dB Axial Ratio Bandwidth Research Articles

Circularly Polarized Polarization Conversion Metasurface-Inspired Antenna Array With Low RCS Over a Wide Band

A circularly polarized (CP) metasurface-inspired antenna array with low radar cross section (RCS) over a wideband based on polarization conversion metasurface (PCM) is proposed. Without increasing the structural complexity, the PCM units serve directly as antenna radiators, which not only maintains good radiation characteristics but also reduces both the in-band and out-of-band RCS of the antenna. Simulations show that the proposed PCM-inspired antenna array has an impedance bandwidth of 37.6% (8.2 to 12 GHz), a 3 dB axial ratio (AR) bandwidth of 32.5% (8.5 to 11.8 GHz), and a 3 dB gain bandwidth of 23.3% (9.5 to 12 GHz). The RCS of the proposed antenna array is greatly reduced for both polarizations in the frequency range of 7.6 to 16.2 GHz (72.3%) compared to conventional microstrip patch antenna array, with a maximum reduction of 20.6 dB. Moreover, the proposed PCM-inspired antenna array has a smaller element size compared to conventional low-RCS metasurface antennas, making it more conducive to the composition of a phased array. Finally, the proposed array is fabricated and measured, and the results confirm the simulations.

A frequency‐ and polarization‐reconfigurable cross dipole antenna using liquid metal

AbstractA frequency and polarization reconfigurable wideband cross‐dipole antenna is proposed. A /4 phase‐shifted ring structure is used to design a reconfigurable frequency and polarization wideband antenna, which is connected to the dipole arm with the liquid metal as a parasitic branch. The antenna consists of a pair of rectangular dipoles, a pair of curved phase‐shifted rings, and a square ring. Two mutually perpendicular rectangular dipole arms are connected by a phase‐shifted ring, which is printed on the upper and lower surfaces. The left‐hand circular polarization and right‐hand circular polarization can be switched by loading liquid metal at different positions of the antenna, and the frequency can be reconstructed by adjusting the length of liquid metal at corresponding positions. The total 3 dB axial ratio bandwidth are 41.27% (1.50–2.28 GHz) and 43.57% (1.49–2.32 GHz), and eight adjustable circularly polarized frequency bands can be obtained at the same time. To verify the proposed design, a reconfigurable antenna is fabricated and measured. The measured results are in good agreement with the simulated results.

A Wide-Band Antenna with Circular Polarization Utilizing a U-Shaped Radiator and Parasitic Strip for Wireless Communications.

A circularly polarized (CP) and wide-band monopole antenna with a miniaturized size is suggested in this study. The suggested structure is composed of a U-shaped radiator on the front side, a partial ground plane with two rectangle slots, and a quadrilateral-shaped parasitic strip on the back side of the FR4 substrate. A wide-band operation with S11 ≤ -10 dB was achieved by regulating the radiator and the partial ground that was placed on the second side of the antenna substrate. The CP was achieved when excited two modes with the same amplitude and a 90° phase difference. This could be generated by regulating the slots' dimensions in the ground plane. Moreover, a quadrilateral-shaped parasitic strip placed on the second side with the partial ground was utilized to extend the 3 dB axial ratio (AR) bandwidth. The suggested structure is simulated, prototyped, and measured to confirm the desired requirements with a total size of 30 × 32 mm2 (0.4 × 0.42 λ0 at 4 GHz). The tested outcomes have a bandwidth of S11 ≤ -10 dB (81.25%) (5.2 GHz, 3.8-9 GHz) and a 3 dB axial ratio (AR) bandwidth (30.7%) (1.63 GHz, 4.48-6.11 GHz). The antenna's different parameters are discussed, which recommend the suggested antenna to be used in UWB, sub 6 GHz, and WLAN wireless applications.

