Symmetrical Radiation Patterns Research Articles

Ka‐band antipodal fermi‐linear tapered slot antenna with a knife edge corrugation

AbstractAn antipodal Fermi‐linear tapered slot antenna (AFLTSA) is presented for Ka‐band applications. A substrate integrated waveguide is used to excite the tapered slot. The proposed design has a measured 26–40 GHz wide impedance bandwidth with a return loss below 15 dB. It maintains a flat gain of 16 dB over an entire frequency band. The knife edges are corrugation profile of AFLTSA exhibits side lobe level of −14 dB in H plane and −19 dB in E plane. It has a symmetric radiation pattern as well as a cross polarization level of −22 dB. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:485–489, 2015

Dual-Band Circularly-Polarized Unidirectional Patch Antenna for RFID Reader Applications

A dual-band 0.92/2.45 GHz circularly-polarized (CP) unidirectional antenna using the wideband dual-feed network, two orthogonally positioned asymmetric H-shape slots, and two stacked concentric annular-ring patches is proposed for RF identification (RFID) applications. The measurement result shows that the antenna achieves the impedance bandwidths of 15.4% and 41.9%, the 3-dB axial-ratio (AR) bandwidths of 4.3% and 21.5%, and peak gains of 7.2 dBic and 8.2 dBic at 0.92 and 2.45 GHz bands, respectively. Moreover, the antenna provides stable symmetrical radiation patterns and wide-angle 3-dB AR beamwidths in both lower and higher bands for unidirectional wide-coverage RFID reader applications. Above all, the dual-band CP unidirectional patch antenna presented is beneficial to dual-band RFID system on configuration, implementation, as well as cost reduction.

Function fitting the symmetric radiation pattern of a LED with attached secondary optic.

The analytical model [Moreno and Sun, Opt. Express 16, 1808-1819 (2008)] is applied to LED with attached secondary optics. It is shown that a slightly modified model using only three cosine power functions can be used for the cases with symmetric radiation pattern and that good fitting on realistic examples can be achieved with several standard optimization algorithms including local search heuristics and genetic algorithm.

Plasmonic Grid Array of Gold Nanorods for Point-to-Point Optical Communications

A novel wire-grid array of nanorods is introduced. The array consists of five gold radiating rods and four gold perpendicular connecting rods. Each rod represents a plasmonic transmission line supporting single Surface Plasmon Polariton mode guided to the interface between the metal and surrounding dielectric. The propagation characteristics of this single strip plasmonic transmission line are studied using an integral equations formulation solved using the Method of Moments. The new array is designed for operation at a wavelength of 1.55 μm, which is commonly used by optical communication systems. The overall physical and electrical sizes of the array are (0.68-by-1.05 μm) and (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> -by-3λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> /2), respectively. The maximum directivity of the proposed wire-grid nantenna array on top of a substrate with refractive index of 2 reaches 15.24 dBi. The proposed wire-grid nantenna array has a symmetric radiation pattern with reasonable side-lobe-level and extremely low cross-polarization level.

Low-Cost High-Gain and Broadband Substrate- Integrated-Waveguide-Fed Patch Antenna Array for 60-GHz Band

A low-cost high-gain and broadband substrate integrated waveguide (SIW)-fed patch antenna array is demonstrated at the 60-GHz band. A single-layered SIW feeding network with wideband T-junctions and wideband high-gain cavity-backed patch antennas are employed to achieve high gain and wideband performance simultaneously. Although the proposed antenna array has a multilayered structure, it can be fabricated by conventional low-cost single-layered printed circuit board (PCB) technology and then realized by stacking and fixing all of single layers together. The simulated and measured impedance bandwidths of a 4 × 4 antenna array are 27.5% and 22.6% for 10 dB. The discrepancy between simulation and measurement is analyzed. A gain up to 19.6 dBi, and symmetrical unidirectional radiation patterns with low cross polarization are also achieved. With advantages of low fabrication cost and good performances, the proposed antenna array is a promising candidate for millimeter-wave wireless communication systems.

