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.     

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot‐strip‐foam‐inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S₁₁ < ?10 dB) and side lobe level (SLL) of ?25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.     

A novel dual‐mode patch antenna with pattern diversity and beam‐tilting for aircraft applications

A dual‐mode patch antenna with pattern diversity that is beam‐tilted in a specific direction is presented. By placing a rectangular metal cavity below the circular patch and simultaneously shorting one end of the patch, the antenna produces tilted beams for dual‐mode radiation patterns. One pattern is excited using a proximity‐fed L‐shaped probe that generates a beam with a tilt angle of 25° from the broadside direction. The second pattern is excited using a coplanar waveguide (CPW)‐based feeding network that generates two beams with a tilt angle of θ_max = ±45° in the directions of ?_max = 70° and ? 70°. The tilt angle can be varied by adjusting the metal cavity's length. A prototype antenna for operation at 2.38 GHz was fabricated and measured. The results indicate that the overlapped bandwidth (|S₁₁| < ?10 dB) for the two patterns is 330 MHz (2.22‐2.55 GHz). The measured peak gains for the two patterns are 6.74‐6.94 dBi and 5.82‐6.74 dBi, respectively. The isolation between the two ports is 18 dB.     

Single‐feed wideband circularly polarized patch antenna using dual mode defected ground waveguide coupling structure

A dual mode square‐ring defected ground waveguide (SR‐DGW) with defected square patch is first proposed to excite a single‐feed dual mode circularly polarized (CP) patch antenna, which can improve the impedance bandwidth and achieve the CP radiation pattern. The defected square patch is called the perturbation element. By optimizing the size of the perturbation, the degenerate modes of the dual mode SR‐DGW are split and their orthogonal modes can be excited simultaneously. Due to the dual mode of the SR‐DGW, the TM₀₁ mode, and TM₁₀ mode of the square patch antenna are excited simultaneously, which can improve the impedance bandwidth of the antenna. Meanwhile, owing to the orthogonal modes, CP radiation pattern of the antenna is obtained. Then, for a better impedance matching, an L‐shaped spurline embedded in the feedline is introduced. The simulated and measured results show a good performance of the proposed antenna. The measured ?10 dB impedance bandwidth is 10.4% (3.56 GHz‐3.95 GHz). The measured 3 dB axial ratio bandwidth is 5.36% (3.63 GHz‐3.83 GHz). Detailed designs and experiments are described and discussed.     

Broadband conical beam antenna in planar environment

In this article, a substrate‐truncated microstrip circular patch antenna with shorting vias is proposed for X‐band applications. The bandwidth of the designed antenna is substantially increased by making two slots—one circular and another annular ring—at the top of the structure which actually helps in bringing two individual resonating frequencies closer to each other. The antenna is simulated using the Ansoft HFSS, and various parameters are optimized for better performance. The deigned structure is finally fabricated and tested, and the measured data fairly agree with the simulated results. The measured relative impedance bandwidth (|S₁₁| < ?10 dB) is found to be 28.5% (8.9‐11.85 GHz). The proposed antenna is behaving like a monopole with the radiated beam of conical shaped in the entire operating band having a maximum gain of 7.2 dBi.     

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.     

一种小型内寄生贴片环形全向天线的设计

文章提出了一种新型的内寄生贴片环形天线,在其周向该天线具有近似均匀辐射的方向图特征。作者依照文章技术加工测试了一个空气介质的环形天线,仿真与实测结果吻合良好,天线最大增益达到2.66dBi,其工作带宽(S11<-10dB)为1.53GHz到1.61GHz,内寄生贴片的引入使得该天线在其轴向的尺寸仅有0.11波长。     

A beam scanning Fabry–Pérot cavity antenna for millimeter‐wave applications

A beam scanning Fabry‐Pérot cavity antenna (FPCA) for 28 GHz‐band is presented in this article. The proposed antenna consists of a slot‐fed patch antenna and several layers of perforated superstrates with different dielectric constant. The beam of the antenna can be controlled by moving the superstrate over the antenna. By increasing the offset between the feeding antenna and the superstrate, a larger tilt angle can be obtained. The size of the antenna is 0.95λ₀ × 0.95λ₀ × 0.48λ₀ at 28.5 GHz. The results show the proposed antenna achieves an impedance bandwidth (S₁₁ < ‐10 dB) of 10.5% (27.2‐30.2 GHz), and the beam can be scanned from 0° to 14° in the yoz‐plane with the offset changed from 0 mm to 2 mm. The gain of the antenna is enhanced by 5 dBi in comparison with the feeding antenna without the superstrate, which ranges from 10.91 to 11.53 dBi with the different offset. The proposed antenna is fabricated and shows a good agreement with simulated result.     

