Miniaturization of a patch antenna using circular reactive impedance substrate

In this article, to construct a reactive impedance substrate, unit ring is designed and proposed with radial and concentric mode analysis. A cylindrical substrate backed with a PEC plane and circular metallic elements on the top is used for achieving reactive surface impedance behavior. In this aspect, three unit rings structure with different ring elements are designed and simulated to realize the reflection phase characteristics. Afterwards, a probe‐fed circular patch antenna is miniaturized by stacking the three‐ring circular reactive impedance surface. The fundamental resonance frequency of the proposed antenna is reduced by about 30% with an improvement in impedance bandwidth by 121.6%. An improved front‐to‐back ratio as well as an acceptable co‐pol and cross‐pol isolation is exhibited in both E‐plane and H‐plane at the resonance frequency. In addition of miniaturization, dual band behavior has also been observed in the proposed design. Both resonance phenomena have been explained by circuit model representation and surface current distribution analysis. Improved radiation efficiency at 81.5% has been measured for the proposed antenna configuration.     

Modal analysis of probe‐fed circular sector microstrip antenna with and without variable air gap: Investigation with modified cavity model

Determination of accurate modal fields is one of the most crucial issues to understand the proper behavior of circular sector microstrip antennas (CSMAs) to achieve the best performance. In this article, dominant and higher order modal characteristics have been rigorously studied which germinate an improved, accurate, and efficient computer‐aided design (CAD) formulation to estimate the resonant frequency of CSMA with and without air gap between substrate and ground plane. The proposed formulation can address the wide variety of issues (such as substrate height, substrate permittivity, air gap height, higher order modes, etc.). The computed results were validated against the results obtained from high ‐ frequency structure simulator (HFSS) and our own experiments, while they have been also justified through the results obtained from the available literature.     

Serial‐feed for a circular patch antenna with circular polarization suitable for arrays

A compact sequential‐rotation array with serial feed and three probes using multi‐layer substrate is proposed. The most compact shape for the microstrip patches are selected with the optimization for the axial ratio and return loss bandwidth. The gain, return loss, and axial ratio bandwidths of the antenna are improved significantly by converting three patches to one circular. The patch radius and the position of probes are selected to form circular Poynting vectors around it where the maximum power is present at large frequency range. While the two layers of the structure use similar board this structure only uses a substrate and three simple pins. Also the total area of the antenna is limited to the microstrip patch and it has a straightforward fabrication steps. So the wideband antenna is relatively inexpensive and compact. The antenna has 21.4% 3 dB axial ratio bandwidth in simulation and 21.1% in fabrication. Consequently, the serial‐multi‐fed circular patch with unique angular and phase arrangements is suitable for many applications as the antenna arrays. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:529–535, 2014.     

宽频带高增益RFID微带天线阵设计

设计了一种宽频带高增益微带天线单元并组成了4元阵列。通过在普通矩形微带贴片加载2个对称切角、改变贴片表面电流分布实现天线单元的双频工作,调节切角尺寸使两个频点相互靠近融合,展宽频带。在此基础上确定合适的阵元间距,采用等副同向并联馈电,馈电网络由T型结功分器组成,并使用同轴探针馈电方式,实现天线阵列的设计。通过高频电磁结构仿真软件HFSS对天线进行仿真和优化,结果表明阵列天线性能良好。     

一种声表面波无线传感器的小型化微带天线

声表面波(SAW)无源无线传感器常用于检测复杂环境下的物理参数。本文针对SAW无线无源传感器天线对低轮廓、小尺寸天线的要求,同时采用短路加载技术和贴片开槽技术,设计了一款小型化的低轮廓微带天线,天线贴片尺寸仅为21.4*21.3mm2,高度仅1mm。测试结果表明,天线,在小型化、低轮廓与增益之间取得良好折中。利用制作的天线,实现了SAW无源无线传感器的检测。     

Circular microstrip antenna with off‐centered Y‐slot

A novel dual‐frequency broadband design of a single‐layer single‐feed circular microstrip antenna with an off‐centered Y‐slot is demonstrated in this communication. By selecting a suitable location of the Y‐slot in the circle, the proposed antenna on glass epoxy FR‐4 substrate not only resonates efficiently at two closely spaced frequencies (2.736 and 2.868 GHz) but also offers improved bandwidth (210 MHz or 7.5%) in comparison with a conventional circular microstrip patch antenna (～2%). From the measured results, almost identical broadside radiation patterns are obtained at two resonant frequencies, and the variation of less than 1 dBi in gain values is achieved in the frequency range where broadband behavior is observed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

