U-shaped Feed Research Articles

Compact Broadband Linearly Polarized Quincunx Metasurface Antennas Using Embedded Fractal Design

A quincunx metasurface (MTS) structure is presented and exploited to design compact broadband metasurface antennas (MTAs). The MTS patch unit is constructed by connecting five same-size quincunx-arrangement squares with strip lines. Since it is a fractal structure and structurally embedded with other units, the gap between adjacent units is prolonged, increasing the edge capacitance. Meanwhile, the surface current is adjusted to flow along the diagonal of quincunx patches, producing a large strip inductance. Hence, the resonance responding to the MTS radiator can be shifted to the low frequencies, while a compact radiating aperture can be obtained accordingly. With the help of characteristic mode analysis (CMA), the quincunx MTS array is modified for further miniaturization. Jerusalem cross aperture and four rectangle apertures are etched on the ground plane, generating aperture modes. Subsequently, the modified quincunx MTS is coupled to a U-shaped feeding network through apertures, forming a horizontally polarized MTA and realizing an operating bandwidth of 37.92% and a peak gain of 7.36 dBi with a compact radiating aperture of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.34\lambda _{0} \times 0.34\lambda _{0}$ </tex-math></inline-formula> . Ultimately, a 45° linearly polarized quincunx MTA using a double U-shaped feeding network is also proposed, obtaining a broader operating bandwidth of 44.60% and 6.43 dBi peak gain with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.34\lambda _{0} \times 0.34\lambda _{0}$ </tex-math></inline-formula> radiating aperture.

Gradient Relative Permittivity Superstrate for Decoupling of Two Closely Located Dual-Polarized Slot Antennas

A simple decoupling method between two closely located dual-polarized slot antennas is proposed in this communication. Based on substrate integrated waveguide (SIW), the dual-polarized antenna is realized using cross-shaped slot and U-shaped feed line, and two identical elements are closely located in edge-to-edge space of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.031\lambda _{0}$ </tex-math></inline-formula> to form the multiple-input–multiple-output (MIMO) array, 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 center operating frequency. Wideband characteristics, high dual-polarized isolation, and low envelope correlation coefficient (ECC) are realized by introducing a superstrate with gradient relative permittivity (GRP) above the array. The GRP is obtained using drilling hole arrays on low-cost FR-4 materials. To validate the proposed design, the antenna array is fabricated and measured. The measured result shows that 13 and 16 dB isolation enhancements are provided for two orthogonally polarized fields, simultaneously. Moreover, the measured operating bandwidth is from 8 to 10.35 GHz (about 25.6%, the isolation is more than 20 dB), and the ECC between two antennas is less than −52 dB for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{1}$ </tex-math></inline-formula> -pol and −62.4 dB for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{2}$ </tex-math></inline-formula> -pol over entire operating band. The proposed method has the potential to be used in MIMO wireless systems.

Frequency-Reconfigurable Liquid Metal Magnetoelectric Dipole Antenna

We propose a frequency-reconfigurable liquid metal magnetoelectric dipole antenna. Two radiation arms composed of liquid metal are attached to the edge of the dipole of a dual polarized magnetoelectric dipole antenna, liquid metal is wrapped in the channel made of a polymethyl methacrylate, a total of eight radiating arms constitute a symmetrical structure, and a pair of U-shaped feeding bars is placed in the middle of the magnetoelectric dipole for coupling feeding, The ground plane and the surrounding reflecting plates form a reflecting cavity structure. The frequency reconfiguration of 1.79–3.85 GHz is realized by adjusting the length of the liquid metal radiation arm. The antenna has a compact structure, with a height of only 0.1 λ in the lowest frequency band, which realizes miniaturization and covers a part of the communication frequency band and can be used for a future 6G communication base station.

A new square-slot circularly polarized antenna array with broadband characteristic

ABSTRACT In this article, we propose a wide square-slot CPA loaded with a semi ellipse patch. The proposed antenna consists of a sequential rotation feeding structure, a square-slot ground-plane with corner cuts, and an asymmetric U-shaped feeding strip. In contrast to the traditional strips and slots etched into the square-slot ground-plane, semi ellipse patch is first inserted into the ground-plane to increase the antenna bandwidth. In addition, four rectangular slots are used to adjust the impedance matching. The slot CPAA could excite multipole CP resonant modes using these slots and patches, which result in the wideband radiation. The proposed slot CPAA has outstanding characteristics of 85.7% (2.0–5.0 GHz) −10-dB IBW and 68.3% (2.20–4.48 GHz) 3-dB ARBW, which would be a potential candidate in the wideband communication.

