基于k平面对圆极化微带天线馈源的确定

微带天线馈点的位置决定天线辐射波的模式和天线与馈线的匹配情况。本文以矩形微带天线形成圆极化波为研究对象,利用k平面相位关系,从理论上推导其馈电点的轨迹方程,通过编程确定其具体的馈电点,利用HFSS9.2仿真观察其S11曲线。     

Modeling of microstrip antennas using neural networks techniques: A review

Artificial neural networks modeling have recently acquired enormous importance in microwave community especially in analyzing and synthesizing of microstrip antennas (MSAs) due to their generalization and adaptability features. A trained neural model estimates response very fast, which is nearly equal to its measured and/or simulated counterpart. Thus, it completely bypasses the repetitive use of conventional models as these models need rediscretization for every minor changes in the geometry, which itself is a time‐consuming exercise. The purpose of this article is to review this emerging area comprehensively for both analyzing and synthesizing of the MSAs. During reviewing process, some untouched cases are also observed, which are essentially required to be resolved for antenna designers. Unique and efficient neural networks‐based solutions are suggested for these cases. The proposed neural approaches are validated by fabricating and characterizing of the prototypes too. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:747–757, 2015.     

Computer aided design algorithm for singly fed circularly polarized rectangular microstrip patch antennas

Based on a resonant cavity model, this work presents an effective computer aided design (CAD) algorithm to design singly fed circularly polarized (CP) rectangular microstrip patch antennas. The CAD algorithm allows precise prediction of the antenna performance. The analysis of radiation pattern, input impedance, and axial ratio parameters confirm the success of the design. The experimental results from a manufactured prototype operating at 2.25 GHz are in good agreement with the CAD predictions. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 32–41, 1999.     

Coaxial cavity waveguide antennas excited by stacked circular microstrip patches for use as prime‐focus reflector feeds

A coaxial cavity antenna excited by a stacked circular microstrip antenna is investigated as a feed for prime‐focus parabolic reflector antennas. The radiation pattern of the proposed cavity‐backed antenna is saddle shaped, which widens the ?10 dB beamwidths and increases the reflector efficiency especially for deep reflectors with small focal length‐to‐diameter ratios. With a single‐probe feed, the co‐polar radiation pattern is slightly asymmetric in the E‐plane, but is made symmetric by a differential feeding technique, using two probes. The impedance bandwidth of the proposed feed antenna is 20%. The antenna was fabricated and tested, and it exhibited good agreement between simulation and measurement results. The gain factor of the feed was also studied with a circular‐symmetric reflector and provided a gain factor of 79% at f/D = 0.375. This type of feed can be used as an alternative to conventional horn or waveguide feeds, where reduced size and light‐weight are desirable with added advantage of easy integration with electronics.     

Miniaturization and bandwidth enhancement of a cavity backed circular microstrip patch antenna

The resonant frequency of a circular patch antenna with and without circular cavity is measured. The patch miniaturization in the presence of the cavity is proved. Different methods of reducing resonant frequencies and broadening bandwidth without significantly reducing antenna gain are presented. Capacitively loaded patch and slits on the patch stimulate the patch at lower frequencies and multiple resonances, thus help miniaturization. Finally ferrite loading on the feed probe further increases the bandwidth without significantly reducing the antenna gain. The method is much more improved than that for a resistive loaded patch and a deformed patch. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Generalized design approach to compact wideband multi‐resonant patch antennas

In this work, a generalized design approach to compact, wideband multi‐resonant microstrip patch antenna is proposed. Theoretical criterion of the length of the prototype dipole is laid down based on the simplest dipole model and the associated eigenmodes at first. Then, the criterion is employed to reveal the general relationship between the prototype dipole length, operational modes, sizes, and radiation behaviors of the resultant multi‐resonant circular sector patch antennas. Next, a compact wideband, dual‐resonant circular sector patch antenna is designed accordingly. It is operating at the TM_3/4,1 and TM_9/4,1 modes within a 240° circular sector patch radiator with its radii short circuited. The antenna fabricated on a single‐layered air substrate exhibits an available radiation bandwidth of 25.0%, with a profile as small as 0.043 guided wavelength at the center frequency. It is evidently verified that the approach can be employed to realize compact, dual‐resonant wideband microstrip patch antennas without increasing antenna profile, inquiring multiple radiators or employing reactance compensation techniques. In addition, it may lead to a series of novel wideband patch antenna designs with diverse performances.     

