Slot Elements Research Articles

Feasibility demonstration of a massively parallelizable optical near-field sensor for sub-wavelength defect detection and imaging.

To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. Full physics simulations of the photonic antenna detector element that enables this instrument, show that using conventional red laser light (in the 600 nm range) the detector magnifies the signal from an 8 nm particle by up to 1.5 orders of magnitude. The antenna is a shaped slot element in a 60 nm silver film. The ability of this detector element to resolve λ/78 objects is confirmed experimentally at radio frequencies by fabricating an artificial material structure that mimics the optical permittivity of silver scaled to 2 GHz, and “cutting” into it the slot antenna. The experimental set-up is also used to demonstrate the imaging of a patterned surface in which the critical dimensions of the pattern are λ/22 in size.

РЕЗОНАТОР ФАБРИ–ПЕРО, ОБРАЗОВАННЫЙ ДВУМЯ ЭКРАНАМИ С ПРЯМОУГОЛЬНЫМИ ОТВЕРСТИЯМИ

PACS number: 41.20.–q Purpose: studies of electrodynamics properties of Fabry–Perot resonator formed by two parallel perfectly conducting screens of finite thickness with rectangular holes while its exciting by a plane wave. Design: operator method of diffraction problems solving based on the method of partial areas and the method of generalized scattering matrixes. Findings: The numerical modeling showed that module of the coefficient of plane wave reflection from the resonator is equal to zero at a fixed wavelength being prohibitive for segments of rectangular waveguides made in both screens. Here, a strong localization of electromagnetic field in the resonator volume is observed. Studying the frequencyselective properties of each screen individually it has been determined that there are no resonances of electromagnetic wave total transmission below the cut-off frequency of rectangular waveguides. It is found that with replacing one of the Fabry–Perot resonator mirrors by a solid metal plane, the amplitude of a plane wave in the resonator can increase by almost an order of magnitude as against the exciting field amplitude. Conclusions: Unique electrodynamic properties of the considered structure can find application in devices for amplifying or generating electromagnetic waves in millimeter and submillimeter bands, as well as in measuring electrical properties of composite materials with large losses. Key words: two-dimensional periodic screen, rectangular waveguide, Fabry–Perot resonator, reflection coefficient, ultraboundary waveguide Manuscript submitted 11.11.2015 Radio phys. radio astron. 2016, 21(1): 58-64 REFERENCES 1. EULER, M. and FUSCO, V., 2010. Frequency Selective Surface Using Nested Split Ring Slot Elements as a Lens with Mechanically Reconfigurable Beam Steering Capability. IEEE Trans. Antennas Propag . vol. 58, no. 10, pp. 3417–3421. DOI: https://doi.org/10.1109/TAP.2010.2055814 2. AZEMI, S. N., GHORBANI, K. and ROWE, W. S. T., 2012. 3D Frequency Selective Surfaces. Prog. Electromagn. Res . C. vol. 29, pp. 191–203. DOI: 10.2528/PIREC12033006 3. BANKOV, S. E., DUPLENKOVA, M. D. and FROLOVA, E. V., 2013. Eigenmodes of resonator on the basis of an electromagnetic crystal. Zhurnal Radioelektroniki . no. 7, pp. 1–27 (in Russian). 4. ZIRAN WU, WEI-REN NG, MICHAEL E. GEHM and HAO XIN., 2011. Terahertz electromagnetic crystal waveguide fabricated by polymer jetting rapid prototyping. Opt. Express . vol. 19, no. 5, pp. 3962–3972. DOI: https://doi.org/10.1364/OE.19.003962 5. ANTONENKO, J. V. and GRIBOVSKY, A. V., 2012. Polarization and Frequency-Selective Properties of a Double Screen of Finite Thickness with Coaxial-Sector Aperture. Radio Phys. Radio Astron . vol. 17, no. 3, pp. 276–281 (in Russian). 6. GRIBOVSKY, A. V., LYTVYNENKO, L. M. and PROSVIRNIN, S. L., 2000. Diffraction of Electromagnetic Waves on a Multi-Layer Structure of Metal Screens with Rectangular Holes. Radio Phys. Radio Astron . vol. 5, no. 2, pp. 166–170 (in Russian). 7. PEROV, A. O., KIRILENKO, A. A., DERKACH, V. N. and SALOGUB, A. N., 2015. System of two screens with the circular beyond the limits openings as the quasi-optical polarizer. Radiofizika i Elektronika . vol. 6(20), no. 3, pp. 3–10 (in Russian). 8. LITVINENKO, L. N. and PROSVIRNIN, S. L., 1984. Spectral operators of dispersion in the tasks of diffraction of waves on flat screens . Kyiv: Naukova dumka (in Russian). 9. GRIBOVSKY, A. V., PROSVIRNIN, S. L. and REZNIK I. I., 1997. Reflecting Phased Array Antenna Consisting of Rectangular Waveguides of Finite Depth. Radio Phys. Radio Astron . vol. 2, no. 1, pp. 52–60 (in Russian).