Circular Polarized Antenna with Rotationally Positioned Microstrip Structures For UHF RFID Applications

With the use of wireless communication and the industry 4.0 revolution, RFID technology integration in production has increased. The large-scale preference of RFID systems is both cost-effective and significantly increasing production. It is an innovation that provides convenience for large production facilities such as product control, in-plant tracking, storage, inventory operations. In this paper, a compact circularly polarized (CP) reader antenna is presented for ultra-high frequency (UHF) radio frequency identification (RFID) applications. The proposed antenna consists of a circularly slotted ground plane and folded plus-shaped structures with vertical and horizontal positions. Microstrip line feeding technique is used in the vertically folded plus-shaped structure positioned on the front surface. The antenna has a 10 dB return loss bandwidth of 80 MHz (840-920) and a 3 dB axial ratio bandwidth of 20 MHz (855-875). Theproposed antenna has dimensions of 75 × 75 × 1.6 mm3 . The size advantage of the single-layer and singlefed structure enables its applicability in portable systems.

Flexible Antenna with Circular/Linear Polarization for Wideband Biomedical Wireless Communication.

A wideband low-profile radiating G-shaped strip on a flexible substrate is proposed to operate as biomedical antenna for off-body communication. The antenna is designed to produce circular polarization over the frequency range 5-6 GHz to communicate with WiMAX/WLAN antennas. Furthermore, it is designed to produce linear polarization over the frequency range 6-19 GHz for communication with the on-body biosensor antennas. It is shown that an inverted G-shaped strip produces circular polarization (CP) of the opposite sense to that produced by G-shaped strip over the frequency range 5-6 GHz. The antenna design is explained and its performance is investigated through simulation, as well as experimental measurements. This antenna can be viewed as composed of a semicircular strip terminated with a horizontal extension at its lower end and terminated with a small circular patch through a corner-shaped strip extension at its upper end to form the shape of "G" or inverted "G". The purpose of the corner-shaped extension and the circular patch termination is to match the antenna impedance to 50 Ω over the entire frequency band (5-19 GHz) and to improve the circular polarization over the frequency band (5-6 GHz). To be fabricated on only one face of the flexible dielectric substrate, the antenna is fed through a co-planar waveguide (CPW). The antenna and the CPW dimensions are optimized to obtain the most optimal performance regarding the impedance matching bandwidth, 3dB Axial Ratio (AR) bandwidth, radiation efficiency, and maximum gain. The results show that the achieved 3dB-AR bandwidth is 18% (5-6 GHz). Thus, the proposed antenna covers the 5 GHz frequency band of the WiMAX/WLAN applications within its 3dB-AR frequency band. Furthermore, the impedance matching bandwidth is 117% (5-19 GHz) which enables low-power communication with the on-body sensors over this wide range of the frequency. The maximum gain and radiation efficiency are 5.37 dBi and 98%, respectively. The overall antenna dimensions are 25 × 27 × 0.13 mm3 and the bandwidth-dimension ratio (BDR) is 1733.

Wideband circular polarizer for a photoconductive antenna.

We report a thin-film circular polarizer consisting of three metal-grid layers to be used with a photoconductive antenna (PCA) to generate terahertz (THz) circularly polarized (CP) radiation. The polarizer has a high transmission with a measured 3 dB axial-ratio bandwidth of 54.7% from 0.57 to 1 THz. We further developed a generalized scattering matrix approach to provide insight into the underlying physical mechanism of the polarizer. We revealed that the Fabry-Pérot-like multi-reflection among gratings enables the high-efficiency polarization conversion. The successful realization of the CP PCA can find widespread application, such as THz circular dichroism spectroscopy, THz Mueller imaging, and ultrahigh-speed THz wireless communications.

