the CirHISRhomo contributes to a constant input impedance and a small axial ratio (AR) across the design frequency range of 3–10 GHz (the fractional bandwidth is approximately 108%). For comparison, the AR for the spiral antenna backed by a conventional perfect electric conducting reflector is also presented. The analysis results are verified by the measured results of the fabricated antenna.

In the present scenario in the field of human health service and body worn application, the major concern is to detect the actual cause of the pain in human body. In this paper the design and proper shape of antenna for a particular body part like knee, elbow or any other joints are presented with the optimized characteristics and comparison between spiral and Hilbert antenna so that the proper parameters like temperature, lubrications or any damage can be analysis. And for security service, the concern is for small size and minimum loss. Now these antenna devices transmit the physiological data from the body for health purpose and for security purpose and desired information will be transmitted from the body to the peripheral device. These two antennas are designed at operating/resonant frequency of 500 MHz with main objectives of minimum size, minimum error, less power consumption and proper shape of antenna to fit the body part after calculating the SAR value.

A new low profile broadband directional spiral antenna design on a planar EBG structure is introduced which is suitable for aircraft structural integration. The proposed antenna has the (greater th...

In order to meet the wide-band full-space radio monitoring task, the design of a circular-polarized planar dual-arm composite spiral antenna is presented in this paper. The antenna operation covers the L-band and S-band frequencies ranging from 200 MHz to 6 GHz (relative bandwidth is 187.1%). The equiangular spiral is applied to the beginning of the Archimedean spiral, which reduces the input impedance of the antenna, thereby reducing the length of the cross-section of the feed balun and realizing the miniaturization of antenna. The antenna is designed to be simple in structure and small in size. The diameter of the radiating surface and the length of the section are only 1/5 and 1/50 of the working wavelength. The simulated and measured results show that the antenna has a very good impedance matching (standing wave ratio of less than 2.5), and the antenna has good symmetry, and has good circular polarization and wideband characteristics. Finally, the antenna is applied with an USRP (universal software radio peripheral) to carry out the electromagnetic signal monitoring experiment outdoors. The results show that the designed antenna can receive electromagnetic signals in the 200 MHz - 6 GHz band and can be used for full-space radio monitoring.

The design and implementation of printed helical spiral antenna (PHSA) and helical printed inverted-F antenna (IFA) are presented for unmanned aerial vehicle (UAV) with global positioning system (GPS) $L1$ band (1.57 GHz) and telemetry communication frequency band (2.33 GHz) applications. The proposed antenna is miniaturized by co-winding the radiation elements on the same ceramic rod, surface covering by dielectric sealant, inserting a high permittivity dielectric load into the helical structure, turning and meandering the radiation element of PHSA into a spiral parallelogram structure. The PHSA and helical IFA antenna radiation elements are manufactured by silver pasted on the same hollow ceramic cylinder with a diameter of 12 mm and a height of 24.7 mm. The experimental and simulation results show that the proposed PHSA and IFA can achieve the gain of 0.05dB and 1.97 dB respectively and be suitable for GPS $L1$ band and telemetry communication frequency band (2.33 GHz) applications separately.

This paper investigates a planar single-arm spiral antenna used to measure human brain radiation in the frequency range 3-5 GHz. The investigation is carried out using numerical modeling (finite elements method) by employing ANSYS Electromagnetics Suite 19.2. The model of human brain tissues and the antenna are built in this software. The optimization of antenna parameters is carried out to obtain the best matching and sensing depth. The frequency dependence of the antenna input impedance, reflection coefficient is computed, and the volume distribution of electromagnetic field in the head tissues is obtained. We investigate the influence of the matching layer to the antenna characteristics in the case of the deviation of the electrical parameters of the head tissue top layers. The matching layer is located between the spiral antenna plane and the surface of the head. The additional simulation is carried out by using WIPL-D Pro EM simulator to validate the obtained results. Shabashov E. P., Shabunin S.N., Mrdakovic B. Modeling and analysis of the spiral antenna properties for the research of the brain radiation in the microwave range. Ural Radio Engineering Journal . 2020;4(1):84–99. DOI: 10.15826/urej.2020.4.1.005