SIW Multibeam Array for 5G Mobile Devices

This paper presents a substrate integrated waveguide (SIW) multibeam slot array operating at $\sim 30$ GHz for future 5G mobile terminal applications. The multibeam forming network is realized with a Butler matrix that is composed of hybrid couplers, crossovers, and phase shifters (135° and 0°). The crossovers are formed with two cascaded hybrid couplers. In the design of 135° and 0° phase shifters, the phase compensation technique is employed. The slot array is a $2 \times 4$ type, in which each column has two slot elements that are longitudinally staggered with respect to one another (in half-wavelength). In addition, mutual couplings reduction techniques applied in the proposed slot array are also discussed. The SIW technique is adopted in case for the related components, as it can be highly integrated in mmWave circuits at low fabrication cost and has low profile characteristics. The overall dimension of the SIW multibeam slot array (including the Butler matrix feeding network) is $72 \times 27.4 \times 0.508$ mm3, and the total area of the slot array is only $10.1\times 20.4$ mm2. The measured 10 dB bandwidth was 28–32 GHz, and the measured gains at 30 GHz for each port were 10.8, 12.1, 12, and 11 dBi. The proposed slot array also possesses wide angle coverage of $\sim 40^{\circ }$ with good steerable radiation.

A 2.4 GHz Switched Beam Antenna for Indoor Applications Using Angle of Arrival Estimation

This study introduces a new design of planar antenna array for ISM band applications at 2.4 GHz. This prototype is switched beam antenna, namely planar antenna with four meandered slotted triangular elements (PAFMSTE), which is proposed for wireless indoor applications. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. The PAFMSTE is used to obtain optimal directivity in four directions in azimuth plane with 3 dB beamwidth of 90° at a specific orientation of 30° in elevation plane. Switched parasitic technique is used to enable PAFMSTE to steer a directional beam through four locations by using four PIN diodes switches. The High Frequency Structure Simulator (HFSS) is used as an efficient simulation tool to optimize the performance of the PAFMSTE antenna. The fabrication and measurements of the PAFMSTE antenna are introduced. The proposed antenna enable radio positioning via Angle of Arrival (AOA) information collected from nearby devices. Then, the Cramér-Rao Bound (CRB) is presented for AOA estimation using identically and equally spaced antenna elements. The CRB depends on the directivity, where the maximum values of CRB are 1.35 × 10-3 and 8 × 10-3 at HPBW of 60° and 90°, respectively.

Beamforming and Angle-of-Arrival Estimation of Square Planar Antenna Array

This paper presents a dual-band planar antenna array for ISM band applications (2.4 GHz and 2.45 GHz). This antenna is proposed for indoor applications and enables adaptive beamforming and angle of arrival (AOA) estimation. An adaptive beamforming algorithm is applied for a planar antenna array, which is able to steer its main beam and nulls in azimuth and elevation planes over a wide frequency band. Planar antenna array operates as a spatial filter in 3D space, processing the received signals with weighting schemes. A planar antenna array is designed for AOA estimation in azimuth and elevation planes by using MUltiple SIgnal Classification (MUSIC) based on subspace algorithm. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. Planar antenna with four elliptical slotted triangular elements (PAFESTE) is used to obtain optimal directivity in four directions in azimuth plane with specific orientation of 30? in elevation plane. It is characterized by half power beamwidth in elevation plane of about 60? and half power beamwidth in azimuth plane of about 90?.

A Substrate Integrated Slot Antenna Array Using Simplified Feeding Network Based on Higher Order Cavity Modes

This paper proposes a novel substrate integrated waveguide (SIW) higher order mode cavity fed $2 \times 2$ -element slot array. The higher order mode cavity feeds all of the slot elements simultaneously, and the resonant mode is excited only by a slot aperture, which helps simplify the feeding network. To enhance the bandwidth, the array is designed as an asymmetric structure with different slot sizes and locations. In this way, new resonances are introduced and thus broaden the bandwidth. Furthermore, the proposed $2 \times 2$ -element slot array is used as subarray to implement a differentially fed $4 \times 4$ -element array. The measured results demonstrate that this simple structure antenna array features wideband, high radiation efficiency, good aperture efficiency, and broadside radiation.

