dB Gain Bandwidth Research Articles

A Low-Profile Wideband Surface-Mountable Substrate-Integrated Waveguide Horn Antenna

A low-profile surface-mountable substrate-integrated waveguide (SIW) horn antenna with wideband performance is proposed in this letter. In order to reduce the serious impedance mismatch at the SIW horn aperture resulting from the thin substrate (0.12 λ0), a semi-open SIW horn is designed by gradually detaching upper broadwall while maintaining another one. Furthermore, in order to realize wide bandwidth for the SIW horn antenna, air-vias are drilled into the semi-open horn to realize smooth transition from semi-open horn to free space. Finally, a fabricated prototype is measured, and results indicate that a 35.7% impedance bandwidth ranging from 19.1 to 27.4 GHz and a 31.8% 3 dB gain bandwidth ranging from 19.3 to 26.6 GHz are obtained, respectively. Stable end fire radiation patterns are observed across the operating band.

Broadband circularly polarized high-gain antenna design based on linear-to-circular polarization conversion focusing metasurface

A single-layer reflecting element is proposed based on the principle of linear-to-circular polarization conversion focusing metasurface, which can independently control the phases of x-polarized and y-polarized reflecting waves and operate in a broadband of 10-14 GHz. Following the generalized Snell's laws of reflection, a super cell is designed with a phase-gradient of -60 for x-polarized waves and 60 for y-polarized waves, and the simulation results show the well wideband anomalous reflection as expected. In the design of the multifunctional metasurface, the 1313 unit cells are used to satisfy the parabolic profile and the focal-distance-to-diameter ratio is set to be 0.5. The phase compensation for forming a constant aperture phase is provided by the individual reflected elements with different structure parameters and x-y=90 is used to realize polarization conversion. The designed sample is simulated in CST Microwave Studio and the results show that both of the x-polarized and y-polarized plane waves are well focused through the reflection of the focusing metasurface in a broadband of 10-14 GHz. Traditionally, multi-layer element is used to broaden phase coverage and bandwidth, the single-layer design in this paper greatly reduces the cost, processing difficulty and thickness of the lens. For further application, a linearly polarized Vivaldi antenna with a highest gain of 10 dB is located at the focal point of metasurface and the angle included between its polarization direction and x-axis is 45 in order to acquire right-handed circularly polarized reflecting wave. According to the reversibility principle of electromagnetic wave propagation, the spherical wave radiated by the feed antenna is converted into plane wave by the reflection of the focusing metasurface so that the antenna gain is remarkably enhanced. Simultaneously, the linearly polarized wave can be transformed into circularly polarized wave. Finally, the feed antenna and the metasurface are fabricated, assembled and measured. Numerical and experimental results are in good agreement with each other, which shows that the -1 dB gain bandwidth of the high-gain antenna is 24% (11-14 GHz) and the 3 dB axial ratio bandwidth is 29.8% (10-13.5 GHz). In addition, the gain at 12 GHz reaches a highest value of 19.6 dBic, and the aperture efficiency is more than 54%. The good performances indicate that the proposed broadband high-gain circularly polarized antenna has a well promising application in various communication systems. It is worth noting that the horizontally polarized, vertically polarized, right-handed circularly polarized and left-handed circularly polarized high-gain antenna can be realized with the rotation of feed antenna. In this case the idea is more versatile and valuable for designing the polarization reconfigurable antenna systems.

Dual‐band, dual‐polarised metallic slot transmitarray antenna

A metallic, dual-band, dual polarised slot-based transmitarray antenna is presented. The antenna consists of three thin metallic layers do not use any dielectric substrates, with air gaps in between the layers. The unit cell uses interleaved orthogonal slots, as well as crossed-dipole slot and uniplanar compact photonic bandgap slot elements to provide the lower and upper frequency band resonators, respectively. The frequency separation between the two resonances can be adjusted from closely spaced to far from each other. The antenna provides dual linear polarisation and circular polarisation with the use of the appropriate feed. The fabricated transmitarray antenna provides two independent frequency bands with a band ratio of 1.13 and low mutual coupling. The measurement of a 14 × 14 element transmitarray antenna at 11 GHz shows a maximum gain of 23.74 dB with -1 dB gain bandwidth of 6.8% and aperture efficiency of 38%; at 12.5 GHz, a maximum gain of 24.45 dB is obtained with -1 dB gain bandwidth of 5.4% and aperture efficiency of 34.6%. The antenna is simulated by using the CST software; the ADS package is used for equivalent circuit simulation.

