Design of a broadband planar cavity-backed circular patch antenna

This paper presents a design of a low-profile cavity-backed circular patch antenna for broadband applications. By using substrate integrated waveguide (SIW) based cavity and feeding mechanism, a planar cavity-backed patch antenna is realized. The proposed study demonstrates that a wide impedance bandwidth can be achieved by employing a rectangular SIW-based cavity underneath the conventional circular patch. Additionally, to generate circular polarization (CP), the patch has been reduced diagonally and shorted by a via-probe. Finally, a CP SIW-based antenna is designed and operating for a wide impedance bandwidth of 23.10% below −10 dB criteria, ranging from 9.09 GHz to 11.40 GHz and axial-ratio (AR) bandwidth of 270 MHz (10.30–10.57 GHz). The proposed design is fabricated by means of a printed circuit board (PCB) procedure. The simulated results are validated with the experimental one which agrees well with each other in the terms of S₁₁, antenna gain, AR and radiation patterns. Moreover, the proposed design exhibits unidirectional radiation characteristics with the measured peak gain of 6.6 dBic while maintaining planar integration.     

A broadband circularly polarized cavity-backed Archimedean spiral array antenna for C-band applications

In this letter, a new configuration of sequentially rotated circularly polarized (CP) array antenna with a modified gain is investigated. In order to realize the presented antenna, four Archimedean spiral radiators are applied on a substrate, backed by a circularly slotted ground plane. Also a combination of 180° rat-race coupler and 90° branch-line couplers prepare the employed feeding network in this study. Furthermore, cavity-backed structure is utilized to enhance the antenna gain and achieve a directional radiation pattern over the operating frequency band. This configuration also extends the return loss (RL) and the axial ratio (AR) bandwidths, simultaneously. According to the experimental results, the 2 × 2 CP array antenna has RL bandwidth of 64.28%, AR bandwidth of 54.28%, and peak gain of 10.84 dBic. The close correspondence between the measured and the simulated results validates the proposed design.     

A systematic design method to obtain broadband characteristics for singly-fed electromagnetically coupled patch antennas for circular polarization

We present a systematic, empirical design technique to obtain optimum broadband impedance, axial-ratio (AR) and gain bandwidths for a singly-fed electromagnetically coupled patch antenna for circular polarization. Our investigation has also revealed tradeoffs amongst obtainable AR, impedance bandwidth and AR bandwidth. Using two design examples at different frequency bands and for different senses of circular polarization, we have demonstrated the effectiveness of the proposed knowledge-based tuning method. We have obtained at C-band measured values of impedance bandwidth (VSWR/spl les/2) equal to 43%, 3-dB AR bandwidth of 8%, AR of less than 0.3 dB and a mean gain level of 7 dB. For the Ku-band element, a 40% impedance bandwidth and a 17.3% of 3-dB AR bandwidth have been obtained with a peak gain of 7.2 dBic.     

小型化缝隙加载圆极化及宽带微带贴片天线设计

提出了一种十字形缝隙加载的小型宽带及圆极化微带贴片天线的设计方法。该天线通过在方形贴片上加载一个大尺寸的十字形缝隙实现天线的尺寸缩减,介质基片采用由FR4和空气层组成的层叠结构,在缝隙中嵌入L型枝节,只需通过调整枝节上同轴线馈电点的位置来获得圆极化或宽带阻抗匹配。ANSYS HFSS仿真分析表明,天线的圆极化带宽（AR≤3 dB）为1.7%,阻抗带宽（VSWR≤2）为5.8%,天线在宽带范围内具有稳定的增益,峰值增益为7.8 dB,同时贴片面积缩减了52.3%。改变馈电点的位置可调节两个谐振频率使天线阻抗带宽达到9.4%,比传统的微带贴片天线阻抗带宽提高了114%。     

Investigation of circularly polarized loop antennas with a parasitic element for bandwidth enhancement

It is demonstrated that the bandwidth of circular polarization (CP) can be significantly increased when one more parasitic loop is added inside the original loop. A single-loop antenna has only one minimum axial ratio (AR) point while the two-loop antenna can create two minimum AR points. An appropriate combination of the two minimum AR points results in a significant enhancement for the CP bandwidth. A comprehensive study of the new type of broad-band circularly polarized antennas is presented. Several loop configurations, including a circular loop, a rhombic loop, and a dual rhombic loop with a series feed and a parallel feed, are investigated. The AR (/spl les/2 dB) bandwidth of the circular-loop antenna with a parasitic circular loop is found to be 20%, more than three times the AR bandwidth of a single loop. For the rhombic-loop antenna with a parasitic rhombic loop, an AR bandwidth (AR/spl les/2dB) of more than 40% can be achieved by changing the rhombus vertex angle. The AR (/spl les/2 dB) bandwidths of the series-fed and parallel-fed dual rhombic-loop antennas with a parasitic element are 30% and 50%, respectively. A broad-band balun is incorporated into the series-fed dual rhombic-loop antenna for impedance matching. The broad-band CP performance of the loop antennas is verified by experimental results.     