Equilateral triangular patch antenna for UHF RFID applications

This article proposes an equilateral triangule‐shaped patch antenna for radio frequency identification (RFID) applications in the 900 MHz (902–928 MHz) ultra high frequency (UHF) band. To achieve optimal impedance matching and 10‐dB operating bandwidth at the desired band, the L‐shaped probe‐feed technique was used as the feeding structure of the proposed antenna. Furthermore, a near semicircular notch was also loaded into the patch so that good circularly polarized (CP) radiation can be generated from the proposed patch antenna. By simply shifting the position or radius of this notch, the CP frequency can be varied with ease. Here, 10‐dB impedance bandwidth and 3‐dB axial ratio bandwidth of 25 and 3% were achieved. Furthermore, stable gain variation of approximately 6 dBi was also exhibited across the RFID UHF band. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:580–586, 2014.     

Bandwidth and gain improvements of low‐profile H‐shaped microstrip patch antenna under quadruple‐mode resonance

A wideband low profile H‐shaped microstrip patch antenna (MPA) with reallocated quadruple‐mode resonance is presented for indoor wireless communication application. In this paper, the TM₂₀ (mode 1), TM₀₂ (mode 2), TM₂₂ (mode 3), and additionally notch mode 4 of the proposed MPA are simultaneously employed. First, the rectangular radiating patch is reshaped as an H‐shaped radiator so as to separate a pair of degenerate modes (mode 1 and mode 2). Then, a pair of linear notches is cut on the diagonal of the patch to excite an additional notch resonance (mode 4). Finally, in order to improve the frequency of mode 1, four shorting pins are placed at the four corners of the H‐shaped patch. Therefore, the bandwidth of the antenna is dramatically increased up by utilizing four resonant modes (modes 1, 2, 3, and 4). A prototype of H‐shaped patch antenna with notches and shorting pins is manufactured and measured. The results show that the antenna achieves a broad bandwidth of about 31.7% (2.31‐3.18 GHz), and its profile is only 0.036 wavelength of center frequency. It is particularly noticed that a relative high gain of around 9.8 dBi is successfully acquired, while keeping relative stable dual‐beam radiation patterns.     

Efficient design of compact millimeter wave microstrip linear array with bandwidth enhancement and sidelobe reduction

In this article, a novel linear mmWave antenna array with series‐feed network is proposed to enhance the bandwidth and reduce sidelobe level without increasing the patch size. The proposed linear array is consisted of four identical wideband array elements, which are all under operation TM₁₀ and TM₀₂ modes by loading shorting pin and rectangular slots. Additionally, through loading symmetry circle‐shaped slots for the four elements, impedance matching of linear array is achieved. Furthermore, multi‐parameters unified‐optimization (MPUO) based on imperial competition algorithm (ICA) is proposed to uniformly optimize all linear array parameters. To verify this design, the proposed linear array is fabricated with a small patch area of 7.5 × 3.914 × 0.254 mm³. The measured results show that the bandwidth is enhanced to 2.05GHz, which is 0.57GHz wider than that of simulation. The simulated peak gain reaches 13dBi while the sidelobe level is reduced to about ?19 dB at 28.6GHz. Moreover, the computation cost using MPUO is reduced by 98.12% compared with that of independent parameters optimization.     

