dB Axial Ratio Bandwidth Research Articles

A compact TM03 mode penta‐polarization agile MSA for interference mitigation in 5G ultra‐dense point to point environment

Signal interference in the recent 5G ultra-dense environment is becoming severe due to the co-existence of large RF nodes operating in the constrained spectrum. In this article, a polarization agile approach for the designing of an RF system is studied to mitigate interference issues besides the communication and signal processing approach. A compact single-fed single layer penta-polarization agile higher-order microstrip patch is analyzed probably for the first time in the literature. The proposed antenna possesses a very low profile of less than 0.01 λ (λ free-space wavelength). Reconfigurable orthogonal feeding with switches is connected with the horizontal and vertical patch edges. Subsequently, these are excited separately and simultaneously using switchable PIN diodes and appropriate bias networks to realize horizontal, vertical, and 45° slant polarization states. Successively, diagonal patch corners are truncated to initiate right and left-hand circular polarizations. Slots are etched on specific orientation of currents on the patch surface to improve side-lobe levels. A prototype is analyzed, simulated, and fabricated at TM03 mode and operating at 5.8 GHz band with penta-polarization agility. A consistent 11 dBi realized broadside gain is measured covering the 10 dB reflection loss and 3 dB axial ratio bandwidth in both the principal planes.

Increasing the Gain of Beam-Tilted Circularly Polarized Radial Line Slot Array Antennas

This article presents a new type of beam-tilted circularly polarized (CP) radial line slot array (RLSA) antennas. When the conventional beam tilting method is applied to CP-RLSA antennas, the aperture efficiency of the antenna degrades significantly due to very sparse slots in some parts of the antenna. A new method is presented to prevent this, and hence a much higher gain and aperture efficiency are achieved from the same antenna area. The key to the new method is an aggressively biased truncation of the slot layout that leaves out sparse slots. Consequently, the feed point moves closer to an edge of the TEM waveguide. A reflecting wall is introduced to prevent leakage from this edge. It is shown that the gain of RLSAs with beams tilted to 25° and 45° (measured from normal direction) can be increased by 5.5 dB (from 20.5 to 26 dBic) using the new method as opposed to the conventional method. The new concept and predicted results are validated using a prototype antenna with the beam-tilted to an angle of 25°. The aperture diameter and overall thickness of the prototype are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12\lambda _{0}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.4\lambda _{0}$ </tex-math></inline-formula> , respectively, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the operating frequency of 18 GHz. The measured results confirmed a higher gain of 26.2 dBic, an aperture efficiency of 30%, the overall efficiency of 93.2%, and sidelobe levels (SLLs) less than −25 dB at 18 GHz. The measured 10 dB return loss bandwidth of the antenna is greater than 63.7%, 3 dB axial-ratio bandwidth is 13.3%, and 3 dB gain bandwidth is 6.7%.

Dual-Band Circularly Polarized Hybrid Dielectric Resonator Antenna for 5G Millimeter-Wave Applications

This paper proposes a dual-band circularly polarized (CP) rectangular dielectric resonator antenna (DRA) for 5G millimeter wave wireless communications. The proposed DRA consists of a novel modified cross-flower exciting (MCF) slot and a rectangular ceramic dielectric resonator (DR). With the help of the compact MCF feeding slot, the fundamental modes TEδ11x/TE1δ1y and higher-order modes TEδ13x/TE1δ3y of the DR can be excited to achieve CP dual-band characteristics. In addition, the MCF slot works as a radiator at 26 GHz and 39 GHz to enhance the DRA bandwidth. More importantly, these two operational bandwidths can be controlled independently at the lower and upper bands. The proposed DRA is designed, fabricated and measured. The measured results show that the proposed dual-band CP DRA achieves 3 dB axial-ratio (AR) bandwidths of 19.8% and 7.8% with peak gains of 5.62 dBic and 6.74 dBic for the lower and upper bands.