Broadband proximity fed ring microstrip antenna arrays

Various gap-coupled array configurations of ring microstrip antennas and rectangular slot cut ring microstrip antennas with proximity fed slot cut ring microstrip antenna for larger bandwidth and gain are proposed. The rectangular slot in ring patch reduces its orthogonal TM₀₁ and TM₀₂ mode resonance frequencies and along with TM₁₀ modes of fed and parasitic ring patches, yields broadband response. The gap-coupled configuration with ring patch and slot cut ring patch yields bandwidth of nearly 430 MHz with broadside radiation pattern and peak gain of more than 9 dBi. By gap-coupling ring patches along all the edges of proximity fed pair of slot cut ring patch, a 3 × 3 ring microstrip antenna array is realized. It yields bandwidth of more than 460 MHz with peak gain of more than 10 dBi. To further improve upon the bandwidth, a 3 × 3 array of ring patches in which rectangular slot is first cut on the edges of ring patch which are gap-coupled along x-axis and further cut inside the patches which are gap-coupled along x and diagonal axes, is proposed. Both of these configurations yield bandwidth of more than 500 MHz (>45%) with a peak gain of around 10 dBi.     

A novel wideband and circularly polarized cross‐dipole antenna

In this paper, we present a novel wideband circularly polarized (CP) composite, called cavity‐backed crossed dipole antenna for 2.45 GHz industrial, scientific, and medical (ISM) band wireless communication. To excite the CP radiation effectively, a curved‐delay line providing an orthogonal phase difference among the cross‐dipole elements is attached at corners of the sequentially rotated elements. By choosing a proper radius of the curved‐delay line, a wide input impedance of the antenna can be realized. Unlike conventional cross‐dipole antennas, the proposed cross‐dipole antenna is designed with an open stub added to the radiating arms of the dipole so that both impedance and axial ratio bandwidths are enhanced. The antenna is center‐fed by a 50‐Ω coaxial cable and is placed above a cavity‐backed reflector to obtain a directional CP radiation pattern. With the advantage of being center‐fed, a symmetric CP radiation pattern can be achieved across the entire operating bandwidth. To further improve the directivity and the radiation pattern, a rectangular cavity‐backed reflector is used. Simulated and measured results confirm that the proposed antenna has good CP characteristics. The proposed antenna obtains a broad 3‐dB axial ratio bandwidth of 49% (1.20 GHz, 1.96–3.16 GHz) and an impedance bandwidth of 67.7% (1.66 GHz, 1.69–3.35 GHz) for reflection coefficient (S₁₁) ≦ −10 dB. It also yields an average CP gain of 9.2 dBic across the operating bandwidth and a peak CP gain of 10 dBic. Copyright © 2016 John Wiley & Sons, Ltd.     

Design and Analysis of Dual-band Circularly Polarized Hybrid Ring Cylindrical Dielectric Resonator Antenna for Wireless Applications in C and X-Band

This article presents a dual-band circularly polarized hybrid ring CDRA (Cylindrical dielectric resonator antenna) for wireless applications in C and X-band. A circular ring inclusive of a slotted cross-shaped microstrip feed line is used to excite the ring CDRA and generation of HEM_11δ and TEM_01δ modes. Multiple inverted Z-shaped apertures and circular ring along with a slotted cross-shaped microstrip feed line are responsible for the generated circular polarization wave between 3.92 and 4.08 GHz in lower band and 8.85 to 9.61 GHz in upper band with 4% (160 MHz) and 8.23% (760 MHz) axial ratio bandwidth (ARBW) respectively. The proposed antenna also offers impedance bandwidth of 20.58% (780 MHz) between 3.40 and 4.18 GHz in lower band while 29.31% (2490 MHz) between 7.25 and 9.74 GHz in upper band resonating at 3.73 and 7.79 GHz with???26.4 and???35.61 dB return loss respectively. The proposed ring CDRA shows stable gain of peak value 5.8 dB (simulated) and 5.8 dB (measured) in lower band while 7.7 dB (simulated) and 8.2 dB (measured) in upper band.

