Low-profile, Broadband, and High-gain Circularly Polarized Metasurface Antenna using 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 λ 0 ×0.72 λ 0 ×0.08 λ 0 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.

This study presents a circularly-polarized (CP) planar monopole antenna designed for ultra-wideband (UWB) applications using characteristic mode analysis (CMA). Initially, a planar monopole antenna with a crescent moon-shaped radiator and a circular open-loop on an FR-4 substrate was designed to achieve wideband characteristics, however, this antenna only satisfied a 3 dB axial ratio (AR) bandwidth within the 8.78–9.4 GHz range. To enhance the AR bandwidth, a triangular slit, a shark fin-shaped stub, and an L-shaped strip were added to the ground plane, generating orthogonal modes in the desired frequency band using CMA. The overall dimensions of the proposed antenna are 30 × 24 × 1.6 mm2 (0.58 × 0.46 × 0.031 λ₀2). The − 10 dB S11 bandwidth is 5.73–10.78 GHz (61.21%) and the 3 dB AR bandwidth is 6–11.12 GHz (59.81%), achieving overlapped bandwidth from 6 to 10.78 GHz (56.9%). The proposed antenna has a realized gain 2.4–5.4 dBi and an average efficiency of 80% within the target frequency. A time-domain analysis, including group delay and system fidelity factor, is conducted to evaluate performance. The fabricated antenna demonstrates omnidirectional radiation patterns at various frequencies and performs well in both the time and frequency domains.

This article presents a miniaturized reconfigurable tri-polarization metantenna with compact size of 0.58 λ 0 × 0.58 λ 0 × 0.04 λ 0 ( λ 0 is the free space wavelength referring to the antenna center frequency). Metantenna means the metasurface is directly used as the antenna radiator aperture instead of an accessory. The metantenna is formed by miniaturized windmill like units, which is evolved from square patch units based on characteristic mode analysis, and 46% size reduction is achieved. Two PIN diodes are introduced into the feeding microstrip for switching among tri-polarization. The measured −10 dB impedance bandwidths are 24.6% (3.24–4.15 GHz) and 24.1% (3.26–4.05 GHz) for circular polarization (CP) and linear polarization (LP), respectively. The measured overlapped 3 dB axial ratio (AR) bandwidth is 15% (3.4–3.95 GHz). The measured peak gains are 5.15 dBi, 5.21 dBic, and 5.25 dBic for LP, left hand (LH) CP and right hand (RH) CP, respectively. The aperture efficiency is 77.3%, 78.5%, and 79.1% for LP, LHCP, and RHCP, respectively. The measured AR beamwidth (BW) of LHCP in XZ-plane and YZ-plane is 192° and 174°, respectively, the measured ARBW of RHCP in XZ-plane and YZ-plane is 201° and 166°, respectively. The developed metantenna has the following advantages: broadband 3 dB AR bandwidth, wide ARBW > 166°, least PIN number (tri-polarization with 2 PIN), and high-aperture efficiency.

The circularly polarized (CP) antennas with high gains have gained growing interest due to their significant advantages, but the existing works usually suffer from narrow bandwidths. In this work, a novel circularly polarized folded transmitarray antenna (CPFTA) inspired by the characteristic mode analysis (CMA) method is proposed to achieve a broadband and high-gain CP radiation. The proposed CPFTA consists of a top-layer multifunctional metasurface (MTS), a bottom-layer polarization conversion metasurface (PCM) integrated with a linearly polarized (LP) microstrip feed source. Enabled by the CMA, the unit cell etched with an asymmetric U-slot of the MTS is optimized to generate two pairs of CP modes to broaden the bandwidth of the CPFTA. Moreover, a modified broadband E-shaped LP microstrip antenna is integrated with the PCM, resulting in a compact profile. A CPFTA prototype is fabricated and characterized to verify the effectiveness of the design. The measured results show that the fabricated antenna could obtain an impedance bandwidth of 31.7%, a 3 dB axial ratio (AR) bandwidth of 36.5%, and a 3 dB gain bandwidth of 30.1% with a peak gain of 22.35 dBic at 9.55 GHz.

A broadband circularly polarized (CP) metasurface antenna based on characteristic mode analysis (CMA) is proposed. The antenna consists of a truncated corner square driver patch loaded with L-shaped branches, sandwiched between a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4\times 4$</tex> metasurface and a ground plane. The CP wave is generated by exciting the driving patch, and the CP wave excites the surface wave propagating on the metasurface, resulting in a wide impedance bandwidth and Axial ratio (AR) bandwidth. The overall size of the antenna is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$36\text{mm}\times 36\text{mm}\times 4.5\text{mm}\ (0.72\ \lambda_{0}\times 0.72 \lambda_{0}\times 0.09\ \lambda_{0})$</tex> . The simulation results show that the bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\vert \mathrm{S}_{11}\vert &lt; -10\ \text{dB}$</tex> is 4.04-8.83 GHz (74.44%), the 3dB AR bandwidth is 4.65-6.92 GHz (39.24%), and the peak gain is 6.83 dBic. In addition, the antenna has good left-handed CP radiation performance within the operating bandwidth, which is suitable for C-band satellite communication applications.