This paper presents the antenna characteristics of a spiral antenna backed by a circular high-impedance surface reflector (CirHISR) composed of a fan-shaped patch element. The fan-shaped patch element is arrayed symmetrically. The antenna height between the spiral antenna and the bottom surface of the CirHISR is 0.09 wavelength (9.0 mm) at the lowest operating frequency of 3 GHz. Input impedance and axial ratio are analyzed using FEKO based on the method of moment and compared to that of a spiral antenna with a CirHISR asymmetric array using a fan-shaped patch element. It is found that good antenna characteristics are obtained across a frequency range of 3 GHz to 10 GHz (a fractional bandwidth of 108%). Similar antenna characteristics are also found between the spiral with the CirHISR symmetric patch array and that of the asymmetric one.

In this communication, we propose a frequency and polarization reconfigurable spiral antenna tuned by liquid metal. The antenna has a compact size and wide reconfigurable bandwidth. The dual-layer polymethylmethacrylate (PMMA) microfluidic attached to the dielectric substrate ensures liquid metal flowing. The left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) are achieved by adjusting the distribution of liquid metal in microfluidic channels. Changing the lengths of liquid metal arms realizes frequency reconfiguration. The proposed antenna supports continuously reconfigurable operating frequencies of RHCP from 0.6GHz to 13.5GHz and keeps working from 1.5GHz to 2.5GHz of LHCP.

In this paper, performance enhancement in a shorted polygonal archimedean spiral antenna has been proposed by backing it with a hybrid reflector. In the proposed work, two arms of the polygonal spiral antenna are shorted at an outer octagonal conductive ring aiding in size reduction of the polygonal spiral. The shorted polygonal spiral antenna with the advantages of low profile and the good axial ratio at lowest frequencies of operation is backed by a hybrid reflector that utilizes combination ferrite layer which tapers towards the center to a PEC layer. The hybrid reflector helps to improve the gain of the antenna significantly at low frequencies without compromising the gain of the antenna at high frequencies. The antenna operates from 0.6 GHz to 6.5 GHz with a minimum boresight gain of 0.2 dBic at 0.6 GHz and an average gain of 6 dBic from 2.2 GHz. The antenna also demonstrates a good axial ratio of ≤3 dB over the VSWR bandwidth in a low-profile dimension of 0.13 λ0 × 0.13 λ0 × 0.04 λ0. The proposed work thus presents a novel idea to develop a compact high-performance spiral by shorting the arms of a polygonal spiral with a conductive ring and backing the same by a hybrid reflector and cavity.

Objective: This numerical study was designed to evaluate the feasibility of using an inductive coil for monitoring the changes in the volume of a hematoma in the head in situ and to compare the inductive coil performance to that of a spiral antenna based on the radar principle. Methods: Numerical analysis was used to solve the complete set of Maxwell's equations in full three-dimensional anatomical model of a head and brain with data on clinical occurrence of hematomas from the clinical literature, for frequencies of 100 MHz, 500 MHz, and 1 GHz. Results: 1) The analysis shows that the spiral radar antenna provides a better resolution when the antenna can be placed exactly facing the center of the volume of blood. Under any other circumstance, the inductive coil has a better resolution at both 500 MHz and 1 GHz. 2) The induction coil is more sensitive to rotation artifacts than the spiral antenna. 3) Single frequency measurements do not provide conclusive results. Conclusion: The inductive coil has the ability to monitor small changes in the volume of a hematoma in the head. However, multifrequency measurements are required for correct diagnostic. Significance: This study provides a new, low-cost alternative to the conventional medical imaging for monitoring the hematoma increase.

