Bandwidth‐enhancement of circularly‐polarized fabry‐perot antenna using single‐layer partially reflective surface

In this article, we investigate bandwidth‐enhancement of a circularly‐polarized (CP) Fabry‐Perot antenna (FPA) using single‐layer partially reflective surface (PRS). The FPA is composed of a single‐feed truncated‐corner square patch antenna, which is covered by the PRS formed by a square aperture array. We revealed that the finite‐sized PRS produces extra resonances and CP radiations for the antenna system, which broadened the impedance matching and axial ratio (AR) bandwidths significantly. For verification, a broadband CP FPA prototype operating near 5.8 GHz was realized and tested. The fabricated antenna with overall size of 125 mm × 125 mm × 23.5 mm achieves a |S₁₁| < ?10 dB bandwidth of 31.7% (5.23‐7.2 GHz), an AR < 3‐dB bandwidth of 13.7% (5.45‐6.25 GHz), the peak gain of 13.3 dBic, a 3‐dB gain bandwidth of 22.38% (5.0‐6.26 GHz), and a radiation efficiency of >91%.     

Dual‐polarized low sidelobe Fabry‐Perot antenna using tapered partially reflective surface

A novel dual‐polarized Fabry‐Perot (FP) cavity antenna with low sidelobes is proposed. Low sidelobes are obtained by using a tapered partially reflective surface (PRS) in the form of circular lattice instead of the conventional rectangular lattice. As the PRS can be regarded as a 2D leaky wave surface on which cylindrical waves propagate outward radially in the form of concentric rings, so arranging the PRS elements in the form of circular lattice and then applying tapering on it yields low sidelobes in both the E‐ and H‐planes. The performance of the proposed PRS is validated by fabricating a dual‐polarized FP antenna and measuring its radiation patterns. Peak realized gains of 18.6 and 18.5 dBi are obtained for horizontal and vertical polarizations respectively, giving an aperture efficiency of around 42%. Measured sidelobe levels are reduced to lower than ?21.3 dB in both the E‐ and H‐planes for the two orthogonal polarizations.     

High performance resonant cavity antenna with non‐uniform metamaterial inspired superstrate

The resonant cavity antenna (RCA) is a class of widely used high gain antennas, but usually suffers from narrow impedance bandwidth owing to its strong resonant property, as well as relatively low aperture efficiency because of its non‐uniform electromagnetic (EM) field distribution on the aperture. This article explores enhancing the RCA's impedance bandwidth and aperture efficiency by designing a non‐uniform metamaterial inspired superstrate, on which the metal patches vary their sizes with respect to their distances to the superstrate's center. After optimized by the Genetic Algorithm, the proposed RCA is designed, fabricated and tested. Measured results agree well with simulated ones and show that in comparison with a RCA with a uniform metamaterial inspired superstrate, this work significantly improves the |S ₁₁| < ?10 dB impedance bandwidth from 2.1% to 6.1%, the gain at the working frequency 10 GHz from 19.07 dBi to 20.55 dBi, and correspondingly the aperture efficiency from 50.5% to 71%. A further analysis estimates that due to the non‐uniform metamaterial inspired superstrate, a more homogeneous distribution for both the amplitude and phase of the EM field is observed on the superstrate's aperture.     

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.     

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 new inhomogeneous partially reflecting surface for Fabry‐Perot antenna to reduce side lobe level

In this article, an extension of the spatial filter method to study Fabry‐Perot antennas with homogeneous or inhomogeneous partially reflecting surface (PRS) of finite size is proposed. This tool was subsequently validated through the study of different Fabry‐Perot antennas, with homogeneous PRS and inhomogeneous GRadient‐INdex (GRIN) PRS that present very high side lobe level (SLL). Since they are due to structure truncation, a new inhomogeneous PRS to reduce the SLL is designed with the new analytical tool. The new inhomogeneous PRS for Fabry‐Perot antenna is characterized by simulations and measurements. Compared to the homogeneous PRS antenna, the proposed PRS allows a SLL reduction of 5 dB without decreasing the 14 dBi directivity.     

