Elliptical Antenna Research Articles

Numerical analysis of specific absorption rate in the human head due to a 13.56 MHz RFID-based intra-ocular pressure measurement system

A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues.

A low sidelobe level of circularly polarized microstrip array antenna for CP-SAR sensor

In this paper, an elliptical microstrip array antenna with a low sidelobe level for circularly polarized synthetic aperture radar (CP-SAR) sensor is investigated. The low sidelobe level is obtained by implementing the Chebyshev synthesis method to distribute the power unevenly to each element of the patch. A Method of Moment is employed for optimizing the design and achieving a good circular polarization at the working frequency (L-Band). The simulated axial ratio (AR) bandwidth (<3 dB) for the five elements elliptical array antenna is around 11.2 MHz (0.88%), which is consistent with the measured value of 13.3 MHz (1.05%). The maximum sidelobe level of the proposed antenna is 23.3 and 21.4 dB for measured and simulated value, respectively. The simulated and measured results considerably agree with the theoretical design calculated using Chebyshev polynomial of 20 dB. The low sidelobe level and reasonable AR values indicate that the proposed antenna satisfies the specifications of the CP-SAR sensor.

Position‐only side lobe reduction of a uniformly excited elliptical antenna array using evolutionary algorithms

This study deals with the design of elliptical antenna arrays for specific radiation property using three different evolutionary algorithms; namely, self-adaptive differential evolution method, biogeography based optimisation method and firefly algorithm. These methods are used to determine an optimum set of positions for uniformly excited elliptical antenna array (EAA) that provides a radiation pattern with optimum side lobe level reduction with the constraint of a fixed major lobe beamwidth. Three examples are investigated; 8, 12 and 20 elements EAAs using these evolutionary algorithms. The comparison shows that the design of non-uniform EAAs using evolutionary algorithms presents a good side lobe reduction in the radiation pattern for the optimised design. Furthermore, the BBO method shows somewhat better performance compared with the other two methods.

Elliptical Antenna Array Pattern Synthesis with Fixed Side Lobe Level and Suitable Main Lobe Beam width by Genetic Algorithm

In this paper, the design of uniform elliptical array (UEA) with optimum side lobe level reduction is presented. Multi-lobe pattern and adaptive nulling of the pattern is achieved by the control of the antenna elements phases in different states. This method is based on genetic algorithm (GA). The method of genetic algorithm is used to determine an optimum set of array factor cost that provide a radiation pattern with maximum side lobe level reduction with constraint of a suitable main lobe beamwidth. The results show that synthesis of the uniform elliptical antenna array by using GA method provide a side lobe level reduction and main lobe beamwidth better than circular antenna array obtained by using IWO (Invasive Weeds Optimization) and also optimized elliptical antenna array by using EPL (The Excitations Of Elements Phases at Eccentricity Low Level).

A rotated elliptical slot antenna with ultra-wide bandwidth

A novel ultra-wideband elliptical slot antenna is proposed.An elliptical slot is rotated by 45° and excited by a circular patch. Tapered microstrip feeding is used for impedance matching. The structure has multiresonance feature over a wide frequency range, where the simulated bandwidth ratio exceeds 20:1. Due to the limitation of the SMA connector, the experiment on the prototype antenna demonstrated an impedance bandwidth (voltage standing wave ratio < 2) of 165%, or 2.54–26.6 GHZ, 10.5:1. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:308–310, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27288

Radiation by a Slotted Conducting Elliptic Cylinder Coated by a Nonconfocal Dielectric

The characteristics of a slot antenna on a perfectly conducting elliptic cylinder coated by a nonconfocal dielectric are investigated experimentally. Tow prototypes of non-coated and dielectric-coated elliptic slot antennas are designed, fabricated, and tested. The simulations and measurements results of non-coated and nonconfocal coated slot antennas are compared and discussed. It is found that the radiation patterns due to coating material become more directive.