Ultrathin flat microwave transmitarray antenna for dual‐polarised operations

A dual-polarised phase-correcting microwave transmitarray that is based on an ultrathin phase-shifting surface (PSS) has been developed at 22 GHz. The FSS element in this array has a square shape with the rotationally symmetrical geometry. It consists of two identical metallic layers etched on the two sides of a single dielectric layer. A phase-shifting range of about 330° is achieved. A planar slot-fed patch antenna was developed as the feed source for the compact structure. The transmitarray prototype, which is fed by a planar antenna, as well as a standard horn, was measured separately. The results show that peak gains of 25.82 and 27.45 dBi and 1 dB gain bandwidths of 6.8 and 9.5% are achieved for the two feed cases.

‘Phoenix’ reflectarray unit cell with reduced size and inductive loading

This study presents a new Phoenix unit cell with reduced size (λ0/3 at centre frequency). Three different techniques are investigated to preserve a complete 360° phase range, with quasi-linear and parallel phase responses over a reasonable frequency band, in spite of this small size. The phase cycle successively uses two different printed elements with complementary capacitive and inductive responses. The studied techniques aim at increasing the insufficient inductive effect. As a demonstration, a 1877-element reflectarray is fabricated with the technique compatible with a single-substrate fabrication process. Measured results show a 1 dB gain bandwidth of 11.3%. © The Institution of Engineering and Technology 2016.

Design of high gain and wide band EBG resonator antenna with dual layers of same dielectric superstrate at X-bands

A wide band EBG resonator antenna with two layer of dielectric superstrates of the same material is design which is operating in X band. The EBG superstrates act as Partially Reflective Surfaces (PRS) having positive reflection phase curve which are suspended above a double sided dipole patch antenna fed by a coaxial cable pass through ground plane. Thus a resonator cavity is constructed which increases the bandwidth and gain of the feed antenna. The measured results validate the simulation results obtain from Computer Simulation Technology (CST) microwave studio. These results show that the antenna posses a 3 dB gain bandwidth from 8.5 GHz to 11.2 GHz, with a peak gain of 15.3 dBi. Furthermore, the scattering parameter S11 is well within range from 8.6 GHz to 11 GHz.

Compact wideband circularly polarised resonant cavity antenna using a single dielectric superstrate

A wideband resonant cavity antenna (RCA) with circular polarisation (CP) and high-gain characteristics is presented. A crossed bowtie dipole is used as a primary wideband CP radiator for the RCA. A half-wavelength planar partially reflecting surface is utilised to achieve high-gain broadside radiation and wide axial ratio (AR) as well as gain bandwidths. The final design yields measured −10 dB impedance and 3 dB AR bandwidths ranging from 5.6 to 8.4 GHz and from 6.3 to 8.15 GHz, respectively. Experimental results also showed an average gain of 14.5 dBic over the CP operating bandwidth and a 3 dB gain bandwidth of 42.7% (5.7–8.8 GHz).

A metamaterial-inspired wideband high-gain FABRY-Perot resonator microstrip patch antenna

In this article, a wide impedance bandwidth and gain bandwidth Fabry–Perot resonator microstrip patch antenna based on metamaterials was presented. The metamaterial superstrate, which is constructed by a doubly periodic array of complementary cross elements, achieved stable reflection phase response within the wide desired operation frequency range to broaden the bandwidth. This antenna worked at 13 GHz, and the simulated and measured impedance bandwidth (S11 < −10 dB) was 1.56 and 1.33 GHz, respectively. The simulated 3 dB gain bandwidth was about 1.1 GHz, and the measured results verified the design. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1675–1678, 2016

Single half-effective-wavelength-thick dielectric layer

A compact wideband resonant cavity antenna is presented. A single layer of an approximately half-effective-wavelength-thick partially reflecting surface, which has a very wide transmission band and the positive slope of a reflection phase against frequency, is employed to achieve very wide half power gain bandwidth. The experiment results demonstrate that the antenna has a −10 dB impedance bandwidth of 49.1% (6–9.9 GHz) and a 3 dB gain bandwidth of 48.7% (5.9–9.7 GHz) with a maximum broadside gain of 14.9 dBi. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1693–1696, 2016

