Radiation Strip Research Articles

An ultra‐wideband MIMO system with multi‐loop mode for full‐screen smartphone applications

AbstractIn this letter, an ultra‐wideband (UWB) eight‐element multiple‐input multiple‐output (MIMO) antenna system with multi‐loop modes for fifth‐generation (5G) smartphones is presented. The antenna unit has a simple structure and is composed of an inverted U‐shaped feeding strip and an L‐shaped grounding radiation strip with a hollow out in the middle. Owing to the generation of two coupling loop modes, the working bandwidth of the proposed antenna unit covers 3.2−6.4 GHz. Besides, the simulated and measured results show that the isolation between any two antennas is better than 12.0 dB, and the total efficiency of each element is higher than 50%. Meanwhile, the measured radiation pattern, envelope correlation coefficients, channel capacity loss, mean effective gain, and diversity gain are also given in this letter. The above results demonstrate that the MIMO system has the advantages of simple structure, convenient manufacture, and superior performance.

A Compact Dual-Band MIMO Antenna for Sub-6 GHz 5G Terminals

In this paper, a dual-band multiple-input-multiple-output (MIMO) antenna is proposed for fifth-generation (5G) wireless communication terminals. The measured -10 dB impedance bandwidths of 380 MHz (3.34–3.72 GHz) and 560 MHz (4.57–5.13 GHz) can cover the 3.4–3.6 GHz and 4.8–5 GHz 5G bands. The single antenna element of this proposed MIMO is composed of an F-shaped feed strip and an inverted L-shaped radiation strip. A defected ground structure is employed to obtain a good isolation performance, whereby the measured isolation between the antenna elements is observed to be larger than 23 dB. The measured total radiation efficiencies at 3.5 GHz and 4.9 GHz are 76.65% and 71.93%, respectively. Besides, the calculated envelope correlation coefficients (ECC) are less than 0.00125 and 0.01164 at the low-frequency and high-frequency bands, respectively. Furthermore, the specific absorption ratio (SAR) analysis of the antenna verifies that it qualifies for 5G terminals.

Minimized Triple-Band Eight-Element Antenna Array for 5G Metal-frame Smartphone Applications.

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only 6.5 mm × 7 mm (0.076 λ0 × 0.082 λ0, λ0 is the free-space wavelength at the frequency of 3.5 GHz). The −6 dB impedance bandwidth of the proposed eight-antenna array can cover 3.3–3.8 GHz, 4.8–5 GHz, and 5.15–5.925 GHz. The evolution design and the analysis of the optimal parameters for a single antenna element are derived to investigate the principle of the antenna. The measured total efficiency is larger than 70%. The measured isolation is better than 13 dB. The measurements of the prototype agree well with the simulation results.

S‐shaped planar antenna with 45° tilted bidirectional radiation pattern for motorcycle helmets

An S-shaped planar antenna (SPA) with a bidirectional radiation pattern and beam tilt characteristic is proposed to achieve maximum communication distance for helmet applications. The proposed SPA is comprised of an S-shaped radiation strip (consisting of a microstrip meander line and two main arms with two inverted L-shaped parasitic elements) and a rectangular ground plane, where a simplified microstrip power divider is introduced by modifying the feed structure in the center of the SPA, such that the S-shaped radiation strip works in the second resonant mode. The proposed SPA generates a tilted beam in the E-plane with an angle of 45°, which is attributed to the obliquely staggered arms of the antenna at a distance. By introducing inverted L-shaped parasitic elements at the end of the two arms, the directivity of the bidirectional radiation pattern can be further improved, thereby increasing the antenna gain. The working principle is analyzed theoretically, and the effects of the antenna structural parameters on the radiation pattern are also analyzed. The experimental results indicate that the 3:1 VSWR impedance bandwidth is 120 MHz, with a realized peak gain of 1.5 dBi at 2.45 GHz. The proposed antenna is designed for real-world applications, allowing the antenna to be obliquely installed while keeping the peak gain direction horizontal for maximum communication distance.

The low-frequency improvement with loading soft magnetic ferrite films for multiband antenna applications

This work presents an easy way to improve the low-frequency properties in a small-size LTE/WWAN smartphone antenna by just loading a soft magnetic ferrite film on the strong radiation area. The base non-magnetic antenna, which only takes up an 11 mm × 30 mm no-ground space, can achieve hexa-band operation covering 822–914/1710–3244 MHz bands by co-designing a meandering strip and a T-shaped feeding strip. With loading a small-size ferrite film (2 mm × 15 mm) at the strong radiation strip, the frequencies can be shifted to cover the range of 692–1191/1698–3020 MHz, which shows a fully covering of octa-band operation, especially including the best long-term-evolution band, LTE700, without enlarging the size of base antenna. In addition, the radiation characteristics of the magnetic antenna with ferrite film loading show a limited change at upper bands (1710–2690 MHz) but an acceptable level at lower bands (698–960 MHz). Both experimental and simulated results have been taken out and shown the consistent tendency. This optimization method of low-frequency properties by introducing a commercial ferrite film on the antenna has provided a simple and convenient way to solve the frequency deviation in the practical smartphone applications.