Dual-Band Textile Antenna With Dual Circular Polarizations Using Polarization Rotation AMC for Off-Body Communications

A dual-circular polarization (CP) textile antenna is investigated for wearable applications at 3.5 GHz WiMAX and 5.8 GHz industrial, scientific, and medical bands. The proposed antenna is composed of a dual-band monopole antenna and a polarization rotation artificial magnetic conductor (PRAMC). Through the PRAMC, the dual-CP radiation is enabled and the backward radiation is alleviated, in which the left-handed CP is generated in the lower band and the right-handed CP is realized in the upper band. Notably, dyadic reflection coefficient analysis is employed to understand the operating mechanism. Both monopole and PRAMC are printed on textile substrate, achieving conformability and comfortability. In addition, numerical results indicate that the performance of the antenna is robust to lossy human body and structural deformations. For verification, the prototype of the antenna was fabricated by two types of manufacturing process (i.e., laser cutting and screen printing), and the advantages and drawbacks of each fabricating approach are discussed for referring. The antenna made by laser cutting was tested on the phantom with the −10 dB impedance bandwidths of 11.7% and 9.1%, the 3 dB axial ratio bandwidths of 2.0% and 8.2%, and the peak gains of 6.6 and 7.2 dBic, in dual bands, respectively.

Implementing the single/multiport tunable terahertz circularly polarized dielectric resonator antenna

A tunable terahertz circularly-polarized dielectric resonator antenna is implemented and numerically studied. An aperture coupled terahertz rectangular dielectric resonator antenna operating with the fundamental magnetic dipole is designed. The modal field distribution is perturbed using the material-perturbation technique and the electric field vectors are aligned in the horizontal plane with their orthogonal components having quadrature phase difference between them. Consequently, the circular polarization is obtained in the operating passband. The proposed antenna provides the 10-dB impedance bandwidth of 12.94% (4.27–4.86 THz) and 3 dB axial ratio bandwidth of 3.77% (4.43–4.60 THz). Moreover, tunability is achieved by modulation in the chemical potential of graphene layer coated at the top of the dielectric resonator by applying an electrostatic bias voltage. In addition, antenna provides the gain of 6.45 dBic along with 98% radiation efficiency. The proposed antenna can also be used for the implementation of multi-port wireless THz communication systems with the advantage of tunable CP response with impeccably high radiation performance parameters. A two-port multi input, multi output (MIMO) antenna is implemented with the usage of the proposed metal strip coated DR. This antenna provides high isolation between both the ports along with polarization response and pattern diversity with the acceptable value of MIMO performance parameters like envelop correlation coefficient and diversity gain.

Circularly Polarized Antenna Array With Suppressed Sidelobes for Electronic Toll Collection

In this letter, a 4×4 circularly polarized antenna array with suppressed sidelobes for electronic toll collection applications is proposed. The antenna array operates at 5.8 GHz and is designed based on the weighted constrained method of the maximum power transmission efficiency (WCMMPTE). Different constraints to control the polarization and sidelobe levels are simultaneously introduced to realize the desired polarizations and sidelobe levels. While the optimized distribution of excitations for the 4×4 antenna array is first obtained analytically by the WCMMPTE, a few elements with negligible exciting amplitudes are then removed to reduce the array size to yield a 12-element array together with a feeding network which are fabricated and tested. The measured results indicate that the fabricated array has a left-hand circular polarization gain of 15.3 dBi with sidelobe levels below –30 dB and half-power beamwidths of 30° in both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϕ</i> = 0° and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϕ</i> = 90° planes, which meet the requirements of ETC system. Moreover, a 3 dB axial ratio bandwidth of 720 MHz and a low axial ratio of 0.3 dB at 5.8 GHz have been achieved, which demonstrate a good circular polarization performance.

Circularly polarized rectangular dielectric resonator antenna with metallic strips load for WLAN application

AbstractThis article presents a circularly polarized rectangular dielectric resonator antenna (CP RDRA) loaded with metallic strips. The dielectric resonator (DR) with metallic strips on the top surface is excited by a slot aperture feed that excites two orthogonal modes to provide circular polarization. The proposed CP RDRA does not require any complex‐shaped dielectric resonator and simplifies the overall design. A prototype of the proposed antenna has been fabricated and validated. It has measured impedance bandwidth between 4.8 and 5.6 GHz and 3 dB axial ratio bandwidth between 5.1 and 5.43 GHz. The axial ratio beamwidth of more than 155° in the XZ and YZ planes is obtained.

A New Observation in Spiral and Curl Antenna Configurations above the Ground Plane

We report here that spiral and curl antennas are essentially the same when using the moment method. This aids in the understanding and design of the two antennas, and serves as the groundwork for new ideas regarding antennas. First, the spiral antenna height above the ground plane was gradually reduced, and at each height, the spiral configuration parameters were optimized for an axial ratio of less than 0.1 dB. It was found that the spiral antenna had configuration parameters almost the same as those for a curl antenna at a height of 0.15 wavelengths. Next, the curl antenna was analyzed with a reduced height. The antenna, at a height of 0.10 wavelengths, showed a 3 dB axial ratio bandwidth of 3%, with a VSWR of less than two. The analysis results are verified with experimental results.