Meta‐surfaces and antennas' radiation characteristics enhancement: planar microstrip and microstrip‐based quasi‐aperture antennas

Meta-surfaces as artificial magnetic conductors or high impedance surfaces to control the electromagnetic fields excited by a microstrip patch resonator are investigated for planar and non-planar structures. In the planar structure, two types of meta-surfaces are used as electromagnetic transducers to transform the captured non-radiating waves to radiated space waves, leading to about 4 dBi gain enhancement. Alternatively, by applying these surfaces as E-plane fences in two sides of a patch, a compact microstrip-based quasi-aperture antenna is proposed. The proposed antenna not only improves the gain up to 8 dBi, but also provides almost a symmetric radiation pattern by controlling the phase distribution of electric fields in the antenna aperture. Using near electric-field pattern inspection and characterising the meta-surfaces, the radiation mechanism of the proposed antennas are delineated. Two antenna prototypes are fabricated and tested and, confirming the simulated ones, the corresponding measured results are presented.

Sensing probe for 3–6 GHz microwave imaging systems

A sensing probe for medical imaging diagnostic systems is presented. The proposed probe consists of a double-ridged waveguide (DRWG) filled with dielectric ceramic and an aperture with a tapered ridge. The DRWG is used to suppress higher-order mode radiations in the rectangular waveguide. The proposed probe is designed for broadband sensing in an immersion liquid with a complex dielectric constant. The performance of the fabricated probe successfully covers the frequency band of 3-6 GHz. The probe suppresses higher-order modes and provides symmetric and similar radiation patterns within the operating frequency range.

Radiant fluxes from on- and off-axis point sources irradiating a circular disc through two different homogeneous isotropic media

The multidomain integral equation method is used to calculate fluxes of radiation from various on- and off-axis point sources passing through two different homogeneous isotropic media and striking a surface of a circular disc perpendicular to the optical axes of these sources. This method is dedicated to radiation passing through attenuating or nonattenuating media with a Fresnel interface and is applicable for arbitrary radiation patterns of point sources. The paper presents, firstly, the generalized multidomain integral equation method, expressed by double iterated integrals, for calculating radiant fluxes from arbitrary emitting point sources. This generalized method is simplified then to the form of multidomain single integral equation method applicable for rotationally symmetrical radiation patterns with optical axes perpendicular to the disc. Next, the simplified method is used for computer simulation of radiant fluxes incident on the disc from small Lambertian and Gaussian sources represented by point source models. All numerical results obtained from this simulation have shown high accuracy and efficiency of the presented method. Selected results are illustrated graphically and validated by Optical Software for Layout and Optimization (OSLO) from Lambda Research Corporation. Potential applications of the presented method include optical sensing and metrology, optical coupling, immersion microscopes, light-extraction problems and creative lighting design.

Size-reduction and suppression of cavity-resonances in hybrid mm-wave antennas for polarimetric measurements

Size and feed structure are some of the important constraints for using antenna-elements in multi-element two-dimensional arrays, where easy planar integration and appropriate matching with transceiver chips are essential. This applies especially when differential signaling and adaptable polarization are required. Based on a balanced-fed patch-excited cavity-backed horn antenna (hybrid antenna), feeding concepts, and approaches to reduce size are discussed and evaluated in this paper. The influence of the substrate-integrated cavity is analyzed and methods to overcome the restrictions are presented, together with simulated and measured results. The antenna elements are evaluated with regard to their use in multistatic and polarimetric sparse arrays, which will be briefly introduced. The optimized antennas achieve 10 dB return loss, a gain of more than 5 dBi as well as symmetric and homogeneous radiation patterns in amplitude and phase with low cross-polarization in the desired frequency-band of operation between 70 and 80 GHz.

Reconfigurable microstrip annular ring antenna for circular polarization diversity

ABSTRACTThis article presents a novel design of a microstrip annular ring antenna with reconfigurable circular polarization (CP) diversity by switching one corner perturbation segment. The proposed antenna has a construction of a single‐feed annular ring as a radiator and frequency perturbing elements at one diagonal edge. To achieve the condition with left‐ and right‐handed CP diversity, the perturbations of the proposed antenna uses the concept of positively and negatively slot‐loaded annular ring. By controls of two diodes' states in the perturbation, both of CP senses have been easily alternated. The simulated and measured results show good and symmetrical radiation patterns at each resonant frequency. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1706–1709, 2014

Multi-Band Miniaturized Patch Antennas for a Compact, Shielded Microwave Breast Imaging Array.