Dual-band circularly polarized asymmetric dipole array antenna for GPS L1 and L2 bands

A dual-band, circularly polarized (CP) asymmetric dipole array antenna for Global Positioning System (GPS) applications with a wide beam is presented in this paper. The proposed antenna comprises two different-sized printed crossed dipoles with integrated baluns fed by an asymmetric feeding network to achieve dual-band functionality. Using two branch-line couplers with different dimensions in the feeding network performs Right-Hand Circular Polarization (RHCP) operation at GPS L1 and L2 bands. According to the experiments, the proposed antenna has wide impedance bandwidths of 24.82% (1139.5–1462.4 MHz) and 14.82% (1500.4–1740.5 MHz), and 3 dB Axial-Ratio (AR) bandwidth of 37.4% (1132.3–1653.2 MHz) to cover the GPS L1 and L2 bands. Furthermore, at 1227 MHz frequency, the antenna has a gain of 4.65 dBic, and a 3 dB AR beamwidth of 148.2° facing the sky. Also, at 1575 MHz frequency, a gain of 5.25 dBic and a 3 dB AR beamwidth of 139.3° are achieved.

A wideband flexible electro-textiles material linear-to-circular polarizing metasurface for S-band CubeSat

In this paper, a flexible linear-to-circular polarizer FSS-based surface made from a single layer of cloth is introduced. Two orthogonal strips serve as the foundation for the proposed structure's architecture, with a central aperture in the unit cell for the pico-satellites aimed towards the S-Band. A wearable material called Shieldit Super serves as the conducting fabric in the unit cell, while Felt serves as the substrate. For the working center frequency of 2.41 GHz, the unit cell size is 0.32λ × 0.26λ × 0.02λ. It has a 3 dB axial ratio bandwidth (ARBW) of 42.90% and an axial ratio of 0.08 dB at 2.41 GHz, which is very close to zero. In addition, the FSS metasurface provides a bandwidth of up to 56.84% with 90% conversion efficiency. The polarizing surface is then created by multiplying this unit cell by a 6 × 6 array. The proposed structure's performance is proven by placing it in front of a patch antenna operating at 2.41 GHz. In addition to efficiently converting linearly polarized waves into circularly polarized waves, the antenna's performance improved when paired with the polarizing surface, as measured by the realized gain, which went from 3.14 dBi to 7.33 dBi.

Circularly Polarized Metasurface Phased Array Antenna System With Wide Axial-Ratio Beamwidth for LEO Mobile Satellite Communication

In this paper a millimeter waves LHCP 1×32 with dummy on both sides phased array antenna is proposed. Multi-layer structure and single feed are employed. The antenna patch adopts 3×3 metasurface. The measured impedance bandwidth is 20%, ranging from 22.5 to 27.5 GHz. The axial ratio bandwidth with an axial-ratio (AR) level < 3 dB achieves 3.35 GHz ranging from 24.15 GHz to 27.5 GHz. Relative 3 dB axial ratio bandwidth reaches 13.4%. A total of 37 beams were measured in the anechoic chamber. The results show that whether the phased array antenna system serves as transmitter or receiver, the 3dB beam angle coverage at 26 GHz reaches -42°-45° at φ= 0° and -42°-42° at φ= 90°. The 3 dB axial ratio beam angle ranges from -80° to 89° at φ= 0°, and from -45° to 45° at φ= 90°. Based on this linear array, it is easy to expand to circular polarization planar wide-angle scanning phased array. The antenna system realizes circular polarization with wide angle wide axial ratio beam scanning, which can be used in LEO satellite communication system.

A Ku Wideband Circularly Polarized Microstrip Antenna Array with Low Profile Crossed-Dipole Element

This paper presents a novel Ku wideband circularly polarized (CP) antenna array composed of crossed-dipole element (CDE) and fed through sequential rotation (SR) feeding technique. Unlike the traditional CP-CDE fed by coaxial cable that usually works at low frequencies, the proposed CDE consists of two orthogonal heart-shaped patch dipoles that can work at frequencies as high as Ku-band, at the same time achieving a larger bandwidth. A feeding structure is proposed without welding, so potential errors in the antenna assembly process can be mitigated. A 2 × 2 CP antenna array with wideband SR feeding network is designed based on the CDE to further expand the axial ratio (AR) bandwidth. The designed antenna array is fabricated using the multilayer printed circuit board (PCB) technology and measured in anechoic chamber using the planar near-field measurement facility. The measured results show that −10 dB impedance bandwidth of 44% (11.6–18.15 GHz) along with 3 dB AR bandwidth of 38.7% (12–17.65 GHz) and 3 dB gain bandwidth of 34.6% (12.2–17.3 GHz) as well as 11.02 dBic peak gain have been achieved while maintaining a lower profile.