Vesicoureteral reflux in young children: a study of radiometric thermometry as detection modality using an ex vivo porcine model

Microwave radiometry is evaluated for renal thermometry tailored to detect the pediatric condition of vesicoureteral urine reflux (VUR) from the bladder through the ureter into the kidney. Prior to a potential reflux event, the urine is heated within the bladder by an external body contacting a hyperthermia applicator to generate a fluidic contrast temperature relative to normal body temperature. A single band, miniaturized radiometer (operating at 3.5 GHz) is connected to an electromagnetic-interference-shielded and suction-coupled elliptical antenna to receive thermal radiation from an ex vivo porcine phantom model. Brightness (radiometric) and fiberoptic temperature data are recorded for varying urine phantom reflux volumes (20–40 mL) and contrast temperatures ranging from 2 to 10 °C within the kidney phantom. The kidney phantom itself is located at 40 mm depth (skin-to-kidney center distance) and surrounded by the porcine phantom. Radiometric step responses to injection of urine simulant by a syringe are shown to be highly correlated with in situ kidney temperatures measured by fiberoptic probes. Statistically, the performance of the VUR detecting scheme is evaluated by error probabilities of making a wrong decision. Laboratory testing of the radiometric system supports the feasibility of passive non-invasive kidney thermometry for the detection of VUR classified within the two highest grades

A Cavity-Backed Aperture-Coupled Microstrip Patch Antenna Array with Sum/Difference Beams

This paper presents a new cavity-backed aperture-coupled microstrip patch antenna (ACMPA) array with sum/difference beams. It is composed of a feed network and two aperture-coupled elliptical patch antennas. A metallic cavity is used at the back of the antenna array to minimize the back radiation. The feed network is realized by a planar magic-T, which consists of microstrip and slotline T-junctions coupled by microstrip-slotline transitions. The antenna is designed, manufactured and tested at 35 GHz. Measurements show clean and symmetrical patterns are realized for both the sum and difference beams. The measured −3-dB E- and H-plane beamwidths of the sum pattern are 55.8◦ and 77.6◦, respectively. A deep null of −32.4 dB is achieved for the difference pattern. Meanwhile, the measured return losses for both the sum and difference ports are less than 10 dB from 34.2–36.6 GHz corresponding to a bandwidth of 6.8%. Within this bandwidth, the isolation between the sum and the difference ports is better than 38 dB.

Design a new elliptical ultrawideband antenna with dual band-notched characteristics

A novel microstrip-fed ultrawideband elliptical antenna with dual band-notched characteristics is proposed and fabricated. Dual band-notched characteristics are achieved by a defected ground structure and using a tuning stub embedded in the microstrip feed line. The operation bandwidth of the designed antenna is from 2.6 to 12 GHz for voltage standing wave ratio less than 2, except two frequency notched bands of 3.2–4.1 GHz for WiMAX and 4.9–6.0 GHz for wireless local area network. Moreover, the proposed antenna provides a good radiation pattern and a relatively flat gain over the entire frequency band excluding the rejected bands. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:780–783, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26625

HIGH GAIN AND LOW CROSS-POLAR COMPACT PRINTED ELLIPTICAL MONOPOLE UWB ANTENNA LOADED WITH PARTIAL GROUND AND PARASITIC PATCHES

In this paper a low cost, high gain, low cross-polar and compact edge feed printed elliptical antenna with a partial ground plane and parasitic patches is proposed and investigated. The proposed antenna is fabricated on a 1.6mm thick FR4 substrate with dielectric constant of 4.4 and loss tangent of 0.025. The total planar area of the proposed antenna (L £ W) is 28 £ 24mm 2 . Both the simulated and experimental result shows that the proposed antenna provides a frequency range compatible with the ultra-wideband (UWB) standard, i.e., 3.5GHz{12GHz frequency band. The radiation pattern produced by the proposed antenna is approximately omnidirectional with in- phase excitation of Surface waves resulting in less cross-polarization level (less than 20dB) compared to its co-polar component for the entire impedance band width. The maximum measured gain for the fabricated antenna is around 6.27dBi with an average e-ciency of above 90% throughout the bandwidth. A linear phase response (phase of S21) accompanied by a constant group delay of 1ns throughout the measured bandwidth makes the proposed antenna a good candidate for UWB applications.

