In this paper, a multi-band AMC-backed antenna system characterized with high gain and low-profile is proposed. It is constructed by placing a quad-band coplanar-waveguide (CPW) antenna over an AMC with four zero-phases in the reflection coefficient. The CPW antenna consists of an ornamental-pillar-shaped patch with the specially designed parasitic elements, and a defected ground structure (DGS), for the application in the frequency bands of 2.45, 3.5, 4.6 and 5.8 GHz. To improve the CPW antenna’s radiation performance, an artificial magnetic conductor (AMC) ground with four zero-phases of the reflection coefficient is designed and employed as the reflector. The AMC unit cell is composed of four metallic nested rings (FMNR), whose innermost ring is connected in series to four lumped capacitors. It is observed that the proposed quad-band AMC ground can not only increase the gains of the multi-band antenna greatly but also combine the two intermediate frequency bands of the antenna into a broadband one. The prototypes of the antenna and the AMC array with $5\times {5}$ unit cells were fabricated and measured. It is found that in comparison to the antenna without AMC, the AMC-backed antenna obtains a gain enhancement by amounts of 4.93, 5.92, 5.54 and 4.95 dB at the frequencies of 2.45, 3.5, 4.6 and 5.8 GHz. The 10-dB impedance bandwidths of the AMC-backed antenna include three bands of 2.13–2.87, 3.22–4.75, and 5.54–5.86 GHz, with the corresponding relative bandwidths of 14.8%, 38.4%, and 5.3%. The proposed antenna can be potentially applied to the applications in WLAN, WiMAX, and 5G mobile communication systems.

/pdf/multi-band-and-high-gain-antenna-using-amc-ground-71u8t949lz.pdf

Multi-Band and High Gain Antenna Using AMC Ground Characterized With Four Zero-Phases of Reflection Coefficient

A high gain and wideband multiple-input multiple-output (MIMO) for 5G new radio (NR) networks is introduced in this paper. The single unit is a monopole antenna with partial ground plane and two small triangles are cut out from the patch to produce the proposed frequency band. The two elements are located orthogonal to each other in order to reduce the mutual coupling without using isolation structure at the desired frequency 28 GHz. An artificial magnetic conductor (AMC) is located underneath the MIMO antenna to improve the gain by about 55% over the entire achieved frequency band (26-31.5 GHz). The Suggested antenna model with the AMC structure is fabricated to verify the simulation results in terms of S-parameters, radiation patterns, gain, and diversity parameters. It is worth noting that the experimental results have the same trend of the simulation ones which makes the suggested AMC-based MIMO antenna applicable for 5G NR networks.

High gain, wideband and low mutual coupling AMC-based millimeter wave MIMO antenna for 5G NR networks

In this work, a compact two-element triple-band multiple-input multiple-output (MIMO) antenna loaded with reflective type metasurface (MS) for enhancing the gain, isolation and impedance bandwidth (IBW) is presented. The two-element radiator antenna consists of a microstrip feed line on the upper side of the substrate and defected ground structure (DGS) on the backside on which multiple slots are etched for obtaining triple-band antenna performance. Due to DGS loading, the entire dimensions of the single radiator antenna are reduced to 22 × 22 × 1.6 mm3 with smaller electrical dimensions of 0.17λ 0 × 0.17λ 0 × 0.012λ 0 at the first resonating frequency. The proposed two-port MIMO antenna with MS operates at 2.36–2.50, 3.43–3.50 and 5.15–5.88 GHz with percentage bandwidths of 5.76, 2.02 and 13.22% for the three operating bands. Due to MS loading, a gain improvement of 5.49, 4.57 and 0.80 dBi is noticed with a maximum gain of 3.98, 5.25 and 2.66 dBi is obtained at the three operating frequencies of 2.46, 3.51 and 5.32 GHz, respectively. The intended antenna is appropriate for working in IEEE 802.11 b/g/n (2.4–2.484 GHz) WLAN, IEEE 802.11 a/h/j (5.15–5.825 GHz) WLAN, and IEEE 802.16e (3.4–3.5 GHz) WiMAX wireless applications.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2020.0350

Bandwidth and gain enhancement of triple-band MIMO antenna incorporating metasurface-based reflector for WLAN/WiMAX applications

A four-port wideband cavity-backed antenna is presented for indoor base stations applications. The antenna is composed of a square open cavity with an X-shaped isolating block and 4 feeding monopoles symmetrically and orthogonally arranged in the aperture of the cavity. A novel methodology based on Characteristic Modes Analysis (CMA) is used for identifying the modes which are contributing to the coupling. As a result of this analysis, an X-shaped isolating block placed at the center of the cavity is proposed for increasing the isolation between ports. A wide-band four-port antenna with unidirectional radiation patterns is obtained with a measured impedance bandwidth ( $\text{S}_{11} dB) ranging from 1.55 to 6 GHz (118%), covering most of the sub-6 GHz 5G bands. The proposed antenna provides four independent radiation patterns, with 16 dB of measured minimum isolation between ports and an efficiency higher than 84%. Multiple-input multiple-output (MIMO) compatibility is confirmed with a $4\times 4$ MIMO simulated system with an envelope correlation coefficient (ECC) $129.5\times 129.5 \times 28.2$ mm3 ( $0.68\lambda \times 0.68\lambda \times 0.15\lambda $ , at a frequency f $=\,\,\text{f}_{min} =1.55$ GHz). Moreover, the antenna has the advantage of avoiding complex feeding structures with baluns or directional couplers.