We present a comprehensive study of a class of multi-band miniaturized patch antennas designed for use in a 3D enclosed sensor array for microwave breast imaging. Miniaturization and multi-band operation are achieved by loading the antenna with non-radiating slots at strategic locations along the patch. This results in symmetric radiation patterns and similar radiation characteristics at all frequencies of operation. Prototypes were fabricated and tested in a biocompatible immersion medium. Excellent agreement was obtained between simulations and measurements. The trade-off between miniaturization and radiation efficiency within this class of patch antennas is explored via a numerical analysis of the effects of the location and number of slots, as well as the thickness and permittivity of the dielectric substrate, on the resonant frequencies and gain. Additionally, we compare 3D quantitative microwave breast imaging performance achieved with two different enclosed arrays of slot-loaded miniaturized patch antennas. Simulated array measurements were obtained for a 3D anatomically realistic numerical breast phantom. The reconstructed breast images generated from miniaturized patch array data suggest that, for the realistic noise power levels assumed in this study, the variations in gain observed across this class of multi-band patch antennas do not significantly impact the overall image quality. We conclude that these miniaturized antennas are promising candidates as compact array elements for shielded, multi-frequency microwave breast imaging systems.

Isolation enhancement in wideband dual‐polarised suspended plate antenna with modified T‐type probes

An isolation enhancement technique for a wideband (1.71–2.17 GHz) and ±45° linear dual-polarised suspended plate antenna is proposed. Isolation (S 12, S 21) between channels is improved by making extensions on suspended plates (SPs) 1–2 and inserting a vertical ungrounded vertical wall under SP-1. The modified T-type probes in this design provide better coupling and return losses (S 11, S 22) for wideband operation. Based on the numerical simulations and measurements, it is observed that 8.2 ± 0.5 dBi gain and 66° ± 6° symmetric azimuth and elevation radiation patterns are obtained. Return losses ≤ − 15 dB and isolation ≤ − 30 dB are achieved in the entire band. This antenna is suitable for base stations of mobile wireless communication systems (PCS, DCS and IMTS ).

A 60-GHz Dense Dielectric Patch Antenna Array

The dense dielectric (DD) patch antenna is investigated at the 60-GHz band. By employing the printed circuit board (PCB) technology, a 4 4 aperture-coupled DD patch antenna array is designed, fabricated and studied. An impedance bandwidth of 23.7% from 51.3 to 65.1 GHz for |S11| <; -10 dB, a gain up to 16.5 dBi with a 3-dB gain bandwidth of 32.5%, and symmetrical broadside radiation patterns with -15 dB cross-polarization are achieved.

On reflector feeds with unidirectional axially symmetric radiation patterns: Their cross-polarization performance and efficiencies

The performance and radiation mechanisms of feed antennas with unidirectional axially symmetric radiation patterns are investigated in detail. Radiating circular apertures, electric-magnetic dipole pairs, and two-element elliptical dipole arrays are discussed. The performance metric considers both the maximum cross-polarization level and the efficiency performance when evaluated on a general reflector system with various focal-length-to-aperture-diameter (F/D) ratios. The axial symmetry and cross-polarization performance are strongly dependent on a complementary or higher-order mode being present. For the three classes of feeds investigated, equivalent performances can be achieved with the maximum cross-polarization levels below ?40 dB, and the maximum asymmetry below 0.3 dB. Apertures perform the best in terms of symmetry, and electric-magnetic dipole pairs perform the worst. It is shown that for a two-element dipole array to achieve optimum performance, the dipoles need to be perfectly circular, and the dipole lengths need to be longer than a half-wavelength, to allow for a second-order current mode to coexist with the fundamental mode.

Design and Prototyping of A Compact 2S Shaped Dual Band Patch Antenna

A compact planar microstrip line fed 2S patch antenna has been designed and fabricated on the dielectric material substrate for D band applications. The proposed antenna is designed and analysed by using widely used finite element method based high frequency electromagnetic simulator HFSS. Measurement results show that the impedance bandwidths (return loss less than -10 dB) of the proposed antenna are 1.2 GHz ranges from 5.25 GHz to 6.40 GHz and 2.8 GHz from 10.9 GHz to 13.8 GHz. The simulated gain 2.09 dBi, 5.8 dBi, and 5.7 dBi with radiation efficiency 45 %, 64 % and 66 % have achieved at three minimum return loss frequencies 5.6 GHz, 11.5 GHz and 12.7 GHz respectively. The measured almost symmetric and stable radiation pattern makes the proposed antenna suitable for C, X, and Ku band applications. Furthermore, the effect of the size of cutting lots over the radiating patch on the return loss has been analysed. DOI: http://dx.doi.org/10.5755/j01.eee.20.1.6171

An Improved Wideband Dipole Antenna for Global Navigation Satellite System

In this letter, an improved wideband dipole antenna is proposed for BEIDOU/GPS/GLONASS/GALILEO systems. The proposed antenna includes crossed narrow magneto-electric dipoles that are excited by two Γ-shaped strip probes, a 3-dB hybrid coupler, and reflecting plate. The experiment results reveal that the proposed antenna achieves a wide impedance bandwidth of 51.4% (1.1-1.85 GHz) for VSWR <; 1.5. A 3-dB axial-ratio bandwidth of 42.9% (1.1-1.7 GHz) and a gain of 5.6 ±0.6 dBi are covered by the whole operating band. Moreover, in the operating bandwidth, very stable, symmetrical radiation patterns and high gain at the low angle are obtained.