Circularly polarized stub-loaded annular ring patch antenna for 2×2 MIMO satellite application

In this article, a stub loaded circularly polarized annular ring patch antenna which operates at 3–5 GHz band for 2×2 MIMO Satellite application is proposed. The evolution of antenna begins with a conventional annular ring patch antenna, addition of diagonal slots and integrated with λ/2 hair pin stub loaded annular ring patch to improve isolation and circular polarization. The antenna isolation is a critical parameter and important requirement of MIMO system. In satellite communications, circular polarization is used to improve the quality and reliability of the communication link between the satellite and the ground station. The antenna achieves circular polarization and mutual coupling through diagonal slots and stub-loaded design without any additional decoupling techniques. The overall size of the proposed MIMO antenna is 63 × 63 × 1.52 mm3 which is fabricated over Rogers RO3003 substrate. The proposed antenna design is simulated, fabricated, tested and analyzed for various parameters such as Reflection coefficient,Isolation Gain, radiation pattern, Axial ratio (AR), Envelope correlation coefficient (ECC), Diversity gain (DG), Channel capacity (CC) and total efficiency. The isolation of <−22 dB, gain of 7.1 dB, axial ratio<3 dB, diversity gain of 9.9 dB, ECC<0.002,CC of 11.23bps/Hz and efficiency>95% are obtained. The measured 10 dB impedance bandwidth of 270MHz and 3 dB AR bandwidth of 250MHz in the desired band are achieved. The simulated and measured antenna parameters are agreeable with each other. The results are found to be promising and having high potential in the 5G and Satellite MIMO.

Phase and Polarization Digitally Modulated Array Using Reconfigurable DR Element: Proposal, Design, and Verification

The proposal, design, and verification of a phase and polarization digitally reconfigurable / modulated array using the reconfigurable dielectric resonator (DR) elements are developed in this paper. Different from the conventional phased arrays and reconfigurable antennas, the radiated electromagnetic (EM) wave can be flexibly controlled by simultaneously modulating its phase and polarization. To realize phase switching, a clever 1-bit phase shifter (0° / 180°) is introduced in the element design. The polarization states are controlled by integrating the switch-loaded feeding structure. And a compact 2-bit polarization tuner (0°-LP, 90°-LP, RHCP, and LHCP) is finally realized. Since every element can realize 1-bit phase and 2-bit polarization switching, the far-field beams and polarization types of the array format can be arbitrarily modulated by designing the coding sequence. To verify the proposed working principle, a compact reconfigurable metasurface-loaded DR element, and a four-element digitally reconfigurable linear array are implemented, respectively. The overlapped -10 dB impedance and 3 dB axial ratio bandwidths are 2.35-2.55 GHz (12.5 %) and 2.42-2.48 GHz (2.4 %), respectively (Covering 2.40 GHz WIFI / BT band). More importantly, it can achieve 16 different beam & polarization modes. The proposed antennas exhibit a low-cost, compact size, good bandwidth, and flexible radiation modulation capacity. They are promising candidates for future smart antennas to manipulate and control electromagnetic (EM) waves.

A Simple Frequency- and Polarization-Reconfigurable Bent Monopole Antenna Based on Liquid Metal

In this letter, a frequency- and polarization-reconfigurable bent monopole antenna using liquid metal is proposed. The proposed antenna is designed to operate at continuously tunable frequencies and switch between left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) states. The frequency reconfigurability is achieved by controlling the length of the liquid metal to change the electrical length of the antenna. The circularly polarization can be achieved by injecting from the inlet, and excited by orthogonal horizontal radiation as well as vertical radiation. 3 dB axial ratio bandwidth of 37.5%(3.12–4.63 GHz) in LHCP state and 48.8% (3.07–5.05 GHz) in RHCP state can be achieved. The whole antenna is characterized by continuous tunability, reconfigurable frequency and polarization, and wide tunable bandwidth. The measured results of constructed prototypes are in close agreement with the simulation results, and its feasibility is fully proved.