Compact all‐metallic cavity‐cascaded antenna

A compact all-metallic cavity-cascaded antenna is presented. A two-end-shorted metallic plate is shorted and divided averagely by five identical shorting walls alternatively, forming five alternatively cascaded open cavities. By selecting proper width of the metallic plate and length of the shorting walls, all the five open cavities operate in the TM1n0 (n = 0.5) mode, generating five fringing fields with the same phase. Thus, effective radiation is achieved. The proposed antenna is operated in the 5-order mode, e.g. five standing waves are distributed along the proposed antenna. It only occupies a volume of 0.43λ 0 × 2.83λ 0 (λ 0 is the wavelength of the centre frequency). Moreover, the proposed antenna is fabricated by all metal, resulting in low cost, light weight, wide bandwidth, high gain and high efficiency. A prototype that can provide an overlapped impedance bandwidth and 3 dB gain bandwidth of 7.72% from 8.10 to 8.75 GHz and a peak gain of 13.37 dBi at 8.5 GHz is built and measured.

Analysis and experiment of stair‐shaped waveguide‐fed dielectric resonator antenna

Theoretical analysis of a stair-shaped waveguide-fed hemispherical dielectric resonator antenna (DRA) using method of moments (MoM) is presented in this study. Waveguide steps are used to enhance the coupling of direct coupled waveguide-fed DRA. Theoretical analysis is performed by solving coupled integral equations obtained by imposing magnetic field boundary conditions at various apertures using MoM. DRA and the steps are analysed using Green's function. For waveguide, modal analysis is performed. In order to determine the effects of various design parameters, parametric analysis has been carried out using the code developed. Experimental results confirm the validity of the proposed theory. The antenna has a maximum gain of 5.7 dBi at 9.09 GHz with a 3 dB gain bandwidth of 11.08%. Reasonable agreement is observed between the measured and simulated radiation patterns. The proposed coupling enhancement technique guarantees more than 98% coupling.

Broadband Transmitarray Antenna Design Using Polarization-Insensitive Frequency Selective Surfaces

Applications of frequency selective surfaces (FSSs) for transmitarray antennas (TAs) are investigated. Two broadband polarization-insensitive FSS elements are proposed and their transmission performances are evaluated against the desired amplitude and phase responses for this application. Accordingly, two small aperture $\left({{20}\,\text{cm} \times {20}\,\text{cm}} \right)$ broadband TAs are designed and their radiation characteristics are compared to each other. The simulated results show a maximum aperture efficiency of (38.4% and 36.7%), $- {1}\,$ and $- {2}$ dB gain bandwidths of (13.5% and 11.8%) and (16.08% and 19.75%) for the first and second TA, respectively. The antenna with superior performances is successfully fabricated and tested as a proof of concept. The measured maximum aperture efficiency of this TA is 34.64% and its $- {1}$ and $- {2}$ dB gain bandwidths are 10.2% and 14.83%, respectively. Moreover, the scanning performance of this antenna is also investigated by changing the feed location and it is shown that reasonable results in terms of sidelobe levels $(\text{less than } {-}{15}\,\text{dB})$ , appearance of shoulder and coma lobes, and gain loss $(\text{better than } {-}{3}\,\text{dB})$ are achieved for scanning range up to $\pm {35}^\circ $ in both E- and H-planes. In addition, a new low-cost cavity-backed folded dipole antenna (CBFDA) is also proposed as a feed for TAs in this work. The introduced feed offers the required radiation pattern to illuminate the designed FSSs.

Broadband circularly polarized high-gain antenna design based on single-layer reflecting metasurface