K-Band Varactor Diode-Tuned Elliptical Slot Antenna for Wideband Imaging

Small resonant elliptical slot antennas have shown great potential as imaging array elements at microwave frequencies. For high-resolution 3D imaging applications it is desirable to extend the operational frequency bandwidth of these elements. One way to achieve this is by loading the slot with a varactor diode, and electronically tuning its resonant frequency. This communication presents the design, analysis, and implementation of a varactor diode-tuned elliptical slot antenna at K-band (18 GHz-26.5 GHz). The slot antenna is then used to produce single-frequency and wideband multi-frequency synthetic aperture radar (SAR) images of two targets located at different distances to show the efficacy of using this slot for wideband imaging.

Improved Radiometric Performance Attained by an Elliptical Microwave Antenna With Suction

We present a new way to securely mount a medical microwave antenna onto the human body for improved in vivo temperature measurements by microwave radiometry. A low cost and simple vacuum pressure source is used to provide suction (negative pressure) on the aperture of an elliptical antenna with vacuum chamber cavity backing. The concept offers improved electromechanical coupling between the antenna surface and the skin of the body. The proposed solution is evaluated experimentally to test repeatability of radiometric temperature measurements by remounting the antenna many times in one sequence on a given anatomical location. Four representative locations (hand, belly, hip, and chest) were used to test the suction antenna concept against anatomical curvature and load variations. Statistical analysis shows a marked decrease in the standard deviation of measured temperatures with the use of suction compared to conventional manual fixation. At repeated measurements, the vacuum antenna produces less uncertainty and improved estimate of the true lossy load temperature. During body movement, the antenna mounted at bone-filled areas shows greatest potential for improved performance.

Vesicoureteral Reflux in Children: A Phantom Study of Microwave Heating and Radiometric Thermometry of Pediatric Bladder

We have investigated the use of microwave heating and radiometry to safely heat urine inside a pediatric bladder. The medical application for this research is to create a safe and reliable method to detect vesicoureteral reflux, a pediatric disorder, where urine flow is reversed and flows from the bladder back up into the kidney. Using fat and muscle tissue models, we have performed both experimental and numerical simulations of a pediatric bladder model using planar dual concentric conductor microstrip antennas at 915 MHz for microwave heating. A planar elliptical antenna connected to a 500 MHz bandwidth microwave radiometer centered at 3.5 GHz was used for noninvasive temperature measurement inside tissue. Temperatures were measured in the phantom models at points during the experiment with implanted fiberoptic sensors, and 2-D distributions in cut planes at depth in the phantom with an infrared camera at the end of the experiment. Cycling between 20 s with 20 Watts power for heating, and 10s without power to allow for undisturbed microwave radiometry measurements, the experimental results show that the target tissue temperature inside the phantom increases fast and that the radiometer provides useful measurements of spatially averaged temperature of the illuminated volume. The presented numerical and experimental results show excellent concordance, which confirms that the proposed system for microwave heating and radiometry is applicable for safe and reliable heating of pediatric bladder.

Novel band-notched ultra-wideband elliptical monopole antenna with dual radiating elements

A novel ultra-wideband design of planar elliptical monopole antenna with dual radiating elements is presented. The proposed antenna consists of two elliptical radiating elements and a ground plane. The antenna has a super-wideband from 2.8 to 15 GHz for voltage standing wave ratio less than 2, except the notched band at 4.8–5.9 GHz for filtering the wireless local area network signal. Based on the contribution of the shorting position d to the notch bandwidth, a particular notch-band range can be designed by adjusting the size of the minor elliptical radiating element. The radiation pattern of the proposed antenna in the yz-plane is omni-directional. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1427–1430, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26023

DUAL BAND-NOTCHED ANTENNA WITH THE PARASITIC STRIP FOR UWB

A novel microstrip-fed ultra wideband (UWB) elliptical antenna with dual band-notched characteristics is proposed. Dual band-notched characteristics are achieved by employing a pair of U- shaped slots on the ground plane and a T-shaped parasitic strip on the backside of the substrate. The operation bandwidth of the designed antenna is from 2.9 to 12GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.2{3.9GHz for WiMAX system and 4.9{6.1GHz for WLAN system. Moreover, the proposed antenna provides good radiation patterns across the working bands and a relatively ∞at gain over the entire frequency band excluding the rejected bands.

