An antenna designated mainly for cellular telephony purposesis presented. It coversone full band from 690 MHz to 2700 MHzwith 6 dB return-loss criterion. The antenna is dimensioned 45 mm by 22.5 mm and is 0.8 mm in thickness. It is composed of a T-shaped monopole on the front-side and a meandered line on the back-side of an FR4 substrate. The T-shaped monopole is responsible for the high-band resonances. The meandered line is divided into three parts: the first partfunctions as a distributed inductor; the second part plays the role as a low-band resonator, and the third part is a tuning element. The distributed inductor and the low-band resonator are both folded strips in configuration, but with different spacing. The tuning element is used to improve the match so that one full band operation can be realized. To clarify the operational mechanism, modesseparately generated from each part are analyzed and compared to modes of the proposed antenna.
Three bent waveguides are proposed and investigated, two for circular waveguide TM01 mode transmission and one for coaxial TEM mode transimission. For high power-handling capacity, all of them are over-mode waveguides. In the bend, circular or coaxial waveguides transmitting only sector waveguide TE11 modes are split into several same sector waveguides by metal plates and metal rod. Those sector waveguides are grouped by their lengths. Different lengths of sector waveguides mean there are phase differences of the TE11 modes after bending. Due to requirements of mode conversion, the phase difference regulated by radii of circular waveguide and metal rod must be 2nπ, n = 0, 1, 2…. Since the phase difference is independent of bend radius, the radius could be as small as possible. One of the prototypes is experimented, and the test result of the VSWR shows that simulation has good match with experiment. Insertion loss is 0.2 dB at 8.4 GHz, which proves the feasibility of the prototype.
In this paper, a microstrip lowpass filter with -3 dB cutoff frequency of 3.8 GHz consisting of two cascaded resonators with flabelliform patches and two symmetric suppressing cells is proposed. To design the filter, the impact of each transmission line on the frequency response is determined by extracting the equations of the insertion loss (S21) and return loss (S11) on the basis of the equivalent LC circuit of the main resonance cell and the cascaded structure. The designed filter is constructed and tested, and a good agreement between the results of simulation and measurement is obtained. In the whole stopband region, a return loss close to zero and an acceptable suppression level of -30 dB from 4.47 to 25.17 GHz are achieved. Furthermore, a flat insertion loss in the passband and a low return loss (-23.02 dB) in the stopband can prove desired in-band and out-band frequency response.
Design of a compact Substrate Integrated Waveguide (SIW) transmission line is presented in this paper. The main parameters of SIW were parametrically studied, and nal designed component was fabricated and measured, which showed very good matching (near 90%) with simulations, demonstrating significant miniaturization factor. The miniaturization was done using Half-Mode (HM) and Slow-Wave (SW) principles together. It was found that the HM-SW method for SIW miniaturization reduced the SIW surface area with a remarkable factor value (70%) while maintaining acceptable characteristics compared to the original SIW. In fact, HM technique reduced 40% the lateral dimension of the SIW, and using the SW technique allowed 30% of size reduction added to the HM principle. Furthermore, a proper microstrip to HM-SW-SIW tapered transition was designed, which showed a return loss decrease between 3 dB and 7.5 dB, as well as facilitating measurement. On the other hand, the proposed transmission line could lead to a size reduction of 30% compared to the HM-SIW miniaturization technique. The HM-SW-SIW transmission line concept presented in this paper can be used to design other compact SIW components such as bandpass filters, couplers, and power divider.
In the present work, a compact size, dual-band antenna is proposed for WLAN/WiMAX/LTE2500/DMB applications. The designed antenna is fed by a 50 Ω coplanar line. The radiating component of the composed antenna consists of radiating strips with half hexagonal and vertical rectangular shapes and square-shaped ground plane which are printed on the same layer. The overall size of the antenna substrate is only 10 x 24 x 1.6 mm3. The simulated and measured results of the proposed antenna show that it operates in the frequency range of 2.5 GHz to 2.75 GHz and 5.0 GHz to 6.7 GHz, respectively.
Multiple target situation is a typical situation of nonhomogeneous clutter environment, which can cause excessive target masking in radar signal detection system. In order to reduce target masking caused by multiple target situations, this paper proposes a new detection structure based on positive-denite matrix space and limited training samples. The proposed detection structure uses a positive-denite matrix to estimate the background power level. In addition, with limited training samples, the detection structure is used to resist the multiple target situations. The simulation results show that the proposed detection structure exhibits a better detection performance than that of the well-known CA-CFAR in homogeneous environment. The detector also performs robustly in multiple target situations, even though 10 interfering targets exist in a length of 24 samples of reference window. Furthermore, the measured results validate the performance of the proposed method.