Novel 2 × 2 square slot circularly polarized antenna array with wideband characteristics

In this paper, a novel 2 × 2 square slot wideband circularly polarized antenna array (CPAA) is proposed. The antenna consists of a sequential rotation feeding structure, four asymmetric U-shaped feeding strips and a slotted ground plane formed by four square slots with cut corners, four rectangular slots, and four L-shaped strips. In contrast to the traditional L-shaped feeding strips used in CPAAs, an asymmetric U-shaped feeding strip is, for the first time, presented to improve the antenna performance. By using these strips and slots as perturbation elements, the slotted CPAA is able to stimulate multiple circular polarized (CP) radiation modes, resulting in wideband CP radiation. The measured results revealed that the 3-dB axial-ratio (AR) bandwidth for AR < 3 reached 81.3% (1.75–4.15 GHz), whereas the −10-dB impedance bandwidth (|S11| < −10 dB) reached 88.6% (1.96–5.08 GHz).

A Wideband Dual-Polarized Aperture-Coupled Antenna Embedded in a Small Metal Cavity

A compact wideband dual-polarized slot-coupled stacked patch antenna is presented in this communication. Two orthogonal U-shaped feed lines are used to excite a cross-slot to obtain dual-polarization. The cross-slot consists of two orthogonal slots whose long sides vary as exponential curves. The impedance bandwidth is increased effectively by using the two orthogonal slots with gradually changing width and stacked patches. The radiation layers and feeding layers of the antenna are embedded in a small cylindrical metal cavity. By using the metal cavity as the reflector, the transverse dimension of the antenna is effectively reduced. The measured results demonstrate that the impedance bandwidth of the antenna is 94% (2.47–6.85 GHz) for $\vert \text{S}_{11}\vert dB with a transmission coefficient of less than −21.2 dB between two input ports. A stable radiation pattern is obtained in the range of 2.5–6.5 GHz. The proposed dual-polarized antenna can be applied to wideband wireless communication systems with compact platforms.

Dual-band slot microstrip patch antennas with dual-radiation modes for wireless communication

AbstractIn this paper, a novel compact dual-band microstrip patch antenna with dual-radiation modes is investigated. The proposed antenna consists of a rectangular ground plane, a U-shaped feed probe, and an H-shaped slot radiating patch. By adjusting the size of these structures, a dual-band antenna can be obtained. In the low-frequency band, the antenna can radiate one radiation beam with high gain. In the high-frequency band, the antenna can achieve monopole-like radiation pattern. Therefore, an antenna prototype is fabricated and measured for validation. Good agreement between the simulated and measured results is observed in this paper. The antenna's operating frequency ranges are 3.6–3.85 GHz in the low-frequency band and 5.1–6.1 GHz in the high-frequency band with the reflection coefficient less than −10 dB. At 3.7 GHz, the antenna radiate one beam with 8.8 dBi realized gain. At 5.5 GHz, it exhibits dual-radiation beams directed to −48 and 48° with 5.6 and 5.5 dBi realized gain in the xoz-plane and −48 and 48° with 2.9 and 3.0 dBi realized gain in the yoz-plane. Therefore, the proposed antenna is a good candidate for wireless communication systems.

CRLH-based compact wideband antenna for mobile applications using U-shaped feed

ABSTRACTIn this article, a compact composite right/left-handed wideband antenna has been proposed and analysed using finite-difference time-domain for cellular applications. The proposed antenna operates at different wireless standards such as GSM1800, WCDMA, WiMAX, Bluetooth and Wi-Fi. It exhibits wideband behaviour with a bandwidth of 55% (at 2.46 GHz). The proposed antenna is compact and has a radiating element size of 0.14 λo × 0.22 λo × 0.01 λo. In addition, commercial Ansys HFSS software has been used to verify the results and a prototype has also been fabricated to test the antenna experimentally. The proposed metamaterial antenna offers good radiation characteristics and is omni-directional in xz-plane with an average gain of 1.3 dBi in the operating bandwidth.

