A microstrip antenna design with multislots embedded into the ground plane for circular polarization

A single probe‐fed square microstrip antenna with two pairs of asymmetric narrow slots loaded into the ground plane for circular polarization (CP) is studied. To allow a simple fine tuning CP mechanism, the method of loading an additional square slot into the center of the ground plane is introduced into this proposed antenna. By tuning the overall‐size of this center square slot, the CP frequency can be easily tuned with minor effects on the CP performances. Furthermore, good axial ratio (AR) value of around 0.5 is also measured at 1575 MHz, which is suitable for GPS operation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2013.     

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。     

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。     

Varactor controlled frequency and polarization reconfigurable microstrip antenna

A single feed compact microstrip antenna achieving frequency and polarization diversity using a varactor is presented. A simple patch antenna with an X‐slot constitutes the fundamental structure. The frequency and polarization agility is realized by varying the reactance of an embedded varactor at the center of the X‐slot with respect to the biasing from 0 to 25 V. The prototype fabricated on a substrate of dielectric constant (ε_r) 4.4 and height (h) 1.6 mm is fed by a proximity feed fabricated using the same substrate. By controlling the bias voltage of the varactor, the polarization of the antenna can be switched between linear and circular polarization. Furthermore, the proposed antenna offers stable broadside radiation characteristics without any extra impedance matching circuit. The frequency and polarization diversities of this design could potentially improve the reliability of wireless communication systems. The details of the antenna are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2011.     

A dual circular‐slot microstrip antenna for GPS application

A novel single probe‐fed circularly polarized (CP) microstrip antenna design for global positioning system application is proposed. To achieve good CP radiation at 1575 MHz, two circular slots of dissimilar sizes are embedded separately into the radiating element and the ground plane. This CP design possesses the advantages such as simple in structure, uncomplicated fine‐tuning technique, and ease in manufacturing tolerances. Parametric studies via simulation are carried out to comprehend the vital parameters that will affect the impedance matching and frequency of the CP radiation. Prototypes of the proposed antenna have been constructed and experimentally studied. The measured results show a 10‐dB bandwidth and 3‐dB axial ratio bandwidth of 2.28 and 0.89%, respectively. Furthermore, stable gain variation at around 3.6 dBic is also observed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

An off‐center‐fed compact wideband antenna with truncated corners and parasitic patches for circular polarization

A novel single‐fed circularly polarized wideband, compact and lightweight microstrip patch antenna (MPA) is proposed. The antenna is designed in a simple two‐phase procedure to achieve wideband and circular polarization. In the first phase, an off‐centered L‐shaped feeding arrangement is employed to obtain wideband (|S₁₁| < ?10 dB) over 10.6 GHz to 14.7 GHz with an improved peak gain of 5.25 dBi. In the second phase, the radiating patch is symmetrically truncated and two modified‐parasitic patches are added to ensure <3 dB axial ratio over 11.4 GHz to 12.8 GHz. A prototype has been fabricated and the measured results show close agreement with the simulation. The proposed antenna is suitable for fixed satellite and broadcast satellite communication in Ku‐band range.     

Cross‐polarization reduction of microstrip antenna using microwave absorbers

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.     

X波段的圆极化微带共形阵天线的仿真与设计

为了满足X频段机载雷达天线的指标要求,使得矩形平面天线与柱面共形,通过并联侧馈方式进行馈电。在微带共形阵天线的相关理论基础上,阵元采用介电常数2.2,厚度为0.5mm的介质基板。通过HFSS12对微带共形阵天线进行仿真设计并优化。实验结果表明,在X波段内实现了方位面的全向扫描,实测阻抗带宽为9.80-10.20GHz,最大增益可达10dB,全向辐射性能稳定,满足了指标要求。     

基于零折射率超材料的高定向性微带天线

研究了一种基于平面网格状零折射率超材料的高定向性微带天线.利用超材料结构的平均效应实现了在10.24 GHz处介电常数为零,进而实现了超材料的折射率为零.实验结果表明,利用零折射率超材料对波束产生汇聚作用,使微带天线的定向性明显增强,E面、H面半功率波束宽度分别收缩了56.67°和26.60.,侧向辐射明显减弱,天线的...     

A high‐gain compact circularly polarized microstrip array antenna with simplified feed network

A broadband high‐gain circularly polarized (CP) microstrip antenna operating in X band is proposed. The circular polarization property is achieved by rotating four narrow band linearly polarized (LP) microstrip patch elements in sequence. Since the conventional series‐parallel feed network is not conducive to the miniaturization of the array, a corresponding simplified feed network is designed to realize the four‐way equal power division and sequential 90° phase shift. With this feed network, the impedance bandwidth (IBW) of the CP array is greatly improved compared with that of the LP element, while maintaining a miniaturized size. Then, parasitic patches are introduced to enhance the axial ratio bandwidth (ARBW). A prototype of this antenna is fabricated and tested. The size of proposed antenna is 0.93λ₀ × 0.93λ₀ × 0.017λ₀ (λ₀ denotes the space wavelength corresponding to the center frequency 10.4 GHz). The measured 10‐dB IBW and 3‐dB ARBW are 13.6% (9.8‐11.23 GHz), 11.2% (9.9‐11.07 GHz) respectively, and peak gain in the overlapping band is 9.8 dBi.     