In this paper, a simulated design of a rectangular spiral antenna is proposed. The antenna is tuned for communication in the ISM band at 2.4GHz. The frequency of choice enables the proposed antenna to be used in a number of IoT based devices using popular wireless networks like Bluetooth and WiFi. The design has been built with FR4 material as the substrate with conductive copper lines, which can be easily fabricated on a PCB. When the coil is used to communicate at 2.374 GHz, the reflection coefficient is −30.5 dB, with a bandwidth of 150.7 MHz for ‖S11‖ ≤ -10 dB, i.e., a fractional bandwidth of 6.53%. The VSWR is obtained to be 1.05 at 2.374 GHz. The radiation efficiency a t 2.4 G Hz is obtained as 38.3%. A thorough comparative study with a traditional coil and the effects of separating the outermost coil on bandwidth, radiation efficiency, ‖S11‖ and VSWR has also been studied. Overall, we see a 70.3% reduction in area when compared with existing works. Our paper also lays out the methodology to tune rectangular spiral antennas to certain frequencies. This research is a 1 of 3 work, with the scope to go towards multi functional coil design capable of Bluetooth Communication, Capacitive touch and Wireless Charging.

In this paper, a composite planar spiral antenna consisting of an eight-arm equiangular spiral antenna and eight Archimedean spiral antennas has been designed to radiate electromagnetic wave carrying tunable angular momenta in a wide band. A tunable eight-way Wilkinson power divider network is used to offer three kinds of feeding modes for the equiangular spiral antenna, and thus the composite antenna can radiate the electromagnetic waves with angular momenta of the modes l=1, 2, and 3, respectively. The Archimedean spiral is introduced to improve the gain of the composite antenna in the case of the angular momentum of l=3. By analyzing axis ratio (AR) of the proposed antenna, the generated angular momentum of l=1 is spin angular momentum (SAM), and the angular momenta of both l=2 and 3 include SAM and orbital angular momentum (OAM). Simulated and measured results are given to demonstrate good performance including tunable modes, good purity and wide band.

Collocating antennas for different purposes on a single communication platform is a big trend as it can improve space efficiency. However, strong interferences happen among the antennas working at different bands due to the close proximity, leading to deteriorated antenna performance. This paper proposes a simple yet effective method to alleviate this issue by developing low-scattering array topology without increasing array size. The proposed method is used on a typical 3G/4G dual-band dual-polarized base station antenna array as an example to illustrate its effectiveness. By relocating the positions of the antennas in such array, the antenna performance can be substantially enhanced. Although this technique cannot eliminate the interferences solely, it can be used as a supplementary with other techniques to achieve optimal performance. At last, the proposed array topology is used together with a low-scattering spiral antenna designed for cross-band scattering mitigation, which leads to an outstanding array performance with a compact size.

To solve the problem of measuring the efficiency of electrically small portable and mobile antennas operating at HF and MF ranges, a calorimetric measurement method is considered. The method is based on the representation of the antenna as a physical system in which electromagnetic radiation is useful, and heat losses are detrimental. Measuring the heat loss of the antenna and its non-radiating equivalent allows you to estimate the efficiency. The description of the developed calorimetric installation for measuring the efficiency is given. Physical and technical features of its work are considered. For testing, a sample of a small-sized spiral antenna was selected, operating at a frequency of 1.9 MHz and matched with a 50 Ohm feedline with VSWR

This paper presents a miniaturized dual-polarized Multiple Input Multiple Output (MIMO) antenna with high isolation. The antenna meets the constraints of sub-6 GHz 5G and the smartphones’ X-band communications. A vertically polarized modified antipodal Vivaldi antenna and a horizontally polarized spiral antenna are designed and integrated, and then their performance is investigated. Three frequency bands of 3.8 GHz, 5.2 GHz, and 8.0 GHz are considered, and the proposed dual-polarized antenna is studied. High isolation of greater than 20 dB is obtained after integration of metamaterial elements, and without applying any other decoupling methods. The proposed triple-band metamaterial-based antenna has 1.6 GHz bandwidth (BW) (2.9 GHz–4.5 GHz), 13.5 dBi gain, and 98% radiation efficiency at 3.8 GHz. At 5.2 GHz it provides 1.2 GHz BW, 9.5 dBi gain, and 96% radiation efficiency. At 8.0 GHz it has 1 GHz BW, 6.75 dBi gain, and 92% radiation efficiency. Four antenna elements (with eight ports) were laid out orthogonally at the four corners of a mobile printed circuit board (PCB) to be utilized as a MIMO antenna for 5G communications. The performance of the MIMO antenna is examined and reported.