Reconfigurable MIMO Antenna for Integrated-Metal-Rimmed Smartphone Applications

A reconfigurable full-metal-rimmed MIMO antenna is designed and proposed for WWAN/LTE smartphones. This antenna consists of two centro-symmetrically distributed antenna elements and radiation structures using the unbroken metal rim in plastic casing. It can achieve a good isolation of more than 17dB over the entire operation bands. Each antenna element occupies a small ground area of 30 × 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The U-shaped feeding line provides a coupled feed and the antenna element generates four typical loop resonant modes. Using reconfigurable technique to combine these four resonant modes, this hepta-band MIMO antenna can satisfactory cover lower bands of GSM850/900 and higher bands of GSM1800/1900/ UMTS/LTE2300/2500. A prototype MIMO antenna was fabricated and the measured results of S-parameters, antenna efficiency and gain, envelope correlation coefficient, mean effective gain, and channel capacity are reported.

Broadband Dual-Polarized Dipole Antenna with Metallic Cylinder for Base Station

ABSTRACTIn this article, a broadband dual-polarized dipole antenna for mobile communication systems is proposed. The design is based on improvements to conventional bowtie dipole antennas, thereby simultaneously achieving wider bandwidth and a more compact size. The antenna consists of a metallic plate reflector and a pair of orthogonal planar dipoles with U-shaped slots, which are separately excited by T-shaped feeding lines. The application of U-shaped slots and T-shaped feeding lines effectively extends the impedance bandwidth. Additionally, using a new approach of adding metallic cylinders to each dipole improved impedance matching. Experimental results indicated that the designed dual-polarized antenna achieved a notably wide bandwidth (1.58–2.82 GHz). Further, the measured isolation between the two ports was better than 30 dB and cross-polarization level was less than –25 dB on the axis. Moreover, the antenna had stable radiation patterns with half-power beam width of 65° ± 5° on the horizontal plane and an average gain of 8.2 dBi over the operating band. Importantly, these parameters collectively meet current telecommunications industry standards.

Design of U-shaped feed structured antenna for ultrawideband application

In this paper, a new compact suspended antenna is presented for ultrawideband (UWB) application. In the proposed design, a new unequal arm U-shaped feeding patch is suspended below an H-shaped radiating patch to produce wide bandwidth through the electromagnetical coupling technique. This new U-shaped feeding patch is connected to a probe to compensate for probe inductance. Two shorting strips are introduced to hold the radiating patch above the ground plane, as well as reduce the antenna's size. These strips improve the bandwidth at the lower operating band. The proposed antenna has a compact dimension of $$0.129\lambda \times 0.186 \lambda \times 0.096 \lambda $$0.129?×0.186?×0.096?, where $$\lambda $$? is the wavelength of the lowest operating frequency. The proposed antenna has been optimized and its parametric study is performed using an electromagnetic field simulator, based on the finite element method. The proposed antenna is prototyped and measured. Measured results indicated that the proposed antenna structure has achieved an impedance bandwidth of 103.86 %, ranging from 4.3 to 13.59 GHz at $$\hbox {VSWR}\le 2$$VSWR≤2. The measured results of the wideband and stable radiation patterns with acceptable gain signify the effectiveness of the proposed antenna configuration in the context of UWB application.

Dual-Wideband Complementary Antenna With a Dual-Layer Cross-ME-Dipole Structure for 2G/3G/LTE/WLAN Applications

A novel dual-wideband complementary patch antenna with a dual-layer cross-magneto-electric (ME)-dipole structure is proposed for 2G/3G/LTE/WLAN applications. In order to provide dual-wideband and complementary characteristics, an inverted U-shaped feeding structure is introduced to feed dual-layer cross-ME-dipole patches. The upper-layer cross-ME-dipole patches mainly serve the upper frequency band, while the lower-layer ones chiefly work for the lower frequency band. In addition, hook-shaped patches are placed on the corner of upper-layer electric dipoles to broaden the impedance bandwidth of the upper frequency band. Moreover, a box-shaped reflector is employed to attain high and stable gain. The prototype antenna can offer an impedance bandwidth of 51.3% (1.68–2.84 GHz) with a stable gain of $ 8.7\pm 1.5~\hbox{dBi}$ , and an impedance bandwidth of 11.4% (5.31–5.95 GHz) with a gain of $8.2 \pm 1.1~\hbox{dBi}$ for the lower and upper bands, respectively. Hence, it can be suitable for 2G/3G/LTE/WLAN base-station communications.