     

Broadband circularly polarized CPW-fed slot antenna array for millimeter wave application

A broadband and circularly polarized 1×4 linear antenna array composed of CPW-fed slot elements for millimeter wave application is discussed. Through a special short-circuiting stub perturbation method, the circular ring slot element achieves circular polarization and a broad bandwidth. Through a parallel feeding network, the array achieves a broad impedance bandwidth of 19% with VSWR?2 and CP bandwidth of 18.4% with AR?3 dB and has a peak gain of about 6.8 dB.     

Wideband GNSS antenna covered by a double-sided metasurface

A novel global navigation satellite system (GNSS) antenna that employs a double-sided metasurface (MS) to cover a circularly slotted patch antenna is presented. With this MS, the antenna has a wide −10-dB reflection coefficient bandwidth from 1.160 GHz to 1.640 GHz (34.3%) and 3-dB axial ratio (AR) bandwidth from 1.170 GHz to 1.720 GHz (38.1%), covering all frequency bands of the GNSSs within a single band. Meanwhile, the right-handed circular polarization (RHCP) gain of the antenna is enhanced by the MS, with a peak value of 6.44 dBic at 1.600 GHz. An electrically small footprint of 0.364 λ₀ × 0.364 λ₀ is also achieved by the antenna at the operating frequency of 1.170 GHz.     

Dual-polarised single-layer slotted patch antenna

A compact design of the single-layer slotted microstrip patch antenna is presented, which has two highly decoupled orthogonal input ports and is capable of generating dual-polarised radiation. The proposed antenna displays a desired characteristic for reducing polarisation loss between the transmitting and receiving antenna units at arbitrary angles. The measured results show that the proposed antenna with resonance frequency at 5.93 GHz has a bandwidth of about 300 MHz, an average gain of greater than 8 dBi, and an input isolation of exceeding 20 dB for the entire impedance bandwidths of the two polarisations.     

基于北斗卫星导航系统的一种圆极化微带天线

介绍一种用于北斗卫星导航系统的圆极化微带天线。该天线的主辐射器由开槽的圆形贴片构成,采用单点的同轴馈电,设计的中心工作频率为2．492GHz。仿真结果显示,调节圆形贴片中开槽的长度,可以分离出简并模,激励两个正交的模式,当两个分量相位为90deg,可以实现圆极化。实际测试中,｜S11｜于-10dB的阻抗带宽为0．09GHz,3dB轴比带宽为0．033GHz,与仿真结果基本吻合。     

Circularly polarized antenna array with a new sequential phase feed network utilizing directional coupler

This is a presentation of a new design of circularly polarized (CP) antenna array having a wide axial ratio (AR) bandwidth and high-gain. It uses an innovative feed network which consists of compact directional couplers and a delay line describing a new kind of sequential phase (SP) feed network. Furthermore, in this work, we report and discuss the features of the feed network and single element. In the following, the single element antenna and the 2 × 2 CP antenna array are designed, prototyped and tested. The antenna array is designed by a multilayer microstrip structure with a compact size of 75 × 52 mm². Moreover, a metal reflector is utilized to enhance the antenna gain and achieve a unidirectional radiation pattern over the operating frequency band. According to the experimental results, the CP antenna array has a return loss (RL) bandwidth of 2.42 GHz (5.83–8.25 GHz), AR bandwidth of 1.11 GHz (6.76–7.87 GHz), and peak gain of 12.15 dBic. It seems that the performance of the proposed design is admirable for C-band frequency.     

Wideband Circularly Polarized Patch Antenna Using Broadband Baluns

A novel 90deg broadband balun comprising a broadband 90deg Schiffman phase shifter is introduced as a means of enhancing the wideband circular polarization performance of dual-fed type microstrip antennas. The proposed 90deg broadband balun delivers good impedance matching, balanced power splitting and consistent 90deg (plusmn5deg) phase shifting, across a wide bandwidth (~57.5%). A circular patch antenna utilizing the proposed 90deg broadband balun is shown to attain measured impedance(S₁₁< -10 dB) and axial ratio (AR < 3 dB) bandwidths of 60.24% and 37.7%, respectively, for the dual L-probe case; and 71.28% and 81.6% respectively, for the quadruple L-probe case.     