Global 21cm experiments aim to measure the sky averaged HI absorption signal from cosmic dawn and the epoch of reionisation. However, antenna chromaticity coupling to bright foregrounds can introduce distortions into the observational data of such experiments. We demonstrate a method for guiding the antenna design of a global experiment through data analysis simulations. This is done by performing simulated observations for a range of inserted 21cm signals, then attempting to identify the signals with a data analysis pipeline. We demonstrate this method on five antennae that were considered as potential designs for the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH); a conical log spiral antenna, an inverted conical sinuous antenna and polygonal-, square- and elliptical-bladed dipoles. We find that the log spiral performs significantly better than the other antennae tested, able to correctly and confidently identify every inserted 21cm signal. In second place is the polygonal dipole antenna, which was only unable to detect signals with both very low amplitudes of 0.05K and low centre frequency of 80MHz. The conical sinuous antenna was found to perform least accurately, only able to detect the highest amplitude 21cm signals, and even then with biases. We also demonstrate that, due to the non-trivial nature of chromatic distortion and the processes of correcting for it, these are not the results that could have been expected superficially from the extent of chromatic variation in each antenna., Comment: 16 pages, 10 figures

Antennas are very required elements in the safety and the security of the nation. During war times it is needed to identify the enemy targets. To obtain the enemies signal frequency and the polarization the defense antennas that are molded on to the airborne vehicles must be are to operating at a wide range of bandwidths with circularly polarized radiation patterns. These CP antennas were suitable at receiving ends for detecting any type of linearly polarized signals that are oriented in any direction. In this paper design and develop a composite spiral antenna covering a frequency range of 0.5−18 GHZ with the dimension of 90mm × 90mm is examined. The spiral antenna is a novel antenna of its kind for microwave direction finding as it exhibits wide frequency band. The Square spiral antenna is the best choice rather than a round spiral since it has reduced aperture. Spiral antenna has some inherent features like ultra wideband bandwidth, circular polarization and flush mounting capability. Hence these Spiral antennas suits as a best choice in direction finding applications. The design of composite spiral circuit is performed by using a computer program generated in MATLAB software. HFSS is a high performance full wave EM field simulator used to analyze the performance of spiral antenna in terms of its input reflection coefficient, Radiation pattern, gain and axial ratio in this paper. After the completion of the antenna design, its various parts are fabricated and assembled with precision. The assembled antenna is tested for various characteristics using network analyzer and anechoic chamber. The investigated outcomes of the tested Spiral antenna are projected in this paper.

A low-profile, ultra-wideband beam steering spiral antenna array with complete coverage of mid-band 5G has been developed for aerospace applications. As 5G frequency bands have been allocated across the globe, the frequencies used by different regions has diverged (e.g. 3.4-3.8 GHz in the EU and 3.3-3.6 GHz & 4.8-5GHz in China). This provides a challenge for intercontinental aerospace communication as aircraft must be able to cover all frequencies. Here, an antenna array solution is presented that covers all the required frequency bands with only a single antenna system. This array consists of miniaturized spiral antenna elements which generates an axial beam from 3.3 GHz to 5 GHz. By placing this antenna in a 16-element array, it allows beam steering in elevation plane from 0 to 40 degrees across the bandwidth. While this is primarily developed for aerospace applications, this work could also provide advantages for ground vehicles and UAVs.

A new absorbing structure based on a planar spiral antenna is designed to deal with multipath propagation in a complex urban environment. Firstly, a multipath propagation model is introduced, and then a specific size metal ring structure is designed for multipath signals, and the final wave-absorbing structure is obtained through improvement and optimization. In this paper, emphasis on the value of the phase and the root mean square error of the antenna received by multipath signals of different angles and frequencies under the absorbing structure. The simulation results verify its effectiveness.

UHF detection method can be effectively applied to online partial discharge monitoring of GIS. But limited to the size of GIS, the UHF antenna needs to be miniaturized to facilitate installation on GIS equipment. This paper designs a miniaturized UHF antenna for partial discharge detection based on the traditional Archimedean spiral antenna after cosine-wave meandered. Simulation and actual test results show that the antenna has ultra-wideband characteristics, good directivity in the working frequency band, and can achieve omnidirectional radiation. At the same time, the antenna voltage standing wave ratio (VSWR)|2 in the 920MHz~3GHz frequency band. The antenna is simple in structure, small in size, 97mm in diameter, and 51mm in section height. The results show that the designed antenna has good performances.