A broadband metasurface antenna is proposed based on characteristic mode analysis. By using a microstrip coupling slot as feed source, and a 90° phase difference is generated between the two modes, thus generating circularly polarized radiation. The antenna is composed of a metasurface, an air layer, and a feeder layer, and the metasurface structure is circularly polarized by slit and Angle cutting. The simulation results show that the antenna can achieve -10 dB bandwidth at 5.59-10.02 GHz, with the relative bandwidth of 56.8%, 3dB Axial Ratio (AR) bandwidth of 7.66-10.21 GHz, with the relative bandwidth of 28.5%.

A low-profile wideband circularly polarized (CP) metasurface antenna is demonstrated for C-band applications. The metasurface consists of 4 × 4 square patches with Z-shaped slots. Characteristic mode analysis is used to investigate the modal behavior of the metasurface, and a pair of degenerate modes is chosen as the operating modes. The CP radiation is realized by exciting a pair of degenerate modes of the metasurface through a slot antenna, which is used as a feed structure with a 90° phase difference. The CP bandwidth is further widened by combining the resonance modes of the metasurface and slot antenna. The measured results show that the −10 dB impedance bandwidth of the antenna is 3.47–4.76 GHz, and the 3 dB axial ratio bandwidth is 3.5–4.9 GHz with a peak gain of 6.9 dBic. Moreover, the antenna exhibits well left-hand CP radiation performances with a low profile of 0.046λ0.

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.

This paper presents a single-fed triple-mode excited low-profile broadband circularly polarized (CP) metasurface (MTS) antenna. It uses a slot-coupled circular patch antenna (CPA) to generate a narrow band of CP radiation and an MTS to broaden it. This work emphasizes a characteristic mode analysis (CMA) based systematic design approach to realize broadband CP. The CMA of a circular patch reveals the existence of orthogonal degenerated modes. A capacitive loading method separates these modes, creating a 90°phase difference for circular polarization; hence, CPA acts as a narrow-band CP radiator. For further CP bandwidth enhancement, an MTS layer is used to produce the required orthogonal modes next to the modes of CPA. The MTS is a 6×6 array of slotted circular MTS elements, which provides only the desired polarized modes (here, horizontal mode) to cascade with the CPA modes. Consequently, the cascaded modes of CPA and MTS remain mutually orthogonal with proper phases, and the excitation of these modes exhibits a wider axial ratio bandwidth (ARBW). The overall dimension of the fabricated antenna is 0.8[Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] (where [Formula: see text] is the free space wavelength at 6.2 GHz). The antenna exhibits an impedance bandwidth of 36.6% (5.18-7.4 GHz) and an ARBW of 26.16% (5.48-7.05 GHz). The design is fabricated using an FR-4 substrate and measured for validation. Being a low-cost design with a broad ARBW, it becomes promising for various sub-6 GHz wireless applications.

This paper proposes a novel high-gain, wideband, circularly polarized (CP) metasurface (MTS) antenna. The antenna is composed of a centrally symmetric MTS and a slot-coupled feeding network. Through characteristic mode analysis (CMA), parasitic patches and mode-suppressing patches are added around the MTS to enhance the desired modes and suppress the unwanted modes. Subsequently, a feeding network that merges a ring slot with an L-shaped microstrip line is utilized to excite two orthogonal modes with a 90° phase difference, thereby achieving CP and high-gain radiation. Finally, a prototype with dimensions of 0.9λ0 × 0.9λ0 × 0.05λ0 is fabricated and tested. The measured results demonstrate an impedance bandwidth (IBW) of 39.5% (4.92–7.37 GHz), a 3 dB axial ratio bandwidth (ARBW) of 33.1% (5.25–7.33 GHz), and a peak gain of 9.4 dBic at 6.9 GHz.