Single-Element and MIMO Circularly Polarized Microstrip Antennas with Negligible Back Radiation for 5G Mid-Band Handsets.

In this paper, single-element and MIMO microstrip antenna with two pairs of unequal slits is proposed as a circularly polarized antenna with negligible back radiation for 5G mid-band handsets. The unequal pairs of slits are engraved on the antenna patch to guarantee the presence of the circular polarization (CP). The proximity-coupled feeding technique is used to excite the proposed microstrip antenna in order to provide larger antenna −10 dB bandwidth which approaches 10.8% (3.48–3.87 GHz). A novel analysis technique is proposed in this paper that demonstrates the 3D axial ratio pattern in order to generate CP in the broadside direction without affecting the structure of the ground plane which ensures weak back radiation. The 3 dB axial ratio bandwidth (ARBW) is found to be equal to 4.1% extended along the range (3.58–3.73 GHz). To make the design more compatible with the 5G mid-band handsets, the 2 × 2 MIMO structure of the proposed antenna with reduced mutual coupling (less than −20 dB) is also presented in this work. The simulation and measured results are in good agreement, and both verify the CP characteristics and the weak back radiation of the proposed antenna.

Quad-Band Circular Polarized Antenna for GNSS, 5G and WIFI-6E Applications

A quad-band circularly-polarized antenna, for applications of a global navigation satellite system (GNSS), 5G, and WIFI-6E, is designed, fabricated, and measured. The proposed antenna is formed by an L-shaped radiator, a rectangular frame ground with an L-shaped stub, and a rectangular strip at the opposite corner. The microstrip antenna can generate four frequency bands, covering WIFI-6E (5925–7125 MHz), 5G n77 (3300–4200 MHz), n78 (3300–3800 MHz), and the GNSS bands. This antenna generates right hand circular polarization (RHCP) waves in the low frequency band (0.95–2.11 GHz), covering GPS, BDS, GLONASS, and GALILEO applications. Moreover, an L-shaped aperture and three rectangular slits are cut on the ground to broaden the axial-ratio bandwidth at the upper band. A prototype is fabricated and measured to verify the performance of this design. It is shown that the agreement between the simulation and measurement is satisfactorily good. The measured −10 dB bandwidths for each band are 75.8% (0.95–2.11 GHz), 55.8% (3.05–5.39 GHz), 39.9% (5.84–8.19 GHz) and 10.3% (9.14–10.68 GHz), respectively. While the measured 3 dB axial-ratio bandwidths are 59.4% (1.16–2.14 GHz), 35.8% (3.23–4.64 GHz), 8.4% (5.70–6.20 GHz), and 2.6% (7.51–7.71 GHz), the measured gains are 4.56, 2.28, 4.26, and 4.30 dBi at 1.5 GHz, 3.8 GHz, 6 GHz, and 7.6 GHz, respectively.

A novel broadband circularly polarised waveguide slot array antenna with a wide axial ratio bandwidth

In this study, a novel broadband circularly polarised waveguide slot array antenna with a wide axial ratio bandwidth is designed. The circular polariser is excited by the waveguide radiation linear polarised antenna, whose end is bent by 90° and generates a circularly polarised electric field. The matching waveguide between the slot and the polariser improves impedance matching. Furthermore, the structure with the added waveguide changes waveguide impedance, which can be used to realise impedance matching, and reduces the spacing between the units. In this study, a 4 × 4 antenna array is fabricated. The measured results reveal that the array achieves −10 dB impedance bandwidth of 27% (11.15–14.63 GHz) and the 3 dB axial ratio bandwidth of 23% (11.48–14.52 GHz). An aperture efficiency higher than 71% is obtained, with the maximum gain of 22 dB. The antenna side lobes levels are less than −13 dB in the operating bandwidth.

