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To meet the demands of the new frequency bands and the $4\times 4$ multiple-input multiple-output (MIMO) specification brought by fifth generation (5G), a triple-band microstrip patch antenna and its four-antenna module are proposed. Based on the half-mode microstrip patch, the first three modes of TM1/2,0, TM1/2,1, and TM3/2,0 that can be independently tuned are engineered to cover the three Chinese 5G bands (N41/N78/N79). The proposed triple-band microstrip patch antenna with the volume of $33.5\times 32.5\times 4$ mm3 shows the −6 dB frequency bands of 2.47–2.75 GHz, 3.39–3.60 GHz, and 4.69–5.10 GHz, which makes a nice compromise between antenna volume and impedance bandwidths. Four such patches are arranged in a sequentially rotated style to constitute the triple-band four-antenna module, which is with the volume of $71\times 71\times 4$ mm3. Measured results of the module show high performance. The reflection coefficients of the four elements are almost identical: the bandwidths are 2.50–2.75 GHz, 3.41–3.62 GHz, and 4.68–5.01 GHz; all the isolations are better than −13.3 dB; the average total efficiencies of the four elements are between −1.41 and −1.11 dB, −2.45 and −2.10 dB, and −1.81 and −1.53 dB for N41, N78, and N79, respectively; and all the envelope correlation coefficients (ECCs) are lower than 0.07. [ABSTRACT FROM AUTHOR]

The huge proliferation of the antenna number brought by 5G greatly increases the pressure of the bezels of the 5G terminals. To release the pressure, planar four-antenna module with miniaturization and wideband performance that can be implemented on the back cover is proposed in this article. Four identical dual-mode PIFAs are arranged in a sequentially rotated style and the whole antenna appears in a circular shape. Each antenna element is a slotted quasi-quarter circle with one inner edge shorted and the other two edges left open, and it is coupled fed by an L-shaped microstrip line. A cross line that connects all the four elements together is used to improve the isolation of the neighboring elements. The four-antenna module covering N77 is with the diameter of 30.6 mm and height of 2 mm. The measured results show that for all the four antenna elements, the −6 dB impedance bandwidths cover 3.3–4.2 GHz, all the isolations are better than 9.7 dB, the average total efficiencies are between 36% and 40%, and envelope correlation coefficients (ECCs) are lower than 0.5. To the best of the authors’ knowledge, this is the smallest four-antenna module covering 3.3–4.2 GHz. [ABSTRACT FROM AUTHOR]

This paper proposes a polarization-orthogonal co-frequency dual antenna pair suitable for fifth-generation (5G) multiple-input multiple-output (MIMO) smartphone with metallic bezels. The proposed spatial-reuse dual antenna pair consists of a split on the metallic bezel and a slot on the mainboard ground, where the slot is centered on the split. Two orthogonal degenerate characteristic modes operating at half wavelength including in-phase current and slot modes can be excited on the same antenna structure. An end-shorted microstrip line that crosses the split is used to excite the in-phase current mode, producing $y$ -polarized radiation, while a symmetrical slot-centered Y-shaped feeding network with its shorted ends crossing the slot is adopted to excite the slot mode, producing $x$ -polarized radiation. To the best of authors’ knowledge, this is the first time that a co-frequency dual antenna pair suitable for smartphone with metallic bezels is proposed. A sub-6 GHz dual antenna pair operating at 3.5 GHz that occupies a footprint of $25 \times 7 \times 1.5$ mm3 shows a simulated isolation better than −24.1 dB without any external decoupling measures and an envelope correlation coefficient (ECC) lower than 0.008. A four-antenna MIMO array is fabricated and measured to verify the feasibility. Across the operation band, the measured isolation of the antenna pair is better than −20.1 dB and other isolation levels are all better than −12.7 dB, the ECCs of any two antennas are lower than 0.13, and the total efficiency range of the four antennas is 35.2%~64.7%. The proposed dual antenna pair exhibits a great potential to be applied in future 5G MIMO smartphone. [ABSTRACT FROM AUTHOR]

In this paper, the scanning performance at a fixed frequency of the 2-bit linear array is presented. Then, for the first time, a microstrip line that supports a traveling wave is used as bit phase sources with any bit number to construct reconfigurable fixed-frequency beam steering bit arrays. Using the \text TM1n0\,\,(n = 0.5 ) open cavity as the radiating element, a ten-element reconfigurable 2-bit fixed-frequency beam steering array operating at 5 GHz is designed and fabricated to verify the idea. By sampling two feed points with a separation distance of a quarter wavelength on one side of the microstrip line, the phase states of 0° and −90° are obtained; other two counterpart points on the other side of the line can offer the phase states of −180° and −270°, producing the required 2-bit unit. Five prototypes representing five array configurations show a measured scan range of 94° between −48° and +46° at 5 GHz, and the measured five beams show good quality and consistency: the peak gains range from 10.01 to 12.33 dBi with a gain variation of only 2.32 dB and the 3 dB beam widths vary between 13° and 17°. [ABSTRACT FROM PUBLISHER]