A coplanar‐waveguide‐fed planar integrated cavity backed slotted antenna array using TE33 mode

This short communication presents a substrate integrated waveguide planar cavity slotted antenna array. The proposed antenna array, excited in its TE₃₃ higher mode, incorporates a grounded coplanar‐waveguide (CPW) CPW‐feeding excitation mechanism. The electromagnetic energy is coupled to the air through 3 × 3 slot array etched on top metallic layer. The proposed antenna operates in the X‐band for the frequency range around the 10 to 11 GHz with resonances at 10.4 and 10.8 GHz frequencies. The proposed antenna array was fabricated and tested. Experimental results show good impedance matching with enhanced radiation characteristics, in terms of peak gain, cross‐polarization level, and low back‐radiation. The proposed antenna has the advantages of low‐footprints, lightweight, high gain, low‐cost, and ease of integration with other electronic circuits. With these characteristics, the proposed antenna array can find its applications in compact wireless digital transceivers.     

A circular patch antenna with parasitic element for UHF RFID applications

This article initially proposes a directly‐fed circular patch antenna with L‐shaped ground plane for Radio Frequency Identification (RFID) applications in the 900 MHz (902?928 MHz) ultrahigh frequency (UHF) band. To achieve circularly polarized (CP) radiation, two arc‐shaped notches are loaded into the main patch. To enhance the CP bandwidth so that the proposed antenna can also cover the UHF RFID band for Europe (866?869 MHz), a parasitic element is printed besides the main patch. Experimental measurements show that the 10‐dB return loss bandwidth of the proposed antenna was 30.95% (833?1138 MHz) and its corresponding 3‐dB axial ratio bandwidth was 8.95% (865?946 MHz). Good gain and radiation efficiency of more than 7 dBic and 90%, respectively, were also exhibited across the two desired UHF RFID bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:681–687, 2015.     

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.     

Edge feeding of circular patch microstrip antennas

Edge feeding of a circular patch antenna by a microstrip line has been achieved by utilizing the circumferential variation of the field which is fixed by loading the patch. However, loading splits the degenerate modes and gives rise to cross‐polarization. Three different techniques are presented to analyze the loaded circular patch antenna. Comparison with the measured results for input impedance and radiation patterns shows good agreement. The concept used here is very general and can be applied to the edge feeding of any ring antenna. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 74–85, 2001.     

Eccentric annular slot patch antenna with frequency agility for UHF RFID reader applications

The design of a simple ultrahigh frequency RFID (radio frequency identification) reader antenna that can operate within the North America RFID band (902–928 MHz) is studied. To generate circular polarization (CP) radiation in this band, a novel method of loading two narrow open‐ended slots (slits) into an eccentric annular slot patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the radiating patch is loaded to an L‐shaped ground plane. From the experimental results, the proposed antenna can yield an impedance bandwidth (10‐dB return loss) between 650 MHz to 1125 MHz, while good CP bandwidth (3‐dB axial ratio, AR) from 901 MHz to 930 MHz is also attained. Furthermore, gain level and efficiency of more than 7.8 dBic and 90%, respectively, were also measured. By simply removing one of the slits, this proposed antenna can also be modified to operate within the China (840–846 MHz) and European (865–868 MHz) RFID band.     

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.     

一种高增益宽频带圆极化微带阵列天线的研制

针对微带天线阻抗匹配带宽一般较窄的自身缺陷,基于相控阵雷达天线的应用背景,设计了一种工作在X波段的双层圆极化微带天线结构,且优化发现,其各电磁参数良好。为提高其增益,还在此基础上设计并最终制作了双层2×2结构的微带天线阵列,其实测性能与设计值相符,增益达到10.7dB,带宽1.2GHz,相应轴比为4dB,符合圆极化要求。     

Gain and isolation enhancement of patch antenna using L‐slotted mushroom electromagnetic bandgap

In this paper, the application of the L‐slotted mushroom electromagnetic bandgap (LMEBG) structure to patch antenna and antenna array is investigated. A coaxial fed patch antenna and antenna array are designed at 5.8 GHz, center frequency for ISM band (5.725‐5.875 GHz). Two layers of LMEBG are placed around the patch to achieve a gain enhancement of 1.9 dB. Measured results show a bandwidth enhancement of 300 MHz with an additional resonant frequency at 5.6 GHz with 4.5 dB of gain. A 5 × 2 array of LMEBG is used to achieve a 2 dB mutual coupling reduction and 2 dB gain enhancement for a two‐element H‐coupled patch antenna array.     

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.     