A Wideband Circularly Polarized Complementary Antenna for Millimeter-Wave Applications

This work presents a design of an aperture-coupled complementary antenna for realizing circularly polarized (CP) broadside radiation at millimeter-wave (mm-wave) frequencies. The proposed antenna constructively combines a patch dipole (electric dipole radiation) and a folded loop antenna (magnetic dipole radiation), which are differentially excited by a longitudinal slot etched on the top layer of the substrate integrated waveguide (SIW). The combination of the proposed patch dipole and the folded loop antenna results in a paralleled electric dipole and magnetic dipole which can generate two orthogonal electric field components and 90° phase difference in the far-field radiation when they are in-phase excited. The proposed antenna achieves a wide impedance bandwidth of 46% from 48.47 to 77.46 GHz and a wide 3 dB axial ratio bandwidth (ARBW) of 47.3% from 51.64 to 83.61 GHz with an overlapped bandwidth of 40%. To further enhance the antenna gain, sequential rotation technique is adopted to construct a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 2$ </tex-math></inline-formula> subarray, which is further employed in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \times 4$ </tex-math></inline-formula> subarray. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \times 4$ </tex-math></inline-formula> subarray is then used to construct an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> antenna array, which achieves a wide impedance bandwidth of 33.8% from 56.11 to 78.95 GHz and a wide 3 dB ARBW of 38.8% from 53.57 to 79.32 GHz, with a maximum antenna gain of around 25.2 dBic. The proposed antenna element and array design would be a competitive candidate for future wireless applications operating at mm-wave spectrum.

Circularly polarized parasitic patch slot antenna using I-tree fractal defected ground structure for CA band applications

Abstract In this article, a single feed antenna design which consists of a parasitic patch slot with an I-tree shaped fractal defected ground structure for circularly polarized radiation is presented. In the proposed design, circular polarization characteristics are achieved by deploying fractal slotted defected ground structures. The antenna design with a third iterative I-tree shaped fractal slot on an Fr4 substrate is fabricated and tested for verifying the simulated results. The circular polarization mechanism is performed using parametric studies. The measured and simulated results confirmed that the proposed structure can adequately generate an impedance bandwidth of 10.6% with 3 dB axial ratio bandwidth of 4.89%, with the measured peak gain of the proposed antenna being 5.16 dBic. The proposed article is suitable for C-band and CA-band applications.

Design and analysis of circularly polarized circular patch antenna with multiple shorting pins using characteristic mode theory

In this paper, we design a single-layer single-feed Circularly Polarized (CP) circular patch antenna with loading of shorting pins. At first, metallic pins are symmetrically placed in a circular patch resonator, and a characteristic mode analysis is carried out. Then, current distributions are studied for a circular patch with four shorting pins, and the pins are slightly shifted to excite two orthogonal degenerate modes simultaneously for CP wave radiation. Finally, the CP circular patch antenna with four shorting pins and optimal feed position is designed to enhance the antenna gain. The proposed antenna has a compact size with dimensions of 0.49λ 0 × 0.49λ 0 × 0.0147λ 0 at 2.76 GHz. According to this study, we can determine the best place of the pins for obtaining the circular polarization. The return loss and radiation properties are measured and compared with simulation results. The proposed antenna has a 3 dB axial ratio bandwidth of 1.8% (2.73–2.78 GHz). The measured gain is 6.1 dBic at 2.76 GHz. The importance of this study is that we can predict the behavior of the antenna with a different number of shortening pins for defining the resonance frequency and obtaining circular polarization.

Ultrabroadband Circularly Polarized Antenna Array Based on Microstrip to SIW Junction

This communication presents a circularly polarized (CP) antenna array with ultrabroadband characteristics and a high gain for millimeter-wave applications. The CP is achieved by arranging eight linearly polarized (LP) tapered slot antenna elements in a circular arrangement based on sequential rotation (SR) techniques. The hybrid structure takes advantage of microstrip line (MSL) compactness in the feeding network and the capabilities of the substrate integrated waveguide (SIW) in antenna element design. A new T-junction MSL-to-SIW transition with a wide range of coupling ratios is used to serve as a wide power divider in the compact SR-feeding network. A detailed parametric study is carried out to demonstrate the effects of the coupling mechanism between the two transmission lines and to find the optimal configuration for the elements of the proposed antenna array. A tradeoff is made between antenna coupling, phase deviation, and overall size to achieve a compact structure with robust performances. An eight-element antenna array prototype is fabricated through the PCB process with a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$57\times 48\times96$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Measured results show a 3 dB axial ratio bandwidth of about 49% over the entire 22.8–37.7 GHz range and a maximum gain of 18 dBi.