Broadband and high gain circularly polarized mushroom‐loaded nonuniform patch array antenna with aperture CPW feed

AbstractThe circularly polarized antenna with high gain and broad bandwidth in single layer substrate is realized with mushroom‐loaded nonuniform square patches and aperture CPW feed for 5 GHz Wi‐Fi applications. An array of nonuniform square patches are excited by using a uniform aperture CPW feed. Moreover, the mushrooms are connected between the patches and the ground plane to reduce the spurious radiations on the patch. Mushrooms are moved in the diagonal direction of patches to generate circular polarization. The dimensions of the middle patches are increased and the mushrooms of the middle patches are moved further in the diagonal direction to enhance the impedance bandwidth (IBW) and 3 dB axial ratio bandwidth (ARBW). An array of mushroom‐loaded nonuniform square patches with aperture CPW feed has achieved an IBW of 54.2% (4.76–8.3 GHz), an ARBW of 14.3% (5.49–6.29 GHz) and the peak gain of 9.5–9.9 dBi over 5 GHz Wi‐Fi band.

Compact Circularly Polarized Monopole Antenna Using Characteristic Mode Analysis

This study aims to design a circularly polarized compact antenna using characteristic mode analysis (CMA). The proposed antenna consists of a substrate with a slotted annular ring-shaped patch and partial ground. The excitation position of the antenna and its optimal dimensions are determined through the analysis of different operation modes with CMA. After that, an optimized antenna is designed, and an antenna prototype is fabricated for validation. The experimental results show that the reflection coefficient achieves a -10dB impedance bandwidth of 6.85 GHz, a 3dB-axial ratio bandwidth of 0.7 GHz, and a peak gain of 3.2 dBi. These characteristics agree with simulations and make the circularly polarized compact antenna suit for C-band and sub-6 GHz 5G wireless applications.

Single-fed broadband CPW-fed circularly polarized implantable antenna for sensing medical applications.

Biomedical telemetry relies heavily on implantable antennas. Due to this, we have designed and tested a compact, a circularly polarized, a low-profile biomedical implantable antenna that operate in the 2.45 GHz ISM band. In order to keep the antenna compact, modified co-planar waveguide (CPW) technology is used. Slotted rectangular patch with one 45-degree angle slot and truncated little patch on the left end of the ground plane generate a frequency-range antenna with circular polarization. Using a 0.25-millimeter-thick Roger Duroid-RT5880 substrate with a thickness of εr = 2.2, tanδ = 0.0009 provides flexibility. The volume of the antenna is 21 mm x 13.5 mm x 0.254 mm (0.25λg × 0.16λg × 0.003λg). The antenna covers 2.35-2.55 GHz (200 MHz) in free space and 1.63-1.17 GHz (1.17 GHz) in epidermal tissue. With skin tissue that has more bandwidth, the (x and y)-axis bends of the antenna are also simulated via the simulation. Bended antenna simulations and measurements show excellent agreement. At 2.45 GHz, the skin-like gel had -10dB impedance and 3dB axial ratio (AR) bandwidths of 47.7 and 53.8%, respectively. The ultimate result is that the SAR values are 0.78 W/kg in skin over 1 g of bulk tissue, as determined by simulations. The suggested SAR values are lower than the FCC's maximum allowable limit (FCC). This antenna is small enough to be implanted in the body, making it perfect for biomedical applications.