The presence of the primary field in the helicopter transient electromagnetic system makes the dynamic range of the response signal so large that it is difficult to observe the secondary field. Therefore, a bucking coil is usually introduced to eliminate the primary field. However, in a traditional design, the size of the bucking coil increases with the size of the system, which makes the bucking coil hard to install, and opposite magnetic moment is large in huge systems. In this paper, a new bucking coil design for a helicopter transient electromagnetic system is proposed. Compared with the traditional design, the bucking coil diameter, total weight and total magnetic moment in two designs are calculated. The results show that the bucking coil we designed is more than 8 times smaller and 5 times lighter than that in the traditional design, which is easier for installation. The bucking moment impact is reduced to 0.03% of the total magnetic moment when the diameter of the transmitting coil increases to 35m, which improves the efficiency of the system. Then we analyze the requirement of manufactory precision and installation accuracy for the bucking coil in our design to get the best bucking result.
In this work, an E-shape Defected Ground Structure (DGS) is achieved to reduce the mutual coupling between two nearby microstrip antennas up to 47%(from 0.064 to 0.03). Both antennas radiate in the same frequency band of 10 GHz. The technique is based on a wall integrating periodic structure permitting the absorption of the electromagnetic field. By using this structure, it was possible to achieve a 20dB reduction in the insertion loss S21 between the two microstrip patch antennas with center-to-center distance of 0.37λ0 (λ0 is the free-space wavelength). The obtained coupling coefficient demonstrates that we have a good isolation between the two antennas. EM solver, simulating and measuring the reflection and transmission coefficients of the designed antenna arrays, achieves the reduction of the mutual coupling. The simulated results are verified by measuring the fabricated prototypes.
In the spatial dimension, the variation of the wind speed along the overhead transmission line makes the conductor temperature and line parameter show a nonuniform distribution characteristic, which has an important influence on the operating status of the system. In order to describe the actual situation more accurately, a line cutting model based on the wind speed variation along the line is proposed. This paper proves the application value of the model by using a typical 4-bus system. From the two aspects of the power flow and the maximum power transmission capacity, we contrast the line cutting model with the traditional models, indicating that the cutting model is closer to the actual situation of the system.
This paper presents a novel binary algorithm named as binary butterfly mating algorithm (BBMO) combined with sub-array strategy for thinning of antenna array. The proposed algorithm has been adapted from a recently developed nature inspired optimization, butterfly mating optimization (BMO). The subarray strategy is dividing the linear array into two parts, one part with a fixed number of element turned on in the middle of array and the rest elements on the edge of array composing another subarray. In order to reduce the complexity of the thinning process, BBMO algorithm is used to optimize the element on the edge of an array. The proposed BBMO with subarray strategy is used to synthesize a linear sparse antenna array in order to reduce maximum sidelobe level and at the same time keeping the percentage of thinning equal to or more than the desired level. To evaluate the performance of the proposed thinning method, a linear array with 100 elements is optimized by BBMO algorithm without and with subarray strategy. And we discuss the impact of number of fixed elements on thinning results. The novel method BBMO with subarray strategy gives reduced SLL as compared to the results available in literature of ant colony algorithm, genetic algorithm, binary differential evolution algorithm, chaotic binary particle swarm optimization, and improved binary invasive weed optimization algorithm. Moreover, the convergence rate of BBMO with subarray strategy is faster than BBMO without subarray strategy and the other methods.
A parallel frequency-dependent, finite-difference time domain method is used to simulate electromagnetic waves propagating in dispersive media. The method is accomplished by using a single-program-multiple-data mode and tested on up to eight Nvidia Tesla GPUs. The sppedup using different numbers of GPUs is compared and presented in tables and graphics. The results provide recommendations for partitioning data from a 3-D computational model to achieve the best GPU performance.
On the basis of equivalent circuit analysis, we investigated the electromagnetic characteristics of artificial dielectric layers (ADLs) having arrays of square metal patches for the normal incidence of plane waves, where the electromagnetic wavelength ranges from p/10 to p/2 (p: period). A good agreement was obtained between measured and calculated S parameters and electromagnetic parameters (permittivity and permeability) for a fabricated ADL except at around 5.2 and 9.2 GHz. A possible cause of the discrepancy between the measured and calculated electromagnetic characteristics is discussed by investigating the electromagnetic wave propagating along the surface of the ADL. Applications of the equivalent circuit analysis to ADLs with other geometries are also discussed.
This work presents the design of a magneto-electric dipole (MED) antenna for the base station antenna of FM radio broadcasting implementation. The advantages of MED antenna are high gain, stable and symmetrical radiation patterns in both electric and magnetic planes, and low back lobe radiation pattern. The antenna was designed and studied to achieve the optimal dimensions of configuration parameters. The prototype antenna was fabricated and measured to validate its S11, radiation patterns, and gain. The impedance bandwidth was 33.49%, and the average gain was 7.78 dBi at the entire operating frequency (88-108 MHz). The measured results are in good agreement with the simulated ones.