Hybrid loop/monopole antenna with a passive bandstop circuit for the LTE/GPS operation in the tablet computer

ABSTRACTA hybrid loop/monopole antenna capable of covering the LTE operation in the 698–960/1710–2690 MHz band and the GPS operation at 1575 MHz for the tablet computer application is presented. With the obtained LTE/GPS operation, the antenna requires a small size of 8 × 40 × 3 mm3 only. The antenna is operated as a coupled‐fed loop antenna for the LTE operation and as a coupled‐fed monopole antenna for the GPS operation. The two antenna structures share the same radiation strip, except that the loop antenna with the end terminal thereof short‐circuited to the device ground plane of the tablet computer and the monopole antenna with the end terminal thereof open‐ended. The two antenna structures are configured into one antenna structure using a passive bandstop circuit connected between the end terminal of the antenna's radiation strip and the device ground plane. The bandstop circuit exhibits a very high impedance in the GPS band and a very low impedance in the LTE band, thereby making the antenna operated as a loop antenna for the LTE operation (698–960/1710–2690 MHz) and a monopole antenna at 1575 MHz for the GPS operation. Details of the proposed hybrid loop/monopole antenna are described. Operating principle of the antenna is addressed, and experimental results of the fabricated antenna are presented and discussed. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:630–635, 2016

Small‐size antenna for seven‐band WWAN/LTE mobile handset

ABSTRACTIn this article, a small‐size seven‐band antenna covering GSM850/900/1800/1900/UMTS2100/LTE2300/2500 bands for wireless wide area network/long term evolution mobile handset is presented. The developed antenna only occupies a planar size of 15 × 25 mm2. The capacitive coupling feed is used to generate fundamental resonant λ/8 mode and high‐order λ/4 mode to reduce the size. Electromagnetic (EM) coupling between the radiation strips is used to widen the operation band. The antenna consists of a feed strip and two radiation strips (RS1, RS2). RS2 is in the same side of the ground. RS1 is in the other side of substrate. Two λ/8 modes (at 850 and 925 MHz) and two λ/4 modes (at 1850 and 2200 MHz) are generated by the capacitive feed. Strip RS1 contributes to 850 and 1850 MHz modes, and strip RS2 contributes to 925 and 2200 MHz modes. In the mean time, there exists EM coupling between the two radiation strips (RS1, RS2), then dual‐resonance mode at 845 and 925 MHz form a wide lower band covering GSM850/900, two high order resonant modes at 1850 and 2200 MHz form a wide upper band covering GSM1800/1900/UMTS2100/LTE2300/2500. Design mechanics is analyzed and main parameters are studied. The proposed antenna is fabricated, and the simulated and measured results agree well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1029–1033, 2015

Compact coupled-fed wideband antenna for internal eight-band LTE/WWAN tablet computer applications

In this article, a compact coupled-fed antenna for eight-band LTE/WWAN tablet computer applications is proposed. The designed antenna consists of an L-shaped monopole, a long meandered strip, a long radiation strip, and a short shorted strip. The long meandered strip and long radiation strip can generate a dual-resonance characteristic for the antenna’s lower band, making it capable of a wideband operation to cover the desired LTE700/GSM850/900 (698–960 MHz) bands. Furthermore, the notch in the long radiation strip can also influence the bandwidth of the antenna’s lower band. The long radiation strip can generate an additional higher order resonant mode at the upper band, combining the two resonant modes contributed by the L-shaped monopole and the short shorted strip to form a wide upper band, covering GSM1800/1900/UMTS2100/LTE2300/2500 (1710–2690 MHz) bands. With the proposed scheme, the antenna only occupies a small volume of 60 12 4 mm3 and can mainly be disposed on a 0.8-mm thick FR4 substrate. The antenna is mounted at the top edge of the display ground which supports a 150 200 mm2 display for the tablet computer. Reasonably good radiating efficiency and antenna gain are also achieved for the practical tablet computer.

Supersonic crack growth in a solid of upturn stress–strain relation under anti-plane shear

This paper examines, from the prospect of continuum analysis, the possibility for a supersonic crack growth in a solid with an upturn stress–strain relation. The stress has a linear-upturn power-law relation with the strain, resulting in an elastic modulus, and consequently a wave speed, that increase with the strain. Though appearing to be “supersonic”, the local wave speed in the crack tip vicinity of the solid with a sufficient upturn stress–strain relation exceeds the crack extension speed. A pre-request for such a supersonic crack growth is the storage of sufficient deformation energy within the solid to nurse the energy flux drawn to the crack tip that extends at an “apparent supersonic” speed. The idea is demonstrated for the simplest case, the anti-plane shear. We examine the steady-state supersonic crack growth in a hyperelastic material. The governing equation is elliptical in the crack tip vicinity but hyperbolic elsewhere. The boundary between two regions is determined with a certain extent. An asymptotic solution is constructed within the super-hardening zone. The solution connects to the hyperbolic radiation strips by weak discontinuity boundaries and to the pre-stressed frontal field by a strong discontinuity boundary.