According to the Pancharatnam-Berry phase principle, a single-layer reflecting element is proposed for steering the phase of the electromagnetic wave. The structure of the element is composed of metabolic cross wire and copper ground sheet, which are separated by an FR4 dielectric substrate with a thickness of 3 mm. When the incident wave is circularly polarized, different rotary angles of the element are used to achieve the co-polarization reflection with high efficiency in a broadband of 11-16 GHz. In the design of the focusing metasurface, the phase compensation for forming a constant aperture phase is provided by the individual reflected element with a different rotated angle. Remarkably, the size of the element is only 5 mm (0.230), and then it can be more accurate to control the phase of the array. The focusing metasurface is composed of 1515 elements with a focal length of 30 mm at 13.5 GHz. The designed sample is simulated in CST Microwave Studio. The results show that the incident circularly polarized plane wave is well transformed into a spherical wave in the band from 11 to 16 GHz, and the focal length is around 30 mm. For further application, a unidirectional Archimedean spiral antenna is located at the focal point of the metasurface. According to the reversibility principle of electromagnetic wave propagation, the spherical wave radiated by the feed antenna is converted into a plane wave by the reflecting metasurface, so that the antenna gain is remarkably enhanced. Through adjusting the distance between the feed antenna and the focusing metasurface, we find that 28 mm is the best distance. Finally, the feed antenna and the metasurface are fabricated, assembled and measured. Numerical and experimental results are in good agreement with each other, showing that the -1 dB gain bandwidth of the high-gain antenna is 12.5-16 GHz, and in this band the peak gains are all over 19 dBc and the axial ratio is better than 3 dB. In addition, the aperture efficiencies are more than 50% in the band from 12 to 15.5 GHz, especially the efficiency at 13 GHz reaches a highest value of 61%. The good performances indicate that the proposed high-gain antenna has a highly promising application in portable communication systems.

Millimeter Wave Fabry-Perot Resonator Antenna Fed by CPW with High Gain and Broadband

A novel millimeter wave coplanar waveguide (CPW) fed Fabry-Perot (F-P) antenna with high gain, broad bandwidth, and low profile is reported. The partially reflective surface (PRS) and the ground form the F-P resonator cavity, which is filled with the same dielectric substrate. A dual rhombic slot loop on the ground acts as the primary feeding antenna, which is fed by the CPW and has broad bandwidth. In order to improve the antenna gain, metal vias are inserted surrounding the F-P cavity. A CPW-to-microstrip transition is designed to measure the performances of the antenna and extend the applications. The measured impedance bandwidth ofS11less than −10 dB is from 34 to 37.7 GHz (10.5%), and the gain is 15.4 dBi at the center frequency of 35 GHz with a 3 dB gain bandwidth of 7.1%. This performance of the antenna shows a tradeoff among gain, bandwidth, and profile.

Ultra-thin broadband flat metasurface to focus electromagnetic waves and its application in high-gain antenna

The phase gradient metasurface has strong abilities to manipulate electromagnetic waves on a subwavelength scale and has a potential to enhance the antenna gain. Based on the single multi-resonance metallic patch srtucture, we propose a new kind of ultra-thin broadband unit cell to manipulate electromagnetic waves and enhance the gain. It has been demonstrated that anomalous reflection can be achieved by utilizing the magnetic resonance between metallic patch and ground plane. Moreover, it is believed that resonance with low quality factor (Q factor) is useful in extending the working bandwidth. In order to extend the bandwidth of phase modulation, it is necessary to design a kind of low-Q unit cell. Besides, we need to extend the phase shift to cover the entire range [0, 360] to achieve the focusing effect. Thus we design a suitable symmetrical unit cell composed of ring and cross metallic patterns to control the phase of reflected waves. The symmetrical structure is useful for decreasing the Q factor so as to get a kind of low-Q unit cell. Theoretically, ring and cross metallic patch can be regarded as multi-resonance unit cells, which can cover the entire scope [0, 360]. The unit cell operates at 15-18 GHz with a thickness of 1 mm and the sides of 0.3 0( 0=20 mm). Furthermore, we design a phase gradient metasurface composed of the designed unit cell to verify the broadband anomalous reflection and focusing effects in CST Microwave Studio; the effect can be clearly illustrated in the simulation results obtained at 15-18 GHz. Due to the successful conversion from plane wave to quasi-spherical wave, we can place the Vivaldi antenna at the focal point of the metasurface as a feed source to transform the quasi-spherical wave to plane wave to enhance antenna gain. The simulation results are in good agreement with the theoretical analysis. Meanwhile, the designed metasurface and Vivaldi antenna have been fabricated and applied to enhance the gain of Vivaldi antenna. Both simulation and test results show that the peak gain has been averagely enhanced by 11 dB during the -1 dB gain bandwidth of 15-18 GHz and the fractional bandwidth is 18.2%. Moreover, due to the thin thickness, light weight and broad band, the designed unit cell may open up a new route for the applications of phase gradient metasurfaces in the microwave band region, and may also used as an alternative of high-gain antenna.