무궁화 5호 위성통신용 Ka대역 안테나 설계

In this paper, we have designed the antenna for Korea SAT-5 Satellite Communication which can use Ka band in the earth station. The antenna structure consist of the the dual-offset gregorian reflector that has high gain and efficiency, the corrugatedhorn that has symmetric radiation patterns and low side lobe levels, the iris polarizer thatmake circular polarization and the OrthoMode Transducer that separate transmitting and receiving signals. The designed antenna gain is more than 45.7㏈i in Tx-band which use LHCP and 42.0㏈i in Rx-band which use RHCP. The co-polarized and cross-polarized radiation pattern comply with ITU-R S.580-6 and S.731-1 that are recommended by International Telecommunication Union in the geostationary satellite. The Axial ratio is less than 1.0㏈ in Tx-band and 1.5㏈ in Rx-band that meet MIL-STD-188-164A.

A Wideband Dual-Band Magneto-Electric Dipole Antenna With Improved Feeding Structure

In this letter, a wideband dual-band magneto-electric dipole antenna with improved feeding structure is presented. A U-shaped electric dipole antenna is employed to generate the dual resonant frequencies. A folded shorted patch that works as a magnetic dipole antenna is assembled vertically to the ground plane. The antenna is excited by a novel feeding line with a polygonal structure that is designed to improve the impedance matching. Simulated and measured results show that the dual operation bands with bandwidths of 72% from 1.48 to 3.15 GHz and 21% from 4.67 to 5.78 GHz for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB were achieved. Stable and symmetric unidirectional radiation patterns, low cross-polarization level, low back-radiation, and an antenna gain ranging from 6.5 to 9.1 dBi were obtained over the dual operating bands.

A Wideband Circularly Polarized Cross-Dipole Antenna

This letter introduces a wideband circularly polarized (CP) cross-dipole antenna fabricated on a double-layered printed circuit board (PCB) substrate for 2.45-GHz ISM band wireless communications. Unlike conventional cross-dipole antennas, the proposed cross dipole is designed with wide open ends such that both impedance and axial-ratio (AR) bandwidths are enhanced. In addition, to excite the CP radiation effectively, a curved-delay line providing an orthogonal phase difference among the cross-dipole elements is attached at the corners of the sequentially rotated elements. By choosing a proper radius of the curved-delay line, a wide input impedance of the antenna can be realized. The antenna is center-fed by a 50- Ω coaxial cable and is placed above a square reflector to obtain a directional CP radiation pattern. With the advantage of centered feed, symmetric CP radiation patterns can be achieved across the entire operating bandwidth. Simulated and measured results confirm the proposed antenna produced good CP characteristics. An impedance bandwidth (for VSWR ≤ 2) of about 50.2% (1.99-3.22 GHz) and the 3-dB AR bandwidth of about 27% (2.30-2.9 GHz) around the center frequency of 2.45 GHz were measured. The antenna has an average CP gain of 6.2 dBic across the operating bandwidth and the maximum gain of 6.8 dBic at the center frequency. The size of antenna is 0.45λ×0.45λ×0.24λ.

Design and realization of a planar ultrawideband antenna with notch band at 3.5 GHz.

A small antenna with single notch band at 3.5 GHz is designed for ultrawideband (UWB) communication applications. The fabricated antenna comprises a radiating monopole element and a perfectly conducting ground plane with a wide slot. To achieve a notch band at 3.5 GHz, a parasitic element has been inserted in the same plane of the substrate along with the radiating patch. Experimental results shows that, by properly adjusting the position of the parasitic element, the designed antenna can achieve an ultrawide operating band of 3.04 to 11 GHz with a notched band operating at 3.31–3.84 GHz. Moreover, the proposed antenna achieved a good gain except at the notched band and exhibits symmetric radiation patterns throughout the operating band. The prototype of the proposed antenna possesses a very compact size and uses simple structures to attain the stop band characteristic with an aim to lessen the interference between UWB and worldwide interoperability for microwave access (WiMAX) band.