Dual circularly polarized loop antenna using a pair of resonant even‐modes

Conceptual design of dual circularly polarized (CP) square loop antennas using a pair of resonant even‐modes for wireless sensor application is presented. A pair of even‐modes is simultaneously excited within a single, nonuniform square loop element and employed to realize a dual circular polarization characteristic. When the natural boundary conditions of the even‐modes and the feed lines are matched, respectively, a bidirectional dual CP loop antenna can be attained at first. Then, a unidirectional dual CP loop antenna is designed by introducing a simple metallic reflector. Both bidirectional and unidirectional designs exhibit dual CP performance with available operation bandwidth of 10.0% and 8.5%. The design approach is expected to get applications in dual CP antenna designs for wireless sensor systems.     

Compact high gain half‐mode substrate integrated waveguide cavity antenna using hybrid mode

In this article, a compact fully planar high gain antenna based on half‐mode substrate integrated waveguide (HMSIW) cavity is presented. The design uses a novel configuration of HMSIW cavity with high length to width ratio along with tapered open edge and a pair of slot stub. The high length to width ratio of the cavity helps to excite closely spaced multiple TE^y_m10 cavity modes within comparatively smaller footprint due to use of the HMSIW cavity. These modes combine to give hybrid mode resonance in the cavity which helps to generate a narrow beam high gain radiation pattern of the antenna. The size of the proposed antenna is further reduced and a pair of slot stub is put along the sidewall of the cavity which helps to sustain similar hybrid mode field distribution within much smaller dimension. A size reduction of 76.7% is achieved in the proposed design configuration without degrading much of the gain performance. The proposed antenna resonates at 9.8 GHz with a gain of 7.9 dBi which is much higher than other reported HMSIW cavity antenna. The proposed antenna may find application in point to point communication, short range radar in X band.     

Metasurface‐based low‐profile high‐gain substrate‐integrated Fabry‐Pérot cavity antenna

A metasurface‐based substrate integrated Fabry‐Pérot cavity (FPC) antenna is presented for improved radiation performance associated with the low profile. A novel partially reflective planar (PRS) artificial magnetic conductor (AMC) structure is proposed as the upper reflector of the substrate integrated FP resonant cavity. A microstrip patch antenna is embedded inside the cavity as a feed. The proposed antenna is designed to operate at 9.35 GHz with the maximum realized gain of 14.2 dBi and the overall profile of λ₀/10 (λ₀ is the operating wavelength in free space). The low‐profile performance of the proposed design outperforms any previous substrate‐integrated FPC antenna design with this gain performance. The influences of the FP cavity on the reduction of the antenna profile and the enhancement of the antenna gain are also investigated. Good agreement between the measured and simulated results validates the feasibility of the analysis and design approach.     

一种基于谐振腔结构的微波位移传感器

设计了一种基于谐振腔原理的位移传感器,能够通过谐振频率的改变进行位移的测试。此微波传感器能够承受高温、高污染等恶劣的工作环境,适合应用于航空发动机的叶尖间隙测试。在理论分析的基础上,建立了工作在24 GHz 左右的微波传感器模型,通过模拟计算得到了量程在0～6 mm 时大于240 MHz/μm的测试灵敏度,验证了该设计的正确性。     

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.     

Three‐dimensional printed wideband,dual‐cavity Ku‐band antenna

A novel three‐dimensional (3D) printed, wideband, and low cost bull's eye antenna is proposed and designed for Ku‐band applications. The proposed antenna covers entire Ku‐band satellite communication bands starting from 10.5 GHz to 14.5 GHz. The antenna structure consists of dual‐cavity radiating aperture surrounded by a circular groove. With the addition of cavity and corrugation, the antenna gain is increased more than 6 dB. The antenna is fabricated using 3D printing technology and conductive painting. Measurement results indicate that the antenna has 72% fractional bandwidth from 8 GHz to 17 GHz. Measured antenna peak gain is 13.5 dBi at 13 GHz and no less than 11.5 dBi throughout the entire Ku band.     

