In this article, a novel slot-array defected ground structure (DGS) for decoupling microstrip antenna array is proposed. The slot-array DGS is etched surrounding each antenna element on the ground plane and parallel to the radiating edges of each antenna element. The decoupling mechanism is elucidated via an equivalent circuit model and the coupled current field analysis, which reveals slot-array DGS has the spatial band-stop characteristic and changes the direction of the partially coupled current, respectively. Both characteristics of the slot-array DGS contribute to mutual coupling reduction. Three practical design examples of applying slot-array DGS to single-linearly polarized (LP), dual-LP, and compact circularly polarized (CP) antenna array are given to illustrate the design process and considerations. The simulated and measured results show that about 50 dB isolation enhancement is obtained by using the slot-array DGS when the edge-to-edge spacing between CP antenna elements is 0.057 wavelength. Additionally, a wheel-shaped absorber based on the electromagnetic loss material is designed and fabricated to reduce the backward radiation caused by slot-array DGS. The absorber has an absorptivity of more than 95% in the frequency range of 1.2–1.35 GHz and suppresses the backward radiation over 12.5 dB in the plane phi = 0° and 16.1 dB in the plane phi = 90° without deteriorating other antenna performances.

A Novel Slot-Array Defected Ground Structure for Decoupling Microstrip Antenna Array

We design and demonstrate a thermally switchable terahertz metamaterial absorber consisting of an array of orthogonal coupled split-ring metal resonators involving a VO2 phase transition. Numerical results indicate that the active metamaterial always absorbs the TE wave in dual-band regardless of insulating and metallic VO2, while the insulator-to-metal phase transition enables a switchable effect between dual-band and broadband absorption of the TM wave with the resonant frequency tunability of 33%. Especially under the metallic VO2 state, the absorption properties are polarization-dependent and exhibit a switching effect between dual-band and broadband absorption with the increase of the polarization angle. The tunable absorption mechanism can be explained by effective impedance theory and electric energy density distributions. The proposed dual-band to broadband metamaterial switching absorber may have broad applications in sensors, imaging and emitters.

Switchable dual-band to broadband terahertz metamaterial absorber incorporating a VO 2 phase transition

In this paper, a graphene-based patch antenna is proposed. The antenna structure is designed so that each of the various antenna sections affected by chemical potential changes can provide a certain radiation behavior for the antenna far-field. The main purpose of the design is to control the polarization of the antenna only by changing its graphene layer Fermi energy level, so that its physical structure remains fixed. In this way, it is possible to achieve a wideband antenna with a favorable matching in the frequency range of 0.82 to 1.07 THz. It is possible to control its polarization in three states: the right- and left-hand circular polarization with an axial ratio less than 3 dB for a frequency range of 0.975 to 1.025 THz, and linear polarization in frequency range of 0.82 to 1.07 THz. The important point is that the physical structure of the antenna by adding circular layered patches at its edges provided us with the possibility of achieving a circular polarization, and with the creation of multi resonance behavior in the input impedance, provided the possibility of increasing bandwidth, significantly.

Polarization Controlling of Multi Resonant Graphene-Based Microstrip Antenna

A 24 GHz Industrial, Scientific, and Medical (ISM)-band Doppler radar antenna with high isolation is proposed for moving target sensing applications. Both transmit (Tx) and receive (Rx) antennas consist of 2 × 2 microstrip patch antenna arrays. High isolation of the proposed antenna is achieved by inserting periodic Jerusalem cross slot array between Tx port and Rx port, and thus the surface wave from Tx port to Rx port is significantly suppressed. The −10 dB reflection coefficient bandwidth of the proposed antenna is 510 MHz, and the isolation between Tx port and Rx port is higher than 36.7 dB over the 24 GHz ISM band. The simulated half-power beamwidths are 58.53° for E -plane and 47.54° for H -plane. Experimental results show that high isolation can lead to improve Doppler radar performance. The proposed antenna can be a good candidate for contact-free monitoring of the heart rate and respiration rate in healthcare applications.

A 24 GHz ISM-Band Doppler Radar Antenna With High Isolation Characteristic for Moving Target Sensing Applications

Multiple-input multiple-output (MIMO) antennas have been a mainstream technology in fifth generation (5G) communications However, strong mutual coupling between both adjacent and nonadjacent elements is inevitable, especially among highly integrated devices In this paper, a slit embedded mushroom electromagnetic bandgap structure (EBG) is primarily proposed to suppress the propagation of surface wave between antenna elements Subsequently, complementary split-ring resonators (CSRRs) are periodically arranged in two sides of the ground to steer the surface wave By effectively utilizing the unusual electromagnetic property of EBG and CSRR to manipulate the propagation of surface wave, the mutual coupling between antenna elements has immensely alleviated Finally, an H-shape defected ground structure (DGS) is introduced to reinforce decoupling effect In order to validate the feasibility of the design principle, a prototype of the proposed antenna has been fabricated and measured Measured results demonstrate that the decoupling concept in this paper is reasonable and approximately 12 dB reduction of mutual coupling is realized