Offset‐fed trapezoidal monopole antenna for broadband circular polarization

A novel broadband circularly polarized monopole antenna consisting of an isosceles trapezoidal monopole antenna which is offset fed by a microstrip line is presented. By choosing an appropriate offset, it is possible to establish two orthogonal current components that are out of phase by 90° and thus producing circular polarization. The axial ratio bandwidth of the proposed antenna has been further increased by adding a vertical slot parallel to the microstrip feed line. The measured results show that the proposed antenna has a 34.57% (1.89 GHz to 2.68 GHz) 3 dB axial ratio bandwidth. The ?10 dB reflection coefficient bandwidth is 122.53% (1.04 GHz to 4.33 GHz). The advantages of the proposed antenna are simplicity and a broad 3 dB axial ratio bandwidth.     

Stacked rectangular dielectric resonator antenna with different volumes for wideband circular polarization coupled with step‐shaped conformal strip

This paper presents a wideband circularly polarized broadside radiation characteristics by using stacked rectangular dielectric resonator antenna (DRA) with different volumes. In this designed antenna, the wide input impedance‐ and axial ratio (AR)‐bandwidths come from three factors: stacked rectangular DR with different volumes, stepped‐shaped conformal strip associated with microstrip line as a feed and different type of partial ground plane. Here, the orthogonal TE^x_δ11 and TE^y_1δ1 modes have been responsible for the generation of CP radiation in stacked rectangular DRA. Measured results show that the proposed stacked rectangular DRA with different volumes achieves input impedance bandwidth of 54.84% while AR bandwidth has been found to be 11.53%. The proposed antenna provides broadside right‐handed CP radiation pattern with gain ranges from 2.27–5.80 dBic and offers an average radiation efficiency of 89.48%, across the entire working bandwidth, respectively. Therefore, this antenna is very much useful for the ISM 2400 band applications.     

Double triangular monopole‐like antenna with reconfigurable single/dual‐wideband circular polarization

A polarization and frequency reconfigurable circularly polarized (CP) antenna is proposed based on a novel bilateral switching mechanism. Two triangular monopole antennas are connected to each other in an L‐shaped form by a narrow link to produce a CP operation. In the proposed technique, 4 PIN‐diode‐based switches are designed with desired insertion loss and isolation, and only 2 DC‐voltage controllers. These switches are located on the links and the feed lines to realize a polarization reconfigurable feature including both right‐hand CP (RHCP) and left‐hand CP (LHCP) modes. Moreover, 2 CP states, a single wideband operation and a dual‐band operation, can be supported by this mechanism. In a special performance of the switches, CP reconfigurability can be obtained in a narrow‐band mode around 2.45 GHz. Two general simulations are performed based on the simple microstrip links and a diode‐circuit model. The measured results exhibit a wide overlapped bandwidth (AR < 3 dB and VSWR < 2) of 44.4% (1.63–2.56 GHz) with a peak gain of 2.88 dBi in the first state and 5.5% (1.22～1.29GHz) and 20.6% (2.12–2.61 GHz) with the peak gains of 0.52 and 3.0 dBi in the second state, respectively. A wide beamwidth is obtained more than 75°. This work is appropriate for L‐ and S‐band CP diversity applications.     

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.     

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.     

Water dense dielectric patch antenna with wide-band and circular polarization reconfigurability

A wide-band circularly polarized reconfigurable antenna based on a pure water dielectric patch antenna is proposed. By changing the shape of pure water in the plexiglass container symmetrically, the circularly polarized states of the antenna can be switched. And the available bandwidth of right-hand circular polarization and left-hand circular polarization remain unchanged. The interface between pure water and air with a great difference in relative dielectric constant is equivalent to an electrical wall. When feed with an L-shaped metallic probe, the axial ratio of a wide band can be formed, and the impedance bandwidth of antenna can be fully utilized. Under the two circularly polarized states of the antenna, the measured results show that the 3-dB axial ratio bandwidth is above 24.4% for |S₁₁| < ? 10 dB, the radiation efficiency is concentrated at 58%–71%, and the maximum gain reaches 3.5 dBi.     

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.     

A wideband polarization reconfigurable isosceles trapezoidal monopole antenna

In this article, a polarization reconfigurable isosceles trapezoidal monopole antenna for the circular polarization (CP) is presented. A trapezoidal monopole and the ground plane are on the same side of the dielectric substrate. The monopole is excited by a reconfigurable T‐shaped 50 Ω microstrip feed line and reconfigurable vertical slots are incorporated in the ground plane to realize switchable wideband CP. For the different switching states of the p‐i‐n diodes, linear polarization, left‐handed and right handed CP can be achieved in the boresight direction (+z direction). The antenna prototype is fabricated and tested. The measured reflection coefficient bandwidth (|S11| < ?10 dB) is 31.2% (2.13 ‐ 2.91 GHz) and axial ratio bandwidth (axial ratio < 3 dB) is 22% (2.18 ‐ 2.72 GHz) for the CP. The measured reflection coefficient bandwidth is 18.56% (2.15 ‐ 2.59 GHz) for linear polarization.     

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.     

Analysis and design of dual‐polarized microstrip antenna array

A new dual‐polarized microstrip antenna array is presented. Diagonal feeding of the square patch with two ports is proposed to obtain dual linear polarization. A novel coplanar feedline network is also presented for the dual‐polarized array. For engineering purposes, a CAD‐oriented method of analysis is developed. The measured results demonstrate high isolation between the two input ports. The array has simple structure and is easy to further combine to form larger coplanar arrays. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 42–48, 1999.