A compact monopolar patch antenna with bandwidth‐enhancement under dual‐mode resonance

A compact monopolar microstrip patch antenna (MPA) with enhanced‐bandwidth is proposed. In order to achieve the miniaturized patch, the zeroth‐order mode of the MPA instead of its higher‐order modes is employed at first by loading the shorting pin around the center of the patch. After that, a L‐shaped microstrip line with a shorting pin is introduced at the periphery of the patch radiator to excite an additional non‐radiative mode for bandwidth enhancement. In final, the proposed MPA is fabricated and measured. The results illustrate that the antenna generates an enhanced‐bandwidth of about 4.1% ranging from 2.39 to 2.49 GHz, which is significantly larger than that of the traditional MPA around 1%. Meanwhile, the dimensions of the radiating patch are obviously decreased down due to the employment of zeroth‐order mode, which are kept as small as about 0.17 λ₀ × 0.22 λ₀ × 0.026 λ₀ (λ₀ is the free‐space wavelength).     

Circularly polarized rectangular dielectric resonator antenna fed by a cross aperture coupled spiral microstrip line

In this article, a circularly polarized rectangular dielectric resonator antenna fed by a cross‐aperture coupled spiral microstrip line is investigated. A quarter wavelength section of microstrip line is positioned between each arm of the cross slot in a spiral form to generate the circular polarization. The prototype of proposed antenna is fabricated and tested. The measured |S₁₁| and 3‐dB axial ratio frequency range is 31.74%, (2.65–3.65) GHz and 20%, (3.12–3.74) GHz, respectively and the measured total gain and left handed circularly polarized gain are 4.5 and 3.1 dB, respectively. The proposed antenna may be suitable for WiMAX applications.     

Miniaturization of patch antenna based on hybrid topology optimization

A hybrid topology optimization method that combines the scalar isotropic material with penalization and the level set method is utilized to achieve the miniaturization of patch antennas while maintaining good radiation and polarization characteristics. In order to achieve this goal, the Heaviside projection filter is applied to obtain topologies that are more complex. Both the radiation power and the reflection coefficient of the antenna are utilized as sub‐objectives. Besides, by setting the radiation patch to be symmetrical, not only the numbers of optimization variables and optimization sub‐objectives are reduced, but also the cross‐polarization level is suppressed effectively, so that the optimization is accelerated. The optimized patch antenna achieves good performance in patch size, impedance matching, radiation pattern, gain, and polarization characteristics. Compared with the reference patch antenna, the patch size of the optimized antenna is reduced by 63%, while the maximum realized gain and efficiency remain basically unchanged, achieving more than 5.9 dBi and 90%, respectively. Due to its very small size patch, the antenna is particularly suitable for compact multi‐antenna and antenna array applications.     

一种宽频带双圆极化微带天线阵列设计

为支撑海量数据传输与宽带无线通信系统需求,提出了一款宽频带双圆极化微带天线。采用微带天线作为基本辐射单元,基于层叠寄生贴片方式与加载空气腔方法展宽天线工作带宽并提高增益值,利用电容加载的三分支线定向耦合器对天线单元进行馈电进一步展宽天线带宽,并实现双圆极化辐射特性。单元电性能仿真结果良好,阻抗与轴比相对带宽达27.9%,峰值增益达到5.6dBi。基于辐射单元进行4×4阵列组合,所设计阵列天线阻抗带宽覆盖7.2 ~ 9.4 GHz,同一单元不同极化与不同单元间端口间隔离度均 ≥ 15 dB,轴比在通带内均 ≤ 3 dB,方向图仿真与测试结果吻合良好,验证了设计方案的正确性。     

A miniaturized patch antenna with enhanced bandwidth by using reactive impedance surface ground and coplanar parasitic patches

In this article, a miniaturized hybrid patch antenna is proposed that shows improved matching bandwidth and almost invariant radiation patterns. This antenna consists of a driven patch, reactive impedance surface (RIS) based ground plane in addition to the coplanar parasitic patches. The simulated and measured results show that the proposed antenna offers fractional bandwidth of 28% (S₁₁ = ?10 dB, from 2.38 GHz to 3.18 GHz). When this antenna operates at 2.38 GHz, 2.68 GHz, 2.98 GHz, and 3.18 GHz, shows realized gain of 6.46 dBi, 6.69 dBi, 7.84 dBi, and 7.59 dBi, whereas the front‐to back (F/B) ratio is 15.62 dB, 20.15 dB, 20.67 dB and 20.92 dB, respectively. The pattern quality is very consistent over the matching bandwidth. Compared to the conventional patch antenna, dimension of the hybrid patch antenna has decreased by about 36%.