Design of a tunable omnidirectional circularly polarized antenna based on VO2

In this article, a VO₂‐based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO₂. By utilizing the characteristics of insulator‐metal phase transition of VO₂, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO₂ and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO₂ do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T ≥ 68°C (state I), the proposed antenna has a 10‐dB impedance bandwidth of 15.9% (2.09‐2.45 GHz), and a 3‐dB axial ratio (AR) bandwidth of 23.4% (2.04‐2.58 GHz). When T < 68°C (state II), it has a bandwidth of 6.5% (2.38‐2.54 GHz) with S₁₁ below ?10 dB, and a bandwidth of 19.9% (2.39‐2.92 GHz) with AR below 3 dB.     

Circularly polarized stacked patch antenna array with enhanced bandwidth for S‐band applications

In this article, a circularly polarized coupled slot 1 × 4 stacked patch antenna array with enhanced bandwidth is proposed for S‐band applications. Initially, a patch antenna radiating at 2.79 GHz is designed and maximum energy from feedline to patch element is coupled using two rectangular slots. Whereas, a parallel feedline structure is designed to provide polarization flexibility by creating 0, 90 , and 180^o phase differences. Then, a truncated patch element is vertically stacked in the design to achieve broader bandwidth of 600 MHz over frequency range from 2.4 to 3.0 GHz. Finally, a coupled slot 1 × 4 array stacked antenna array having feedline line structure to provide 90^o phase difference for circular polarization is designed and fabricated for measurements. It is observed that the final design achieved target specification having impedance matching (|S₁₁ | (dB) < ?10 dB over 2.4 to 3.0 GHz, broad band circular polarization, and 11.5 dBic total gain. Overall, a good agreement between simulated and measurement results is observed.     

Design of circular patch antenna with a high gain by using a novel artificial planar dual‐layer metamaterial superstrate

This study presents a new dual‐layer metasurface structure proposed to enhance the performance of a circular patch antenna. A novel unit cell planar metasurface is characterized by nearly equal enhanced effective permeability and permittivity ε_r ? μ_r > 1 at the resonant frequency. In addition, a 5*5 array of these unit cells are used as a superstrate over a circular patch antenna which is fed by 50 Ω microstrip line and operating at 2.45 GHz for improving the antenna performance. The patch antenna gain is increased by creating an in‐phase electric field area on the top surface of the metasurface. The obtained results showed that the maximum gain of the antenna increased from 2.31 dBi to 7.5 dBi. A 30% increase in the bandwidth is also remarked. The proposed antenna with metasurface occupies an overall volume of 1.01λ_g ×1.01λ_g ×0.025λ_g . The simulation analysis and measured results were performed using the microwave studio, high frequency structure simulator software, and vector network analyzer. The proposed antenna prototype has been fabricated. The measured results indicate that the antenna has a good impedance matching in the desired operating band (2.37‐2.49 GHz) with the resonant frequency of 2.44 GHz which make the proposed antenna appropriate for microwave applications.     

A low‐profile wideband dual‐polarization patch antenna with antisymmetric feeding network

In this paper, a novel broadband dual‐polarization patch antenna is proposed. Antisymmetric Γ feeding network is applied to excite the radiating patch etched on the upper side of the horizontal substrate, which could minimize the undesired radiation from the probe and extend the impedance bandwidth. For verifying the proposed approach, a prototype is fabricated and measured, the simulated and measured results show the antenna has a wide impedance bandwidth of 48% (1.66‐2.71 GHz) for S11 < ?10 dB, as well as stable radiation gain around 9.5 dBi with low cross‐polarization. In addition, the total height of the antenna is only 0.17 λ₀ ( λ₀ is the free space wavelength of central frequency) and high port‐to‐port isolation is better than 30 dB. The characteristics of the proposed antenna illustrate it can be an indication for a micro base station in the mobile communication system.     

A multi‐mode wideband omnidirectional monopolar patch antenna for indoor wireless communication systems

A wideband omnidirectional monopolar patch antenna merged multi‐mode with a simple structure is proposed in this article. The antenna consists of a circular patch and a concentric annular ring, which is coupled‐fed by a T‐shape monopole at its center. A wideband performance is achieved by converging multi‐mode: TM₀₂ mode of the circular patch, TM₀₂ mode of the annular ring and monopole mode of the T‐shape monopole. The measured results show that the proposed antenna has an impedance bandwidth of 55.3% from 4.45GHz to 7.85GHz. All of the three resonant modes lead to conical radiation patterns in the elevation plane and omnidirectional radiation patterns in the azimuth plane, and the measured peak gain varies from 6.1 to 10 dBi within the operating band, which verifies it can be a good choice for indoor wireless communication systems.     