Design of Multiple-Polarization Transmitarray Antenna Using Rectangle Ring Slot Elements

A multiple-polarization transmitarray using rectangle ring slot elements is presented in this letter. Fed by a linearly polarized Vivaldi antenna, this proposed transmitarray can generate radiation patterns with different polarizations, including left-handed circular polarization, right-handed circular polarization, and vertical and horizontal polarizations. The multiple-polarization characteristic is realized by properly rotating the feed antenna around the center and adjusting the x- and y-dimensions of each element. To validate the performance of the designed antenna, a prime-focus 81-element transmitarray has been fabricated and measured. The experimental results show that the fabricated antenna in the CP mode achieves 3-dB axial-ratio bandwidths of 16.7%, while the antenna in the LP mode achieves 1-dB gain bandwidths of 8.3% with the maximum gain of 20.1 dB. The feature of polarization diversity makes the designed transmitarray suitable for the wireless communication systems.

Study of Scattering Parameters and Gain of two Longitudinal Slots of Same Electrical Lengths Milled on two Waveguides for Series and Shunt Slot Array Planar Antenna

This paper presents a study of two longitudinal slots of same electrical lengths milled on two waveguides for series and shunt slot array planar antenna. Initially single longitudinal slot element is milled on waveguide which is called single element waveguide slot antenna (WSA). Two same or different structures of single element WSA are kept either in series or shunt for making of two element longitudinal waveguide series slot array and shunt slot array planar antenna respectively. Theoretical data for the reflection coefficient and transmission coefficient due to mutual impedance have been obtained for two element series and shunt planar WSA. The theoretical data have been compared with simulated data for validation the proposed design structures. The almost outstanding agreement obtained between the results validates the investigation of proposed design structure. After the reflection and transmission coefficients validation, the total gain of the proposed design structures is simulated. The result found in series slot array planar antenna behaves as a multi band within in X-band for the application of the multi frequency selective device for communication and shunt slot array planar antenna behaves as in single band entire coverage of X-band for the application of long distance data communication.

A slotted hollow ring element for Ku‐band high‐efficiency circularly polarized reflectarrays

ABSTRACTBased on the idea of a single‐layer multiresonance structure for a linearly polarized reflectarray, a novel slotted hollow ring element is presented for Ku‐band high‐efficiency circularly polarized reflectarrays. The appropriate geometry parameters are determined by studying the effects of incident angle on the element reflection coefficient. Compared to the conventional microstrip ring element, it can provide a broader CP bandwidth and more accurate phase compensation. Then, using the angular rotation technique, an offset 137‐element reflectarray operating at 12 GHz is designed and fabricated to demonstrate the superior performance of the element. The measured result shows that the reflectarray offers a maximum efficiency of 66.13% at 12.3 GHz. Meanwhile, the efficiency is better than 60% over a 16.8% bandwidth (11.1–13.1 GHz). The overlapping 1‐dB gain bandwidth and 3‐dB axial‐ratio bandwidth can reach 20%. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2629–2632, 2015

Substrate-Integrated Waveguide-Based 60-GHz Resonant Slotted Waveguide Arrays With Wide Impedance Bandwidth and High Gain

Conventional resonant-slotted waveguide arrays can only achieve a few percent of impedance bandwidth. This paper presents a new substrate-integrated waveguide (SIW)-based 60-GHz resonant-slotted waveguide array, which can achieve both wide impedance bandwidth and high gain. In the design, resonant slots with different resonant frequencies are arranged at unequal spacing along the SIW. The variance of the excitation voltages of different resonant slots is minimized to improve the arrays’ impedance bandwidth and gain. A ${\bf 4} \times {\bf 1}$ -element subarray is designed accordingly, which shows a $- {\bf 10}\mbox{-}{\bf dB}$ impedance bandwidth from 56.5 to 66.7 GHz (16.6%) with a peak broadside gain of 11.5 dBi. Based on this subarray, three other arrays with ${\bf 4} \times {\bf 4}$ , ${\bf 8} \times {\bf 4}$ , and ${\bf 8} \times {\bf 8}$ -slot elements are designed, fabricated, and measured. Long nonresonant slots are placed between each two subarrays to improve isolation. Measured results of the three fabricated arrays show $- {\bf 10}$ -dB impedance bandwidths of 20.8%, 22.4%, 18.8%, respectively, and peak broadside gain of 18.3, 19.9, and 22.8 dBi, respectively. The proposed structures exhibit wider impedance bandwidth and higher peak gain than their former counterparts.