A low-profile broadband circularly polarized metasurface antenna based on characteristic mode analysis

A new broadband circularly polarized (CP) metasurface (MS) antenna based on characteristic mode analysis (CMA) is proposed. The antenna consists of 4×4 truncated Γ-shaped unit cells and is fed by an improved slot coupling structure. The characteristic modes required to achieve CP are analyzed by CMA, and the CP performance is improved by changing the characteristic currents distribution. By introducing a stepped slot structure on the slot floor, the bandwidth of the antenna has been further broadened. By loading the microstrip line to feed the MS, left-handed circular polarization (LHCP) can be realized. In addition, the equivalent circuit method is used to explain how the designed MS antenna achieves CP. The overall size of the designed and fabricated MS antenna is 0.72×0.72×0.08 at 6.2 GHz. The measured −10 dB impedance bandwidth of the antenna is 25.17% (5.21 GHz-6.71 GHz) and the measured 3 dB axial ratio bandwidth is 17.42% (5.87 GHz-6.99 GHz). Moreover, the highest gain in the working frequency band is 7.52 dBic. The proposed CP MS antenna has good application prospects in C-band satellite communications.

A dual‐curl antenna with coplanar feedline for sequential rotation

Using the method of moments, a dual-wire antenna with a single balanced feed is proposed. To enlarge a 3 dB axial ratio bandwidth, non-resonant radiation elements and a coplanar feedline for sequential rotation (SR) are used. It is revealed that the bandwidth reaches 49%, which is 1.7 times as wide as that without SR. Subsequently, the balanced feed is transformed into a quasi-balanced one to consider voltage standing wave ratio (VSWR). It is found that the VSWR remains less than two in the axial ratio bandwidth. Simulated results are verified with experimental ones.

Broadband Circularly Polarized CPW-Fed Monopole Antenna with a Via-Free CRLH-TL Unit Cell

This article presents a broadband circularly polarized composite right/left-hand (CRLH) antenna. A compact microstrip line inductor and an interdigital capacitor are used to form a left-handed parallel inductor and a left-handed series capacitor. The metamaterial parameters of the series inductor and the parallel inductor are optimized. The asymmetric perturbation is introduced to excite the circularly polarized (CP) electromagnetic wave. The influence of interdigital capacitance on the electrical performance of the antenna is analyzed theoretically and experimentally. The value of CL is changed to reduce the electrical size of the antenna, and the resonant frequency of the antenna is reduced accordingly. The physical dimensions of this CPW-Fed monopole antenna are 25 mm ∗ 24 mm ∗ 1 mm. The measured 10 dB wide impedance bandwidth is 79.5%, and the measured 3 dB axial ratio (AR) bandwidth is 56.2%.

A Low-Profile Broadband Metasurface Antenna With Polarization Conversion Based on Characteristic Mode Analysis

In this paper, a low-profile, broadband metasurface antenna for polarization conversion is proposed based on characteristic mode analysis (CMA). A new type of metasurface unit with a partially chamfered symmetrical triangular structure is designed. The inherent physical characteristics of the antenna are analyzed based on CMA, and the expected characteristic modes are selected for excitation at a suitable position. Slot-coupled feeding via microstrip line realizes the performance of wide impedance bandwidth and axial ratio bandwidth (ARBW). The measured -10 dB impedance bandwidth of 36.3% (4.38–6.32 GHz) and the 3 dB ARBW of 20.1% (5.41–6.62 GHz) are achieved. The left-hand circular polarization (LHCP) is realized, and the measured highest gain in the working frequency band is 6.05 dBic. The overall size of the designed and fabricated metasurface antenna is 0.58 λ0 × 0.58 λ0 × 0.07 λ0at 5 GHz. The proposed metasurface antenna can be well used in C-band satellite communications due to its low profile, broadband, and circular polarization.

Compact-Size Ultra-Wideband Circularly Polarized Antenna With Stable Gain and Radiation Pattern

A novel ultra-wideband (UWB) circularly polarized (CP) antenna array with sequential phase feed is proposed in this article. The element implements a multiresonance monopole to achieve UWB CP radiation. To investigate the CP operating mechanism, characteristic mode analysis is used to provide different modes at various frequencies. The simulated characteristic mode analysis results show that this element can realize good CP at three independently adjustable frequencies (2.4, 3.8, and 5.8 GHz). By combining these three frequencies, a UWB CP antenna element is realized from 2.02 to 6.03 GHz for axial ratio (AR) less than 3.0 dB. Because the main radiating region of this element changes at different frequencies, a compact 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 array, whose profile is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.09\lambda $ </tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> is the wavelength in free space at the lowest operating frequency), is designed and optimized to achieve higher realized gain and stable radiation pattern. Subsequently, a prototype of this array is fabricated and measured. Measured results demonstrate an overlapping bandwidth of 120.9% from 1.8 to 7.3 GHz, in terms of the −10 dB reflection coefficient bandwidth and 3 dB AR bandwidth. This array has the advantages of simple structure, compact size, high gain, and stable pattern within the entire operating band.