一种宽频带四单元微带天线阵设计*

综合运用了H型缝隙耦合馈电技术和引入空气层技术展宽了天线的频带,设计出一个工作在Ku波段的宽频带微带天线单元并组成四单元阵列。该天线由两层介质板构成,并利用180°反相馈电抑制了高次模的耦合激励,降低了交叉极化电平。使用三维电磁场仿真软件(Ansoft HFSS)对微带天线进行仿真优化,仿真结果表明,天线单元性能良好,相对阻抗带宽(S11≤-10 dB)为8.5%,增益为8.05 dB。四单元天线阵列相对阻抗带宽(S11≤-10 dB)达到16.6%,增益为13.7 dB。天线阵列性能良好,设计方法具有很好的可扩展性。归纳总结出的介电常数计算式也具有普遍性。     

Analysis of microstrip antennas on finite chiral substrates

An approach is developed to analyze microstrip antennas on finite chiral substrates using the finite-element method (FEM). The perfectly matched layers (PMLs) in the chiral media is employed in this work. First, the characteristics of microstrip antennas on infinite conventional, ferrite, and chiral substrates are respectively analyzed in order to validate our analysis. Then microstrip antennas on finite chiral substrates are investigated as a comparison with those on infinite chiral substrates. Finally, the input impedances of microstrip antennas on infinite and finite chiral substrate are calculated. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 49–56, 2004.     

Matched feeds for offset reflector antenna using circular microstrip patch antenna

This article presents two designs of matched feed for an offset fed reflector. Circular microstrip patch antennas are used in the proposed designs. Both the matched feeds achieve conjugate field matching by generating TM₂₁ mode at an appropriate ratio to the fundamental TM₁₁ mode. The first matched feed generates the required dual mode field distributions using a dual layer stacked patch antenna. The second matched feed is a novel design using centered circular array with the central element generating the required TM₂₁ mode and the surrounding circular ring antenna elements operating in the TM₁₁ mode. Both the designs are studied analytically using cavity model and are implemented in High frequency System Simulator (HFSS) and Computer Simulation Technology (CST). The matched feed designs are investigated for an offset reflector with the projected diameter, D = 50λ, focal length, F = 30λ and clearance height, H = 5λ operating at 20 GHz. The secondary field patterns of the offset reflector fed by the matched feeds are evaluated numerically using a MATLAB code based on geometrical optics technique and verified by HFSS‐PO results. Offset reflector performance such as cross‐polarization, ?30 dB cross‐polar bandwidth, gain, and first side‐lobe level are investigated for the both matched feeds.     

Performance characterization of wideband,wide‐angle scan arrays of cavity‐backed U‐slot microstrip patch antennas

This work looks at the use of wideband cavity‐backed U‐slot microstrip antennas in finite phased arrays. This configuration retains the single‐patch and single‐layer characteristics of conventional microstrip antenna arrays and provides a good impedance matching over wider scan angles when electrically thick substrates are used to improve the frequency bandwidth. The characteristics of finite phased arrays of U‐slot rectangular microstrip patches enclosed in cylindrical cavities are analyzed from a validated hybrid methodology based on the finite element method, the modal analysis, and the properties of spherical waves. The results are compared with those obtained using an infinite array model. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Harmonics blocking in the inset fed microstrip patch antenna using cascaded defected microstrip structure

In this article a cascaded defected microstrip structures (CDMS) is proposed as the feed line of an inset patch microstrip antenna. Using this feed line, the effective radiation is improved; the higher order harmonics are completely suppressed, the size of antenna is about 10% reduced and also the front‐to‐back ratio parameter is greatly improved. In comparison to a conventional microstrip patch antenna without the CDMS, the radiated power of the CDMS patch antenna at harmonic frequencies even up to the 4th harmonic has been drastically decreased. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Aperture‐coupled microstrip antennas loaded with very high permittivity ceramics

The use of very high permittivity ceramic materials (εr = 38, 80) to miniaturize an aperture‐coupled microstrip patch antenna is reported in this article. A loss of the antenna gain in such a technique is observed, and then a novel substrate‐superstrate structure is developed to enhance the gain. The whole process of gain enhancement is analyzed by using the finite‐difference time‐domain (FDTD) method. The simulations are excellently correlated with the experiments. They validate that the loss of the antenna gain can be recovered up to that of conventional microstrip antennas loaded with low permittivity materials (εr < 3). In addition, the performance comparison of the aperture‐coupled microstrip antenna of very high permittivity with the probe‐fed microstrip antenna of very high permittivity is presented. It is shown that the aperture‐coupled antenna has wider impedance and radiation bandwidths than the probe‐fed one while keeping the antenna gain at about the same level. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 154–160, 2003.     

Analytic study on CP enhancement of millimeter wave DR and patch subarray antennas

This article presents a comparative analysis for the performance of single, 2 × 2, and 4 × 4 dielectric resonator (DR) and patch circularly polarized (CP) antenna subarrays at 30 GHz. In order to enhance the CP bandwidth, the subarray elements are fed by two kinds of sequential feeding techniques using parallel and hybrid ring feeds. The 4 × 4 patch antenna subarrays fed by parallel and hybrid ring feeding networks are fabricated and tested. Measurements show acceptable agreement with simulation results. The experimental results show a bandwidth of 36.9% for both (?10 dB) impedance matching and (3 dB) axial ratio CP patterns for the patch subarray antenna with hybrid ring feeding. For the parallel feeding, the corresponding bandwidth is 28.81%. The proposed antennas combine desirable features such as wide impedance and AR bandwidths, low profile, and easiness of fabrication and therefore is a good candidate for millimeter wave systems around 30 GHz.     