Circularly polarized beam-steering antenna array with enhanced characteristics using UCEBG structure

A broadband circularly polarized (CP) beam-steering antenna array is presented. CP antenna is composed of four identical CP slot elements with 2 × 2 configuration and a 4 × 4 feeding network. CP slot element is utilized in array form to improve impedance bandwidth and sequentially rotation method is used to increase axial-ratio bandwidth. Moreover, uni-planer compact electromagnetic band-gap structure is applied to enhance the overall performance of antenna array. Measured results depict that the array has impedance bandwidth over a frequency range of 4.1–7 GHz (~53%) for S11 ≤ −10 dB and 3 dB axial-ratio bandwidth of 1.95 GHz that is between 4.6 and 6.55 GHz (~35%). The antenna array has peak gain of 11 dBi at 5.5 GHz.

A High-Efficiency Transmitarray Antenna Using Double Split Ring Slot Elements

This letter present a high-efficiency transmitarray antenna using a four-layer double split ring slot structure as the unit cell element. The transmission coefficient of the element at different incident angles is analyzed by Ansoft HFSS, and the results show that the element has the advantages of low transmission loss and less sensitivity to the incidence angle of the electric field. A high-efficiency transmitarray antenna composed of four layers of double split ring slot elements is designed, manufactured, and tested at Ku-band. The diameter of the transmitarray antenna is 6.76 wavelengths, and the measured gain is 23.9 dB. Radiation efficiency of 77.6% and aperture efficiency of 55% are achieved at a center frequency of 13.58 GHz in this design. The measured 1-dB and 3-dB gain bandwidths are 7.4% and 17.7%, respectively.

Simulation, Design of Compact Multi-band Microstrip Slot Antennas for WiMAX/WLAN and UWB Applications

In this paper, multiband, printed microstrip-feed monopole antennas using slot elements are proposed. First, an antenna with a dome shaped slot and a blended rectangular shaped patch is designed. The antenna is characterized by an operating frequency band $$(\hbox {S}_{11} < -10\,\hbox {dB})$$(S11<-10dB) from 2.2 to 12.9 GHz. Next, dual and triple-band antenna configurations are obtained by slightly changing some of the dimensions and adding thin $$\lambda /4$$?/4 length metallic strips to the ground plane of the basic design. Resonance of these metallic strips introduces the additional bands at the lower end. The dual band antenna operates from 2.2 to 2.4 and 3 to 13 GHz. The triple-band antenna operates from 2.2 to 2.4, 2.8 to 3.3 and 3.55 to 11.6 GHz. The first antenna is suitable for all the Bluetooth, worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN) and ultra wide band (UWB) applications, whereas the second antenna is suitable for 2.3 GHz WiMAX in addition to UWB applications. The third antenna is suitable for 2.3/3.3 GHz WiMAX, 5.15/5.5 GHz WLAN and UWB applications. All the proposed antennas have simple geometry and radiation patterns which are nearly Omni directional in H-plane and dumbbell shaped in E-plane. The simulated and measured results are in good agreement.

Ground effect due to rough and resonant surfaces

Particularly if the ground surface between noise source and receiver would otherwise be smooth and acoustically hard, structured low-rise ground roughness can be used as an alternative to conventional noise barriers. The techniques of periodic-spacing, absorptive covering, and local resonance can be used, as when broadening metamaterial stop bands, to achieve a broadband ground effect. This has been demonstrated both numerically and through laboratory experiments. Computations have employed multiple scattering theory, the Finite Element Method and the Boundary Element Method. The experiments have involved measurements over cylindrical and rectangular roughness elements and over their resonant counterparts created by incorporating slit-like openings. Resonant elements with slit openings have been found numerically and experimentally to add a destructive interference below the first roughness-induced destructive interference and thereby mitigate the adverse effects of the low-frequency surface waves generated by the presence of roughness elements. A nested configuration of slotted hollow roughness elements is predicted to produce multiple resonances and this idea has been validated through laboratory experiments.

Broadband and high gain waveguide‐fed slot antenna array in the Ku‐band

A broadband and high-gain slot antenna array operating in the Ku-band is reported in this study. The antenna is with waveguide-fed cavity backed configuration and made entirely via simple milling process. The overall antenna structure consists of four layers. The bottom layer is a waveguide feed network to provide corporate power division. In turn, the waveguide feed network is excited by a conventional coaxial probe from the back. The waveguide network couples energy to an array of cavity via an aperture plate. These constitute the middle two layers. Each cavity then excites a subarray of 2 × 2 radiating slots in the top layer. The radiating slot elements and the feed network are designed to achieve wide bandwidth and high-gain performance. Finally, an 8 × 8 array antenna has been designed and fabricated with about 25 dBi gain over 14.8% bandwidth, and the cross-polarisation was around −30 dB in the boresight.