The HI 21cm absorption line is masked by bright foregrounds and systematic distortions that arise due to the chromaticity of the antenna used to make the observation coupling to the spectral inhomogeneity of these foregrounds. We demonstrate that these distortions are sufficient to conceal the 21cm signal when the antenna is not perfectly achromatic and that simple corrections assuming a constant spatial distribution of foreground power are insufficient to overcome them. We then propose a new physics-motivated method of modelling the foregrounds of 21cm experiments in order to fit the chromatic distortions as part of the foregrounds. This is done by generating a simulated sky model across the observing band by dividing the sky into $N$ regions and scaling a base map assuming a distinct uniform spectral index in each region. The resulting sky map can then be convolved with a model of the antenna beam to give a model of foregrounds and chromaticity parameterised by the spectral indices of the $N$ regions. We demonstrate that fitting this model for varying $N$ using a Bayesian nested sampling algorithm and comparing the results using the evidence allows the 21cm signal to be reliably detected in data of a relatively smooth conical log spiral antenna. We also test a much more chromatic conical sinuous antenna and find this model will not produce a reliable signal detection, but in a manner that is easily distinguishable from a true detection., 20 pages, 18 figures

The nearfield antenna with well-distributed field is required in radio frequency identification (RFID) system. In this paper, a nearfield antenna, with planar quadrifilar spiral antenna and feeding network is presented. The proposed antenna exhibits uniform field distribution with maximum variation of 10dB for both E and H fields in simulation, and field difference between inside and outside the range of antenna is 30dB.

A broadband planar circularly polarized antenna based on the differential excitation of an asymmetrical spiral antenna is presented in this paper. The proposed feeding method of the spiral antenna is an appropriate alternative to the complex balun circuits used in conventional spiral antennas. The simulation results show that the CP antenna covers the 46.84 % -15 dB impedance bandwidth and 36.19% 3-dB axial ratio (AR) bandwidth with the peak realized gain of 6.7 dBi. The presented antenna inherits the low profile characteristic and is capable of integration with planar structure.

International audience; 4-arm spiral antennas have a wide bandwidth and circular polarization when operating in mode 1 (fundamental mode). Switching to mode 3 (to obtain opposite circular polarization) dramatically reduces the antenna bandwidth compared to mode 1. In this work we reduce the arm sizes of the spiral (for example with RF switches) to increase the bandwidth of mode 3 at the higher mode 1 frequencies. In this way the antenna has the same wide bandwidth for both polarizations (modes).

Noninvasive determination of biological parameters is a research challenge now a day. A suitable noninvasive technique that measures blood glucose level (BGL) accurately without any side effect is not available till date. This paper presents possibility of measurement of BGL of human being noninvasively using Microwave Sensor. Various microstrip antenna structures like a spiral antenna, ultra-wideband antenna, and narrowband antenna are proposed as microwave sensors, and performance is measured in terms of return loss. Experimentation on each antenna is carried out to check the frequency response of antenna for various BGLs measured using the available invasive technique. BGL and microwave frequency relation is determined using these proposed antennas to a model noninvasive blood glucose meter. A comparative study of antennas is done.

Full-wave finite-element antenna simulations are carried out between 100 and 700 GHz for a planar square spiral antenna, investigating the effect on the antenna gain of resistive losses in the metal arms. It is found that a large degradation of the gain occurs relative to the same antenna with arms of pure gold. However, the degradation is greatest at low frequencies where the skin depth in the lossy metal is significantly greater than the thickness of the metal arms. As the skin depth approaches the thickness of the arms, the lossymetal antenna gain approaches the gold-arm antenna gain asymptotically.

In this paper, a simple Archemedian spiral antenna fed by a 6-section exponential impedance transformer cum parallel-strip to microstrip balun is presented. Antenna and the balun are designed for ultra wide-band (UWB) (1.6-12 GHz) frequency range. Using this antenna, a 17 element array helmet is simulated in 3-5 GHz band, around CST voxel model of human brain with a 1 cm blood-clot introduced in it. A comparison of difference in reflection loss with and without tumor for various antenna positions is carried out.