A novel broadband reflectarray antenna with lattice stubs on square element for Ku‐band application

ABSTRACTIn this article, a single layer unit cell reflectarray antenna comprising a fixed square patch to which is attached a lattice of symmetric open ended stubs is proposed. The phase response of the proposed unit cell element is governed by the length of the lattice, providing more than 600° of reflection phase variation. The unit cell element of 0.54λ0 × 0.54λ0, has a thin dielectric substrate thickness of 0.036λ0 and is placed above an air layer making the overall unit cell thickness of 0.126λ0. A 15 × 15 elements Ku‐band reflectarray antenna is designed with an area of 18 × 18 cm2. The reflectarray is center fed by a linearly polarized pyramidal horn antenna. The planar reflectarray antenna is fabricated and has wide −1 dB gain bandwidth, about 20% covering 12.1–14.8 GHz. The measured antenna gain at 13.5 GHz is 25 dB which is equivalent to 39% efficiency. The proposed unit cell and the reflectarray antenna are simulated through CST and HFSS software packages. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2699–2702, 2015

Wideband gain enhancement of slot antenna using one unprinted dielectric superstrate

A quarter-wavelength-thick unprinted dielectric slab is placed above a slot antenna to achieve high gain with a large bandwidth. By optimally truncating the high-permittivity superstrate to a small area of 2.25λ0 2, 8–10 dB enhancement in the directivity of the slot is achieved over a 3 dB directivity bandwidth of 16–18%. A prototype antenna was fabricated and tested at 11.5 GHz. Its measured peak gain is 16.95 dBi and the 3 dB gain bandwidth is 16.25%. The proposed antenna is simple and, more importantly, has a lower profile with a total height of 0.593λ 0.

Wideband 60 GHz circularly polarised stacked patch antenna array in low‐temperature co‐fired ceramic technology

A wideband circularly polarised (CP) cross-aperture-coupled stacked feed antenna array with the top-metal strip via fence based on multilayer low-temperature co-fired ceramic technology is designed and measured for 60 GHz wireless communication applications. The influence of the large substrate and ground size on the radiation patterns of the proposed CP antenna array is investigated. Considering the 10 dB impedance bandwidth, 3 dB axial ratio bandwidth and 3 dB gain bandwidth, the measured results reveal that a wide operating bandwidth more than 17% at the centre frequency of 61.75 GHz from 56.5 to 67 GHz of the presented CP antenna array is achieved.

A Wideband High-Gain High-Efficiency Hybrid Integrated Plate Array Antenna for V-Band Inter-Satellite Links

A wideband high-gain high-efficiency hybrid integrated plate array antenna for inter-satellite links is presented in this paper. This antenna consists of microstrip patches, substrate integrated waveguide (SIW) and waveguide power dividers. A novel feeding structure is proposed to excite the microstrip sub-array with a wideband characteristic. The radiation efficiency of SIW arrays with different sizes is compared by experiment. The hybrid SIW-waveguide feeding topology is optimized to realize high efficiency, low cost and compact configuration at the same time. The array antenna is fabricated through standard multi-layer PCB process and milling technology. Measured results demonstrate about 14.6% of reflection coefficient bandwidth ( |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |<;-10 dB) in the frequency band of 57-66 GHz. The gain fluctuates less than 3 dB within the same band. The 1 dB gain bandwidth is 8.1% within the frequency band of 59-64 GHz. The maximum gain is 39.2 dBi at 59 GHz with the efficiency of 41%.

Single-Layer Wideband Circularly Polarized Patch Antennas for Q-Band Applications

In this communication, dual-fed wideband circularly polarized (CP) patch antennas based on the single-layer printed circuit board (PCB) process and the substrate integrated waveguide (SIW) technology are proposed. Firstly, a patch antenna fed by an SIW coupler is developed to achieve a measured 3 dB axial-ratio (AR) bandwidth of 21% (from 38 GHz to 47 GHz). Then, by introducing second-order inductive windows, an improved CP patch antenna is developed. The measured results show that the 1 dB gain bandwidth is expanded from 3 GHz to 9 GHz while the overlapped bandwidth of AR and reflect coefficient is maintained. Finally, a 2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex> </formula> 2 CP array is developed with a dual-polarized patch array. By carefully selecting the resonant frequency of the patches, a wide gain bandwidth is achieved. Moreover, by compensating the major error that deteriorates the AR bandwidth with a specially-designed coupler, the measured 3 dB AR bandwidth reaches as wide as 22.8%. The measured peak gain is 12.35 dBi.