Circular polarization-agile and beam switching enabled reconfigurable cavity-backed antenna

In this paper, a circular polarization-agile and beam switching enabled reconfigurable cavity-backed antenna having the ability to steer its radiation beam in different directions is presented. The antenna consists of two E-shaped driven patches, a tunable phase shifter integrated with PIN diodes for pattern switching and four switchable feeding probes for implementing polarization agility. The proposed antenna can simultaneously change its polarization and pattern. Beam switching and polarization agility are independently controlled by altering the OFF-ON states of diodes loaded on the feed network and switchable feeding probes. For validity of the proposed concept, the antenna prototype is fabricated and tested. The proposed antenna has measured impedance bandwidth (S11 < -10 dB) and 3 dB axial ratio bandwidths of 23% and 17.4% respectively for all states over the frequency range 4.7–5.6 GHz. The measured and simulation results show that the antenna can scan up to ± 30° with five reconfigurable beams and two polarizations states for each reconfigurable beam.

Pentaband Dual-Polarized Antenna for Multiservice Wireless Applications

This paper presents a novel design for and an experimental study of a dual-polarized quad-port MIMO antenna. The design achieves resonance at five distinct frequency bands with reduced mutual coupling. The design includes a single annular ring slot, four truncated rectangular corners, and a truncated aperture to improve resonance behavior. The design is then extended to a four-port MIMO antenna by including a ground-plane slit to enhance isolation between antenna elements at the center resonance band. The antenna achieves resonances at 5 distinct bands, ranging from 1.5 to 8.4 GHz, with significant mutual coupling reductions. The resonances of the quad-port pentaband MIMO antenna are achieved at 1.55 GHz (1.5–1.65 GHz), 2.5 GHz (2.4–2.7 GHz), 5.2 GHz (5–5.85), 7.3 GHz (7.1–7.4), and 8.15 GHz (7.9–8.4), with respective mutual coupling reductions of 27 dB, 37 dB, 21 dB, 29 dB, and 21 dB. Additionally, the 3 dB axial ratio bandwidth (ARBW) is observed at 6.5% (1.5–1.6 GHz) and 15% (2.4–2.7 GHz) in 2 distinct bands, and the envelope correlation coefficient and diversity gain are calculated within the specified band range. Experimental measurements of the prototype for the quad-port antenna are conducted, with excellent agreement found between the results and the simulations.

A broad axial ratio bandwidth and wide angle coverage circularly polarized monopole antenna for wireless communication

AbstractA uniquely shaped layout of a wideband circularly polarized (CP) printed monopole antenna is planned in this article. The proposed antenna comprises a 7‐shaped slotted radiating patch, tapered feed line, and modified partial ground plane. Multiple parasitic strips are employed at optimum positions on the ground and radiating planes to improve the axial ratio bandwidth (ARBW). The electrical dimension of the designed antenna is . The confirmed −10 dB impedance bandwidth (IBW) and 3 dB ARBW are 11.86 GHz (3.14–15 GHz), 130% and 6.32 GHz (4.04–10.36 GHz), 87.78% along with coverage angle. The proposed antenna is suitable for different applications in communication systems such as WLAN, WiMAX, FM CW altimeter, and satellite for C‐ and X‐ band.

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves.

A terahertz flexible metamaterial quarter-wave plate (QWP) is designed and fabricated using polyimide as the substrate in this paper, with a 3 dB axial ratio bandwidth of 0.51 THz and high polarization conversion efficiency and transmittance. The effect of the incidence angle on the polarization conversion performance of the QWP is discussed by measuring the transmissions at multiple incidence angles. The blocking effect of this QWP combined with a polarizer on the backward reflection of terahertz waves is investigated by terahertz time-domain spectral transmission experiments. By adjusting the angle of the QWP and polarizer with respect to the incident light in the optical path, a blocking efficiency of 20 dB can be achieved at a 20° incidence angle, with a bandwidth of 0.25 THz, a maximum blocking efficiency of 58 dB at 1.73 THz, and an insertion loss of only 1.4 dB. Flexible terahertz metamaterial QWPs and polarizers can effectively block harmful reflected waves in terahertz communication and other systems. They have the advantages of a simple structure, ultra-thinness and flexibility, easy integration, no external magnetic field, and no low-temperature and other environmental requirements, thus having broad application prospects for terahertz on-chip integrated systems.