A rigid air-filled cavity backed UWB spiral antenna for GPR applications is designed, simulated, and measured. The fabricated physically big planar spiral is accurately cut out of a thick aluminum sheet using an abrasive water jet machine. It is fed by a mechanically firm balun feed that avoids the weak interconnection between the spiral and the balun. The antenna operates from 750 MHz – 1.25 GHz and maintains better than 12dB return loss and greater than 6 dB peak gain over the range. The fabricated antenna also keeps an axial ratio of less than 4 dB over the operating frequency range.

Wideband planar antennas with balanced feeds, such as spiral antennas, often require wideband microstrip exponential tapers with intricate printed circuit board interconnects at right angles. A twinaxial feed scheme is proposed for a cavity-backed spiral antenna, which eliminates this need. The overall assembly features an input VSWR of below 2.8:1 across the band of 630 MHz to 2.87 GHz, which is comparable to that of the antenna simulated in isolation with a differential port feed.

The paper presents design, simulation and experimental results for the reconfigurable square spiral antenna. This antenna is reconfigurable for two bands: band-I is 0.4–3 GHz which covers G...

The purpose of this work is to present new technology of acquiring energy from the Ultra-wideband (UWB) station and stored in a super-capacitor to charge any electronic device. Many electronic devices operate in critical conditions where it is costly, inaccessible to replace the battery. Examples include sensors of cardiovascular diseases [1][2], aircraft or structural building tracks, oil, and gas platform [3][4]. The research is developing and design a t-shirt it contains a circuit can harvesting the radiofrequency energy around us from many radio station and store this scavenging power in super-capacitor. The evident system of acquiring RF energy is to design spiral antennas are tuned to scavenge RF energy from the ultra-wideband. The device is installed into the jacket, as shown in Figure 1. This device consists of an antenna connected to a small circuit that can collect the harvested signals for charging many electronic devices. - 2019 IEEE. VII. ACKNOWLEDGMENT This publication was made by NPRP grant # NPRP8-140-2-065 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. Scopus

This paper investigates a planar single-arm spiral antenna used to measure human brain radiation in the frequency range 3-5 GHz. The investigation was carried out using numerical modeling (finite elements method) by employing ANSYS Electromagnetics Suite 19.2. In this software, the model of brain tissues and antenna was built. An optimization of antenna parameters was carried out to obtain the best matching and sensing depth. Frequency dependence of antenna input impedance, reflection coefficient was computed, and also a volume distribution of electromagnetic field in the head tissue was obtained. An influence matching layer to antenna characteristics is investigate in case of deviation of electrical parameters of the head tissue top layers. The matching layer is located between the spiral antenna plane and the surface of the head. To validate the obtained results, an additional simulation was carried out by using another software EM simulator.

In order to meet the requirements of miniaturization, wide frequency band and low-profile antennas for electromagnetic environment monitoring area, we designed a miniaturized Archimedes spiral antenna for USRP electromagnetic signal acquisition system. Antenna is sine-wave meandered based on the traditional Archimedean spiral antenna to reduce the antenna size. After optimizing the structure parameters, the antenna with a radius of 60mm and a thickness of 2mm was fabricated. The measurement results show that: in 400MHz-4.5GHz frequency range, the antenna has good impedance characteristics with VSWR ≤ 2, and has an ultra-wide-band, as well as great directivity and omnidirectional radiation feature. Finally, the antenna was applied to the USRP(Universal Software Radio Peripheral) and an environmental monitoring experiment was conducted. The results show that the antenna can receive electromagnetic signals of 400MHz-4.5GHz, and has potential application in electromagnetic environment monitoring area.