基于腔模理论对圆形微带天线的研究

在导体接地板的介质基片上贴加导体薄片而形成的天线是微带天线。本文基于腔模理论对圆形微带天线远区场的确定,在给定参数的条件下,通过仿真软件得到曲线。     

基于腔模理论对圆形微带天线的研究

在导体接地板的介质基片上贴加导体薄片而形成的天线是微带天线。本文基于腔模理论对圆形微带天线远区场的确定，在给定参数的条件下，通过仿真软件得到曲线。     

Computation of resonant frequency for equilateral triangular microstrip antennas using the adaptive neuro-fuzzy inference system

A new method based on the adaptive neuro-fuzzy inference system (ANFIS) for calculating the resonant frequency of the equilateral triangular microstrip patch antenna is presented. The ANFIS has the advantages of the expert knowledge of the fuzzy inference system and the learning capability of neural networks. A hybrid-learning algorithm, which combines the least-square method and the backpropagation algorithm, is used to identify the parameters of ANFIS. The results of the new method show better agreement with the experimental results, as compared to the results of previous methods available in the literature. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 134–143, 2004.     

Probe‐fed microstrip antennas loaded with very high‐permittivity ceramics

This article reports the feasibility study of miniaturizing probe‐fed microstrip patch antennas by dielectric loading. The loading materials are barium tetratitanate ceramics of very high dielectric constant (ε_r = 38, 80). It is shown that, simply through loading, the antenna sizes are greatly reduced; however, the antenna performances are deteriorated. For instance, the antenna gain becomes lower. Then enhancement of the antenna performances follows. A substrate–superstrate structure is used to recover the gain. Both the experiments and the finite‐difference time‐domain (FDTD) simulations demonstrate that the gain and impedance bandwidth can be retrieved such that they are comparable to those of conventional microstrip antennas loaded with low permittivity materials (ε_r < 3). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Design of wideband bandpass filter using short‐circuited circular patch resonator loaded with slots

This paper presents a wideband bandpass filter design based on a short‐circuited circular patch resonator with inductively loaded slots. The cavity model method is used to analyze the excited resonances of the resonator. According to the illustration of the cavity model, the TM₀₁₀ mode is excited as the fundamental mode, the resonant frequency of which is much lower than that of the TM₁₁₀ mode and can be further lowered by the loaded arc‐oriented slots. Therefore, the proposed resonator can be used to design a filter with compact size. In addition, one of the two orthogonal degenerate TM₁₁₀ modes can be independently tuned by the slot along the symmetric plane without affecting the TM₀₁₀ mode. Since the resonant frequency of each mode can be tuned independently by the parameters of the slots, and the coupling between resonant modes of the resonator and source/load can be adjusted by the feeding angle and the capacitive loaded stubs on the feeding lines, the center frequencies and bandwidths of the designed bandpass filters can be tuned easily. The analysis is theoretically and experimentally verified by two examples with good agreement between the simulated and measured results.     

High isolation dual‐frequency patch antenna integrated with cascade defected microstrip structure

This article presents a high‐isolation dual‐frequency rectangular patch antenna utilizing microstrip feed line integrated with a cascade defected microstrip structure (CDMS). Two types of CDMS are added, T‐shaped CDMS and Dumbbell‐T‐shaped CDMS. Simulation results show using these structures improve isolation up to 70 dB and reduce harmonic signals from transmitter. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

High performance microstrip monopole antenna with loaded metamaterial wire medium superstrate

A novel design of printed monopole antenna loaded with wire medium is developed for radar applications. The advocated design aims to simultaneously enhance the gain and bandwidth of the proposed geometry. The proposed antenna is composed of a circular patch etched with double C‐shaped slots and the ground is defected to achieve wide bandwidth. Wire medium superstrate and a metal reflector are implemented to provide high gain. The promising tunable wire medium superstrate consists of a periodic array of parallel metallic wires arranged in a rectangular pattern that mimic the behavior of epsilon‐near‐to‐zero (ENZ) metamaterial. This medium is suspended at a distance of a quarter‐wavelength in air above the antenna to provide the optimum gain and reduce the side lobes level. Prototype of the optimized antenna is fabricated using Rogers's substrate to offer ?10 dB bandwidth over the entire frequency range (900 MHz to 2.85 GHz). Details of the design process are investigated through full wave electromagnetic simulations performed by CST software. Experimental results of the fabricated prototype are presented and also compared with simulation results where an appreciable agreement between them is demonstrated.