Broadband circularly polarized beam‐steering antenna array for wireless applications

ABSTRACTThis article describes the implementation of a broadband circularly polarized (CP) antenna array for switched beam applications. The antenna comprises of four identical CP slot elements in a 2 × 2 configuration that uses a 4 × 4 feeding network. Each CP slot element in the array is sequentially rotated with respect to each other to enhance the antenna's axial‐ratio (AR) bandwidth. Measured results confirm the array exhibits an impedance bandwidth of 2.25 GHz that extends over the frequency range 4.6–6.85 GHz (∼40%) for S11 ≤ −10 dB, and 3 dB AR bandwidth of 1.7 GHz that extends between 4.8–6.5 GHz (∼30%). The antenna's gain is in excess of 6.8 dBi between 5–6 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2813–2817, 2014

CPW Center-Fed Single-Layer SIW Slot Antenna Array for Automotive Radars

A compact co-planar waveguide (CPW) center-fed substrate-integrated-waveguide (SIW) slot antenna array is proposed to achieve narrow H-plane beamwidth and low sidelobe levels for automotive radars such as across-the-road (ATR) radar. The antenna consists of an array of SIW slot elements, a CPW-SIW transition, and a CPW power divider. A new type of CPW-SIW transition is proposed to minimize the blockage aperture of the slot antenna array for suppressing the sidelobe levels of the array. A parallel center feeding configuration is applied to avoid beam squinting. The antenna prototype printed onto a single-layer Rogers 5880 is with 32 ×4 slot elements and an overall size of 195 mm×40 mm×0.79 mm. Measured results show that the proposed antenna exhibits a gain of > 22.8 dBi, an efficiency of > 67%, a return loss of > 10 dB, a sidelobe level of <;-21 dB, and a fixed boresight beam of <;4.6° in H-planes over 24.05-24.25 GHz, suitable for ATR radar.

Microwave System to Detect Traumatic Brain Injuries Using Compact Unidirectional Antenna and Wideband Transceiver With Verification on Realistic Head Phantom

A portable microwave system to detect traumatic brain injuries is described. The wideband system utilizes a unidirectional antenna, microwave transceiver, and processing and image reconstruction algorithms. The utilized antenna is designed to have a compact three-dimensional (3-D) structure using a slotted dipole element and a folded parasitic structure. It attains directional radiation patterns with an average 9-dB front-to-back ratio and 102.2% fractional bandwidth covering the band 1.1–3.4 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$~$</tex> </formula> GHz, which is suitable for head imaging. To test the system, a realistic head phantom, which attains accurate internal and external anatomical structure and electrical properties, is fabricated by a 3-D printer using a detailed numerical model. Targets imitating the properties of bleeding are inserted at different positions in the fabricated head phantom to emulate brain injury scenarios. The integrated system is used in a virtual arrayed monostatic radar approach to detect the injuries. Using data sets recorded at 32 antenna positions around the head, a back projection algorithm is used to generate images of the scanned head. The achieved results demonstrate the feasibility of such a system as a portable module for brain injuries detection.

Circumferential Traveling Wave Slot Array on Cylindrical Substrate Integrated Waveguide (CSIW)

Traveling wave slot array on cylindrical substrate integrated waveguide (CSIW) is designed, fabricated and measured at K-band. CSIW is formed by wrapping the substrate integrated waveguide (SIW) around the cylinder in the circumferential direction. 16 element longitudinal slot array on the broad wall of single CSIW is designed by the Elliot's design procedure. The spacings between the slot elements are determined to reduce the half power beam width (HPBW) and to obtain good matching at 25 GHz. A 4 × 16 slot array is formed using 4 CSIW array each having 16 traveling wave longitudinal slots and the array is fed by 1 × 4 SIW power divider structure. About 10 ° beam steering is achieved when frequency is swept from 24 to 26 GHz. Gain of the antenna is 14 dB. Very good agreement between the simulated and measured results is obtained.

Simulation of Payload Vibration Protection by Shape Memory Alloy Parts

A system of vibroisolation under consideration consists of a payload connected to a vibrating housing by plane shape memory alloy (SMA) slotted elements. The calculation of the mechanical behavior of the SMA is based on a microstructural theory. Simulations of harmonic and of impact excitations are carried out. The results have shown that protective properties of this system depend on the SMA state. The maximum reduction of the acceleration amplitude for harmonic excitation is reached when the SMA is in the martensitic (pseudo-plastic) state or in the two-phase state. A variation of temperature allows changing the resonance frequency and thus escaping from the resonance and controlling a mode of vibration.