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101.
This article describes a new technique for pattern squint elimination of quad‐ridged conical and pyramidal horn antennas by introducing bended coaxial probes. Because of the phase difference and mutual coupling between vertical and horizontal polarizations, the radiation patterns of the conventional quad‐ridged conical and pyramidal horn antennas squint over a wide bandwidth. The proposed technique substantially reduces the phase difference and coupling between the two probes, so a significant improvement in the radiation patterns over the frequency band of 8–18 GHz can be achieved. The designed modified horn antennas are most suitable as a feed element in reflectors of radar systems and EMC applications. The proposed modified antennas have a voltage standing wave ratio (VSWR) less than 2.2 for the frequency range of 8–18 GHz. Moreover, the proposed antennas exhibit high gain, dual‐polarization performance, good isolation, low SLL, low back lobe, low cross polarization, and satisfactory far‐field radiation characteristics for the entire frequency band. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010. 相似文献
102.
An accurate impedance matrix interpolation technique based on the surface integral equation (SIE) is presented for the analysis of wireless communication antennas over wide frequency bands. The first‐order derivative of the impedance matrix at the internal frequency is considered in the cubic polynomial‐based interpolation scheme, thus the novel impedance matrix interpolation scheme will provide high accuracy and high efficiency over a frequency band. To demonstrate the efficiency and accuracy of the proposed method, numerical results for planar inverted F antennas (PIFA) and a wideband E‐shaped patch antenna are presented. Good agreement among the interpolation results, exact MoM solutions, finite element method (FEM) solutions, and measured data is observed over the bandwidth. Besides, dimensions of the feeding probe are also studied to investigate their effect on the input impedance and radiation patterns. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. 相似文献
103.
104.
M. Naeem D.C. Lee 《Engineering Applications of Artificial Intelligence》2011,24(6):1046-1051
In this paper, we present a low-complexity algorithm for real-time joint transmit and receive antenna selection in MIMO systems. The computational complexity of exhaustive search in this problem grows exponentially with the number of transmit and receive antennas. We apply Binary Particle Swarm Optimization (BPSO) to the joint transmit and receive antenna selection problem. In addition, applying the general BPSO to joint antenna selection, we also present a specific improvement to this population-based heuristic algorithm, namely, we feed cyclically shifted initial population so that the average convergence time (the number of iterations until reaching an acceptable solution) is reduced. The proposed BPSO for joint antenna selection problem has a low computational complexity, and its effectiveness is verified through simulation results. 相似文献
105.
106.
In this article, a metamaterial inspired microwave absorber is used to reduce the cross‐polarization (XP) level of the radiated wave in microstrip antenna (MSA). A microwave absorber unit‐cell has been analyzed and implemented to reduce the cross polarization (XP) level in a single element and a 2 × 2 microstrip patch array antennas. The antennas have been designed on a FR‐4 substrate of thickness 0.8 mm at 10.1 GHz center frequency. The 2 × 2 patch array antenna with and without the absorbers have been experimentally verified for the S11 parameter, the radiation pattern, and the XP suppression in H‐plane and a good comparison has been found. 相似文献
107.
Expedited simulation‐driven design optimization of UWB antennas by means of response features 下载免费PDF全文
In this work, a method for fast design optimization of broadband antennas is considered. The approach is based on a feature‐based optimization (FBO) concept where reflection characteristics of the structure at hand are formulated in terms of suitably defined feature points. Redefinition of the design problem allows for reducing the design optimization cost, because the dependence of feature point coordinates on antenna dimensions is less nonlinear than for the original frequency characteristics (here, S‐parameters). This results in faster convergence of the optimization algorithm. The cost of the design process is further reduced using variable‐fidelity electromagnetic (EM) simulation models. In case of UWB antennas, the feature points are defined, among others, as the levels of the reflection characteristic at its local in‐band maxima, as well as location of the frequency point which corresponds to acceptable reflection around the lower corner frequency within the UWB band. Also, the number of characteristic points depends on antenna topology and its dimensions. Performance of FBO‐based design optimization is demonstrated using two examples of planar UWB antennas. Moreover, the computational cost of the approach is compared with conventional optimization driven by a pattern search algorithm. Experimental validation of the numerical results is also provided. 相似文献
108.
In this study, novel designs of single‐band and tri‐band pattern reconfigurable antennas are proposed. The design of single‐band pattern reconfigurable antenna is accomplished by the use of varactor diodes with the parasitic elements placed on both sides of the driven conventional printed dipole antenna. By tuning the capacitance of varactor, the antenna operates in four different configurations of radiation pattern which include bi‐directional end‐fire, broadside, and uni‐directional end‐fire radiation patterns. The tri‐band pattern reconfigurable antenna design is achieved by the use of parasitic elements on both sides of a tri‐band driven dipole antenna. Dual‐band LC resonators are used as loading elements along the arms of printed dipole to get two lower order modes in addition to the reference dipole mode, resulting in a triband operation of the driven element. The electrical lengths of the parasitic elements with respect to the tri‐band driven element are controlled by suitably embedding varactor and PIN diodes with them. The proposed tri‐band antenna operates in ten different configurations of radiation patterns in the three operating bands. Fully functional prototypes of single‐band and tri‐band pattern reconfigurable antennas along with the DC bias networks have been fabricated to validate the results obtained in simulation. 相似文献
109.
Tri‐band composite cylindrical dielectric resonator antenna with hybrid mode excitation and cross‐polarization suppression 下载免费PDF全文
This communication investigates composite cylindrical dielectric resonator antenna (CDRA) for various wireless applications. Three important features of proposed antenna design are (i) realization of two different hybrid modes, that is, HEM11δ and HEM12δ mode in CDRA with the help of modified annular ring printed line (work as both magnetic dipole and electric dipole), both the hybrid modes support broadside radiation characteristics (ii) suppression of HEM21δ mode, in order to reduce the cross‐polarization level in H‐plane of other hybrid modes (HEM11δ and HEM12δ mode) by an amount of 8‐10 dB (iii) creation of triple‐band attribute using the concept of composite antenna. The proposed antenna design has been fabricated and practically tested. Simulated outcomes show good agreement with measured outcomes. It works in three frequency bands, that is, 2.25‐2.79 GHz, 3.1‐4.0 GHz, and 5.05‐5.6 GHz. The designed antenna structure is appropriate for WLAN and WiMAX applications. 相似文献
110.
为了有效完成铁路沿线的安全监测,基于北斗警犬状态远程监测系统应运而生,目前存在着监测系统中天线受环境影响大、接收性能差等问题,针对上述问题设计了一种平面微带天线。本文以单支节调配器为主线,以应用角度出发,分别对其平面及馈线弯折等情况进行了仿真分析,克服铁路特殊环境北斗天线安装困难、频带窄易受干扰等缺点。采用ANSOFT HFSS软件进行天线性能仿真,仿真结果表明,设计的北斗天线有效中心频率为1571MHz,电压驻波比小于1.5,符合警犬状态远程监测的实际应用要求。 相似文献