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.     

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.     

Low‐cost broadband microstrip antenna array for 24 GHz FMCW radar applications

Two designs of microstrip antenna arrays consisting of eight radiating elements and operating within a broad frequency range having the center frequency of 24 GHz are presented. One of the proposed antenna arrays uses a single laminate layer with a ground plane on one side and radiating elements on the other side, the other one is a double layer structure, where the radiating elements with beam‐forming network are placed on the top layer and are fed with the use of the slot coupler. The application of U‐slot radiating elements with enlarged inner parasitic patch allows us to achieve reflection coefficient better than 10 dB within the assumed bandwidth of currently developed FMCW radars, which is 23–25 GHz frequency range. The theoretical analysis as well as experimental results of the manufactured 2 × 4 antenna arrays is shown. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

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.     

Antipodal tapered slot antenna array using broadband decoupling structure for mutual coupling reduction

In this article, an effective method to reduce the mutual coupling between the antipodal tapered slot antenna (ATSA) array is proposed. This method is mainly implemented by loading a set of decoupling structures (DS) perpendicular to the dielectric substrate between two antenna elements. The proposed DS can provide transmission forbidden band which can effectively prevent leaked electromagnetic waves. DS can operate in most frequency bands within 4 to 17.5 GHz. It can enhance about 23 dB isolation between the ATSA array without affecting bandwidth and radiation characteristics. The proposed ATSA arrays are fabricated and tested. The measured results can verify its excellent properties. The proposed broadband decoupling method is a suitable candidate for restrain mutual coupling of ultra‐wideband planar end‐fire antennas. This design sheds new light on broadband decoupling.     

Decoupling antenna array with X‐shaped strip

Manipulating mutual coupling between antenna array elements is always a critical essential in designing phased arrays. In this article, an X‐shaped strip is applied to decouple a five‐element E‐plane microstrip antenna array, whose adjacent elements' center‐to‐center spacing is only 0.45 λ₀. Simulation and measurement results reveal that the proposed array employing the loaded structure exhibits excellent decoupling capability, as in comparison to the reference array, impedance of every port is well matched, mutual coupling between both adjacent elements and nonadjacent ones is efficiently reduced and radiation patterns of every individual patch are markedly corrected. Besides, when beam scanning is performed, the proposed array is equipped with higher gain and lower SLL. The X‐shaped strip predicts a promising application in phased array and a large‐scale array.     

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。     

A modified decoupling scheme for receiving antenna arrays with application to DOA estimation

Mutual coupling in antenna arrays can critically degrade the performance of subsystems, such as those aiming at the estimation of the direction of arrival (DOA) of incident signals. In this article, an accurate form of mutual impedance matrix (MIM) and decoupling methodology is introduced. The methodology for computing the MIM is presented. In the modified MIM and decoupling method, extreme care has been taken to account for all self‐impedance and mutual impedance terms, relating to the mutual coupling effects. It is shown that the new method results in an essential improvement in DOA estimation applications. The resolution and accuracy, achieved using the modified MIM and decoupling methodology, are unmatched with those of the previous techniques. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

A novel suspended stripline‐fed printed square slot array antenna with high‐gain

A novel suspended stripline‐fed square slot array antenna with high gain is presented. Its basic structure is a suspended stripline comprising of three layers. On the top layer, 4 × 4 square slots are etched and act as radiation elements. The middle layer consists of a suspended stripline power divider, and the bottom layer is a metal ground. After optimization by a parallel Genetic Algorithm (GA) on a cluster system, a prototype antenna is fabricated and tested. The measured results agree well with the simulated data, and show a high gain of 18.7 dBi and an impedance bandwidth of 5.7% for S11<‐10 dB are obtained. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Novel ultra‐compact two‐dimensional waveguide‐based metasurface for electromagnetic coupling reduction of microstrip antenna array

A novel ultracompact two‐dimensional (2D) waveguide‐based metasurface is proposed herein and applied for the first time to reduce mutual coupling in antenna array for multiple‐input multiple‐output applications. The unit cell of the proposed 2D waveguide‐based metasurface is ultracompact (8.6 mm × 4.8 mm, equal to λ₀/14.2 × λ₀/25.5) mainly due to the symmetrical spiral lines etched on the ground. The metasurface exhibits a bandgap with two transmission zeros attributing to the negative permeability in the vicinity of magnetic resonance and the negative permittivity in the vicinity of electric resonance. Taking advantage of these two features, a microstrip antenna array is then designed, fabricated, and measured by embedding an 8 × 1 array of the well‐engineered 2D waveguide‐based metasurface elements between two closely spaced (9.2 mm, equal to λ₀/13.3) H‐plane coupled rectangular patches. There is good agreement between the simulated and measured results, indicating that the metasurface effectively reduces antenna mutual coupling by more than 11.18 dB and improves forward gain. The proposed compact structure has one of the highest reported decoupling efficiencies among similar periodic structures with comparable dimensions. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:789–794, 2015.     

Investigation on decoupling of wide band wearable multiple‐input multiple‐output antenna elements using microstrip neutralization line

An investigation to enhance the decoupling between the elements of a compact wide band multiple‐input multiple‐output (MIMO) antenna is presented in this communication. A microstrip neutralization line (NL) is designed on the top of antenna surface to enhance the port isolation. The geometry is embedded on a jeans material to be apposite for the on‐body wearable applications. The antenna covers the frequency spectra from 3.14 to 9.73 GHz (around 102.4%) and fulfills the bandwidth requirements of WiMAX (3.2‐3.8 GHz), WLAN (5.15‐5.35/5.72‐5.85 GHz), C band downlink‐uplink (3.7‐4.2/5.9‐6.425 GHz), downlink defense (7.2‐7.7 GHz), and ITU (8‐8.5 GHz) bands. The port isolation is found to be more than 32 dB over the whole application bands. The antenna is appraised in a rich scattering environment with very minimal envelope correlation coefficient (ECC < 0.12) and great amount of diversity gain (DG > 9.8). The proposed MIMO antenna system is able to achieve the channel capacity loss (CCL) of less than 0.2 BPS/Hz throughout the whole operating band. The proposed structure is etched on an area of 30 × 50 mm². The simulated and measured performances of the proposed antenna are in well‐matched state.     