High‐gain waveguide slot antenna using simple parasitic patch's cover

In this article, a way based on using miniature patch cells has been proposed to increase gain and bandwidth of the waveguide slot antenna. In the presented approach, an array of 3 × 3 metal patches has been used as superstrate to create Fabry Perot theorem resonance cavity. The proposed high ‐ gain and simple antenna is composed of a conventional waveguide slot antenna with an extended broad wall, and an array of parasitic patches which are symmetrically placed over slot at a distance of about free ‐ space half wavelength. The slot has been created on a rectangular waveguide WR90 with 22.86 mm × 10.16 mm × 52.5 mm dimension, also extended wall dimension is 2λ₀ (67.5 mm) × 3λ₀ (107 mm). It has been shown that the proposed structure compared with the conventional waveguide slot antenna improves antenna peak gain from 6.5 to 16.5 dBi and, in the same time, antenna bandwidth from 11% to around 16.2%. More important advantage of the proposed antenna is that unlike to other Fabry Perot antenna with the same gain, there is not any dielectric material in the proposed structure. A prototype antenna was simulated, fabricated, and measured for verification.     

A compact asymmetric slot dual band antenna fed by CPW for PCS and UWB applications

A compact slot antenna with an overall dimension of 30 × 30 × 1.6 mm³ is proposed for dual band applications. The radiating element is a hexagonal shape patch which protrudes from a Co‐Planar Waveguide (CPW) feed into a step shape slot. The slot is basically rectangular in shape and is extended by inserting rectangular cuts of different sizes on the ground plane around it. The ultrawide impedance bandwidth is achieved using asymmetric feed line along with extended rectangular cuts around the slot. For realizing the second band for personal communication system applications (near 1.9 GHz), a metallic stub of quarter wave length is attached at the top of the slot. The measured impedance bandwidth (for S₁₁ < ?10 dB) is 110 MHz (1.86–1.97 GHz) for the first band and 9 GHz (3.0–12.0 GHz) for the second band. The antenna is further characterized by omnidirectional radiation patterns in the H‐plane, dumb‐bell shape radiation patterns in the E‐plane and a peak gain of 3–5 dBi over the ultrawideband. All the measured results are found to be in good agreement with the simulated results. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:243–254, 2015.     

A low‐profile dual port UWB‐MIMO/diversity antenna with band rejection ability

A band notched ultra‐wideband (UWB) antenna is presented in this article as a good prospect for multiple‐input multiple‐output (MIMO)/diversity application. The proposed MIMO antenna is constituted of two modified rectangle‐shaped patch antenna elements. A stepped stub is extended from the modified ground plane as a decoupling element between the radiators to realize a good isolation level between them. A band rejection response is obtained by connecting an open resonant stub to each of the radiators. The simulated prototype is fabricated and tested for verification. Results reveal that the proposed prototype provides a 10 dB return loss bandwidth from 3.08 to 10.98 GHz with band notch characteristics from 4.98 to 5.96 GHz, and a good port isolation level (S₂₁ ≤ 20). Diversity performances are ensured in terms of total active reflection coefficient, envelope correlation coefficient (<0.013 except notch band), diversity gain (≈9.51 dB), mean effective gain ratio (≈1), and channel capacity loss (≤0.35 bps/HZ except notch band). It evidences that the presented band notched UWB antenna can be a good prospective for MIMO/diversity applications.     