On-board antenna-feeder devices constitute an integral part of spacecrafts both according to the type used and according to the target-oriented task. There is a target-oriented data radio transmission line besides other on-board systems such as telemetry, navigation, intersatellite communications, etc., comprising receiving or transmitting antennas. In this paper presents the construction of on-booard data radio transmission line antenna system of information transmission for big-size spacecrafts “Meteor” series and small-size spacecrafts designed on space-based platform “Canopus-B”. VHF -band, UHF -band, S-band and X-band antennas are used as part of the target-oriented data transmission radio line. The drawbacks of the approach being used for the vehicle-borne radio line construction are shown. Thus, the research work shows the status of the vehicle-borne antenna-feeder devices of the space vehicle target-oriented data radio transmitting line through the example of spacecrafts “Meteor” series and space-based platform “Canopus-B”. The future trends in the further development of the radio line on-board antennas are as well revealed and presented.

An improved meandered spiral antenna with a new semi-fractal reflector is designed and fabricated. It is considered as a unidirectional circular polarised broadband antenna having high gain. To improve the impedance bandwidth, the top layer of the antenna is shaped as equiangular Archimedean lines which its outer area meanders. The reflector consists of many fractal hexagonal shape cells. It is implemented at the back of the spiral antenna in order to improve the gain and circular polarisation. The simulated and measured results indicated that the antenna covers the impedance bandwidth of 446% within the frequency region of 0.8–4.37 GHz having the gain of 7.5–13 dBiC. The antenna is designed to be employed in positioning and short-range sensing systems.

This paper proposed a novel antenna for ultra-high frequency (UHF) radio frequency identification (RFID) near-field applications with uniform distribution of the electric field along the x-axis (Ex), and the y-axis (Ey). The proposed antenna adopted a spiral structure to achieve broadband and multi-polarization. The novel antenna achieved good impedance matching within 860–960 MHz. Using a ground plate, the proposed antenna achieved low far-field gain and a maximum gain of less than −11 dBi. The component of the excited electric field Ex and Ey parallel to the antenna surface was uniformly distributed, and there was no zero point. The proposed antenna achieved a 100% read rate of tags parallel to its surface in the reading area of 150 mm × 150 mm × 220 mm. Simulation results were consistent with the results of real-world measurements, and the proposed antenna was suitable as a reader antenna in near-field applications. The polarization mode of RFID tags is mostly linear polarization, and the placement of tags in practical applications is diversified. Compared with the traditional RFID reader antenna, the proposed antenna achieves uniform electric field distribution parallel to the antenna surface, but the single-direction electric field has zero-reading points, which is easy to cause the misread of tags. The RFID tags can be read more accurately. To verify the scalability of the reading area of the spiral antenna unit, it was used for array design, and simulations were conducted using 1 × 2, 2 × 2, 1 × 4, and 2 × 4 arrays. The component distribution of the electric field excited by the four array antennas in the x and y directions was uniform and the reading area was controllable. Therefore, the proposed spiral antenna has the expandability of the reading area and can meet the needs of different application scenarios by changing the number of array units. With the array extension, the matching network also extends, and the impedance characteristics of the array antenna are somewhat different, but they also meet the application requirements.

A double layer spiral antenna with side length of $740~\mu \text{m}$ was fabricated by a multilayer electroplating process and bonded with an radio frequency identification chip by silver epoxy to form a microsensor chip. A theoretical power transfer model was built to optimize the power transfer efficiency. The resonant frequency of the microsensor was characterized inside a small coupling loop, exhibiting a high degree of agreement with theoretical results. A magnetically coupled communication and charging platform was developed to work with the microsensors. The reader antenna was composed of a coupling loop and a secondary coil with 40-mm diameter wrapped around a polycarbonate tube. To maximize the magnetic field generated inside the secondary coil, a lump circuit model was built and its resonant modes were analyzed. The maximum current inside the secondary coil was achieved at the serial resonant frequency, at which the current followed a sinusoidal distribution along the coil. The magnetic field distribution inside the coil was calculated to analyze the read-out of the reader antenna. The communication and power transfer was demonstrated with the microsensors flowing through the reader antenna by successfully retrieving the sensor ID. [2016-0318]

In era of ever increasing demand of wireless communications, domain of antenna design has progressed rapidly and gained a lot of attention among researchers and academicians. Over past few decades, it has catered the needs of society and technocrats by proving itself as one of the main driving forces behind recent advancements in wireless communication. Especially in the GNSS applications, for civilian and military use, antenna design has played a vital role. Thus, a humble attempt is made in this article to provide a glance of globally used antenna for the GNSS applications. A spiral antenna. Various aspects of antenna characteristics have been described that gives insight of developments carried out in the field of spiral antenna design and important conclusions are drawn from the comparisons made for their future use. Comparative reviews between various aspects of antenna designs reveal the fact about promising performance of spiral based antenna in developing dual/tri band applications for GPS as well as IRNSS.