ABSTRACT In this article, a new strategy for high-quality and wide-coverage air-to-ground communication is proposed by using pattern synthesis method. The cosecant pattern for equal-gain coverage is synthesized using two switchable patterns, which are provided by switchable feeding networks and a ten-element airborne microstrip antenna array. The merits of the proposed strategy include two folds: first, the antenna array and feeding network are easy to design and with low cost, no need to use beam steering method. Second, the maximum available gain in the required cosecant coverage is achieved by the proposed strategy, providing sufficient path loss margin. We have simulated and fabricated the array prototype, and measured results have proved our idea to achieve equal-gain coverage with a relatively simple antenna structure. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:750-753, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT In this letter, a dual-patch antenna with bidirectional circular polarization of the same sense is proposed for coal mine and tunnel communications and positioning systems. The proposed antenna consists of two back-to-back patches with a common ground plane. We only feed one patch on the front side by microstrip feeding line, and the energy is coupled to the other patch on the back side through a slot, which is etched on the common ground. By properly truncating the corners of the dual patches, bidirectional radiation pattern is achieved with the right-hand circular polarization on both front and back sides. Compared to previous designs for the same purpose, the proposed antenna is with a compact structure using only two layers of substrate and without using complex feeding networks, benefiting from the merits of small dimension, low cost, and easy fabrication. We have built the antenna prototype and taken the measurement. The measured impedance bandwidth for S11<−10 dB is 90 MHz (2.44-2.53 GHz), and the measured 3-dB axial-ratio bandwidth is 20 MHz (2.455-2.475 GHz), agreeing well with the simulated results. The measured peak right hand circularly polarization gains are 3.70 dBic and 3.09 dBic for front and back directions. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:645-648, 2017 [ABSTRACT FROM AUTHOR]

A new antenna structure is proposed to show that a single-layer magnetic current array based on the microstrip line structure can achieve a relatively uniform and large in-phase radiating aperture together with high realized aperture usage rate (RAUR). By alternatively and periodically loading the microstrip line with blocking stubs, the equivalent magnetic currents along one direction are suppressed while the currents along the other direction are left, forming a relatively uniform and in-phase 1-D magnetic current array. The electromagnetic wave is radiated into space while traveling forward along the line. By in-parallel concatenating a series of the 1-D arrays with adjacent arrays presenting mirror relations, a large in-phase radiating aperture is built with a relatively high RAUR performance. Moreover, the shorting walls at the interconnecting planes of the neighboring 1-Darrays can be removed attributing to the antenna arrangement style and the required feed network. Eight rows of the 24-element 1-D magnetic current array fed using a substrate integrated waveguide-based eight-way power divider fabricated using a single substrate board is simulated and built to demonstrate the design strategy. The prototype shows a measured bandwidth of 4.37% and a peak gain of 25.1 dBi at 20 GHz. The RAUR is 8.66/ \lambda 0^{2} , which is higher than most of the single-layer high-gain antennas. [ABSTRACT FROM PUBLISHER]

In this communication, an all-metal standing wave antenna array is proposed based on the microstrip transmission line. By alternatively blocking the microstrip line every half wavelength, the symmetrical equivalent magnetic currents are broken for effectively radiating. By properly tuning the blocking positions along the microstrip line, a broadside pattern is achieved with high gain. The proposed antenna is scalable along one direction to a certain level to acquire the directivity as high as about 15 dBi. More importantly, the proposed antenna array has the potential to be built only by metal without any dielectrics. The all-metal structure has the merits of being low-cost, light weight, easily fabricated, and having no dielectric losses. Based on this idea, a five-segment linear array with a center feed is designed and tested. The measured bandwidth is from 7.83 to 8.81 GHz (980 MHz, 11.78%), and the measured gain is ranging from 9.1 to 12.47 dBi. [ABSTRACT FROM AUTHOR]

This letter proposes a dual-port wideband monopulse Vivaldi antenna based on a new perspective of common mode and differential mode radiations. To realize the sum and difference patterns utilizing the differential and common mode radiations, a metallic wedge is introduced in the center of the Vivaldi antenna, the effect of the virtual magnetic wall disappears, and the realistic electric wall plays the dominant role, fulfilling the boundary condition for difference beam under common mode excitation. Meanwhile, the sum beam is kept unchanged under differential mode excitation. The desired sum and difference radiation patterns are realized in a single Vivaldi antenna under differential mode and common mode excitations, respectively. Moreover, a notched band is introduced for interference suppression, and the notched frequency can be easily controlled by adjusting the microstrip feeding stub without loading an extra resonator. Measured results show that the proposed monopulse antenna exhibits 101 % fractional bandwidth from 2.2 GHz to 6.7 GHz, in which a notched band is from 3.75 GHz to 4.3 GHz. Across the operational band, the average gain of the sum pattern is 8 dBi, and the null depth of the difference pattern is below −15 dB. Measured results agree well with the simulated ones. [ABSTRACT FROM AUTHOR]