A Novel Compact 2.4/5.2 GHz Dual Wideband Bandpass Filter with Deep Transmission Zero

In this study, a novel compact 2.4/5.2 GHz dual wideband bandpass filter was designed and fabricated on an Al2O3 ceramic substrate. First, a dual-band filter was designed based on two open-loop rectangular ring (OLRR) resonators, which were cascaded using a coupling connection in order to increase the bandwidths of the dual passbands. Diverging U-shaped dual feed input/output transmission lines were used for strong coupling. A shunt quarterwavelength open stub eliminated unwanted harmonic frequencies and transmitted the desired passbands. To achieve this, four open stubs were directly added onto the two OLRR resonators as bandstop resonators to reject undesired frequencies and improve the out-of-band rejection between the two resonant frequencies. The coupling sections between the two resonators were modified using a groove structure to regulate the coupling of the two modes and eliminate the ripple at the designed 5.2 GHz band. According to simulated and measured results, the proposed filter with optimized parameters exhibited dualwide passbands with bandwidths of 530 MHz (22.84%) and 650 MHz (12.29%) at 2.32 GHz and 5.29 GHz, respectively.

Wideband single-fed proximity coupled circularly polarised annular slot antenna

A wide impedance and axial ratio bandwidths single-fed method for circularly polarised (CP) annular slot antenna is proposed. Impedance and axial ratio bandwidths of approximately 18% have been achieved. The annular slot radiator operating at its fundamental TM11 mode is fed by a simple U-shaped microstrip line structure through proximity coupling at the annular section in the middle of the line. A pair of 100-Ω impedance transformers is connected to transform and align the impedance bandwidth with the axial ratio bandwidth. Simulations show that the source current, which flows in the annular section of the U-shaped feed line, induces a circulating current in the annular slot radiator which contributes the CP radiation. Both currents on the U-shaped feed line and the annular slot radiator flow in the same direction. The antenna radiates at both broadside and backside directions of opposite type of circular polarisation. The type of circular polarisation can be selected by feeding signal into the appropriate input terminal. Moreover, this article has further demonstrated that the bandwidths of the antenna are mainly limited by the radiating elements, not the proposed U-shaped feed line proximity coupled method. A parametric study of the antenna has also been reported. Experimental and simulated results of the antennas are presented and discussed.

A Novel High-Gain Dual-Band Antenna for RFID Reader Applications

A novel high-gain dual-band antenna for radio frequency identification (RFID) reader applications covering free ISM bands of 2.45 and 5.8 GHz is presented in this letter. The antenna is composed of a U-shaped copper strip with unequal arm, a printed rectangular ring, and the ground plane. A good impedance bandwidth of 120 MHz has been achieved from 2.37 to 2.49 GHz for the lower band, while the upper band covers 420 MHz (from 5.55 to 5.97 GHz). The U-shaped feeding strip excites the rectangular ring effectively by providing a good impedance matching with over 85% of total antenna efficiency in both the frequency bands and also 9.56 and 10.17 dBi gain in the lower and higher frequency band, respectively.

Design of microstrip patch antenna using novel U-shaped feeding strip with unequal arm

A novel feeding technique is developed for the microstrip patch antenna. The U-shaped feeding strip with an unequal arm is proposed to feed a printed rectangular ring patch antenna to achieve high gain. Measured results of the prototype antenna agree very well with simulated results. According to the measured results, the antenna shows good impedance bandwidths satisfying ISM 2.45/5.8 GHz with good impedance matching. Stable radiation patterns are achieved with maximum gains of 9.56 and 10.17 dBi for both bands.

Reconfigurable Parts Feeding System Using Array of Vibrators

We propose a reconfigurable parts feeding system (RPFS) consisting of a large number of vibrators, each consisting of a vertical exciter having a piezoelectric element used as a drive source and a plate installed on the vertical exciter. The plate freely chooses a specific feed direction (forward and turn) by adjusting the thickness of the plate and the position of an elastic hinge. The RPSF features: (1) a variety of feed paths freely formed by adjusting plates on vertical exciters, and (2) positional adjustment for plates on vertical exciters automated using a robot to reduce time and cost. We analyzed the vibration of plates based on vibration modes of plates based on FEM analysis. Basic RPFS performance was evaluated in 3 feeding experiments, i.e., along an I-shaped feed path, along a U-shaped feed path, and with a feeding object larger than each plate, using an experimental RPFS.