This paper describes experimental studies of passive intermodulation due to metal-metal contacts. These studies cover the in uence of roughness surface prole and of the thin native oxide layer on PIM value versus contact axial forces. A complete description of a dedicated test bench used during dierent studies is done. Moreover, obtained results are compared to observations published earlier.
A novel method for generating electromagnetic field with orbital angular momentum (OAM) and correspondingly a practical design based on conical horn antenna are proposed in this paper. The OAM modes of ±m for r/φ field components and ±(m-1) for x/y ones can be generated by superposing the two orthogonal polarization degenerate TEmn modes in circular waveguide through a mode-transformation section, and then radiated from the horn in the far end. The effectiveness of the proposed method is analyzed from physical mechanisms and demonstrated by both simulation and experiment for the presented new-typed OAM horn antenna.
In this paper, a fractal tetrahedron shaped dielectric resonator antenna (DRA) design for wideband applications is proposed. Two triangular-shaped fractal slots of different sizes are introduced to reduce Q-factor of DRA and in turn to achieve wide bandwidth (BW). Internal coaxial feeding is utilized for good impedance matching and ease of fabrication. The proposed fractal DRA is fabricated and tested. The measured results are in good accordance with the simulated ones. Measured impedance bandwidth of about 72.3% covering frequency band of 3.8-8.1 GHz is achieved. Good separation between co- and cross-polarized radiation patterns in broadside direction is achieved. Various design parameters and associated results are discussed in this paper.
Simulation and experimental measurement of a new design of an oblique incidence and polarization insensitive metamaterial absorber with multiband absorption is presented in this paper. The unit cell of the proposed metamaterial absorber comprises concentric continuous rings of different radii and widths placed in four different quadrants with identical pair of rings placed diagonally opposite, with each ring responsible for high absorption. The calculated dispersion behavior of MM absorber in terms of effective permittivity (εeff), effective permeability (μeff), and refractive index (ηeff) shows the metamaterial characteristics. The surface current and field distributions in MM absorber are simulated to understand the occurrence of absorption bands. The measured results show the absorption peaks of 99.5%, 99.8%, 99.5% and 99.9% at 7.20 GHz, 9.3 GHz, 12.61 GHz, and 13.07 GHz, respectively. The simulated results are well supported by the experimentally measured performance of the fabricated metamaterial absorber. It offers multiband absorption with bands lying in C-band, X-band and Ku-band for mobile communication, satellite communication and radar applications. With merged third and fourth absorption peaks, the proposed metamaterial absorber structure exhibits a broadband absorption.
In recent years, radio tomographic imaging (RTI) is an emerging device-free localization (DFL) technology enabling the localization of people and other objects without requiring them to carry any electronic device. Different from other DFL techniques, the RTI method makes use of the changes of received signal strength (RSS) measured on links of the network to estimate the radio frequency (RF) attenuation field and forms an image of the changed field. This image is then used to infer the locations of targets within the deployed network. However, there still lacks an efficient scheme which can achieve robust location estimation performance with low computational cost. To solve this problem, we propose a lightweight robust RTI approach in this paper. The proposed method not only can reduce the algorithm's storage and computational resource requirements, but also exploits the location information of wireless measurement nodes to improve the accuracy of the localization result, which ensures its robust performance. The effectiveness and robustness of the proposed scheme are demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and complexity.
In this paper, the direction of arrival (DOA) and polarization parameters are estimated by a uniform circular array (UCA) with several single-polarized sensors. An ecient and improved polarization MUSIC algorithm for estimating the DOA and polarization parameters is presented. This method uses information on the amplitude to reduce the computational complexity. When the source is linearly polarized, the proposed algorithm is more accurate at a low signal-to-noise ratio (SNR). Monte Carlo simulations verify the ecacy of the proposed method.
We propose a novel numerical approach for the optimal design of wide-area heterogeneous electromagnetic metasurfaces beyond the conventionally used unit-cell approximation. The proposed method exploits the combination of Rigorous Coupled Wave Analysis (RCWA) and global optimization techniques (two evolutionary algorithms namely the Genetic Algorithm (GA) and a modied form of the Articial Bee Colony (ABC with memetic search phase method) are considered). As a specic example, we consider the design of beam deflectors using all-dielectric nanoantennae for operation in the visible wavelength region; beam deflectors can serve as building blocks for other more complicated devices like metalenses. Compared to previous reports using local optimization approaches our approach improves device eciency; transmission eciency is especially improved for wide deflection angle beam deflectors. The ABC method with memetic search phase is also an improvement over the more commonly used GA as it reaches similar eciency levels with a 35% reduction in computation time. The method described here is of interest for the rapid design of a wide variety of electromagnetic metasurfaces irrespective of their operational wavelength.