Improvement of ECRH Elliptical Mirror Antenna for GAMMA 10

Horizontally steerable ECRH antenna system of central cell on GAMMA 10 is developed for efficient electron heating. The steering mirror antenna can shift horizontally absorption position at the resonance surface in the range of -7.3 ~ +7.3 mm from standard position without significant power reduction which is examined with both calculation and cold power test. As a result of the plasma experiments of the antenna position scan, it is found the horizontally optimized position for ECRH. The spilled RF from mirror(the stray RF) seems to deteriorate the hot ion confinement. The newly installed efficient antenna system which has higher transmission efficiency of ~90% has shown improved heating performance.

Elliptic Cylinder with Slotted Antenna Coated with Magnetic Metamaterials

The radiation properties of an axially slotted elliptic antenna coated with magnetic metamaterials are investigated. The fields inside and outside the dielectric coating are expressed in terms of the Mathieu functions. The boundary conditions at various surfaces are enforced using the orthogonality property of angular Mathieu functions. Numerical results are presented graphically for the radiation pattern, aperture conductance, and antenna gain for the TM case. It was found that a slotted antenna coated with magnetic metamaterials has more gain as well as lower side lobes compared to one coated with conventional dielectric or nonmagnetic metamaterials.

Wideband CPW‐fed elliptical monopole antenna

AbstractAn elliptical monopole antenna with a wide bandwidth is proposed, which is composed of an elliptical monopole patch and a ground plane by uniting a quarter of a disc and a rectangular structure, both printed on the same side of a substrate and fed by a coplanar waveguide (CPW) feeder.The simulated and experimental results demonstrate that this antenna achieves an impedance bandwidth covering 2.6–13.9 GHz for VSWR ≤ 2 and also shows a nearly omnidirectional radiation pattern, which indicates that the proposed antenna performance is suitable for UWB applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1774–1776, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25358

Design of a novel band-notched slot patch antenna for UWB communication systems

A novel band-notched elliptical slot antenna is presented for ultra-wideband (UWB) applications. The proposed antenna is fed via a microstrip-line that is connected to an elliptical shaped patch which incorporates an inverted-U slot. The inverted-U slot behaves like a band reject network designed to eliminate 5.15–5.825 GHz band-limited by IEEE 802.11a and HIPERLAN/2. Effects of varying the inverted-U shaped slot parameters on the antenna's performance show that notch band can be finely tuned. The antenna with optimal parameters was realized and its performance measured. The antenna was fabricated on a RT/duroid 6006 that has a thickness of 1.27 mm and a relative permittivity of 6.15. The size of the actual antenna is 50 × 50 mm2. The radiation characteristics of the proposed antenna satisfy UWB system requirements. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1599–1603, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25237

The Rough Surface Impulse Response of a Pulse-Limited Altimeter With an Elliptical Antenna Pattern

This letter describes the impulse response of a pulse-limited altimeter with an elliptical antenna pattern from a uniformly rough surface inclined at an angle to a sphere or, equivalently, from spherical surface and mispointed antenna. An integral for the impulse response is given, and analytic forms for the special cases of a mispointed circular antenna and a nadir-pointed elliptical antenna are derived. An analytic approximation for the case of small ellipticity and small surface gradient (or mispointing) are also given. The letter is illustrated with numerical examples that show the general effect of ellipticity on the impulse response. It also shows that in the practical case of the elliptical CryoSat-2 satellite SIRAL antenna, the analytic approximation is sufficiently accurate to provide a correction for the ellipticity for CryoSat-2 echoes from the ocean surface.