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Enhancing MIMO Antenna Isolation Characteristic by Manipulating the Propagation of Surface Wave

Decoupling of a wideband circularly polarized (CP) conformal array is studied by a single-negative (SNG) metamaterial (MTM) isolator. The conformal array consists of two wideband CP antennas, which are assembled on an arched carrier, and a wideband SNG structure is placed between the antenna elements for coupling reduction. The SNG structure consists of four wheel-shaped units concentrically. The SNG structure is bianisotropic, and its constitutive parameters are tailored to form a wide isolation band. By using the proposed wideband SNG structure, the mutual coupling between the conformal antenna elements is reduced up to 25 dB at 4.5 GHz, and the mutual coupling is improved in the 3.9–5.05 GHz band. In addition, the loading of the SNG structure has little effect on the axial-ratio bandwidth. Besides, the gain and radiation patterns are improved. This research provides some basis in the decoupling of the conformal array.

Coupling Reduction for a Wideband Circularly Polarized Conformal Array Antenna With a Single-Negative Structure

An ultra-broadband terahertz absorber is proposed by a metasurface consisting of coplanar graphene fishnet pattern and gold cross-shaped pattern. The mechanisms of the ultra-broad absorption band of the absorber are that multiple localized surface plasmon resonances are excited in the metasurface and the hybridization of the graphene and gold patterns enhances the field in the metasurface. Besides, the multiple reflections of incidence between the top surface and bottom mirror also enhance the absorbance. The design demonstrates that a band of 90% absorption can be expanded to 8.7 THz with a centric frequency 6.45 THz (134.88%). In addition, the proposed absorber is insensitive to the angle of polarization and it is slightly sensitive to the incident angle. Furthermore, the absorption bandwidth of 85% absorbance can be tuned from 2~8 THz to 2~11 THz via changing the bias voltage. The proposed absorber is interesting for the applications of sensing, detecting, and optoelectronic devices.

An Ultra-Broadband Terahertz Absorber Based on Coplanar Graphene and Gold Hybridized Metasurface

The invention discloses a zeroth-order resonator and a low-profile zeroth-order resonator omnidirectional circularly polarized antenna. The zero-order resonator is composed of a dielectric substrate, a metal patch, a metal floor and a short-circuit pin. The metal patch and the metal floor are respectively adhered on the two relatively parallel surfaces of the dielectric substrate. One end of the short-circuit pin is connected with the metal patch, and the other end is connected with the metal floor. The zeroth-order resonators are arranged at the external side of the radiation type feed network of the antenna in a surrounding way. Phase difference between two polarizations is enabled to be fixed at 90 degrees by the zeroth-order resonators, electric dipoles and magnetic dipoles are constructed by using a mode of circular ring group arrays, and the design of the zeroth-order resonator units and optimization of the circular ring array circularly polarized antenna are separated without considering the phase problem of two mutually perpendicular linear polarization components so that optimization efficiency can be enhanced, system resources can be saved and design efficiency can be enhanced. Besides, the designed omnidirectional circularly polarized antenna has the low-profile characteristic and can be applied to systems with the requirement for the antenna profile.

Zeroth-order resonator and low-profile zeroth-order resonator omnidirectional circularly polarized antenna

Compact spoof surface plasmon polariton leaky-wave antenna with consistent gain

The invention discloses a broadband high-gain circularly polarized antenna, which comprises a first dielectric substrate, a second dielectric substrate and a metal reflector plate, wherein the first dielectric substrate, the second dielectric substrate and the metal reflector plate are parallel to one other and are sequentially superposed at intervals from top to bottom; a metal ground plate coats the upper surface of the second dielectric substrate; an S-shaped coupling gap is formed in the metal ground plate; a strip-shaped microstrip feeder coats the lower surface of the second dielectric substrate; the extension direction of the microstrip feeder is vertical to that of the S-shaped coupling gap; the center region of the S-shaped coupling gap is projected into the microstrip feeder; and a metal radiation patch coats the lower surface, namely one surface toward the second dielectric substrate, of the first dielectric substrate. The broadband high-gain circularly polarized antenna has the characteristics of being small in size, low in construction cost, simple in structure and easy to be integrated with other equipment when broadband high-gain circular polarization of the antenna is achieved.

Liao Xin

Papers

Coupling Reduction for a Wideband Circularly Polarized Conformal Array Antenna With a Single-Negative Structure

An Ultra-Broadband Terahertz Absorber Based on Coplanar Graphene and Gold Hybridized Metasurface

Zeroth-order resonator and low-profile zeroth-order resonator omnidirectional circularly polarized antenna

Compact spoof surface plasmon polariton leaky-wave antenna with consistent gain

Broadband high-gain circularly polarized antenna