Increasing mobility, safety and passenger comfort are very strong motivations for implementation of Intelligent Transportation Systems (ITS) in practice. The role of wireless communications in ITS has become compelling, both for industry and research community. Wireless communications technologies provide a platform for the exchange of data among the vehicles. A penta-band printed spiral antenna with tapered feed is proposed for vehicular communication system, facilitating vehicle-to-vehicle (V2V) and infrastructure to vehicle (I2V) communication. The antenna covers the navigational frequencies viz., 1.2, 1.5 GHz and Wireless Communication frequencies viz., 2.45, 3.3 GHz and Dedicated Short Range Communication frequency, 5.8 GHz for vehicular communications. Further, radio link characterization of I2V and V2V propagation channel is carried out using Electromagnetic propagation tool, and compared with empirical path loss models of ITU, two-ray reflection and inter-vehicle models.

Developments in automotive industries are increasing to deliver secured and pleasant journey by exchange of information among the vehicles, inside vehicles, between vehicle and with infrastructure utilizing wireless communication networks (WCN). To meet the requirements for various wireless applications, a new printed planar based circularly polarized penta-band spiral antenna with tapered feed is designed to cover the navigational frequencies viz., 1.2, 1.5 GHz and WCN frequencies viz., 2.4, 3.3 GHz and Dedicated Short Range Communication frequency 5.8 GHz for vehicular mobile communications. A 3D Electromagnetic (EM) tool is used for design and is validated via field measurements with Radio Frequency (RF) equipment. In order to validate the performance of the designed antenna, Received Signal Strength (RSS) experiments were conducted between two vehicles at 2.4 and 5.8 GHz in an open area and on road with a vehicle moving speed of 15 km/h. Further, path loss analysis is done for vehicular environments with line of sight condition are simulated using EM propagation tool and simulated results are compared with empirical model viz., ITU, Two-ray reflection, dual-slope model and COST 231 Walfisch Ikegami model.

A low-profile, dual circularly polarised, and centre-fed four-arm Archimedean spiral antenna with broadside radiation patterns is investigated in this paper. It is shown that both right- and left-hand circular polarisations (CPs) are generated in the four-arm spiral antenna, whose circumference is less than three wavelengths, by properly exciting the spiral arms from their inner ends. Similar analogy can be used to extend the concept to any multi-arm spiral antenna. The proposed compact antenna, which is backed by a planar reflector surface, is designed and extensively investigated to study main antenna specifications including gain, cross polarisation, and pattern symmetry, for dual-polarised wireless communication systems. A 3 dB axial ratio frequency bandwidth of about 1.8-5.3 GHz is realised for both clockwise and counter-clockwise CP with axial beams. Furthermore, superior pattern symmetry with equal beamwidths is attained for both senses of polarisation. A prototype antenna is fabricated and tested. Excellent agreement between the measured and computed results is observed. An asymptotic equation is also developed to estimate the antenna peak gain over the frequency band for both senses of CPs.

A new fractal curve along with its iterative function system based on Koch curve is proposed and used for the miniaturization of Fibonacci spiral antenna (FSA). This curve possesses semicircular sections so as to maintain the symmetry with quarter circular sections of FSA. The modified Koch curve owing to its curvatures facilitates a smoother flow of surface current along the spiral arms fractalized with it, unlike uneven current distribution when fractalized with conventional sharp-cornered Koch curve. The second iterate of this curve has resulted in nearly 50% of size reduction by maintaining an equivalent arm length needed for the operation at lowest frequency. The numerical analysis and measurements confirm the retention of inherent broadband characteristics of the FSA and its miniaturized prototypes in the absence of ground plane with excellent radiation properties.