Enhancement of gain with corrugated Y‐shaped patch antenna for triple‐band applications

In this article, investigation has been carried out on Y‐shaped patch antenna to produce triple‐band for wireless applications. The corrugated Y‐shaped patch antenna is considered to produce low reflection coefficient with high gain at the triple‐bands. The corrugated Y‐shaped patch antenna is resonates at 4.19 GHz (4‐4.43 GHz), 8.79 GHz (8.61‐9.01 GHz), 13 GHz (12.6‐13.6 GHz) frequencies with reflection coefficient of ?29.26 dB, ?34.87 dB, ?40.37 dB and gain 5.01 dBi, 5.42 dBi, 7.46 dBi, respectively. The proposed corrugated Y‐shaped patch antenna works three frequency bands at radio communications, satellite communications, and aeronautical radio navigation applications, respectively.     

A multistate high gain antenna based on metasurface

A multi‐state high gain antenna based on metasurface is proposed. The antenna is composed of two stacking layers and a ground plane. The metasurface is constituted by two layers with the same size. And both of the two layers contain a copper patch array which is formed by 4 × 4 square copper cells uniformly distributed along x and y directions. The metasurface antenna is excited by the aperture coupled structure. The structure is consists of an anomaly microstrip line and a narrow slot etched in the ground plane. Genetic algorithm (GA) is adopted to optimize all the parameters and obtain the best performance of the metasurface antenna. By appropriately choosing the dimensions of the antenna, the proposed antenna can be achieved with the impedance bandwidth (RL≥10 dB) of about 340 MHz (7.8% at 4.36 GHz), 180 MHz (3.6% at 5.02 GHz), and 2800 MHz (41.1% at 6.81 GHz). The peak gain of the proposed antenna is 10.1dBi, 6.9 dBi, and 10.5dBi at 4.26 GHz, 5 GHz, and 7 GHz. In addition, the proposed metasurface antenna can work in multistate, which makes it an excellent candidate for practical applications.     

A broadband circularly polarized monopole antenna

A compact modified C‐shaped monopole antenna with broadband circular polarization is proposed, fabricated and measured. The antenna structure is simple and only consists of combined modified C‐shaped radiation patch and an improved ground plane with the overall size of 25 × 25 × 1 mm³. By cutting the corner on the modified C‐shaped patch and adding triangular stubs on the ground plane, the wide impedance bandwidth and axial ratio bandwidth are achieved. The design process of the antenna is given, and the circular polarization mechanism of the circularly polarized antenna is analyzed from the surface current distributions. The measured impedance bandwidth is 95.2% (4.4‐12.4 GHz) with return loss better than 10 dB, and the measured 3 dB axial ratio bandwidth is 96.8% (4.42‐12.72 GHz). The peak gain is above 3.0 dBi within the working band, which indicates that it is suitable for application of ultra‐wideband (UWB) wireless communication systems and satellite communication systems.     

Compact wideband circularly polarized horn antenna with tapered slot‐coupled feeding for Ku‐band applications

A compact wideband circularly polarized (CP) horn antenna with slot‐coupled feeding structure at Ku band for satellite communication is devised. The proposed design is based on a square aperture horn antenna with two orthogonal ridges, which is fed by nonuniform curved slot along the diagonal of the horn on the bottom cavity. And in order to improve the impedance matching, a staircase typed ridge is connected the feeding probe as a matching network. Moreover, two orthogonal ridges are excited with a tapered slot coupled by the staircase ridges via feeding probe. Wideband CP performance is achieved with an overall physical dimension of 9 mm × 9 mm × 14 mm (0.045λ₀ × 0.045λ₀ × 0.07λ₀ at frequency of 15 GHz). It is experimentally demonstrated that the proposed antenna achieves: a wide 10‐dB return loss bandwidth of about 2.4 GHz, a 3‐dB axial ratio bandwidth of 1 GHz, and a peak gain of 6.5 dBi.