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.     

Broadband gap‐coupled half‐hexagonal microstrip antenna fed by microstrip‐line resonator

Half‐hexagonal microstrip antenna (H‐HMSA) is a compact version of HMSA, as it resonates at the same fundamental mode frequency. In this article, a compact configuration of a single layer, broadband gap‐coupled H‐HMSA has been proposed. Gap‐coupled H‐HMSA is fed indirectly by a λ/2 microstrip‐line resonator. Broad bandwidth (BW) is achieved with an effective use of resonance introduced by λ/2 resonator and gap‐coupled half‐hexagonal radiating patches. A peak gain of 7.07 dBi and measured BW (S₁₁ ≤ ?10 dB) of 11.5% at the center frequency of 5.2 GHz have been achieved, which occupies a small volume of 0.023 λ₀³ including the ground plane. The radiation patterns remain in the broadside direction throughout the return loss BW. Simulated results of the proposed antenna configuration are experimentally validated with good agreement.     

用于卫星通信的Ku波段宽带双频双极化微带天线阵

利用口径耦合馈电、错位倒相馈网技术和单层微带贴片结构设计出一种用于卫星通信的Ku波段宽带双频双极化微带四元天线阵。用电磁仿真软件CST2008对天线阵的电特性进行了仿真和优化。四元天线阵实测结果表明:水平极化端口在11.21GHz～13.47GHz频率范围内VSWR燮1.5,相对阻抗带宽为18.3%;垂直极化端口在13.43GHz～14.88GHz频率范围内VSWR燮1.5,相对阻抗带宽为10.24%。工作频带内两端口隔离度<-35dB,最大增益为13.2dB,与仿真结果一致。     

A WiMAX circularly polarized antenna array using slot‐coupling feeding technique

In this letter, we present a circular polarization antenna array using the novel slot‐coupling feeding technique. This antenna includes eight elements which are installed in line, each array element is fed by means of two microstrip lines with equal amplitude and phase rotation of 90°. The feeding microstrip lines are coupled to a square patch through a square‐ring slot realized in the feeding network ground plane. With the presence of the slots, this antenna array is able to cover the range of frequency of 3 GHz to 4 GHz. The size of the proposed antenna array is 7λ × 1.8λ × 0.4λ. The measured gain is 15.2 dBi and the bandwidth of S11< ?10 dB is 1 GHz (3–4 GHz, 28%). The antenna array is suited for the WiMAX applications. With the use of slot‐coupling feeding technique, the measured bandwidth for axial ratio < 3 dB is about 24% in the WiMAX frequency band (3.3–3.8GHz). The measured HPBW of the y–z planes is larger than 62°. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:567–574, 2016.     

A dual‐feed microstrip grid array antenna for balanced or unbalanced operation

The development of a dual‐feed microstrip grid array antenna for either balanced or unbalanced operation to radiate pencil‐beam patterns has been described. As an example, the dual‐feed microstrip grid array antenna on RT/duroid 5880 substrate with a size of 60 × 60 × 0.787 mm³ or 4.8λ × 4.8λ × 0.063λ at 24 GHz were designed and fabricated. The measured results show that the dual‐feed microstrip grid array antenna has achieved excellent performances: 4.85% impedance bandwidth, 9.03% gain bandwidth, and 20.6‐dBi gain at 24.15 GHz as a balanced antenna and 6.05% impedance bandwidth, 7.74% gain bandwidth, and 17.8‐dBi gain at 24.15 GHz as an unbalanced antenna. The dual‐feed microstrip grid array antenna is a suitable antenna candidate for radar and sensor applications.     

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.     

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.     

新型锯齿结构微带天线在整流天线中的应用

提出了一种新型带有V形锯齿结构的圆形微带天线,相比于传统的圆形微带天线,该结构微带天线在2GHz的S11值能够达到-26.9dB,二次谐波S11值能够达到-0.2 dB,三次谐波S11值能够达到-3 dB。由于这种良好的抑制高次谐波的作用,在组成整流天线时,可以省掉结构复杂、体积较大的滤波器。并且采用这种结构的天线,具有采用分形技术设计微带天线所获得的缩小天线尺寸的效果。对由该结构组成的整流天线进行仿真和实验测试,获得了超过2.7 V的DC电压,证明了其应用到整流天线中的可行性。     

T‐fed for end‐fire pattern of log‐periodic microstrip array

This article considers feeding techniques for Log Periodic Microstrip‐Antenna Array (LPMA). It proposes simple design equations of LPMA for each feed configuration. For an operating band of 4 to 6 GHz, we use a scaling factor of 1.05. EM simulation studies and measurements on prototypes show that the T Fed LPMA gives 2 to 5 dBi gain improvement over other configurations. Unlike many other LPMA configurations, the proposed configuration follows proper Log‐Periodic principle with almost an end‐fire radiation pattern. These design principles will be useful in LPMA synthesis and the prototype‐based designs can find applications in various areas including Wi‐Fi, C band, and others.