A novel design of a multiband monopole mobile phone antenna with circular polarization for GNSS application is presented. The proposed antenna generates four resonant frequencies with branch lines and a shorted parasitic strip to obtain a wide operating band. With the definition of 2.5:1 VSWR, the bandwidth covers several wireless communication systems, including GSM (880 ~ 960 MHz), DCS (1710 ~ 1880 MHz), PCS (1850 ~ 1990 MHz), UMTS (1920 ~ 2170 MHz), WiBro (2300 ~ 2390 MHz) and ISM (2400 ~ 2483 MHz), and also covers GNSS, including COMPASS (1559.052 ~ 1591.788 MHz), GPS (1575.42 ± 5 MHz), GLONASS (1602 ~ 1615.5 MHz). A tuning stub is added to the ground plane and the feeding strip is mounted 45 ° at the corner to achieve circular polarization for GNSS application. The 3 dB axial ratio (AR) bandwidth (AR-BW) is obtained from 1540 to 1630 MHz, covering the L1 band of GNSS, including COMPASS, GPS and GLONASS. In the 3 dB axial ratio bandwidth, right hand and left hand circularly polarizations are obtained in different broadside directions, with the peak circularly polarized gain of more than 2.7 dBic. An equivalent circuit network is used to analyze the mechanism of circular polarization. Details of the proposed antenna parameters, including return loss, radiation characteristics, and AR spectrum are presented and discussed.

A high-gain rectangular waveguide-fed aperture antenna that uses a Spidron fractal structure to produce circular polarization is proposed. The antenna consists of a Spidron fractal aperture etched onto the ground plane of a dielectric substrate that is directly excited by a WR (Waveguide Rectangular)-90 waveguide-to-coax adapter. A superstrate was implemented at an appropriate distance above the antenna to enhance the broadside gain significantly. An antenna prototype was fabricated and tested to validate the design. The measured impedance bandwidth for | S 11 | ≤ −10 dB is 9.89–11.58 GHz (15.74%). The corresponding measured 3 dB axial ratio (AR) bandwidth is 10.68–11.00 GHz (2.95%), and within the measured 3 dB AR bandwidth, a maximum realized gain of 9.59 dBic is achieved. The radiation patterns of the proposed antenna are presented and discussed.

This work presents a novel design of a low-profile broadband circularly polarized (CP) metasurface (MS) antenna based on characteristic mode analysis (CMA) technique for potential use in C-band satellite communications. The proposed antenna is composed of a 4 × 4 array of truncated patch unit cells and incorporates an enhanced slot coupling feeding structure. CMA technique is employed to analyse and modify to improved CP performance. The proposed design exhibits good radiation characteristics including measured − 10 dB impedance bandwidth of 22.72% (4.8–6.05 GHz), a 3 dB axial ratio bandwidth (ARBW) of 16.3% (5.1–5.95 GHz), and a peak gain of 8 dBi within its operational frequency range. Furthermore, the antenna's metasurface design contributes to scattering suppression over a wide frequency span (4–18 GHz), with a notable peak reduction of 9.1 dB at 8 GHz. This characteristic holds potential significance for radar cross-section (RCS) reduction.

In this paper, a microstrip-fed broadband circularly polarized (CP) slot antenna is presented. CP operation can be attained simply by embedding an S-shaped strip. By loading with a multiple-circular-sector patch, which consists of 12 circular-sector patches with identical central angles of 30° and different radii, the 3 dB axial ratio (AR) bandwidth is significantly broadened. To validate the performance of the proposed antenna, an antenna prototype is fabricated and tested. The fabricated antenna is 54 mm × 54 mm × 0.8 mm in size. The measured −10 dB reflection and 3 dB AR bandwidths are 81.06% (1.68–3.97 GHz) and 70.55% (1.89–3.95 GHz), respectively. Within the 3 dB AR bandwidth, the measured peak gain is 3.81 dBic. Reasonable agreement is also obtained between the measured and simulated results.

In this paper, a broadband left-handed circularly polarized (LHCP) corrugated horn antenna using a dielectric circular polarizer is proposed. Circularly polarized (CP) waves are generated by inserting an improved dovetail-shaped dielectric plate into the circular waveguide. Compared with the traditional dovetail-shaped circular polarizer, the proposed improved dovetail-shaped circular polarizer has a wider impedance bandwidth and 3 dB axial ratio bandwidth. A substrate-integrated waveguide (SIW) structure is designed as a wall to eliminate the influence of fixed grooves on the circular polarizer. The simulated reflection coefficient of the dielectric plate circular polarizer is less than −20 dB in the frequency band from 17.57 to 33.25 GHz. Then, a conical corrugated horn antenna with five corrugations and a four-level metal stepped rectangular-circular waveguide converter are designed and optimized. The simulated −10 dB impedance and 3 dB axial ratio (AR) bandwidths of the circularly polarized horn antenna integrated with the polarizer are 61% (17.1–32.8 GHz) and 60.9% (17.76–33.32 GHz), respectively. The simulated peak gain is 17.34 dBic. The measured −10 dB impedance is 52.7% (17.2–27.5 GHz).