A new triple proximity-fed circularly polarized microstrip antenna

A novel circularly polarized microstrip antenna using triple proximity-fed method is proposed in this paper. The circular polarization radiation is produced by adjusting 120° phase shift between the feeds. In the feeding network, a three-way circular-sector power divider is adopted to distribute the current equally to each feed. A method of moments is employed for optimizing the design and achieving a good circular polarization at the center frequency of 1.28 GHz. The measured result shows that 3-dB axial ratio bandwidth and maximum gain are about 0.68% (8.7 MHz) and 7.11 dBic, respectively, which are consistent with the simulated values of 0.70% (9.0 MHz) and 7.21 dBic. The narrow bandwidth and reasonable gain indicate that this antenna is promising for various applications in L-band.     

A High‐Gain Microstrip Patch Array Antenna Using a Superstrate Layer

A dielectric superstrate layer above a microstrip patch antenna has remarkable effects on its gain and resonant characteristics. This paper experimentally investigates the effect of a superstrate layer for high gain on microstrip patch antennas. We measured the gain of antennas with and without a superstrate and found that the gain of a single patch with a superstrate was enhanced by about 4 dBi over the one without a superstrate at 12 GHz. The impedance bandwidths of a single patch with and without a superstrate for VSWR < 2 were above 11%. The designed 2×8 array antenna using a superstrate had a high gain of over 22.5 dB and a wide impedance bandwidth of over 17%.     

Compact dual-band patch antenna using spiral shaped electromagnetic bandgap structures for high speed wireless networks

This paper presents a compact dual-band slot antenna for 1.8/2.4 GHz WLAN applications using electromagnetic bandgap (EBG) structures. The slotted rectangular radiating element is surrounded by a spiral-like EBG. The antenna size is very compact (60 mm × 60 mm × 3.27 mm), and can be integrated easily with other RF front-end circuits. The working frequency of the patch antenna falls inside the EBG which will lead to the suppression of the surface waves. It is demonstrated that the proposed antenna can completely cover the required bandwidths of IEEE 802.11b/g and IEEE 802.11a with satisfactory radiation characteristics. The simulation is carried out using the finite integration time domain method (FITD) analysis technique. The EM simulated return loss, gain, directivity, radiation pattern, antenna efficiency and VSWR are presented for proposed antenna array. Good agreement is achieved between the simulated and measured results.     

E-shaped patch with reactive impedance surface for high gain and broadband circularly polarized antenna

A low-profile circularly polarized (CP) antenna with high gain and broad bandwidth is aimed at 5-GHz Wi-Fi applications using a symmetrical E-shaped patch. Initially, the radiating element is modeled as a symmetrical E-shape. An array of 4 × 4 rectangular patches are arranged periodically to make up a reactive impedance surface (RIS) structure. Furthermore, the RIS structure is deployed in the middle of a symmetrical E-shaped radiating patch and a perfect electric conductor (PEC) ground plane. As a result, the broadband CP is achieved with high gain. The above-mentioned combinations have achieved a −10-dB reflection coefficient bandwidth of 21.4% (4.92–6.1 GHz) and a 3-dB axial ratio (AR) bandwidth of 15.5% (5.25–6.1 GHz), and the antenna has attained a gain of 7.45–7.53 dBic.     

一款UHF 波段小型化RFID 天线的设计

随着太赫兹成像技术的快速发展,太赫兹成像研究过程中对测试系统提出了大带宽、高性能、通用性强及使用灵活性高等要求,针对这一需求,提出了用通用测试仪器构建太赫兹成像系统的思路:充分利用了通用仪器频率覆盖宽、指标高、通用性强等特点,使得构建的系统指标更高;充分利用了毫米波扩频模块的标准化、模块化设计思路,可实现成像系统测试频段的灵活更换。利用构建的成像系统进行的成像试验结果验证了方法的可行性,能够满足太赫兹成像研究人员快捷方便构建高性能成像系统的要求。     

一种应用于三频GPS的宽频带单馈电天线设计

为了实现全球定位系统（global positioning system,GPS）天线小型化并提高其性能,提出了一种新型的三频段GPS宽频带单馈电背腔天线,可在1176.45 MHz（L5）、1227.60 MHz（L2）和1575.42 MHz（L1）三个GPS频段下工作。通过在一端馈送交叉型行波天线并在另一端添加负载,来实现提出天线的右旋圆极化（right-hand circular polarization,RHCP）,且配有弯折线散热器。天线尺寸仅为120×120×29 mm3。仿真和实际测量结果显示,提出的单馈电天线无需使用复杂的馈电网络或双馈结构便可提供宽阻抗带宽（VSWR<2）、低轴比（AR）（<2 dB）和高RHCP增益（>4 dBic）。