/pdf/four-port-wide-band-cavity-backed-antenna-with-isolating-x-1dqavb3gg1.pdf

Four-Port Wide-Band Cavity-Backed Antenna With Isolating X-Shaped Block for Sub-6 GHz 5G Indoor Base Stations

This paper presents an active mode subtraction method based on the characteristic mode analysis to estimate the forward directivity based on the difference in modal significance curves. This made the optimization of the antenna gain in the design process to be more efficient. To the best of the authors’ knowledge, such method is innovative and proposed in literature for the first time. This method is derived on the basis that the total radiated field of the antenna, and consequently, the directivity is mainly contributed by the excited dominant modes. To demonstrate its effectiveness, three compact, planar, and wearable antennas with increasing complexity will be designed and optimized using this method. The first is a conventional circular patch antenna operating at 5.3 GHz, whereas the second one is a planar loop antenna operating at 3.08 GHz. The third design is a crown-shaped planar antenna (CPA) with a $3\times3$ artificial magnetic conductor (AMC) plane integrated underneath to reduce potential coupling effects from the body. All three antennas are made fully using textiles with the same thicknesses: felt fabric as its substrate and ShieldIt Super as its conductive textile. For all designs, the use of the proposed method, which is validated using the method of moments, has predicted the maximum direction of radiation and its respective gain at the desired frequencies with good accuracy. Besides that, the design of the AMC plane for the CPA is also optimized using CMA prior to the integration with the antenna and a leather wrist strap. Measurements of the final crown-shaped antenna design indicated a good agreement with simulations, with an operating bandwidth of more than 240 MHz, FBR of 15.73 dB and a directional radiation pattern outward from the body.

/pdf/gain-optimization-of-low-profile-textile-antennas-using-cma-zm2ct2zpq8.pdf

Gain Optimization of Low-Profile Textile Antennas Using CMA and Active Mode Subtraction Method

A low-profile dual-band dual-polarized antenna with an artificial magnetic conductor (AMC) reflector is proposed for 5G communications. The antenna consists of a pair of crossed dual-polarized dual-band bowtie dipoles and a dual-band AMC reflector. By introducing trapezoidal slots and U-shaped slots on the bowtie dipoles, miniaturization and dual-band characteristics are achieved. Moreover, T-shaped feeding structures are utilized to broaden the bandwidth of the bowtie dipoles. By adopting a dual-band AMC reflector instead of a conventional perfect electric conductor (PEC) reflector, the distance between the radiator and the reflector can be reduced from $0.25\lambda _{0}$ to $0.08\lambda _{0}$ (where $\lambda _{0}$ is the free-space wavelength at 3.5 GHz). The radiator can maintain the impedance bandwidth and a high gain can also be achieved, even if it is close to the AMC reflector. A geometrical optics model is used to explain the mechanism of the AMC. The optimal parameters of the AMC depend on the antenna operating frequency and the distance between the radiator and the reflector. Measurements show that the proposed dual-band antenna has an impedance bandwidth of 19.8% (3.14-3.83 GHz) and 13.2% (4.40-5.02 GHz), covering the sub-6 GHz frequency spectra of 5G mobile communications. The peak gain is 7.1 dBi in the lower band and 8.2 dBi in the upper band. Port isolation better than 20 dB is achieved. The proposed antenna can be used alone for 5G indoor base station, or as the element of an array for 5G outdoor base station.

/pdf/a-low-profile-dual-band-dual-polarized-antenna-with-an-amc-sf0zs3fzes.pdf

A Low-Profile Dual-Band Dual-Polarized Antenna With an AMC Reflector for 5G Communications

We report a broadband ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna of compact size mounted on a metallic object in a near field communication (NFC) RFID system. One ...

Compact broadband circularly polarized UHF RFID tag antenna for metallic mounting

A dual-band dual-polarized low-profile antenna loaded with an artificial magnetic conductor (AMC) reflector is proposed for 5G base stations. The proposed antenna consists of a pair of crossed dual-band rectangular dipoles and an AMC reflector, which operates as the perfect magnetic conductor (PMC) in the lower band and the perfect electric conductor (PEC) in the upper band. By using the AMC reflector instead of the conventional PEC reflector, the distance between the dipole radiator and the reflector can be reduced from 0.25λ 0 to 0.14λ 0 (where λ 0 is the free-space wavelength at 3.45 GHz) without performance degradation. Simulated results show that the proposed antenna has an impedance bandwidth of 3.2–3.7 GHz and 4.8–5.0 GHz, covering the sub-6 GHz spectra for 5G mobile communications in China. The simulated antenna peak gains are 8.1 dBi in the lower band and 6.2 dBi in the upper band. The port isolation of the proposed antenna is better than 20 dB within the 5G operating band.

Qingchong Liu

Papers

A Low-Profile Dual-Band Dual-Polarized Antenna With an AMC Reflector for 5G Communications

Compact broadband circularly polarized UHF RFID tag antenna for metallic mounting

A Dual-band Dual-polarized Antenna with AMC Reflector for 5G Base Stations