Design of a novel metasurface for dual‐band Fabry‐Pérot cavity antenna

A novel reflective metasurface which presents different reflection phases to different polarization waves is designed in this article. The metasurface is used as the ground plane of a Fabry‐Pérot cavity (FPC) antenna. The radiator of the FPC antenna is a dual‐band patch antenna which has different polarizations in different bands, so by tuning the reflection phase of the metasurface correctly, the FPC antenna can work in two frequency bands. A prototype antenna is fabricated and measured. The measured results show that the antenna can operate at 8.35‐8.56 GHz (2.5%) in x‐polarization and 9.5‐10.1 GHz (6.1%) in y‐polarization. The maximum realized gains of the antenna in two bands are 17.6 dB at 8.75 GHz and 19 dB at 9.8 GHz. The measured results agree well with the simulated results which confirm the correctness of the design.     

A low‐profile wideband dual‐polarized antenna with gain enhancement,low gain variations,and low cross polarization for 5G indoor communications

A low‐profile wideband dual‐polarized antenna with high gain, low gain variations, and low cross‐polarization for the fifth generation (5G) indoor distribution system is proposed. By using circular‐thread vase‐shaped structure, a low profile of 0.23λ₀ (λ₀ is the free‐space wavelength at the starting frequency) as well as low gain variation feature can be achieved by the vertically polarized (VP) radiating element. An eight‐way power divider network is employed to feed the horizontally polarized (HP) dipoles so that wideband performance is obtained. Here, eight pairs of arc‐shaped parasitic strips are used to broaden the bandwidth, and eight pairs of director elements are introduced to enhance the gain and reduce the gain variations. In addition, the protruded stubs that are extended from the circular ground plane will help to reduce the cross polarization in the VP direction. Measured results show that a bandwidth of 46.5% (3.3‐5.3 GHz) (S₁₁ < ?10 dB) with a gain of 0.85 ± 0.35 dBi, and another bandwidth of 85.0% (2.5‐6.2 GHz) with a gain of 4.75 ± 1.75 dBi can be realized in the HP and VP directions, respectively. Furthermore, high isolation (>27 dB) and low cross polarization (<?24 dB) can also be attained. Therefore, the proposed antenna is a good candidate for 5G indoor distributed system.     

A dual band leaky wave antenna based on modified substrate integrated waveguide

In this article, a new leaky wave antenna (LWA) based on modified substrate integrated waveguide (SIW) is introduced. At first, the modified SIW structure is presented and it is shown that it supports propagation of quasi‐TEM with nearly uniform electric field distribution. Then, a new cell based on diagonal‐shaped slots embedded on top surface of the structure is introduced and its dispersion characteristics and its different radiation regions are determined. A LWA made of 15 unit cells is designed and a prototype of the antenna is fabricated. The proposed LWA is simulated using a software package and its radiation characteristics are also measured. It is shown that a good agreement is obtained between simulated and measured results and two frequency bands are obtained. In the frequency range of 7 GHz to 8.25 GHz, it radiates in forward region with maximum gain of 11.3 dB and scan angles from 54° to end‐fire. In addition, it radiates in backward region from ?70° to broadside from 14 GHz up to 20 GHz with maximum gain of 16.47 dB. High gain, compactness, and wide scan angles are the advantages of the proposed LWA.     

A broadband slant polarized cavity backed microstrip‐fed wide‐slot antenna array

This article deals with the design of a broadband cavity‐backed microstrip‐fed wide‐slot antenna array for L‐band applications. For verification purpose, a sample 1 × 4‐element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a measured impedance bandwidth of 1.4 GHz (90%) with frequency of 0.85 to 2.25 GHz and the gain is higher than 11 dBi. The designed antenna has small size and low weight and can be fabricated using a low‐cost fabrication process for easy integration with RF circuits and microwave components. This work is useful for some radar applications and radio frequency identification systems.     

A new compact planar UWB monopole antenna

A new compact planar monopole antenna which covers an ultra wide bandwidth of ～147% from 2.96 to 19.43 GHz for S₁₁ ≤ ?10 dB is presented. The proposed antenna has simple configuration and easily fed by using a 50 Ω microstrip line. The total size of the antenna is 30 × 26 × 1.6 mm³. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.